Abstract
Inspired by biological systems, we seek to achieve natural dynamics and versatile locomotion for hopping or running robots by installing a series elastic actuator (SEA) in the joints due to its compliant property, passive adaptability and energy storage. However, robots equipped with these actuators have drawbacks in terms of substantial delay and limited bandwidth in their position control, especially when a robot has to choose its foothold while it is running at a demanding speed. To solve these problems, compliance control and adaptive position/torque control are introduced to a hopping- legged robot in this paper. The compliant performance of the robot can be improved through the intrinsic property of an SEA with a torque control algorithm. Combining the kinetics model and stochastic model of a 2-DOF robot, an adaptive position control with Kalman Filtering (KF) is developed to provide rapid convergent state estimation of the load on the robotic end-effector by solving the inverse dynamics. Validating the robustness and effectiveness of the proposed algorithm on our hopping-legged robot Tigger, the experimental results show very good position-tracking and disturbance-rejection, as well as flexible interactions while operating in a complex environment.
Highlights
In order to study and understand the principles of human and animal locomotion, lots of legged systems have been developed in the last twenty years
We extended the principle of high compliance actuators, including non-linear spring and damping characteristics, as well as sophisticated low-level control to enable high fidelity torque control and precise position control
By increasing the update rate greatly, the adaptive feedforward control term will get closer to the real dynamics of an series elastic actuator (SEA)-based robot in a shorter time, in order to satisfy the purpose of control
Summary
In order to study and understand the principles of human and animal locomotion, lots of legged systems have been developed in the last twenty years. These robots can be separated into two classes [1]. The other class of legged systems relates to those equipped with a force or torque sensor, such that a joint or the structure allows the robot to exploit natural locomotion with compliant control. We extended the principle of high compliance actuators, including non-linear spring and damping characteristics, as well as sophisticated low-level control to enable high fidelity torque control and precise position control.
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