毕业设计英文翻译

Task-oriented Analysis and Design Method for DeVeloping PLC Programs for

Mechanical System Control

Ma Yinyuan, Jiang Zhaoyuan

Institute of Mechanical & Electrical Technology, Lanzhou Jiaotong University, Lanzhou,

Gansu 730070, China

Abstract—To reduce the difficulties in developing PLC based control software for

mechanical system, an approach named task-oriented analysis and design (TOAD) is

proposed. TOAD emphasizes task centric and model centric developing process. By their

property, control tasks are classified as private-sequential task, global-real-time task and

asynchronous-concurrent task. The classification prompts developers to find tasks and to

analyze a system. Hierarchical modeling method is presented. Intertask communication and

multitask scheduling method is given. The method is demonstrated using a case study of

elevator control software. By encapsulating the tasks into subroutines, and by means of

setting or resetting the enable input bit of the subroutines to enable or disable the subroutines

to be executed or not to dispatch the tasks, a structured and time-efficient program is

developed, which can be reused as a framework of the PLC software for mechanical system

control.

Keywords-control

systems; software development; task- oriented; PLC; framework

I. Introduction

It is difficult to develop PLC control software for modern mechanical equipment. An

approach named model-driven development of the control software is proposed in [1].

However, the approach is still rather rough and lacks of implemented example -

“Future work will focus on the implementation of methods for automated model transformation, the further formalization of modeling constructs and their integration and

validation based on complex examples from the industrial field”. There are some modeling

methods and examples of the mechanical control software described in some papers. But the

mentioned methods and modeling examples complicate the problem. And they are

unpractical for various reasons [1]. Take the typical mechanical and electrical system -

elevator control software as example, there are improved Petri Net model, improved UML

model, object-oriented models and so on. However, some models are divorced from reality,

which is unhelpful for the developing of the real system. Some models just simulate the

behavior of the system, which is far away from the system control of elevator. Four types of

PLC programming design methods for mechanical control system are extracted in [2], While

these design methods focus on detail technical. And all the paper lacks of exhaustive

descriptions of the development process from system analysis to the realization. Readers still

feel lacking referable example in designing similar systems, and they do not know how to

begin with.

TOAD (task-oriented analysis and design) method presented in this paper is a

model-driven system development method which focuses on analysis of control task and

implementation of the mechanical control systems. TOAD method uses UML statecharts as

modeling state machine) model which proposed in the paper [3] is essentially the same.

However UML model is much easier to be transformed to software implementation [4].

Different from TOAD, the method proposed in [3] adopts module based framework at the

system level, which is object-oriented. And the realized system combines object model and

NFSM model. This method takes different modeling methods at two levels, which makes it

harder to master and use. TOAD method applies the task-oriented perspectives to two levels,

which can simplify system analysis and integration.

Few papers referred to framework technology in PLC software development or utility

based on framework. The control system software model based on UML statecharts has given in this paper, which adopts elevator control as the object. The control system has

implemented, which is transformed from the model, which can be used as a framework of

the similar control software.

II. Finding Out Tasks and modeling the tystem

A. Define Tasks According to System Functions or States

TOAD method requires starting system analysis from finding out the functional subunits

of the system function. The functional subunits, which are defined as tasks, provide the first

dimension of mechatronic control software in a modular way. The system can be analyzed

according to different behaviors of the system in different time periods, or according to

different functional requirements, or according to the fiinction components of the system to

decompose the system. For example, some systems require manual and automatic functions,