Combination of VCA based micro force generator and micro robot for micro hardness and stiffness test

This paper presents the development of small force generator mechanism with voice coil actuator and piezo driven micro robot for surface hardness and stiffness test. This small force generator is composed of voice coil actuator and parallel leaf spring mechanism. The small force can be controlled by current which is supplied to coil and positioned precisely at the balance point with the parallel leaf spring with no mechanical friction. And the full bridge strain gauges on both side of double leaf spring can detect small force which is applied to the micro indenter. This unique layout can provide good linearity and small force up to 20 mN with 0.05 mN resolution. The displacement of the indenter head also can be measured by the laser displacement sensor for monitoring the depth behavior of the indenter during whole dwell time. Since the overall size of this system is compact enough to operate inside special chamber for bio-cell stiffness analysis application. This small force generator unit is set up with the piezo driven inchworm micro robot for carrying the test sample to be measured. This micro robot can move precisely step by step with 1 μm resolution on metal plate. In the experimental results, the elasticity investigations with several samples are successfully checked by the indentation load-depth curve.