It mainly completes the acquisition, encoding and storage of the input keyboard signal of the special keyboard, and generates an interrupt signal, requesting the industrial computer to read the key value and make corresponding processing. The input of various operation commands and the parameter input of the machining process control file are completed by means of a dedicated keyboard.
The multi-axis AC servo drive control card is composed of two sets of servo amplifiers, servo motors and encoders, and two semi-closed loop servo control systems. The main task is to complete the control of the start, acceleration, deceleration and stop of the servo motor according to the command sent by the industrial computer, and generate 6 interrupt signals according to the motion state of the two servo axes: position error overrun, transmission midway shift point The location counter value has been fully folded back, the encoder indexing flag and the illegal control command.
The optically separated digital output card and one SSR relay module port board complete the grinding head motor, the head frame motor, the cooling valve, the upper and lower feeding mechanism, the receiving mechanism, the fixture cleaning device, and the X-axis and Z-axis servo amplifier outputs. Enable, output control of switch control signals such as alarms.
The digital signal input card and one optical isolation input port board jointly complete the monitoring of the feeding, unloading, receiving mechanism and the X-axis and Z-axis 5 pairs of limit signals and the machine cooling and lubrication system status signals. Any of the limit signals can cause a hard interrupt to ensure no damage to the mechanical system.
The characteristics of the control system are as follows. Servo control accuracy analysis to ensure that the servo drive output device has a certain mechanical strength, the table drive part uses a ball screw with a pitch of 6mm, and the encoder installed at the end of the servo motor generates 4096 pulses every time the servo motor rotates. And output to the pulse counter on the servo control board. Therefore, each pulse theoretically corresponds to a table displacement of 1.4 m, which is less than 1/5 of the allowable error of the design. Usually in a high-precision control system, the theoretical design error generally takes 1/3 to 1 of the tolerance. 2, so from the perspective of signal resolution, the system design requirements can be fully met, and the test results confirm the correctness of this selection.
Servo control mode and signal transmission mode In order to ensure that the computer has enough time to respond to and process the user's special commands, and meet the requirements of control accuracy, the PID servo control board with PID parameter adjustment is adopted. Before the industrial computer sends a control command to the control panel, it only needs to select a reasonable PID coefficient according to the displacement, velocity and acceleration parameters, calculate the theoretical pulse count value corresponding to the displacement and the speed count value and the acceleration count value obtained by the difference principle, and After transmitting the above values ​​to the servo control board, the industrial computer completes the output operation of the servo control once. Therefore, the industrial computer has a lot of time to process external requests and status displays. Even in the case of two-axis linkage control, the two-axis starting time difference is only 1.2×10-7s according to the machine code. In the case of 3000r/min, the resulting displacement error is about 0.03m, so it can be ignored.
A Hall element sensor is provided for each controlled mechanical device to detect whether it reaches the limit position, which can protect each moving mechanism from being damaged, and is used to specify the coordinate origin of the servo axis. These detection signals are linked to the industrial computer by means of an interrupt request.
The control signal input from the membrane keyboard during the cyclic processing is also connected to the industrial computer by means of interruption, and the industrial computer performs corresponding processing through key value analysis. Fault and protection control To prevent accidents, the control system has three safety protections to stop the machining operation. The first type is the emergency stop button on the main control cabinet. When it is pressed, it will send a low level signal to the servo amplifier and the industrial computer at the same time. Its function is to make the servo amplifier output enable signal position zero, and stop the servo part output. After receiving the signal, the industrial computer releases all the outputs and reboots into the initial preparation state of the machining. The second type is to use the red stop button on the membrane key to make the control software enter a specific interrupt service, return the two servo axes to the home position lock in time, release other external outputs, and then wait. The third type is the power control button on the main control board. Pressing this button will cut off the power of the industrial computer and the servo amplifier. It is the control protection button for emergency stop.
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