Delft University of Technology
FACULTY MECHANICAL, MARITIME AND MATERIALS ENGINEERING
Department Maritime and Transport Technology Mekelweg 2 2628 CD Delft the Netherlands Phone +31 (0)15-2782889 Fax +31 (0)15-2781397 www.mtt.tudelft.nl
This report consists of 68 pages and 1 appendices. It may only be reproduced literally and as a whole. For commercial purposes only with written authorization of Delft University of Technology. Requests for consult are only taken into consideration under the condition that the applicant denies all legal rights on liabilities concerning the contents of the advice.
Specialization: Transport Engineering and Logistics
Report number: 2015.TEL.7978
Title:
State of the art survey of baggage
handling systems control and
automated equipment
Author:
L.L.P. van Rijen (4036670)
Title (in Dutch) Voortgang en huidige stand van techniek in de automatiserings en besturingstechnologien voor baggagesystemen.
Assignment: literature Confidential: no
Initiator (university): dr.ir. Y. Pang Supervisor: dr.ir. Y. Pang
T
U
Delft
FACULTY OF MECHANICAL, MARITIME ANDmKammy]
t.;liVi.-,i:i(W::^|r!lüïK|i,ViDepartment of Marine and Transport Teclinology Delft University of Technology
Mekelweg 2 2628 CD Delft the Netherlands Phone +31 (0)15-2782889 Fax +31 (0)15-2781397 www.mtt.tudelft.nl Student: Supervisor: Specialization: L. L. P. van Rijen Y. Pang TEL
Assignment type: Literature Report number: 2015.TEL.7978 Confidential: No
Creditpoints (EC): 10
Subject: State of the art of automation and system control in baggage handling
Modern airport baggage handling concerns improving the processes from check-in through screening until departure, arrival and claims. Various automated baggage handling technologies are worldwide applied from sortation, transport, tracing and tracking, storage and retrieval. Together with integrated system control smooth handling processes and operations can be achieved with respect to handling speed, safety and efficiency.
This literature assignment is to survey the state of the art of automated equipment and technologies applied in the field of airport baggage handling. Further, the principles and approaches of integrated baggage handling system control will be investigated. The survey of this assignment should cover the following:
- to review the general airport baggage handling process including the description of sub-processes and involved equipment;
- to summarize the functions and operations that can be automated;
- to investigate the technologies to achieve automation and to describe relative applications; - to survey the existing and feasible concepts, methods and principles for the control of
baggage handling systems.
This report should be arranged in such a way that all data is structurally presented in graphs, tables, and lists with belonging descriptions and explanations in text.
The report should comply with the guidelines of the section. Details can be found on the website. The mentor.
i
Preface
This work has been made to fulfill a literature assignment from the department Transport Engineering and Logistics concerning baggage handling systems. It adds knowledge over the developments and state of the art of baggage handling systems, airports in particular. Baggage handling systems, being challenging transport infrastructures, are from a mechanical and control point of view very relevant and interesting to the department and myself. This work has been written in such a way that it can be understood by people with an academic background in this particular field.
Summary
The ongoing trend of worldwide air passenger growth and the corresponding growth of major airports hubs caused more and more throughput in these major airports hubs. As a consequence the baggage handling systems (BHS) grew simultaneously larger and more complex. At the same time, like many other industrial sectors automation experienced a vast increase. This report aims to survey the state of the art automated baggage handling equipment in which commercialized equipment is reviewed as well as radical new concepts which might give a glance into the future of automation in BHS. The increasing complexity and new challenges within large modern BHS impact the control of these particular systems as well. The mostly academic research into this specific field of control will hence be analysed as well. In this way, a complete review of BHS is realized, from the point a passenger deposits its bag up to the point the bag is placed inside the aircraft and back up to where the passenger picks up its bag again.
The BHS can be divided in different parts, each with their unique equipment. The first concerns baggage drop-off and reclaim, the only parts coming into contact with the passenger. Automated baggage drop-off, one of the most recent additions to the automated equipment, is special since it is the only part which has interaction with the passenger. Screening follows after drop-off. The most modern screening equipment has high throughput and advanced 3D scanning techniques. In this way one pre-scanning step can be omitted, resulting in less rejections. Subsequently inner terminal transport and sorting is realised. The focus of new equipment is on speed and throughput. Destination coded vehicle systems are more and more common with the increased demand for higher velocities in continuously expanding airports. Many sorting options exist although they often have their own infrastructure which makes the choice also very dependents on the existing transport infrastructure. Early baggage systems are present in larger hub airports and exist in different forms. The make-up area including inbound unloading (when baggage has been brought back to the terminal) has seen a significant amount of new automated equipment being installed. From robotics to baggage
aligning/orienting equipment. Automated carts and unit load device (ULD) unloaders have also been commercialized. The last part of the journey of the bag (from an outbound perspective) reaches up to the belly of the plane. Automation is much more scarcely present compared to the other parts of the BHS since a significant part is mechanised and/or realised with human involvement. New ideas however have emerged through patens which aim to realize more automation. The control chapter starts with an introduction to low and high level control and equipment for control. The following section about control challenges in BHS seeks to find the difficulties and opportunities in terms of
ii control. The state of the art high level control is discussed afterwards followed by an overview of research in the field of control of BHS. The main topics discussed are model predictive control (MPC) and multi agent systems (MAS).
Due to the significant amount of research related to control of BHS, especially if control of material handling systems in general is included, the focus has been towards high level control and to largest topics MPC and MAS in particular. These topics covered to a large extent most of the research from recent years. Research in these topics specifically dedicated to BHS started between 2005 and 2010. MPC in a hierarchical control structure shows the most promise together with centralized MPC with a pre-calculated initial best guess to speed up computation time. For both fields of research remains still many research left to do before it can be introduced in real BHS.
Automation seems to be expanding throughout the whole BHS. The most modern additions include the automated drop-off solutions and automated loading and unloading equipment for carts and ULD. For the remaining parts which rely still heavily on human involvement it can be argued that they will be automated as well. The technological progression and the trend of continuous automation up till today support this statement.
