Servo Control Using Switches for Discrete Positional Feedback

摘要

This report describes an approach for providing and/or assisting in thepositional control of a one degree-of-freedom servo-mechanism using switches. The switches, positioned along the path of a moving mechanism, can also be simulated using continuous feedback sensors for certain applications. Real time feedback of the discrete time at which each switch is tripped during motion is provided to the controller. Based on this time-position information, constant motor forces to be applied between switches are determined to sustain and complete the required repositioning task. A definitive control procedure is not presented here, but rather a promising one that may have important applications as we have found in our work. Also, the method is not intended to compete with more sophisticated and complicated approaches using higher component quality and quantity and computer power. On the contrary, one of the intended goals is to go somewhat the other way to make use of existing or even less expensive components. The main contribution that we make to this overall control technique is to introduce and use probability and statistical concepts in determining the switch locations and the required real time motor forces. A probabilistic approach is needed because of the uncertainty in the actual position and velocities of the mechanism as it travels between switches. These uncertainties in turn are derived from uncertainties in the disturbing forces that are encountered during any given motion cycle. In this report, we develop the theory for a statistically-based approach for control using switches. We then verify the results using simulation and experimentation. In our experimental work, we applied our techniques to the ramming mechanism of a large caliber tank autoloader with excellent results.