Whole-Body Motion Planning for a Six-Legged Robot Walking on Rugged Terrain

Abstract

Whole-body motion planning is a key ability for legged robots, which allows for the generation of terrain adaptive behaviors and thereby improved mobility in complex environment. To this end, this paper addresses the issue of terrain geometry based whole-body motion planning for a six-legged robot over a rugged terrain. The whole-body planning is decomposed into two sub-tasks: leg support and swing. For leg support planning, the target pose of the robot torso in a walking step is first found by maximizing the stability margin at the moment of support-swing transition and matching the orientation of the support polygon formed by target footholds. Then, the torso and thereby the leg support trajectories are generated using cubic spline interpolation and transferred into joint space through inverse kinematics. In terms of leg swing planning, the trajectories in a walking step are generated by solving an optimal problem that satisfies three constraints and a bioinspired objective function. The proposed whole-body motion planning strategies are implemented with a simulation and a real-world six-legged robot, and the results show that stable and collision-free motions can be produced for the robot over rugged terrains.

Design of Bionic Foot Inspired by the Anti-Slip Cushioning Mechanism of Yak Feet

“…From Equations ( 6) and ( 8), it can be seen that the impact time and z1, z2, and z3 were negatively correlated; the impact time with the reduction in the three spring parameters increases, and the finger occipital-hoof ball spring stiffness had the greatest effect on the impact time, followed by the flexor tendon spring stiffness, and the extensor tendon spring stiffness had the least effect, indicating that the foot sole and the ground at 0 • and −5 • for the impact of the finger occiput-hoof ball structure played a major buffering effect. From Equation (7), we can see that the rule of change is similar to that of 0 • and −5 • , the stiffness of the extensor tendon spring and the stiffness of the phalanx-soleus spring had a large effect on the impact time, and the degree of effect was not much different, indicating that the extensor tendon spring and the phalanx-soleus spring both played a cushioning effect when the sole of the foot and the ground were impacted at a 5 • angle.…”

“…The regression equation for natural space could be obtained in the same way when the sole of the foot is at 5 • to the ground: ŷ = 0.05492 − 7.1 × 10 −5 z 1 − 6.934 × 10 −5 z 2 − 3.2 × 10 −5 z 3 (7) When the sole of the foot was at −5…”

“…Legged robots have received much attention in the past few years due to their excellent performance in complex environments [1][2][3]. And the foot structure is one of the important factors affecting the walking performance of quadruped robots [4][5][6][7][8]. The foot mainly plays the role of cushioning and support, and exhibits unique functions and properties during robot activities, which need to be adapted to different types of ground.…”

Optimization of Motion Planning and Control for Automatic Machines, Robots and Multibody Systems

“…Among mobile robots, legged robots are attracting interest in the scientific community, and therefore have been included in this book. In [13], the whole-body motion planning of a six-legged robot over rugged terrain is discussed. Motion planning is decomposed into support motion (aimed at stability maximization and orientation matching) and swing motion.…”

Model and Fuzzy Controller Design Approaches for Stability of Modern Robot Manipulators

“…Stability is a fundamental aspect that underlies the efficient motion of a robot. In order to ensure a sufficient stability margin, a necessary condition in modern robotics is the presence of a link connecting various components [1,2]. The crucial factors to consider for stability in robots are their mass, length, and force [3].…”