Earticle

The intelligent reflecting surface (IRS) technology can enhance coverage in wireless networks by detouring a blocked path, where the phases of its passive elements are controlled to reinforce reflected signals in the desired directions, as the massive MIMO does. As a massive IRS system is introduced in the millimeter wave (mmWave) and tera-hertz (THz) bands, the optimal phase control induces computational complexity, and its complexity is doubled in multiuser systems. We propose a computationally efficient phase control algorithm in IRS-aided multiuser systems, where the reflected signals are sequentially aligned to search for optimal phases to maximize the total SNR of all users in service. The proposed scheme is evaluated with continuous phase and discrete phases with 1, 2, and 3 bits and compared with the random phase and full-search cases.

PURPOSE: This study examined the influence of treadmill exercise with initial pain control using transcutaneous electrical nerve stimulation (TENS) on induced pain of knee osteoarthritis in rats. METHODS: Thirty adult male Sprague - Dawley rats were divided randomly into the TENS Group (TG, n = 10), Treadmill Exercise Group (TEG, n = 10), and Treadmill with TENS Group (TTG, n = 10). In the TG, TENS was performed for 20 min per day for two weeks with a TENS program at the knee joint. The TEG performed treadmill exercise 15 m/min for 20 min per day for two weeks. The TTG performed initial pain control by TENS program during the 1st ~ 3rd days, and treadmill exercise was performed using the TEG methods from the 4th day. The lumbar spine was extracted and processed using western blot analysis to evaluate pain (c-fos expression). RESULTS: The results showed that c-fos expression was decreased significantly in all groups after each intervention (p < .05). In particular, TTG produced the most significant decrease compared to the other groups. CONCLUSION: These results suggest that treadmill exercise with initial pain control using TENS is a suitable method for relieving pain in knee osteoarthritis.

The use of robots in rehabilitation has become an issue of increasing importance because of the requirement of functional recovery therapy for limbs. A novel pneumatic artificial muscle (PAM) actuator - which has achieved increased popularity for providing safety and mobility assistance to humans performing tasks, as well as providing another advantages such as high strength and power/weight ratio, low cost, compactness, ease of maintenance, cleanliness, readily available, cheap power source, and so on - has been considered during the recent decades for use in a therapy robot, which in particular requires a high level of safety. However, some limitations still exist, such as air compressibility and the lack of damping ability of the actuator to bring the dynamic delay of the pressure response and cause the oscillatory motion. In addition, to aid rehabilitation more efficiently, the robot should adjust its impedance parameters according to the physical condition of the patient. For this purpose, the manipulator join is equipped with a Magneto-Rheological Brake (MRB). A new phase plane switching control method using MRB is proposed for tracking sinusoidal waveforms. The effectiveness of the proposed algorithm is demonstrated through an experiment using a fabricated two-axis PAM manipulator. The experiment proves that the stability of the manipulator could be greatly improved using a high gain control without regard to the change of the frequencies of the reference input and the external load condition, and without decreasing the response speed or lowering the stiffness of PAM manipulator.

Pneumatic cylinders are one kind of low cost actuation sources which have been applied in industrial and robotics field, since they have a high power/weight ratio, a high-tension force and a long durability. To overcome the shortcomings of conventional pneumatic cylinders, a number of newer pneumatic actuators have been developed such as McKibben Muscle, Rubber Actuator and Pneumatic Artificial Muscle (PAM) Manipulators. However, some limitations still exist, such as the air compressibility and the lack of damping ability of the actuator bring the dynamic delay of the pressure response and cause the oscillatory motion. In addition, the nonlinearities in the PAM manipulator still limit the controllability. Therefore, it is not easy to realize motion with high accuracy and high speed and with respect to various external inertia loads. To overcome these problems, a novel controller which harmonizes a phase plane switching control method (PPSC) with conventional PID controller and the adaptabilities of neural network is newly proposed. In order to realize satisfactory control performance a variable damper, Magneto-Rheological Brake (MRB), is equipped to the joint of the robot. The mixture of conventional PID controller and an intelligent phase plane switching control using neural network (IPPSC) brings us a novel controller. The experiments were carried out in a robot arm, which is driven by two PAM actuators, and the effectiveness of the proposed control algorithm was demonstrated through experiments, which had proved that the stability of the manipulator can be improved greatly in a high gain control by using MRB with IPPSC and without regard for the changes of external inertia loads.

