Yuwang Liu

The underactuation and motion-coupling in robotic fingers and two new 1-DOF motion-coupling anthropomorphic fingers

Present multifingered hands share a common drawback: the complexity of both the hardware and the software. The complexity is derived from tens of DOF and their actuators placed in small space, and results in the high weight and the non-reliability of the whole system. So many multifingered hands, especially the prosthetics and the hand developed for project application, adopt underactuation (in the finger or transmission system) or motion-coupling (in the finger) to reduce the number of actuators but not reduce the number of the DOF (underactuation) or the motion (motion-coupling), and accordingly debase the complexity of the multifingered hand. This paper firstly reviews the underactuation and motion-coupling used in existing anthropomorphic finger. And then based on the analysis of the existing motion-coupling anthropomorphic finger, we propose two new 1-DOF motion-coupling anthropomorphic fingers based on linkage. The two new proposed fingers are more compact than the existing 1-DOF fingers based on linkage. The feasibility of the two proposed fingers is validated in the end, and a 3D-CAD model of the anthropomorphic hand SIA-I with new-proposed fingers is given.

Kinematic feasibility analysis of 3-D multifingered grasp

The problem of determining whether a 3-D grasp is kinematically feasible is addressed in this paper. A unified computational framework for the kinematic feasibility analysis of grasps is proposed. In the study, we transform the detection of the feasibility of the grasp to the estimate of the relationship (contact, penetrate, and detach) between the exterior surfaces of the object and the hands elements (phalange and palm). The feasibility of a grasp then becomes equivalent to the estimate of the distance between the two section-lines in the same cross section. This allows us to cast the feasibility analysis conveniently as a problem of estimating the distance between two curves (or some points on the two curves) on a 2-D plane. Theoretically the object to be grasped can be any shape. An example is given to validate the method.

An optimal method to determine the parameters of anthropomorphic finger based on four-link mechanism

Anthropomorphic fingers based on four-link mechanisms are commonly used in the design of the dexterous robotic hands. The most critical part of the design is to determine a set of optimal linkage parameters that will provide the desired mechanical configuration and motion scope to match human fingerspsila. The existing optimization method is based on the vector kinematics equations of the linkages, which must apply the abstract constraints to ensure that the four-link mechanism is crossed. These constraints are non-intuitive to apply and may yield unsatisfactory results if applied improperly. This paper will propose an alternative approach, a geometry-based kinematics, to ensure the crossed four-link configuration without applying the abstract constraints. This paper will briefly review the vector kinematics based optimal method. Optimization using geometry-based kinematics will be introduced. Constraints and boundary conditions for the optimal parameters of the four-link mechanism will be discussed. An example is given to demonstrate the effectiveness of the proposed method to an anthropomorphic finger.

Rigid-flexible coupling dynamics analysis of a spot-welding robot

This paper studied a dynamics simulation analysis method for a rigid-flexible coupling system of spot-welding robot. The 6R spot-welding robot multi-body dynamics model is created by FEA (finite element analysis) and MBD (multi-body dynamics) software. Based on rigid-flexible coupling analysis method, we analyze mechanics characteristic of upper arm and get the deformation of end measuring point, maximum stress position and stress curve, when spot-welding robot is moving under loads. The analysis method is intuitional and accurate, and can increase the accuracy of dynamic response analysis of parts under the dynamic loads. The simulation results are very important theoretical basis for structure design and optimization of the spot-welding robot.

Vibration characteristic analysis of spot-welding robot based on ADAMS/Vibration

Aiming to improving the performance of high-power, heavy-load, high-speed and high-precision robots, this paper proposes a simulation method for vibration analysis based on virtual prototyping technology. In ADAMS/Vibration, we first establish the rigid-flexible coupling vibration system of a spot-welding robot, then solve the natural frequencies and modal shapes of the system, and finally calculate the frequency response under certain forced vibration. In order to build vibration system, the principle and simulation process of vibration analysis are given by inputting sine sweep signal on end effector. With the help of the getting frequency response, we can avoid the failure of damage due to the resonance vibration of the system and create the conditions for the optimal design and reliability research of a spot-welding robot.

Dynamic Analysis of a 165Kg Spot Welding Robot

A novel 165Kg spot welding robot is introduced, which is independently developed by China. The Newton-Euler approach is used to derive the dynamic equation. Then, entity model of the robot is built up with Solidworks software. The motion of the robot is planned by the position, velocity and acceleration of all the joint. The first three joints, which bear most of the payload and the own weight of the robot, are set with maximum acceleration during the accelerating/ decelerating process. According to the planned trajectory, dynamic simulation is carried out using Solidworks. The driving torques of each joint are obtained. From the dynamic analysis, we find the position yielding the maximum driving torque while the robot is moving with the maximum payload and the maximum speed. The moment of inertia is a predominant influence in the causation of big actuating torque.

Introduction of a unique robotic hand: SIA- I Hand

This paper describes the control of a three-fingered prosthetic dexterous hand developed by the State Key Robotics Laboratory at the Shenyang Institute of Automation, Chinese Academy of Science. A distributed control system is used to control the motion of this multi-finger hand. Preliminary experiment results show that the dexterity of the hand meets the design expectation and that the hand is able to perform a broad number of tasks with many gestures.

The Optimization of Mechanical and Electrical Integration Linear Output Transmission System with Sensor Function

The new highly integrated mechanical and electrical integration linear output sensor system designed is used to solve the problems of movement conversion/transmission, force transmission/ measurement etc. Firstly, further theory study is presented and the function of sensing parameters and transmission parameters is deduced; Secondly, the key parameters of system design and the constrained conditions are shown based on the system structure and strength theory. At last through simulation to determine the optimal structure parameters meeting the specific conditions and establish the corresponding relationship of parameters for future design.

Movement coupling analysis on the wrist of 165Kg spot welding robot

The driven system of 165Kg spot welding robot is introduced and the movement coupling of the wrist is analyzed in detail. The influence formulas of movement coupling to each joint of the wrist are derived theoretically. Furthermore, the kinematics simulation of the wrist is carried out by the software of Solidworks. The simulation results are in agreement with the theoretical calculation, which proves the validity of the transmission analysis. These can be used as reference for transmission design and motion control of industrial robots.

Nonlinear Vibration Analysis of Machine-tool Guideway System with Clearance

This paper studies hysteretic effect of machine-tool guideway system with clearance, establishes the nonlinear dynamics model of guideway system with symmetric clearance, and obtains the equivalent damping and equivalent stiffness coefficients using asymptotic method. With the use of time-domain graph, frequency-domain graph, phase trajectory figure, Poincare section figure, bifurcation diagram, and lyapunov exponent figure, the dynamics response of damping and external vibration frequency effect on system is studied. The result shows that the period, double-period and chaos movement will occur when the system parameters change in certain range.