A high-precision motion control method for electromagnetic valve control system

Abstract

The present invention discloses a high-precision motion control method for an electromagnetic valve control system. The method calculates in real time the flow rate that the electromagnetic valve group currently needs to output to the controlled actuator, obtains the ratio of the flow rate to the maximum output flow rate of the electromagnetic valve group, and converts the ratio into a PWM wave duty cycle. When the duty cycle is not less than the lower limit of the duty cycle in the flow linear region, a traditional PWM wave synchronous control method is adopted. When the duty cycle is less than the lower limit of the duty cycle in the linear region, the controller obtains the equivalent duty cycle σ0 required at this time based on the flow ratio, and selects two PWM waves to control the two solenoid valves in the electromagnetic valve group in a phase-staggered manner. The time length t1 of the overlapping area of ​​the two PWM waves in one control cycle satisfies t1 = σ0 × T, where T is the time of one control cycle. The control effect of the electromagnetic valve group is to achieve the required actual flow output. The present invention can meet the high-precision control requirements when the hydraulic actuator approaches the target position.

Description

Technical Field

[0001] The present invention belongs to the field of electromagnetic valve control, and in particular relates to a high-precision motion control method for an electromagnetic valve control system. Background Art

[0002] Hydraulic technology, with its high power density and high output force, plays an irreplaceable role in many applications, such as machine tool manufacturing, heavy machinery, and aerospace equipment. Hydraulic actuators are the core control elements of hydraulic systems, and the accuracy of their displacement and speed control directly affects the performance and efficiency of the entire system.

[0003] Current valve-controlled systems typically utilize proportional valves, which output a continuous flow, to control the motion of hydraulic actuators. However, these valves suffer from issues such as deadband and leakage, as well as large hysteresis and low frequency response, making them inadequate for applications requiring high response speed and control accuracy. To address this issue, digital hydraulic technology employs pulse-width modulation (PWM) to control the solenoid valve's opening and closing signals, thereby regulating flow output.

[0004] However, due to the movement lag time and movement time of the opening and closing of the solenoid valve, when the hydraulic actuator approaches the target position, the required output flow is small. At this time, under the existing pulse width modulation method, the solenoid valve is controlled by a low duty cycle PWM wave, such as Figure 1 and Figure 2 As shown in the figure, the solenoid valve will fall into the dead zone and nonlinear zone. The dead zone means that the solenoid valve cannot be opened and closed, and the output flow is 0 at this time; the nonlinear zone means that the solenoid valve is not completely opened and closed, and the valve core movement is in an unstable state. At this time, the solenoid valve is very likely to fail to open and close due to changes in working conditions. The flow output of the solenoid valve each time it is opened and closed is uncertain, so the system cannot achieve high-precision displacement control when the hydraulic actuator approaches the target position. Summary of the Invention

[0005] To address the problems in the prior art, the present invention proposes a high-precision motion control method for an electromagnetic valve control system. The electromagnetic valve control system of the present invention includes a controller, a PWM control module controlled by the controller, a plurality of electromagnetic valve groups driven by the PWM control module, and a controlled actuator. Each electromagnetic valve group includes a first electromagnetic valve connected to the oil inlet of the controlled actuator and a second electromagnetic valve connected to the oil outlet of the controlled actuator. Because the first electromagnetic valve and the second electromagnetic valve are respectively connected to the oil inlet and oil outlet of the controlled actuator, when either electromagnetic valve is in the closed state, the oil circuit of the controlled actuator is shut off. Only when both the first electromagnetic valve and the second electromagnetic valve in the electromagnetic valve group are open can the oil in the oil circuit controlled by the electromagnetic valve group of the controlled actuator flow, and the controlled actuator can perform its action.

