Smoczek J., Szpytko J. To improve safety and reliability of the device in transportation processes via integrated monitoring system of control process.

TO IMPROVE SAFETY AND RELIABILITY OF

THE DEVICE IN TRANSPORTATION

PROCESSES VIA INTEGRATED MONITORING

SYSTEM OF CONTROL PROCESS

Smoczek J., Szpytko J.

AGH University of Science and Technology, Mickiewicza Ave. 30, PL 30059 Cracow, Poland

Abstract: The paper presents research methodology of control methods influence on exploitation

quality and technical state of the selected transportation devices and precision realised transportation tasks. The example of monitoring system of control process of crane movement and chosen exploitation parameters was shown. Proposed control-monitoring integrated system enables to supervise crane control and exploitation process for analysis and evaluating technical state of the device and quality (with safety and reliability aspects) realized transportation tasks.

1. Introduction

Technical state and reliability transportation devices have more and more important issue in automated industrial processes influencing on quality and precision of realized tasks as well as quality of the operation and efficiency in industrial process [1, 2]. In transportation systems and devices quality and precision realized tasks as well as technical state of the devices depends on executive and control subsystems. From users point of view it is important to optimize movement of the shifting load that concerns following problems:  precision of positioning of the shifting load,

 minimising swinging of the load,  minimising bridge’s bevelling,

 overloads minimising in driving mechanisms and constructions,

 elaborating and following movement trajectory of the load without collision.

It is not always possible to solve above problems by entirely automation of transportation process. In systems, in which control process is realized by crane operator proper execution of transported tasks depends on co-operation human-machine system. Proper co-operation depends on technical means, solutions and devices applied in driving, control and assistance subsystems adjusted to the operator’s psychophysical abilities as well as operator’s experience and knowledge about controlled process. Monitoring of control

process and technical state of the device enables to evaluate influence used control methods realized by operator and technical solution applied in control and driving subsystems on technical state of the device and exploitation quality.

Information gathered during monitoring could be a source of knowledge used farther in implementation new technical solutions. Experience and knowledge of the operator can be used in building intelligent decision making system or intelligent control system basis on expert systems, artificial neural networks and fuzzy logic. Via integrated monitoring system of control process and technical state of the device in transportation processes is possible to improve safety and exploitation reliability.

2. Integrated monitoring system of control and technical state of the

device

Analysis and evaluation of a crane control techniques influence on technical state of the device and precision of realised by crane operator tasks needs to conduct researches on:  possibilities of development and using new solutions in crane’s driving mechanisms

and technical solutions enable to counteract undesirable phenomenon type of crane’s bridge bevelling and swing of a load,

 influence of crane’s control methods and possibilities of implementation unconventional control systems (e.g. intelligent control systems) to improve control quality and technical state of the device,

 conditions and factors that have negative effects on the crane operator work, his health and quality executions tasks.

For realizing above researches’ directions it is necessary to elaborate and build monitoring system which gives possibility to analyze and evaluate technical state of the device and research the influence on its control methods and technical solutions employed in executive and control subsystems. This analysis should be conducted basis on assumed indicators of control process and selected parameters of device’s exploitation, measured on-line as well as off-line. In consequence of this analysis, it will be taken the assessment of tested control methods and solutions in driving and control subsystems as well as possibilities employing new technical solutions.

For researches needs the following indicators of quality control process and technical state of the device have been assumed:

 precision and time of transported load positioning (offset and angle of swing load),  angle of crane’s bridge beveling,

 overloads in crane’s driving mechanisms during transient states (real power consumed by crane’s motors),

 deformations and stresses in bridge’s construction and in ropes as a function of load and crane’s trolley position on the bridge,

 time delays in control and executive subsystems (e.g. starting and braking time, time of breaking release switching on),

 errors of wheel-rail geometry (errors of wheels setting and roadway geometry). Basis on above information gaining on-line or off-line it is possible to make analysis and assessment of control results realized by crane operator and their influence on technical state of the device (Figure 1). During monitoring, basis on gathered information the analysis is made regarding to:

 used control methods and technical solutions in driving mechanisms influence on technical state of the device: overloads in construction and driving mechanisms,  technical state of the device and used control methods influence on movement

precision during handling a load: positioning of a load, time of working cycle, dumping of a load swinging,

 load value and its distribution and overloads occurred during transient states of working mechanisms influence on technical state in wheel-rail system and undesirable phenomenon in this system, type of crane’s bridge bevelling.

Analysis of technical state of the device and quality of realized working movement during transportation tasks executing, conducted basis on selected exploitation parameters gives possibility to estimate usefulness used technical solutions in control and driving subsystems and shows direction of development new applications to improve safety and reliability of the device and transportation process. Basis on this information it is possible to define exploitation indicators W as a function of parameters monitored during devicei working Ej: ) e , , P , t , t , , , z , y , x , z , y , x ( F ) E ( F Wi  j        k k k  k (1) where: z , y , x , z , y ,

x    - positions and velocities of crane’s movement mechanisms,



 _{- angle of a bridge’s bevelling,}

t - time of a working cycle (or time of load positioning), k

t

 - time delay in driving and control subsystems,

k

P - real power consumed by motors,

k

 - deformation bridge’s construction and ropes,

k e

 - geometrical errors in wheel-rail system.

