Design of Improved Five-phase Hybrid Stepper Motor Driver Based on Single Chip Microcomputer

Design of Improved Five-phase Hybrid Stepper Motor Driver Based on Single Chip Microcomputer

Design of an Improved Five-phase Hybrid Stepper Motor Driver Based on Single Chip Microcomputer Yu Hongquan, Hu Weixiong, Yan Gangfeng (College of Electrical Engineering, Zhejiang University, Hangzhou 310027, Zhejiang, China) There are many disadvantages to the stepper motor driver: low frequency torque oscillation, high frequency output rotation Insufficient moments and multiple power supplies. Based on the analysis of the existing stepper motor driver and combined with the theoretical analysis, an improved five-phase hybrid stepper motor driver based on single-chip microcomputer is designed. The driver uses a single power supply and adopts a three-phase excitation PWM output mode to improve the torque-frequency characteristics of the drive. It is put into use in computerized embroidery machine systems and achieves good results.

Stepper motors are widely used in automatic control systems as an execution component. Hybrid stepper motors are widely used due to their high operating frequency, high dynamic torque, small fluctuations, smooth operation, low noise, positioning accuracy, and high resolution. Used in various mechatronic equipments.

In the textile machinery, the most commonly used stepping motor is a five-phase hybrid stepper motor, and the stepper motor used in the computerized embroidery machine system is generally 110BYG550, so the author designed it is also matched with the driver - in the analysis of the computer Based on the existing stepper motor driver in the embroidery machine, in order to reduce its low frequency torque oscillation, improve the high frequency output torque, and facilitate the use, the author designs an improved stepper motor drive 1 existing stepper motor driver. The disadvantages of stepper motor driver input control signals are generally four: (common anode), FREE (offline level), DIR (direction level), CP (step pulse). The existing computerized embroidery machine system stepper motor driver (for example, a certain model), using AT89C2051 control chip, to accept external control signals, output 5 signals, after the decoding circuit to get 10 output signals, and then through the upper and lower arm The driving circuit drives the power MOSFET to obtain a five-phase output for driving the stepping motor. At low frequency operation, the output current has a large impact. In order to reduce the impact of the current, FREE signal is needed to block the output of the engineering design journal frequently; during shutdown or long When there is no input step pulse, it is necessary to input the FREE signal to close the output, so as to avoid the stepper motor phase current is too large, the power-on time is too long and heat. When it is offline, there is no output torque; in the computerized embroidery machine, this situation has little effect (the load is a repulsive load), and for a potential load, if the torque is to be locked, the FREE signal must be coordinated , To achieve PWM output, this will take up some of the resources of the master CPU; or in the stepper motor winding in series with the current limiting resistor without off-line, so that the corresponding increase in loss. The excitation method of the existing stepping motor driver is two-phase excitation, and the torque output under this method is not the largest, especially at high frequencies, the output torque is insufficient. The input power supply requires two inputs: control power (AC220V) and operating power (AC90V). The input of the dual power input, especially AC90V, needs to be matched with the transformer, that is, the transformer must be used when the stepper motor driver is used. This not only causes the inconvenience of use. It also increased spending.

2 Some theoretical analysis on the stepper motor bookmark3 phase: 2.1 Analysis of stepper motor torque The stepper motor torque is expressed as follows: Stepper motor excitation method (single-phase excitation, two-phase excitation, etc.) different, the corresponding output The torque is also different. For three-phase stepper motors, the magnitude of the output torque does not change for single-phase and two-phase excitations, and only the angle changes.

Two-phase: The negative sign in Equation (5) and Equation (6) indicates that the winding is reversely energized. From Equations (4) and (6), it can be seen that the static peak torque obtained by the two-phase excitation is about 1.62 times the single-phase excitation peak, while the maximum static peak torque during the three-phase excitation is 2.62 times that of the single-phase excitation (four The phase-on output torque is reduced instead. Therefore, the stepper motor driver designed by the author uses three-phase excitation, which can make full use of the magnetic core capacity, increase the output torque, and enhance the load capacity of the stepper motor, especially the high-frequency load capability.

