Nonlinear Control of Electric Motors

Electromechanical actuators have been utilized in many applications from home appliances to sophisticated guidance and control systems. Various electromechanical actuators such as electric motors, hydraulic and pneumatic actuators, smart materials (e.g., piezoceramics, magneto-restrictive materials, shape-memory alloys, electrorehological fluids, etc.) have been considered. Modeling and control design for such actuators have been and are pursued to achieve a higher level of performance. As a part of our on-going efforts, we consider modeling and control design of electric motors, namely step motors, brushless DC motors, and induction motors. These electrical motors are used in many applications; some requiring a high level of accuracy and performance such as machines used in electronics industry for assembly or semiconductor wafer probing and inspection.

To achieve high precision and bandwidth for the motors, we explore modeling of these devices to the extent needed to provide a high performance controller but at the same time amenable to model-based nonlinear designs. To this extent, we consider nonlinear and adaptive controllers to derive robust and high performance feedback controllers which are essential for applications that require high performance and accuracies. The recent nonlinear and adaptive design tools have been shown to be effective in designing controllers to achieve robust performance. We have utilized existing nonlinear tools and their extensions to design robust adaptive controllers for various motors under full state or partial state measurement (sensorless control). We have experimental test beds for such motors at the Control/Robotics Research Laboratory at Polytechnic University and one such test bed is a dual axis linear stepper motor used in electronics industry.