System development of an admittance-controlled 2-dof haptic device using electrostatic motors

This paper describes the system development of an admittance-controlled 2-dof haptic device using electrostatic motors. The unique point of the device is that all components including the motors and sensors are fabricated using non ferromagnetic materials to realize operation in a strong magnetic field. The device consists of an operation handle, two electrostatic motor units and two optical force sensors, and is an improved version of our previous development. The new device has stiffer platforms, improved force sensors, and newly fabricated driving electronics. The employed electrostatic motor is one of the strongest electrostatic actuators and can generate thrust force of several newtons. To operate a motor unit, two three-phase signals are required and they have to be amplified to over 1 kV. In our previous development, the signals were amplified by six large commercial amplifiers, which was not practical enough considering the portability of the system. This work developed an original driving electronics for the motor using Field Programmable Gate Array (FPGA) and step-up transformers to reduce the system size. The device was implemented on one of the major haptic toolkits, CHAI 3D. To be able to run sample impedance-type programs without any modifications, we implemented our device to behave like impedance-type on CHAI 3D.