[0006] It should be noted that the present invention uses PWM waves to control the solenoid valves in the solenoid valve group. PWM waves are pulse-width modulated waves. Within a given control cycle, a high PWM wave indicates that the controlled solenoid valve is energized and open, while a low PWM wave indicates that the controlled solenoid valve is closed. The proportion of time the PWM wave is high within a control cycle is the duty cycle of the PWM wave. By changing the PWM wave's duty cycle, the on-time of the controlled solenoid valve within a control cycle can be changed, thereby changing the output flow rate of the solenoid valve within a cycle. A duty cycle of 100% indicates that the controlled solenoid valve is open throughout the entire control cycle. A single control cycle is very short, and the flow rate of the solenoid valve fluctuates within a single cycle (flow output when high, no flow output when low). Therefore, in the art, the average flow rate is generally used to indicate the actual output flow rate of a solenoid valve or solenoid valve group per unit time (including multiple control cycles). Unless otherwise specified, the flow rate in the present invention refers to the average flow rate.

[0007] The high-precision motion control method of the electromagnetic valve control system provided by the present invention comprises the following steps:

[0008] 1) Given the target control quantity of the controlled actuator, the controller detects the real-time feedback quantity of the controlled actuator in real time, obtains the flow rate that the solenoid valve group currently needs to output to the controlled actuator, and obtains the ratio of this flow rate to the maximum output flow rate of the solenoid valve group;

[0009] 2) Based on the obtained flow ratio, the duty cycle σ required to be output by the PWM control module is obtained from the regulated flow characteristic curve;

[0010] When the duty cycle σ is greater than or equal to the duty cycle lower limit σ1 in the flow linear region of the flow characteristic curve, the controller controls the PWM control module to output a PWM wave with exactly the same duty cycle σ to control the two solenoid valves in the solenoid valve group to open and close synchronously;

[0011] When the required duty cycle σ is less than the duty cycle lower limit σ1 in the flow linear region, the controller obtains the required equivalent duty cycle σ0 from the regulated flow characteristic curve according to the flow ratio, and selects two PWM waves with the same duty cycle σ′ and the same period to control the two solenoid valves in the solenoid valve group in a phase-staggered manner. The time length t1 of the overlapping area of ​​the two PWM waves in one control cycle satisfies t1 = σ0 × T, where T is the time of one control cycle. The control effect of the solenoid valve group is to achieve the required actual flow output;

[0012] 3) Repeat steps 1) and 2) until the controlled actuator reaches the target control amount.

[0013] Furthermore, the duty cycle σ′ satisfies: σ1≤σ′≤50%, and σ′ is preferably 50%.

[0014] Furthermore, the controller pre-stores a regulated flow characteristic curve, which is obtained by the following steps:

[0015] 2.1) Obtain flow characteristic curve

[0016] Under fixed opening and closing frequency and pressure difference, the duty cycle of the PWM wave that controls the opening and closing of the solenoid valve is modulated from 0 to 100%, and the flow rate of the oil outlet of a single solenoid valve is measured at different duty cycles. This value is divided by the maximum flow rate when the solenoid valve is fully open to obtain the flow ratio. Then, the relationship curve between the flow ratio and the duty cycle is obtained, that is, the flow characteristic curve;

[0017] 2.2) Distinguish between the linear region and the nonlinear region in the flow characteristic curve, and correct the portion of the flow characteristic curve where the duty cycle is less than the lower limit σ1 of the duty cycle in the flow linear region;

[0018] The correction method is as follows: connecting a first solenoid valve to the oil inlet of the controlled actuator, and a second solenoid valve to the oil outlet of the controlled actuator; using two PWM waves with a duty cycle of 50% and the same period to drive the first solenoid valve and the second solenoid valve respectively; controlling the two PWM waves to be staggered in phase so that the overlapping time length t1 of the two PWM waves varies within the range of 0-0.5T, where T is the time of one control cycle, setting the equivalent duty cycle σ0 = t1 / T, measuring the oil flow of the controlled actuator under different equivalent duty cycles σ0, dividing the oil flow by the maximum oil flow when the first solenoid valve and the second solenoid valve are fully open to obtain a flow ratio, and then obtaining a relationship curve between the flow ratio and the equivalent duty cycle σ0; replacing the part of the flow characteristic curve obtained in step 1) where the duty cycle σ is less than σ1 with the part where the duty cycle σ is less than σ1 in the relationship curve between the flow ratio and the equivalent duty cycle; thereby obtaining a regulated flow characteristic curve.

