Electromagnetic valve rapid movement driving method based on voltage pulse width modulation technology
Technical Field
The invention relates to the field of electromagnetic valve control, in particular to a method for driving an electromagnetic valve to move quickly based on a voltage pulse width modulation technology.
Background
In the solenoid valve, the ampere-turns and the working air gap have the greatest influence on the electromagnetic force of the electromagnet. Ampere-turns is the product of the number of turns of the coil and the current in the single coil. In the case where the magnetic flux is not saturated, the larger the current, the larger the electromagnetic force; the smaller the working air gap, the greater the electromagnetic force. Since the solenoid valve is usually opened when the working air gap in the electromagnet is largest, and closed when the working air gap in the electromagnet is smallest, the opening current is larger than the closing current.
In the prior art, a multi-voltage source mode is adopted in the field of high-frequency electromagnetic valves to achieve a high-frequency control function, and a high-voltage source is adopted as excitation voltage in a patent [ CN201610015304.4] to enable the electromagnetic valves to be opened in a short time; the voltage-stabilized power supply provides a maintaining voltage to keep the current at a value slightly larger than the closing current; the negative voltage source provides a large reverse voltage to reduce the current to the off current for a short time. The three-stage voltage method can accelerate the working frequency of the electromagnetic valve.
However, this control method has some disadvantages. First, multiple voltage sources complicate the operation of the system and can generate large errors. Secondly, the switching time of each voltage segment in the control method is determined according to the magnitude relation between the actual current value and the theoretical current value in the system circuit, which causes a problem: in a high-speed electromagnetic valve, because the dynamic characteristic of the electromagnetic valve is weaker and the current dynamic characteristic of an electromagnet is better, the method can cause the switching of a voltage source when a valve core of the electromagnetic valve is in a motion state, so that the dynamic characteristic of the electromagnetic valve during opening and closing is reduced. Specifically, in the opening stage of the electromagnetic valve, the current rapidly rises to the opening current, while the electromagnet is still moving, i.e. not completely opened, and at the moment, the voltage source is switched, so that the dynamic characteristic in the opening stage is reduced. In the closing phase of the solenoid valve, the current is already reduced below the closing current, and the solenoid valve core is still in the closing motion state of slow recovery, at this time, if the reverse voltage source is switched to the zero voltage source, the dynamic characteristic of the closing phase is reduced.
Disclosure of Invention
In order to solve the difficulties, the invention provides a method for driving the rapid movement of the electromagnetic valve based on a voltage pulse width modulation technology.
The invention discloses a rapid movement driving method of an electromagnetic valve based on a voltage pulse width modulation technology, wherein a coil of the electromagnetic valve is connected with a voltage source through a current detector, the voltage source is connected with a duty ratio controller, the duty ratio controller is connected with a controller, and a pressure sensing system is connected with each working port of the electromagnetic valve to acquire the pressure state of each working port of the electromagnetic valve in real time; the controller is connected with the pressure sensing system to acquire data in the pressure sensing system in real time, and comprises a control signal generating unit which generates a control signal;
the control method comprises the following steps:
a preloading excitation stage: before the rising edge of the control signal arrives, according to the duration time of the preloading stage, the controller triggers the duty ratio controller in advance, the duty ratio controller outputs a high-frequency square wave signal with the duty ratio of 100% to the voltage source, the voltage source outputs a voltage square wave with the duty ratio of 100%, the current of the coil just reaches the preloading current after the preloading excitation stage, and the preloading current value is slightly smaller than the starting current;
a preload maintenance phase: the controller triggers the duty ratio controller, the duty ratio controller outputs a high-frequency square wave signal with the duty ratio alpha to the voltage source, the voltage source starts to output a voltage square wave with the duty ratio alpha, wherein alpha is more than 0 and less than 1, and under the action of the maintaining voltage, the coil current always makes high-frequency small fluctuation around the pre-loading current value, namely the pre-loading current state is reached;
