Foot-end Trajectory Analysis Based on a Novel Reconfigurable Leg Mechanism

A novel reconfigurable leg mechanism is proposed for the problem of inadequate ground adaptability of the robot, which is essentially caused by the fixed foot-end trajectory of the single-degree-of-freedom leg mechanism. To address this issue, the multi-linkage Jansen mechanism is used as the basis of the configuration, and the telescopic degree-of-freedom of specific rods are increased to realize the adjustment of the foot-end position. By means of this method, the consecutive variation of foot trajectory can be obtained, so that the height of the raised leg can be elevated in the longitudinal direction to enhance the ability to cross barriers. Also, the stride distance can be accurately varied in the lateral direction to achieve low energy consumption and high efficiency of continuous walking. The leg mechanism is driven by an electric motor during travel, which maintains its single-degree-of-freedom characteristics and has performance advantages in terms of fewer actuating motors, high structural stiffness, and large load capacity. The structural design of the reconfigurable leg mechanism, kinematic analysis, and trajectory adjustment are carried out. This paper involves the characteristic analysis of the foot-end trajectory cluster based on the kinematic model of this mechanism, and also proposes a method of motion analysis to seek the optimal variation process of the foot-end trajectory. A series of simulation experiments in Adams show that the trajectory adjustment can be successfully applied to the stair-climbing working conditions of mobile robots.