Compact and Optimized Optical Six-Axis Force/Torque Sensor for Legged Robots

This study introduces a novel compact and lightweight six-axis force/torque sensor designed for legged robots. In contrast to conventional strain-gauge-based sensors, the innovative sensor utilizes a non-contact measurement method that employs photocouplers. This unique approach enhances the sensor’s resistance to physical impacts, thereby reducing the risk of damage. This design enhances durability, streamlines manufacturing processes, and reduces costs. Because force/torque sensors in legged robots must withstand impact forces that exceed typical ground reaction forces by over threefold, conventional designs often encounter structural limitations. While expanding the sensing range could potentially mitigate sensor failure, it inevitably compromises sensitivity. To address this trade-off, this study introduces an optimization-based design approach that maximizes sensitivity while minimizing error. Through precise modeling and objective function analysis, optimal design parameters were identified and validated through integration and testing on a quadruped robot. The results of these tests closely align with theoretical predictions, validating the sensor’s ability to accurately measure forces in dynamic environments. Beyond foot-ground interaction analysis, the proposed sensor opens up possibilities for broader use in robotic systems, thereby contributing to advancements in both robotics and sensor technology.