The five-phase hybrid stepping motor coil winding method has two types of star and pentagonal connection, but for the pentagonal connection method, three-phase excitation cannot be realized, so the star connection method is used.

From equations (2) and (3), it is clear that the above conclusions can be obtained.

For five-phase stepper motors, the situation is different.

Single-phase: two-phase: 2.2 star connection maximum output torque switching sequence converts the three-phase excitation maximum output torque method into the switching sequence of the upper and lower arms of the five-phase inverter bridge, and then controls the five-phase bridge according to this sequence. The three-phase excitation maximum torque output can be realized. Stepper motor windings are arranged in the order as shown. Switch capital letters in the figure indicate positive phase windings, and lower case letters represent inverting windings. It can be seen that when the adjacent three phases are turned on (capital letters indicate positive energization, and lowercase letters indicate reverse energization), it can be seen from Expression (6) that the output torque is maximum at this time. Therefore, the three-phase excitation ten-shot operation can be pushed out from the middle, and the lower case letter indicates that the lower arm is opened).

Stepper motor winding sequence 3 stepper motor driver hardware circuit design Based on the above analysis, the author designed an improved stepper motor driver based on 89C51 microcontroller. The driver hardware circuit, such as listening to |2, is compatible with the input and output of the existing driver and can directly replace the existing stepper motor driver. No power section is shown. The driver is powered by a single parent-frequency 220V power supply. The power supply for the control circuit is provided by the transformer output. The working voltage of the 110BYG550 series stepper motor is 80300V. The output voltage of the 220V AC is not controlled after the full-bridge rectification. It is about 311V, so the main power supply needs to be provided after the chopper circuit is stepped down.

Five-phase inverter bridge improved stepper motor driver hardware circuit diagram The motor driver software consists of a main program, a CP interrupt service routine, and a timer interrupt service routine. The main program mainly realizes the initialization of the interrupt control register, the setting of the timer working mode and the interruption of the upper arm switch and the lower arm switch. Therefore, the upper and lower arm drive circuits need to be designed separately: the upper arm drive circuit accepts the given The control signal is amplified by the amplifying circuit and then driven by the high-frequency pulse transformer to drive the upper arm switch tube; the lower arm drive circuit receives the given control signal, and the optocoupler isolates the amplifying circuit to drive the lower arm switch tube. In the driving circuit, the upper bridge arm drive circuit design is a key technical problem. The author uses a non-gate 74HC04 to connect the resistor and capacitor to form an oscillator to generate high-frequency oscillations. The NAND gate control output drives the high-frequency pulse transformer, and the transformer output passes through the full-bridge rectification. Get a DC voltage to drive the switch.

Five-phase inverter bridge meter adopts three-phase excitation PWM output mode, so that the output torque is large, which can not only approximate the constant current, but also lock the torque under the condition of no pulse for a long time. For the potential load, there is no FREE pulse matching. The driver also works well in this case.

The improved driver has the following improvements over the existing driver: Increased cost based on enhanced performance.

220V power supply, eliminating the need for transformers, lowering operating costs, and ease of use.

The use of three-phase excitation increases the output torque and increases the output capacity.

Using software-timed PWM output, it is possible to approximate a constant current and safely lock the torque when there is no pulse.

4 system software design On the basis of hardware, use C language to design the system software 13|, step enable to prohibit offline query and other functions, CP interrupt service subroutine to achieve partial address operation, check the switch sequence table output control pulse and restart timing The device clears the IE1 flag and other functions. The timer interrupt service routine mainly implements the PWM control function. The flow of the main program and the CP interrupt service subroutine is as shown in the figure. The timed interrupt service subroutine is relatively simple, so the flowchart is not given.

5 Conclusion The improved stepper motor driver has greatly improved performance compared to the existing stepper motor driver. The low frequency torque is stable and the high frequency output torque is large. This driver has been successfully used in computerized embroidery machine systems to drive the 110BYG550 series of five-phase hybrid stepper motors. The driver's production cost is also lower than that of the existing stepper motor driver, which not only reduces the cost of the embroidery machine but also improves the quality of the embroidery.

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