Control system and method of electronic oil pump

Abstract

The invention discloses a control system and method for an electronic oil pump, and relates to the technical field of electronic oil pump control. The system comprises a database, a positioning module, a damping regulation and control module, a double-tube coordination module and an oscillation monitoring module, through the synergistic effect, cross unstable intervals are recognized and avoided, damping and flow path switching are dynamically adjusted, and real-time monitoring and graded early warning are conducted, so that when the electronic oil pump is in the low-flow working condition or the engine pre-lubrication boundary state, the flow path switching is dynamically adjusted; the problems of pressure oscillation, discontinuous oil film thickness, unsmooth hydraulic execution and the like caused by impedance matching imbalance between a pump characteristic curve and a pipeline can be effectively avoided; therefore, the technical problem that in the prior art, an electronic oil pump is prone to oscillation under the boundary working condition is thoroughly solved, and the stability and reliability of the system are greatly improved.

Description

Technical Field

[0001] This invention relates to the field of electronic oil pump control technology, and more specifically, to a control system and method for an electronic oil pump. Background Technology

[0002] An electronic oil pump is an oil pump directly driven by an electric motor and regulated by an electronic control unit (ECU). It breaks through the traditional method of mechanical transmission by the engine crankshaft or camshaft. It can deliver lubricating oil or hydraulic oil under different engine operating conditions, and even after the engine is turned off, to meet the lubrication needs after pre-lubrication or cold start. However, under low flow conditions or boundary conditions (such as the pre-lubrication stage before the engine starts), the characteristic curve (flow-pressure relationship) of the electronic oil pump and the impedance characteristic curve of the entire oil circuit system often cross into an unstable range. That is, the output characteristics of the electronic oil pump are mismatched with the impedance of the pipeline system, which leads to pressure oscillation, discontinuity in the thickness of the lubricating oil film, or uneven operation of hydraulic actuators. Summary of the Invention

[0003] The main objective of this invention is to provide a control system and method for an electronic oil pump to overcome the problems mentioned in the background art.

[0004] To achieve the above objectives, according to one aspect of the present invention, a control system for an electronic oil pump is provided, the system comprising: a database, a positioning module, a damping control module, a dual-pipe coordination module, and an oscillation monitoring module; The database stores the pump characteristic curves of the oil pump: ,in The speed coefficient describes the flow contribution per unit speed. The linear pressure coefficient indicates that the flow rate decreases linearly with increasing pressure. The coefficient of the nonlinear quadratic term reflects the nonlinear loss of fluid under high pressure or low speed, which is usually caused by oil viscosity or leakage in gaps. At the same time, the pressure P(t) and flow rate Q(t) of the oil pump are monitored and collected in real time and stored. The positioning module is based on the pump characteristic curve and the system impedance curve derived by combining the Darcy-Weisbach formula and the energy storage cavity effect: ,in The system absorbs flow, representing the flow rate consumed by the system under pressure P. For the oil tank pressure, The constant laminar flow impedance represents the constant flow resistance within the pipe caused by viscous resistance. For pressure-related turbulent impedance, , reflecting the nonlinear resistance characteristics of turbulence at high pressure, α is a turbulence resistance coefficient related to the pipeline structure and fluid characteristics; C is the compression coefficient of the cavity, representing the pressure fluctuation accommodating capacity of the system pipeline (similar to a capacitor), is the pressure change rate, indicating the rate of change of pressure with time, corresponding to the transient response; draw the curves of the two in the same pressure-flow coordinate system and numerically solve the intersection point, and locate the cross instability interval according to the intersection point, and when the pump operating point enters this interval, send the damping adjustment instruction to the damping control module, and send the valve adjustment instruction to the double-pipe coordination module at the same time; When the damping control module receives the damping adjustment instruction, it sends adjustment instructions to the damping hole and adjustable throttle valve connected in parallel in the main pipeline, and adjusts the valve opening through proportional or PI algorithm to suppress the oscillation in the cross instability interval; When the double-pipe coordination module receives the valve control instruction, it uses the three-way proportional valve to smoothly and shock-free switch the flow distribution from the buffer pipeline to the regular pipeline within the given switching time window according to the designed cosine buffer function, and combines the feedforward compensation term and the damping coupling term, and then adds PID feedback regulation to achieve precise tracking of the oil pressure trajectory and oscillation suppression; The oscillation monitoring module opens the observation window after maintaining for a set period of time after each adjustment, continuously samples the difference between the actual pressure and the expected pressure, draws a real-time error curve and compares it with the threshold value, calculates the overrun error integral, i.e. the oscillation value, and executes the corresponding strategy according to the oscillation value.

