Inductive power transfer (IPT) systems conventionally operate at the natural resonant frequency for efficient power transmission, but their output power is sensitive to mutual inductance changes. Recent studies have shown that parity-time-symmetric IPT systems have two splitting frequencies in the strongly coupled range, enabling robust wireless power transfer with constant output power and high efficiency. Self-excited oscillation circuits can automatically track these optimal frequencies without measuring circuit parameters. However, practical self-oscillating systems contain voltage harmonics and feedback delays, which are often ignored in the analysis of steady-state performance. In this paper, the effects of high-order harmonics and time delay on steady-state frequencies are systematically analyzed. First, the formula of ideal bifurcation frequency is derived based on the zero-phase-angle condition. Then, steady-state conditions under square wave voltage and feedback delays are obtained using the Fourier series and superposition theorem. Finally, numerical examples demonstrate that exceptional points shift towards stronger coupling due to harmonics, whereas time delay could eliminate frequency bifurcation.

In this paper, a robust closed-loop speed control for wireless motor systems is proposed with the consideration of maximum efficiency point tracking (MEPT). Firstly, the optimal load condition for maximum efficiency point tracking of wireless motor systems is derived, a buck converter with an optimal duty cycle is adopted to achieve impedance match of the wireless power transfer system such that maximum efficiency can be guaranteed. Then, an integral fixed-time sliding mode (FTSM) control strategy is designed to achieve robust speed tracking control for wireless motors in the presence of parameter variation and external disturbance. The simulation results illustrated superior tracking performance with 15.90% speed tracking overshoot reduction, 26.90% speed tracking error RMS reduction compared with the conventional PID control. And the efficiency of the WPT systems is well maintained at 85.55% simultaneously.

ICSI (Intracytoplasmic sperm injection) is one of the most effective treatments for severe male infertility. During the implementation of the ICSI, it is necessary to perform the three-dimensional positioning of the tip of the glass injection micropipette. At present, the process is mainly controlled by skilled operators. Such manual operation is time-consuming and likely to cause micropipette damage or even serious damage to the oocyte membrane due to the inaccurate positioning. In this paper, an automatic system was developed for micropipette positioning. The microscopic positioning is carried out by autofocusing and planar positioning. A search strategy based on Dynamic Curve Fitting (DCF) was proposed to avoid local extremum issues due to the noises during the autofocusing. The proposed search strategy is adaptive to different focus algorisms, making the design of autofocusing becomes simpler. Besides, we proposed a planar positioning algorithm that can quickly and accurately obtain the tip position of the micropipette at the focusing plane. Finally, the visual servo control is employed to move the micropipette to the center of the vision. The experimental results demonstrated that the DCF method can accurately (mean error: 3 μm) find the focusing plane when applying random Gaussian noise with a mean value of 0 and a variance of 1 to the focus measure. By contrast, both the hill-climbing search method and the Fibonacci search method cannot work properly. The tip positioning algorithm provides a real-time in-plane tip positioning at a frame rate of 40 Hz with an average accuracy of 11 μm.