Low-power power supply method for the solenoid valve opening and maintaining stage based on pulse width modulation technology

Abstract

The present invention discloses a low-power supply method for the opening and maintaining stages of a solenoid valve based on pulse width modulation technology. The method includes: in the opening and maintaining stages of the solenoid valve drive circuit, establishing a target model for the opening and maintaining stages of the solenoid valve under the constraint of modulation frequency and duty cycle calculation, inputting the component parameters, and outputting the modulation frequency and duty cycle according to the optimization algorithm; inputting the modulation frequency and duty cycle as control signals into the controller, generating a voltage pulse width modulation square wave PWM drive pulse and inputting it into the driver, and outputting a drive voltage to supply power to the electromagnetic coil, so as to realize low-power supply for the solenoid valve drive circuit in the opening and maintaining stages. The present invention can give specific voltage square wave frequency and duty cycle according to the digital hydraulic valve closing current and drive circuit component parameters under the condition of meeting low power consumption, so that the digital hydraulic valve meets the functional requirements and reduces the temperature rise of the electromagnet module.

Description

Technical Field

[0001] The present invention relates to a low-power supply method, and particularly to a low-power supply method for the solenoid valve opening and maintaining stage based on pulse width modulation technology. Background Art

[0002] The high-speed switch type pilot stage digital hydraulic valve has strong anti-pollution ability and high reliability, and has obvious advantages in harsh working environments such as construction machinery. It is the core control component in the intelligent development of equipment such as construction machinery. Aiming at the problems of low frequency response and serious heating in the high-speed switch type pilot stage digital hydraulic valve, most of the existing high-speed switch type pilot stage voltage control technologies adopt two-stage, three-stage, five-stage or seven-stage voltage pulse width modulation methods. For example, Patent CN202010332933.6 adopts a five-stage voltage control method; while Patent CN202010014346.2 divides a single opening and closing cycle of the high-speed switch valve into seven stages, and represents them with corresponding digital codes, namely the preloading excitation stage, the preloading maintenance stage, the opening stage, the reverse excitation stage, the opening maintenance stage, the closing stage and the closing maintenance stage. No matter which voltage control method is adopted, there is an opening and maintaining stage. Compared with other stages, the opening and maintaining stage has the longest time and is one of the key stages determining the temperature rise of the solenoid valve electromagnet. The voltage pulse width modulation method in the opening and maintaining stage is to make the current flowing through the switch valve coil not lower than the closing current by outputting a voltage square wave with a fixed frequency f and a duty cycle τ. Usually, the modulation frequency is between 1 kHz and 200 kHz.

[0003] The existing pulse width modulation technology for the opening and maintaining stage of high-speed switch valves is not perfect for the calculation methods of modulation frequency and duty cycle. For example, in Patent CN202010014349.6, the duty cycle is determined by the product of the duty cycle and the power supply voltage being slightly greater than the product of the electromagnet coil resistance and the closing current. Since there is inductance in the electromagnet coil, the equivalent resistance for calculating the duty cycle is not equal to the electromagnet coil resistance, and the quantitative data of "slightly greater than" needs to be determined by experimental testing. There is also little report on the selection of modulation frequency. Therefore, the existing technology does not give a perfect calculation method for the selection of voltage square wave frequency and duty cycle. Summary of the Invention

[0004] In order to solve the problems in the background art, the present invention provides a low-power supply method for the solenoid valve opening and maintaining stage based on pulse width modulation technology. The method of the present invention can give the specific voltage square wave frequency f and duty cycle according to the closing current of the digital hydraulic valve and the parameters of the drive circuit components, so as to reduce the temperature rise of the electromagnet module while meeting the functional requirements of the digital hydraulic valve, which is very important for the industrial control field.

[0005] The technical solution adopted by the present invention is:

[0006] The low-power power supply method for the solenoid valve opening and maintaining stage of the present invention includes the following steps:

[0007] Step 1) In the opening and maintaining stage of the solenoid valve driving circuit, establish a target model for the solenoid valve opening and maintaining stage of the solenoid valve driving circuit under the modulation frequency and duty cycle calculation constraints. Input the component parameters of the solenoid valve driving circuit into the target model for the solenoid valve opening and maintaining stage. The target model for the solenoid valve opening and maintaining stage outputs the modulation frequency and duty cycle of the solenoid valve driving circuit according to the optimization algorithm.

