A New Foot Trajectory Planning Method for Legged Robots and Its Application in Hexapod Robots

Abstract

Compared with wheeled and tracked robots, legged robots have better movement ability and are more suitable for the exploration of unknown environments. In order to further improve the adaptability of legged robots to complex terrains such as slopes, obstacle environments, and so on, this paper makes a new design of the legged robot’s foot sensing structure that can successfully provide accurate feedback of the landing information. Based on this information, a new foot trajectory planning method named three-element trajectory determination method is proposed. For each leg in one movement period, the three elements are the start point in the support phase, the end point in the support phase, and the joint angle changes in the transfer phase where the first two elements are used to control the height, distance, and direction of the movement, and the third element is used make decisions during the lifting process of the leg. For the support phase, the trajectory is described in Cartesian space, and a spline of linear function with parabolic blends is used. For the transfer phase, the trajectory is described in joint-space, and the joint angle function is designed as the superposition of the joint angle reverse-chronological function and the interpolation function which is obtained based on joint angle changes. As an important legged robot, a hexapod robot that we designed by ourselves with triangle gait is chosen to test the proposed foot trajectory planning method. Experiments show that, while the foot’s landing information can be read and based on the three-element trajectory planning method, the hexapod robot can achieve stable movement even in very complex scenes. Although the experiments are performed on a hexapod robot, our method is applicable to all forms of legged robots.

Reactive Locomotion of a Hexapod for Navigation Across Irregular Ground

“…The reactive behavior comes with the contact detection module. Similarly, to the model presented by Xia et al [6], the robot locomotion in an irregular ground is adjusted according to the early detection of foot-forces. For this purpose, the system reads the values from the force sensors placed on each foot-tip to detect irregularities in the normal contact forces.…”

“…In this case, the perception of the foot-ground interaction is important to plan the actuation of its legs according to the terrain topology. Thereby, Xia et al [6] and Liu et al [5] resorted to force sensors placed on the feet to evaluate the normal contact forces and adjust the limbs trajectory. Both studies aim at detecting a variation of the contact forces to switch the actuation of the legs.…”

Development and implementation of a new approach for posture control of a hexapod robot to walk in irregular terrains

“…The advantage of the main body leveling method is not resorting to external sensors to estimate the hexapod state. Xia et al [40] proposed a body leveling method based on the detection of contact forces between the limbs. In a different approach, Chen et al [41] proposed a proportional control to adjust the hexapod posture based on the relation between the feet and the torso's linear and angular velocities.…”

Editorial for Special Issue “Automation and Robotics: Latest Achievements, Challenges and Prospects”

“…The second strongest group of published papers enhances the field of mechanization, automation and robotics focused on production technologies and mechanical engineering. The authors of this group of papers [5][6][7][8][9] combine results oriented to the design of the mechanical parts with the support of 3D adjustable simulations and other objects designed for kinematic data adaptation and positioning of industrial robots. The authors of these papers deal with advanced theoretical topics related to the statics and dynamics of action elements of robotic systems [10][11][12][13].…”