Publication

Abstract : Joint torque sensors are widely used in robots for collision detection and continuous monitoring of the joint torque during path planning, manipulation, and tool operation. There is a strong demand for such sensors that ensure efficient collision detection and safe operation by virtue of their responsive sensitivity, overload capacity, and avoidance of resonance. This research investigated a highly sensitive strain gauge-based joint torque sensor design, with a novel pear-shaped hole on its spoke structure. A safety factor of 4 was assumed during the design phase to secure the high overload capacity of the sensor structure. The proffered sensor was designed for robotic applications involving high-frequency vibrations, with minimal risk of achieving mechanical resonance. Finite element method optimization was carried out to maximize the sensitivity, precluding resonance. An instrumentation amplifier-based sensor-mountable data acquisition unit was also designed and fabricated to acquire the amplified strain gauge data. The experimental results showed that the proposed sensor has 38 mV/Nm sensitivity and 0.04 Nm resolution in the measurement range of ±25 Nm torque. The sensor resolution and sensitivity were shown to be 60% and 26.78% better than extant sensors, respectively. The reduction in strain over the sensing area along the length of the spoke structure was constrained to 5.42%, which secured uniform strain distribution under strain gauges, for enhanced sensitivity. The proposed methodology can very well be applied to design sensors with maximum sensitivity for the prescribed vibration constraints.