Libo Meng

Gait Planning of Omnidirectional Walk on Inclined Ground for Biped Robots

When a biped robot moves about in a physical environment, it may encounter inclined ground. Biped walking on inclined ground still remains challenging for biped robots. Previous studies have discussed biped walking on inclined ground along specific directions. However, omnidirectional walk on inclined ground has rarely been investigated. In this paper, we propose a gait pattern generation method for omnidirectional biped walking on inclined ground. First, a model that describes the motion of biped walking on inclined ground uniformly with two angle parameters is proposed. A mathematical relationship between motions in the sagittal and coronal planes of the biped robot are presented. Then, based on nonorthogonal motion decoupling, a method that generates gait patterns for omnidirectional walking with a double support phase for biped robots is proposed. The trajectories of each foot are designated by the walking speed, step length, and walking direction. The motion trajectory of the center of mass (CoM) of the robot is planned using a linear inverted pendulum model in the sagittal and coronal planes. The motion of CoM in the sagittal and coronal planes is constrained in parallel to the gradient vector of the inclined ground and the horizontal plane, respectively. Finally, the effectiveness of the proposed gait planning method for biped walking on is validated by simulations and experiments with an actual biped robot.

Design of a humanoid ping-pong player robot with redundant joints

This study investigates the design of a humanoid ping-pong robot system with a 7-DOFs redundant arm. The design of the arm mechanism, real-time binocular vision system, and a distributed control structure was presented. The methods for ball trajectory prediction and motion planning for the ping-pong racket were proposed. A Jacobian pseudoinverse method considering joint limits and manipulability optimization terms is employed to solve inverse kinematics in order to decrease the counterforce exerting on the humanoid robot. The proposed system is validated by a series of rally experiments between the robot and a human.

A falling motion control of humanoid robots based on biomechanical evaluation of falling down of humans

This paper presents results of experimental investigation of the falling down of human body in order to identify significant characteristics and parameters that help for safe similar situations with humanoid robots. Experiments are discussed with results from lab tests that give both behavior and values of the biomechanics of falling down of human body. Simulations of humanoid robot falling verified the strategies concluded from the human falling down.

Bipedal walking with toe-off, heel-strike and compliance with external disturbances

Both disturbance rejection and human-like motions, like toe-off and heel-strike, are important for a biped robot to enhance its performance. However, the required motions for them may influence each other, which is why few studies consider them simultaneously. This paper presents a method to realize stable walking with toe-off and heel-strike even when the robot experiences disturbances. We propose a walking controller which can constrain the desired ground reaction force. On the one hand, the controller can adjust the torso acceleration to make the supporting leg compliant with the external disturbances on the torso. On the other hand, it can rotate the supporting foot by adjusting the ZMP to an appropriate location. The linear inverted pendulum is utilized to generate the CoM trajectory and the foot placement. Meanwhile, its ZMP can be predefined as required so that the toe-off and heel-strike can be achieved by the controller. The effectiveness of the proposed method is demonstrated by simulations.

Human-like walking patterns with pelvic rotation for a humanoid robot

Fast and stable walking is one of the important prerequisite for humanoid robots to serve the people. Pelvic rotations play a significant role when one walks fast. This paper proposes a method to generate human-like walking patterns with pelvic rotation in the transverse plane for a humanoid robot to effectively improve its quickness and stability. First, the regularities of pelvic rotation in the transverse plane during human walking are studied. Second, the mechanism design of a humanoid robot waist for pelvic rotations is presented. Then, a walking trajectory planning with pelvic rotation to improve the stability margin is proposed. Finally, the effectiveness of the method is demonstrated through simulations and experiments on BHR-5.

Hand-eye servo and flexible control of an anthropomorphic arm

One key technology for a humanoid robot is to sense the environment accurately and control the movement of the robot in realtime. This paper addresses this problem and focuses on the visual servoing control of an anthropomorphic robotic arm. A high precision, image-based visual servo algorithm for an eye-in-hand visual system is proposed to control the movement of the anthropomorphic arm. The control objective of the controller is to lock all the feature points at fixed points on the image plane. Then, impedance control law is implemented to keep the flexible of the arm. Finally, the effectiveness of the proposed methods are verified by experiments on our humanoid robotic arm platform.

Disturbance Rejection Controller for Biped Walking Using Real-Time ZMP Regulation

This paper proposes a disturbance rejection controller using real-time ZMP (Zero Moment Point) regulation which could maintain the stable walk of a humanoid robot when the robot is subjected to external disturbances. The controller detects the disturbance by an accelerometer, and computes the ZMP increment to overcome disturbance to ensure stability, and then calculate the increment of trajectory of center of mass according to ZMP increment using preview control. The effectiveness of our proposed method was confirmed by simulation in ADAMS and walking experiment on an actual humanoid robot, BHR-5.

A universal pattern generator for biped walking on 3D slopes

Uneven terrain walking is one of the important premises for biped robots to serve people. However, it is one of the key challenges for biped robots walking on a slope. In this paper, a universal method to generate patterns for biped robot walking on a three-dimensional (3D) slope is proposed. Different from most researches, which only focused on the specific walking directions on a slope as across or along a slope, the proposed method is applied to biped robots for all directions walking on a slope. First, unification of parameters for biped walking on a 3D slope is designed. Second, walking patterns based on dual linear inverted pendulum method (DLLIPM) on a 3D slope are generated. Finally, the effectiveness of the universal pattern generator is verified through simulations.

A Falling Motion Strategy for Humanoids Based on Motion Primitives of Human Falling

In this paper, a falling motion planning for humanoid robots is proposed as inspired from human falling in order to decrease the impact force significantly. Firstly, motion data of human falling are obtained from a motion track system. Then, two falling motion primitives, namely, knee bending with stretching and hip bending with stretching are identified from human falling tests. A motion strategy is used to combine the falling motion primitives in motion strategy for humanoid falling in order to minimize the impact effects. Simulations and experiments with a humanoid robot have verified the proposed falling motion strategy.

Rolling motion generation of multi-points contact for a humanoid robot

The posture of a humanoid robot needs to be changed from lying state to others in order to complete required missions. With the rolling motion, it is possible for a humanoid robot to change lying state and adapt itself to the environmental uncertainties. The study of rolling motion for humanoid robots is fairly rare. This paper proposed a highly dynamic whole-body rolling motion. The planned rolling motion trajectories were based on the motion of human rolling, and meet the constraints of dynamic stability and multi-points contact conditions. The trajectory of the center of mass (CoM) and environmental constraints were calculated by dividing whole-body motion into upper and lower body movement. The effectiveness of proposed method was confirmed by dynamic simulation on a virtual humanoid robot.