[0008] Step 2) Input the modulation frequency and duty cycle as control signals into the controller of the solenoid valve driving circuit. The controller generates a voltage pulse width modulation square wave PWM driving pulse and inputs it into the driver of the solenoid valve driving circuit. The driver outputs a driving voltage to supply power to the electromagnetic coil of the solenoid valve driving circuit, realizing low-power power supply in the opening and maintaining stage of the solenoid valve driving circuit.

[0009] In the said step 1), in the opening and maintaining stage of the solenoid valve driving circuit, the target model for the solenoid valve opening and maintaining stage is specifically as follows:

[0010] minP w (f, τ)

[0011] Wherein, P w () represents the resistive loss of the electromagnetic coil of the solenoid valve driving circuit; f represents the modulation frequency of the solenoid valve driving circuit; τ represents the duty cycle of the solenoid valve driving circuit.

[0012] The resistive loss of the electromagnetic coil of the said solenoid valve driving circuit is specifically as follows:

[0013]

[0014] Wherein, I average () represents the average current of the solenoid valve driving circuit; R w represents the solenoid coil resistance.

[0015] The average current of the said solenoid valve driving circuit is specifically as follows:

[0016]

[0017] Wherein, U represents the supply voltage of the solenoid valve driving circuit; R s represents the current sampling resistance of the solenoid valve driving circuit; R u represents the unloading resistance of the solenoid valve driving circuit; L 1 represents the inductance in the open state of the solenoid valve driving circuit.

[0018] The component parameters of the said solenoid valve driving circuit include the supply voltage U of the solenoid valve driving circuit, the current sampling resistance Rs 、 unloading resistor R u 、 on-state inductance L 1 and coil resistance R w 。

[0019] In the said step 1), the modulation frequency and duty cycle calculation constraints are specifically as follows:

[0020] n s ×I c -I lend (f, τ) ≤ 0

[0021] f max -f ≥ 0

[0022] τ - 1 ≤ 0

[0023] -f ≤ 0

[0024] -τ ≤ 0

[0025] Wherein, n s represents the typical safety margin used in engineering calculations, n s ×I c represents the turn-off current; I c represents the turn-off current of the solenoid valve drive circuit; I lend () represents the minimum current of the solenoid valve drive circuit; f max represents the minimum value between the maximum pulse frequency output by the controller and the maximum pulse frequency received by the driver.

[0026] The component parameters of the said solenoid valve drive circuit include the turn-off current I of the solenoid valve drive circuit c 。

[0027] In the said step 1), the minimum current of the said solenoid valve drive circuit is specifically as follows:

[0028]

[0029] Wherein, U represents the supply voltage of the solenoid valve drive circuit; R w represents the solenoid valve coil resistance; R s represents the current sampling resistance of the solenoid valve drive circuit; R u represents the unloading resistor of the solenoid valve drive circuit; L 1 represents the on-state inductance of the solenoid valve drive circuit.

[0030] The said typical safety margin n s is preferably 1.05 to 1.5.

[0031] In the said step 1), the optimization algorithm is specifically the Lagrange multiplier optimization algorithm.

[0032] The beneficial effects of the present invention are as follows:

[0033] Compared with the existing estimation method and testing method, the present invention can give specific voltage square wave frequency and duty cycle according to the closing current of the digital hydraulic valve and the parameters of the driving circuit components under the condition of meeting low power consumption, so that the digital hydraulic valve meets the functional requirements and reduces the temperature rise of the electromagnet module. Description of the Drawings

[0034] Figure 1 It is a driving signal flow chart of the electro-hydraulic control module of the present invention;

[0035] Figure 2 It is a schematic diagram of the switch valve driver circuit of the present invention;

[0036] Figure 3 It is a voltage and current waveform diagram in the opening and maintaining stage of the present invention;

[0037] Figure 4 It is a schematic diagram of the voltage being at a low level in a single cycle of the present invention;

[0038] Figure 5 It is a schematic diagram of the current flow direction during unloading of the present invention;

[0039] Figure 6 It is a schematic diagram of the voltage being at a high level in a single cycle of the present invention;

[0040] Figure 7 It is a schematic diagram of the current flow direction during loading of the present invention;

[0041] Figure 8 It is a schematic diagram of the test circuit of the present invention;

[0042] Figure 9 It is a temperature rise curve diagram of the 4WE coil of the present invention. Detailed Embodiment

[0043] The following further describes the present invention in detail with reference to the drawings and specific embodiments.

