CN111245291A - Cylindrical stator ultrasonic motor transformerless LLC drive control circuit and method - Google Patents

Abstract

The invention discloses a cylindrical stator ultrasonic motor transformerless LLC drive control circuit and a cylindrical stator ultrasonic motor transformerless LLC drive control method. The input power supply of the driving circuit is a direct current source, and a direct current booster circuit is added into the post-stage circuit to boost the initial voltage of the post-stage circuit; a switching-off device MOSFET is adopted in the circuit, and a driving signal is changed into two paths of signals with 90-degree phase difference through a phase modulation circuit and is transmitted to an MOSFET driving chip to control the switching-off of the two paths of driving circuits. The circuit is provided with a feedback loop, the output voltage is sampled, the sampled signal is compared with a reference value, the duty ratio parameter is adjusted, and the voltage at two ends of the motor is ensured to meet the requirement of driving voltage. The invention does not need a booster transformer, greatly reduces the volume of the driving control board, and is suitable for special application occasions sensitive to the space size.

Description

A transformerless LLC drive control circuit and method for a cylindrical stator ultrasonic motor

technical field

The invention relates to a cylindrical ultrasonic motor technology, in particular to a transformerless LLC drive control circuit and method for a cylindrical stator ultrasonic motor.

Background technique

As a new type of motor, ultrasonic motor has the advantages of low speed and 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. The ultrasonic motor has 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 ultrasonic motor drive control needs to use a transformer for signal amplification and filtering. Most of the pulse transformers and power tubes are used to form a boost and inverter circuit. The combination of the characteristic parameters plays the role of a low-pass filter circuit and realizes boosting at the same time. This kind of circuit has been successfully used in the drive of various ultrasonic motors, and has good stability and reliability. However, the number of circuit components is large and the volume is relatively large, which is not conducive to the development trend of the miniaturization of the ultrasonic motor, and restricts the application of the ultrasonic motor in other related fields.

SUMMARY OF THE INVENTION

Purpose of the invention: In view of the above problems, the present invention proposes a transformerless LLC drive control circuit and method for a cylindrical stator ultrasonic motor. Through the capacitive characteristics of the ultrasonic motor itself, a matching oscillating inductance is added to realize transformerless drive control and reduce the volume of the drive control circuit. Expand the scope of use of the device.

Technical scheme: In order to achieve the purpose of the present invention, the technical scheme adopted in the present invention is: a transformerless LLC drive control circuit for a cylindrical stator ultrasonic motor, including a DC power supply, an LLC oscillation booster circuit, a cylindrical stator ultrasonic motor, and a voltage measurement circuit and PID controller; the DC power supply supplies power to the LLC oscillating booster circuit, the cylindrical ultrasonic motor, the voltage measurement circuit and the PID controller; the LLC oscillating booster circuit includes switching devices, which control the on-off of the circuit to generate a driving voltage at both ends of the motor; The voltage measurement circuit samples and measures the voltage at both ends of the motor, and inputs the measured voltage feedback to the PID controller; the PID controller receives the voltage feedback measured by the voltage measurement circuit, adjusts the driving signal of the switching device, and adjusts the motor driving voltage.

Further, the LLC oscillating boost circuit includes a charging inductor, an oscillating inductor, an oscillating capacitor and a switching device; the charging inductor is connected to the DC power supply, and is connected to the switching device to form a loop; the oscillating inductor and the oscillating capacitor are connected and connected in parallel to both ends of the switching device; The oscillation capacitor is connected in parallel with the motor.

Further, when the switching device is in the off or on state, the LLC oscillating booster circuit is in the charging or oscillating state.

Further, the cylindrical stator ultrasonic motor includes a stator and a rotor; the stator includes a cylinder, a piezoelectric ceramic sheet, a matching block and a base, and the piezoelectric ceramic sheet is clamped by a threaded structure between the matching block and the base to form a Lanjiewen. Vibrator structure; the rotor is in hard frictional contact with the stator cylinder through the preload spring on the top of the motor. Using the inverse piezoelectric effect of piezoelectric ceramics, the cylinder generates first-order free-free bending vibration, and the particles at the top of the cylinder generate elliptical vibration, relying on friction. force the rotor to turn.

