The Design And Implementation Of Control System For Torsion Bar Pressing-in And Straightening Machine

The project comes from a company's actual production needs, to assemble a torsion bar component, which was used in electric power steering system. Based on the requirements of the EPS torsion bar assembly, the previous process of torsion bar assembly was improve, and an automatic torsion bar pressing-in and pulling-out testing, component's radial run-out detecting and automatic straightening machine is designed.The machine designed overcome the traditional manual assembly processing's shortcomings such as low efficiency and difficult to ensure the accuracy. PLC is the system centre controller, working together with HMI, the system's work will be monitored all the time. The system's relative parameters can be set and modified, to make the efficiency and pass-rate as high as possible.The EPS torsion bar pressing-in and straightening machine's mechanical structure and hardware control system were designed. The power required, driving torque and working stroke in each step were calculated accurately. Basing on the calculations, suitable type of the servo motors, reducers, electric cylinders, air cylinders and laser displacement sensor in each step were chose. The hardware control system block diagram and the electrical control cabinet were designed.The control program of the system was designed using PLC. With the program, the torsion bar pressing-in operating station and the component's run-out measuring and straightening operating station can work independently. The system's working mode can be chose from manual mode, semi-automatic mode and fully-automatic mode according to the need. A digital filter program was designed to filtrate the interferences from the environment and the surface roughness of the work piece.As to facilitate the monitoring and operating of the machine, a series of Human-Machine interface is designed. The system's related parameters can be set and modified through HMI. Moreover, the working mode can be switched among manual mode, semi-automatic mode and fully-automatic mode freely.The accuracy of the system was tested, and the influences which lowering the system accuracy were found out. To improve the system accuracy, some proposals are given.The EPS torsion bar pressing-in bar and straightening machine designed can complete the torsion bar assembly work and the component's run-out measurement and straighten work well. The components obtained at last were all in the eligible range after the straighten process.