CN109474202B - Self-calibrating ultrasonic motor step control system and method - Google Patents

Abstract

The invention discloses a self-correcting ultrasonic motor step control system and method. A single-phase driving voltage of a certain frequency is applied to the motor, and the rotor is driven to rotate through the radial vibration of piezoelectric ceramics; the elasticity is judged according to whether a certain fluctuation occurs in the sampling current. Whether the blade is stuck in the positioning slot. If the sampling current fluctuates, it means that the elastic blade is stuck in the positioning slot. At this time, the driving voltage is reduced to zero to ensure that the motor completes the stepping motion; the motor stops running for a certain period of time according to the demand; apply the driving voltage, The elastic blade breaks away from the positioning slot and continues to rotate, and the motor can continue to run stably to the next positioning slot. The control system of the present invention uses the sampling resistor as the feedback element to form a closed-loop loop, so that the self-correcting stepping ultrasonic motor can realize stable stepping operation; compared with the open-loop control, the closed-loop feedback control is accurate and flexible, and can be changed through the host computer. The time interval in which the stepper runs.

Description

Self-calibrating ultrasonic motor step control system and method

technical field

The invention belongs to the technical field of ultrasonic motor control, in particular to a self-correcting ultrasonic motor step control system and method.

Background technique

As a new type of motor, ultrasonic motor has the advantages of low speed, high torque, fast action response, self-locking when power off, no noise, no electromagnetic interference, etc. It is widely used in aerospace, precision instruments, robot joint drive and other fields. Ultrasonic motors have flexible structural design and various design forms. According to different working modes and driving principles, ultrasonic motors with different forms and functions can be designed.

At present, the step control of the ultrasonic motor needs to be connected to the position sensor to form a closed loop for position information feedback. The disadvantage is that it will inevitably cause cumulative errors during multi-step operation, and the complex feedback and control devices limit the development of equipment miniaturization. The self-calibrating stepping ultrasonic motor does not require a complex feedback system to achieve stepping operation without cumulative error. A reasonable control method can make the motor run stably, output large torque, and obtain output performance and reliability that can reach the level of electromagnetic motors. .

Contents of the invention

Purpose of the invention: In view of the above problems, the present invention proposes a self-correcting ultrasonic motor step control system and method, which forms a closed-loop loop through the feedback current, and realizes the step operation of the ultrasonic motor without cumulative error.

Technical solution: In order to achieve the purpose of the present invention, the technical solution adopted in the present invention is: a self-correcting ultrasonic motor step control system, including a host computer, a communication module, a control module, a drive module, a self-correcting ultrasonic motor and Feedback module; the upper computer is used to issue instructions and send them to the control module through the communication module; after the control module receives the instructions, it adjusts the voltage applied to the motor through the drive module; the drive voltage is applied to the motor, the motor rotates, and the motor current is controlled by the feedback module Collect and feed back to the control module; the elastic blade of the motor is stuck into the positioning slot, the motor stops rotating, and the current fluctuates, which is fed back to the control module to reduce the voltage applied to the motor to zero; after the positioning time set by the host computer, the control module Apply the driving voltage to the motor again, the elastic blade rushes out of the positioning slot, and the motor starts to run stably to the next positioning slot.

Further, the self-correcting ultrasonic motor is a standing wave ultrasonic motor with radial vibration; the motor stator includes a piezoelectric ceramic ring, a metal ring and elastic blades, the metal ring is outside the piezoelectric ceramic ring, and the elastic blades are uniformly welded on the metal Outside the ring; the rotor of the motor is cylindrical, and there are a number of positioning grooves inside along the circumferential direction, and the width, depth and shape of the positioning grooves are the same.

Further, the control module is a DSP controller, and the modules used include an SCI module, a PWM module, and an analog-to-digital conversion module; the SCI module is a serial communication interface module for receiving host computer signals; the PWM module adjusts the PWM wave duty cycle To adjust the voltage applied to the motor; the analog-to-digital conversion module receives the signal from the feedback module.

Further, the communication module includes an RS232 interface and a level conversion chip; the RS232 receives signals from the host computer and sends them to the control module through the level conversion chip.

Further, the drive module is a push-pull switch drive circuit, which inverts the DC signal into an AC signal, and boosts the low-voltage signal into a high-voltage signal capable of driving the motor.

Further, the feedback module is a sampling circuit that performs current sampling to obtain a voltage value that is fed back to the analog-to-digital conversion module.

