Force Control Experiments for Engineering Graduate Students

This paper describes a series of experiments for beginning graduate students in control engineering. The design of a servo driven force controller is the framework for the experiments. Principles of classical and modern control, signal processing, system identification, and design robustness are presented and applied in the elements of experiments. Electronic and mechanical (mechatronic) hardware familiarity is also addressed. Force control methodologies including impedance matching and PID control are studied for stability and achievability of the desired response. Control is studied both in terms of the frequency response and time response. The implemented controller design is digital, using an Intel 486-PC based system. System response under variations of sampling times is examined. Signal processing is introduced in terms of the quadrature motor shaft encoders as well as analog force and position sensors. Anti-aliasing filters are designed and built for the analog sensors. With the instrumentation in place, system identification experiments are conducted to determine appropriate system models. These models are used for controller design. In controller design students become familiar with MATLAB control and signal processing tools. Bode plots, root loci, gain plots and parametric plots along with simulations are used to determine an appropriate controller design, based on the student’s desired specifications and identified model. After successful designs are simulated, they are then implemented on the servo system. Controller hardware and software allows the capture of sensor and state time history data for later analysis, and design validation.