A closed-loop control method for electro-hydraulic continuously variable valve opening duration

Abstract

The application discloses a kind of electro-hydraulic variable valve opening duration continuous variable closed-loop control methods, belong to valve opening state identification technical field, comprising: the laser displacement sensor for detecting valve lift signal is installed in the lift end of electro-hydraulic variable valve, the calibration of opening time and closing time is carried out to each state valve data collected in Matlab, valve opening identification algorithm and valve closing identification algorithm used in Matlab offline test are written into ECU to carry out multiple-cycle open-loop test;With the identification valve opening duration as closed-loop feedback input, PID closed-loop controller is used to control valve to track target and realize the closed-loop switching of variable duration.The application can reduce the steady-state error of valve opening duration and realize continuous variable of arbitrary duration by taking the identification valve opening duration as feedback closed-loop control high-frequency solenoid valve high-frequency signal under the multiple-cycle operation of valve.

Description

Technical Field

[0001] This invention belongs to the field of valve opening state recognition technology, specifically relating to a closed-loop control method for a continuously variable electro-hydraulic variable valve opening duration. Background Technology

[0002] Traditional mechanical cam-driven valves, due to their fixed phase, lift, and cam profile parameters, cannot meet the optimal needs of diesel engines under various operating conditions. In contrast, camless variable valve timing technology completely breaks the constraints of the camshaft and cam profile, thus enabling flexible and independent adjustment of scavenging phase, opening duration, and lift according to operating conditions. This makes it possible for the scavenging process to achieve true optimal performance under various steady-state engine conditions. Simultaneously, it allows for precise and rapid adjustment of the scavenging process, similar to ignition and injection, based on each cycle, significantly improving engine transient performance. Electro-hydraulic variable valve timing mechanisms, which directly drive valves through hydraulic pressure, are widely considered a promising camless valve timing mechanism. Due to the design flexibility, high power density, and compatibility of hydraulic oil sources, the high-pressure fluid flow rate driving the valve movement can be controlled through various active or passive methods, resulting in a rapid and flexible controllable valve movement trajectory and achieving soft-landing characteristics. Because there is no strict motion constraint from the camshaft, the accuracy of the operating parameters (timing, lift, opening and closing response, seat speed, etc.) of camless variable valves is affected. Electro-hydraulic variable valve mechanisms are subject to interference from various nonlinear factors, such as the increase in hydraulic oil viscosity with decreasing temperature and fluctuations in system hydraulic force. These factors all affect the accuracy of the target valve operating parameters. In particular, the cyclical variation of valve operating parameters will lead to cyclical variations in the engine. Therefore, it is essential to employ certain control measures to improve the consistency of the electro-hydraulic variable valve's motion cycle. For the closed-loop control of variable valve motion, information on the operating parameters of the controlled valve can be obtained directly or indirectly, and used for closed-loop feedback control to improve control performance. For electro-hydraulic variable valves, non-contact displacement sensors are generally used to provide real-time feedback on valve lift. In this way, information such as valve timing, response time, and seat speed can be obtained in real time through the valve lift signal and used for closed-loop feedback control of valve motion. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a closed-loop control method with a continuously variable electro-hydraulic variable valve opening duration, which is used to solve the problems of large steady-state error and poor stability of multi-cycle operation in the prior art.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] This invention provides a closed-loop control method for an electro-hydraulic variable valve with a continuously variable opening duration, comprising the following steps:

[0006] S1: Install the laser displacement sensor for detecting valve lift signal at the lift end of the electro-hydraulic variable valve. Under open-loop control, collect valve profile data of the electro-hydraulic valve in multiple cycles under various operating conditions. After processing the valve profile data, extract the single valve cycle under each operating condition as a valve profile feature analysis sample.

[0007] S2: Design a closed-loop control system for valve opening duration, using the valve opening duration as the closed-loop feedback input. The target valve opening duration T during valve operation. * Compared with the actual valve opening duration T of the previous cycle k The difference is the control variable of the closed-loop controller, and this is used as the input to obtain the control output value of the high-frequency solenoid valve to control the duration of the high-level signal of the high-frequency solenoid valve, thereby controlling the valve opening duration of the next cycle.