A self-calibrating ultrasonic motor step control method, comprising the steps of:

(1) The upper computer sends a command, through the RS232 interface, through the level conversion chip to the DSP controller to start the signal, and set the positioning time of the ultrasonic motor;

(2) The SCI module of the DSP controller receives instructions from the host computer, and the PWM module outputs PWM waves, and applies a driving voltage to the ultrasonic motor through the push-pull switch driving circuit to drive the motor to rotate;

(3) When the elastic blade is stuck into the positioning slot, the motor stops rotating, the current fluctuates, and the sampling circuit obtains a fluctuating signal, which is fed back to the analog-to-digital conversion module;

(4) The DSP controller receives the feedback signal, adjusts the duty cycle of the PWM module, and reduces the applied voltage to zero to ensure that the motor completes the stepping motion;

(5) After the positioning time set by the host computer, reapply the drive voltage to the motor, the elastic blade rushes out of the spring slot, and the motor starts to run stably to the next positioning slot.

Beneficial effects: Compared with ordinary ultrasonic motors, the self-correcting ultrasonic motor of the present invention has a special mechanical structure design, and can realize stepping operation without cumulative error without the need for position sensors to feed back position information; the closed-loop feedback circuit is formed by using sampling resistors, The circuit is simple, the cost is reduced, and it is conducive to miniaturization design; the motor voltage is adjusted by adjusting the duty cycle of the PWM wave output by the DSP control chip, so as to realize the shutdown and start of the motor, and avoid out-of-step or multi-step failure caused by switching working modes Question: Compared with open-loop control, closed-loop feedback control is precise and flexible, and the time interval in stepping operation can be changed through the host computer.

Description of drawings

Fig. 1 is the structure diagram of the stator and rotor of the self-correcting type ultrasonic motor of the present invention;

Fig. 2 is a structural diagram of the step control system of the present invention;

Fig. 3 is a circuit diagram of the driving module of the present invention.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 1, the self-correcting ultrasonic motor according to the present invention has a stator structure composed of a metal elastic body, a piezoelectric ceramic ring and elastic blades, the metal ring is outside the piezoelectric ceramic ring, and the elastic blades are evenly distributed by welding outside the metal elastomer. The rotor structure is cylindrical, and there are multiple positioning grooves with equal width, shape and size inside the rotor. The key to the stepping operation of the motor is that the elastic blades run to the groove, and the rotor stops rotating due to the positioning of the groove to complete the stepping motion.

As shown in Figure 2, the self-calibrating ultrasonic motor step control system based on current detection includes a host computer, a communication module, a control module, a drive module, a self-calibrating ultrasonic motor and a feedback module.

The communication module includes RS232 interface and level conversion chip. The port of the GPIO pin of the DSP controller is TTL level, but the RS232 interface uses positive and negative voltages to indicate the logic state, which is different from TTL’s high and low levels to indicate the logic state, so a level conversion chip is required for logic conversion to realize GPIO output The compatibility between the level and the RS232 signal level realizes the data reception and transmission between DSP and host computer.

The control module is DSP chip TMS320F28335, and the used modules include SCI module, PWM module and analog-to-digital (A/D) conversion module. The SCI module is a serial communication interface module used to receive signals from the host computer. The PWM module outputs PWM waves, and adjusts the voltage applied to the motor by adjusting the duty cycle of the PWM waves. An analog-to-digital (A/D) conversion module receives signals from the feedback module.

The drive module is a push-pull switch drive circuit, which inverts the DC signal into an AC signal and boosts the low-voltage signal into a high-voltage signal capable of driving the motor. As shown in FIG. 3 , the switching tubes Q1 and Q2 are turned on alternately, and an alternating voltage with opposite phases is generated at both ends of the primary side winding of the transformer.

The feedback module is a sampling circuit. The sampling resistor is used for current sampling, and the obtained voltage value is fed back to the analog-to-digital (A/D) conversion module of the DSP controller.

Self-calibration ultrasonic motor step control method, the specific control method in one cycle:

(1) The host computer issues a command, sends a start signal to the DSP through the RS232 interface, and sets the positioning time of the ultrasonic motor;

(2) The SCI module of the DSP controller receives instructions from the host computer, and the PWM module outputs PWM waves, and applies a driving voltage with a peak value of 100V to the ultrasonic motor through the push-pull switch driving circuit to drive the motor to rotate.

The motor is driven by a single-phase voltage, the piezoelectric ceramic produces first-order radial vibration, and the elastic blade produces extrusion deformation, which drives the rotor to rotate stably through friction.

The sampling circuit feeds back the current value during normal operation to the analog-to-digital conversion module of the DSP controller, and the current value is about 110mA;

(3) When the elastic blade is stuck into the positioning groove, due to the action of the positioning groove, the rotor stops rotating;

(4) The elastic blade is stuck into the positioning slot, and the motor current fluctuates, and the fluctuating current value is about 175mA, which is about 1.5-1.6 times of the current value during normal operation.

