Improved robustness of a servomotor system using internal model control

Difficulties arise in automatic positioning applications where a flexible coupling exists between the load inertia and the servomotor. In addition, variability in the load inertia can lead to significant variations in the position tracking capability and stability margins. This thesis develops an internal model control design method as a means to provide consistent output position tracking performance. It is based upon the principle that the primary feedback signal is the difference between the actual load inertia position and that derived by the result of a dynamic model of the flexible coupling and load inertia implemented in the controller. After deriving the theory of IMC design, an experimental system is examined that includes the identification of dynamic model parameters and determination of the internal model controller. A comparison to a conventional design approach is also provided. Simulations are conducting to access the stability characteristics of the internal model control method. Experimental results from a laboratory investigation are also reported to demonstrate the improved robustness of the internal model control method compared to the conventional approach.