[0008] S3: On the electro-hydraulic variable valve test platform, the controller controls the valve to track the target and achieves the closed-loop switching effect of variable duration. When the valve is running in multiple cycles, the displacement sensor detects the valve lift profile data in real time and transmits it to the ECU. The valve opening recognition algorithm and valve closing recognition algorithm written in the ECU controller identify the opening and closing time of the valve in the previous valve cycle based on the detected valve lift, and adjust the valve opening duration of the next cycle in real time through the closed-loop control algorithm.

[0009] S4: Adjust the proportional unit and integral unit in the control parameters of the closed-loop controller to achieve the best stability of the valve opening duration during multi-cycle operation under preset conditions;

[0010] S5: The steady-state error of valve multi-cycle operation is evaluated using the following formula:

[0011]

[0012] Where error is the error between the actual valve opening time and the target, t rdi Let t be the actual valve opening time in the i-th cycle. gd Let n be the target valve opening duration, and n be the total number of cycles.

[0013] Furthermore, the valve opening recognition algorithm includes: when the valve is in the closed state, detecting the valve position l at the time of detection. n Compare with the valve position threshold l0, if l n If the value is greater than 10, then the valve opening time marker count C will be incremented. start Increment by 1, and determine the start time flag count C. start The magnitude of the valve set count threshold k, if C start>k, it is considered that the valve meets the opening judgment condition, the valve opens, the valve opening identifier flag = 1, and C is initialized start ; On the contrary, if l n <l0, it is considered that the valve is closed and C is initialized start .

[0014] Furthermore, the valve closing recognition algorithm includes: when the valve is in the open state, the valve position l at the detection moment n is compared with the valve position l at the previous moment n―1 . If l n ≥l n―1 and l n―1 ≥l c , it indicates that the valve is closed, and the valve opening judgment identifier flag = 0 is set.

[0015] Furthermore, in step S3, the verification method is to calibrate the opening moment and closing moment of the valve data in each state collected in Matlab, and write the valve opening recognition algorithm and valve closing recognition algorithm used in the Matlab offline test into the ECU for multi-cycle open-loop testing.

[0016] The beneficial effects of the present invention are as follows:

[0017] The present invention proposes a method for identifying the opening and closing moments of an electro-hydraulic variable valve under any operating conditions. It can accurately identify the opening and closing moments of the valve during multi-cycle operation of the valve, and then use the identified valve opening duration as feedback to close the loop to regulate the high-frequency signal of the high-frequency solenoid valve, reduce the steady-state error of the valve opening duration, and achieve continuous variation of any duration.

[0018] Other advantages, objectives, and features of the present invention will be described in the subsequent specification, and are to some extent obvious to those skilled in the art, or those skilled in the art can obtain teachings from the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the following specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to make the objectives, technical solutions, and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration:

[0020] Figure 1 is the PID control flow chart of the embodiment of the present invention;

[0021] Figure 2 is the open-loop and closed-loop comparison diagram of the electro-hydraulic valve multi-cycle operation with a working condition of 500 rpm / 240°CA in the embodiment of the present invention;

[0022] Figure 3This is the open-loop and closed-loop comparison diagram of the multi-cycle operation of the electro-hydraulic valve under the working condition of 1000 rpm / 240°CA in the embodiment of the present invention;

[0023] Figure 4 This is the open-loop and closed-loop comparison diagram of the multi-cycle operation of the electro-hydraulic valve under the working condition of 1500 rpm / 240°CA in the embodiment of the present invention;

[0024] Figure 5 This is the open-loop and closed-loop comparison diagram of the multi-cycle operation of the electro-hydraulic valve under the working condition of 2000 rpm / 240°CA in the embodiment of the present invention. Detailed implementation manners

[0025] As Figures 1-2 shown, the present invention provides a closed-loop control method for continuously variable electro-hydraulic variable valve opening duration, including the following steps:

[0026] Step 1: Install a laser displacement sensor for detecting the valve lift signal at the lift end of the electro-hydraulic variable valve, set the valve position threshold l0, and collect the valve profile data of the electro-hydraulic valve under multiple working conditions in multi-cycle operation under open-loop control.