[0019] Furthermore, the controlled actuator is a symmetrical hydraulic cylinder, an asymmetrical hydraulic cylinder or a hydraulic motor;

[0020] When the controlled actuator is a symmetrical hydraulic cylinder or an asymmetrical hydraulic cylinder, the target control amount is the target displacement of the piston in the controlled actuator, and the real-time feedback amount of the controlled actuator detected by the controller is the real-time displacement of the piston;

[0021] When the controlled actuator is a hydraulic motor, the target control amount is the target speed of the output shaft of the controlled actuator, and the real-time feedback amount of the controlled actuator detected by the controller is the real-time speed of the output shaft.

[0022] Furthermore, the flow rate that the solenoid valve group currently needs to output to the controlled actuator as described in step 1) is obtained as follows: the controller obtains the difference between the target control amount and the real-time feedback amount of the controlled actuator, and calculates the flow rate that the solenoid valve group currently needs to output to the controlled actuator based on the value; the flow rate is divided by the maximum output flow rate when the solenoid valve group is fully open to obtain the flow ratio.

[0023] Compared with the existing ones, the present invention has the following beneficial effects:

[0024] The high-precision motion control method (dual-channel PWM phase-staggered technology) proposed in this invention for solenoid valve control systems effectively prevents the solenoid valve from operating in the nonlinear region, preventing unstable opening and closing. When the required duty cycle enters the nonlinear region, the control signals (PWM) of the solenoid valves connected to the actuator's oil inlet and outlet are phase-staggered, staggering the movement of the valve spools controlling the two valves. This allows the valve spools to maintain full opening and closing, while delivering the desired equivalent flow rate.

[0025] This invention effectively improves flow control accuracy. The system combines traditional digital hydraulic control methods (pulse width modulation) with dual-channel PWM phase-staggered technology. Within the linear region, PWM technology is used to precisely adjust the duty cycle based on feedback. Outside the linear region, dual-channel PWM phase-staggered technology is used to precisely adjust the overlap time (t1) based on feedback, achieving more precise oil control. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the solenoid valve core displacement under different duty cycles;

[0027] Figure 2 is the flow characteristic curve of the solenoid valve;

[0028] Figure 3 This is the principle diagram of dual-channel PWM phase shift technology;

[0029] Figure 4 Schematic diagram of the full-bridge valve control system;

[0030] Figure 5 is the flow characteristic curve;

[0031] Figure 6 This is the system logic block diagram. DETAILED DESCRIPTION

[0032] The present invention will be further described and illustrated below in conjunction with specific embodiments. The embodiments are merely illustrative of the present disclosure and do not limit its scope. The technical features of the various embodiments of the present invention may be combined accordingly, provided that there is no conflict between them.

[0033] The movement of the hydraulic actuator requires the simultaneous flow of oil at its inlet and outlet ports, which requires the solenoid valves connecting the two ports to be opened at the same time. When the solenoid valve at any end is closed, the hydraulic actuator will stop moving. In traditional digital hydraulic control technology (pulse width modulation), the PWM that controls the solenoid valves connected to the inlet and outlet ports is synchronized, and the system regulates the amount of output oil by adjusting the duty cycle of PWM. Specifically, the system controls the flow by adjusting the duty cycle of the PWM wave to control the opening and closing time of the valve core in a single cycle. Increasing the duty cycle can increase the flow output by the valve, making the inlet and outlet of the hydraulic actuator and the oil intake and discharge faster, thereby increasing the movement speed of the hydraulic actuator; decreasing the duty cycle can reduce the flow output by the valve and reduce the movement speed of the hydraulic actuator.