List of abbreviations
ABD: Automated baggage drop-off AMS: Amsterdam Airport Schiphol BHS: Baggage handling system(s) BPH: Bags per hour
CTM: Container transfer module(s) DCV: Destination coded vehicle(s) EBS: Early bag storage(s)
EDS: Explosive detection system(s) HBS: Hold baggage screening
ICAO: International civil aviation organization ICS: Individual carrier system(s)
IED: Improvised explosive device(s) MAS: Multi agent system(s)
MPC: Model predictive control PEC: Photo electric cell
RFID: Radio frequency identification SOA: State of the art
iii
Contents
Preface ... i Summary ... i List of abbreviations ... ii 1. Introduction ... 12. The baggage handling process ... 3
3. Baggage handling equipment ... 4
3.1 Baggage drop-off and reclaim ... 4
3.2 Baggage screening ... 10
3.3 Internal transport ... 15
3.4 Early baggage storage ... 27
3.5 Make-up area ... 30
3.6 External transport and loading of the airplane ... 38
4. Control of baggage handling systems ... 42
4.1 An introduction to PLC’s ... 42
4.2 The challenges of control of baggage handling systems ... 43
4.3 Control architectures ... 45
4.4 The traditional state of the art method ... 46
4.5 Multi agent systems ... 47
4.6 Model predictive control ... 50
5. Conclusions ... 58
6. Bibliography ... 60
1
1. Introduction
Air travel growth has been very strong in the past decades [1] and not surprisingly, airports grew simultaneously. This increase of demand had a large influence on airport operations and baggage handling systems (BHS) in particular which grew larger and more complex. Automation and mechanization became a more and more present phenomena. Nowadays automation and mechanization is still expanding throughout the BHS and continuously improved, slowly replacing or supporting human labor and improving the system performance. Many large modern airports have replaced their conveyor belts partly by faster individual carrier systems (ICS) and recently the concept of automated baggage drop-off (ABD) has been introduced. The most recent and significant innovations in BHS have been mainly where there was still few automation. This is at the Baggage drop-off, at the early baggage storage (EBS), at the make-up section and at the airplane. However this does not mean all innovations are fully automated equipment. There has also been a lot of interest in innovations in human support equipment, to help the handlers support the weight of the baggage.
Different reasons can be attributed to the rise of automation and mechanization. Firstly, machines are able to lift heavy without the long term problems encountered by people, like (lower) back problems. IATA (International Air Transport Association) has tried to solve this partly by limiting the allowed baggage weights but the current standard maximum of 23 kg [2] is nonetheless still heavy enough to cause lower bag problems on the long run [3]. Mechanization plays a crucial role to limit this problem. Automation is an extent of mechanization and adds more benefits. More automation means that baggage has less chance to get lost or stolen since employees have less chance to interfere in the baggage handling process and baggage is more consequently traced and tracked since this is inherently required to transport the bag by automated means. It also decreases the chance that maleficent employees can place anything inside the baggage such as explosives. The rest of the arguments apply to automation in general such as the arguments that robots never complain, never get sick, offer a very continuous output over the whole day and they are perfectly suited for repetitive jobs which are required in abundance in large BHS. In countries where minimal wages are high, automation can also lead to cost savings in the long run.
This research aims to get an overview of the present BHS technologies which are offered by the industry and by proceedings in the academic field. It aims to evaluate the state of the art of the complete BHS from baggage drop-off up to the baggage hold of the airplane and back up to the baggage reclaim area. It focuses on commercialized equipment and innovations as well as new control technologies and methods of the complete system. Research which focuses on controlling specific parts can be added if the amount of research allows. It should be noted that baggage handling does not merely applies to airports. But since the airport industry is by far the biggest user of these systems and also by far the most state of the art industry with respect to BHS, the focus will be entirely on airports. Nevertheless, it should be noted that equipment and control technologies could also be used in other industries, both transport related branches and other industries like product manufacturing and postal services.
2 The time span which the review of BHS system control will have is depending significantly on the research itself found by the author. The goal is to investigate the research from 5 years old but if it seems obvious to take somewhat older research into consideration, it is reasonable to take that research into account. Concerning the automated equipment, patents have mostly been used for those parts of the BHS which have still no automated commercialized equipment. Other use of patents is clarification of working principles of state of the art equipment or promising competitive concepts. The main sources of this survey will be relevant academic papers, mostly for control technologies, patents and company information, in particular for equipment innovation, and finally interviews with experts if deemed necessary. The research is deemed complete if the complete BHS, the entire journey of the bag, has been surveyed and if all important novelties in the field of control of BHS have been addressed.
The report starts with a brief schematic overview of the BHS. It is shown here how all these processes are interrelated. It will continue with the main topic of this survey, commercialized equipment and innovations, where it will elaborate on the different parts or processes of the BHS in the consecutive sections. Since all these parts are not generally distinguishable they are defined by the author. The reason why certain processes and equipment are grouped together is due to similarities, their place inside the BHS and/or the size of the content regarding certain processes. The chapter will start with a section about Baggage drop-off and reclaim followed by baggage screening. The next section about internal transport includes sorting equipment, but does not include any form of transport between the make-up area and up to the airplane. This distinction is made because this transport differs significantly from the regular BHS. To highlight this distinction this section is called internal transport. The chapter continuous with a section concerning EBS followed by a section with all equipment related to the make-up area. This includes inbound baggage feed into the baggage conveyor system inside the terminal. Alignment and orientation equipment which is predominantly used at this inbound feed is for that reason also discussed here. The chapter will conclude with a section about the complete final journey of the bag up to the aircraft hold.
Subsequently the report will give an overview of the proceedings in the field of control technologies where the challenge of control of BHS will be discussed, the current state of the art control method and finally the novelties from academic research. Finally, the report will end with a conclusion where it will present the findings of the survey.
3
2. The baggage handling process
The baggage handling system needs to accomplish three different goals which are scanning, tracking and routing. Scanning, i.e. screening, is performed by screening equipment [4]. Tracking is
accomplished by the use of sensors and the ability to store data and show data to the operators. Routing refers to the physical movement of individual bags between the passenger and the aircraft. The largest part of this study involves equipment aiming to achieve the goal of routing (1) but attention is also given to sensors which are necessary for the working of this equipment.
Figure 1 shows the complete baggage handling process in a typical modern large airport hub [5], showing all processes form the highest level. Left of the dotted line is public space, right of the dotted line is secured space not accesible by non-authorized people. Security, meaning minimization of chance of potentially hazardeous human interference with the baggage such as the placement of explosives, is especially important after inbound screening. Each block represents a separate subsystem of the BHS. The blue blocks represent outbound flow and the red blocks inbound. With ‘Transport over tarmac’ and ‘Transport into/out of the airplane’ there is no difference between outbound and inbound except the direction of the flow.
Figure 1 The overall baggage handling process in a typical modern large airport [5].
The blocks represent different processes. Sorting is not represented in this figure as a separate process but it belongs to transport in this case as mentioned before. The difference between small and large airports is the flow of transferbaggage. In small airports the only option is to retrieve your baggage as a passenger and re-enter it at the baggage drop-off. The storage facility, called the early bag storage (EBS) is also non-existent since baggage is usually just stored at the make-up. Sometimes baggage is manually put aside if necessary. Another difference is the size of the BHS. This has an impact of the infrastructure of the BHS. Large BHS may have a loop where different parts of the BHS can connect to. In this way different terminals can connect with different EBS and gates without the need for a direct connection between all of them. Amsterdam Schiphol (AMS) for instance calls it the backbone since it is the main transport line [6]. Another typical feature of large airports are the long distances. Large distances demand high velocities to be able to to achieve short connection times and short drop-off to airplane times. These high velocities are only achieved by state of the art equipment.
