Yuqiao Wang

Kinematics analysis of bridge-type micro-displacement mechanism based on flexure hinge

Bridge-type micro-displacement mechanism based on flexible hinge is a classical displacement magnifying mechanism. A flexible branched chain model was established to analyze the characteristics of the mechanism according to its symmetrical structure, thus the formulas for calculating output displacement and displacement amplification ratio of the displacement amplification mechanism were derived. Finite element simulation was carried on by software ANSYS11.0, and then compared with the theoretical model. Finally, an experiment sample piece was designed and processed to verify the theoretical model. The results showed that: the displacement amplification ratio of the bridge-type micro-displacement mechanism will increase first and then decrease, while the distance of the flexible hinges ly increase, and when the influence angle of amplification ratio α = 0.688°, the displacement amplification ratio get its maximum; Bridge-type micro-displacement mechanism can realize a displacement amplification ratio of more than 40 times, but the error will be amplified at the same time, so the amplification ratio of the bridge-type amplification mechanism should not be too large.

Modeling Hysteresis in Piezo Actuator Based on Neural Networks

Hysteresis and nonlinearity of piezo actuator are the major factors affecting the motion accuracy in controlling a micro system. The prediction accuracy of classical Preisach model could be improved only by mass experiments for measuring hysteresis. A model based on BP neural networks was proposed to improve the prediction accuracy. Because the stoke of piezo actuator have relation to historical extrema inputs, the input of the model are current exciting voltage, historical voltage at nearest turning point and its corresponding stroke and the output is piezo actuators stroke. Results of simulation and experiments show that the proposed hysteresis model can exactly describe and predict the hysteresis of piezo actuator compare with traditional bilinear interpolation and has the better generalization ability.

Vibration Response and Power Flow Characteristics of a Flexible Manipulator with a Moving Base

Flexible manipulator generally can be modeled as a coupling system with a flexible beam and a rigid moving base. This paper investigates the vibration responses and power flow of a flexible manipulator with a moving base (FMMB). Considering the motion characteristics of the rigid base, the moving base is modeled to have a motion with disturbances, and the dynamic model of the FMMB is established. With the dynamic model, vibration responses of the FMMB for the rigid base having disturbance velocities and accelerations are specifically presented. Subsequently, to investigate the effect of the disturbances on the vibration energy distributions of the FMMB, power flow of the FMMB is exhibited. To verify the dynamic model, an ADAMS physical model of the FMMB is constructed. It reveals that the motion characteristics of the rigid base have a noticeable effect on the vibration responses and power flow of the FMMB and should be considered. The results are significant and contribute to the vibration control of flexible manipulators.

Hysteresis modeling of piezo actuator using neural networks

Hysteresis and nonlinearity of piezo actuator are the major factors affecting the motion accuracy in controlling a micro system. The prediction accuracy of classical Preisach model could be improved only by mass experiments for measuring hysteresis. A model based on BP neural networks was proposed to improve the prediction accuracy. The stoke of piezo actuator has relation to current exciting voltage and historical extrema according to ‘wiping-out’ property of Preisach model. A model based on neural networks was established. The input of the model is current exciting voltage, historical voltage at nearest turning point and its corresponding stroke and the output is piezo actuators stroke. Results of simulation and experiments show that the proposed hysteresis model can exactly describe and predict the hysteresis of piezo actuator in comparison with traditional bilinear interpolation and has the better generalization ability.

Output displacement analysis for compliant single parallel four-bar mechanism

The compliant parallel guiding mechanism is widely used in the micro-driving and precision measurement. In order to analyze the output displacement characteristics of compliant parallel guiding beam, a half beam model was established based on the force analysis and deformation analysis of the supporting arm according to the symmetrical structure. And the guiding displacement and coupled displacement formulas was derived and verified by experiments. Results show that the guiding displacement is roughly linearly with the force and the relation between guiding displacement and coupled displacement is likewise exponential within elastic range of compliant beam.

Modeling and simulation the distribution of metro stray current

By simplifying and limiting current circuit model of metro power supply, this paper firstly showed stray current production and its damage, then analyzed bilateral power supply system using resistor network theory, and constructed stray current analytical model of bilateral power supply, computer simulation in different conditions of stray current distribution was carried out, the results show that metro stray current is affected by substation pitch, railway portrait resistor, rail-to-ground transition resistor and other factors, the distribution of stray current is provided macroscopicly in a qualitative way. This gives theoretical basis on how to set the distance of substation. Ultimately it provides a good solution to reduce the stray current corrosion.