[0034] This method is suitable for initial displacement control. In the initial displacement, the displacement required by the hydraulic actuator is large, the required PWM duty cycle is large and is in the flow linear region (such as Figure 2 As shown, in contrast, a smaller duty cycle may be in the nonlinear region. It should be noted that a larger PWM duty cycle may also be in the nonlinear region. However, in this case, the overall output flow is large, and high-precision control is not required. Furthermore, the high-precision control of the present invention focuses only on the situation when the hydraulic actuator approaches the target position. Therefore, high-precision control is only performed on the portion where the duty cycle is smaller than the nonlinear region. As the required displacement decreases, the required duty cycle also decreases. When the duty cycle output by the controller enters the nonlinear flow region, the valve core cannot be fully opened or closed.

[0035] To this end, the present invention proposes a valve control system control method based on dual-channel PWM phase stagger technology to control hydraulic actuators.

[0036] like Figure 3This is the principle diagram of the dual-channel PWM phase-shifting technology of the present invention. The blue dotted line is the PWM wave (PWM1) of the first solenoid valve connected to the oil inlet, and the red dotted line is the PWM wave (PWM2) of the second solenoid valve connected to the oil outlet. The cycle time of PWM1 and PWM2 is the same (both are T1). Taking the hydraulic cylinder as an example of a hydraulic actuator, the displacement of the hydraulic cylinder can only be carried out when the solenoid valves connected to the inlet and outlet are both open. At this time, the PWM waves controlling the two solenoid valves are both high potential. When the PWM waves controlling the solenoid valves are phase-shifted (shifted time t), the valve core movement of the two solenoid valves is also shifted. The interval that actually works is the intersection of the two valve opening intervals, and this intersection is defined as the equivalent valve core movement. The intersection of the high levels of the two PWM waves is taken and defined as the high level of the equivalent PWM. The remaining intervals of a single cycle are defined as the low level of the equivalent PWM. The equivalent duty cycle is the time of the equivalent PWM high level (t1) divided by the cycle time (T1). The overall output flow of the system is positively correlated with the size of the equivalent duty cycle. The size of the equivalent duty cycle can be adjusted by adjusting the phase of the two PWM waves.

[0037] When approaching the target displacement, the traditional digital hydraulic control method still requires two solenoid valves to control the opening and closing of the solenoid valves under low duty cycle PWM (PWM3), but under low duty cycle, the solenoid valves will fall into the dead zone or nonlinear zone. Figure 3 As shown in the figure, the valve core is in an incompletely open and closed state, and the flow rate output by the solenoid valve is uncertain during each opening and closing cycle. However, under the control method proposed in this invention, by adjusting the staggered opening time (t) and aligning the equivalent duty cycle with the PWM3 duty cycle, the equivalent valve core movement remains fully open and closed, and the solenoid valve output flow rate remains stable, enabling high-precision displacement control of the actuator as it approaches the target position.

[0038] The above is the basic principle of the control method. The control method can be applied to a variety of valve control systems S, including full bridge, bypass throttling, etc. The actuators controlled by the valve control system can be symmetrical hydraulic cylinders, asymmetrical hydraulic cylinders, hydraulic motors, etc.

[0039] Take the full-bridge valve control system as an example, Figure 4 As shown in FIG, the system consists of a controller, four PWM control modules (1, 2, 3, and 4), a displacement monitoring module of the controlled actuator, four normally closed solenoid valves, and a controlled actuator (asymmetric hydraulic cylinder).

[0040] The controller receives the detection signal from the displacement detection module according to the hydraulic cylinder displacement and displacement direction set by the user, and sends modulation signals to the four PWM control modules to adjust the duty cycle and overlap time (t1) of the PWM wave.

