Design and analysis of an adjustable Stephenson-III closed-chain leg mechanism and its application in multi-legged robot

To improve the insufficient adaptability of single degree-of-freedom (DOF) closed-chain legs to unknown surroundings, this paper studies a novel adjustable closed-chain leg mechanism. Based on the traditional six-bar Stephenson-III leg mechanism, we add one degree-of-freedom to realize the adjustment of frame rod position, by which different shapes of foot trajectory curves are obtained. The height of the foot trajectory can be adjusted longitudinally to enhance the obstacle-surmounting ability, and the length of the walking stride can be changed in the transverse direction to achieve the landing point placement of the swing leg. The structure optimization, gait analysis and obstacle-surmounting simulation in different scenarios are carried out. The test results of walking ability and obstacle surmounting performance in specific surrounding show that the designed closed-chain leg mechanism can increase the maximum obstacle-crossing height and walking stability, which proves the promising characteristics of the proposed leg mechanism in the application of multi-legged robots.