Internal Transport (within terminal building) Baggage
drop-off Screening
Storage (EBS)
Make-up Transport over tarmac Transport into the airplane
Transport out of the airplane Transport over
tarmac Baggage feed
into the internal transport system Reclaim (optional)Screening
4
3. Baggage handling equipment
This chapter will show a state of the art equipment overview where it tries to give a comparison between current applied and commercially available automated technologies. Each section will start with a brief introduction of the subject followed by a functional diagram of the (sub) system under observation to provide the insight in the functions linked to the processes which are to be automated. The main focus will be on the operation of the relevant equipment. Moreover, the (dis)advantages of the relevant equipment and a comparison between them will be listed if applicable. Finally, if necessary, representative specification will be given by figures delivered by equipment manufacturers. Most sections will start with a clear definition to clarify, or in the case a good or appropriate one could not be found with a description by the author.
It is important to distinguish two different terms, automation and mechanisation. Automation can be defined as: ‘the technique, method, or system of operating or controlling a process by highly automatic means, as by electronic devices, reducing human intervention to a minimum’ [7] whereas mechanisation merely means ‘to operate or perform by or as if by machinery’ [8]. From the first definition it can be deduced that human involvement is not necessarily completely omitted. Especially on the tarmac some equipment is deployed by humans but once in place it has the ability to work (partly) autonomous with the aid of sensors. If any confusion on whether it would be automated or not might arise, the equipment is still surveyed. Nowadays most of the modern equipment in BHS is automated. Some mechanisation is still present however in even the most state of the art airports. The focus however remains solely on automation.
3.1 Baggage drop-off and reclaim
Figure 2 Automated Baggage drop-off at Amsterdam Airport Schiphol (AMS) [9].
This section is divided in two parts. The first part will concern automated baggage drop-off systems, such as illustrated in figure 2. The second part, which is considerably smaller, will elaborate on reclaim systems.
Automated baggage drop-off systems
Description by author: Baggage drop-off refers to the drop-off process for excess baggage which is not allowed to be taken into the passenger compartment of the aircraft. It is one of the entering points of the BHS for baggage and the only one accessible to passengers.
5 The system is designed to interact with humans, which makes it a special part of the BHS and only partly automated. The parts which are automated are the instructions to the passenger, the check if the label is placed correctly and the check that the baggage has authorised weight, dimensions and conveyability (round objects for instance are not conveyable). It also makes sure that there are no humans or animals introduced into the baggage handling system.
The first patents related to Common Use Self-Service (CUSS) were filed in the late 1980’s [10]. After ten years, in the 1990’s, a patent was released for an automated bag drop-off (ABD) [11]. However, it is only recently, in the past decade that these innovations actually became reality. First automated check-ins, later ABD were deployed in the past five years. Since the successful entrance of low cost carriers into the air transport market, the industry realised that the best possible service was not a must for most passengers. The increase of competition (low cost carriers and Middle East carriers) also forced the airlines to cut down costs in all possible ways to be able to compete. It started with the self-printing of the boarding card and after this was completely accepted by the passengers it was time to start with automating the baggage drop-off process. Common Use Self-Service (CUSS) technologies became a more frequent presence at airports. A typical ABD process, as present at AMS and commercialized by BagDrop, will look as shown in Figure 3.
Figure 3 A typical ABD process as present at AMS, provided by BagDrop [12] [13].
The return loop is for additional pieces baggage a passenger may have. The warning is released after it fails one of the checks. When observing other ABD systems, some differences might occur. In Paris Charles de Gaulle for instance, the baggage label should be printed in advance at another CUSS system [14].
The functional diagram for an ABD system is depicted in figure 4. The red dots with numbers will be used on the next page to identify the sensors and devices required to fulfil a certain function.
Figure 4 Functional diagram ABD system.
Checking passenger information (boarding card or biometric scan for
example)
Check baggage, this includes: IATA bar code reading
Intrusion detection Oversize detection conveyability check
(Lugagge imaging) (RFID tag writing and
reading) Print baggage label Baggage weighing
(Tilt bag and) transport bag onto the next
conveyor Close door Open door (i.a.) Open door Give warning red = optional Print baggage claim tag
Accept and feed passenger bag (s) into the BHS
Make sure nobody enters BHS Check dimensions Transport bag Check passenger Check boarding card Scan barcode Link bag to passenger Print bag label
with barcode
Close door (optional) Check for living animals/people Check weight Check bag Code RFID Check label if placed correctly Check conveyability
1
2
3
3
6
4
8
Provide protective housing (optional) Stick RFID to label5
Take picture of bag (optional)7
9
3
Detect presence bag Transport bag10
6 This equipment in particular contains a great amount of specific sensors and other devices. The complete list, based on the red dots in figure 4, is as follows:
1. Barcode scanner to check the barcode [15];
2. Weight sensors for weight allowance, load cells for instance [13];
3. Measuring automation light can be used oversize detection and ‘conveyability check’ [15]. Oversize detection is also possible with Photoelectric cells [16].
4. Label printer [18];
5. Device which connects (sticks) the RFID tag to the label [18]; 6. RFID reader for reading and writing RFID tags [15];
7. Camera for luggage imaging if applicable [18]. This image could be used later in the handling or in case the bag would get lost it would provide useful extra information;
8. Safety light curtains ‘
to prevent the risk of jamming or an accident when closing’[17];
9. 2D laser scanners can be used for intrusion detection [18] as well as infrared cameras, carbon dioxide detectors or movement detectors [19] They cannot detect however the presence of humans or animals within a suitcase. Load cell fluctuations can therefore be used to solve this problem [13].
10. 2D lasers for detecting baggage on receiving conveyor for conveyance to the BHS. This is necessary since ABD usually contain two conveyors if multiple baggage input is desired which is often the case [15].
Differences between ABD systems
Based on a research on ABD concepts and commercialized products it is observed that they can be distinguished by several key features. This is visualized in figure 5. The explanation on the differences follows after the figure.
Figure 5 Categorization of ABD systems.
The most interesting feature in which baggage drop-off technologies distinguish themselves is in the way the baggage is brought into the BHS. The baggage can be delivered to the BHS in a horizontal or vertical direction. A vertical baggage drop-off concept, called DROP@EASE [20], shown in figure 6, came from Vanderlande Industries, which proposed this solution in combination with their TUBTRAX system. In this concept the advantage comes mostly from the immediate ‘tubbing’. This brings a great amount of different advantages: ‘By bringing the carrier to the passenger, there is no more need for check-in belts, tipping devices, barcode scanners, automatic loaders and manual coding stations further downstream’ [20]. This drop off solution is also beneficial for the available floor space on passenger level. In contrast, it is much more space demanding on the lower level. This requires the drop-off
ABD system
Front access Horizontal Insertion of
baggage into BHS Vertical Insertion of
baggage into BHS Side access
Tilting system No tilting
system Closed
7 stations to be spaced at a significant distance from each other. Another downside is that each drop-off point requires a lift which significantly adds to the complete costs of the system.
Figure 6 DROP@EASE ABD solution from Vanderlande [20].