[0041] PWM control module: receives the modulation signal (PWM wave signal) from the controller and outputs the corresponding driving voltage to the solenoid valve;

[0042] Displacement monitoring module: detects the load displacement of the hydraulic cylinder and sends the displacement to the controller;

[0043] Working principle of full-bridge valve control system:

[0044] The two ports of the hydraulic cylinder (Port A and Port B) are connected to two solenoid valves, respectively. Solenoid valves 1 and 4 are connected to the oil inlet (Port P), and solenoid valves 2 and 3 are connected to the oil outlet (Port T). The controller controls the PWM duty cycle of the four solenoid valves to control the direction and flow rate of the oil at Ports A and B, thereby controlling the direction and displacement of the hydraulic cylinder.

[0045] The following effects can be achieved through this system:

[0046] Forward movement: solenoid valves 2 and 4 are closed (duty cycle is 0%), and solenoid valves 1 and 3 are opened (equivalent duty cycle is greater than 0%), which allows the rodless chamber to receive high-pressure oil while the rod chamber discharges low-pressure oil.

[0047] Reverse movement: solenoid valves 1 and 3 are closed (duty cycle is 0%), and solenoid valves 2 and 4 are opened (equivalent duty cycle is greater than 0%), so that the rod chamber receives high-pressure oil while the rodless chamber discharges low-pressure oil.

[0048] Hovering motion: There are three control methods to achieve the hovering of the hydraulic cylinder.

[0049] ① Solenoid valves 1, 2, 3, and 4 are closed (duty cycle 0%); ② Solenoid valves 2 and 4 are closed (duty cycle 0%), while solenoid valves 1 and 3 are open, with an equivalent duty cycle of 0%; ③ Solenoid valves 1 and 3 are closed (duty cycle 0%), while solenoid valves 2 and 4 are open, with an equivalent duty cycle of 0%. These three control methods can keep the oil in the two chambers stationary, allowing the load to hover at a specific position.

[0050] The controller of the present invention pre-stores a regulated flow characteristic curve, which is obtained by the following steps:

[0051] First, obtain the flow characteristic curve (the relationship curve between the current average flow of the solenoid valve / the percentage ratio of the maximum output flow of the valve and the duty cycle):

[0052] Under fixed opening and closing frequency and pressure difference, the duty cycle of the PWM wave that controls the opening and closing of the solenoid valve is modulated from 0 to 100%, and the flow rate of the oil outlet of a single solenoid valve is measured at different duty cycles. This value is divided by the maximum flow rate when the solenoid valve is fully open to obtain the flow ratio. Then, the relationship curve between the flow ratio and the duty cycle is obtained, that is, the flow characteristic curve;

[0053] Then distinguish the linear region and nonlinear region in the flow characteristic curve, obtain the starting and ending points (σ1, σ2) of the flow linear region, and correct the portion of the flow characteristic curve where the duty cycle is less than the lower limit σ1 of the duty cycle in the flow linear region;

[0054] The correction method is as follows: connecting a first solenoid valve to the oil inlet of the controlled actuator, and a second solenoid valve to the oil outlet of the controlled actuator; using two PWM waves with a duty cycle of 50% and the same period to drive the first solenoid valve and the second solenoid valve respectively; controlling the two PWM waves to be staggered in phase so that the overlapping time length t1 of the two PWM waves varies within the range of 0-0.5T, where T is the time of one control cycle, setting the equivalent duty cycle σ0 = t1 / T, measuring the oil flow of the controlled actuator under different equivalent duty cycles σ0, dividing the oil flow by the maximum oil flow when the first solenoid valve and the second solenoid valve are fully open to obtain a flow ratio, and then obtaining a relationship curve between the flow ratio and the equivalent duty cycle σ0; replacing the part of the flow characteristic curve obtained in step 1) where the duty cycle σ is less than σ1 with the part where the duty cycle σ is less than σ1 in the relationship curve between the flow ratio and the equivalent duty cycle; thereby obtaining a regulated flow characteristic curve.

