CN202424570U - Inductance-capacitance (LC) resonant driving circuit for ultrasonic motor - Google Patents

Abstract

The utility model relates to an LC resonant drive circuit for an ultrasonic motor. According to the capacitive load characteristics of the ultrasonic motor, the utility model forms a transformerless drive circuit for LC resonant step-up with the participation of the ultrasonic motor body through series matching inductance . Further, the utility model proposes a method of fixing all circuit parameters and only changing the driving signal frequency, duty cycle and resonance cycle number, so as to realize the driving control of the ultrasonic motor. Using USR30 type ultrasonic motor, the experimental verification was carried out.

Description

A kind of LC resonant drive circuit for ultrasonic motor

technical field

The utility model relates to an ultrasonic motor, in particular to the technical field of drive control of the ultrasonic motor.

Background technique

Ultrasonic motor is a new concept driving device that has appeared in the past two decades. Compared with traditional electromagnetic motors, it has high power density, no electromagnetic interference, low speed and high torque, fast action response, no noise in operation, and no input. These advantages make ultrasonic motors have broad application prospects in high-end motion control fields such as aerospace, robotics, precision processing equipment, medical equipment, and bioengineering, as well as general motion control fields such as household appliances and automotive electronics.

At present, the size of the ultrasonic motor drive controller is relatively large, which is greatly limited in some applications. According to the capacitive load characteristics of the motor, literature [1] proposed a transformerless drive circuit using LC resonance by simplifying the equivalent circuit of the ultrasonic motor, and carried out a simulation analysis. Literature [2] studied the design method of the resonant drive circuit, and explained the relationship between the amplitude and energy ratio of each harmonic in the output signal and the duty cycle of the drive signal and the resonant period. The research of the above literature provides a good foundation for the research of ultrasonic motor power resonant drive circuit, but the given drive circuit can only make the motor work at the pre-designed definite operating point, and the controllable variables such as the motor drive voltage and frequency cannot be controlled. regulation, which severely limits the practical application of this type of circuit. Literature [3] carried out a preliminary exploration on adjustable and controllable aspects, and analyzed the selection of different resistance and inductance values to realize off-line adjustment of frequency. However, since the inductance in the circuit is a power inductance, it is difficult to accurately realize the variable inductance value online, and the adjustable and controllable power resonant drive circuit still needs further research. The relevant references are as follows:

[1] Gu Juping, Hu Minqiang, Shi Bin, etc. Research on Resonant Boost Drive Technology of Ultrasonic Motors, Proceedings of the Chinese Society for Electrical Engineering, 2002, 22(8): 49-52.

[2] Li Huafeng, Zhao Chunsheng. Research on Ultrasonic Motor Driver Based on LC Resonance, Chinese Journal of Electrical Engineering, 2005, 25(23): 144-148.

[3] Gan Yunhua, Jinlong, Wang Xinjian, etc. Frequency conversion control characteristics of self-excited oscillation drive circuit of ultrasonic motor, Proceedings of the Chinese Society for Electrical Engineering, 2008, 28(9): 93-96.

Utility model content

The purpose of the utility model is to provide an LC resonant drive circuit for an ultrasonic motor to solve the problem of poor effect of the existing drive control method.

In order to achieve the above object, the circuit scheme of the present utility model is: a kind of LC resonant drive circuit for ultrasonic motor, the AC side of the A, B two-phase bridge drive circuit driving the ultrasonic motor is equipped with series matching inductors in series, so The A and B two-phase bridge drive circuits are respectively provided with a Boost boost circuit for adjusting the DC bus voltage of the corresponding phase bridge drive circuit. The power switch tube of the Boost boost circuit is connected in series with a diode, and the anode of the diode is connected to The series connection point of the series matching inductance L and the equivalent capacitance C of the ultrasonic motor.

The switch tubes of the A and B two-phase bridge drive circuits are MOSFETs.

