CN111245291B

CN111245291B - A transformerless LLC drive control circuit and method for a cylindrical stator ultrasonic motor

Info

Publication number: CN111245291B
Application number: CN202010164549.XA
Authority: CN
Inventors: 徐志科; 张淼; 杜龙; 冷静雯; 汪涛; 金龙
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2020-03-11
Filing date: 2020-03-11
Publication date: 2021-10-19
Anticipated expiration: 2040-03-11
Also published as: CN111245291A

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

Cylindrical stator ultrasonic motor transformerless LLC drive control circuit and method

Technical Field

The invention relates to the technology of a cylindrical ultrasonic motor, in particular to a transformerless LLC (logical Link control) drive control circuit and a transformerless LLC drive control method for a cylindrical stator ultrasonic motor.

Background

The ultrasonic motor serving as a novel motor has the advantages of low speed, large torque, quick action response, power failure self-locking, no noise, no electromagnetic interference and the like, and is widely applied to the fields of aerospace, precise instruments and meters, robot joint driving and the like. The ultrasonic motor has flexible structural design and various design forms, and can be designed into ultrasonic motors with different forms and functions according to different working modes and driving principles.

At present, a transformer is required to amplify and filter signals for ultrasonic motor drive control, a boosting and inverting circuit is mostly formed by a pulse transformer and a power tube, leakage inductance parameters are directly utilized by analyzing an electrical model of the pulse transformer, the leakage inductance parameters are matched with capacitive parameters of an ultrasonic motor to play a role of a low-pass filter circuit, and boosting is realized at the same time. The circuit is successfully used for driving various ultrasonic motors and has good stability and reliability. However, the circuit elements are large in number and large in size, which is not favorable for the development trend of miniaturization of the ultrasonic motor, and restricts the application of the ultrasonic motor in other related fields.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the problems, the invention provides a cylindrical stator ultrasonic motor transformerless LLC drive control circuit and a cylindrical stator ultrasonic motor transformerless LLC drive control method.

The technical scheme is as follows: in order to realize the purpose of the invention, the technical scheme adopted by the invention is as follows: a cylindrical stator ultrasonic motor transformerless LLC drive control circuit comprises a direct-current power supply, an LLC oscillation boosting circuit, a cylindrical stator ultrasonic motor, a voltage measuring circuit and a PID controller; the direct current power supply supplies power to the LLC oscillation booster circuit, the cylindrical ultrasonic motor, the voltage measuring circuit and the PID controller; the LLC oscillation booster circuit comprises a switching device, controls the on-off of the circuit and generates driving voltage at two ends of the motor; the voltage measuring circuit samples and measures the voltages at two ends of the motor and inputs the measured voltage feedback quantity into the PID controller; and the PID controller receives the voltage feedback quantity measured by the voltage measuring circuit, adjusts the driving signal of the switching device and adjusts the driving voltage of the motor.

Further, the LLC oscillating voltage boost circuit includes a charging inductor, an oscillating capacitor, and a switching device; the charging inductor is connected with a direct current power supply and a switching device to form a loop; the oscillating inductor and the oscillating capacitor are connected and connected in parallel at two ends of the switching device; the oscillating capacitor is connected in parallel with the motor.

Further, the LLC oscillation boost circuit is in a charging or oscillation state when the switching device is in an off or on state.

Further, the cylindrical stator ultrasonic motor comprises a stator and a rotor; the stator comprises a cylinder, a piezoelectric ceramic piece, a matching block and a base, wherein the piezoelectric ceramic piece is clamped between the matching block and the base through a thread structure to form a Langewen vibrator structure; the rotor is in hard friction contact with the stator cylinder through a pre-tightening spring on the top of the motor, the first-order free-free bending vibration is generated on the cylinder by utilizing the inverse piezoelectric effect of the piezoelectric ceramic, and the mass point on the top of the cylinder generates elliptical vibration and pushes the rotor to rotate according to the friction force.

A cylindrical stator ultrasonic motor transformerless LLC drive control method comprises the following steps:

(1) switching on a direct current power supply;

(2) controlling a switching device of the LLC oscillation boosting circuit to be switched on and off according to the initially set duty ratio and frequency, and enabling the LLC oscillation boosting circuit to enter an initial oscillation state;

(3) the stored energy of the inductor is increased, the voltage peak values at two ends of the motor are improved, and the motor enters a running state;

(4) the voltage measuring circuit measures the voltage at two ends of the motor in real time, sends signals to the PID controller, and adjusts the voltage at the end of the motor by analyzing and adjusting the duty ratio and frequency of driving signals of the switching device.