[0055] When the duty cycle corresponding to the percentage ratio of the current average flow rate of the solenoid valve to the maximum output flow rate is less than the starting point of the linear region σ1, the duty cycle is in the nonlinear region. At this time, the system needs to adopt the dual-channel PWM phase staggering method of the present invention for high-precision control. The red curve is the flow characteristic curve after regulation measured in advance. The controller obtains the equivalent duty cycle σ0 required at this time from the flow characteristic curve after regulation based on the flow ratio, and selects two PWM waves with the same duty cycle σ′ and the same period to control the two solenoid valves in the solenoid valve group in a phase-staggered manner. The time length t1 of the overlapping area of ​​the two PWM waves in one control cycle satisfies t1 = σ0 × T, where T is the time of one control cycle. The control effect of the solenoid valve group is to achieve the required actual flow output;

[0056] On this basis, if Figure 5As shown, a reference flow linearization curve can also be introduced within the controller to establish a linear relationship between the command signal and valve flow in the control system. All values ​​on the regulated flow characteristic curve are mapped one-to-one with all values ​​on the reference flow characteristic curve, establishing a linear relationship between the command signal and valve flow in the control system. For example, at a 20% average flow / maximum output flow ratio, the equivalent duty cycle on the regulated flow characteristic curve is σ0. Given a 20% duty cycle on the reference flow linearization curve, the controller establishes a one-to-one mapping relationship between the equivalent duty cycle σ0 and the 20% duty cycle on the reference flow linearization curve. When the external environment requires a 20% average flow / maximum output flow ratio, the controller generates a command of 0.2 and obtains the equivalent duty cycle σ0 through the established mapping relationship. At this point, the controller only needs to store the mapping relationship between the command and the equivalent duty cycle σ0. Similarly, by repeating the above steps for the remaining values ​​on the regulated flow characteristic curve, the regulated flow characteristic curve can be mapped to the reference flow linearization curve, establishing a linear relationship between the command signal and valve flow in the control system.

[0057] like Figure 6 As shown, the control method of the present invention includes the following steps:

[0058] 1) Given the target control quantity of the controlled actuator, the controller detects the real-time feedback quantity of the controlled actuator in real time, obtains the flow rate that the solenoid valve group currently needs to output to the controlled actuator, and obtains the ratio of this flow rate to the maximum output flow rate of the solenoid valve group;

[0059] The conventional method in the valve orifice field is to obtain the current flow rate that needs to be output to the controlled actuator by detecting the real-time feedback amount and the set target control amount. For example, when the target control amount is the displacement, the target displacement X0 is taken as the difference between the actuator displacement X, and this value is passed through the control algorithm (such as the PID algorithm) to calculate the required movement speed V1 of the actuator. The controller takes the derivative of the real-time displacement X to obtain the actuator displacement speed V0, and this value is passed through the control algorithm (such as the PID algorithm) to obtain the required average flow rate, which is divided by the maximum output flow rate of the valve to obtain the ratio. When the target control amount is speed, the difference is taken from the required target speed, and this value is passed through the control algorithm (such as the PID algorithm) to obtain the required average flow rate, and then the ratio is obtained.

[0060] 2) Based on the obtained flow ratio, the duty cycle σ required to be output by the PWM control module is obtained from the regulated flow characteristic curve;

[0061] When the duty cycle σ is greater than or equal to the duty cycle lower limit σ1 in the flow linear region of the flow characteristic curve, the controller controls the PWM control module to output a PWM wave with exactly the same duty cycle σ to control the two solenoid valves in the solenoid valve group to open and close synchronously;

[0062] When the required duty cycle σ is less than the duty cycle lower limit σ1 in the flow linear region, the controller obtains the required equivalent duty cycle σ0 from the regulated flow characteristic curve according to the flow ratio, and selects two PWM waves with the same duty cycle σ′ and the same period to control the two solenoid valves in the solenoid valve group in a phase-staggered manner. The time length t1 of the overlapping area of ​​the two PWM waves in one control cycle satisfies t1 = σ0 × T, where T is the time of one control cycle. The control effect of the solenoid valve group is to achieve the required actual flow output;

[0063] 3) Repeat steps 1) and 2) until the controlled actuator reaches the target control amount.