A transformerless LLC drive control method for a cylindrical stator ultrasonic motor, comprising the steps of:

(1) Turn on the DC power supply;

(2) Control the switching device of the LLC oscillating booster circuit to turn off according to the initial set duty ratio and frequency, and the LLC oscillating booster circuit enters the initial oscillation state;

(3) The stored energy of the inductance increases, the voltage peak value across the motor increases, and the motor enters the running state;

(4) The voltage measurement circuit measures the voltage at both ends of the motor in real time, and sends the signal to the PID controller. After analysis and adjustment, the duty cycle and frequency of the driving signal of the switching device are adjusted, and the voltage at the motor terminal is adjusted.

Further, in the step 4, the driving signal is divided into two phases, A and B, with a time phase difference of 90°.

Beneficial effects: Compared with the ordinary traveling wave ultrasonic motor, the cylindrical ultrasonic motor of the present invention has a special mechanical structure design, and does not have strict requirements on the sinusoidality of the driving power waveform. The initial input DC voltage meets the motor drive voltage requirement.

The transformerless LLC drive control technology of the present invention uses the capacitive characteristics of the ultrasonic motor itself, adds matching oscillating inductance, and the oscillation boosting method avoids the use of a booster transformer, the circuit structure is simpler, the volume of the drive control circuit is further reduced, and the use range of the device is expanded. .

Description of drawings

1 is a block diagram of a transformerless LLC drive control circuit of a cylindrical stator ultrasonic motor of the present invention;

Fig. 2 is the structure diagram of the cylindrical stator ultrasonic motor of the present invention;

Fig. 3 is the main circuit diagram of the drive system of the present invention;

Fig. 4 is the equivalent circuit diagram of LLC oscillation circuit MOSFET opening of the present invention;

Fig. 5 is the equivalent circuit diagram of LLC oscillation circuit MOSFET turn-off of the present invention;

FIG. 6 is the turn-on signal of the two-phase MOSFETs of A and B of the driving circuit of the present invention, and D=50%.

Detailed ways

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

As shown in Figure 1, the transformerless LLC drive control circuit of the cylindrical stator ultrasonic motor of the present invention includes a DC power supply, an LLC oscillation boost circuit, a cylindrical stator ultrasonic motor, a voltage measurement circuit and a PID controller. The DC power supply powers the LLC oscillator booster circuit, the cylindrical ultrasonic motor, the voltage measurement circuit and the PID controller. The LLC oscillating booster circuit includes a switching device, which controls the on-off of the circuit to generate a driving voltage at both ends of the motor. The voltage measurement circuit samples and measures the voltage at both ends of the motor, and inputs the measured voltage feedback into the PID controller to ensure that the gain of the drive circuit is stable within a certain range and meets the needs of the normal operation of the motor. The PID controller receives the voltage feedback measured by the voltage measurement circuit, adjusts the driving signal of the switching device, and adjusts the driving voltage of the motor. The driving signal is divided into two phases, A and B, with a time phase difference of 90°.

As shown in FIG. 2 , in the cylindrical stator ultrasonic motor of the present invention, the length of the motor is 22 mm, and the diameter of the cylindrical stator is 10 mm. The cylindrical stator ultrasonic motor includes a stator and a rotor. The motor stator includes a cylinder, a piezoelectric ceramic sheet, a matching block and a base. The piezoelectric ceramic sheet is clamped by a threaded structure between the matching block and the base to form a Lanjiewen oscillator structure; there are four piezoelectric ceramic sheets, A , B two phase each two pieces. The rotor of the motor is in hard frictional contact with the stator cylinder through the preload spring on the top of the motor. Using the inverse piezoelectric effect of piezoelectric ceramics, the cylinder generates first-order free-free bending vibration, and the particles at the top of the cylinder generate elliptical vibration, which is driven by friction. The rotor turns.

