A foot force sensing approach for a legged walking robot using the motor current

A quadruped walking robot with the large payload capability is developed for the rescue purpose. To enhance the payload capability, the leg is designed by using the parallel mechanism. To simplify the actuation system, the actuators are selected as electric motors. Foot force is very important for the gait planning and stability control. Traditional foot force sensors are often easy to corrupt due to the strong impact from the ground. In this study, the indirect foot force sensing method is proposed, where the foot force is estimated from the motor current based on the dynamics model. To improve the accuracy of the dynamics model, an improved dynamics model is established to compensate unknown parameters and frictions by using the system identification technique. Because additional foot force or joint torque sensors are not required, the size and weight of the robot do not increase. The effectiveness of the proposed method is verified by the experiments.