Compliance Control of the HydraulicDriven Single Legged Robot This paper presents the force control strategies and a kind of compliance control strategies of the hydraulic driven unit (HDU) in the legged robots. The model of HDU is established and the transfer function of the HDU force control system is given. The analysis of the force control strategies is introduced according to the characteristic of the HDU system. Based on the force control strategy called velocity feedback control strategy which performs the best, the virtual model control strategy which is a kind of compliance control strategy is presented to enhance the adaptability of the legged robot. Finally, the experiments are taken on the HDU experiment platform to test the performance of the force control strategies and the compliance control strategy. The landing buffer experiments are taken on the single leg robot to verify the effectiveness of the compliance control strategy. In the landing buffer experiments, the impact force of the single leg robotu0027s knee HDU is about 0.33 time of what it is without the compliance control strategy while landing.

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.