Vehicle exploitation analysis

University of Technology and Life Sciences

Summary

This paper presents an analysis of maintenance and technical processes which form the basis for testing the quality of life. The desirability of transport enterprises, well-built operating system, based on an appropriate strategy is the basis for opti-mum economic effects.

Keywords: system, operation, use, service 1. Introduction

The process of meeting the socio – economic needs includes the following phases: valuation (the appearance of a need), construction, manufacturing and operation [3]. At the stage of develop-ing the concept of valudevelop-ing a task and its costs, the construction of a vehicle determines the main features of the structure (geometry and material) and an appropriately high level of fitness (growth rate), while the production phase of construction is the realization of the best technologies and materials. The operation is an essential step for the purpose of practical use and verification of the quality of previous stages.

Exploitation is understood as a set of targeted organizational – technical actions and economic factors between humans and technical devices, together with the relations occurring between them. Among the sciences involved in exploitation the following can be distinguished: the theory of operation, reliability, tribology, diagnostics, technical and safety equipment [2].

Road transport companies choose a strategy of exploitation of transport means and facilities depending on current needs to ensure their operation. These strategies are characterized by: equipment reliability, economic efficiency, weight of transported cargo, the number of passengers, time of work or condition of vehicles or equipment. In literature, there is also an authorized service machines strategy [3]. On the basis of a chosen strategy, a system of exploitation of technical means is built.

Because of the nature of transport companies, where vehicles are often at a considerable dis-tance away from diagnostic or repair shops, a state strategy often cannot be applied exclusively, which in stationary situations brings optimal economic results. These companies assume that the vehicle must cover a specific distance and remain technically fit for the next job, which is to be done in the field. Therefore, there used to be a mixed system that combines planning reviews and exchanges with the diagnosis of symptoms – allowing for the prevention of sudden damage. Operation and maintenance of vehicles are mutually dependent on each other and play a key role in transport means exploitation.

2. Process of use

The process of use constitutes a purposeful activity of users on adequate sites, leading in the final stage to perform the assumed tasks, which define the types of use. In the process of means of transportation use these tasks include transportation of people and goods.

Components of the system of using means of transport are as follows: individuals representing a set of users, tasks of determining the types of traffic use, use stations such as roads, cars and infrastructure underlying the service, and relationships between users and tasks against the base.

The structural model of the database specifies the assignment of a set of object users to ob-jects from the base.

Table 1. Structural model of usage base Objects in usage base D A set of users U

D1- roads D2- vehicles ... Dq- infrastructure

U1-entrepreneur 1 1 … 1 U2-driver 1 1 …

... … … … …

Ul-analyst 1 1 … 1

Fig. 1. Transportation means usage graph

Usage process measures. The status of usage of any means of transport can be described by the degree of exploitation resource wear and tear in the use (distance covered, used MPS materials) – L, the time a vehicle spends in a given use state – T and the individual load (cargo capacity) – Q. Use efficiency characteristics of means of transport in time [1]. During operation – T, a vehicle is located at suitable intervals: Tu(t) – in use, To(t) – in service, Tr(t)- in motion, Trp(t) – at work.

Readiness coefficient characterizing the reliability of means of transport in the system of exploita-tion: kg(t) =

)

(

)

(

)

(

t

To

t

Tu

t

Tu

+

t

t

Tu )

(

Users

Base- Road vehicles

u

u

u

d

d

.

d

a

a

a

a

a

a

a

a

a

relations - transports

The degree of the use of a suitable vehicle: krpu(t) =

)

(

)

(

t

Tu

t

Trp

The indicator of vehicle use during operation: krpe(t) =

)

(

)

(

)

(

t

To

t

Tu

t

Trp

+

t

t

Trp )

(

Indicator of usage intensity of given means of transport: Įu =

)

(

)

(

t

Tu

t

L

Indication of exploitation intensity of a vehicle: ae =

)

(

)

(

)

(

t

To

t

Tu

t

L

+

t

t

L )

(

Performed use work in t time t is the sum of the quantities of a used resource set Li, under the burden Qi: P(t) =

¦

QiLi

Indicator of vehicle use:

C(t) =

)

(

)

(

t

qL

t

P

Costs of transportation means usage

The value of costs of vehicle use in the system of exploitation can be represented approximately as a sum of the following components:

Cu(t) = Ct + CL + CQ

Fig. 2. The costs of vehicle use in the operating system

Costs of vehicle use in exploitation system Cu

Costs dependent of usage time Ct

: - salaries - vehicle wear - storing - amortization - road wear - infrastructure wear

Costs dependent on resorce use CL

:

- fuel and grease - vehicle wear - salaries

- energy (electrical, thermal) - road wear

- infrastructure wear

Cost dependent on performer work CQ :

- fuel and grease - vehicle wear - road wear - infrastructure wear

3. Process of transport

Handling is a set of preventive and regenerative processes performed to maintain objects in the state of fitness. Maintenance operations are present to prevent any damage to an object (physi-cal aging, fatigue of materials, mechani(physi-cal damage) – and they include diagnosis, prediction of the state, regulation, reinforcement, lubrication, transportation and storage, which are meant to remove the effects of damage and recovery of fitness, i.e. a diagnosis, repair, replacement parts, transporta-tion and storage; also, the cleanness of vehicle components – replacement, cleaning, transportatransporta-tion and storage.