and (3) starting: when the rising edge of the control signal comes, the controller triggers the duty ratio controller, the duty ratio controller outputs a high-frequency square wave signal with the duty ratio of 100% to the voltage source, the voltage source outputs a voltage square wave with the duty ratio of 100%, the current of the coil rapidly rises under the excitation of the voltage square wave with the duty ratio of 100%, the current is slightly fluctuated on the value of the preloading current before the rising edge of the control signal comes, under the excitation of the voltage square wave with the duty ratio of 100%, the current rises to the opening current in a short time, at the moment, the valve core of the electromagnetic valve is opened and moved, and enters the opening stage, and the excitation of the voltage source is continuously maintained until the electromagnetic valve is ensured to completely start;
a starting maintaining stage: then the controller triggers the duty ratio controller, the duty ratio controller outputs a high-frequency square wave signal with the duty ratio beta to a voltage source, the voltage source starts to output a voltage square wave with the duty ratio beta, wherein the value of beta is more than 0 and less than 1, the current gradually decreases and finally does high-frequency small fluctuation around the value of the maintaining current, and the maintaining current is slightly larger than the closing current so as to keep the opening state of the electromagnetic valve;
and (3) closing stage: when the falling edge of the control signal comes, the controller triggers the duty ratio controller, the duty ratio controller outputs a high-frequency square wave signal with a duty ratio of-100% to the voltage source, the voltage source outputs a voltage square wave with a duty ratio of-100%, under the excitation of the voltage square wave with a duty ratio of-100%, the current of the coil is rapidly reduced to a closing current, at the moment, the valve core starts to move, the reset is carried out, and the voltage source continues to excite until the current is reduced to 0;
closing the maintaining stage: the controller triggers the duty ratio controller, the duty ratio controller outputs a high-frequency square wave signal with the duty ratio of 0 to the voltage source, and the voltage source starts to output a voltage square wave with the duty ratio of 0, namely power is not supplied; until the next preloading phase arrives.
As a preferred embodiment of the present invention, in the preload maintaining stage, the modulated equivalent voltage value of the high-frequency voltage square wave signal with the duty ratio α output by the voltage source is smaller than the product of the resistance of the solenoid valve coil and the opening current.
As a preferred embodiment of the present invention, the modulated equivalent voltage value of the high-frequency voltage square-wave signal with the duty ratio β is greater than the product of the solenoid coil resistance and the closing current.
As a preferred aspect of the present invention, the duration of the opening phase is equal to the time required by the solenoid valve to complete the stroke by using a voltage source modulated by a high-frequency voltage square wave signal with a duty ratio of 100% in a 0 current state of the solenoid valve, so as to ensure that the solenoid valve is completely started.
As a preferred embodiment of the present invention, the calculation process of the duration time required by the pre-loading excitation phase is as follows: and the controller calculates the time required by the current of the coil to rise to the preloading current according to the current driving voltage, the current of the solenoid valve, the linear inductance resistance and the inductance, and the time is used as the duration time of the preloading excitation stage.
As a preferable scheme of the invention, the duration time required by the preloading maintaining stage is 1-2 ms.
As a preferred embodiment of the present invention, the controller may calculate a system on current and a system off current in a current state according to the data; the control signal generated by the controller is a square wave signal, the duty ratio of the control signal is the target opening time and the cycle time ratio of the electromagnetic valve, the rising edge of the control signal indicates that an operator wants the electromagnetic valve to be opened, the high potential of the control signal indicates that the operator wants the electromagnetic valve to be opened, the falling edge of the control signal indicates that the operator wants the electromagnetic valve to be closed, and the low potential of the control signal indicates that the operator wants the electromagnetic valve to be closed; the controller acquires the duty ratio, the frequency, the rising edge moment and the falling edge moment of the control signal generated by the control signal generating unit in real time.
