Design and characterization of a PCB based capacitive shear force sensor for robotic gripper application

The shear force sensor is one of the key elements in future robotic industries; it is of great importance in applications where robotic arms are required to delicately interact with objects to be handled. This paper presents the development of a capacitive shear force capable of sensing shear forces in two degrees of freedom. The fabrication of the sensor is based on the PCB fabrication process, a well-known and mature technology. We adopt the capacitance sensing scheme for its high sensitivity and easy implementation. For sensor characterization, we used a force gauge and an optical interferometer to measure sensor's parameters including its sensitivity and resolution. The dimension of our prototype shear force sensor including the metal housing is 26 mm × 13 mm × 58 mm suitable for the integration with commercial robotic grippers. For sensor performance, we achieved a shear force sensitivity of 126 fF/N and a resolution of smaller than 6 mN.