Transient response analysis and FF/FB control with 0.05 micro meter resolution for 3-DOF inchworm mobile mechanism

In this paper, we have reported that precise positioning control within one step motion with 0.05μm positioning resolution for a precise inchworm mobile mechanism. The mechanism is composed of 2 Y-shaped electromagnets and 6 piezoelectric actuators and moves like inchworm with synchronism of saw-tooth magnetic forces and sinusoidal displacements of the actuators. In previous report, we have reported that the mechanism moves straight in any direction with 80μm step width. We have also described that we can approximately calculate the displacements of 6 piezoelectric actuators with 3-DOF simple harmonic vibration model for getting coarse positioning of 3-DOF movements. However, we still need to control within 1 step motion for precise positioning with less than sub-micro meter resolution. In this paper, we describe ideal input voltage to the 6 actuators under the condition of no slip of supporting electromagnet. In experiments, we have checked that we can control the free leg within 0.3μm when positioning range is between 5 to 30μm under open loop condition. We have also checked that we can control the mechanism within 0.05μm within 0.05 second when we join ideal input voltage as feed forward control and PID closed-loop control as feedback. We also discuss about applications of bio-medical and nano science to open up flexible, high efficiency, and multi-function micromanipulation organized by this omnidirectional and holonomic mobile mechanisms.