FPGA Logic Devices for Precision Control: An Application to Large Friction Actuators with Payloads

Precision control, which has the goal of making control precision approach measurement precision, is an important subject in modern control engineering. Control theory based on continuous-time systems has long reached this objective by providing tools for ensuring asymptotic stability and convergence. However, it is difficult to obtain this degree of precision control in discrete-time nonlinear systems such as a computer-controlled actuator with friction. This is because the z-transform, the common analysis tool for discrete-time systems, is not applicable to nonlinear systems. Furthermore, computation delays are inevitable in control implementations as long as digital signal processors (DSPs) or central processing units (CPUs) are used, necessarily resulting in systems that are discrete by nature. Thus, the discrepancy between the use of continuous-time systems in design and analysis and the use of discrete-time systems in control implementation has become a long-standing problem in the control of electromechanical systems, which fundamentally challenges the precision control objective.