[0027] Step 2: Process the valve profile data and extract a single valve cycle under each working condition as a valve profile feature analysis sample;

[0028] Step 3: Analyze the characteristics of the valve opening and closing profile data and propose a valve opening recognition algorithm and a valve closing recognition algorithm for the sampling data of the laser displacement sensor. [[ID=2�]]

[0029] Among them, the valve opening recognition algorithm includes: when the valve is in the closed state, compare the valve position l n at the detection moment with the valve position threshold l0.

[0030] If l n > l0, add 1 to the valve opening moment identification count C start , and judge the size of the opening moment identification count C start and the valve setting count threshold k.

[0031] If C start > k, it is considered that the valve meets the opening judgment condition, the valve opens, the valve opening identifier flag = 1, and initialize C start ; otherwise, if l n < l0, it is considered that the valve is closed, and initialize C start .

[0032] The valve closing recognition algorithm includes: when the valve is in the open state, compare the valve position l n at the detection moment with the valve position l n―1 at the previous moment. If ln ≥l n―1 And l n―1 ≥l c , (l c If l0 and l0 are the threshold values ​​for valve closing and opening respectively (the two values ​​are not the same), then the valve is closed, and the valve opening indicator flag is set to 0.

[0033] Step 4: Verify the feasibility of the valve opening recognition algorithm and the valve closing recognition algorithm. In Matlab, calibrate the opening and closing times of the valve data collected in each state. Then, write the valve opening recognition algorithm and the valve closing recognition algorithm used in the Matlab offline test into the ECU for multi-cycle open-loop testing.

[0034] Step 5: Design a closed-loop control system for valve opening duration that uses the valve opening duration identification as the closed-loop feedback input, and verify the closed-loop switching effect of the controller controlling the valve to track the target and achieve variable duration on an electro-hydraulic variable valve test platform; When the valve is running in multiple cycles, the displacement sensor detects the valve lift profile data in real time and transmits it to the ECU. The valve opening and closing time in the previous valve cycle is obtained by identifying the valve opening and closing time based on the detected valve lift using the valve opening and closing time identification method written in the ECU controller;

[0035] Step Six: Target Valve Opening Duration T during Valve Operation * Compared with the actual valve opening duration T of the previous cycle k The control variable of the closed-loop controller is used as the input to obtain the control output value of the high-frequency solenoid valve, which controls the duration of the high-level signal of the high-frequency solenoid valve, thereby controlling the valve opening duration of the next cycle to approach the target valve duration.

[0036] Step 7: Continuously variable valve opening duration: The difference between the target valve opening duration and the actual detected valve opening duration is used as the input of the closed-loop controller to control the opening and closing of the high-frequency solenoid valve to achieve the opening and closing of the valve.

[0037] Step 8: Evaluate the steady-state error of valve multi-cycle operation using the following formula:

[0038]

[0039] Where error is the error between the actual valve opening time and the target, t rdi Let t be the actual valve opening time in the i-th cycle. gd Let n be the target valve opening duration, and n be the total number of cycles.

[0040] In this embodiment, 100 cycles were performed by manipulating the valves on the test bench, and a portion of the results were analyzed. The closed-loop control and open-loop control effects were compared, and the average steady-state error was calculated. The results are shown in the table below:

[0041]

[0042]