As a preferred scheme of the present invention, the duty ratio controller is connected to a voltage source and can output a high-frequency square wave signal to the voltage source, the voltage source amplifies the high-frequency square wave signal according to the received high-frequency square wave signal, the frequency and the duty ratio of the amplified high-frequency square wave signal are not changed, and the amplitude is equal to that of the voltage source.
The invention has the beneficial effects that:
(1) the pressure sensor can detect the oil pressure of the oil inlet and the working port of the electromagnetic valve in real time and feed the oil pressure back to the arithmetic unit, and the arithmetic unit automatically calculates the opening current and the closing current according to the data of the early-stage test of the electromagnetic valve.
(2) The pre-loading stage (including a pre-loading excitation stage and a pre-loading maintaining stage) adopts two stages of voltage excitation modulated by different duty ratios, namely the voltage excitation modulated by a high-frequency square wave signal with the duty ratio of 100% is firstly used, so that the current of the coil quickly reaches the pre-loading current. And then the voltage modulated by the high-frequency square wave signal with the duty ratio of alpha is used for maintaining, so that the current is maintained in a pre-loading current state. Conventional multiple voltage source control techniques are used to implement the function of pre-load current, and usually employ a single voltage for pre-load excitation, since the pre-load current is a relatively fixed value, and in combination with the current resistance situation, the corresponding pre-load voltage is also relatively fixed, and the magnitude of the pre-load voltage is equal to the product of the pre-load current and the resistance. In the traditional method, the pre-loading voltage is smaller than the pre-loading excitation voltage in the invention, so that the current is slowly increased under the action of the pre-loading voltage, the time required for the current to be increased to the pre-loading current is longer, and the whole pre-loading process is prolonged. Therefore, for some high-frequency switches, the method of preloading by using a single voltage source often cannot meet the requirement of higher-frequency on-off. Furthermore, as the duty cycle varies, when the duty cycle is high, the time left to open the preload stage is reduced, and when the time is reduced such that the current cannot be increased to the preload current, the effect of the preload stage is further reduced. Therefore, there are many limitations to the method of performing the preloading using a single voltage. Compared with a control mode that only one section of voltage source is used in the preloading stage, the control method provided by the invention has the advantages that the voltage source which is modulated by the high-frequency square wave signal with the duty ratio of 100% is adopted for excitation, the current rising rate is higher, the current can be quickly raised to the preloading current state, and the time consumption of the preloading stage is shorter. The method is suitable for occasions with higher switching frequency.
(3) In the invention, the excitation duration time of a voltage source modulated by a high-frequency square wave signal with a duty ratio of 100% in the opening stage is equal to the time required for exciting the solenoid valve to finish the stroke by adopting the voltage source modulated by the high-frequency square wave signal with the duty ratio of 100% in the 0 current state of the solenoid valve; the method has the advantages that: since the solenoid valve can be fully opened if it is energized by the voltage source instead in the 0-current state, the same energizing time will certainly allow the valve to be fully opened if a certain pre-load current is already available. Therefore, the method can ensure that the valve core of the electromagnetic valve completes the expected working stroke, and ensure that the valve core is in a static state at the moment of switching to the opening maintaining stage in the opening stage, thereby further improving the dynamic characteristic of the opening stage of the electromagnetic valve.
In the prior art, patent No. CN201610015304.4 discloses switching the high voltage excitation to the low voltage maintenance immediately after the current is increased to the opening current, which results in the solenoid valve still being in the opening motion state and not completing the stroke when the coil current reaches the opening current because the dynamic characteristic of the solenoid valve is weak and the current dynamic characteristic of the solenoid coil is good. Immediately switching the high voltage excitation to the low voltage hold at this time reduces the driving force at the opening stage of the solenoid valve, which reduces the dynamic characteristics at the opening stage of the solenoid valve.