Other features in which ABD systems distinguish themselves are the placement of the passenger access, some of them can be accessed from the side of the conveyor (Figure 6, number 1), others from the front (Figure 6, number 2). An example of the first is the ABD from Alstef [14] and an example of the second is shown in figure 2, offered by SARABEE/Bagdrop [21].
Figure 6 Front and side access of ABD systems.
Some ABD points are closed, others are open. ‘Important drawbacks of closed baggage drop systems is that they require substantial alterations to the existing infrastructure present at airports and hence are relatively expensive. Furthermore, closed baggage drop systems are of higher complexity than the open-natured systems and the associated purchase cost is therefore higher’ [13].
Closed ABD systems can have a tilting system. Such a system was proposed in a patent from SCARABEE [19]. One advantage is that the baggage can be placed in such a way that that its centre of gravity is as low as possible towards the running conveyor which creates more stability. Moreover, it also serves as an obstruction towards the conveyor system behind it. This prevents someone or something to enter the BHS. It removes the necessity for an extra blocking mechanism. The system has two conveyors which can rotate over 90 degrees with their centre of rotation in the direction perpendicular to the direction of conveying. This is shown in Figure 7 where 18A shows the inside of this particular ABD system where 40 and 42 are both tilting conveyors and 46 shows the closing lid at passenger side. The infeed is left and the exit towards the BHS is right where 44 can serve as a buffer
8 and might even work as a lift element to bring the baggage underneath the floor towards the underlying BHS.
Figure 7 Conveyor configurations and process for a closed ABD system with tilting system [19].
Another tilting system has been patented by the Airport of Paris [22]. This system uses only one conveyor and a tilting kinematic to tilt the baggage. This process is shown in figure 8. According to the inventors their system has a shorter processing time than the previous one.
Figure 8 Tilting configuration and process for a closed ABD system [22]. Baggage reclaim
Description by author: The inbound version of drop-off, called baggage (re)claim, is the process where the passenger and the bag get reunited.
The first automated reclaim systems where already invented in the sixties [23] and were improved in the subsequent decade to something we can observe more or less today. The current system is a conveying system which enables bags to be moved around a predefined path using overlapping plates all along the path which support the bags. Two types exist, flat and tilted systems: ‘The tilted … (version)…adds additional storage capacity to the carousel, while the flat version offers improved ergonomic handling for passengers’ [24].
The operation is fairly simple. An important operational consideration however is at the infeed: ‘To avoid overloading the baggage claim carousel and damaging luggage as a result, the luggage feed process to the baggage claim carousel is monitored. A … photoelectric proximity sensor detects the load status of the baggage claim carousel right before the induction belt. the luggage supply from the induction belt stops if the baggage claim carousel is occupied by luggage at that point and the … photoelectric sensor simultaneously detects another piece of luggage on the induction belt’ [25].
The advantage of the current reclaim system is that it is automated and and as said before, fairly simple. There are drawbacks however. One inventor describes these drawbacks as follows: ‘Travelers crowd around the carousel, potentially making it difficult for others to get to their bags, because they are unsure of when their bags will appear. Travelers may accidentally grab similar looking bags which are
9 not theirs. Such as system may lead to anxiety in travelers as they try to find their bags while hoping that their bags are not lost’ [26].
Inventions tried to reduce or eliminate this problem with different solutions. The inventions which stay within the scope of the research are listed here1:
- Current existing equipment but in addition notify the passenger about the arrival of their bag (their bag in specific). This can be done with a personal indentifaction code automatically shown on a public screen or with a message automatically send to a passengers personal mobile communcation device [26]. This solution reduces the problem, although it remains possible to take the wrong bag. An advantage of this solution is that it requires limited modifactions to the current system which makes it cheap. Bag identification sensors would be required to be able to notify the passenger.
- Block baggage unless passenger indentity is confirmed. Baggage is placed inside a locking mechanism which releases the bag when the passenger indentifies himself [27]. This eliminates the problem completely but has major drawbacks regarding costs and the fixed baggage spots make this concept more space demanding.
That there is potential for improvement regarding the reclaim process is emphasized by Rein Scholing, a logistic expert from Tebodin Consultants & Engineers: ‘Taking the passengers’ perspective, baggage reclaim is clearly an underdeveloped area – would it not be logical to upgrade this function to the quality level of the check-in process? ….The answer to all these questions is ‘yes’. There is ample potential for improvements and time and cost savings. However, this requires true willingness of parties to cooperate and rethink the baggage handling process together to develop into a system which can cope with ever-growing baggage flows’ [28].
1 One other invention which aims to solve the problem, not mentioned in the text because it remains outside of the scope of this survey is the following: Check passenger + bag combination when leaving the reclaim area [151]. A viable option. It reduces any unintentional mistaken baggage. Since labels can be switched baggage weight can be checked to minimize the chance of stolen baggage. The downside of this system is that passengers are delayed when leaving the area.
10
3.2 Baggage screening
Figure 9 Baggage screening equipment, three Morpho CTX 9800 DSi [29].
Definition by the international civil aviation organization (ICAO): "The application of technical or other means which are intended to detect weapons, explosives or other dangerous devices which may be used to commit an act of unlawful interference" [30].
The process of screening checked in baggage which takes place inside BHS is referred to as hold baggage hold screening (HBS) and sometimes checked baggage screening (CBS). The process of HBS was almost non-existent until the attack on a Pan Am airplane above Scottish Lockerbie in 1988. After this devastating event, BHS was internationally stimulated [31]. A second important event in the history of hold baggage screening was not surprisingly the 9/11 terrorist attacks. ‘Before September 11, 2001 only 5 percent of bags were being checked’ was mentioned by the United States Transportation Security Administration [32]. At the end of 2002/start of 2003 all baggage was screened in the US and Europe [33].
The most common screening procedure consists of five levels, if a bag does not pass a certain level it will go to the next level, except level 5 which can be reached from all levels excluding level 1. Level 1 to 3 are still part of the BHS, although level 3 is a diverted route. 4 and 5 are separate and require manual handling of the baggage [30].
A more elaborate description of each level comes from ICAO [30]:
- ‘Level 1 screening is carried out by high-speed X-ray machines with automatic explosive detection capabilities.’
- Level 2: ‘This level consists of a group of workstations each equipped with image enhancement /manipulation to allow diagnosis of the screened image by the operator. An operator decides whether the bag is cleared or not at this level.’ If the decision can not be made within a predefined time window the bag will be sent to level 3.
- ‘’All bags that are either uncleared by the Level 2 operator or are subject to errors in the tracking system are diverted to Level 3. Level 3 screening equipment typically consists of certified EDS CT units.’
- Level 4: ‘This level is for bags not cleared at Level 3 and normally requires the bag and passenger to be reunited for a hand search of the contents.’
11 - ‘Level 5 bags are those which may be classified as suspect by the security screening staff at
any point from Level 2 onwards. The appropriate authorities (police) and the airport
management are notified by the security operator whenever uncleared baggage is referred to Level 5 and agreed emergency procedures are instigated, usually consisting of referral to the specialist EOD (bomb squad) teams.’
