Leg Trajectory Planning for Quadruped Robots with High-Speed Trot Gait

Abstract

In this paper, a single leg platform for quadruped robots is designed based on the motivation of high-speed locomotion. The leg is designed for lightweight and low inertia with a structure of three joints by imitating quadruped animals. Because high acceleration and extensive loadings will be involved on the legs during the high-speed locomotion, the trade-off between the leg mass and strength is specifically designed and evaluated with the finite element analysis. Moreover, quadruped animals usually increase stride frequency and decrease contact time as the locomotion speed increases, while maintaining the swing duration during trot gait. Inspired by this phenomenon, the foot-end trajectory for quadruped robots with a high-speed trot gait is proposed. The gait trajectory is planned for swing and stance phase; thus the robot can keep its stability with adjustable trajectories while following a specific gait pattern. Especially for the swing phase, the proposed trajectory can minimize the maximum acceleration of legs and ensure the continuity of position, speed, and acceleration. Then, based on the kinematics analysis, the proposed trajectory is compared with the trajectory of Bézier curve for the power consumption. Finally, a simulation with Webots software is carried out for verifying the motion stability with two trajectory planning schemes respectively. Moreover, a motion capture device is used for evaluating the tracking accuracy of two schemes for obtaining an optimal gait trajectory suitable for high-speed trot gait.

Leg Locomotion Adaption for Quadruped Robots with Ground Compliance Estimation

“…The detailed leg design with three-joint leg structure can be found in our previous research [ 5 ]. The overall of the control diagram is shown in Figure 1 .…”

“…MIT Cheetah was designed with proprioceptive actuator for impact mitigation and high-bandwidth physical interaction [ 4 ]. In our previous research, inspired by the proprioceptive actuator [ 5 ], we designed a single-leg platform for high-speed locomotion. ANYmal used the complicated actuator which makes the robot impact with high torque control accuracy [ 6 ].…”

Attitude Trajectory Optimization to Ensure Balance Hexapod Locomotion

“…S P Six = B Si P Six + l ix S P Siy = B Si P Siy + l iy S P Siz = B Si P Siz + l iz (32) where S P Si = S P Six , S P Siy , S P Siz T represents the hypothetical foot position vector of leg i in the slope coordinate S when the robot is standing still on the slope. To maintain as high stability as possible at any time during walking, S P Si should be kept in the middle position of a step.…”

“…In addition, in most currently developed balance walking controllers, the influence of the swing leg motions on the body attitude adjustment process is not considered. In fact, for many currently developed legged robots, the trajectory of the swing leg is only designed with different shapes according to the desired motion state of the robot in the robot body coordinate without considering the terrain attitude angles, namely the yaw, pitch, and roll angles of the terrain [12,[32][33][34]. For a legged robot walking on flat terrain, this swing leg trajectory design is easy to be carried out and won't cause any trouble to the walking performance.…”

Advances in Mechanical Systems Dynamics

“…In Reference [5], a single leg platform for quadruped robots is designed in order to achieve high-speed locomotion. For this purpose, the foot-end trajectory for quadruped robots with a high-speed trot gait is proposed.…”