[0064] For example, if the actual average flow rate required is 20% of the valve's maximum flow rate (less than the duty cycle lower limit in the linear region), the controller only needs to generate a command of 0.2 to obtain the equivalent duty cycle signal σ0 actually required by the solenoid valve. Multiplying the equivalent duty cycle signal σ0 by the solenoid valve's control period T yields the PWM wave overlap time t1. This overlap time is then transmitted to the PWM control module, and the PWM waves controlling the two solenoid valves are staggered by a certain amount to achieve an overlap time of t1. The resulting control effect of the solenoid valve group is to achieve an actual flow output of 20% of the valve's maximum flow rate. In this way, the control system maintains a linear relationship without having to directly address the valve's nonlinear flow characteristics.

[0065] Furthermore, when controlling two solenoid valves within a solenoid valve group with their phases staggered, the two PWM waves should have the same period and the same duty cycle σ′, with only a phase shift. The PWM duty cycle σ′ can be selected within a certain range, but must satisfy the following conditions: σ1 ≤ σ′ ≤ 50% to ensure that the overlap period reaches t1. If σ′ exceeds 50%, and the required overlap time t1 is short, one PWM wave will overlap with the other PWM wave for two periods. Therefore, σ′ is preferably set to 50%.

[0066] The system uses different control methods by judging the required duty cycle. When the required duty cycle is in the linear region, the system uses traditional digital hydraulic control technology (pulse width modulation); when the hydraulic actuator approaches the target position, the system needs to output a small flow of oil, and the required duty cycle is less than the starting point of the linear region. The system will use dual-channel PWM phase staggered technology to control the hydraulic actuator, which effectively prevents the valve from operating in the nonlinear region and improves the accuracy of flow control.

[0067] The above-described embodiments merely illustrate several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. Persons skilled in the art will readily appreciate that variations and modifications may be made without departing from the scope of the present invention, all of which fall within the scope of protection of the present invention.

Claims

1. A high-precision motion control method for a solenoid valve control system, the solenoid valve control system comprising a controller, a PWM control module controlled by the controller, a plurality of solenoid valve groups driven by the PWM control module, and a controlled actuator, each solenoid valve group comprising a first solenoid valve connected to an oil inlet of the controlled actuator and a second solenoid valve connected to an oil outlet of the controlled actuator; It is characterized by: The high-precision motion control method comprises the following steps: 1) Given the target control quantity of the controlled actuator, the controller detects the real-time feedback quantity of the controlled actuator in real time, obtains the current flow rate that the solenoid valve group needs to output to the controlled actuator, and obtains the ratio of this flow rate to the maximum output flow rate of the solenoid valve group; 2) Based on the obtained flow ratio, obtain the duty cycle that the PWM control module needs to output from the regulated flow characteristic curve ; When the duty cycle Greater than or equal to the lower limit of the duty cycle in the flow linear region of the flow characteristic curve When the controller controls the PWM control module to output the same duty cycle as The PWM wave controls the two solenoid valves in the solenoid valve group to open and close synchronously; When the required duty cycle Less than the lower limit of the duty cycle in the flow linear region When the flow ratio is 0, the controller obtains the equivalent duty cycle required at this time from the regulated flow characteristic curve. , and select the duty cycle to be The two PWM waves with the same period control the two solenoid valves in the solenoid valve group in a phase-shifted manner, and the time length t1 of the overlapping area of ​​the two PWM waves in one control cycle satisfies , where T is the time of a control cycle, and the control effect of the solenoid valve group is to achieve the required actual flow output; 3) Repeat steps 1) and 2) until the controlled actuator reaches the target control amount.