In the process of exploitation there is the concept of inter-service resource (TBO) – as a number of vehicle usage units (hours, engine hours, miles); after reaching them, it should be subject to certain service formalities.

The next term is the exploitative potential believed to have appeared at the stage of vehicle evaluation and construction and charactering the ability stock to perform work. The exploitative potential is raised and rendered through maintenance operations.

4. Service base and ITS model

A service base is a collection of service posts B. Each post is closely connected with its pa-rameters determining: the type of use operation – op, to – the time of performed operation, qo –

output position, and Co – operation cost.

Tabl. 2. Structural model of a service base Set of users

- owner, shipper, driver Set of base objects

b1- vehicle b2- service post … bk – SKP

u1 1 … … … u2 … 1 … …

… … …

ul … … … 1

U-set of users (owner, driver)

B-set of base components (vehicle, control station) P-set of service employees (driver, mechanic)

Fig. 3. Servicing of the system of means of transport

u

u



u



b

b

b

p=1

p=2,3

P=1,2…P

p=1,3,5

An equation of a change of state “w” of means of transport in a time interval [1]:

dt

dw

= f[w(t0), A(t), B(t), C(t), t] t0 – initial state of the means of transport (9)

A(t), B(t), C(t) – forcing factors

Because of the changing state of a vehicle in time, service processes should include such op-erations as: diagnosis – for the state of an object at any given time t, prediction – for the state of means of transport capable at future moment t + ǻt and genesis – for the means of transport incapable at past moment of the past t – ǻt.

The following methods of servicing means of transport can be distinguished: a dynamic one, which determines the current status, defines variables, optimal operating terms, minimizes the costs of facility maintenance in operational state; a quasi-dynamic one, with fixed service dates, reducing the number of servicing, but raising the costs associated with mandatory servicing; and a static one, which has also fixed service dates established on the basis of experience or a research of population representing a given means of transport, regarded as the least effective and uneco-nomic.

These methods are a basis of the main – scheduled – preventive service systems: diagnostic (dynamic), service with diagnosis and static.

Service system of means of transport in terms of control

Fig. 4. Elements of a working service subsystem in terms of control

A management subsystem has a listing-reporting and planning-decisive function. It aims to collect information about users of resources, database use, and economic indicators of quality and damage relationships. On this basis planning and decision making, as well ad system control and the monitoring of its functioning takes place.

POR – working service subsystem POZ – Service control PBP – service and current repairs PPP – storing PSP – average

repairs PGPrepairs – main Dg – diagnos-tics

POK – control POE – economics POI – informa-tion R – relations R – rela-tions

Fit means of transport are maintained in various ways: without diagnosis, according to the sta-tistical method of use, and with diagnosis, according to the dynamic and quasi-dynamic methods of use which use an external diagnostic appliance, an onboard one and a mixed one.

Fig. 5. Algorithm of keeping means of transport fit 5. Indicators of the service process

Because of the differences in the duration of service operations of means of transport, the ser-vice process is random, and the duration of particular serser-vices are a random variable.

An indicator of stops of vehicle in service ko(t) determines the probability that means of

transport is currently serviced: k0(t) =

)

(

)

(

)

(

t

T

t

T

t

T

+

where Tu- total vehicle usage time (10)

An indicator of passive stops in service k01(t) determines the probability that a vehicle waits

to be serviced and evaluates the effectiveness of the service system: k01(t) =

)

(

)

(

)

(

t

T

t

T

t

T

+

Unit cost of service C0 is defined by the probability that it is contained in the interval [0,C]:

F0(C) = P (C0<C) (12)

Cost of service C is the sum of unit costs which is a random variable depending on the scope of their operations and materials used during the service.

6. Conclusion

The paper gives an overview of two major components of the exploitation of vehicles: use and service along with defining measures of their processes and highlighting an important role of the diagnosis of means of transport, which together with the system of planned maintenance allow to minimize operating costs.

Diagnosis

i

Fit Unfit

Current state change prognosis and a new check-up date

Repair

Determining the

Planned sernice activities

Departure

Entry

Bibliography

1. NiziĔski S.: Eksploatacja obiektów technicznych. IEE, Sulejówek – Olsztyn – Radom 2002. 2. ZeliaĞ A.: Teoria prognozy. PWE, Warszawa 1984.

3. ĩółtowski B.: Podstawy diagnostyki Maszyn. ATR, Bydgoszcz 1996.

ANALIZA PROCESU EKSPLOATACJI POJAZDÓW Streszczenie

W pracy dokonano analizy utrzymania zdatnoĞci pojazdów w nowoczesnym sys-temie diagnostycznym. Systemowe ujĊcie problematyki badania stanu i wypracowywania decyzji eksploatacyjnych prowadzi do racjonalnej eksploatacji pojazdów, optymalizuje zaplecze techniczne oraz umoĪliwia planowanie inwestycji eksploatacyjnych. Strategie według stanu technicznego wkraczają do transportu op-tymalizując koszty uĪytkowania pojazdów.

Słowa kluczowe: eksploatacja, diagnostyka, uszkodzenia, pojazdy, stan techniczny

*This paper is a part of WND-POIG.01.03.01-00-212/09 project.

Jarosław DeczyĔski Bogdan ĩółtowski

University of Technology and Life Sciences Department of Mechanical Engineering