Level 4 and 5 are indeed not part of the BHS and are not using automated equipment. Therefore the technologies presented in this report will apply only to level 1 to 3.
The functional diagram of HBS is relatively simple, it is depicted in figure 10.
Figure 10 The functional diagram of HBS.
There are many technologies, most of them are used as imaging technology which means they provide an image which can be displayed on a screen. Zbigniew Bielecki, et al. mentions two types of explosives detection systems (EDS): ‘IED (improvised explosive device(s)) detection techniques can be divided into two groups: bulk detection of explosives, and trace detection of explosives. In bulk detection, a macroscopic mass of explosive material is detected directly, usually by viewing images made by X-ray scanners or similar equipment. In trace detection, the explosive is detected by chemical identification of microscopic residues of the explosive compound. These residues can be applied in either or both of two forms: vapor and particulate’ [34]. The focus will be on bulk detection systems, since these include equipment which can be placed inside a BHS. Trace methods are used in level 4 and 5 and involve manual, laboratory type of screening. It is therefore not automated.
Different technologies
For screening different technologies can be used as shown below. All information has been retrieved from [35] unless given otherwise. Only the currently commercialized bulk screening methods are mentioned here.2 In this section only the technology behind each method is explained. A more in dept comparison between the methods follows later.
- 2D imaging: X-ray Transmission Imaging (for level 1), also called projection radiography. ‘The oldest and simplest form of x-ray scanning. In projection radiography, a beam of x rays is directed at an object behind which a detector or x-ray sensitive surface (i.e., electronic-device array or photographic film) is placed. Volumes of different absorptive properties in the object
12 absorb and scatter the incident x rays to different degrees, causing an x ray shadow to be cast on the detecting surface. This shadow pattern is the x-ray image.’
- 2D imaging: X-ray Backscatter Imaging. ‘“Backscatter” consists of waves that are reflected back from an obstacle. In backscatter imaging, x rays are beamed at a target object and a sensor co-located with the beam source records reflected (backscattered) waves.’
- 2.5D imaging: Stereoscopic X-ray (for level 1), 3D impression from Transmission X-ray information;
- Full 3D imaging: Computed Tomography (CT) X-ray. With this method ’a hollow tube that surrounds the bag. The X-ray mechanism revolves slowly around it, bombarding it with X-rays and recording the resulting data. The CT scanner uses all of this data to create a very detailed tomogram (slice) of the bag.’ It is a complex, time-consuming and expensive technology and therefore mostly used at level 3) [36] [37];
- Full 3D imaging: Real Time Tomography (RTT) X-ray. CT uses a rotating gantry whereas RTT uses a stationary gantry with a ring of x-ray sources and sensors [38]. This is visualised in figure 11.
-
Figure 11 Working principle of CT X-ray and RTT X-ray technology (2).
- Full 3D imaging: Dual energy RTT and CT X-ray (3). As the name suggests, dual energy technology uses two different energy levels to create images [40].
- Non-image: X-ray diffraction technology or coherent X-ray scattering (CXRS) compares scanning patterns with a library of materials [41].
All these methods can be categorized and this is visualized as such in figure 12.
Figure 12 Categorization of currently applied screening technologies.
Currently applied screening technologies
2D imaging 2.5D imaging Non image
technology Full 3D imaging X-ray Transmission Imaging X-ray Backscatter Imaging Stereoscopic
X-ray Imaging Computed Tomography (CT) X-ray
Dual Energy RTT and CT X-ray Real Time Tomography
(RTT) X-ray
X-ray diffraction technology
13 As for the 2D techniques, the most commonly applied technique for baggage screening is transmission X-ray. In contrast to backscatter it is a certainty that all concealed objects are more or less visible and the image is sharper (objects have sharper definitions) than that of backscatter [42]. However, in certain cases, transmission X-ray can result in such high complexity images that can barely be readably or some details vanish in the total complexity of the image. In such cases, backscatter might give more valuable information [43]. Moreover, backscatter shows better results with organic and plastic materials. This is clearly visible in figure 13 where a plastic pistol on the right is clearly more visible with backscatter imaging. Both technologies are complementary and are therefore preferably combined.
Figure 13 Transmission (a) and Backscatter (b) comparison [44].
Since full 3D imaging has been too expensive and to slow in the past to use at level one, conventional 2D X-ray has usually been used at that particular level. The results of this conventional X-ray however are less clear and will therefore result in more declined baggage, baggage which has eventually to pass through level 3 equipment which increases the processing time of the bag. Nowadays more advanced full 3D imaging systems called RTT X-ray are able to reach higher throughputs, equal to 2D X-ray at lower prices compared to conventional CT X-ray which make them a viable option for level 1 and level 2 screening. The main difference between CT and RTT is the gantry as mentioned before which allows higher throughput but it is also less costly regarding operational costs and service costs due to a smaller amount of moving parts [37] [45].
Dual energy technology which can be applied to both conventional CT as to RTT offers to possibility to retrieve both atomic number information and density information, instead of only density information. Both measurements can be used to improve the knowledge regarding the materials inside a bag. In addition, Ying, et al. mentioned the following: ‘For example, water and the explosive ANFO (Ammonium Nitrate and fuel oil) can have similar physical densities. However, they differ significantly in effective atomic numbers. Therefore, water and ANFO can be better discriminated from each other by a dual energy CT scanner. It has also been shown on non-CT-based x-ray systems that using both atomic number and density measurements for explosive detection can achieve a lower false alarm rate than using density measurements alone’ [39].
X-ray diffraction is a different method which is used in combination with CT or RTT equipment to decrease false alarm rates. It identifies material based on its material composition by comparing x-ray scatter spectra with those of substance samples from a library [46].
Both X-ray diffraction and backscatter are used only in addition to one of the other methods to decrease false alarm rates. In itself they are not sufficient.
14 Table 1 shows a small overview of current state of the art commercialized in line screening systems. This table is based on the following references: [47] [48] [49] [50] [51]. This table should give an idea about the performance of individual techniques.
Table 1 State of the art commercialized in line screening systems.
Model (Manufacturer) Technique Throughput* [BPH**] Belt speed [m/s] Views (if 2D) Rapiscan MVXR5000 (Rapiscan systems) Conventional X-ray 1800 5 Rapiscan RTTTM 80 and 110 (Rapiscan systems) Dual Energy RTT X-ray 1200 - 1800 3D eXaminer 3X (L3) CT 300-360 3D eXaminer 3DX (L3) CT 550 3D eXaminer 3DX-ES (L3) CT 440-750 3D
eXaminer XLB (L3) Dual Energy CT ≤1200 3D
MV3D (L3) Dual Energy RTT X-ray ≤1800 3D HI-SCAN 10080 EDX-2is/EDtS (Smiths detection) RTT X-ray 1800 0,5 3D
Reveal CT-80DR+ (Leidos) Dual energy CT 226 3D
Reveal CT-800MS (Leidos) Dual energy CT 660-1000 3D
Reveal CT-120 (Leidos) Dual energy CT 1000 3D
XRD3500 (SAFRAN Morpho)
X-ray diffraction - 0,5 – 1,2 n/a
CTX5800 (SAFRAN Morpho)
CT Over 400 0,14 3D
*In case two numbers are listed (nr-nr) the lowest usually refers to stand alone configuration, otherwise it refers to the in-line configuration.