[0044] The low-power supply method for the opening and maintaining stage of the solenoid valve of the present invention includes the following steps:

[0045] Step 1) In the opening and maintaining stage of the solenoid valve driving circuit, establish a target model for the opening and maintaining stage of the solenoid valve driving circuit under the constraint of modulation frequency and duty cycle calculation. Input the component parameters of the solenoid valve driving circuit into the target model for the opening and maintaining stage of the solenoid valve. The target model for the opening and maintaining stage of the solenoid valve outputs the modulation frequency and duty cycle of the solenoid valve driving circuit according to the optimization algorithm.

[0046] In step 1), in the opening and maintaining stage of the solenoid valve driving circuit, the target model for the opening and maintaining stage of the solenoid valve is specifically as follows:

[0047] minP w (f, τ)

[0048] where P w () represents the resistive loss of the electromagnetic coil of the solenoid valve drive circuit; f represents the modulation frequency of the solenoid valve drive circuit; τ represents the duty cycle of the solenoid valve drive circuit.

[0049] The resistive loss of the electromagnetic coil of the solenoid valve drive circuit is specifically as follows:

[0050]

[0051] where I average () represents the average current of the solenoid valve drive circuit; R w represents the solenoid valve coil resistance.

[0052] The average current of the solenoid valve drive circuit is specifically as follows:

[0053]

[0054] where U represents the supply voltage of the solenoid valve drive circuit; R s represents the current sampling resistance of the solenoid valve drive circuit; R u represents the unloading resistance of the solenoid valve drive circuit; L 1 represents the on-state inductance of the solenoid valve drive circuit.

[0055] The component parameters of the solenoid valve drive circuit include the supply voltage U of the solenoid valve drive circuit, the current sampling resistance R s , the unloading resistance R u , the on-state inductance L 1 and the coil resistance R w .

[0056] In step 1), the modulation frequency and duty cycle calculation constraints are specifically as follows:

[0057] n s ×I c -I lend (f, τ) ≤ 0

[0058] f max -f ≥ 0

[0059] τ - 1 ≤ 0

[0060] -f ≤ 0

[0061] -τ ≤ 0

[0062] where n s represents the typical safety margin used in engineering calculations, n s×I c Indicates the turn-off current; I c Indicates the turn-off current of the solenoid valve drive circuit; I lend () indicates the minimum current of the solenoid valve drive circuit; f max Indicates the minimum value between the maximum pulse frequency output by the controller and the maximum pulse frequency received by the driver;

[0063] The component parameters of the solenoid valve drive circuit include the turn-off current I of the solenoid valve drive circuit c .

[0064] In step 1), the minimum current of the solenoid valve drive circuit is specifically as follows:

[0065]

[0066] Where U represents the supply voltage of the solenoid valve drive circuit; R w represents the solenoid coil resistance; R s represents the current sampling resistance of the solenoid valve drive circuit; R u represents the unloading resistance of the solenoid valve drive circuit; L 1 represents the inductance in the open state of the solenoid valve drive circuit.

[0067] Typical safety margin n s Preferably 1.05 to 1.5.

[0068] In step 1), the optimization algorithm is specifically the Lagrange multiplier optimization algorithm.

[0069] In step 2), the modulation frequency and duty cycle are used as control signals and input into the controller of the solenoid valve drive circuit. The controller generates a voltage pulse width modulation square wave PWM drive pulse and inputs it into the driver of the solenoid valve drive circuit. The driver outputs a drive voltage to supply power to the electromagnetic coil of the solenoid valve drive circuit, realizing low-power supply in the open maintenance stage of the solenoid valve drive circuit.

[0070] Specific embodiments of the present invention are as follows:

[0071] As Figure 1 shown, when the controller of the present invention receives the rising edge of the control signal, the controller outputs a drive pulse with a duty cycle of 100% in the opening stage; when the coil current reaches the opening trigger current, the controller enters the opening maintenance stage. The controller calculates the drive pulse frequency and duty cycle based on the known parameters and sends the drive pulse to the driver. The driver amplifies the drive pulse square wave signal by turning the switching device on and off. The frequency and duty cycle of the amplified square wave signal remain unchanged, and the amplitude becomes equal to the voltage source. Under the action of the drive voltage, a magnetic field is generated around the coil, and the high-speed switching valve body always remains in the open state under the action of the magnetic field force.

