Development of a novel strategy based on in-process compensation of charge leakage for static force measurement by piezoelectric force sensors

Abstract

Ordinary piezoelectric force sensors are only capable of measuring dynamic forces but not static forces because of the charge leakage due to the finite resistance of piezoelectric materials and charge amplifiers. This paper presents a new strategy for in-process compensation of charge leakage for force measurement with wide spectrum from static to dynamic realized by piezoelectric force sensors. The compensation is in-process operated based on the concept of dynamic accumulation. In order to improve the measurement accuracy and long-term stability by the compensation, the zero offset generated by normalization, bias current and temperature drift are all theoretically analyzed and experimentally validated. Measurement experiments of four different types of force signals, which contain static, triangle, sinusoidal and random force signals acting on the piezoelectric force sensor, are conducted to validate the proposed strategy. In addition, the effect of different time constant of the piezoelectric sensor under different applied forces on the compensated results is analyzed. Performance tests contain accuracy, resolution, span and bandwidth have been conducted. It is validated that the proposed method has high sensitivity of sub-millinewton, long-term stability and wide spectrum from static signal to dynamic measurement capabilities, which would provide an effective and precise method for micro force measurement and control in ultra-precision machining, semiconductor industry and biomechanics fields.