Zong Guanghua

Analysis of Rotational Precision for an Isosceles-Trapezoidal Flexural Pivot

An isosceles-trapezoidal flexural pivot can be of great use for practical designs, especially in the cases that a pure rotation about a virtual pivot is required. The analysis of rotational precision for such a structure is important for the mechanical design in precise-required applications. For this purpose, a rigid isosceles-trapezoidal linkage model is first proposed to provide an accurate analytical result for its notch-type flexural counterpart. The influence of dimensional parameters on the center shift is discussed. In order to disclose the equivalence between leaf-type flexure structure and its pseudo-rigid-body model, a transitional model is introduced, from which an equivalent pseudo-rigid-body model for leaf-type isosceles-trapezoidal flexure structure is then derived. The results of both simulation and experiment verify that the equivalent rigid model is also accurate enough in the case of a larger deflection.

Realization of a Modular Reconfigurable Robot for Rough Terrain

Reconfigurable robotic systems are made from a large number of independent modules that can be used to form various robot shapes. As a result, the robots have the capability to adopt optimized configurations to suit different tasks and environments. The object of this research work is to build a mobile robot for rough terrain. In this paper, we developed a novel modular reconfigurable robotic system called JL-I. JL-I is a distributed system composed of several identical modules. Each module is self-contained including two powered tracks, a docking mechanism, pose-adjusting mechanisms, batteries, communication devices and microprocessors. The docking mechanisms allow the modules to connect or disconnect under computer control, and between each two adjacent modules, the pose-adjusting mechanisms are able to form an active spherical joint, which endows the robot with the abilities of changing shapes in three dimensions. This design of JL-I module realizes versatile robotic motion and configurations. Many useful functionalities such as getting recovery when the robot is turnover, getting over vertical steps can be obtained by different chain of motions. This paper describes the development, hardware and software construction of the JL-I robot. An actual system with three modules was build and basic configurations were examined

Dynamics of parallel mechanism with direct compliance control

Direct compliance control is an effective force control method for robot, especially for parallel mechanism robot. However, structural complexity of parallel mechanism and redundant actuation of the DCC requires make establishment of a dynamic model for robot control very difficult. In this paper, based on influence coefficient method, the dynamics of a parallel mechanism is deeply studied. The parallel mechanism without DCC is first investigated. Then is mechanism with DCC. The derived dynamic equations for both situations are not only easily established, but also simply expressed with mechanisms influence coefficient matrices. Therefore the dynamic algorithm can be easily realized on computer.

The Stiffness Model of Leaf-Type Isosceles-Trapezoidal Flexural Pivots

A leaf-type isosceles-trapezoidal flexural pivot can be of great practical use for designing compliant mechanisms. The analysis of load-deflection behavior for such a pivot is essential to the study of the mechanisms that are comprised of them. Based on the analysis of a single special loaded leaf segment, a pseudo-rigid-body four-bar model is proposed. The four-bar model is further simplified to a pin-joint model for some simple applications. The accuracy of both models is demonstrated by comparing results to those of nonlinear finite element analysis. At last, the two models are applied to analyze the cartwheel hinge as an example.

Accuracy analysis of the serial-parallel micromotion manipulator

The 6 DOF serial-parallel micromotion manipulator discussed in this paper comprises two 3 DOF parallel mechanisms connected in series with one another. Manufacturing tolerances, actuation errors, link offsets, and connection errors of two stages cause deviations with respect to the nominal structural parameters of the manipulator. If the nominal values of these parameters are used within the control software of the manipulator, the resulting pose of the end-effector will be inaccurate. In order to evaluate the effects of the above factors upon the pose accuracy, a vector arithmetic method is applied to establish the relations between the pose accuracy and manufacturing tolerances, actuation errors, and connection errors of two parallel mechanisms. Some results which are very useful to the design and manufacture of the micromotion manipulator are derived. The analysis method can also be used on the accuracy analysis of other type parallel or serial-parallel mechanisms.

On the implementation of stiffness control on a manipulator using rubber actuators

This paper deals with the stiffness control problem for a manipulator actuated by rubber actuators. Two stiffness control methods, the adjusting /spl Delta/P method and the adjusting P/sub 0/ method are presented and studied. The adjusting P/sub 0/ method utilizes the intrinsic flexibility of the rubber actuator to realize the joint stiffness control, which is different from conventional force control methods. Both methods are demonstrated experimentally, and their feasibility is confirmed with experimental results.

Dynamics analysis of a 6-DOF serial-parallel micromanipulator

A new dexterous 6-DOF two-stage serial-parallel micromanipulator is described. The kinematics of this mechanism are analyzed with the method of vector analysis, and some advantages are also discussed. Inertia forces, moments of inertia and elastic potential energy are also analyzed. The dynamics of the SP mechanism has been modeled using a Lagrangian approach.

CCD-based microarray scanner system

In this paper, the fluorescence detection of microarray is analyzed. The guidelines for optical system of microarray scanner based on CCD is proposed. A novel CCD-based microarray scanner system is developed in terms of the guidelines. The control subsystem and software for scanner are studied in details. Finally, some preliminary experiment results are presented.