Huaxin Liu

Integral Acceleration Generation for Slip Avoidance in a Planar Humanoid Robot

Slip occurrence puts not only the humans but also the humanoid robots into dangerous situations. Although the detection and the estimation of slip have been well researched, studies on slip avoidance control in a humanoid robot are rare. Previous methods used to restrict the horizontal motion or regulate the vertical motion of the humanoid robot did not take the important rotational motion into account. This study proposes an integral acceleration generation method for slip avoidance that meets the real-time requirements, using the sagittal plane as an example. The proposed method makes full use of all the motions related to the slip in the sagittal plane to prevent the slip, including the translational and the rotational motions. The simulations and experiments on the physical humanoid robot demonstrate the effectiveness of the presented method.

Trot pattern generation for quadruped robot based on the ZMP stability margin

Quadruped robot is expected to serve in complex conditions such as mountain road, grassland, etc., therefore we desire a walking pattern generation that can guarantee both the speed and the stability of the quadruped robot. In order to solve this problem, this paper focuses on the stability for the tort pattern and proposes trot pattern generation for quadruped robot on the basis of ZMP stability margin. The foot trajectory is first designed based on the work space limitation. Then the ZMP and stability margin is computed to achieve the optimal trajectory of the midpoint of the hip joint of the robot. The angles of each joint are finally obtained through the inverse kinematics calculation. Finally, the effectiveness of the proposed method is demonstrated by the results from the simulation and the experiment on the quadruped robot in BIT.

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.

Obstacle avoidance research of snake-like robot based on multi-sensor information fusion

The snake-like robot needs to adapt to complex environment, in order to reach the target point safely and collisionless, necessary obstacle avoidance strategy is of vital importance. In this paper, laser radar and ultrasonic sensors are used to detect the surrounding environment, and then information fusion method based on TS fuzzy neural network is adopted to integrate the collected information, which provides the necessary condition for obstacle avoidance research of the snake-like robot. Experiments show that the snake-like robot can successfully avoid obstacles to reach the target point after training of the fuzzy neural network.

Passive buffering arm for a humanoid robot against falling damage

Humanoid robot is anticipated to serve people in the near future. However, a humanoid robot encounters a high risk of falling when walking or operating in an uncertain environment. In this paper, we propose a passive buffering arm to reduce damage for humanoid robot during falling forward, and we develop a robotic prototype which has a simplified humanoid robot shape and can emulate motions in the sagittal plane for falling forward. Through the analysis of experimental data, we know the magnitude of the impact force and impact torque in robot arm during falling forward, and we conclude that the optimal elasticity and damping for buffer components.

A Cable-Pulley Transmission for Ankle Joint Actuation in Artificial Leg

In this paper a cable-pulley transmission is proposed as the angular actuation system in ankle joints of artificial legs with human-scale design. The ankle articular characteristics in human and robotic ankles are discussed toward a proper design solution for efficient and accurate operation in coordination with leg motion. A flow chart of a design procedure is introduced for mechatronic iterative optimal design. A mechanical design is elaborated for ankle angular pitch DOF and it is used for dynamic simulation in ADAMS environment. Simulation results are discussed to characterize both the performance and feasibility of the proposed design. A simulated validation is reported as an approximate operating solution of human-walking in order to show the main advantages of the proposed design in possible humanoid robot implementations.

A torque limiter for safe joint applied to humanoid robots against falling damage

Humanoid robot is anticipated to serve people in our daily life in the near future. However, the great cost of falling damage needs to be addressed before it is widely used. In this paper, a safe and compact joint with torque limiter is developed to reduce the damage to a humanoid robot during falling. First, the overall scheme design and working principles of the safe joint are investigated. Then, the mechanical design of the safe joint is presented in details. Finally, the effectiveness of the safe joint is verified by several simulations.

Method of Design Optimization and Trajectory Implementation on a Small Cat-Like Robot

In the field of robotics, small cat-like robots, due to its small size, good flexibility, low energy consumption, has become a research trend. Elastic four-bar linkage mechanism (EFLM) with programmable trajectory, good stability, and certain buffer performance, is an excellent choice for driver design of small quadruped robot. We designed a novel miniature cat-like robot, Og-cat, which is optimized in structural features and special parameters compared with other similar quadruped robots. Moreover, we developed a method that can make leg trajectory implement accurately for robots using EFLM. A trajectory realization function is obtained through MATLAB fitting so that the trajectory can be executed precisely. The proposed method has been confirmed on our small quadruped robot Og-cat.

Falling protective method for humanoid robots using arm compliance to reduce damage

A falling protective method is proposed to reduce the damage during falling forward for humanoid robots. We develop a humanoid robot equipped with two flexible arms. The flexible arms make up the mechanical protection during falling down. The falling protective method consists of three parts: fall detection, leg crouch, and arm compliance control. Arm compliance control is applied to protect the robot from being severely damaged. Simulations have been achieved using the compliance control. The falling protective method is validated.

Mechanical design of the legs of hydraulically actuated quadruped bionic robot

This paper discusses the design of the mechanical structure of a quadruped robot and a three-dimensional simulation model is built under Adams simulating the mechanisms motion to capture the dynamic characteristics of the quadruped robot. This paper analyses the effect of the length of legs on the walking structure from different aspects: its movement speed, capability of climbing obstacles and the workspace of its foot end. In addition, to achieve the optimization target of balancing the output force of each hydraulic cylinder, the paper establishes a mathematical model under required constraints working out the lever members that accommodated with the structure. Synthesizing all these factors, the most satisfied structural parameters of the autonomous quadruped robot are selected.