As shown in Figure 3, the two-phase drive circuits of motors A and B are connected in parallel with each other without interfering with each other, and the energy is provided by the same DC power supply. Using the capacitive load characteristics of the cylindrical ultrasonic motor itself, the motor body is used as part of the oscillating circuit, and matching inductors and matching capacitors are added to form an oscillating LLC drive circuit, which generates a sinusoidal oscillating alternating voltage on the equivalent circuit of the motor. The drive motor runs.

The LLC oscillating boost circuit includes a charging inductor L ₁ , an oscillating inductor L ₂ , an oscillating capacitor C ₂ and a switching device; the charging inductor is connected to the DC power supply and is connected to the switching device to form a loop; the oscillating inductor and the oscillating capacitor are connected and connected in parallel to both ends of the switching device ; The oscillation capacitor is connected in parallel with the motor. When the switching device is in the off or on state, the LLC oscillating boost circuit is in a charging or oscillating state.

The charging inductance L ₁ , the oscillating inductance L ₂ and the oscillating capacitor C ₂ are actually determined according to the parameters of the A and B two-phase single-phase circuits. The parallel circuits of C _m and R _m are the electrical parameters of the motor itself, which can be obtained by experimental methods. The value of the oscillation capacitor C ₂ is 100C _m , and its function is to eliminate the influence on the motor drive circuit caused by the change of the parameter C _m of the motor itself during the operation of the motor. The oscillating inductance L ₂ satisfies the following relationship:

Among them, f is the switching frequency of the MOSFET, and the value of the charging inductance L ₁ is about 0.1L ₂ to 10L ₂ .

The main circuit of the drive system of the present invention operates in two different states according to the on-off condition of the MOSFET. FIG. 4 is an equivalent circuit diagram of the MOSFET being turned on, and FIG.

When the power tube is turned on, L ₁ and the DC power supply form an energy storage circuit; L ₂ , C ₂ , C _m , R _m form a damped oscillation circuit, which utilizes the energy storage and resistance in L ₂ and C ₂ when the MOSFET is turned off R _m cooperates to complete the damping oscillation process of one cycle to achieve the purpose of improving the waveform.

When the power tube is turned off, the circuit works in the boosting state of BOOST, and the energy storage voltage _on L1 and the DC power supply are simultaneously applied to the output end of the circuit, thereby increasing the circuit output voltage at the moment when the MOSFET is turned off. Since the MOSFET works in the off state for a very short time, the influence of the series oscillating circuit composed of L ₁ , L ₂ , C _m and R _m during this time period is negligible, and this process is simplified as a direct current _The boost process in which the power supply and L1 work together.

During the operation of the circuit, the breaking frequency of the power tube determines the timing of boosting the boost circuit; the damping oscillation frequencies of L ₂ and C ₂ determine the frequency of the output voltage. The peak value of the output voltage of the damping oscillation circuit decreases with the passage of time according to the negative exponential law. The booster circuit of BOOST should supplement the voltage attenuation brought by the damping oscillation at the appropriate time, and select the appropriate boosting time of BOOST to match the damping oscillation frequency. The voltage decreases once every time the voltage oscillates. The optimal timing of pressurization is selected as the peak value of u(t) after the first half-cycle zero-crossing point of the secondary half cycle, so as to ensure that the peak value loss of the voltage is minimized or even remains unchanged.

The voltage measurement circuit measures the output terminal voltage of the driving circuit, which is the driving voltage applied to the A-phase or B-phase of the motor, and measures the voltage value by means of small resistance pressure measurement. sent to the PID control circuit.

The PID control circuit receives the motor drive voltage data measured by the voltage measurement circuit, and adjusts the MOSFET drive frequency or duty cycle according to the motor drive voltage threshold measured in advance through experiments. The drive signal is shown in Figure 6. It can be seen from the theoretical analysis that the frequency of the motor itself will not change significantly during the operation, so the duty cycle is preferentially adjusted. If the duty cycle is too high or too low, the drive circuit may fail, so the duty cycle determines the duty cycle range based on simulation and actual implementation.

Using the oscillation mode to drive the cylindrical ultrasonic motor can eliminate the dependence of the traditional drive circuit on the step-up transformer and reduce the size of the drive circuit.

