The conventional proportional P controller has been often used as the position controller of the dc servo motor. When the unknown and inaccessible load torque, such as the coulomb friction, the gravity, and so on, is imposed on the dc servo motor, this control system has the steady- and/or transient-state error. This error will be reduced by a new method in the paper, which is based on the observer theory and programmed in the microprocessor. The deadbeat observer in this paper can estimate the sum of all the external forces quickly with a very simple structure. The new torque regulator based on this observer is expected to realize no steady-state-error and little transient-state-error position control even in employing only the P controller, whether various types of external force are imposed or not. Moreover, according to the observer theory, this system has merit in that this response to the external force can be determined independently of the response to the position reference. Numerical and experimental results are also shown.
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