[0005] Further, the cross instability interval is located according to the intersection point: The function is And the inverse function is Draw them in the same pressure-flow coordinate system, and solve the equation in the function space , find all real solutions, and each real solution corresponds to an intersection point. Calculate the local slope of each intersection point on the two curves at the intersection point, and subtract the two to get the net slope. In the pressure-flow plane, start from the first intersection point with a net slope less than zero, and go along the pump characteristic curve to the next intersection point, until the first intersection point with a net slope greater than or equal to zero is encountered. These two intersection points are the cross instability interval. Between the two points, the net slope is less than zero, i.e. divergent and oscillatory instability. Thus the cross instability interval of the oil pump can be identified.

[0006] Further, adjust the valve opening: After identifying that it has entered the cross instability interval, activate the damping hole and adjustable throttle valve connected in parallel in the main pipeline, obtain the damping hole diameter d0, the corresponding damping coefficient c0, and the electric control opening X(t) ∈ [0, 1] of the adjustable throttle valve, and calculate the dynamic damping coefficient of the damping hole and the adjustable throttle valve in parallel : ; The pump-pipeline system is approximated as a first or second order inertia-spring-damper system, whose equivalent damping ratio is calculated as , where m is the equivalent mass, representing the inertia parameter of the oil column and related structures to the dynamic response, k is the equivalent stiffness, representing the elastic characteristics of the pipeline and oil tank, etc., the restoring force parameter to the pressure-volume change; a minimum damping ratio threshold is set, if the equivalent damping ratio is less than the minimum damping ratio threshold , it indicates the tendency to oscillate; The proportional control or PI control is adopted to adjust the valve opening, first calculate the damping ratio error , the calculation formula is , which represents the difference between the current equivalent damping ratio and the designed minimum damping ratio, the update formula of the throttle valve opening at the next moment is: , where is the current damping valve opening, K1 is the proportional gain, the response strength to the instantaneous damping ratio error , increasing can accelerate the error elimination speed, K2 is the integral gain, the response strength to the error accumulation, mainly used to eliminate the steady-state error; is the error integral, the cumulative amount of error in the past entire time window, used to compensate the steady-state deviation of the system; the control throttle valve opening is adjusted in real time with the change of the damping ratio error , so as to keep the equivalent damping ratio of the system close to or slightly higher than the designed value minimum damping ratio threshold , to suppress the oscillation in the cross-instability region.

[0007] Further, the double-path smooth switching and feed-backward compound control: There are two parallel pipelines at the pump outlet: the left side is the buffer pipeline, and the right side is the conventional pipeline, the three-way proportional valve mixes the flow of the two paths according to the electric control signal β(t)∈[0,1], and the switching process is designed as a cosine buffer function: , t is the current system running time, t∈[ , +T]; where is the switching starting time, i.e., the starting time of the buffer function switching, T is the switching duration, i.e., the buffer transition time of the entire switching process; set the normalized time variable τ: ∈[0,1], and substitute it into the buffer function, the buffer function is: , the first derivative of the buffer function is calculated as: , and the second derivative is For a first order function, the end point velocity is zero, smooth and no impact; for a second order derivative, the end point acceleration is zero, avoiding transient oscillation; the function design and derivation process reasonably utilizes the advantages of cosine function, which are end point smoothness, transition moderation, and controllable time width.

[0008] Further, the over-limit error integral is calculated: The error of each time point in the observation window is plotted in two-dimensional coordinates, and then the discrete points are connected in time sequence to obtain the real-time error curve U(t) of the observation window by using a smooth curve; an error threshold Emax is set, a straight line is drawn in the two-dimensional coordinates, the vertical coordinate = Emax, and the integral formula The error degree is calculated to obtain the oscillation value UE, wherein when U(t)≤Emax, =0, when U(t)>Emax, =U(t)-Emax.

[0009] Further, corresponding strategies are executed according to the oscillation value: An oscillation interval is set, if the oscillation value is within the oscillation interval, the current switching duration T is retrieved and increased by ΔT to obtain the latest switching duration, which is updated to the double-pipe coordination module; if the oscillation value is greater than the upper limit of the oscillation interval, the conservative mode is triggered; the specific conservative mode is that: Locking at an intermediate value, keeping the buffer pipeline and the conventional pipeline each providing 50% of the flow, avoiding greater disturbance caused by frequent switching, stopping using the feedforward compensation, simplifying the system to pure feedback control to avoid larger oscillation caused by model deviation or prediction error, and reducing the PID gain to a conservative gear, the conservative mode is automatically linked to the bypass safety valve or mechanical overflow valve, and part of the oil is directly returned to the oil tank under the control in the conservative mode, so that the high pressure coupling is quickly released, and the pipeline and the element are protected.

