Application of feedback linearization method for the control of permanent magnet stepper motors

Brush DC motors are the most commonly used motors in the industry. The main reason for this is the ease of control of these motors. However, brushes cause problems that reduce the performance of the motors and also limit their use in certain applications. Therefore, motor designers are in a continuous search of new motor types. The first option that comes to mind is brushless AC motors. These motors can be roughly divided into two groups: Induction motors and permanent magnet synchronous motors. These two types of motors have their advantages and disadvantages depending on the application and the cost. However, when position control is desired the first choice is usually AC stepper motors. They are optimized for position control and are very easy to use. Today, stepper motors with 0.45-degree full-step size are available. Although stepper motors are most commonly used motors for position control, open loop control performance of these motors is not adequate when highperformance is required. Nonlinearity of the motor and step missing problem which may occur when stepper motors are driven at the natural resonance frequency of the motor or at its multiples are among the reasons for this. Field Orientation Control and Feedback Linearization Control methods are used with Permanent Magnet Stepper Motors if high performance is required. vii These two methods are investigated and discussed in detail in this thesis. Structure, basic operation principles, open-loop operation, modeling and closed loop control of these motors are studied with the aid of simulations. Finally, closed loop operation performance with the above mentioned methods are analyzed.