(4) The invention makes the negative voltage continue to be excited under the condition that the duty ratio controller outputs a signal with a duty ratio of-100% to the voltage source until the current is reduced to 0. The advantage of this method is that in the prior art, as in patent CN201610015304.4, when the current of the exciting coil with the negative voltage source drops to the closing current, the negative voltage source stops working immediately. Since the dynamic characteristics of the solenoid valve are slow in a high frequency state and the dynamic characteristics of the current of the electromagnet are good, in the prior art, the current is already reduced below the closing current, and the electromagnet valve core is still in a closing state of slow recovery, so that the excitation of the negative voltage source is stopped, the driving force of the closing stage of the solenoid valve is reduced, and the dynamic characteristics of the valve in the closing stage are reduced. In the invention, the reverse voltage output by the voltage source modulated by the high-frequency square wave signal with the duty ratio of-100% can work until the current of the electromagnetic valve is reduced to 0, so that the dynamic characteristic of the closing stage of the electromagnet can be improved, and the time consumption of the closing stage of the electromagnetic valve is shortened.
(5) The single voltage source reduces the cost of the device compared with multiple voltage sources.
(6) The control mode of single voltage source duty ratio regulation does not have the phenomenon of multi-power switching, so the phenomenon of short circuit caused by the power will not occur, and the work will be more stable. And compared with multiple voltage sources, the working condition is simpler, and a plurality of working errors are greatly reduced.
Drawings
FIG. 1 is a schematic structural diagram of a solenoid valve driving system corresponding to the method of the present invention.
FIG. 2 is a graph of control signals and current for the method of the present invention.
FIG. 3 is the opening and closing characteristics of a single voltage driven solenoid valve;
FIG. 4 is a graph of the on and off characteristics of a solenoid valve driven by the method of the present invention;
fig. 5 shows the opening and closing characteristics of the solenoid valve in the scheme of preloading with a voltage square wave with a certain fixed duty ratio (the duty ratio is less than 1).
Detailed Description
The invention is further described with reference to the drawings and the specific embodiments in the following description.
As shown in fig. 1, the method of the present invention is based on the solenoid valve fast motion driving system based on the voltage pulse width modulation technique shown in fig. 1, and the driving system includes a duty ratio controller 1, a voltage source 2, a current detector 3, a solenoid valve 4, a pressure sensing system 5, and a controller 6; the pressure sensing system 5 is connected with each working port of the electromagnetic valve 4 to obtain the pressure state of each working port of the electromagnetic valve in real time; the controller 6 is connected with the pressure sensing system 5 to acquire data in the pressure sensing system 5 in real time, the controller 6 can calculate system opening current and closing current in the current state according to the acquired data, the controller comprises a control signal generating unit, and the control signal generating unit generates a control signal; the controller is connected with a duty ratio controller 1, the duty ratio controller 1 is connected with a voltage source 2, and the duty ratio controller can output square wave signals to the voltage source; the voltage source 2 is connected to the coil of the solenoid valve 4 via a current detector 3. The control signal 7 is input by an operator and represents the on-off state of the electromagnetic valve expected by the operator, namely, the high potential of the control signal represents that the operator expects the on-off valve to be in the on state, and the low potential of the control signal represents that the operator expects the on-off valve to be in the off state.
Before the system is used, electrical parameters such as resistance and inductance of a solenoid valve coil are obtained by a static test method. Obtaining current required by opening of the electromagnetic valve under the current working condition (the current working condition refers to the current oil inlet pressure PP and the control port pressure PA) by a static test method, and fitting by software through earlier-stage test data to obtain a function expression of an electromagnetic valve opening current IO, an electromagnetic valve closing current IC and the current working condition, wherein the current is defined as the opening current; the current required for shutdown at the present operating condition is defined as the shutdown current.
As shown in FIG. 2, a single duty cycle of the solenoid valve is divided into 6 stages, which are represented by Arabic numerals 1-6, respectively, as shown in FIG. 2. Where 1 represents the preload excitation phase, 2 represents the preload maintenance phase, 3 represents the on phase, 4 represents the on maintenance phase, 5 represents the off phase, and 6 represents the off maintenance. The end time of the phase 2 coincides with the rising edge time of the control signal, and the end time of the phase 4 coincides with the falling edge time of the control signal.