[0010] In order to achieve the above-mentioned purpose, according to another aspect of the present application, a control method of an electronic oil pump is provided, the method comprising the following steps: Step one, storing the pump characteristic curve of the oil pump, and simultaneously monitoring and collecting the pressure and flow of the oil pump and storing; based on the pump characteristic curve and the system impedance curve derived by combining the Darcy-Weisbach formula and the accumulator cavity effect, the curves of the two are drawn in the same pressure-flow coordinate system and the intersection point is numerically solved, and the intersection unstable interval is located according to the intersection point, and when the pump operating point enters the interval, a damping adjustment instruction is sent to step three, and a valve adjustment instruction is sent to step four; Step two, when receiving the damping adjustment instruction, sending an adjustment instruction to the damping hole and the adjustable throttle valve connected in parallel in the main road, and adjusting the valve opening degree by proportional or PI algorithm to suppress the oscillation in the intersection unstable interval; Step three, when receiving the valve control instruction, the three-way proportional valve is used to switch the flow distribution from the buffer pipeline to the conventional pipeline smoothly and without impact within a given switching time window according to a designed cosine buffer function, and the oil pressure trajectory is accurately tracked and oscillation is suppressed by combining a feedforward compensation term with a damping coupling term and then assisted by PID feedback regulation; Step four, after each adjustment is completed, an observation window is opened after a set time period, the difference between the actual pressure and the expected pressure is continuously sampled, a real-time error curve is drawn and compared with a threshold value, an overrun error integral, i.e., an oscillation value, is calculated, and a corresponding strategy is executed according to the oscillation value.

[0011] The beneficial effects of the present application are: The present application can accurately identify all intersection points of the pump characteristic curve and the pipeline impedance curve and quantitatively evaluate the net slope change trend at each intersection point by using the pre-stored pump characteristic curve, combining the Darcy-Weisbach formula and the energy storage cavity effect, and establishing a system impedance model, and when the slope of the pump and the system impedance is less than zero, it can be determined that it is in the unstable interval, and this amplification effect will amplify the small disturbance into obvious oscillation, and according to the accurate positioning of the start and end pressure values of the unstable interval in the pressure-flow plane, the flow and pressure boundaries for subsequent damping adjustment and flow path switching can be provided, avoiding blind control due to mismatch in low flow or boundary conditions, and effectively reducing the risk of pressure oscillation and insufficient lubrication caused by the unstable interval from the source; When the pump operating point enters the unstable interval, the present application uses a small-diameter damping hole and an adjustable throttle valve in parallel, dynamically calculates the damping coefficient according to the real-time pressure and valve opening, and simplifies the pump-pipeline model into an inertia-spring-damper system to estimate the equivalent damping ratio in real time, and when the equivalent damping ratio is lower than the set minimum threshold, the valve opening is quickly adjusted through a proportional or PI control algorithm to realize accurate tracking of the damping ratio, which not only quickly suppresses the oscillation in the cross-unstable interval, but also automatically eliminates the steady-state error, so that the system always remains in a critical stable or slightly higher damping state, thereby ensuring that the oil pressure fluctuation is timely attenuated under various working conditions, effectively improving the anti-oscillation ability and safety robustness of the electronic oil pump under variable working conditions; The application realizes the non-impact transition from the low impedance buffer passage to the high impedance conventional passage by connecting the buffer pipeline and the conventional pipeline in parallel at the outlet when the pump enters the easily oscillating area, and by switching the flow path according to the cosine buffer function with a three-way proportional valve, the smooth function with the first and second derivatives being zero at the endpoints can avoid the sudden change of speed and acceleration in the switching process, and suppresses the transient oscillation; at the same time, combined with the dynamic adjustment of the feedforward compensation and the damping coupling term, and supplemented by the PID feedback control, the system internal resistance and inertia disturbance can be pre-compensated and closed-loop corrected while ensuring smooth switching, so that both the oil film discontinuity caused by the sudden change of pressure and the energy efficiency and response speed of the system are maintained to the maximum during the whole switching process. The application calculates the overrun error integral to quantify the oscillation degree by monitoring the error curve of the oil pressure and the expected pressure in real time after each adjustment, and automatically adjusts the switching duration or triggers the conservative mode according to the preset oscillation interval; in the medium oscillation interval, the switching duration is moderately prolonged to further smooth the transition; when the oscillation value exceeds the upper limit, the conservative mode of mixed flow locking and pure feedback control is automatically switched to, the PID gain is reduced, and the safety valve or mechanical overflow valve is connected to reduce the large disturbance; the hierarchical response strategy can flexibly cope with slight disturbance and quickly protect the pipeline and components in severe oscillation, greatly improving the online adaptive stability and safety of the system. In summary, through the synergistic effect, the application identifies and avoids the cross-unstable interval, dynamically adjusts the damping and flow path switching, and monitors and grades the warning in real time, so that the electronic oil pump can effectively avoid the problems of pressure oscillation and oil film thickness discontinuity, hydraulic execution unevenness and the like caused by the imbalance between the pump characteristic curve and the pipeline impedance matching in the low flow condition or the engine pre-lubrication boundary state. Therefore, the application completely solves the technical problem that the electronic oil pump is prone to oscillation in the boundary condition in the prior art, and greatly improves the stability and reliability of the system. BRIEF DESCRIPTION OF DRAWINGS

