1 Control Task
The control system design requirements for the test diagnostic platform are as follows:
(1) According to the instructions of the on-site assembly personnel, the operator issues the action command of the servo electric cylinders, and the four servo electric cylinders move individually within the total stroke range and stop reliably at the stroke limit position:
(2) The control box should have stroke display and action indication functions for each electric cylinder, and should be easy to operate and move.
2. Control Object Analysis
The experimental diagnostic platform is shown in Figure 1.
The host computer operating system controls the LSMC Micron L7s series standard I/O servo drive. This drive can operate in torque, speed, and position modes depending on its connection to the host controller, and can switch operating modes based on parameters and I/O input contact signals. While fulfilling the position control function, the mode selection places significant differences on the host controller's functional requirements. Torque mode places the highest demands on the host controller, requiring both position and speed loop control. Position mode places the lowest demands on the host controller, but it doesn't affect positioning accuracy; its accuracy depends on the servo motor encoder feedback accuracy and the electric cylinder's mechanical precision. Therefore, to simplify the host computer's functions, a fast and accurate all-digital position servo system is constructed using the servo drive and the electric cylinder APM AC servo motor.
3 Control System Design
Based on the analysis of the control task and the controlled object, the control system should provide a user-friendly human-machine interface, capable of semi-closed-loop position control of four servo electric cylinders, with operating modes including JOG continuous operation, JOG stepping and jogging, electronic handwheel mode, servo motor start/stop with S-shaped acceleration and deceleration, motor enable and brake control, etc.
Since an AC servo position control system is used, the L7s series standard I/O servo drive terminal input position operation mode wiring is used. The upper control system needs a programmable motion controller, motion control card or PLC with PTO (pulse train output) and an upper human-machine interface (HMI) touch screen that can communicate and connect with the controller or control card.
3.1 Control System Based on Four-Axis Motion Control PLL
The entire control system includes a power supply, a Xinje TH765 series HMI touch screen display, a Xinje XDM-32T-C four-axis motion control PLC, an electronic handwheel, and L7s series standard I/O servo drives. The HMI touch screen display, motion control PLC, and L7s servo drives form a monitoring system via a serial communication network using the MODBUs-RTU protocol. Its system structure is shown in Figure 2.
3.2 Human-Computer Interface Design
The Xinje TH765 series HMI touch operation display can be quickly configured with TOuchwin editing software to realize multiple interfaces, as shown in Figure 3, including operation and position display interface, servo drive status interface, alarm and history record interface, etc.
4 Applications
The AP inclined plane operating console integrated control system is adopted. The operating platform, as shown in Figure 4, mainly consists of an HMI touch screen display and an electronic handwheel. The left side of the electronic handwheel is an axis selection knob with five positions: OFF, X1, Y1, X2, and Y2. The right side of the electronic handwheel is a magnification selection knob with three positions: X1, X10, and X100. When in the OFF position, the hand-cranked metal encoder is ineffective. When in the corresponding axis position, the electronic handwheel and the hand-cranked metal encoder can be operated clockwise and counterclockwise, moving the corresponding axis forward and backward.
5 Conclusion
The domestically produced Xinje XDM series motion control PLC introduced in this article integrates motion control functions with ordinary PLC functions. It can support up to 10-axis pulse output and realize two-axis linkage. It supports both ordinary motion control commands, such as circular arc and linear interpolation, and planar conversion commands. It can perform two-axis linkage conversion such as Xy, yZ, and XZ. It is simple to implement, highly reliable, and has certain reference value for realizing multi-axis motion control.
