Improvement of robust stability in two-degree-of-freedom control with adaptive control

This paper describes the improvement of robust stability in two-degree-of-freedom (TDOF) control systems with adaptive control. The design for TDOF control systems begins by making use of nominal models. If there is any change in characteristics of the models, system performance is deteriorated. Therefore it is expected that control systems must have robust stability. TDOF control systems are generally designed with trade-off between robust stability and disturbance performance. To improve robust stability in entire operating conditions, here, adaptive control is applied just to feedforward control in TDOF control systems. As a result, TDOF control systems are designed without trade-off between robust stability and disturbance performance. Furthermore, robust performance of control systems is improved. This paper verifies, by simulations and experiments, that robust stability can be greatly improved with the proposed adaptive control in TDOF position control systems.