[0012] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments of the present application and its description are used to explain the application and are not intended to limit the application. In the drawings: Figure 1 is a schematic diagram of the system module connection of the application; Figure 2 is a schematic diagram of the method flow of the application. DETAILED DESCRIPTION

[0013] It should be noted that the embodiments in the application and the features in the embodiments can be combined with each other without conflict. The application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0014] In order to make the person skilled in the art better understand the technical scheme of the present application, the technical scheme in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor should belong to the protection scope of the present application.

[0015] It should be noted that the terms "first", "second", and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to only those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0016] In order to make the purpose and advantages of the present application more clear and apparent, the present application will be further described below in conjunction with the embodiments; it should be understood that the specific embodiments described herein are only used to explain the present application, and do not limit the present application.

[0017] According to the embodiments of the present application, as shown in Figure 1 A control system of an electronic oil pump is provided, which comprises a database, a positioning module, a damping control module, a double-pipe coordination module and a shock monitoring module. The database stores the pump characteristic curve of the oil pump, and simultaneously monitors and collects the pressure P and flow Q of the oil pump, and stores them. The positioning module draws the pump characteristic curve and the system impedance curve (including constant laminar impedance, pressure-dependent turbulent impedance and cavity compression effect) derived based on the pump characteristic curve and combined with the Darcy-Weisbach formula and the energy storage cavity effect in the same pressure-flow coordinate system, and numerically solves the intersection point, calculates the sum of the local slopes at each real solution, judges the region where the slope sum is less than zero as the intersection unstable region, and from the first intersection point where the slope sum is less than zero, along the pump characteristic curve to the next intersection point where the slope sum is greater than or equal to zero, the interval is determined as the unstable interval, and when the pump operating point enters this interval, sends a damping adjustment instruction to the damping control module, and simultaneously sends a valve adjustment instruction to the double-pipe coordination module; When the damping adjustment module receives the damping adjustment instruction, the controller sends an adjustment instruction to the small-diameter damping hole and the adjustable throttle valve connected in parallel to the main pipeline. At this time, according to the dynamic damping coefficient determined by the real-time pressure and the opening degree of the electric control valve, and the pre-set minimum damping ratio threshold, the system equivalent the pump-pipeline system to an inertia-spring-damping model, calculates the difference between the current equivalent damping ratio and the threshold in real time, and adjusts the valve opening degree through a proportional or PI algorithm. The proportional gain and integral gain ensure that the damping ratio error is quickly eliminated and the steady-state deviation is eliminated, so as to maintain the equivalent damping ratio at a level slightly higher than the designed minimum value, thereby suppressing the oscillation in the cross-instability interval. When the double-pipe coordination module receives the valve control instruction, the three-way proportional valve is used to smoothly and shock-free convert the flow distribution from the buffer pipeline to the conventional pipeline within a given switching time window according to the designed cosine buffer function. The first and second derivatives of the buffer function are zero at the endpoints, effectively avoiding sudden changes in transient speed or acceleration. At the same time, combined with the feedforward compensation term (dynamic compensation for system resistance and inertia) and the damping coupling term, and supplemented by PID feedback regulation, precise tracking and oscillation suppression of the oil pressure trajectory are achieved. After each adjustment, the oscillation monitoring module opens an observation window after a set period of time, continuously samples the difference between the actual pressure and the expected pressure, draws a real-time error curve and compares it with the threshold, and calculates the overrun error integral (i.e. the oscillation value). If the oscillation value is below the lower limit of the oscillation interval, no further operation is required. If it is within the oscillation interval, the switching duration is appropriately extended and the feedforward and feedback parameters are recalculated. If it exceeds the upper limit of the oscillation interval, the conservative mode is started: the double-path flow is fixed at 50% each, the mixing weight is locked, the feedforward compensation is disabled, and only the conservative feedback PID control (proportional and integral gain halved, derivative gain maintained) is used to reduce the system response speed, and the bypass safety valve or mechanical overflow valve is connected in parallel to return part of the oil to the tank to ensure the safety of the pipeline and components and maximize the robustness of the system.