Gyroscopes applications are widely used for measuring angular velocity and angular rotation of objects. For working of a vibratory gyroscope, it needs to be excited at its resonant frequency. An electronic circuit is necessary to drive gyro vibrating. This circuit is also named oscillation loop. To get best performance of a gyro, the oscillation loop has to drive gyro oscillating at its fixed resonant frequency and maintain gyro's vibration amplitude at prescribed value. That means the oscillation loop has two parts: phase (frequency) control part and amplitude control part. This paper is written to introduce phase locked loop (PLL) technique to design a phase control loop for vibratory gyroscopes, in this case is a hemispherical resonating gyroscope (HRG).

The analysis and control of a new type unsymmetrical slotted self-bearing step motor for small angle control is presented. The motor actuator is used for both motor and bearing functionality without any additional coil windings or electromagnets for bearing functionality. A circular-arc, straight-line permeance model for the fringing effect is presented. An unsymmetrical slotted self-bearing step motor layout and control algorithm are described. A new control current generation method using the electromagnets layout geometry, which needs no additional current for bearing functionality, is proposed. As the result of this analysis the fringing effect largely influences on the system characteristics. especially in torque. Even if the bearing functionality is added into the motor functionality, it is shown that the magnitude of torque is not changed.

In the phase-shift measurement method, the distance light travels can be obtained based on the phase difference between the reference signal and the measured signal. When the object having various colors is measured, the intensity of the measured signal much varies even at the same distance, and it causes different phase delay due to wide dynamic range input to a signal processing circuit. In this work, an measured intensity control method is proposed to solve this phase delay problem.

In this paper, we propose a novel velocity ripple controller using phase compensation feedforward control. Velocity ripples result in many kinds of performance degradations in manufacturing machines, especially such as ultra-precision roll lathes. The generation of velocity ripple in constant velocity control comes from various causes, such as electrical torque ripples, mechanical worn out, inconsistent mass center, etc. Conventional researches about ripple is mainly for reducing torque ripple in actuator level, which is only one of reasons for velocity ripples, so in this study, we focus on eliminating velocity ripples in upper level controller using phase compensation feedforward controller. The proposed algorithm is composed of several modules, such as ripple extractor, phase adjuster and phase follower etc. The suggested algorithm can be easily extended, and it shows a superior performance in the experiments of ultra-precision roll lathes.

Proposes a three-phase four-wire APF with four-leg topology based on one-cycle control. Main circuit adopts three-phase four-leg power topology. The fourth bridge arm connects to the zero line, which can inhibit the system zero sequence current. This topology is suitable for high power balanced and unbalanced load. Applying one-cycle control strategy, compares with the traditional control method of APF, it has advantages, such as fast dynamic response, strong anti-interference ability and so on. Meanwhile, the circuit structure is simple, low cost and easy to implement. Simulation and experimental results show one-cycle control with three-phase four-leg APF can effectively compensate harmonic, zero sequence and reactive current.

This paper proposes a new single phase variable structure control (SPVSC) for mismatched uncertain systems. A new sliding mode without reaching phase is designed to address two most important problems in the variable structure control area: 1) the system states are in sliding mode at the initial time movement; and 2) using only output variables directly. First, a new sufficient condition in terms of linear matrix inequality is derived such that the existence of a sliding surface guarantees asymptotic stability of the sliding mode dynamics from the initial time instant. Second, a static output feedback SPVSC law is designed to force the system states to stay in the sliding surface from beginning to end. Final, the lateral motion of a B-26 aircraft is simulated to demonstrate the advantages and effectiveness of the proposed SPVSC scheme.

This thesis develops efficiency optimization control strategies for three phase induction motors with Hall sensor. This thesis compares the different control strategies include open-loop voltage-mode control of hard-commutation scheme, open-loop voltage-mode control of soft-commutation scheme, and closed-loop current-mode control scheme, and analyzes the current response and overall efficiency. This thesis also develops a low-cost and high efficiency sensorless control for three phase induction motors drives. The proposed scheme detects the back-EMF zero-crossing-point (ZCP) to realize current commutation without Hall sensor. An adjustable blanking time control method is used to ensure correct detection of the ZCP. When using sensorless commutation control, the fan motor can start-up smoothly and operate under wide speed range, moreover, the overall efficiency is almost the same to the results of control scheme with Hall sensor.