The method comprises the steps that a controller generates a control signal, before the rising edge of the control signal comes, the controller calculates the time required by increasing the current of a coil to a pre-loading current by adopting a pre-loading excitation voltage according to the current state of the coil and the parameters of the coil, the time is taken as the duration of a pre-loading excitation stage, the controller enters a stage 1 according to the duration of the pre-loading excitation stage, the controller triggers a duty ratio controller in advance, the duty ratio controller outputs a high-frequency square wave signal with the duty ratio of 100% to a voltage source, the voltage source starts to output a voltage square wave with the duty ratio of 100%, and the current of the coil quickly reaches the set pre-loading current under the excitation of the high voltage;
since the duration of phase 1 is calculated by the controller based on the current coil electrical parameters, the coil current reaches a preload current that is just slightly less than the turn-on current at the end of the duration of phase 1. At the moment, the duration of the stage 1 is finished, the stage 2 is entered, the controller triggers the duty ratio controller, the duty ratio controller outputs a high-frequency square wave signal with the duty ratio alpha to the voltage source, the voltage source starts to output a voltage square wave with the duty ratio alpha, wherein, alpha is more than 0 and less than 1, and under the action of the maintaining voltage, the coil current is always kept in a preloading current state, namely, the coil current surrounds a value slightly less than the starting current and is in a preloading current state with high-frequency small fluctuation.
After the stage 2 is finished, namely when the rising edge of the control signal comes, the stage 3 is entered, the controller triggers the duty ratio controller, the duty ratio controller outputs a high-frequency square wave signal with the duty ratio of 100% to the voltage source, the current of the coil rapidly rises under the excitation of the modulated voltage source, because the current is stabilized in a pre-loading current state before the rising edge of the control signal comes, the current rises to a starting current in a short time under the excitation of the modulated voltage source, the maintaining time of the voltage of the stage is equal to the time required by the voltage source which is modulated by the high-frequency square wave signal with the duty ratio of 100% to excite the electromagnetic valve to finish the stroke under the 0 current state of the electromagnetic valve;
after the stage 3 is finished, entering a stage 4, triggering a duty ratio controller by the controller, outputting a high-frequency square wave signal with a duty ratio of beta to a voltage source by the duty ratio controller, starting outputting a voltage square wave with the duty ratio of beta by the voltage source, wherein beta is more than 0 and less than 1, gradually reducing the coil current, and finally performing high-frequency small fluctuation around the value of a maintaining current, wherein the maintaining current is slightly larger than a closing current so as to keep the opening state of the electromagnetic valve;
after the stage 4 is finished, when the falling edge of the control signal comes, the stage 5 is entered, the controller triggers the duty ratio controller, the duty ratio controller outputs a high-frequency square wave signal with the duty ratio of-100% to the voltage source, the voltage source outputs reverse voltage, under the excitation of the reverse voltage, the coil current is rapidly reduced to be closed current, at the moment, the valve core starts to move, the reset is carried out, the voltage source continues to excite until the current is reduced to 0, and at the moment, the stage 5 is finished;
and after the stage 5 is finished, entering a stage 6, triggering the duty ratio controller by the controller, outputting a high-frequency square wave signal with the duty ratio of 0 to the voltage source by the duty ratio controller, and outputting a voltage square wave with the duty ratio of 0 by the voltage source, namely, not supplying power. Until the next cycle;
in the scheme, the value of the voltage output by the voltage source modulated by the high-frequency square wave signal with the duty ratio of alpha is less than the product of the resistance of the solenoid valve coil and the opening current, and is generally less than 5-10% of the product of the resistance of the solenoid valve coil and the opening current; the voltage value output by the voltage source after being modulated by the high-frequency square wave signal with the duty ratio of beta is larger than the product of the resistance of the solenoid valve coil and the closing current, and is generally larger than 5-10% of the product of the resistance of the solenoid valve coil and the closing current;