[0018] According to the embodiment of the present application, as shown in Figure 2 The control method of the electronic oil pump comprises the following steps: Step one, stability analysis, locate the cross-instability interval (i.e. the region where the slopes after the intersection of the characteristic curves are negative), and determine the flow and pressure range of the interval to provide a basis for subsequent control and damping design. Specifically: The pump characteristic curve of each oil pump is pre-stored. The specific process of obtaining the pump characteristic curve is as follows: fix the electronic oil pump speed at the target value w1 on the industrial oil pump test bench, connect the throttle valve control loop impedance, and install high-precision pressure sensors and flow meters. Adjust the throttle valve opening degree step by step to achieve different pipeline impedances. At each level, after the system pressure stabilizes, record the pump outlet pressure P and the corresponding flow The pump characteristic curve was fitted using the least squares method to obtain the continuous function. ,in The speed coefficient describes the flow contribution per unit speed. The linear pressure coefficient indicates that the flow rate decreases linearly with increasing pressure. The coefficient of the nonlinear quadratic term reflects the nonlinear loss of fluid under high pressure or low speed, which is usually caused by oil viscosity or leakage in gaps. Combining the Darcy-Weisbach formula and the energy storage cavity effect, the system consumption flow model is established as follows: ,in The system absorbs flow, representing the flow rate consumed by the system under pressure P. For the oil tank pressure, The constant laminar flow impedance represents the constant flow resistance within the pipe caused by viscous resistance. For pressure-related turbulent impedance, α reflects the nonlinear drag-in characteristics of turbulence under high pressure, and is a turbulence drag coefficient related to pipeline structure and fluid characteristics; C is the cavity compressibility coefficient, which characterizes the system pipeline's ability to accommodate pressure fluctuations (similar to a capacitor). The pressure change rate represents the rate at which pressure changes with time, corresponding to the transient response; Will and inverse function Plotting the two curves on the same pressure-flow axis visually shows their intersection and slope changes; solving the equations in function space. Solve for all real solutions, and each real solution corresponds to an intersection point. Mark all intersection points on the graph, where P* is the pressure value at the intersection point, which is the pump characteristic curve. With system impedance curve (Right now The pressure value corresponding to the point of intersection is the point where the flow rates of the two curves are equal; calculate the local slope of the two curves at the equilibrium point using the following formula: and , here It is a notation that refers to the flow rate required by a pipeline or the pipeline's response to flow rate; that is, the equivalent flow rate expression of a pipeline system. = According to the formula Calculate the net slope of the two curves. If the net slope <0 indicates that the system has an "amplification" effect on small disturbances. After deviating from this value, the system will diverge further, causing oscillations or instability. This crossover point and its neighborhood are called the unstable interval. In the PQ plane, from the first net slope The intersection point of <0 starts, along the pump characteristic curve to the next intersection point, until the first intersection point meets the net slope ≥0, these two intersection points are the intersection instability interval, between the two points, the net slope <0, that is, divergent, oscillatory instability; thus the intersection instability interval of the oil pump can be identified, if the intersection instability interval of the oil pump is identified, a damping adjustment instruction is sent to step two, and a valve adjustment instruction is sent to step three; By pre-stored pump characteristic curve, combined with Darcy-Weisbach formula and energy storage cavity effect to establish system impedance model, all intersection points of pump characteristic curve and pipeline impedance curve can be accurately identified in system design stage, and the trend of net slope change at each intersection point can be quantitatively evaluated; when the slope of pump and system impedance is less than zero, it can be determined as intersection instability interval, this amplification effect will cause small disturbance to be amplified as obvious oscillation; according to accurate positioning of the start and end pressure values of the instability interval in the pressure-flow plane, clear flow and pressure boundary can be provided for subsequent damping adjustment and flow path switching, avoiding blind control due to mismatch in low flow or boundary conditions, effectively reducing the risk of pressure oscillation and lubrication deficiency caused by instability interval from the source.