Parallel operation of Multi-inverter can greatly improve the system's flexibility , power system's Capacity, redundancy and reliability, current through the power switch is divided, so the current stress for power switch can also be greatly reduced, the performance is improved with costs effective and power density. The conventional droop-control strategy which is adopted generally for parallel inverter regulates the phase and the amplitude of the output voltage according to output active power and reactive power，respectively.And active power and reactive power are related to both output amplitude and output phase for double closed-loop feedback voltage—source inverter．The control method of the droop control with virtual impedance is applied in this paper. The PQ droop control strategy for parallel single phase inverter is illustrated. PQ droop control scheme can effectively stabilize the droop control system to automatically exit, and also can achieve the expected load-sharing flow effect. Droop control without mutual connection, the inverter can be conveniently connected and removed. Finally， simulation results by obtained MATLAB / Simulink software is given to verify the effectiveness of theoretical analysis .

A switching-based SVPWM control method for three-phase active power filter is proposed in this paper. First, error model of the switched system is established. And then, according to the space voltage vector diagram and three-phase supply voltage waveforms, the supply voltage is divided into six sectors. In each sector, a combination of switching subsystem is set up according to the requirement of quadratic stability condition. Finally, the common Lyapunov function is selected and therefore, the subsystem is determined, which has minimum derivative of Lyapunov function and meets the conditions above. The validity of the proposed control method is proved with Matlab/Simulink and experimental results.

Three-phase bearingless induction motor is a multi-variable, nonlinear and strong coupling object, to achieve its high performance control, the dynamic mathematical models was analyzed firstly. According to the derived mathematical model, the reversibility of bearingless induction motor system was discussed, and the dynamic mathematical models of inverse system were derived. Then, based on the inverse system method, the dynamic decoupling control strategy of three-phase bearingless induction motor was researched, and the dynamic decoupling control system was build. Simulation results show that the dynamic decoupling control has been achieved between motor speed, rotor flux linkage and two radial displacement components, and the control system has higher dynamic and static performance; the presented decoupling control method is effective and feasible.

Due to synchronous rectification based on Phase-shift full bridge converter is difficult to work in a state of soft switch, to solve this problem, this paper sets out an control approach of synchronous rectification based on the ZVZCS phase-shifted full-bridge, and the drive signal of synchronous rectification side uses leading-leg drive waveform after a certain time delay and applies the resonant principle in the switching process，not only keeping full bridge ZVZCS soft switching but also realizing MOSFET of the synchronous rectification ZVS. The simulation of saber and experimental research show that the converter has a good performance.

Decoupling control of two-motor dual three-phase permanent-magnet synchronous motor (PMSM) series-connected system can be realized by using proper phase transposition rules with a single supply from a six-phase voltage source inverter (VSI), which solved the control problem of two motors in series. Since the traditional two-vector SVPWM strategy, which is commonly used in three-phase system, exists 5th and 7th harmonics in x-y plane, making it hard to realize decoupling control of two-motor dual three-phase PMSM series-connected system. Meanwhile, the DC bus voltage utilization of carrier-based PWM strategy is lower. Thus one method, which adopted a TBTSB-SVPWM strategy with two modulators, was proposed in this paper. It ensures the inverter output voltage only contains two kinds of fundamental components required by the two series-connected motors with a single VSI, making it possible to realize decoupling control of two-motor dual three-phase PMSM series-connected system. Simulation results indicate that there is no influence on the other motor while the speed/load of any one motor changed, achieving the decoupling control of series-connected system, and the feasibility and validness of the proposed approach are verified.

On the basis of the three-phase four-wire shunt active power filter (APF), this paper discusses the control system. In order to produce compensation current faster, it takes the fusion of FFT and p-q method to detect the harmonic current, and adopt dual-DSP hardware structure based on MCBSP to realize signal processing. At the same time, this paper presents a three- closed-loop control system to keep the accuracy. Then, we build some MATLAB models for the control system to verify the validity of this system. At last, we did an experiment to realize the communication between the dual-DSP.