Weida Li

Analysis and experiment of stick-slip motion principle in a legged microrobot

To solve the contradiction between high speed with high resolution for micro robot, a legged micro robot based on dual locomotion principles is presented. The dual locomotion principles include stick-slip principle in non-resonant condition and impact principle in resonant condition, which are respectively for high resolution and high velocity. Stick-slip principle is discussed mainly in this paper. Firstly, its driving process is divided into sticky phase and slip phase, in which static analysis and transient dynamic analysis is preceded respectively. Secondly, the relation between mechanisms vibration with friction force is analyzed by using numerical simulation method. And then the stick-slip principle is revealed based by micro robot. A legged micro robot prototype is developed, whose dimension is 70mm×35mm×15mm and weight is about 3g. Experimental results show that the locomotion resolution of the prototype reaches 0.896 mm in forward direction when driving voltage is 10V. And the changing trend of resolution with voltage is consistent with theoretic analysis, which approves the validity of the analysis.

Adjustment of Intention to Start a Motion of Lower Limbs Based on Cerebral Hemoglobin Information

To increase intelligence of walking-assisted devices, it is important to provide a start command of action based on the motion intention of subjects. In this paper, a method for identifying motion intention was proposed based on cerebral hemoglobin information. Spontaneous movements (upstairs, downstairs, upslope, down-slope, sit-down, squat, and the corresponding standup) without an advanced imagination or external stimuli were performed on two subjects. During the experiment, cerebral hemoglobin information was recorded by applying near-infrared spectroscopic technology. Multiple analyses of variance on different features of the variation of total hemoglobin were combined and a series of significant levels were set. The corresponding precision rate was up to 74.8%, and the sensitivity was up to 79.2%. Since the proposed identification method is realized based on the brain information recorded in a real movement environment, it is helpful and practical to enhance intelligence of walking-assisted devices.

Dynamic analysis and optimization for the ankle joint prosthesis

Nowadays, a comfortable ankle prosthesis with natural walking gait for the amputee has become an important requisite. In this paper, a new kind of active ankle prosthesis is presented, which can not only help amputees walk naturally, but also reduce energy consumption by recycling. Firstly, the structure of ankle prosthesis was proposed. And then, dynamic simulation and structure parameters optimization for the prosthesis were carried out in Adams software environment. Finally, energy consumption in a gait cycle was calculated based on the dynamic simulation. We conclude that our ankle joint prosthesis can greatly reduce the energy consumption.

Structure design and analysis of compliant human-machine interface mechanism for exoskeletons

Due to the difference between kinematics of human joints and exoskeleton joints, joint misalignment may be brought about by human-machine interface (HMI). Joint misalignment may lead to undesired interaction forces, if not copped with properly, e.g. in the HMI mechanism with straps. In this paper, firstly the interaction forces caused by joint misalignment in HMI mechanism with straps are studied. Then, a compliant HMI mechanism which consists of passive mechanical linkages is presented and Degrees of Freedom (DOFs) of the whole human-machine system are analyzed. A simulation model of human-machine system is established for analyzing the interaction forces in the compliant HMI mechanism. Finally, comparative results were obtained to demonstrate that the constraint forces can be decreased greatly with sufficient driving forces simultaneously by using of the compliant HMI mechanism.

A NOVEL RESONANT LOCOMOTION PRINCIPLE BASED ON IMPACT FORCE FOR MINIATURE MOBILE ROBOT

For their small size, good mobility and energy saving, miniature mobile robots have possibility application in many domains, but it is hard for traditional locomotion mechanisms to fit miniature robot well because of their complex structures. To solve this problem, a kind of resonant locomotion principle based on impact force is proposed and analyzed through numerical simulation of the vibro-impact system model. And then, a prototype locomotion mechanism and an energetically autonomous robot actuated by piezoelectric bimorphs are developed and tested. Experiment results show that the mechanism can achieve locomotion velocity as high as 280mm/s with the 10V excitation voltage, and can also generate motion about 16mm/s with excitation voltage as low as only 1V.