[0019] Step two, a small-diameter damping hole and an adjustable throttle valve are connected in parallel in the pipeline, when receiving the valve adjustment instruction, the equivalent damping ratio is adjusted in real time; specifically: The damping element should be installed between the pump outlet and the double-pipe branching point of the main trunk, the hole diameter of the damping hole is d0, the corresponding damping coefficient is c0, and they are connected in parallel in the same path, the valve core opening is represented by electric control amount X(t) ∈ [0, 1], the larger the opening, the larger the flow area, and the smaller the damping; its dynamic damping coefficient is , which is usually determined by pressure and opening; the calculation formula of the final equivalent damping coefficient ; the pump-pipeline system is approximated as a first-order or second-order inertia-spring-damping system, its equivalent damping ratio , the calculation formula is , wherein m is the equivalent mass, representing the inertia parameter of the oil column and related structure to dynamic response, k is the equivalent stiffness, representing the elastic characteristics of the pipeline and oil tank, etc., the restoring force parameter to pressure-volume change; a minimum damping ratio threshold is set, if the equivalent damping ratio < minimum damping ratio threshold , it means that it tends to oscillate; Proportional control or PI control is adopted to adjust the valve opening, first calculate the damping ratio error , the calculation formula is ​, which represents the difference between the current equivalent damping ratio and the design minimum damping ratio, the next time throttle opening The update formula is: , where is the current damping valve opening, K1 is the proportional gain, and the response strength of the instantaneous damping ratio error , increasing can speed up the error elimination speed, K2 is the integral gain, and the response strength of the error accumulation, mainly used to eliminate the steady-state error; is the error integral, the cumulative amount of error in the past entire time window, used to compensate for the steady-state deviation of the system; control the throttle opening, so that the throttle opening X(t) is adjusted in real time with the change of the damping ratio error , so as to keep the system equivalent damping ratio Close to or slightly higher than the design value of the minimum damping ratio threshold To suppress the oscillation in the cross-unstable region; By identifying when the pump operating point enters the unstable region, using a small-diameter damping hole and an adjustable throttle valve, dynamically calculating the damping coefficient according to the real-time pressure and valve opening, and simplifying the pump-pipeline model into an inertia-spring-damper system to estimate the equivalent damping ratio in real time; When the equivalent damping ratio is lower than the set minimum threshold, the valve opening is quickly adjusted through proportional or PI control algorithm to realize accurate tracking of the damping ratio; Not only can it quickly suppress the oscillation in the cross-unstable region, but also can automatically eliminate the steady-state error, so that the system always remains in a critical stable or slightly higher damping state, thereby ensuring that the oil pressure fluctuation is attenuated in time under various working conditions, effectively improving the anti-oscillation ability and safety robustness of the electronic oil pump under variable working conditions.

