Changhai Ru

A new ice gripper based on thermoelectric effect for manipulating micro objects

Manipulating small or micro objects has been a big challenging task in many areas. As the most basic tool to manipulate, fabricate, characterize, assemble and test the micro scale devices and biological samples, micromanipulation keeps receiving attentions over the area of micro technology especially micro automation. Research along this direction is becoming a major stream in the world. The paper presents a new type of ice gripper based on thermoelectric effect to form ice ball on the active part of the tip. The adhesion force of an intermediate, like water, is much greater in its solid phase than liquid phase. Enough force can be produced to pick a micro object by applying the principle. First, the theory the ice gripper based on is introduced. Next, an ice gripper is designed and the preliminary parameters which influence the ice ball formed are presented. It is shown that the ice gripper is a promising approach in micro manipulation, though some problems need to be solved.

An Improved Auto Focusing Algorithm for a Micromanipulation System

With rapid development of biotechnology and other relevant technology, micromanipulation in biotechnology has been drawing the attention of scholars home and abroad. Especially micromanipulation on micro scale is demanded, however, most of the current commercial micromanipulation systems adopt manual operation mode by mechanical or hydraulic transmission. In this circumstance, we develop and study a computer-controlled system. The system includes visualization part, human interface part and micromanipulator part. It can be used for cell puncturing and many other micromanipulations. In this paper we proposed a novel auto focusing algorithm. The whole visualization part includes two parts: auto locating part and auto focusing part. It not only can realize real-time monitoring, but also can accurately locate the targets position by visualization part and human interface part. The auto focusing algorithm has high correct ratio and high precision and stability.

A novel model of piezoelectric ceramic hysteretic

Piezoelectric actuators are widely applied as actuators in micro/nano-positioning systems, due to its characteristic of infinitely small displacement resolution. While the tracking control accuracy of the piezoelectric actuator is limited due to their inherent hysteretic nonlinearity. This paper describes a mathematical model which could compensate the hysteresis of piezoelectric actuator based on an inverse control in open-loop operation. The basis of the inverse control is formed by a hysteresis mathematical model, which can describe precisely phenomena. The mathematical modeling framework could precisely predict a hysteresis path for arbitrarily assigned input profiles. The new hysteretic model makes use of polar coordinate which has the advantage that the proposed model simplifies the identification procedure of its inverse model. The model can accurately predict the response of hysteretic nonlinearity in piezoelectric ceramic actuators; utilizing a piezoelectric-driven actuator, it is experimentally demonstrated that if the memory units is sufficiently recorded, model response in the prediction of a hysteresis track is significantly improved.

Modeling and compensation of piezoelectric ceramic hysteretic behavior

Piezoelectric actuators are widely applied as actuators in micro/nano-positioning systems, due to its characteristic of infinitely small displacement resolution. While the tracking control accuracy of the piezoelectric actuator is limited because of their inherent hysteretic nonlinearity. This paper describes a mathematical model which could precisely compensate the hysteresis of piezoelectric actuator based on an inverse control in open-loop operation. The basis of the inverse control is formed by a hysteresis mathematical model, which can describe precisely phenomena. The novel hysteresis model makes use of polar coordinate which has the advantage that the proposed model simplifies the identification procedure of its inverse model. It is experimentally demonstrated that the tracking precision is significantly improved.

Enhancement of Tracking Performance for Piezo-Nanopositioning Stage

Nano-positioning systems using piezoelectric stack actuator have a very wide range of applications including ultra-precision machine tools, diamond turning machines and motion stage. However, loss of tracking positioning precision in piezoelectric actuator occurs due to hysteresis during long range applications and creep effects when positioning is needed over extended periods of time. This paper describes a method for simultaneous compensation of the hysteresis and creep of piezoelectric actuator based on an inverse controller. Based on the hysteresis model and creep model, an adaptive inverse control approach is presented for improving tracking performance of piezo-nanopositioning. The inverse model of creep is identified by using LMS algorithm. The realization of an adaptive inverse controller for the linearization of a piezoelectric actuator is formulated. Finally, a tracking control experiment of piezoelectric actuators for a desired trajectory is performed according to the proposed method and the experimental results demonstrate that the positioning precision is noticeably improved in open-loop operation compared to the conventional open-loop control without any compensation.

