Research On The Structure And The Contorl Strategy Of Variable Impedence Cheetah Leg For Highly Speed Locomotion

With the thorough research of quadruped robots, the quickness and flexibility have become a focus recently. Especially since the Cheetah from Boston Dynamics and the Cheetah from MIT came out and shocked the world, the quadruped robots’ rapidity became the most challenge research topic in the robotics field. Studies have shown that the natural frequency of the legs is the most crucial key to achieve high speed locomotion. The leg’s natural frequency can be changed with different impedance of the leg, which could improve the locomotion speed.This paper chooses cheetah as the bionic object and presents an active compliance control approach based on impedance control, on the basis of the morphology and the bio-dynamics. A variable impedance cheetah leg prototype is established using hydraulic. According the cheetah’s physiological structure, the joints and the structural dimension can be acquired. Besides, the mathematical model, the kinematics and the dynamics equations are established. Comparing with traditional quadruped robots, the superiority in calculating and controlling is analyzed.To achieving high speed locomotion, this paper analyzed the key factors basing on the SLIP model and came out that the impedance has great effect on the velocity. Through the force based impedance control, the articulated leg is equivalent to a virtual SLIP model. Then using the active torque control, the articulated legs’ velocity has been increased rapidly. All the control methods could offer a new method for multi-joints quadruped robots for highly speed locomotion.Through a serious of simulation, the hydraulic drivers are selected and the structural dimensions are optimized, having the robotics’ structure and control method tested. Based on those, the variable impedance articulated leg experimental platform are established including the leg prototype, the sensor system and the velocity testing platform. A serious of experiments including the hopping, the constant speed running, and variable speed running experiments have been conducted and tested the rationality of the structure and the feasibility of the control method basing on active compliance.