Positioning Control of Single-Link Flexible Arm Using Frequency-Shaped Sliding Mode Control Theory

This paper is concerned with the positioning control of a single-link flexible arm using frequency-shaped sliding mode control theory. In the control object, a harmonic drive system for a reduction gear has a large friction torque, and thus we applied the sliding mode control theory to this positioning control problem in order to compensate for the nonlinear friction torque. We designed the control system using the output feedback method. The high-gain sliding mode controller, however, often causes instability of the control system due to spillover phenomena in the high-frequency region. Therefore, we also design a switching hyperplane using H∞ control theory which can suppress such spillover phenomena markedly. We found that the frequency-shaped sliding mode control system exhibits good performance. However, the system performance is influenced by uncertainties which do not satisfy matching conditions.