Design and implementation of optimal digital variable gain controller

The hardware and software design and implementation of an efficient microprocessor-based digital control loop for optimal gain tuning is described. A method is proposed whereby the gain of the system controller is varied continuously, so as to improve the dynamic performance of the closed-loop system response. It is shown that the optimal gain at any instant is a function of the system's states at that instant. The optimal gain tuning for the gain controller is solved analytically using the Phillips integral algorithm in the sense of minimizing the integral squared error (ISE) criterion formulated in the time domain. The theoretical system response and that of a real-time implementation are compared. Experimental results demonstrate the advantages of the controller. Suitable accuracy can be achieved using A/D and D/A converters with 12 bits as input to the microprocessor or output from it. The average time required for the microprocessor to compute the value of the time-varying gain control is 17.58 ms when the operating frequency of the 8085 microprocessor is 3 MHz