人体自由负重深蹲在稳定与非稳定条件下肌肉iEMG比较研究

为了进一步区别人体自由负重在稳定与非稳定条件下对浅层肌肉放电的影响差异及不同条件下负重与肌肉活性之间的关系,本研究对12名田径运动员在不同条件下的保加利亚单腿深蹲相关肌肉(11块)进行了表面肌电测试。结果表明:(1)随着负重的提升,人体肌肉i EMG值显著提高(P<0.05,P<0.01,P<0.001);(2)非稳定支撑面练习仅在低负重(0%RM)时较稳定支撑面练习对人体肌肉刺激更大(P<0.05);(3)人体在稳定与非稳定条件下自由负重深蹲练习的不同肌肉之间的组合用力模式不同,稳定条件主要刺激了人体的前部肌群,非稳定条件则主要刺激了后部肌群。研究认为:(1)人体在稳定与非稳定条件下的自由负重练习,负重是刺激浅层肌肉活性的主要变量;(2)人体在稳定与非稳定条件下的自由负重练习,肌肉活性与用力模式均需得到关注,应根据实际需求,合理选择训练方法;(3)稳定与非稳定条件下负重与人体肌肉的i EMG存在一种"S"型非线性曲线关系。

Vector control of induction motor based on fractional-order intelligent-integral speed controller

To improve dynamic and static performances and robustness of the induction motor speed control system based on vector control,an improved fractional-order intelligent proportional integral(IPIλ)controller was applied to the speed controller of the vector control system,which combined the intelligent fractional integral with the proportion according to the variation of deviation.Compared with proportional integral(PI)and fractional-order proportional integral(FOPI)controllers,the IPIλcontroller achieved better control performance.The stimulation results indicate that the IPIλcontroller can not only track the given speed quickly and accurately,but also have better anti-interference and robustness for load and parameters variations.

Improved control of intelligent excavator using proportional-integral-plus gain scheduling

Consider the design and implementation of an electro-hydraulic control system for a robotic excavator, namely the Lancaster University computerized and intelligent excavator (LUCIE). The excavator was developed to autonomously dig trenches without human intervention. One stumbling block is the achievement of adequate, accurate, quick and smooth movement under automatic control, which is difficult for traditional control algorithm, e.g. PI/PID. A gain scheduling design, based on the true digital proportional-integral-plus (PIP) control methodology, was utilized to regulate the nonlinear joint dynamics. Simulation and initial field tests both demonstrated the feasibility and robustness of proposed technique to the uncertainties of parameters, time delay and load disturbances, with the excavator arm directed along specified trajectories in a smooth, fast and accurate manner. The tracking error magnitudes for oblique straight line and horizontal straight line are less than 20 mm and 50 mm, respectively, while the velocity reaches 9 m/min.

An Improved Proportional Integral Estimator of the Stator Resistance for a Direct Torque Controlled Induction Motor

In this paper, an improved PI （proportional integral） stator resistance estimation for a DTC （direct torque controlled） induction motor is proposed. This estimation method is based on an on-line stator resistance correction regarding the variations of the stator current estimation error. In fact, the input variable of the P1 estimator is the stator current estimation error. The main idea is to tune accurately the stator resistance value relatively to the evolution of the stator current estimation error gradient to avoid the drive instability and ensure the tracking of the actual value of the stator resistance. But there is an unavoidable steady state error between the filtered stator current modulus and its estimated value from the dq model of the machine which is due to pseudo random commutations of the inverter switches. This may deteriorate the performance of the proposed fuzzy stator resistance estimator. An offset has been introduced in order to overcome this problem, for different speed command values and load torques. Simulation results show that the proposed estimator was able to successfully track the actual value of the stator resistance lbr different operating conditions.

Fuzzy Logic Controlled Induction Motor Based Intelligent Controller

The indirect vector controlled IM （induction motor） drive involves decoupling of the stator current into torque and flux producing components. This paper proposes the implementation of a fuzzy logic control scheme applied to a two d-q current components model of an induction motor. An intelligent based on fuzzy logic controller is developed with the help of knowledge rule base for efficient control. The performance of fuzzy logic controller is compared with that of the proportional integral controller in terms of the settling time and dynamic response to sudden load changes. The harmonic pattern of the output current is evaluated for both fixed gain proportional integral controller and the fuzzy logic based controller. The performance of the IM drive has been analyzed under steady state and transient conditions. Simulation results of both the controllers are presented for comparison.

Integrating Automatic Patch Snatching System by the Concept of Generalized Mechanisms

An automatic patch snatching system is described which has three machine cells including dividing equipment, tackling equipment and patch removing equipment. The electromechanical integration design of in-piece tackling system based on the concept of generalized mechanisms is introduced. The design of the dividing equipment, the design of micro-feeding machine equipped with micro-level pressure sensor, and the realizing of computer path for patch snatching are investigated.

An Electrochemically Assisted Mechanically Controllable Break Junction Approach for Single Molecule Junction Conductance Measurements

We report an electrochemically assisted mechanically controllable break junction （EC-MCBJ） approach to investigating single molecule conductance. Electrode pairs connected with a gold nanobridge were fabricated by electrochemical deposition and then mounted on a homebuilt MCBJ platform. A large number of Au- molecule-Au junctions were produced sequentially by repeated breaking and reconnecting of the gold nanobridge. In order to measure their single molecule conductance, statistical conductance histograms were generated for benzene-l,4-dithiol （BDT） and 4,4＇-bipyridine （BPY）. The values extracted from these histograms were found to be in the same range as values previously reported in the literature. Our method is distinct from the ones used to acquire these previously reported literature values, however, in that it is faster, simpler, more cost-effective, and changing the electrode material is more convenient.