Development of hybrid stepping motor driver based on L297/298 chip Wang Pengfei, You Bo (School of Mechanical Power Engineering, Harbin University of Science and Technology, Harbin 150080, China) The drive is stable and reliable, improving stepping and positioning accuracy, and better control. Fever phenomenon.
Hybrid stepping motors are widely used in CNC machine tools, robots, remote control, aerospace and other fields, especially the development of microcomputers and microelectronics, making stepper motors more widely used. However, its disadvantages such as large step angle, low resolution, and easy heat generation often fail to meet the precise positioning and high torque control in the industry. The phase current of the motor winding rises. When the voltage of the sampling resistor rises to the reference voltage 1, the comparator flips. The flip-flop is reset, the power transistor is turned off, the current is dropped, and the next oscillation pulse is awaited. Thus, the flip-flop outputs a constant-frequency PWM signal, modulating the output signal of L297, and the peak value of the winding phase current is set.
Comparator sense resistor voltage L297 internal chopper circuit schematic L297 single-chip stepper motor controller IC is suitable for 3 hardware architecture bipolar two-phase stepper motor or unipolar four-phase stepper motor control. The L297 output signal can be used to control the L298 dual H-bridge driver set. As can be seen from the above, the L297 has a chopper constant current circuit internally, and the DAC0832 is enabled to set the signal phase current peak value. Therefore, the basic idea of ​​the driver hardware circuit design is The L297 is equipped with a suitable RC network to adjust the chopping oscillation pulse frequency. At the same time, the 8751 is used to generate the step of changing the subdivision voltage consistent with the phase sequence of L297, and is input as the 297 pin of L297, thereby controlling the Ref input terminal of the peak current of the winding current at the chopping time. Therefore, in the actual circuit Adopted in the design, double L297 single L298 structure. Drive part of the circuit such as. In the step of changing the subdivision voltage which is consistent with the L297 phase sequence by the 8751, the subdivided voltage generating circuit, for example, optically isolates the pulse signal of a certain external frequency through the idle diaphragm 6N137 and sends it to the external interrupt of the 8751 respectively. 1 and counter 0, where counter 0 operates in mode 2, that is, an 8-bit counter that automatically reloads the initial value. Since the counter 0 interrupt is one level lower than the external interrupt, there is no need to set the interrupt priority level. Whenever the external pulse signal is input, the counter is incremented by one. When the count register overflows, the counter 0 is triggered to be interrupted. In the interrupt response function, let The P10 port of the MCU outputs the corresponding pulse signal, which is sent to the CLOCK pin of L297 after being reversed. In the external interrupt 1 triggered subsequently, let the count variable self-add one, and output the array value with the count variable as the subscript to the P0 port, and then pass the 8-bit analog conversion of the DAC0832, and send the generated step voltage to the L297. Pin. In this way, not only the sub-division double L297 single L298 structure driving part hardware circuit diagram stepping motor subdivision voltage generating circuit 39 which is consistent with the L297 timing is realized, and the variable value of the high subdivision number can be realized.
In order to realize the subdivision driving of the stepping motor, it is necessary to take out the corresponding subdivision code at an appropriate time, and at the same time, it is required to complete the subdivision cycle output every time the motor phase sequence changes. The EPROM curing program flow chart is as follows.
4 Experiment and summary The hybrid stepping motor driver has been successfully applied to the motion control drive unit of the XY numerical control platform. By developing the control software under the Win-environment, the VC++ is designed with a good control interface interface to facilitate the stepping. Motor drive. The drive unit improves stepping accuracy and positioning accuracy through subdivision characteristics. During the long-term high torque driving process, the phenomenon of heat generation is better controlled due to its chopping constant current characteristics.
Drive power EPROM curing block diagram
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