A Parallel-Beam MEMS Six-Axis Force/Torque Sensor with High Sensitivity, Low Crosstalk, and Packaging for Large-Range Applications

This paper presents a piezoresistive parallel-beam MEMS six-axis force/torque sensor with high sensitivity and low crosstalk. The novel parallel-beam design divides each cross-beam segment into three parallel beams, which can separate force and torque-sensing piezoresistors, thereby reducing the inter-dimensional crosstalk, and the sensitivities are improved due to the narrowed width of each beam. The parallel strain beams were released by combining the back and front DRIE processes. The proposed sensor chip achieves shear force (Fx/Fy) and normal force (Fz) sensitivities of$12.86 \text{mV} / \mathrm{N}, 11.44 \text{mV} / \mathrm{N}$, and$54.36 \text{mV} / \mathrm{N}$, torque Mx, My and Mz sensitivities of$131.95 \text{mV} / \mathrm{N} \cdot \text{mm}, \quad 128.06 \text{mV} / \mathrm{N} \cdot \text{mm}$, and 12.67$\text{mV} / \mathrm{N} \cdot \text{mm}$, respectively, with an inter-dimensional crosstalk of less than 5%. The sensing ranges of the sensor chip are 1.07 N and$1.95 \mathrm{N} \cdot \text{mm}$for Fz and Mz. Through a high-precision metal-based packaging method, the sensing ranges of Fz and Mz were expanded to over 100 N and$2500 \mathrm{N} \cdot \text{mm}$with minimum detectable force and torque of 12 mN and$7.8 \mathrm{N} \cdot \text{mm}$, respectively. By mounting the packaged sensor and a commercial six-axis force/torque sensor together on the wrist of a dexterous hand, the output of the sensor showed a high consistency with the commercial sensor under the same load interactions with the dexterous hand.