Abstract

Harmonic drive motors are widely used in precision control systems due to several advantages such as zero backlash, high gear ratio, compact size and light weight. However, the combination of friction and flexibility in harmonic drives often limits the performance in positioning applications when using conventional control methods. One problem that often occurs is that the system sticks before the desired position is reached. An alternative and effective solution is to apply a large impulse input for a very short period of time to achieve small motion increments. In this thesis, a new control approach using impulse inputs is developed to improve the resolution of harmonic drive motors. The main objective is to achieve maximum resolution in the presence of high friction levels. A model capable of predicting the impulse response of harmonic drive motors is developed and used to guide the development of an optimal impulse waveform that is robust to parameter variations. The optimal input is then used in the development of an adaptive impulse control method. The performance of the approach is verified with extensive simulations and experiments. Use of the impulse control method demonstrates that the resolution of harmonic drive motors can be increased by more than an order of magnitude. Together, these results provide an effective new approach for control of harmonic drive motors in high precision positioning applications.