This paper presents a position servo control approach for a permanent magnet linear synchronous motor. The nonlinear motor dynamics is expressed in the backstepping control scheme on which a recursive designing procedure is carried out. Based on the desired motion trajectory, the magnetic thrust force is first calculated and then treated as the control objective for the next subsystems. The command voltages to stabilise the whole system are established concerning the electric properties of the magnetic windings. To overcome the impacts of system uncertainties, an adaptive neural network is exploited to estimate the uncertainty and provide necessary compensation in the control effort. Based on the Lyapunov functional analysis, the adaptive laws for online tuning the parameters of the neural networks are derived so that the precision of position servo control can be improved. Compared with the conventional current regulated control scheme, this investigation introduces a voltage-controlled pulse-width modulation with a complete theoretic base, including the mechanical and electrical dynamics. The effectiveness of the proposed approach is verified by the experimental results and a comparison study with a recent work developed in the robust fuzzy PI control scheme.

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A novel dimmable light-emitting diode (LED) driver is proposed in this study. The circuit topology uses two active switches. One active switch shared by a buck-boost converter and a buck converter is operated at highswitching frequency while the other one is low-frequency pulse-width modulated to dim high-power LEDs. The buckboost converter plays the role of a power-factor corrector. It operates at discontinuous-conduction mode to waveshape the line current to be sinusoidal and in phase with the input-line voltage. The buck converter regulates the dc-link voltage to output a low-frequency pulse-width modulation (PWM) voltage to drive high-brightness LEDs. Since only one power-conversion process is required, and the buck converter works only when the low-frequency PWM voltage is at a high level, the proposed LED driver has the advantage of high efficiency. Besides, it achieves unity power factor and low total current harmonic distortion.

This study presents an analytic designing approach for the sensorless direct thrust force control (DTFC) of permanent magnet linear synchronous motor (PMLSM). A modified stator flux estimator developed by use of an adaptive mechanism and correction factors is devoted to measuring the stator flux linkage and the mover's position. The parameters of the flux estimator are adjusted in advance through an off-line identification process to increase the accuracy of estimation. Based on the principle of backstepping control, the reference q-axis flux command, which is equivalent to the thrust force command, is first obtained from the Lyapunov functional analysis. Then, the reference d-axis flux command is calculated according to the characteristics of stator flux linkage. The voltage control strategy is constructed to stabilise the global system and ensure the convergence of DTFC. Compared to the conventional direct torque/thrust control, the proposed control scheme can apply the space vector modulation to achieve a fixed switching frequency. Consequently, the phenomenon of flux and force ripples inherited from DTFC is improved. The experiment results are provided to validate the proposed control approach. Moreover, a recent work that is based on the optimal control is adopted as a comparison study.

In this paper, a fast charging balancing circuit for LiFePO4 battery is proposed to address the voltage imbalanced problem of a lithium battery string. During the lithium battery string charging process, the occurrence of voltage imbalance will activate the fast balancing mechanism. The proposed balancing circuit is composed of a bi-directional converter and the switch network. The purpose of bi-directional is that the energy can be delivered to the lowest voltage cell for charging mode. On the other hand, the energy stored in the magnetizing inductors of the transformer can be charged back to the higher voltage cell in recycling mode. This novel scheme includes the following features: (1) The odd-numbered and even-numbered cells in the string with the maximum differential voltage will be chosen for balancing process directly. In this topology, there is no need to store and deliver the energy through any intermediate or the extra storing components. That is, the energy loss can be saved to improve the efficiency, and the fast balancing technique can be achieved. (2) There is only one converter to complete the energy transfer for voltage balancing process. The concept makes the circuit structure much simpler. (3) The structure has bi-directional power flow and good electrical isolation features. (4) A single chip controller is applied to measure the voltage of each cell to achieve the fast balancing process effectively. At the end of the paper, the practical test of the proposed balancing method on LiFePO4 battery pack (28.8 V/2.5 Ah) is verified and implemented by the experimental results.

A high efficiency illumination for LED street lighting is proposed. For energy saving, this paper uses Class-E resonant inverter as main electric circuit to improve efficiency. In addition, single dimming control has the best efficiency, simplest control scheme and lowest circuit cost among other types of dimming techniques. Multiple serial-connected transformers used to drive the LED strings as they can provide galvanic isolation and have the advantage of good current distribution against device difference. Finally, a prototype circuit for driving 112 W LEDs in total was built and tested to verify the theoretical analysis.