Robust Full-Closed Control-Based Vibration Suppression for Positioning Devices with Strain Wave Gearing

The plenary lecture presents a practical robust compensator design technique for precision positioning devices including strain wave gearing. Since HarmonicDrive®¹ gear (HDG), a typical strain wave gearing, inherently possesses non-linear properties known as angular transmission errors (ATEs) due to structural errors and flexibility in the mechanisms, the ideal positioning accuracy corresponding to the apparent resolution cannot be essentially attained at the output of gearing in the devices. In addition, mechanisms with HDGs generally excite resonant vibrations due to the periodical disturbance by ATEs, especially in the condition that the frequency of synchronous components of the ATE corresponds to the critical mechanical resonant frequency. The lecture, therefore, focuses on the vibration suppression in positioning, in order to improve the performance deteriorations by applying a robust full-closed control. In the compensator design, under the assumption that full-closed feedback positioning systems can be constructed using load-side (i.e. output of the gearing) sensors, an H_∞ compensator design has been adopting to shape frequency characteristics on the mechanical vibration. The proposed approach has been applied to precision motion control of actual devices as servo actuators, and verified through numerical and experimental evaluations.Registered Trademark in Japan.