Bi Shusheng

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.

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.

Modeling of a Cartwheel Flexural Pivot

A cartwheel flexural pivot has a small center shift as a function of loading and ease of manufacturing. This paper addresses an accurate model that includes the loading cases of a bending moment combined with both a horizontal force and a vertical force. First, a triangle flexural pivot is modeled as a single beam. Then, the model of cartwheel flexural pivot based on an equivalent model is developed by utilizing the results of the triangle pivot. The expressions for rotational displacement and center shift are derived to evaluate the primary motion and the parasitic motion; the maximum rotational angle is simply formulated to predicate the range of motion. Finally, the model is verified by finite element analysis. The relative error of the primary motion is less than 1.1% for various loading cases even if the rotational angle reaches ±20 deg, and the predicted errors for the two center shift components are less than 15.4% and 7.1%. The result shows that the model is accurate enough for designers to use for initial parametric design studies, such as for conceptual design.

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.

Design of a Family of Ultra-Precision Linear Motion Mechanisms

The parasitic motion of a parallel four-bar mechanism (PFBM) is undesirable for designers. In this paper, the rigid joints in PFBM are replaced with their flexural counterparts, and the center shift of rotational flexural pivots can be made full use of in order to compensate for this parasitic motion. First, three schemes are proposed to design a family of ultraprecision linear-motion mechanisms. Therefore, the generalized cross-spring pivots are utilized as joints, and six configurations are obtained. Then, for parasitic motion of these configurations, the compensation condition is presented, and the design space of geometric parameters is given. Moreover, the characteristic evaluation of these configurations is implemented, and an approach to improve their performances is further proposed. In addition, a model is developed to parametrically predict the parasitic motion and primary motion. Finally, the analytic model is verified by finite element analysis (FEA), so these linear-motion mechanisms can be employed in precision engineering.

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.

Design of Intelligent Monitoring and Controlling System for Foodstuff Deepfreeze

In order to improve monitoring and control level for small and medium scale enterprises, an intelligent monitoring and control system has been designed. In hardware designing, MSP430FG4619 was selected as microprocessor for its topping performance and ultralow-power consumption; and the temperature and humidity can be gathered accurately by SHT71 sensor. The acquiring information can be saved in the memorizer provisionally and can be transmitted by wired or wireless transmission. In fuzzy control system software designing, a prototype for fuzzy control was built in the first instance. On the basis of artificial manipulation experience and specific characteristics of the environment, the fuzzy control system can be built expediently by adding relevant parameters to the prototype. Practice shows that: the fuzzy control system prototype greatly improve development efficiency of intelligent monitoring and control system. The system has a high degree of automation and storage food quality is improved obviously.

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.