Sensorless Control of a Shearer Short-Range Cutting Interior Permanent Magnet Synchronous Motor Based on a New Sliding Mode Observer

Considering the low reliability and poor adaptability of existing drum shear cutting parts, this paper presents a permanent magnet short-range cutting transmission system with a low-speed and high-torque interior permanent magnet synchronous motor (IPMSM) as the driving source and a sensorless control strategy based on a new sliding mode observer (SMO). To increase the robustness of the observer and reduce the error caused by chattering in the traditional SMO, the phase-locked loop technique is used instead of the traditional arc-tangent function estimation, and the sigmoid function is introduced to replace the traditional sign function; then, the sliding mode gain is adjusted through the fuzzy control algorithm in the new SMO. The scheme effectively improves the problems of the high failure rate caused by the long transmission chain of the shearer cutting section and the environmental impact for the mechanical sensor measurement results. Finally, the mathematical model of IPMSM based on the two-phase rotating coordinate system and end cutting load is established to verify the effectiveness and feasibility of the program. The results show that the new observer can accurately realize the speed and position estimation of the shearer cutting motor, and it has good dynamic response performance, observation accuracy, and robustness.

Dynamic Model and Vibration Characteristics of Planar 3-RRR Parallel Manipulator with Flexible Intermediate Links considering Exact Boundary Conditions

Due to the complexity of the dynamic model of a planar 3-RRR flexible parallel manipulator (FPM), it is often difficult to achieve active vibration control algorithm based on the system dynamic model. To establish a simple and efficient dynamic model of the planar 3-RRR FPM to study its dynamic characteristics and build a controller conveniently, firstly, considering the effect of rigid-flexible coupling and the moment of inertia at the end of the flexible intermediate link, the modal function is determined with the pinned-free boundary condition. Then, considering the main vibration modes of the system, a high-efficiency coupling dynamic model is established on the basis of guaranteeing the model control accuracy. According to the model, the modal characteristics of the flexible intermediate link are analyzed and compared with the modal test results. The results show that the model can effectively reflect the main vibration modes of the planar 3-RRR FPM; in addition the model can be used to analyze the effects of inertial and coupling forces on the dynamics model and the drive torque of the drive motor. Because this model is of the less dynamic parameters, it is convenient to carry out the control program.

Two-Time Scale Virtual Sensor Design for Vibration Observation of a Translational Flexible-Link Manipulator Based on Singular Perturbation and Differential Games

Effective feedback control requires all state variable information of the system. However, in the translational flexible-link manipulator (TFM) system, it is unrealistic to measure the vibration signals and their time derivative of any points of the TFM by infinite sensors. With the rigid-flexible coupling between the global motion of the rigid base and the elastic vibration of the flexible-link manipulator considered, a two-time scale virtual sensor, which includes the speed observer and the vibration observer, is designed to achieve the estimation for the vibration signals and their time derivative of the TFM, as well as the speed observer and the vibration observer are separately designed for the slow and fast subsystems, which are decomposed from the dynamic model of the TFM by the singular perturbation. Additionally, based on the linear-quadratic differential games, the observer gains of the two-time scale virtual sensor are optimized, which aims to minimize the estimation error while keeping the observer stable. Finally, the numerical calculation and experiment verify the efficiency of the designed two-time scale virtual sensor.

Dynamic Model and Vibration Power Flow of a Rigid-Flexible Coupling and Harmonic-Disturbance Exciting System for Flexible Robotic Manipulator with Elastic Joints

This paper investigates the dynamic of a flexible robotic manipulator (FRM) which consists of rigid driving base, flexible links, and flexible joints. With considering the motion fluctuations caused by the coupling effect, such as the motor parameters and mechanism inertias, as harmonic disturbances, the system investigated in this paper remains a parametrically excited system. An elastic restraint model of the FRM with elastic joints (FRMEJ) is proposed, which considers the elastic properties of the connecting joints between the flexible arm and the driving base, as well as the harmonic disturbances aroused by the electromechanical coupling effect. As a consequence, the FRMEJ accordingly remains a flexible multibody system which conveys the effects of rigid-flexible couple and electromechanical couple. The Lagrangian function and Hamilton’s principle are used to establish the dynamic model of the FRMEJ. Based on the dynamic model proposed, the vibration power flow is introduced to show the vibration energy distribution. Numerical simulations are conducted to investigate the effect of the joint elasticities and the disturbance excitations, and the influences of the structure parameters and motion parameters on the vibration power flow are studied. The results obtained in this paper contribute to the structure design, motion optimization, and vibration control of FRMs.