Joint Torque Estimation for Dynamic Jumping Control of Compliant GearDriven Legged Robot * This paper is to explain compliant torque control for gear driven legged robot. In this paper, active torque compliance control is realized without torque sensor or any mechanically elastic component. The joint torque estimation is very important for torque control. However, Joint torque sensor for mediumsize legged robot is so large and heavy that it increases the inertia of the leg, slows down the dynamic response, and leads to complicated electrical system. Therefore, we only use the encoder information and the motor current to estimate the joint torque without torque sensors. Compliant torque control have advantages of absorbing impacts and saving energy. But, torque control is difficult to guarantee the position precision, because the accurate model of the robot is hard to obtain. In order to ensure both compliance and position accuracy, hybrid torque and position control is applied to our robot. In the jumping motion experiments, it is verified that the joint torque can reach peck value in 4.75 ms when jumping up. While The landing peak torque in hybrid control is lower than 16 of that under position control and 12 of that in torque control. This indicates that the compliance torque control can absorb a large part of shock.

Joint Torque Estimation toward Dynamic and Compliant Control for GearDriven Torque Sensorless Quadruped Robot This paper investigates dynamic and compliant control based on joint output torque estimation for electrically actuated quadruped robots with largereductionratio harmonic gear. Compared with position control, force control exhibits better performance of dynamics and compliance for the robotxe2x80x99s interactions with complex environments. However, force control without direct feedbacks from torque sensors may come with poor tracking performance of joint compliance when the robot equipped with gears of high reduction. To solve this problem, we propose a new method to estimate joint torque from motor current and rotation velocity detected on each joint, using a more precise friction model of the harmonic gear. We also introduce a prestance phase to the whole cycle of leg alternating swingstance based on hybrid force and position control to dynamically absorb feet impacts on the ground. Our controller performance is validated by standing experiment and walking experiment.