The motor is an important actuator for all types of CNC machine tools.
The motor is an important actuator for all types of CNC machine tools. To achieve precise position control of the motor, the position of the rotor must be accurately detected. Photoelectric encoders are currently the most commonly used detection devices. Photoelectric encoders are divided into incremental, absolute and hybrid. Among them, the incremental type has been widely used because of its simple structure, long mechanical life, and easy realization of high resolution. Incremental photoelectric encoder output has A, B, Z three-phase signals, in which phase A and phase B are 90° out of phase, Z phase is the “zero position” of the encoder, and only one pulse is output per revolution. In applications, it is often necessary to divide the A-phase and B-phase orthogonal pulses by a certain ratio, that is, a sub-weekly ratio. The difficulty of frequency division is that the A' phase, B' phase pulse output after frequency division still remains orthogonal or nearly orthogonal, regardless of whether the set-wise ratio is an integer or a fraction. To this end, an FPGA-based integer-peripheral ratio implementation method is proposed. The method has simple logical structure, flexible configuration, easy expansion, and high practical value.
1 Electronic gear ratio and sub-week ratio Electronic gear ratio and sub-week ratio are a very important concept in CNC machine tools and CNC machining centers. Most of the servo drive devices in foreign countries have electronic gear ratio and sub-peripheral function. The electronic gear ratio KEG is the ratio of the pulse quantity and the command pulse quantity actually executed by the servo motor. The weekly ratio KDF is the servo drive received from the servo motor shaft. The ratio of the pulse amount of the pulse encoder to the amount of pulse actually fed back to the upper servo control system (CNC). In combination with the electronic gear ratio and the division ratio function, the user can easily realize the integer pulse equivalent, thereby avoiding the quantization error in the intermediate calculation, and directly transplanting the code to the number of lines equipped with different motor encoders without modifying the G code or Machine tools or machining centers with different pitch screws.
