Research On Control System Of Ultrasonic-resistance Hybrid Welding Power Supply

With the increasing demand for the non-ferrous metals in the modern industry, the welding problems of non-ferrous miniature component are attracting more attention. Aiming to solve the difficulties, ultrasonic-resistance hybrid welding which combines the advantages of the ultrasonic welding and resistance welding is put forward. In hybrid welding, ultrasonic vibration and current are applied to the component in particular ways to improve the properties of the welding joint. Since the method is still in the research stage, there is no dedicated power supply, therefore, a control system for the ultrasonic-resistance hybrid welding power supply is designed to improve the coordination and the adjustability of the hybrid energy output.First of all, the overall scheme and the control strategy of the hybrid welding power supply were determined, the main power circuits of the ultrasonic welding and the resistance welding were built. According to the control requirements of the hybrid welding, the control system based on DSP was designed, including signal feedback circuit, DDS circuit, phase shifted pulse generating circuit, CPLD circuits, switch control circuit etc.. The PCB board for the control circuit was designed and manufactured according to the electrical specification. The control software including ultrasonic frequency tracking program, A/D sampling program, input capture program, PI control program etc. were designed and debugged, to ensure all functions of the control system can be achieved.Then the hybrid welding power supply was assembled, and the experiment platform for the hybrid welding was built. The hybrid welding power supply was debugged and some welding experiments were done on the platform..Ultrasonic frequency tracking and voltage feedback control ensure the stable and adjustable vibration from the ultrasonic transducer, the constant-current output for the resistance welding is realized through the current feedback control. Three voltage amplitude parameters for ultrasonic welding and three current amplitude for resistance weiding can be set, making it flexible to get different hybrid energy output through setting the waveform parameters.At last, some welding experiments on T2-Cu and 6061-Al have been done on the hybrid welding system, the result showed that, a diffusion layer generates in the welding interface under the effect of ultrasonic vibration and current heat. And the results of tensile experiments showed that, the tensile properties and ductility of the joints in hybrid welding were improved comparing to those in ultrasonic welding.