The sampling current is sampled by the sampling resistor and passed to the DSP analog-to-digital (A/D) conversion module.

(5) The DSP controller receives the signal, the PWM module adjusts the duty cycle, and the applied voltage drops to zero to prevent the motor from out-of-step or multi-step operation and ensure that the motor completes the step motion;

(6) After the positioning time set by the host computer is set, the driving voltage is applied to the motor, the elastic blade rushes out of the positioning slot, and the motor starts to run stably to the next positioning slot.

In summary, the stepping control based on current detection is carried out on the self-correcting stepping motor, so that the motor can perform stepping operation under closed-loop control. This control method enables the motor to perform stable and precise stepping operation, and the stepping interval can be adjusted through the host computer.

Claims (6)

1. A self-correcting type ultrasonic motor step control system is characterized in that it comprises a host computer, a communication module, a control module, a drive module, a self-correcting type ultrasonic motor and a feedback module; The upper computer is used to issue instructions and send them to the control module through the communication module; after the control module receives the instructions, it adjusts the voltage applied to the motor through the drive module; Apply driving voltage to the motor, the motor rotates, and the motor current is collected by the feedback module and fed back to the control module; The elastic blade of the motor snaps into the positioning slot, the motor stops rotating, and the current fluctuates, which is fed back to the control module to reduce the voltage applied to the motor to zero; After the positioning time set by the host computer, the control module reapplies the driving voltage to the motor, the elastic blade rushes out of the positioning slot, and the motor starts to run stably to the next positioning slot; The self-correcting ultrasonic motor is a standing wave ultrasonic motor with radial vibration; the motor stator includes a piezoelectric ceramic ring, a metal ring and elastic blades, the metal ring is outside the piezoelectric ceramic ring, and the elastic blades are evenly welded outside the metal ring; The rotor of the motor is cylindrical, and there are several positioning slots inside along the circumferential direction, and the width, depth and shape of the positioning slots are the same. 2. self-calibration type ultrasonic motor stepping control system according to claim 1, is characterized in that, described control module is a DSP controller, and using module comprises SCI module, PWM module and analog-to-digital conversion module; SCI module is a serial port The communication interface module is used to receive the signal from the host computer; the PWM module adjusts the voltage applied to the motor by adjusting the duty cycle of the PWM wave; the analog-to-digital conversion module receives the signal from the feedback module. 3. The self-calibrating ultrasonic motor step control system according to claim 1, wherein the communication module includes an RS232 interface and a level conversion chip; RS232 receives the signal from the host computer and sends it to the control unit through the level conversion chip module. 4. The self-calibrating ultrasonic motor step control system according to claim 1, wherein the drive module is a push-pull switch drive circuit, which inverts a DC signal into an AC signal and boosts a low-voltage signal It is a high-voltage signal capable of driving a motor. 5 . The self-calibrating ultrasonic motor step control system according to claim 1 , wherein the feedback module is a sampling circuit that performs current sampling to obtain a voltage value that is fed back to the control module. 6 . 6. A self-correcting type ultrasonic motor stepping control method, is characterized in that, comprises the steps: (1) The upper computer sends a command, through the RS232 interface, through the level conversion chip to the DSP controller to start the signal, and set the positioning time of the self-correcting ultrasonic motor; The self-correcting ultrasonic motor is a standing wave ultrasonic motor with radial vibration; the motor stator includes a piezoelectric ceramic ring, a metal ring and elastic blades, the metal ring is outside the piezoelectric ceramic ring, and the elastic blades are evenly welded outside the metal ring; The rotor of the motor is cylindrical, and there are several positioning slots inside along the circumferential direction, and the width, depth and shape of the positioning slots are the same; (2) The SCI module of the DSP controller receives instructions from the host computer, and the PWM module outputs PWM waves, and applies a driving voltage to the self-correcting ultrasonic motor through the push-pull switch driving circuit to drive the motor to rotate; (3) When the elastic blade is stuck into the positioning slot, the motor stops rotating, the current fluctuates, and the sampling circuit obtains a fluctuating signal, which is fed back to the analog-to-digital conversion module; (4) The DSP controller receives the feedback signal, adjusts the duty cycle of the PWM module, and reduces the applied voltage to zero to ensure that the motor completes the stepping motion; (5) After the positioning time set by the host computer is set, the driving voltage is applied to the motor again, the elastic blade rushes out of the positioning slot, and the motor starts to run stably to the next positioning slot.