The transformerless LLC drive control method for a cylindrical stator ultrasonic motor according to the present invention comprises the steps of:

(1) Connect the DC power supply to provide an energy source for the system;

(2) Control the switching device of the LLC oscillating booster circuit to turn off according to the initial set duty ratio and frequency, and the LLC oscillating booster circuit enters the initial oscillation state;

(3) As the energy stored in the inductance continues to increase, the peak value of the motor terminal voltage also continues to increase, and the motor gradually enters the running state;

(4) With the operation of the motor, the self-heating and other factors cause the frequency of the motor to change, and the driving frequency also needs to be changed. The voltage measurement circuit measures the voltage at both ends of the motor in real time, and sends the signal to the PID controller. After analysis and adjustment, the duty cycle and frequency of the driving signal of the switching device are adjusted, and the voltage at the motor terminal is adjusted.

Claims (6)

1. a cylindrical stator ultrasonic motor transformerless LLC drive control circuit, is characterized in that, comprises DC power supply, LLC oscillation boost circuit, cylindrical stator ultrasonic motor, voltage measurement circuit and PID controller; DC power supply is LLC oscillation boost circuit , Cylindrical ultrasonic motor, voltage measurement circuit and PID controller power supply; The LLC oscillating boost circuit includes a switching device, which controls the on-off of the circuit to generate a driving voltage at both ends of the motor; The voltage measurement circuit samples and measures the voltage at both ends of the motor, and inputs the measured voltage feedback to the PID controller; the PID controller receives the voltage feedback measured by the voltage measurement circuit, adjusts the driving signal of the switching device, and adjusts the motor driving voltage. 2. The transformerless LLC drive control circuit for a cylindrical stator ultrasonic motor according to claim 1, wherein the LLC oscillation boost circuit comprises a charging inductance (L ₁ ), an oscillation inductance (L ₂ ), an oscillation capacitor (C ₂ ) and the switching device; the charging inductor is connected to the DC power supply, and is connected to the switching device to form a loop; the oscillating inductor and the oscillating capacitor are connected and connected in parallel to both ends of the switching device; the oscillating capacitor is connected in parallel with the motor. 3 . The transformerless LLC drive control circuit for a cylindrical stator ultrasonic motor according to claim 1 , wherein when the switching device is in an off or on state, the LLC oscillating booster circuit is in a charging or oscillating state. 4 . 4. The transformerless LLC drive control circuit of cylindrical stator ultrasonic motor according to claim 1, is characterized in that, described cylindrical stator ultrasonic motor comprises stator and rotor; The stator includes a cylinder, a piezoelectric ceramic sheet, a matching block and a base, and the piezoelectric ceramic sheet is clamped by a threaded structure between the matching block and the base to form a Lanjiewen oscillator structure; The rotor is in hard frictional contact with the stator cylinder through the preloaded spring at the top of the motor. Using the inverse piezoelectric effect of piezoelectric ceramics, the cylinder generates first-order free-free bending vibration, and the particles at the top of the cylinder generate elliptical vibration, which pushes the rotor by friction. turn. 5. a cylindrical stator ultrasonic motor transformerless LLC drive control method, based on the cylindrical stator ultrasonic motor transformerless LLC drive control circuit described in claim 1-4, is characterized in that, comprises the steps: (1) Turn on the DC power supply; (2) Control the switching device of the LLC oscillating booster circuit to turn off according to the initial set duty ratio and frequency, and the LLC oscillating booster circuit enters the initial oscillation state; (3) The stored energy of the inductance increases, the voltage peak value across the motor increases, and the motor enters the running state; (4) The voltage measurement circuit measures the voltage at both ends of the motor in real time, and sends the signal to the PID controller. After analysis and adjustment, the duty cycle and frequency of the driving signal of the switching device are adjusted, and the voltage at the motor terminal is adjusted. 6 . The transformerless LLC drive control method for a cylindrical stator ultrasonic motor according to claim 1 , wherein, in the step 4, the drive signal is divided into two phases, A and B, and the time phase differs by 90°. 7 .

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