A Novel Auto Focusing Algorithm for a Micromanipulation System

With rapid development of biotechnology and other relevant technology, micromanipulation in biotechnology has been drawing the attention of scholars home and abroad. Especially micromanipulation on micro scale is demanded, however, most of the current commercial micromanipulation systems adopt manual operation mode by mechanical or hydraulic transmission. In this circumstance, we develop and study a computer-controlled system. The system includes visualization part, human interface part and micromanipulator part. It can be used for cell puncturing and many other micromanipulations. In this paper we proposed a novel auto focusing algorithm. The whole visualization part includes two parts: auto locating part and auto focusing part. It not only can realize real-time monitoring, but also can accurately locate the targets position by visualization part and human interface part. The auto focusing algorithm has high correct ratio and high precision and stability.

Tracking Control of Piezoelectric Actuators by Feedforward Hysteresis Compensation

Due to the inherent hysteresis nonlinearity, the piezoelectric actuator always causes positioning error in the open-loop operation and instability in the closed-loop operation. In order to improve the positioning accuracy and response speed, a control method for piezoelectric actuator based on a PID feedback controller with a feedforward compensation is proposed. The feedforward controller based on a new mathematical model is used to describe the nonlinearity of piezoelectric actuator and improve the response speed. The feedback controller consists of a regular PID controller, which is used to improve the positioning accuracy. Finally, the tracking control experiments of piezoelectric actuators for a desired sinusoidal trajectory are performed according to the proposed control method and the experimental results demonstrate that the positioning precision is noticeably improved by augmenting the feedback controller with a model of hysteresis in the feedforward loop. The maximum error in tracking a sinusoidal signal is lowered about one order of magnitude in comparison with only using PID controller

A research based on piezoelectric ceramic hysteretic modeling and inverse control

Piezoelectric actuators are widely applied as actuators in micro/nano-positioning systems, due to its characteristic of infinitely small displacement resolution. At the same time, piezoelectricity material has nonlinear hysteretic phenomena, it will induce low position precision and it also results in closed-loop controlling system instable. This paper presents a new approach for modeling hysteretic nonlinearity in piezoelectric ceramic actuators. It is proved that the new hysteretic model can be proved to the general continuous, which makes use of polar coordinate. An advantage is that the proposed model simplifies the identification procedure of its inverse model. The model can accurately predict the response of hysteretic nonlinearity in piezoelectric ceramic actuators, when the input voltage is periodical and triangular signal; an inverse hysteretic model feedforward control strategy is then developed and implemented to compensate for the system ever present hysteretic nonlinearity.

An Improved Wideband Amplifier for Piezoelectric Actuator

Piezoelectric actuators are becoming increasingly important in such fields as vibration control, precision positioning, acoustics and sonar, and it is mainly driven by voltage in practical application. The amplifier driven by voltage has good stability and static characteristic, but in high speed motion conditions, we have to sacrifice frequency response bandwidth to ensure stability, so its closed loop frequency response bandwidth is relatively low. This study aims at the default what we have discussed about the present piezoelectric amplifier designed a new type of piezoelectric amplifier which has a wideband. In this paper, feedback zero compensation and noise gain compensation with the intention of increasing frequency bandwidth are used in the multilevel amplifier and the test results of the performance of piezoelectric amplifier are described. This piezoelectric amplifier has a relatively strong load carrying ability, short response time, wideband and high stability by feedback zero compensation and noise gain compensation.

Study and Realization of the Scene Simulation Technique For a Target Tracking Scene

The key techniques of realizing scene simulation are studied and a scene simulation system for target tracking in a campus is realized based on virtual reality (VR) technology in this paper. The motion of two mobile robots and the process of target tracking are simulated and a desktop VR simulation system is designed. Firstly, the methods of texture mapping and particle system in dynamic modelling are given and compared. Then, the models and the system are optimized in order to improve the speed and performance. Thirdly, a graphic user interface (GUI) is developed to setup the connection between the VR simulation end and the motion capture end by the socket network service. Through the network communication, motion position data of the robots are transmitted to implement simulation of six DOF motion. At last, the software of MultiGen Creator is used to build the models and Vega is used to drive the scene. At the same time, VC++ and the Vega API are combined to realize the VR system including the ramble function, special effects and etc. in a graphic workstation