Research On The Measuring Principle And Performance Of Integrated Piezoelectric 6-Axis Force Sensor

Because of the ability to realize the measurement of three force components and three moment components applied on the object simultaneously, the six-axis force sensor, acting as the primary link in the measurement and control system, has been widely used and works well in the fields of aviation and space, intelligent robot and military. But, with the measurement requirements increasing and the measurement conditions getting harsher, in some fields where the space for the sensor’s installation is narrow or the high accuracy of dynamic measurement is required, limited by the technique’s performance or the size of the sensor’s construction the current measuring technique cannot work well, so it is of great significance and necessity to develop a small-size piezoelectric six-axis force sensor.With the research aim, and based on the piezoelectric effect and theory of elasticity of anisotropic body, in this paper the distribution law of the induced charge on the surface of quartz wafer under six-dimensional forces is researched. Based on the law, a novel small-size integrated piezoelectric 6-axis force sensor is developed, then static calibration experiment is conducted to acquire relevant accuracy indexes, the idiographic work is as follows:According to the mechanical property of anisotropic body, the coupling effect of bending moment and torque applied on the wafer is analyzed, then the stress distributions in the wafer under 6-axis forces is researched, with the six stress components obtained, indicating the normal stress is only dependent on normal force and bending moments, the shear stress is only dependent on shear forces and torque.Then, regarding the XO-cut and YO-cut quartz wafer as the analysis targets and based on the piezoelectric effect, the mapping relationships and the composite piezoelectric equations between the forces and the density of induced charge on the surface are built. Dividing the wafer surface into several areas, the linear equations between the quantity of electricity on each divided area and the multi-dimensional forces are deduced. After the theoretical calculation, the piezoelectric simulation analysis of quartz wafer under multi-dimensional forces is made by using Ansys, achieving the electric potential distribution and the electric field intensity distribution. Besides, the relationship between effect of composite loads on the wafer and the superposition of each effect of single load on the wafer is analyzed. The simulation result presents a consistency with the result of theoretical numerical calculation.Finally, based on the theoretical analysis and the conception of measuring the quantity of electricity on each area by positioning several electrode slices on the whole surface, a small-size integrated piezoelectric 6-axis force sensor, whose core element is a delicate quartz chipset. In order to check if the sensor can work well, a static calibration experiment platform is built and the static calibration experiment is conducted, getting the accuracy indexes, such as linearity, repeatability and transverse interference. Also, the compensation analysis on the interference error is made.The results of theoretical analysis and calibration experiment make it clear that single wafer or chipset unit can realize the measurement of multi-dimensional forces and the development of an integrated piezoelectric 6-axis force sensor is feasible, which promotes the innovation of piezoelectric theory. By reducing the size of piezoelectric 6-axis force sensor essentially, the dynamic measurement requirements in narrow space can be met and the application areas of piezoelectric 6-axis measuring technique will be extended greatly.