[0043] This invention employs a laser displacement sensor and designs an algorithm to accurately identify the opening and closing times of an electro-hydraulic variable valve. The algorithm was validated on an actual experimental platform. The difference between the identified valve opening duration and the target valve opening duration is used as feedback input to control a high-frequency solenoid valve, thereby improving the consistency of the electro-hydraulic variable valve across multiple cycles. Since the electro-hydraulic variable valve eliminates the constraint of the camshaft, the valve opening and closing are controlled by a mechanism similar to an electro-hydraulic servo system, achieved by controlling the opening and closing of the high-frequency solenoid valve. Because the electro-hydraulic valve is subject to various time-varying factors, the timing of valve opening and the opening of the solenoid valve are closely related. There is a certain time delay characteristic. The difference between the target valve opening duration and the actual detected valve opening duration is used as the input of the closed-loop controller to control the opening and closing of the high-frequency solenoid valve, so as to achieve the tracking of the target valve opening duration by the actual valve opening duration. Due to the good robustness of the PID closed-loop control algorithm, it can effectively overcome the disturbances caused by the fluctuation characteristics of hydraulic oil temperature and pressure in the electro-hydraulic variable valve timing mechanism. Thus, it can achieve static error-free tracking of the target valve motion profile under the presence of external disturbances. In other words, compared with the less motion constraint of the electro-hydraulic valve under open-loop control, the fluctuation of the valve opening duration after being disturbed is larger. Under closed-loop control, this fluctuation can be effectively reduced. Specifically, it reduces the steady-state error of the system and improves the stability of the system in multi-cycle operation.

[0044] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A closed-loop control method for an electro-hydraulic variable valve with continuously variable opening duration, characterized in that, Includes the following steps: S1: Install the laser displacement sensor for detecting valve lift signal at the lift end of the electro-hydraulic variable valve. Under open-loop control, collect valve profile data of the electro-hydraulic valve in multiple cycles under various operating conditions. After processing the valve profile data, extract the single valve cycle under each operating condition as a valve profile feature analysis sample. S2: Design a closed-loop control system for valve opening duration that uses the valve opening duration as the closed-loop feedback input. The target valve opening duration during valve operation... Identifying the actual valve opening duration of the previous cycle The difference is the control variable of the closed-loop controller, and this is used as the input to obtain the control output value of the high-frequency solenoid valve to control the duration of the high-level signal of the high-frequency solenoid valve, thereby controlling the valve opening duration of the next cycle. S3: On the electro-hydraulic variable valve test platform, the controller controls the valve to track the target and achieves the closed-loop switching effect of variable duration. When the valve is running in multiple cycles, the displacement sensor detects the valve lift profile data in real time and transmits it to the ECU. The valve opening recognition algorithm and valve closing recognition algorithm written in the ECU controller identify the opening and closing time of the valve in the previous valve cycle based on the detected valve lift, and adjust the valve opening duration of the next cycle in real time through the closed-loop control algorithm. S4: Adjust the proportional unit and integral unit in the closed-loop controller control parameters to achieve the best stability of valve opening duration during multi-cycle operation under preset conditions; S5: The steady-state error of valve multi-cycle operation is evaluated using the following formula: in, This represents the error between the actual valve opening time and the target value. Let be the actual valve opening time in the i-th cycle. For the target valve opening duration, This represents the total number of cycles.

2. The closed-loop control method for continuously variable electro-hydraulic variable valve opening duration according to claim 1, characterized in that: The valve opening recognition algorithm includes: when the valve is closed, detecting the valve position at the current time. Valve position threshold To make a comparison, if Then the valve opening time marker will be counted. Increment by 1, and check the start time flag count. Valve set count threshold The size, if If the valve meets the opening condition, it is considered to be open, the valve is open, the valve opening identifier flag=1, and initialization is performed. Conversely, if It is assumed that the valve is closed and initialized. .

3. The closed-loop control method for continuously variable electro-hydraulic variable valve opening duration according to claim 2, characterized in that: The valve closing recognition algorithm includes: when the valve is open, if and This indicates that the valve is closed, and the valve opening determination flag is set to 0; where, To detect the valve position at the time of testing, This refers to the valve position at the previous moment. This is the threshold for determining when the valve is closed.

4. The closed-loop control method for continuously variable electro-hydraulic variable valve opening duration according to claim 1, characterized in that: In step S3, the verification method is to calibrate the opening and closing times of the collected valve data in Matlab, and write the valve opening recognition algorithm and valve closing recognition algorithm used in Matlab offline testing into the ECU for multi-cycle open-loop testing.

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