In this paper, a robust wireless power transfer system is proposed with self alignment capability and controllable output current characteristics for static charging of automatic guided vehicles (AGVs). A reconfigurable circuitry is designed to work initially in an inductor-capacitor-capacitor-series (LCC-S) compensation mode for achieving magnetic field self alignment, then switched to an LCC-LCC configuration for wireless charging. Apart from the passive components used for wireless power transfer, no additional components such as cameras, sensors, or dedicated sensing coils are needed for self alignment. The induced voltage of a series tuned Q-coil on the load side is used for the AGV to automatically adjust its position. The vehicle will be self aligned when the induced voltage becomes null, then the system is switched to a controllable constant current (CC) charging mode. A prototype is built which demonstrates that the output charging current is controllable and can be kept constant against load variations. The experimental results show the proposed system can realize an 89.1% dc-dc power transfer efficiency (PTE) at an output current of 30A and output voltage of 48V.

The main purpose of this study is to investigate the dynamic mixed elastohydrodynamic lubrication (DMEHL) behavior of the water-lubricated bearing with unbalanced rotor during start-up. To achieve this, a DMEHL model that couples the rotor dynamic model considering the unbalanced load with the transient mixed lubrication model is established. The validity of the calculation procedure is verified by comparisons with published experimental and numerical results. Using numerical studies, the optimal accelerating mode for reducing the transient asperity contact during start-up is identified. Numerical results indicate that during start-up, the rotor dynamic characteristic and hydrodynamic force are more sensitive to the unbalanced load than the transient contact force, and the rotor imbalance eccentricity will affect the transient contact behaviors if the surface roughness is relatively large. In addition, the DMEHL responses are affected by the unbalanced load only when the accelerating time is small. Finally, the DMEHL responses during start-up using three different water-lubricated materials, namely, polymer, Thordon, and ceramic, are compared. It is found that DMEHL performance at the start-up stage highly depends on the elastic modulus and hardness of the water-lubricated material.

The magnetic coupling wireless power transfer (MC-WPT) system for automatic guided vehicles (AGVs) is characterized by a small and unfixed air gap, which leads to significant changes in self- and mutual inductance of the magnetic coupler. In this paper, an efficiency improvement method is proposed for the MC-WPT system with variable self- and mutual inductance parameters. By optimizing the design of magnetic couplers and compensation parameters, a wide range of zero voltage switching (ZVS) operation and minimization the reactive current are achieved. The self-inductance variation is utilized to provide a variable system input impedance, which expands the ZVS operation range with phase shift modulation (PSM). Meanwhile, the reactive current of the resonant tank in the entire air gap range can be reduced to the minimum when the tuning parameters are designed properly. Compared to traditional hybrid control strategies, the proposed method offers a simpler control scheme and eliminates the adverse effects caused by the self-inductance variation. A laboratory prototype is built to verify the theoretical analysis. Experimental results show that system achieves ZVS operation and minimum reactive current within an air gap range of 20-50 mm, and efficiency reaches 91.2%.

Wireless power transfer (WPT) technology, leveraging the unique advantage of contactless power supply, has been recognized as a core power supply solution for mobile devices such as automated guided vehicles (AGVs) and electric vehicles (EVs). However, its transmission performance is highly susceptible to lateral offset, longitudinal misalignment, and angular deflection of the coils, resulting in a sharp decline in efficiency and unstable output. This has become a key bottleneck restricting the engineering application of the technology. This paper presents a comprehensive review focusing on the misalignment tolerance technologies for WPT systems. First, taking the LCC-S/LCC topology as an example, the influence of coil misalignment on the system output performance is analyzed, and various misalignment tolerance methods are enumerated. Subsequently, the basic principles and main research achievements of four categories of misalignment tolerance technologies, namely coupling structure optimization, compensation topology optimization, control strategies, and alignment guidance technology, are systematically summarized, with their limitations identified. Finally, the future research directions of misalignment tolerance technologies are discussed.

In this article, a misalignment-adaptive wireless charging system for inspection robots (IRs) is proposed, which has autoalignment capability in the x-axis and high coupling tolerance in the y-axis. A reconfigurable secondary compensation circuit is designed to work initially in the inductor–capacitor–capacitor series (LCC-S) mode for magnetic field autoalignment, and it is then switched to LCC–LCC topology for wireless charging. The Q-coil is used in a reconfigurable coupling structure to adjust the IRs position for autoalignment, and it is also used as the compensation inductor for wireless power transfer (WPT). The DD coil in the secondary side is used to achieve high coupling tolerance capability in the y-axis. A laboratory prototype with an output current of 22 A and output voltage of 52 V is built, and practical results show that the system can achieve an alignment accuracy of ±5 mm in the x-axis, and the output current fluctuation of the system is ±3.2% when the misalignment ratio along the y-axis is 40%.

To mitigate coil misalignment caused by inaccurate AGV parking—which leads to fluctuations in charging voltage, current, and power—this article proposes a wireless power transfer (WPT) system featuring dual-mode switching with coupling reversal and constant-voltage (CV) output. By switching the system operating mode, the mutual inductance is reversed from a subtractive to an additive state, thereby restoring the system’s mutual coupling after coil misalignment. Based on this functionality, a switchable-mode topology with a corresponding compensation method is proposed, in which the system operates in a subtractive mutual inductance mode under the LCC-S topology before switching and transitions to an additive mode under the LCC-S–S topology within a specified misalignment range, thereby effectively enhancing the system’s misalignment tolerance. To validate the system’s effectiveness, a 500W experimental prototype was developed. The experimental results show that, within an 8% output voltage fluctuation range, the system’s misalignment reaches 54% of the maximum coil size, a 6% improvement over the pre-switching misalignment of 48%. The system’s dc-dc maximum transfer efficiency is 90.28%.