According to the capacitive load characteristics of the ultrasonic motor, the utility model forms a transformer-less drive circuit with LC resonance step-up participated by the body of the ultrasonic motor by matching inductance in series. Furthermore, the utility model proposes a method of fixing all circuit parameters and only changing the driving signal frequency, duty cycle and resonance cycle number, so as to realize the driving control of the ultrasonic motor. The USR30 type ultrasonic motor is used for experimental verification.

Description of drawings

Figure 1 is an LC resonant drive circuit;

Figure 2 is the relationship between the resonant frequency of the motor and the drive frequency of the switch;

Figure 3 is a simulation waveform of different cycles and different duty ratios;

Fig. 4 is a structural block diagram of ultrasonic motor drive control;

Figure 5 is the driving waveform and resonance waveform of the 40% duty cycle of the B phase;

Figure 6 is a two-phase measured waveform.

Detailed ways

Below in conjunction with accompanying drawing, the utility model is described in further detail.

The AC sides of the A and B two-phase bridge drive circuits that drive the ultrasonic motor are all provided with series matching inductors L, and the A and B two-phase bridge drive circuits are respectively provided with DC bus voltages for adjusting the corresponding phase bridge drive circuits. The Boost voltage boosting circuit is characterized in that the power switch tube Q of the Boost voltage boosting circuit is connected in series with a diode D1, and the anode of the diode D1 is connected to the series connection point of the series matching inductor L and the capacitor C.

The ultrasonic motor (USM) can be considered capacitive near the resonant frequency, which is equivalent to a capacitor C. The Boost boost LC resonant driving circuit of the present invention is shown in Fig. 1 . Since there is an anti-parallel body diode inside the MOSFET device Q, it will discharge through this diode when the voltage of the capacitor C (that is, the ultrasonic motor) is reversed, so that the output voltage has only a positive half-wave. To prevent this, an ultrafast recovery diode is placed in series with the circuit so that the LC can fully oscillate during the switch-off period. The switch refers to the power switch tube Q.

The working principle of the circuit is: when the switch Q is turned on, the power supply stores energy to the inductor L; when the switch is turned off, the energy stored in the inductor is released to the capacitor C and resonates with it. The whole circuit is an LC series resonant circuit with initial conditions. There are two key reasons for the Boost unit to increase the voltage: one is that the inductor L can pump up the voltage after storing energy, and the other is that the capacitor C can maintain the output voltage, so the selection of the duty cycle has a great influence on the output voltage amplitude. Value and rms play a key role. The selection of the series matched inductor is determined by:

$\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; =</span>\frac{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; k\&pi;</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula, k is the number of full cycles resonant during the turn-off period, D is the duty cycle, and T is the switching period.

Once the matching inductance is selected, the LC resonant frequency is fixed, and the duty cycle of the resonant waveform is changed by adjusting the frequency of the drive signal driving the MOSFET, and the equivalent effect of the discontinuous sine wave is changed, thereby adjusting the motor speed to achieve the purpose of control . The relationship between the frequency f of the switch drive signal and the resonant frequency f _USR of the motor is as follows (see Figure 2):

$\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; USR</span>}}\frac{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

According to the formulas (1) and (2), it can be seen that the speed control of the ultrasonic motor can be realized by adjusting the duty ratio D of the switch signal, the frequency f of the switch signal and the number of conduction cycles k. The above formula is equivalently transformed into:

$\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; D.</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;k</span>}}\sqrt{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; LC</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

To keep the above formula established, it is only necessary to change the values of the two parameters in f, D, and k. There are three possible speed regulation methods. The first one: keep D unchanged, and adjust f and k. This method has a large frequency range and amplitude, ranging from a few kHz to tens of kHz, and the speed regulation range is small, because the more the frequency is, the more serious the distortion will be. The second one: keep k constant, adjust f and D. This method can realize continuous speed regulation with high precision. The third way: keep f unchanged, adjust k and D. The duty ratio calculated by this method may be a negative value, which does not conform to the actual situation. It can be seen that the second method is the ideal speed regulation method. Taking the second method as an example, use Miltisim10 to conduct simulation tests, analyze the obtained waveforms and data, and draw the following conclusions: try to choose a signal with a small duty cycle and a small number of cycles to ensure sufficient boosting capability and reduce nonlinear Influence. The waveform is shown in Figure 3.