** BPH = bags per hour
This table shows that the machines equipped with the RTT technique are considerably faster than regular CT and matches the throughput of conventional X-ray.
15
3.3 Internal transport
Figure 14 The BEUMER autover®, an independent carrier system (ICS) [52].
Description by author: Transport refers to the general displacement of baggage which is required all over the BHS. This displacement is necessary to get a bag from its initial drop-off point to its final destination. More elaborately, displacement can mean horizontal displacement, vertical displacement or diverting.
Nowadays there is a large variety in transport equipment. Horizontal transport is the most prevalent process in BHS, since it is required to cover the distances inside a BHS. Vertical transport can be used throughout the BHS. Vertical distances can be covered using regular horizontal transportation equipment when the equipment is place under an inclined direction. However, for confined spaces or if limitation of space is desired dedicated equipment can be used to perform vertical transport. Baggage diversion is required for both redundancy and sortation purposes and this process may take place throughout the BHS. The basic functional diagram of baggage transport is shown in figure 15.
Figure 15 The functional diagram of baggage transport.
This section will start with a discussion about the main transport systems currently in practice, including a thorough comparison. Afterwards this sections elaborates on how these systems process bags and which sensors and communication technologies are used in order to do so. This sections ends with vertical transport and sortation which are processes which require special attention due to the dedicated equipment used for these processes.
Transport baggage
Divert baggage Transport baggage horizontally/vertically
Divert baggage horizontally/vertically Move baggage
Track location baggage Retrieve information path/destination bag(streams)
Check if bag has reached divertion point Know current position divertion equipment
16 Different transport systems
In BHS two main transport concepts currently exist: conventional systems (conveyors) and advanced systems like ICS which uses destination coded vehicles (DCV). Both have their own equipment and technologies. ICS is improving on one important requirement for new and future BHS which is throughput [53]. Throughput is important to ensure minimum connection times (MCT) in large hub airports and inbound travel time of baggage which is important regarding customer satisfaction. The speed (which influences throughput) of ICS can be considerably higher as will be shown in a
comparison with a conventional BHS. There are currently two types of ICS currently on the market, as shown in figure 15.
Figure 15 Vanderlande Tubtrax, Tub type ICS (L) and Daifuku Logan iDCV, vehicle type ICS (R). The first system uses tubs (also named ‘totes’, ‘trays’ or ‘containers’) and the second type uses vehicles, possibly in combination with a tub placed on the vehicle (more about this later in the report). The ‘just tub’ version uses belts or rotating frictional wheels on the track to convey the tub. The vehicle version uses self-propelled vehicles which are running over a track. One difference between the two types is that tubs are passive and vehicles are not. With active vehicles moving elements on the track become obsolete, except perhaps for switching tracks. The BEUMER autover® is an example of a system where the track lacks any moving parts. Baggage can be offloaded by the vehicle itself using an integrated conveyor belt and switching tracks is performed by lowering a pivot arm with a guidance wheel over an edge which forces the vehicle to follow the edge towards a certain track. This is shown in figure 16. This brings an important advantage: incidental break downs of moving parts have less impact on the BHS operation since operations can continue while the carrier goes to the repair area. In practice this means the following: ‘… if there is a failure in the drive system of an individual carrier, the vehicle is automatically collected by the immediately following unit and continuous its journey without interruption. This means that there is no need for additional transport lines to achieve the desired level of redundancy’ [54]. A track segment in contrast would require a temporary shutdown of the complete route to repair it or replace it by a new segment. A downside however of all this integrated functions inside each vehicle is the increased weight of each vehicle.
Figure 16 Rear view of a BEUMER autover® vehicle with track guidance [55].
Lowered
pivot arm
Guidance
wheel
Guiding
edge
Lifted
pivot arm
17 The second difference is the mode of control. A tub will have no on-board intelligence which means the track routes the tub whereas a vehicle in contrast does has an embedded controller. An example of an operation of a vehicle based ICS is explained by Alstef, supplier of the BEUMER autover® system: ‘Each autoca® fills its mission independantly from the others and waits for the next order. The autoca® sets its speed according to the track section that can be straight, a curve or a junction. Each autoca® is in communication with the autoca® ahead and rear in order to keep a safe distance, and to get into the traffic without stopping the main flow. The autoca® itself selects the best route according to the traffic. The central controller sends orders to the autoca®’ [56].
As already mentioned it is possible to combine a vehicle with a tub. The ‘Bagtrax’ system from Vanderlande allows the container (top part) to be removed from the wheel-supported frame in order to use this system efficiently in combination with an EBS. This system is for instance used in AMS [57]. Figure 17, as retrieved from [58], illustrates this concept.
Figure 17 Vanderlande concept for separation of container and wheel-supported frame. The categorization of baggage transport systems can be visualised as in figure 18.
Figure 18 Categorization of transport systems for baggage.
Very recently, the mechanical and electrical engineering consultancy firm Swanson Rink did an extensive study regarding the benefits of ICS compared to conventional BHS [59]. An important advantage of ICS is that vertical storage in for example an EBS becomes much more feasible since all tubs are equipped with RFID. With individual baggage RFID tagging this would introduce a significant difficulty since the RFID placement is not fixed anymore which makes it harder to relocate the bag. EBS becomes also probably more complicated and expensive without tubs.
Transport systems
Individual carrier system (ICS) Conveyor system
Vehicle version Combined version
(vehicle and tub) Tub version
18 The study included a numerative comparison between the two using several key aspects. These are costs (table 2), environmental impact (table 3) and inbound travel time (table 4). The inbound travel time refers to the time it costs for the baggage to arrive at the baggage reclaim carousel. This is an important figure since it can be related to passenger satisfaction. To be able to generate the required data a model of a BHS was created with 2750 BPH peak capacity outbound and 3500 peak capacity inbound with 12 outbound load points and 18 inbound load points, values representative for a medium to large BHS. All results are based on this model.
There is one aspect of this model worth mentioning in particular. An ICS is different compared to a regular conveyor belt system in one other striking aspect. ICS are looped systems whereas conveyor belt systems are one way systems. This return flow of empty tubs/carts adds infrastructure but it can be used to transport inbound baggage to the reclaim carousel which is exactly what was done in the model.
Table 2 Cost comparison of traditional and advanced BHS [59].
Cost Traditional BHS [$] ICS [$]
Total cost of ownership 470,497,000 411,110,000
Construction cost 120,738,000 143,121,000
Table 3 Environmental impact comparison of traditional and advanced BHS [59].
