Research on Automatic Segment Switching without Communication in Automated Guided Vehicle Dynamic Wireless Power Transfer System

Automated guided vehicles (AGVs) are widely used in logistics warehouses, ports and other occasions. However, the problems of short AGV range, fixed charging position and long charging time always restrict the improvement of logistics efficiency. Dynamic wireless power transfer (DWPT) can realize contactless and uninterrupted power supply for AGVs on the move, which not only extends their driving range, but also reduces the volume and weight of their batteries. The DWPT technology is a feasible solution to improve the operational efficiency of AGVs. In the process of designing AGV dynamic wireless power supply system, its compact interior space is an important consideration in the design process, therefore, AGV needs a simple structure, small size, low cost DWPT system. As per the length of the Tx coils, the long-track type and the segmented type of DWPT system are classified. The segmented type DWPT system can improve system efficiency by segment control, which only allows the Tx coils under the Rx coil to be activated. Segment control highly relies on the proper functioning of position detection. The position detection method can be roughly categorized into three kinds: communication-based method, parameter estimation-based method, and detection-coil-based method. For the communication-based method, the global positioning system, Radio Frequency, and other method can be used. But it is not suitable for small size and compact interior AGVs. For the parameter-based method, the change of Tx side parameters is used for position detection. However, it usually requires Tx coils to be interval energized to detect the Receiver (Rx) coil, increasing the system standby loss. For the detection-coil-based method, additional inverters and hardware setup on the Rx side are needed to energize the detection coil, leading to complex deployment. However, the existing position detection methods need to set up communication module, or complex circuit and other hardware. And all need the controller to process the position signal for segment switching. To simplify the implementation complexity of segment switching, a position detection method and a segment switching strategy are proposed. The position detection is realized with only one detection coil at the Tx side, which can enable the switches without any additional power supply. As the detection coil and the Tx coil are decoupled by an additional capacitor, the detection coil is only coupled with the Receiver (Rx) coil. Therefore, the detection coil is only energized by the Rx coil. As the Rx coil moves in/out, detection coils along the moving direction are activated/deactivated to enable/disenabled switches to turn corresponding Tx coils on/offautomatically without any control modules or communication, whichis suitable for smallsize AGVs. The Tx array is comprised of n identical Tx coils (Tn), which transfer power to the receiver coil (R1). The Tx coils are wound around by n identical detection coils, resulting in a strong coupling between the detection coil and the Tx coil. To prevent the detection coil from being energized and triggered by the Tx coil, a circuit-based decoupling method is employed, which use a capacitor to cancel out the mutual inductance between Txcoil and detection coil. The DWPT experimental principle prototype of 500 W power level was built. The experimental results verify the two functions of Rx coil position detection and Tx coil segment switching of the proposed system. In the experiment, when the Rx coil moves, the Tx coil can switch in the correct order automatically according to the segment switching strategy, and there is no switching overvoltage. The stability of the output voltage is not affected when the Tx coil is switched in segments. The proposed method of non-communication position detection and automatic segment switching is feasible. © 2024 China Machine Press. All rights reserved.