Experimental verification is carried out below. The structure of the experimental circuit is shown in Figure 4. The general-purpose PWM generator chip TL494 is used to generate two channels of signals PWM1 and PWM2 with adjustable frequency and pulse width, and a two-phase frequency-dividing circuit composed of a double rising edge D flip-flop CD4013 is used to generate two-phase four-channel PWM signals with a mutual difference of 90° , amplified by the dedicated MOSFET driver chip IR4427 to drive the MOSFET to work, thereby completing the Boost boost LC resonance participated by the ultrasonic motor body, so as to achieve the purpose of driving and controlling the operation of the ultrasonic motor.

Because the equivalent capacitance of the motor is converted under static conditions, and the dynamic capacitance cannot be directly measured when the motor is running, so the matching inductance parameters are corrected according to the measured data to obtain the matching inductance that meets the resonant frequency. Table 1 shows the measured equivalent capacitor terminal voltage peak-to-peak value Vpp (V), voltage effective value Vrms (V), driving frequency (kHz) and converted resonant frequency (kHz). Figure 5 is the measured driving waveform and resonance waveform of the two cycles of the B phase with a 40% duty cycle. Since other parameters are ignored when converting the equivalent capacitance, the influence of other parameters such as resistance is not considered in the simulation test, so the waveform obtained in the experiment does not oscillate with equal amplitude, but has attenuation. Figure 6 is the measured resonant waveform of the two-phase terminal voltage of the motor. It can be seen from the measured parameters and waveforms that in order to make the motor run effectively, the resonant frequency with a slightly larger duty cycle of the two cycles can be selected to ensure sufficient resonant frequency and effective voltage value.

Table 1 Experimental measurement data of two-phase equivalent capacitance terminals

The utility model provides that all circuit parameters such as the fixed inductance value remain unchanged, and only the frequency, duty cycle and cycle number of the power switch drive signal are changed to change the sine wave, thereby realizing the adjustable and controllable motor drive voltage, and further realizing the method of speed control. The feasibility of this method is verified by the hardware circuit composed of TL494, and a useful attempt is made in the miniaturization and miniaturization of the ultrasonic motor drive control.

The utility model proposes a new driving control method: on the basis of fixing all circuit parameters such as the fixed inductance value, only changing the power switch driving signal frequency, duty cycle and resonant cycle number, so that the sinusoidal frequency of driving the ultrasonic motor The wave equivalent effect is changed, so that the motor drive voltage can be adjusted and controlled, and then the motor speed control can be realized. On this basis, the simulation test is carried out and the hardware circuit is built. The feasibility of this method is verified by experiments, and a reliable basis is provided for better drive control of the ultrasonic motor.

Claims (2)

1. A kind of LC resonant driving circuit for ultrasonic motor, the AC side of the A, B two-phase bridge driving circuit of driving ultrasonic motor is all connected in series and is provided with series matching inductance, and described A, B two-phase bridge driving circuit respectively A Boost boost circuit for adjusting the DC bus voltage of the corresponding phase bridge drive circuit is provided, and it is characterized in that the power switch tube of the Boost boost circuit is connected in series with a diode, and the anode of the diode is connected to the series matching inductance L and On the series point of the equivalent capacitance C of the ultrasonic motor. 2 . The LC resonant drive circuit for ultrasonic motors according to claim 1 , wherein the switch tubes of the A and B two-phase bridge drive circuits are MOSFETs. 3 .

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