Da Peng Fan

Design Consideration for Precise Cable Drive

A brief overview of previously built Electro-Optical Tracking system reveals a trend toward smaller, more agile systems. Steel cable drive technology is an alternative to gearbox, belt and pulleys, chains and sprocket and other currently available transmission for several significant advantages, which includes backlash free, high stiffness, high efficiency, no lubrication etc.. As a new type of drive form, there were several key tradeoffs for the cable drive application, which will be developed and subjected in detail in this paper. Firstly Transmission principle and properties of cable drive is studied. Secondly, related design considerations of cable drive will be implemented and researched in detail, including the cable selection and capstan design, cable-groove matching strategy and cable tensioning design. Finally, actual application example of precise steel cable drive is presented for an Electro-Optical tracking gimbals, and performances tested validate the significant advantages of precise cable drive technology.

A Fast Algorithm to Compute B-Splines and its Application in Curve Fitting

B-spline method plays an important role in data interpolating, fitting and smoothing. Through analyzing the computed path of the de Boor-Cox algorithm, a new method for calculating B-spline function is given based on the vector extending operation. The proposed method has a parallel computing architecture and is suitable to realize by computers. Compared with the de Boor-Cox algorithm, the proposed method can improve computing efficiency by (2k+1) times in the task of calculating all nonzero values of k-degree B-spine functions. As an application in B-spline curve fitting, it shows that the proposed algorithm can reduce the computing efforts obviously.

Transverse Stiffness and Guiding Characteristics Analysis of Compliant Linear Guided Mechanism

This paper presents a novel compliant linear guided mechanism (CLGM) to replace traditional spring and translation joint to transfer motion and force with its advanced guiding characteristics. In view of the incompatible relationship between axial stiffness and transverse stiffness of CLGM, eight kinds of CLGMs were developed by using building block approach based on fixed-guided flexure beam. The finite element analysis (FEA) models of eight CLGMs were built to complete numerical analysis on the force-displacement in axis and off-axis direction with same geometric sizes. The FEA results show that the structure configuration of Type 2-Type 8 can achieve a larger axial travel, Type 2 and Type4 have the advanced guiding characteristic with higher ratio of axial/transverse stiffness. Analysis indicates that the building block approach is an efficient method to complete the conceptual synthesis of compliant mechanism and FEA is effective on the structure optimization for the required compliance and stiffness in axial and transverse direction.

A Piezo/Gear Compound Drive: Principles Analysis and Simulation

Increasing demands regarding the light-weight, high-torque and high-precision actuator are inducing the need for new actuators and new drive principles. This paper introduces a novel principle for transforming the linear motion of high performance piezoelectric actuators into continuous rotation is implemented by two piezoelectric actuators acting on a driving gear covering a driven gear with a slightly smaller diameter. By driving the piezoelectric actuators, the driving gear is energized to move on a circular trajectory around the driven gear which is thereby slowly rotated. Firstly, the structure and driving mechanism is introduced. Secondly, transmission ratio, the demand driving force and displacement are analyzed theoretically and by the means of simulation analysis. Finally, the bottlenecks of mechanism design and machining are presented. Some instructive reference for the structure design of Piezo/Gear compound drive is provided.

Modeling of Harmonic Drive System with Low-Frequency Resonance

In the design process of lightweight harmonic drive system, low-frequency resonance generally affects controller design, and restricts system servo performance. In the design stage of system, it has great significance that the resonant frequencies and dynamic performances could be predicted. This paper presents a modeling method of harmonic drive system which has low-frequency resonance. Takes an uniaxial harmonic drive system as example to describe the implementation process of the modeling method. The dynamics model of harmonic drive system has been built. Using Ansys, Recurdyn and Matlab, the rigid-flexible coupling dynamics simulation model of system has been established. The simulation model analysis and the actual system experiment have been done respectively. Comparing the simulation and experiment results, it shows that: the open-loop time-frequency domain characteristics and the structural modals of simulation and experiment results are basically consistent. Using this method, the resonant frequency and dynamic performance of harmonic drive system can be predicted in the system design stage, and improve design efficiency.

Error Analysis and Calibration of Gyro-Stabilized Platform for Electro-Optical Pointing System

A novel method in the solution of the pointing problem for electro-optical pointing system (EOPS) is presented in this paper. Firstly, the error sources are analyzed in detail. And then, a linear model whose parameters have definitely physical meaning is developed to improve pointing accuracy. Extensive experiments have been carried out and the results show that the system errors can be eliminated by the model effectively and the pointing accuracy of the azimuth and elevation axes have been improved from 0.4541º and 0.2959º to 0.038º and 0.031º respectively.

Exploration into the Innovative Mode of Combining Learning with Researching and Production

It is proposed that the integration of learning, researching and production provides a good solution to the problem that higher education fails to offer qualified graduates demanded by machinery manufacturing industry. This paper first analyses the weakness of enterprises in scientific research and creativity and inexperience of higher education institutes in transferring scientific achievements, then some advice is given as to how to improve the innovative integration mode followed by some successful cases. At last it goes deeper into the future tendency of this mode.

Torsional Vibration of Precise Cable Drive System

Precise cable drive has been developed as an alternative transmission element to gearbox, belt and pulleys, chains and sprocket in Electro-Optical Tracking system. Precise cable drive has several significant advantages including backlash free, high stiffness, high efficiency, no lubrication etc.. This paper develops analytical methods to predict the Torsional Vibration of precise cable drive to enable designers to better assess dynamic performance in the design study phase. Theoretical formulation of transmission stiffness for precise cable drive is carried out, the dynamic equation of cable drive system is deduced and inherent frequency is obtained. Parametric studies are conducted to evaluate the relationship between the inherent frequency and cable drive parameters.

Design of a Large-Torque Precise Cable Drive Mechanism

Precise cable drive has been developed as a new-style transmission element that has the advantages of low backlash, high stiffness, high efficiency, no friction and no lubrication, and is widely used in electro-optical tracking system. A precise cable drive mechanism is designed in this paper. Its torque output is greater than 50Nm and precision is less than 0.1mrad. Size of the cable is selected base on the maximum load of the cable evaluated in the process of the reciprocating motion. In order to improve the driving capacity, design the cable-groove match strategy with the non-intervene cable wrapping method. A figure eight pattern wrapped method and screw pitch of the cable wrapped line is designed. The influence of the contact angle on the preload force and the influence of the preload force on the backlash are simulated by the software Matlab when the mechanism driving the maximum load. At last magnitude of the contact angle and the preload force is confirmed.

Analysis of a 3-DOF Micro-Positioning Stage

Firstly a three degrees of freedom micro-positioning stage constructed by flexure hinges is designed, and the simplified model of the stage is established. Secondly, the stiffness of the stage along X, Y direction or around Z direction is deduced by structural mechanics. The difference between finite element method and theory value is less than 7%, so it shows the theory analysis is feasible, further more, stress of the moving stage is analyzed, and the effect curve of the key parameters to the stiffness and stress is obtained. It can be concluded that the stiffness and stress mainly related with the flexure hinge length L and width t, thus it provide a theoretical basis for three-dimensional micro-positioning stage design.