[0072] The high-speed switching valve drive circuit used in the present invention is as follows Figure 2 shown. ① DC power supply, ②③④⑤ Mosfet transistors (switching devices), ⑥ current sampling resistor, ⑦ inductance of the electromagnetic coil in the open state of the high-speed switching valve, ⑧ resistance of the electromagnet coil, ⑨ diode, and ⑩ unloading resistor. T s represents a current waveform period of the high-speed switching valve drive circuit.

[0073] As Figure 3 shown, it is the voltage and current waveform diagram of the opening and maintaining stage of the high-speed switching valve drive circuit of the present invention. The model of the current waveform can be established by the recurrence method, series, and Taylor expansion. When the voltage waveform is at a low level, the drive frequencies of the field effect transistors ②③④⑤ are at a low level and in the cut-off state, as Figure 4 shown. Therefore, the electromagnet coil forms a current closed-loop circuit through the unloading circuit, and the current flow direction is as Figure 5 shown. When the voltage waveform is at a high level, as Figure 6 shown, the drive frequencies of the field effect transistors ③④ are at a high level and in the conducting state, the drive frequencies of the field effect transistors ②⑤ are at a low level and in the cut-off state, and the switching valve electromagnetic coil forms a closed-loop circuit through the main circuit, and the current flow direction is as Figure 7 shown. When at the Nth voltage waveform, the current value at the last moment of the high level is specifically as follows:

[0074]

[0075]

[0076]

[0077] Among them, I r represents the starting current of the solenoid valve drive circuit, and the component parameters of the solenoid valve drive circuit also include the starting current I r of the solenoid valve drive circuit.

[0078] Taking the 4WE type electromagnetic coil as an example in the present invention, the relevant parameters are first determined: the coil resistance R w is 18.5 Ω, the coil inductance L 1 is 370 mH, the current sampling resistor R s is 0.5 Ω, the unloading resistor R u is 50 Ω, the supply voltage U is 24V, and its closing current I c is 0.26A. The controller uses STM32F103ZET6, the drive module uses 4 Mosfet power transistors of 25N06, and the maximum output frequency of the drive circuit is 50KHz. A Mean Well switching power supply is used, with an output voltage of 24V and a maximum power of 50W.

[0079] Substituting the relevant parameters into the various formulas gives the following results:

[0080]

[0081] The establishment of the constraint conditions is specifically as follows:

[0082] g 1 (f, τ) = n s × I c - I lend ≤ 0

[0083] g 2 (f, τ) = τ - 1 ≤ 0

[0084] g 3 (f, τ) = 0 - τ ≤ 0

[0085] g 4 (f, τ) = f - f max ≤ 0

[0086] g 5 (f, τ) = 0 - f ≤ 0

[0087] The establishment of the target model is specifically as follows:

[0088]

[0089] Construct the objective function and constraint conditions, and finally solve to obtain the duty cycle τ of 0.5 and the modulation frequency of 49525 Hz. While the duty cycle calculated by the equivalent resistance method is 0.41, and its corresponding minimum current is 0.21 A, this current will cause the solenoid valve to close and affect its normal operation.

[0090] Since the PWM pulse frequency in the controller is generated by timer counting, in this example, the chip crystal oscillator frequency is 72 MHz and the timer count is 1454. Therefore, a modulation frequency close to the optimal value of 49518 Hz can be generated. Finally, the controller generates the corresponding drive pulse according to the duty cycle of 0.5 and the modulation frequency of 49518.

[0091] As Figure 8 shown, the test circuit devices mainly include: a switching power supply, a control board, a drive board, an electromagnet, a digital thermometer, and a battery. Test conditions: duty cycle 0.5, drive frequency 2 KHz - 50 KHz, working duration 3 minutes. Due to power consumption, the electromagnet heats up, and the power consumption level can be judged by the temperature rise of the electromagnet. Under the same external environmental conditions, fixing the position where the thermocouple is attached, the test shows that the temperature rise of the electromagnet coil decreases gradually as the frequency increases. When the drive frequency reaches around 49500 Hz, the coil temperature rise reaches the minimum value. The specific test results are as follows Figure 9 shown.

