Mariko Mizuochi

A Wide-Range Velocity Measurement Method for Motion Control

This paper discusses velocity measurement for motor drives with optical encoders. Although many methods on velocity measurement have been proposed, accurate measurement was not achieved in a high-speed range. This paper therefore proposes synchronous-measurement method (S method) that measures the velocity synchronized with the alteration of pulse numbers in each sampling period. Accurate velocity measurement is achieved in all speed ranges with this method. Furthermore, other velocity prediction methods are applicable in addition to the method. Simulation and experimental results verify the validity of the proposed method.

Improvement of disturbance suppression based on disturbance observer

This research focuses on improvement of disturbance suppression even under existence of observation noise. Disturbance observer is an effective tool to estimate and compensate disturbance. There is a problem, however, that it cannot accomplish desired disturbance suppression when a large observation noise exists. In this research, a method with which influence of disturbance can be suppressed greatly even with a large observation noise is proposed. The authors focus on an LPF used in velocity calculation. The method is proposed based on the analysis on the characteristics and mechanism of disturbance suppression in disturbance observer with a focus on its cut-off frequencies. In the method, the cut-off frequency of disturbance observer is set higher than that for velocity calculation. Validity of the proposal was confirmed in theoretical analysis, simulation, and experiments

Force sensing and force control using multirate sampling method

This paper focuses on a bandwidth and a delay of force sensing. High bandwidth force sensing is important for motion control systems to cope with unknown environments. Reaction torque observer is utilized instead of force sensors to detect external force in this paper. The bandwidth of force sensing is limited by the sampling period and data noise. The delay in force information may deteriorate the performance of force control since force information is fed back. According to these considerations, this paper proposes application of a multirate sampling method to the force control system. Reaction torque observer is modified for the multirate system. The bandwidth of force sensing can be improved and the delay in force information can be decreased with the proposed method. The validity of the proposal is verified by stability analysis, simulation and experimental results.