Design examples

In this chapter, several design examples are illustrated to demonstrate the validity of the CSD two-port framework. Two different design methodologies with respect to speed control of DC servomotors are presented. These examples will show how industrial controllers, such as pseudo derivative feedback (PDF) controllers and pseudo derivative feedback with feedforward (PDFF) controllers, can be formulated into the standard control design framework and then solved by the state-space solution procedures presented in previous chapters. By defining the transfer function from the load torque disturbance to the controlled output, the dynamic stiffness of a servo control system is characterized, and a scalar index value is defined by the inverse of the maximum magnitude of the transfer function with respect to frequency, i.e., the worst case in the frequency response. Thus, for performance measurement of robust design, maximizing the dynamic stiffness measurement implies minimizing the H_∞-norm in controller design. This chapter will also show how the dynamic stiffness of a servo system can be achieved by H_∞ design.