Further, in step 4, the driving signal is divided into A, B two phases, and the phases of the driving signal are different by 90 °.

Has the advantages that: compared with the common traveling wave type ultrasonic motor, the cylindrical ultrasonic motor has special mechanical structure design and has no strict requirement on the sine of the waveform of a driving power supply, and the overvoltage is generated on the motor body in an oscillation boosting mode and is higher than the initial input direct current voltage, so that the requirement on the driving voltage of the motor is met.

According to the drive control technology of the LLC without the transformer, the matched oscillation inductor is added through the capacitive characteristics of the ultrasonic motor, the use of a step-up transformer is avoided in an oscillation step-up mode, the circuit structure is simpler, the volume of a drive control circuit is further reduced, and the application range of the device is expanded.

Drawings

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

FIG. 2 is a block diagram of a cylindrical stator ultrasonic motor of the present invention;

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

FIG. 4 is a MOSFET turn-on equivalent circuit diagram of the LLC oscillation circuit of the invention;

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

fig. 6 shows a two-phase MOSFET turn-on signal of the present invention driver circuit A, B, where D is 50%.

Detailed Description

The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.

As shown in fig. 1, the LLC driving control circuit of cylindrical stator ultrasonic motor according to the present invention includes a dc power supply, an LLC oscillation boosting circuit, a cylindrical stator ultrasonic motor, a voltage measuring circuit, and a PID controller. And the direct current power supply supplies power to the LLC oscillation booster circuit, the cylindrical ultrasonic motor, the voltage measuring circuit and the PID controller. The LLC oscillation booster circuit comprises a switching device which controls the on-off of the circuit and generates driving voltage at two ends of the motor. The voltage measuring circuit samples and measures the voltages at two ends of the motor, and inputs the measured voltage feedback quantity into the PID controller, so that the gain of the driving circuit is ensured to be stabilized in a certain range, and the normal operation requirement of the motor is met. The PID controller receives the voltage feedback quantity measured by the voltage measuring circuit, adjusts the driving signal of the switching element, and adjusts the driving voltage of the motor, wherein the driving signal is divided into A, B phases, and the time phase difference is 90 degrees.

As shown in FIG. 2, the length of the cylindrical stator ultrasonic motor is 22mm, and the diameter of the cylindrical stator is 10 mm. The cylindrical stator ultrasonic motor comprises a stator and a rotor. The motor stator comprises a cylinder, a piezoelectric ceramic piece, a matching block and a base, wherein the piezoelectric ceramic piece is clamped between the matching block and the base through a thread structure to form a Langewen vibrator structure; the piezoelectric ceramic plate I has four pieces, and A, B two phases are respectively provided. The motor rotor is in hard friction contact with the stator cylinder through a pre-tightening spring on the top of the motor, the first-order free-free bending vibration is generated on the cylinder by utilizing the inverse piezoelectric effect of the piezoelectric ceramic, and the mass point on the top of the cylinder generates elliptical vibration and pushes the rotor to rotate according to the friction force.

As shown in fig. 3, the two-phase driving circuits of the motor A, B are connected in parallel without interfering with each other, and are powered by the same dc power source. The capacitive load characteristic of the cylinder ultrasonic motor is utilized, the motor body is used as a part of an oscillating circuit, a matching inductor and a matching capacitor are added to form an oscillating LLC driving circuit, sinusoidal oscillation alternating voltage is generated on a motor equivalent circuit, and the voltage is utilized to drive the motor to run.

The LLC oscillation booster circuit comprises a charging inductor L₁And an oscillating inductor L₂And an oscillation capacitor C₂And a switching device; the charging inductor is connected with a direct current power supply and a switching device to form a loop; the oscillating inductor and the oscillating capacitor are connected and connected in parallel at two ends of the switching device; the oscillating capacitor is connected in parallel with the motor. When the switching device is in an off or on state, the LLC oscillation boosting circuit is in a charging or oscillation state.

Charging inductor L₁And an oscillating inductor L₂And an oscillating capacitor C₂According to A, B two-phase single-phase circuit parameters. C_m、R_mThe parallel circuit is the electrical parameter of the motor and can be obtained through an experimental method. Oscillation capacitor C₂Value of 100C_mThe function of which is to eliminate the motor parameter C_mThe influence of changes in the operation of the motor on the motor drive circuit. Oscillating inductor L₂Satisfies the following relation:

wherein f is the on-off frequency of the MOSFET and the charging inductance L₁Value of about 0.1L₂～10L₂。

The main circuit of the driving system of the invention works in two different states according to the on-off condition of the MOSFET, figure 4 is an equivalent circuit diagram of the MOSFET on, and figure 5 is an equivalent circuit diagram of the MOSFET off.