[0020] Step three, in the pre-lubrication stage, by setting a parallel double pipeline, combined with a three-way proportional valve mixed shunt, realize the smooth switching from the buffer pipeline to the conventional pipeline, suppress the oscillation, and keep the system energy efficiency; Specifically: There are double pipelines, the left pipeline is the buffer pipeline, and the right pipeline is the conventional pipeline. It needs to be explained here that the parameters of the pipeline in step one and the related calculations are all based on the conventional pipeline on the right; Buffer pipeline: low impedance, large pipe diameter, few elbows, and the characteristic curve is more gentle at low flow; Conventional pipeline: high impedance, standard pipe diameter, many elbows, and meets the flow-resistance design under daily working conditions; The three-way proportional valve is installed between the pump outlet and the two branches; When receiving the valve adjustment instruction, design and derive the smoothing function, t is the current time, that is, the current system running time, t∈[ , +T]; Where The switching start time, that is, the starting time of the buffer function, T is the switching duration, that is, the buffer transition time of the entire switching process, the larger T indicates the smoother the switching; The buffer function is: Let the normalized time variable be τ: ∈[0,1], and substituting this into the buffer function, the buffer function becomes: The first derivative of the buffer function is calculated as follows: and the second derivative is For a first-order function, the endpoint velocity is made zero, resulting in a smooth and shock-free process; for a second-order derivative, the endpoint acceleration is made zero to avoid transient oscillations. The design and derivation of this function make reasonable use of the advantages of the cosine function, namely, smooth endpoints, gentle transition, and controllable time width. Set the desired trajectory under system pressure. The approximate dynamic behavior of the oil circuit is represented by a second-order differential equation: P is the current oil pressure. This refers to hydraulic acceleration, which describes the steepness of the pressure change trend. is the rate of change of oil pressure (the speed of pressure), which describes the speed at which the pressure rises or falls; c is the equivalent damping, i.e., the resistance coefficient of the pipeline valve, which is similar to friction. The channel control gain is the effectiveness of the β control pressure (opening-pressure mapping coefficient). To control the input (obtained from the switching function above); based on the current desired trajectory The feedforward control variable is designed to compensate for the system's internal resistance and inertia. It can quickly compensate for upcoming dynamic disturbances and act in advance on the oil pump control system; For damping coupling terms, θ is the coupling gain, used to adjust the influence of the coupling term to ensure that the system is not over- or under-excited; feedforward control considers both the target trajectory and the current damping state, further improving the system's vibration suppression capability in the unstable region; Then, set the PID feedback adaptive adjustment to obtain the feedback controller output. : Where K3 is the differential gain, and the PID controller is based on the actual error. Closed-loop adjustments are performed to compensate for model biases and external disturbances in real time; it should be noted that the total control input... : and constraints ∈[0,1], adjust the flow rate proportionally between the two channels: ; By connecting the buffer pipeline and the conventional pipeline in parallel at the outlet when the pump enters the easily oscillating area, and by switching the flow path smoothly according to the cosine buffer function with a three-way proportional valve, the smooth transition from the low-impedance buffer passage to the high-impedance conventional passage is realized. The smooth function with the first and second derivatives being zero at the endpoints can avoid the sudden changes in speed and acceleration during the switching process and suppress transient oscillation. At the same time, in combination with feedforward compensation and dynamic adjustment of the damping coupling term, and supplemented by PID feedback control, the system internal resistance and inertia disturbance can be pre-compensated and closed-loop corrected while ensuring smooth switching, so that both the oil film discontinuity caused by sudden pressure change and the energy efficiency and response speed of the system are maintained to the maximum extent.

[0021] Step four, real-time online oscillation monitoring and early warning; After each adjustment through the above steps, the pressure is monitored in real time after a fixed time (1 min or 2 min, etc.), and the pressure is compared with the expected pressure The real-time error U(t) is obtained by difference calculation. With a fixed time period as an observation window (30 s or 1 min or 2 min, etc.), the errors at each time point in the observation window are plotted in two-dimensional coordinates, and then the discrete points are connected in time sequence to obtain the real-time error curve of the observation window by using a smooth curve. There is an error threshold Emax. If the real-time error U(t) is greater than the error threshold Emax, it indicates that the error is obvious, and a straight line is drawn in the two-dimensional coordinates, with the vertical coordinate = Emax. The error degree is calculated by using the integral formula When U(t)≤Emax, =0, when U(t)>Emax, =U(t)-Emax; There is an oscillation interval. If the oscillation value is less than the lower limit of the oscillation interval, it indicates that the system pressure error is very small and can be ignored, and no adjustment is needed. If the oscillation value is within the oscillation interval, the current switching duration T is retrieved and increased by ΔT to obtain the latest switching duration, which is updated to step three to re-estimate the feedforward component and the feedback component. If the oscillation value is greater than the upper limit of the oscillation interval, it indicates that the adjustment effect is not good and the error is serious, and the conservative mode is triggered. The specific conservative mode is to set the mixed weight Locking in a middle value (i.e. 0.5), keeping the buffer pipeline and the conventional pipeline each providing 50% of the flow, avoiding greater disturbance caused by frequent switching, stopping using feedforward compensation, simplifying the system to pure feedback control, to avoid model deviation or prediction error causing greater shock, and reducing the PID gain to a conservative gear (K1, K2 reduced by 50%, K3 remains), slowing down the response speed, sacrificing a little performance for higher robustness; It should be noted that the conservative mode automatically interlocks the safety valve or mechanical overflow valve, and in the conservative mode, the control will return part of the oil to the tank, quickly contact high pressure coupling, and protect the pipeline and elements; By monitoring the error curve of the oil pressure and the expected pressure in real time after each adjustment, the overrun error integral is calculated to quantify the shock level, and the switching duration is automatically adjusted or the conservative mode is triggered according to the preset shock interval; In the medium shock interval, the switching time is moderately extended to further smooth the transition; When the shock value exceeds the upper limit, the system automatically switches to the conservative mode of mixed flow locking and pure feedback control, reduces the PID gain, and triggers the safety valve or mechanical overflow valve to offset the large disturbance; This hierarchical response strategy can not only flexibly respond to slight disturbances, but also quickly protect the pipeline and elements in severe shock, greatly improving the online adaptive stability and safety of the system.

