Miniature capacitive three-axis force sensor

Interest in low-cost force-torque sensors with high performance will continue to increase in the next years, as robot control needs to rely on more sensors to move into the human environment. Existing force-torque sensors still suffer from some shortcomings such as noise sensitivity, low resolution and high cost. This limits their use in some emerging applications. Through an advanced systematic design method based on a symbolic formulation of the wrench-displacement relationship, we designed compact and cost-effective three-axis capacitance-based force sensor. Despite its relative simplicity, our sensor exhibits a very good sensitivity thanks to the electronic components selected, but also to a special soft silicone layer filled with nanoparticles of ferroelectric ceramic. This composite we made has a relatively high dielectric constant. This paper presents the design process that led to the sensor including the structure, the capacitance measurement circuit and the fabrication of the soft dielectric. Characterization tests have also been carried out on a prototype of the sensor and the results show that it is sensitive and easy to fabricate.