Abstract
Both compliance and discontinuity are the common characteristics of the real ground surface. This paper proposes a stabilization method for the underactuated bipedal locomotion on the discontinuous compliant ground. Unlike a totally new control method, the method is actually a high-level control strategy developed based on an existing low-level controller meant for the continuous compliant ground. As a result, although the ground environment is more complex, the calculation cost for the robot walking control system is not increased. With the high-level control strategy, the robot is able to adjust its step-length and velocity simultaneously to stride over the discontinuous areas on the compliant ground surface. The effectiveness of the developed method is validated with a numerical simulation and a physical experiment.
Highlights
Underactuated bipedal walking has attracted increasing attention due to the low energy-consumption characteristic [1,2,3,4]
A nominal gait should be preplanned by considering the actual unevenness of the terrain around the robot, and the bipedal locomotion can be stabilized by finding a control strategy to force each joint position always converging the gait. is method has been used prevalently to realize a stable bipedal locomotion on the rigid uneven ground [12, 13]
A high-level control strategy is proposed to stabilize an underactuated bipedal walking on the discontinuous compliant ground. e main contribution of this work is the strategy being developed from the features of an adaptive feedforward controller (AFC) which was designed for the locomotion on a continuous compliant ground mentioned in [23] but not from a fresh start
Summary
Underactuated bipedal walking has attracted increasing attention due to the low energy-consumption characteristic [1,2,3,4]. In the early research studies, the ground is assumed to be rigid, and the robot-ground impact is modelled as the rigid body collisions of kinematic chains with an external surface [10, 11] With this assumption, a nominal gait should be preplanned by considering the actual unevenness of the terrain around the robot, and the bipedal locomotion can be stabilized by finding a control strategy to force each joint position always converging the gait. Yang et al applied a reinforcement learning method to supervise the stride-frequency and find out the reasonable step-length online for bipedal walking [29] Since these methods are not designed for walking on the compliant ground, they are incapable of coping with the effects of ground compliance and discontinuity simultaneously. A high-level control strategy is proposed to stabilize an underactuated bipedal walking on the discontinuous compliant ground.
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