Environmental factor Traditional BHS ICS Reduction [%]
Global Warming potential [tons CO2] 9560 6570 31
Primary Energy [MWh] 29800 20200 32
Eutrophication Potential [tons N] 3.81 2.99 22
Acidification Potential [tons SO2] 27.5 20.8 24
Smog Potential [tons SO2] 363 262 28
Ozone Depletion Potential [lb CFC-11] 3.59 2.35 35
Table 4 Travel time of inbound baggage to the reclaim carousel comparison [59].
Inbound percentage to reach carousel Traditional BHS [min] ICS [min]
First bag 22 20
50% 40 36
95% 77 50
All figures are clearly showing how beneficial ICS can be. It scores better on all points, except construction costs but the total life cycle costs for the owner will eventually be lower due to lower operational and maintenance costs.
19 Table 5 shows an overview of different commercialized ICS provided by the market.
Table 5 An overview of different commercial ICS.
System (Manufacturer) Type Speed [m/s] Source BTS (Daifuku Logan) Tub 10 (max), 1,5 (curve/merge/
diverge/incline), 1,2 (discharge)
[60]
iDCV (Daifuku Logan) Vehicle 10 (max) [61]
Tubtrax (Vanderlande) Tub 6 (max) [62]
Bagtrax (Vanderlande) Combined 14 (max) [62]
CrisBag® (BEUMERGROUP) Tub 10 (max), 3000 totes/h [63]
BEUMER autover®(BEUMERGROUP) Vehicle 10 (max) [64]
This table shows the speed difference between tub and vehicle type is in general not that big. Compared to conveyor systems which reach around 3 m/s [65] the speed difference is much larger however.
Tracking, checking and communication
As mentioned earlier tracking is one the key tasks of a BHS. Each bag location must be able to be tracked throughout the BHS and at the same the exact position is required for diversion inside the BHS. Barcode identification for tracking individual bags throughout a conveyor system is still common. Recently however identification technology has been replaced or extended throughout the industry with a more modern radio frequency identification (RFID). The benefits include a better accuracy and no requirement for a clear line of sight [66]. An example of a RFID implementation and how the information from the bag is used, is given by Fred Marten, a controls engineering manager at Vanderlande Industries, when talking about the new Terminal 3 at McCarran International Airport in Las Vegas: ‘When a bag is placed on the conveyor, it passes under a reader that interrogates the RFID inlay's unique identifier and forwards that ID number to … VIBES (Vanderlande control software)… residing on the airport's database. The software manages baggage-handling-based data (for example, which luggage is destined for a particular flight), provides localized controls for the conveyor system's programmable logic controller (PLC)—to send instructions to the conveyor system indicating the direction in which a bag should be routed, for instance—and manages the RFID read data’[65]. The exact position of baggage on the belt is determined with additional equipment and methods: ‘…baggage is tracked using ‘photo-eye’ sensors and belt speed to determine its location’ [67]. Typically, each conveyor section is equipped with a photoelectric sensor (also referred to as photo electric cell or PEC). ‘This sensor projects a beam of light across the conveyor and is projected back using a reflector. When this beam is broken, the tracking system knows that a bag is present at this location’ [4]. Further tracking of the bag can be done either by the conveyor speed or by the use of a tachometer in the rollers. The last option adds more accuracy but is more expensive and adds at the same time more complexity to the system. In general these PEC’s can fulfil a broad range of functions (source is [68] unless listed otherwise):
20 1. Overheight detection. Placed at a certain height at input sections of the BHS. Some input sections however can use dedicated equipment to check for both overheight and conveyability such as the BAGCHECK from Vanderlande or the built in sensors of an ABD.
2. Overlength detection. Placed at input sections of the BHS. The blocking time of the sensor signal determines the bag length.
3. Cascade stop. If a bag runs past the PEC while the downstream conveyor is stopped, the resulting signal blocks the conveyor.
4. Jam detection. This is present right in front of potential jam sections such as power turns, incline conveyors and merges. If the signal is blocked for a certain amount of time, while the conveyor is still running, it will stop the conveyor and the downstream conveyor as well.
5. Merge and sort control. Placed in front of merge sections and sortation devices. If a bag runs past the PEC, the conveyor can either be stopped or the sortation equipment can be activated. 6. Collision detection. Mounted for example on vertical sortation equipment, specifically below the infeed conveyor and below the upper outfeed conveyor. This should prevent something (or less likely, someone) is crushed between the moving infeed conveyor and outfeed conveyor
[69]
. 7. Energy saving. Conveyors can be stopped if baggage is not detected for a predetermined time.New baggage will reactivate the conveyors
[70]
.For ICS the use of radio frequency for communicating unique bag information is very common. In independent vehicle type carrier systems such as the BEUMER autover® communication needs to go both ways since the carrier needs to know where to discharge or how to route itself which eliminates barcode technology as an option since barcode technology can merely be used for one way communication. The BHS communicates however only with the carrier so the information of bag and carrier need to be merged together when the bag is loaded inside the carrier [71]. The following text explains as an example how SEAP Automation GmbH, the company responsible for the control and electrical engineering at Frankfurt airport, implemented communication equipment and sensors to realise automation:‘The proximity switches are used to detect the oncoming transport boxes and their transport chassis. The chassis is made out of metal and it carries a transport box made of synthetic material, which contains one piece of luggage at a time. While a barcode is attached to the boxes, the chassis is equipped with reflectors that allow an easy identification on the basis of the so called Hamming-Code. The Hamming-Code is a linear block code that allows an automatic error correction, which makes the machine very reliable. In front of the switches, a barcode scanner reads the barcode attached to the boxes, while an optical code-reader station reads the reflector's code which is attached to the outside of the chassis. In addition to the optical sensors that are integrated into the reading stations, SEAP Automation used light curtains, light sensors and barriers for the transport route. While the light curtains are used to check the luggage overhang and the height control, the other optical sensors ensure a smooth operation of the system by recording every oncoming transport box and giving the signal to accelerate or slowdown the box if needed’ [72].
Before tubs are stacked or accept bags they an ‘empty check’ is required: ‘Before a robot transports the baggage tubs to the inspection station…2D laser scanners control the tubs. The scanners check that the tubs are empty and not stacked inside each other and that the tub elements required for
21 further transport are available’ [73]. At this inspection station the inspection of tubs can also be fully automated: ‘The … 3D vision sensor checks the baggage tubs for deviations from target values. This makes it possible to detect damage to baggage tubs, such as the tiniest cracks, deformations and contour changes, and to replace defective tubs quickly’ [74].’Such techniques can also be applied to vehicle type ICS.
In Frankfurt airport the carriers are passive. With ICS using self-propelled vehicles however the number of sensors can decrease significantly. In the BEUMER autover® system for instance each carrier uses radio frequency to a far greater extent: ‘Each autoca® is in communication with the autoca® ahead and rear in order to keep a safe distance, and to get into the traffic without stopping the main flow’ [56].
