adaptive controller to a dc motor for high performance tracking applications ... proposed technique, the rotor position and/or the speed of the dc motor is forced to ...
89 WM 244-5 September 1989
89 WM219-7 September 1989
Adaptive Tracking Control for High Performance DC Drives
Transient Behaviour of a Current-Source Inverter-Fed Synchronous Motor with a
Siri Weerasooriya, Student Member, and M. A. El-Sharkawi, Senior Member Department of Electrical Engineering, FT-1 0 University of Washington Seattle, WA Abstract-This paper presents a novel application of a modified adaptive controller to a dc motor for high performance tracking applications, such as robotics, actuation and manipulation. By the proposed technique, the rotor position and/or the speed of the dc motor is forced to follow preselected tracks, even when the load condition varies. An algorithm based on Minimum Variance Self Tuning control is developed for this purpose. The adaptive controller is effective even in the presence of external disturbances, provided that the system exhibits minimum phase characteristics. The effectiveness of the controller is demonstrated by using a general purpose nonlinear simulation software. The simplicity of the algorithm and the promising test results prove that this proposed controller is very effective in high performance tracking applications. Summary The utilization of dc drives in complex applications such as robotics manipulations requires not only a position control at the final time, but also tracking or trajectory control. A track is a time history of position and/or velocity that the end effector of a manipulator should follow at all time. This may require that each motor in the manipulator follow its predetermined speed or position track during starting, speed change and breaking, but without causing excessive stresses to the entire system's hardware. In many drives applications, the mechanical load varies considerably during operation. Robots and machine tools with changing load inertia are two typical examples. When a fixed controller setting is used in a drive system with a widely changing load, unsatisfactory performance is often produced. This is quite obvious in positioncontrolled drives where slightly misaligned controllers can cause considerable overshoot and oscillations. In tracking applications, such a control system is deficient and can not be considered a viable option. The requirement for high performance drive systems in various industrial applications has produced great research efforts in the application of modern control theory, particularly adaptive control. With the rapid evolution of semiconductor technologies and microelectronics, practical application of such advanced control algorithms have been made possible. Microprocessor based digital control schemes have become indispensable in these applications. Various adaptive control algorithms have been proposed for trajectory control. Unfortunately, most of these algorithms are rather complex and need excessive computational time for real time implementation. In motor drives, where microprocessors are used as controllers, any algorithm complexity is quite a large obstacle to overcome specially in high speed real-time process controllers. In or
separate processor has to be dedicated for system identification, while a second processor performs the adaptation and monitoring tasks. In this paper, the Minimum Variance Self Tuning (MVST) control strategy is modified and utilized for tracking control of dc motors. The MVST control is well known for its simple algorithm and implementation even with slow microprocessors. The major restrictions when MVST is applied are that the system must be a minimum phase, that the process time delay is known and that a bound can be given to the order of the system. This paper shows that when the performance index of the MVST is selected as a variance of the error between the actual motor output and its corresponding desired track, the tracking capability of the motor is outstanding. To illustrate the effectiveness of the proposed many cases a
adaptive tracking controller, the entire system is simulated by a general purpose nonlinear dynamics simulator software. Load variations are allowed during the control process to validate the effectiveness of the controller for high performance drive applications.
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