the calculation of the duration required for the pre-load excitation phase (phase 1) in the scheme is: the controller calculates the time required by the current of the coil to rise to the preloading current according to the current driving voltage, the current of the solenoid valve, the linear inductance resistance and the inductance, and the time is used as the duration time of the stage 1;
the duration required for the preload maintenance phase (phase 2) in the scheme is: the duration is 1-2 ms under normal conditions, and the duration can be increased or decreased properly according to different working conditions;
the calculation of the duration required for the start-up phase (phase 3) in the scheme is: the duration time of the voltage source modulated by the high-frequency square wave signal with the duty ratio of 100 percent is equal to the required time for the solenoid valve to complete the stroke by adopting the high-voltage source to excite the solenoid valve in a 0 current state, namely the duration time of the stage 3;
the calculation of the duration required for the maintenance phase (phase 4) in the scheme is: the time from the end time of the stage 3 to the arrival time of the falling edge of the control signal lasts;
the calculation of the duration required for the shutdown phase (phase 5) in the scheme is: the current after the stage 4 is reduced to 0 current for the required time under the excitation of a voltage source modulated by a high-frequency square wave signal with the duty ratio of-100%;
the calculation process of the duration required for the gap phase (phase 6) in the scheme is: the time that the end time of phase 5 lasts until the start time of the next phase 1.
As shown in fig. 3, which is a schematic diagram of the opening and closing characteristics of a solenoid valve driven by a single voltage of 24V, it can be seen from the figure that the opening of the solenoid valve lags behind 3ms, the opening movement lags behind 2ms, the closing movement lags behind 6.8ms, and the closing movement is 6.1ms after tests.
As shown in fig. 4, which is a schematic diagram of the opening and closing characteristics of the solenoid valve controlled by the high dynamic control method of the solenoid valve based on voltage pulse width modulation of the present invention, in this embodiment, the voltage source is 24V, and the duty ratios of the voltage square waves in the first to sixth stages are 100%, 33%, 100%, 20.8%, -100%, and 0%, respectively. Tests show that the opening lag is 0.2ms, the opening movement is 1.9ms, the closing lag is 0.1ms, and the closing movement is 1.7 ms. Compared with the scheme shown in the figure 3, the electromagnetic valve is provided with the preloading stage before the expected opening and closing time, so that the opening and closing delay time is greatly reduced; in the opening stage, the valve core of the electromagnetic valve is ensured to complete the expected working stroke by setting specific maintenance time; in the starting maintaining stage, the current of the coil is gradually reduced by loading a voltage square wave with a set duty ratio, and finally the high-frequency small fluctuation is carried out around the value of the maintaining current, wherein the maintaining current is slightly larger than the closing current; in the closing stage, the voltage source outputs reverse voltage, and under the excitation of the reverse voltage, the current of the coil is rapidly reduced to closing current until the current is reduced to 0; the dynamic characteristic of the closing stage of the electromagnet can be improved, and the time consumption of the closing stage of the electromagnetic valve is shortened.
Fig. 5 shows a comparative example in which the pre-loading stage only uses a voltage square wave with a duty cycle of 29.1%, and in this comparative example, the voltage source is 24V, the pre-loading stage duty cycle is 29.1%, the on-stage duty cycle is 100%, the on-sustain stage duty cycle is 20.8%, the off-stage duty cycle is-100%, and the off-sustain stage duty cycle is 0%. The test results show that the opening lag time is as follows: 0.5 ms; the opening movement time is as follows: 1.9 ms; the shut down lag time is: 0.2 ms; the closing movement time is: 1.8 ms.
As can be seen from the comparison between fig. 4 and fig. 5, under the condition that the voltage sources are the same, the invention loads the coil current by using the voltage square wave with the duty ratio of 100% in the preloading stage, so that the coil current can quickly reach the preloading current; compared with the comparative example, the invention greatly shortens the time required by the preloading stage, namely the invention can meet the requirement of higher frequency on-off and is suitable for occasions of high-frequency switches.