Vertical transport
For space reasons it might be better to transport baggage in a straight vertical way. For this several options exist. One option is a continuous vertical conveyor (CVC). This can be either a lift system or a spiral conveyor. Discontinuous systems like discontinuous lifts are available but would not be able to meet the required throughput demand in most of the cases. One exception is at the drop-off where for instance where a single drop off point is combined with one lift. This is shown in figure 6. Separate discontinuous lifts for BHS are offered by Transnorm, whose lift accelerate with 3 m/s2 and are able to reach a top speed of 2 m/s [75]. Throughput depends obviously on the elevation height. A larger distance will decrease the throughput which makes the system less suitable for bigger height differences.
Not much companies offer lift systems dedicated to BHS, most probably since the product is very complex and the demand low. NERAK offers their solution for both trays and loose baggage with a capacity up to 1400 units per hour for height differences up to 40 meter [76]. This system is shown in figure A2 in appendix A. Both configurations are shown there. Logan ksec offers also a similar product with capacities >400 bags/hour [77]. The major disdvantage of the system is the price, due to limited amount of suppliers and the complexity. Other problems are capacity, unflexible loading, reltively large footprint of lift and lift regulations [78] .The capacity is indeed low, when observing for instance the values for modern screening equipment. This means the lift system could become a bottleneck.
A different solution for upward vertical transport is the spiral conveyor. This system uses a slowly inclining belt revolting upwards around a supporting member. The drawbacks of this system are the large footprint compared to a lift system and the system remains quite complex and thus expensive. Moreover, loose baggage could cause problems as a result of mounted wheels. Tubs have a very large area and a low friction coefficient. A DCV system with tubs or demountable containers (Vanderlande Bagtrax) can therefore not be combined with a friction belt but chain push systems as visualised in figure 19 could solve this problem although they are not commercially available. An extra advantage is that such a system could significantly increase the incline. A company offering spiral conveyors suitable for BHS is Ambaflex [79].
22 Figure 19 Visualisation of a push chain system.
With a speed of up to 1.5 m/s [79] for friction based systems a throughput of around 5400 units of loose baggage per hour could be feasible in theory. Even with half this throughput this easily exceeds the throughput of lift systems and screening systems.
The last solution for downward only transportation is the spiral chute. This is a very simple cheap solution but speed control of bags is impossible. This is not necessarily a bad thing since baggage can be blocked and released at the bottom after the position of the bag is known again by the use of scanning equipment. Spiral chutes are offered by many companies like Transnorm [80] or Daifuku Logan [81].
To summarize, the vertical transport equipment can be categorized as shown in figure 20.
Figure 20 Overview of vertical transport equipment.
Due to the significant disadvantages of lifts and spiral conveyors vertical transport are to be avoided as much as possible. DCV systems can use inclining and declining track segments instead is space allows.
Sortation
Sortation can happen anywhere in the BHS. For instance at the screening area to separate cleared and non-cleared baggage. Sortation equipment can also be used to divert baggage for redudancy purposes. For concentional conveyor belts two types of sortation ways exist, the horizontal and the vertical method. Pushers/horizontal diverters perform horizontal sorting and vertical sortation units perform vertical sorting. DCV/ICS systems, however require their own dedicated equipment and methods. Finally, integrated sorters, specifically designed for sorting, can be used in case sortation is very predominant in a compact area and in case capacity requirements are high. This could be the case at the make-up area. Integrated sorters will be discussed first. Note however, that ICS systems may have their own integrated sorting equipment as well.
Tub
Pushing/support element
Vertical transport
Both directions Downward only
Continuous Discontinuous Spiral chute
Discontinuous lift Continuous vertical
conveyors (CVC) Spiral conveyors
23 Integrated sortation systems exist in three types. The first type uses moveable pushing blocks (Figure 21A), a system where blocks (black in Figure 21A) slide over a flat transport surface to push the baggage off track. The second uses built in cross mounted conveyors (Figure 21B) and the third uses tilting trays (Figure 21C) to slide the baggage off by the use of gravity.
Figure 21 Three types of integrated sortation systems.
A disadvantage of the first system (Figure 21A) is that it allows the system to sort baggage only to one side since the moveable pushing block is always obstructing one side.
All three integrated sorters need dedicated feeder belts to quickly transfer a bag on the wooden platform or belt. This happens at an angle of around 45 degrees. Such feeder belts are shown in figure 22. The infeed process requires the infeed belts to transfer the bag exactly at
the right moment, just in time to reach the desired spot on the integrated sorter. To ensure correct transfer, a dedicated sensor detects the leading edge of a bag: ‘…the … switching automation light grid detects the various shapes of their (i.e. the baggage) leading edges shortly before they are transferred to the sorter. The fast response time of the light grid also ensures precise leading edge detection even at high conveyor belt speeds’ [25].
A small overview of commercialized integrated sortation systems is given in table 6.
Table 6 Integrated sortation systems.
Model (Manufacturer) Type Speed [m/s]
Throughput Source Variosort TTS 1100 (Siemens) Tilt tray sorter 2 6000 trays per hour [83]
LS-4000CB (BEUMERGROUP) Cross mounted conveyor
2,5 unknown [84]
TRAXORTER (Vanderlande) Moveable pushing blocks
2 6000 trays per hour [85]
HELIXORTER (Vanderlande) Tilt tray sorter 2 6000 trays per hour [86]
MBHS (Selex ES) Cross mounted conveyor
24 Currently, based on table 6, the largest throughput available on the market is delivered by cross mounted conveyor systems. This observation is confirmed by John Sarineck, chief sales officer for Beumer Group, when speaking about material handling in general: ‘When you require volumes of 15,000 units per hour, a cross-belt sorter is more accurate, can service more destinations and operate at higher speeds than other types of equipment’ [88]. If this throughput is actually necessary depends obviously on the specific situation.
Horizontal sortation is conventional conveyor belts. Three different types of equipment exist as shown in figure 23 on the next page. Push plates or pushers (Figure 23A), diverter arms (Figure 23B) and diverter belts (Figure 23C). Pushers push the baggage off track by hitting the bag perpendicular to the track. Diverter arms and diverter belts direct the baggage off track. Diverter belts have a working belt, diverter arms do not. Pushers have a downside that hitting a bag is much rougher compared to blocking a bag’s path to divert it. This could potentially lead to damaged bags/object in bags.
Figure 23 Different types of sortation equipment.
Table 7 shows an overview of this equipment offered by baggage handling equipment suppliers.
Table 7 Sortation equipment for baggage conveyor belts.
Equipment (Manufacturer) Type Throughput [BPH] Source Vertibelt (Vanderlande) Diverter arm 1200 [89]
Parallel Pusher (Vanderlande) Push plate 1800 [89]
HCD (Vanderlande) Diverter belt 3600 [89]
Model 656A (Daifuku Logan) Diverter belt 1500 [90]
Diverter (Glidepath) Push plate 3300* [91]
Powered plough (Glidepath) Diverter belt 3600 [91]
Flip action pusher (GT) Diverter arm 2660 [92]
Super Pusher (G&T conveyor company) Push plate 4800 [93] *3600 (in double configuration)
It can be concluded that there is a large range in terms of throughput. Push plates can potentially reach very high throughput rates, however with the disadvantage of rough handling as mentioned before.