A fully automatic packaging machine works by having an operator place a single-sided sealed bag in the bag supply compartment. The machine automatically completes a series of processes, including bag picking, bag feeding, and bag filling. Finally, the bag is sent to a clamping machine to shape the unsealed bag opening, and together with the upright bag conveyor, it is sent to a folding machine for folding. The folding machine, together with the upright bag conveyor, then sends the material to an automatic sewing machine for the sealing process. The bag sealing mechanism in a fully automatic packaging machine mainly consists of four parts: the bag clamping mechanism, the folding mechanism, the upright bag conveyor, and the sewing machine. Their specific locations are shown within the dotted lines in Figure 1. To maintain the bag's shape during transport on the upright bag conveyor, ensure a smooth and aesthetically pleasing folded seam, and improve the sealing rate, the horizontal conveying speeds of the sewing machine, folding conveyor, clamping conveyor, and upright bag conveyor must be consistent. However, due to factors such as processing errors, conveyor belt tension, and slippage, it is difficult to guarantee this through mechanical processing or adjustment alone. Therefore, a method using frequency converters to adjust the speeds of the folding motor, clamping motor, and upright bag conveyor motor, based on the sewing machine speed, is adopted to solve these problems. The speed is adjusted by multi-turn potentiometer and the forward and reverse rotation of the motor is controlled by digital input. The specific scheme is as follows: (1) Circuit design: The frequency is adjusted by three potentiometers. The inverter control terminal wiring is as follows: V1, V2, V3 - potentiometers; OP6 - forward rotation control input; OP7 - reverse rotation; OP8 - reset; CM common input terminal; TA, TC - fault alarm output. (2) Variable frequency drive (VFD) parameter settings: F114 = 0.5, F115 - 0.5, F2~ = 3, F2~ = 2 (if a PLC is not used, it needs to be set to 3) (3) VFD working process and speed regulation method: Since the VFD is installed in the control cabinet, which is far from the equipment site, the speed regulation potentiometers of the three VFDs are installed on the field operation table where the equipment operation can be directly observed. This makes it convenient for the operator to directly observe the equipment and perform frequency regulation. If any defective products are found to have passed through Yantai Huifeng Electronics Co., Ltd. during the operation (such as broken packaging bags), the equipment can be switched to manual operation mode. Press the "reverse conveying" button on the operation table, and the three VFDs will simultaneously control the motor to reverse and transport the material off the line. The specific control signal flow is shown in Figure 2. This scheme is simple and convenient for speed regulation, has few control links, and is easy to repair when a fault occurs. However, fine speed adjustments require the operator's experience. The potentiometer must have a locking mechanism. The potentiometer can be locked at any position after adjustment to prevent the potentiometer's rotating end from contacting other objects and rotating, thus changing the VFD frequency.