Abstract
Knee-stretched walking is considered to be a human-like and energy-efficient gait. The strategy of extending legs to obtain vertical center of mass trajectory is commonly used to avoid the problem of singularities in knee-stretched gait generation. However, knee-stretched gait generation utilizing this strategy with toe-off and heel-strike has kinematics conflicts at transition moments between single support and double support phases. In this article, a knee-stretched walking generation with toe-off and heel-strike for the position-controlled humanoid robot has been proposed. The position constraints of center of mass have been considered in the gait generation to avoid the kinematics conflicts based on model predictive control. The method has been verified in simulation and validated in experiment.
Highlights
Most biped walking studies use a knee-bent posture to avoid the problem of singularities
The same simplified dynamics model and similar state and input vectors as those used for the sagittal plane were selected for the knee-stretched walking in the lateral plane, the discrete system dynamics is given as follows xk 1⁄4 Axxk þ Bxuxk pxk 1⁄4 Cxxk where xk 1⁄4 1⁄2 xðkT Þ x_ðkT Þ x€ðkT Þ T, uxk 1⁄4 _€xðkT Þ, pxk 1⁄4 pxðkT Þ, xðkT Þ, and pxðkT Þ are the lateral positions of center of mass (CoM) and zero moment point (ZMP) at kT, respectively, Ax 1⁄4 Ay, Bx 1⁄4 By, and Cx 1⁄4 1⁄2 1 0 ÀhCoM=g
This article focused on realizing a knee-stretched walking with toe-off and heelstrike on a position-controlled humanoid robot
Summary
Most biped walking studies use a knee-bent posture to avoid the problem of singularities. The robot outlined in red is conducting the desired knee-stretched motion which is stable in the sagittal plane and the desired lateral CoM position with modification of vertical CoM position, of which the maximum length limitation of the leg is satisfied.
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