[0092] In the present invention, unknown parameters of the model are calculated through known parameters and the target model in the solenoid valve opening and maintaining stage, so as to obtain the final modulation frequency f and duty cycle. Finally, the modulation frequency and duty cycle are incorporated into the controller, thereby completing the control of the high-speed switching valve in the opening and maintaining stage. Compared with the existing estimation method and testing method, the present invention can give specific voltage square wave frequency and duty cycle according to the digital hydraulic valve closing current and the parameters of the driving circuit components under the condition of meeting the minimum power consumption, enabling the digital hydraulic valve to meet the functional requirements and reducing the temperature rise of the electromagnet module.

Claims

1. A low-power supply method for the opening and maintaining stage of a solenoid valve based on pulse width modulation technology, characterized in that: The method includes the following steps: Step 1) In the opening and maintaining stage of the solenoid valve drive circuit, establish a target model for the opening and maintaining stage of the solenoid valve drive circuit under the constraint of modulation frequency and duty cycle calculation. Input the component parameters of the solenoid valve drive circuit into the target model for the opening and maintaining stage of the solenoid valve. The target model for the opening and maintaining stage of the solenoid valve outputs the modulation frequency and duty cycle of the solenoid valve drive circuit according to the optimization algorithm; Step 2) Input the modulation frequency and duty cycle as control signals into the controller of the solenoid valve drive circuit. The controller generates a voltage pulse width modulation square wave PWM drive pulse and inputs it into the driver of the solenoid valve drive circuit. The driver outputs a drive voltage to supply power to the electromagnetic coil of the solenoid valve drive circuit, realizing low-power supply in the opening and maintaining stage of the solenoid valve drive circuit; In the said Step 1), in the opening and maintaining stage of the solenoid valve drive circuit, the target model for the opening and maintaining stage of the solenoid valve is specifically as follows: minP w (f,τ) Among them, P w () represents the resistive loss of the electromagnetic coil of the solenoid valve drive circuit; f represents the modulation frequency of the solenoid valve drive circuit; τ represents the duty cycle of the solenoid valve drive circuit; The specific resistance loss of the electromagnetic coil of the solenoid valve drive circuit is as follows: Among them, I average () represents the average current of the solenoid valve drive circuit; R w represents the solenoid valve coil resistance; The average current of the solenoid valve drive circuit is specifically as follows: Among them, U represents the supply voltage of the solenoid valve drive circuit; R s represents the current sampling resistor of the solenoid valve drive circuit; R u represents the unloading resistor of the solenoid valve drive circuit; L 1 represents the on-state inductance of the solenoid valve drive circuit; The component parameters of the solenoid valve drive circuit include the supply voltage U and current sampling resistor R of the solenoid valve drive circuit s , unloading resistor R u , inductance L in the open state 1 and coil resistance R w ; In the said Step 1), the modulation frequency and duty cycle calculation constraints are specifically as follows: n s ×I c -I lend (f,τ) ≤ 0 f max -f ≥ 0 τ - 1 ≤ 0 -f≤0 τ ≤ 0 Wherein, n s represents a typical safety margin; I c represents the turn-off current of the solenoid valve drive circuit; I lend () represents the minimum current of the solenoid valve drive circuit; f max represents the minimum value between the maximum pulse frequency output by the controller and the maximum pulse frequency received by the driver; The component parameters of the solenoid valve drive circuit include the turn-off current I of the solenoid valve drive circuit c .

2. The low-power supply method for the opening and maintaining stage of a solenoid valve based on pulse width modulation technology according to claim 1, characterized in that: In the said Step 1), the lowest current of the solenoid valve drive circuit is specifically as follows: Among them, U represents the supply voltage of the solenoid valve drive circuit; R w represents the solenoid valve coil resistance; R s represents the current sampling resistance of the solenoid valve drive circuit; R u represents the unloading resistance of the solenoid valve drive circuit; L 1 represents the on-state inductance of the solenoid valve drive circuit.

3. The low-power supply method for the opening and maintaining stage of a solenoid valve based on pulse width modulation technology according to claim 1, characterized in that: The typical safety margin n s is 1.05 to 1.

5.

4. The low-power supply method for the opening and maintaining stage of a solenoid valve based on pulse width modulation technology according to claim 1, characterized in that: In the said Step 1), the optimization algorithm is specifically the Lagrange multiplier optimization algorithm.

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