When the power tube is conducted, L₁And a direct current power supply form an energy storage loop; l is₂、C₂And C_m、R_mForming a damped oscillation circuit using the period L when the MOSFET is turned off₂And C₂Energy storage and resistance R in_mThe purpose of improving the waveform is achieved by completing a cycle damping oscillation process.

When the power tube is turned off, the circuit works in a BOOST state L₁The stored energy voltage and the direct current power supply are simultaneously applied to the output end of the circuit, so that the output voltage of the circuit at the moment of disconnection of the MOSFET is improved. Since the time that the MOSFET is operated in the OFF state is short, L is set to be equal to L in this period₁、L₂、C_mAnd R_mThe influence brought by the formed series oscillating circuit is ignored, and the process is simplified to be that a direct current power supply and L₁A co-acting boosting process.

In the circuit operation process, the on-off frequency of the power tube determines the pressurization time of the BOOST circuit; l is₂、C₂Determines the frequency of the output voltage. The peak value of the output voltage of the damped oscillation circuit is reduced along with the time-continuation voltage peak value according to a negative exponential law along with the time-lapse. The BOOST circuit should supplement the voltage attenuation caused by the ringing at a proper timing, and select a proper BOOST timing to match the ringing frequency. The voltage decreases once per oscillation. The optimal time of pressurization is selected as the peak value of u (t) after the zero crossing point of the auxiliary half cycle for the first time, and the peak value loss of the voltage is ensured to be minimum or even kept unchanged.

The voltage measuring circuit measures the voltage of the output end of the driving circuit, namely the driving voltage applied to the phase A or the phase B of the motor, measures the voltage value in a small resistance pressure measuring mode, converts the analog quantity into the digital quantity by adopting the A/D conversion module, and transmits the data to the PID control circuit.

The PID control circuit receives the motor driving voltage data measured by the voltage measuring circuit, and adjusts the MOSFET driving frequency or duty ratio according to the motor driving voltage threshold value measured in advance through an experimental manner, and the driving signal is as shown in fig. 6. Theoretical analysis shows that the self frequency of the motor does not change obviously in the running process, so that the duty ratio is preferentially adjusted. The duty ratio is too high or too low, which may cause the failure of the driving circuit, so the duty ratio determines the duty ratio range according to simulation and actual implementation.

The cylindrical ultrasonic motor is driven in an oscillation mode, so that the dependence of a traditional driving circuit on a step-up transformer can be eliminated, and the volume of the driving circuit is reduced.

The invention relates to a cylindrical stator ultrasonic motor transformerless LLC drive control method, which comprises the following steps:

(1) a direct current power supply is switched on to provide an energy source for the system;

(3) as the energy stored in the inductor is continuously increased, the terminal voltage peak value of the motor is also continuously improved, and the motor gradually enters an operating state;

(4) along with the operation of the motor, the self frequency of the motor is changed due to self heating and other factors, and the driving frequency is required to be changed accordingly. The voltage measuring circuit measures the voltage at two ends of the motor in real time, sends signals to the PID controller, and adjusts the voltage at the end of the motor by analyzing and adjusting the duty ratio and frequency of driving signals of the switching device.

Claims

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;

The LLC oscillating boosting voltage is composed of a charging inductor L ₁ , an oscillating inductor L ₂ , an oscillating capacitor C ₂ and a switching device; the charging inductor L ₁ is connected to the DC power supply and is connected to the switching device to form a loop; the oscillating inductor L ₂ and the oscillating capacitor C After ₂ is connected in series, it is connected in parallel to both ends of the switching device; the parallel body of the motor equivalent circuit C _m and R _m is connected in parallel with C ₂ .

2 . The transformerless LLC drive control circuit for a cylindrical stator ultrasonic motor according to claim 1 , wherein when the switching device is in a disconnected or open state, the LLC oscillating booster circuit is in a charging or oscillating state. 3 .

3. The transformerless LLC drive control circuit for a cylindrical stator ultrasonic motor according to claim 1, wherein the cylindrical stator ultrasonic motor comprises 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 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.

4. a cylindrical stator ultrasonic motor transformerless LLC drive control method, based on the described cylindrical stator ultrasonic motor transformerless LLC drive control circuit of claim 1-3, 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.

5 . The transformerless LLC drive control method for a cylindrical stator ultrasonic motor according to claim 4 , wherein, in the step 4, the drive signal is divided into two phases, A and B, and the time phase differs by 90°. 6 .