Experimental study on performance improvement of force control by using multi-level converters

In motion control systems, detailed characteristics of power converters and motors are usually not considered. Practically, voltage ripple, harmonics, and electromagnetic interferences (EMI) generated in widely used 2-level converters become concerns to realize a high-performance control. Those possibly degrade the control performance especially in sensitive applications such as the case of small motors, high-speed and high-precision systems, and haptic systems. In this paper, performance improvement of motion control systems by applying multi-level converters is studied experimentally in a force control system of a DC motor. Some experimental results clarify that force control gain and cutoff frequency of DOB (disturbance observer) are able to be larger in the case of multi-level converters compared with the case of 2-level converters. It is confirmed that the multi-level converter improves the force control performance compared with the case of 2-level converter even when an identical control system is used.