3. Intelligent control system of a crane movement basis of

operator/engineer knowledge

Device exploitation quality improvement, desiring to obtain minimization of the time load shifting during transportation process and precision in positioning with angle of the swing load minimization are ore and more significant in practice that put high demands before applications used in driving and control systems. Complexity of phenomenon occurred during loads transportation process using cranes as a result of wide change exploitation parameters causes that in crane’s control systems are required tools taking into consideration complexity of such systems characterized by uncertainty, imprecision and subjectivity of parameters. One of that mathematical tool is fuzzy logic which is a nonlinear system that convert a crisp input vector into a crisp output vector. Fuzzy models are experts systems in which control strategy is expressed in form of IF-THEN rules built using linguistic terms that gives simple and legible interface in process of controllers’ realization. It allows to elaborate control strategy basis on knowledge and experience users of controlled process using natural language and next implementation of this

algorithm as a fuzzy model using if-then implication. Knowledge of the experienced user could be obtained, for example by questionnaires or verbal description of operator’s decision process, taking into rules show his behavior depending on changeable input information: “if state of the process is… then it should …”

Control strategy of experienced crane’s operator whose aim is shifting load from the point A to the point B with minimizing load swinging after starting and during braking trolley or bridge movement mechanism can be described in linguistic form and next translated on fuzzy rules and converted in inference system of fuzzy model emulating human decision process (Figure 2).

Fig. 2. Operator’s knowledge implementation in fuzzy control system

Presented in the figure 3 control-monitoring system of an overhead-traveling crane was elaborated and realized on the real object, the two-spars overhead crane with Q = 12,5 [t] hoisting capacity and bridge width L = 16 [m] working in the workshop.

Figure 3. Control and monitoring system of an overhead crane

The aim of the realized system was crane’s movement mechanisms control, visualization and monitoring chosen exploitation parameters of the device. System was based on PLC (Programmable Logic Controller) controller and PC computer with HICAP video card, data acquisition cards type of PCL 818HG and InTouch SCADA program. In the presented system the following subsystems can be distinguish:

 control system with PLC controller witch realizes control algorithm of crane’s movement mechanisms (bridge, trolley and hoisting mechanism) equipped in frequency inverters enable to smooth velocity and torque change,

 measurement circuit composed of sensors enable to measure the exploitation parameters for control and monitoring purposes (e.g. position and velocity of crane’s movement mechanisms, swing angle of the transported load and power consumed by driving mechanisms) and PC computer with data acquisition card type of PCL 818HG for measurement signal gathering,

 visualization and monitoring system built using HMI (Human Machine Interface) tool, InTouch program on PC computers connected by wireless LAN net connection.

Application built in InTouch program allows providing desired position of the load in three dimensional space and monitoring crane’s movement and selected exploitation parameters measured by sensors. InTouch program communicates with PLC controller by using OPC standard communication. OPC server enables connection between PLC controller and other PC computers with OPC clients (InTouch applications) using wireless LAN net connection. Proposed solution enables to realize operator’s stand over crane’s cabin as well as dispatch room where transportation process in workshop could be monitored and supervised. Presented example of control-monitoring system based on telematics solutions helps in decision process during realizing transportation tasks. Views from the cameras directed on crane’s working spaces enable better operator’s visibility that is often limited from crane’s cabin.

Proposed integrated control-monitoring system based on PLC controller, data acquisition cards and Matlab and InTouch programs enabled to gather information about exploitation process of the device and influence used control methods realised by operator and automated system on technical state of the device and quality realized tasks. It also gave possibility to elaborate, built and conduct real time experiments for prototyping conventional PID and fuzzy control systems based on TSK model (Takagi-Sugeno-Kang). Control algorithms were elaborated and tested during simulation on the mathematical models and during experiments on the real object and next implemented on the target control device, PLC controller [1, 2].

5. Conclusions

In transportation systems and devices quality and precision realized tasks, as well as technical state of the devices depends on executive and control subsystems. If control process is realized by operator it is important proper co-operation human-machine system depending on technical means, solutions and devices applied in driving, control and assistance subsystems adjusted to the operator’s abilities, experience and knowledge. Monitoring of control process and technical state of the device enables to evaluate influence used control methods realized by operator and technical solution applied in control and driving subsystems on technical state of the device and exploitation quality overlooked by system safety and reliability. Information about controlled process, heuristic knowledge of the operator can be used for building intelligent system supporting decision process of control.

The research project is financed from the Polish Science budget for the years 2005-08.

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