Stepper motor constant current chopping subdivision driving system controlled by single chip microcomputer JI Xiuzhi s WANG Zong-si s XIE Feng-qin ZHAO Ping-yuan 3 REN Hui-ying 4(1. School of Mechatronics, Shandong University of Science and Technology, Tai'an 271019, Shandong, China;2. Power Control Engineering of Shandong University of Science and Technology College, Jinan 250031, Shandong, China; 3. Taishan Cableway Company, Tai'an 271000, Shandong, China:4. Mechanical and Electrical Equipment Manufacturing Plant of Yanzhou Mining Group, Zoucheng, Shandong 273500, China) Stepper Motor Constant Current Chopper Wave Dividing Drive Circuit and Its Function And characteristics are systematically elaborated.
A stepper motor is an actuator that converts a pulse signal into an angular displacement or a linear displacement, and is an incremental driving element that corresponds to a digital pulse input and output. With the advantages of high positioning accuracy, small inertia, no accumulation error, good start-up performance, easy control, low cost and convenient interface with the computer, it is widely used in CNC systems. The development of computer technology has promoted the development of digital control technology, making the drive system of stepper motor mainly from the hardware control to the control of the combination of soft and hard, which compensates for some disadvantages of the stepper motor control, such as low frequency vibration, high frequency out of step And so on, to improve the performance of the stepper motor, such as reducing the step angle, improve the running accuracy, make the stepper motor more widely used, more flexible control. The subdivision drive reduces the step angle, improves the running accuracy of the stepper motor, and reduces low-frequency vibration and high-frequency out-of-step phenomena. The system adopts a constant current chopper and subdivision combined driving method. Its characteristics are as follows: “complete switching†type is adopted to make the power thyristor work in the fully saturated and cut-off two states, reducing power consumption; Choose non-subdivided, fixed subdivision, and variable subdivision. The number of subdivisions can be selected from 0 to 255. The subdivision uses a single microprocessor to improve the processing speed.
1 stepping motor subdivision basic principle stepper motor drive is to each phase excitation winding current flow, so as to form a change in the magnetic field synthesis direction to make the stepper motor rotation, that is, change the power status, the rotor turns a Step angle. The formula for the step angle is: where a represents the number of line states of the incoming winding, W represents the number of phases of the motor, and B represents the number of teeth of the rotor. It can be seen that once the stepper motor is manufactured, the number of phases and the number of teeth of the rotor will be fixed values. In order to reduce the step angle to achieve the purpose of subdivision, only the user can change a. In the motor drive system, the current amplitude through the phase windings does not change, and the a value changes only when the power status of each phase changes. For a three-phase stepping motor, a=1 when the single three-shot or double three-shot operation is running, and a=2 if the single or double six-shot operation is running. If you want to increase a, you must press the current in the winding'. The steps rise and fall, that is, there are multiple stable intermediate current states between zero and maximum phase currents. The current waveforms for each phase are shown for three-phase six-shot four subdivisions. Each phase current rises and falls by 1/4 of the maximum current value. Compared with the single and double six-shot mode, the value of a increases from 2 to 8, and the step angle becomes 1/4 of the three-phase six-shot operation mode. Therefore, the key to subdividing the stepping motor is to control the phase winding of the motor. The current in the size and its stability.
2 system hardware circuit and characteristic This system circuit is shown as, mainly divides into three parts: Subdivision, power amplification, reference power.
Subdivided drive schematic subdivisions are dedicated to a single microprocessor. For the selection of the microprocessor, the more commonly used 89C51 is used, no expansion of the ROM and RAM, the circuit is simplified, and the cost is reduced. The upper computer mainly performs interpolation calculation, manual control, communication with the computer and sending pulses, selecting the direction of the stepping motor, selecting the stepping motor signal, sending the subdivision number, and performing variable subdivision control according to the speed. The main function of the subdivided microprocessor is to communicate with the host computer to perform a look-up table based on the number of subdivisions sent to complete the function of the ring distributor. The hardware in the conventional circuit is softened, and its function is to be controlled by the software according to needs. Flexible generation of required stepped current waveforms, flexible implementation of multiple subdivisions.
2.2 Power amplifier section The system uses constant current chopping wave drive. For the use of power amplifiers, FETs with higher switching frequencies are used to improve system performance. In a conventional constant current chopper driving circuit, the power amplifier tube cannot always be operated in a fully saturated or cut-off state, which increases the power consumption of the power amplifier tube, causes serious heat generation, and reduces the life of the power amplifier tube. If the power amplifier tube is thermally broken down, Will make the circuit not work properly. In addition, in the conventional circuit, the subdivided falling edge is the same as the rising edge, so that the power amplifier tube is operated in the chopping state, and the power amplifier tube T2 is directly operated in the conducting state. Since the current in the winding is decreased slowly, it is often caused by Falling edges cannot be subdivided. In order to solve the above two problems, the following measures are taken: the circuit is improved so that the power amplifier tube and the power amplifier tube T2 work in a completely on-off state, that is, they work in a fully saturated and cut-off state; and the T2 work in the same manner and is turned on at the same time. At the same time, the current drop rate in the winding is increased, the subdivision of the falling edge is better achieved, and the efficiency of the system is improved.
2.3 Reference voltage Because the DAC0832 uses a unipolar output, a dedicated integrated voltage conversion chip is used to convert the positive voltage to -5V to increase the stability of the DAC0832's reference voltage, and then the output voltage of the DAC0832 is adjusted to the actual level by the potentiometer. The required voltage value improves the system's anti-jamming performance.
3 System software functions and features are written in MCS-51 assembly language. The subdivided microprocessor uses interrupts to receive stepping pulses from the host computer. Its interrupt program flow chart is shown.
In the main program, the first step is to initialize the motor controlled by the microcomputer, that is, to provide a step current to the A-phase winding, which prevents the A-phase from changing from zero to the most interrupted program flow chart when the motor is in normal operation. The shock followed by waiting for the interruption.
In the interrupt program, the subdivided current value is stored in the ROM of the subdivided microprocessor in advance, and the subdivision number is determined by communicating with the upper computer, and the subroutine jumps to the corresponding subroutine according to the subdivision number, and then judges. The motor's steering uses the look-up table method to complete the distribution of data.
Kn95 Mask, Kn95 Fold Mask, N95 Respirator Mask, Kn95 Respirator
GUANGZHOU HTD INTERNATIONAL , https://www.maskhtd.com