2. The high-precision motion control method of the electromagnetic valve control system according to claim 1, characterized in that: Duty cycle satisfy: ≤ ≤50%.

3. The high-precision motion control method of the electromagnetic valve control system according to claim 1, characterized in that: The controller pre-stores a regulated flow characteristic curve, which is obtained by the following steps: 21) Obtain flow characteristic curve Under fixed opening and closing frequency and pressure difference, the duty cycle of the PWM wave that controls the opening and closing of the solenoid valve is modulated from 0 to 100%, and the flow rate of the oil outlet of a single solenoid valve is measured at different duty cycles. This value is divided by the maximum flow rate when the solenoid valve is fully open to obtain the flow ratio. Then, the relationship curve between the flow ratio and the duty cycle is obtained, that is, the flow characteristic curve; 22) Distinguish the linear and nonlinear regions in the flow characteristic curve, and make the duty cycle on the flow characteristic curve less than the lower limit of the duty cycle in the linear region. revise the parts; The correction method is as follows: connect the first solenoid valve to the oil inlet of the controlled actuator, and the second solenoid valve to the oil outlet of the controlled actuator; use two PWM waves with a duty cycle of 50% and the same period to drive the first solenoid valve and the second solenoid valve respectively; control the two PWM waves to be staggered in phase so that the overlapping time length t1 of the two PWM waves varies within the range of 0-0.5T, where T is the time of one control cycle, and the equivalent duty cycle , measured at different equivalent duty cycles The oil flow of the controlled actuator is divided by the maximum oil flow when the first solenoid valve and the second solenoid valve are fully open to obtain the flow ratio, and then the flow ratio and the equivalent duty cycle are obtained. The relationship curve between the flow ratio and the equivalent duty cycle is shown in Figure 2. Less than Replace the duty cycle in the flow characteristic curve obtained in step 1) with Less than part, thereby obtaining the flow characteristic curve after regulation.

4. The high-precision motion control method of the electromagnetic valve control system according to claim 3, characterized in that: The linear region in the flow characteristic curve is the part where the flow ratio and the duty cycle are linearly related. The minimum duty cycle in the linear region is the lower limit of the duty cycle. .

5. The high-precision motion control method of the electromagnetic valve control system according to claim 1, characterized in that: Only when both solenoid valves in the solenoid valve group are in the open state can the oil in the oil circuit of the controlled actuator flow and the controlled actuator can perform the action; that is, when two PWM waves control the two solenoid valves in the solenoid valve group in a staggered manner, the two solenoid valves are in the open state and the controlled actuator can perform the action only within the time range of the overlapping area of ​​the PWM waves.

6. The high-precision motion control method of the electromagnetic valve control system according to claim 1, characterized in that: The controlled actuator is a symmetrical hydraulic cylinder, an asymmetrical hydraulic cylinder or a hydraulic motor; When the controlled actuator is a symmetrical hydraulic cylinder or an asymmetrical hydraulic cylinder, the target control amount is the target displacement of the piston in the controlled actuator, and the real-time feedback amount of the controlled actuator detected by the controller is the real-time displacement of the piston; When the controlled actuator is a hydraulic motor, the target control amount is the target speed of the output shaft of the controlled actuator, and the real-time feedback amount of the controlled actuator detected by the controller is the real-time speed of the output shaft.

7. The high-precision motion control method of the electromagnetic valve control system according to claim 1, characterized in that: The flow rate that the solenoid valve group currently needs to output to the controlled actuator as described in step 1) is specifically obtained as follows: the controller calculates the flow rate that the solenoid valve group currently needs to output to the controlled actuator based on the difference between the target control amount and the real-time feedback amount of the controlled actuator; and divides the flow rate by the maximum output flow rate when the solenoid valve group is fully open to obtain the flow ratio.

8. The high-precision motion control method of the electromagnetic valve control system according to claim 1, characterized in that: The two solenoid valves in the solenoid valve group are identical.

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