Signal control in NC operating state
In the numerical control system, the functions of tool jogging, workpiece setting, follow-up of the table, and correction of the origin of the machine are usually realized by handwheel operation. This function brings a lot of convenience to the machine operator. Handwheels are widely used in CNC machine tools. However, when the hand wheel swings around the micro-range, it is easy to produce jitter, which causes the output pulse to be inaccurate, which causes the machine tool to malfunction, and the workpiece is scrapped, which seriously endangers the operator's personal safety. Therefore, during the machining process, the precision And reliability is especially important. In the application of the actual numerical control system, the author summarizes and tests a well-structured handwheel signal processing method. 1 hand wheel working principle The handwheel, also known as the hand pulse generator, is essentially an incremental encoder and is a photoelectric position control component. The working principle diagram of the hand wheel is given. When the hand wheel rotates, the grating disk rotates at the same speed as the rotating shaft. After the detecting device composed of the light-emitting elements, the angle of the turning is converted into the position and direction information. The pulse sequence can drive the movement of each axis of the CNC machine under program control. Each revolution of the hand wheel produces a set of A, B signals with a phase difference of 90. In the forward rotation, the A phase leads the B phase 90, and when it reverses, the B phase leads the A phase 90. 2 handwheel signal processing handwheel output signal processing circuit has discrete components, special chips, microcontrollers, programmable logic devices and many other implementation methods. However, for multi-axis CNC systems, if discrete components are used to complete a series of encoder signals including handwheel signals, more components are required, resulting in complex structures, increased power consumption, and reduced stability. At present, complex programmable logic device CPLD is often used to realize the function of phase identification and filtering of handwheel signals. It consists of phase discrimination, debounce circuit, delay circuit, 16-bit reversible counter, output buffer and data bus. The functions of each part of the circuit are described below. 2 1 phase-detection circuit principle The function of the phase-detection circuit is to obtain the direction of rotation of the handwheel and generate the counter direction signal. According to the working principle of the hand wheel, in each signal period, the A signal pulse and the B signal pulse are different by 90, and the output signal is as shown. The handwheel direction information is defined as: if the A signal pulse leads the B signal pulse 90, the handwheel moves in the positive direction. 2 2 Handwheel signal phase discrimination, debounce circuit design in order to eliminate the handwheel output pulse caused by various interference factors. Clutter ensures the reliability and validity of the output signal and must be debounced before the counter is counted. Two methods are generally used to improve the ability to filter out clutter: one is to use Schmitt trigger as the input pole, the ability to shape the waveform by Schmitt trigger to filter the clutter; the second is to use multi-stage delay The time method to complete the filtering function. Similarly, phase discrimination can also be achieved using commonly used methods: D flip-flops and gates. These methods are simple to implement, but have poor anti-interference ability. Based on the above analysis, in order to better realize the phase discrimination and filtering of the handwheel signal, this paper adopts the state machine plus mark discrimination method. After repeated trials in actual work, it is proved that using this method to achieve the phase-detection and de-shake of the handwheel is better than the previous method. It can be seen that when rotating a scale, the ideal situation is that the A and B signal combinations have four states. When forward, the state of BA is: 00 01 11 10; when reversed, the BA state is: 00 10 11 01. For convenience of description, let S1=00, S2=01, S4=11, and S3=10. FP and FN in the figure are marks of the corresponding state of forward rotation and reverse rotation. When the transition from the previous state to the next state is completed, Corresponding position 1. If the forward or reverse rotation completes 4 states continuously, there is 1 pulse output, that is, Q = 1, and when the positive direction rotation is specified, the direction signal D = 1, and the reverse D = 0. The handwheel signal state transition diagram will be described in the following sections, and the CPLD implementation is taken as an example to illustrate the design process. When the current state is S1: (1) If the previous state is S1, the forward rotation flag is FP= 0001, FN= 0001, then Q = 0; (2) If the previous state is S3, and FP = 1111, then Q = 1, D = 1, the handwheel is rotating one scale; (3) if the previous state is S2 and FN = 1111, then Q = 1, D = 0, the handwheel reverses one scale; (4) if before A state is S4, this state is inactive, reset FP= 0001, FN = 0001, Q = 0, the handwheel has an interference signal, not counting. When the current state is S2: (1) If the previous state is S4 and FN= 0111, then FN=1111 is set, FP is cleared, and the handwheel signal completes the transition from S4 state to S2 state, which belongs to the intermediate process of one cycle. , the handwheel scale has not changed, Q = 0; (2) If the previous state is S1, and FP = 0001, then FP = 0011, FN is cleared, and the handwheel signal completes the transition from the S1 state to the S2 state. The result is the same as above; (3) If the previous state is S3, this state is invalid, reset FP= 0001, FN = 0001, Q = 0, the handwheel has an interference signal, not counting. When the current state is S4: (1) If the previous state is S3 and FN= 0011, then FN= 0111 is set, FP is cleared, and the handwheel signal completes the transition from S3 state to S4 state, which belongs to the intermediate process of one cycle. , the handwheel scale does not change, Q = 0; (2) If the previous state is S2, and FP = 0011, then FP = 0111, FN is cleared, the handwheel signal completes the transition from S2 state to S4 state, In the middle process of one cycle, the handwheel scale does not change, Q = 0; (3) If the previous state is S1, this state is invalid, reset FP= 0001, FN = 0001, Q = 0, handwheel There are interference signals coming over, not counting. When the current state is S3: (1) If the previous state is S1 and FN= 0001, then FN=0011 is set, FP is cleared, and the handwheel signal completes the transition from S1 state to S3 state, which belongs to the intermediate process of one cycle. , the handwheel scale does not change, Q = 0; (2) If the previous state is S4, and FP = 0111, then FP = 1111, FN is cleared, the handwheel signal completes the transition from S4 state to S3 state, In the middle of a cycle, the handwheel scale does not change, Q = 0; (3) If the previous state is S2, this state is inactive, reset FP= 0001, FN = 0001, Q = 0, handwheel There are interference signals coming over, not counting. 2 3 delay circuit It can be known from the working principle of the reversible counter that before counting, the direction must be discriminated. Here, the D-trigger can be used to delay the handwheel pulse signal by one clock cycle, and the circuit structure diagram is given. Therefore, the volume of the working space of the glazing robot is V=360 (R 2 m ax - R 2 m in) (1m ax - 1m in) (b max - bm in) 4 summary glazing process and process for typical sanitary ceramic products Requirements, after determining the principle of designing the glazing robot, the following conclusions are drawn: (1) the glazing robot can be an articulated robot with 5 degrees of freedom; (2) according to the typical sanitary ceramic products (ie, the dimensions of the one-piece toilet) The corresponding limit value can be selected to determine the structural size of each part of the glazing robot; (3) When the structural size of the glazing robot is actually designed, the working margin of the robot should also be considered; (4) The working space of the glazing robot is 4 The enclosed graphic area of ​​the arc, multiplied by the distance moved along the y axis. 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