Dynamic modelling and torque ripple minimization of a lightweight ultra-high transmission ratio harmonic drive

Abstract

Harmonic drives have been of significant importance in many industrial and high-end applications including robotics, aerospace and manufacturing. Their unique characteristics combine high torque capabilities, high to ultra-high transmission per stage and low backlash performance in compact designs, suited for limited space applications. However, apart from the eminent merits of the technology, this type of gearboxes is associated with complex dynamic performance. Since their operations is associated with high compliance and friction a non – linear behavior is imposed to the system. This is also intensified due to torque ripples which in many cases apart from adding up to the overall complexity of the system, can also interfere with components of similar resonance frequency. In the frame of this paper a novel concept for a low-cost lightweight plastic harmonic drive used in positioning of telecommunication antennas is presented. Due to the tight dynamic specifications of the application (settling time, positioning error etc.) the torque ripple of the transmission was modelled and minimized. Design changes were also incorporated in various features in order to improve the overall dynamic performance.