A software tool development for pneumatic actuator system simulation and design
Introduction
Pneumatic actuators have been widely used in the applications for simple speed control in industrial process and automation. In recent years, the ready availability of low cost microprocessors and advanced mechantronic components allow industrial users to consider adopting pneumatic actuators to accomplish more sophisticated motion control tasks [1], [2], [3], [4], [5]. However, there exist some difficulties in pneumatic system control and analysis which are associated with air compressibility, significant friction and non-linearities [5], [6], [7]. This leads to a demand for an assistant software tool to be used for dynamic analysis of pneumatic systems to address those difficulties in system design. Most current available pneumatic system CAS, CAD software packages are mainly developed for the purpose of pneumatic circuit designs [8], [9], [10], not for pneumatic system dynamic analysis. Therefore, development of a software tool for pneumatic actuator system simulation and design is proposed in this paper.
The software should be easy to use, easy to understand, re-configurable, and easy to simulate the dynamic behaviours of pneumatic systems. From analysis of current software design technologies, a components-based software design method is adopted in the paper, together with the features of graphic user interfaces (GUI).
Components-based software design method is a new phase in object oriented methodology evolution. The recent development in component technology enables the construction of complex software systems by assembling together off-the-shelf components [11], [12]. The major characteristic of a component is to be considered as a unit of independent deployment and has no persistent state [13], [14]. This design method is now widely used in CAD software design. A software component should show same dynamic behaviours as its real world counterpart and should adopt the standard interface for the convenience of system integration. The software implementation of a component contains program code and data, which can be considered as an independent unit for users to pick up to connect with other components to form a complete pneumatic system. Their interfaces allow them to accept input and feedback information from and also send output and feedback information to those components which are adjacent to them. A typical example of component structure is shown in Fig. 1.
The pneumatic system components are initially organised into five major categories, which are compressed air supplies, valves, cylinders, control strategies and miscellaneous parts (for example, connection pipes). The above organisation is determined based on the mechanical structure of pneumatic systems, which is generally the classification shown in the manufacturers’ catalogues. The way of organising the components’ classes may lead the users to feel same when they pick up the components from the library as they are picking the components from the manufacturers’ catalogues. A component library accommodating these five classes of components is then built up on the basis of dynamic analysis of pneumatic systems and component models. Users can pick up different components from the library to construct a complete pneumatic system. The dynamic behaviours of the complete system can be simulated in different operating modes. The graphic user interface and animation techniques are adopted in software design to create a user-friendly environment. MATLAB-SIMULINK is used to implement the software design. Three different kinds of software structures have been investigated and compared in the paper which reflects the route of the authors’ thinking in designing the software.
Section snippets
Development of components models
From the analysis of dynamics of individual pneumatic system components and the standard orifice theory, the mathematical models for individual components are derived in this section.
Pneumatic system CAS/CAD software development
The components-based design method is employed in the development of the software. All pneumatic system components are organised into different classes on the basis of their hardware natures. A software library is then formed to accommodate those components like the real hardware component stores. The simulation program in the system level can be built through assembling the components picked up from the library. The procedure is illustrated in Fig. 3.
To connect the components together into a
Applications of the software tool
To demonstrate the way of using the software, two application examples are given in this section, one is the model validation and another is the PID servo control system.
Discussion and conclusion
A components-based design method is adopted in the development of the software for pneumatic system CAD and CAS. Although the paper does not discuss implementation of advanced control strategies such as fuzzy and non-linear control for pneumatic systems, it provides a flexible way for users to design and add different new components of control strategies into the library. So the structure of the software is open for further development. The software is still in its early stage and has only been
Yuan Yuan Lin-Chen received the BE degree from the Department of Electrical Engineering, Xi’an Jiaotong University, China in 1989, and MPhil degree from the Department of Electrical Engineering and Electronics, University of Liverpool, UK in 2001. She is currently a PhD research student in Control Theory and Applications Centre, School of Mathematical and Information Sciences, Coventry University, UK. Her research interest includes feedback control of imperfectly known, singularly perturbed,
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Yuan Yuan Lin-Chen received the BE degree from the Department of Electrical Engineering, Xi’an Jiaotong University, China in 1989, and MPhil degree from the Department of Electrical Engineering and Electronics, University of Liverpool, UK in 2001. She is currently a PhD research student in Control Theory and Applications Centre, School of Mathematical and Information Sciences, Coventry University, UK. Her research interest includes feedback control of imperfectly known, singularly perturbed, dynamical non-linear systems with time-delay.
Jihong Wang received the BE degree in automatic control from Wuhan University of Technology, Wuhan, China, in 1982. She received the MSc degree in automatic control from Shandong University of Science and Technology, China, in 1985 and received the PhD degree in non-linear uncertain system control from Coventry University, UK in 1995. Currently, she is a lecturer with the Department of Electrical Engineering and Electronics, University of Liverpool, Liverpool, UK. Her main research interests include non-linear system control, motion control, power systems, and intelligence engineering.
Q.H. Wu (M’91–SM’97) received the MSc degree in electrical engineering from Huazhong University of Science and Technology, Wuhan, China, in 1981. He received the PhD degree from the Queen’s University of Belfast, Belfast, UK in 1987. Currently, he is the Chair of Electrical Engineering with the Department of Electrical Engineering and Electronics, The University of Liverpool, Liverpool, UK acting as the head of Intelligence Engineering and Automation Group. His research interests include adaptive control, neural networks, learning systems, evolutionary computation, and power system control and operation.