[0022] The above is only an embodiment of the present application and is not intended to limit the present application. Those skilled in the art can make various changes and modifications to the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the scope of the claims of the present application.

Claims

1. A control system of an electronic oil pump, comprising a database storing pump characteristic curves of the oil pump, while real-time monitoring and collecting pressure and flow rate of the oil pump and storing; characterized in that Further comprising: a positioning module, based on the pump characteristic curves and system impedance curves derived by combining Darcy-Weisbach formula and energy storage cavity effect, drawing curves of both in the same pressure-flow coordinate system and numerically solving intersection points, and positioning intersection unstable interval according to the intersection points, and sending damping adjustment instructions to the damping control module and valve adjustment instructions to the double-pipe coordination module when the pump operating point enters the interval; the damping control module sends adjustment instructions to the damping hole and adjustable throttle valve connected in parallel in the main line when receiving the damping adjustment instructions, and adjusts the valve opening through proportional or PI algorithm to suppress oscillation in the intersection unstable interval; the double-pipe coordination module receives the valve control instructions, uses a three-way proportional valve to switch the flow distribution from the buffer pipe to the regular pipe according to a designed cosine buffer function within a given switching time window, and combines a feedforward compensation term and a damping coupling term, and then uses PID feedback regulation to achieve precise tracking of the oil pressure trajectory and oscillation suppression; the oscillation monitoring module opens an observation window after maintaining a set time after each adjustment, continuously samples the difference between the actual pressure and the expected pressure, draws a real-time error curve and compares it with a threshold value, calculates the overrun error integral, i.e. the oscillation value, and executes corresponding strategies according to the oscillation value.

2. The control system of an electric oil pump according to claim 1, wherein Positioning the intersection unstable interval according to the intersection points: placing the pump characteristic curves and the system impedance curves in the same pressure-flow coordinate system, numerically solving the real solutions of the two curves, each real solution being an intersection point of the two curves, calculating the local slopes of the two curves at each intersection point, and subtracting the two slopes to obtain the net slope, in the pressure-flow plane, starting from the first intersection point with a net slope less than zero, along the pump characteristic curve to the next intersection point, until the first intersection point with a net slope greater than or equal to zero is encountered, the two intersection points being the intersection unstable interval, and between the two points, the net slope is less than zero, i.e. divergence and oscillation instability; thus the intersection unstable interval of the oil pump can be identified.

3. The control system of an electric oil pump according to claim 2, wherein Adjusting the valve opening: after identifying the entry into the intersection unstable interval, activating the damping hole and adjustable throttle valve connected in parallel in the main line, obtaining the damping hole diameter, corresponding damping coefficient and electric control opening of the throttle valve, and calculating the dynamic damping coefficient of the damping hole and adjustable throttle valve in parallel; approximating the pump-pipeline system as a first-order or second-order inertia-spring-damper model, calculating the equivalent damping ratio, presetting the minimum damping ratio threshold, subtracting the equivalent damping ratio from the minimum damping ratio threshold to obtain the damping ratio error, and updating the valve opening through proportional-integral control until the latest equivalent damping ratio is greater than or equal to the minimum damping ratio threshold.

4. The control system of an electric oil pump according to claim 3, wherein Double-path smooth switching and feedforward-feedback compound control: At the pump outlet, two parallel pipelines are provided: the left side is a buffer pipeline, and the right side is a conventional pipeline. A three-way proportional valve proportionally mixes the flow rates of the two routes according to an electric control signal β(t) ∈ [0, 1], and the switching process is designed by a cosine buffer function as follows: , t is the current system running time, t ∈ [ , +T]; wherein the switching starting time, that is, the starting time of the buffer function switching, and T is the switching duration, that is, the buffer transition time of the entire switching process. The function is zero at the endpoint first and second derivatives, the system is based on the current target pressure trajectory to build a second-order differential model, and a feedforward compensation term is designed to offset the system resistance and inertia disturbance in advance, while a damping coupling term is added to enhance the suppression of transient fluctuations, and the final control quantity is the sum of feedforward and PID feedback, which drives the three-way valve; wherein the damping coupling term is composed of damping ratio error.

5. The control system of an electric oil pump according to claim 4, wherein Calculate the overrun error integral: The errors of each time point in the observation window are plotted in two-dimensional coordinates in sequence, and then the smooth curve is used to connect the discrete points in sequence to obtain the real-time error curve U(t) of the observation window; the error threshold Emax is set, a straight line is drawn in the two-dimensional coordinates, the ordinate = Emax, and the integral formula is used The error degree is calculated to obtain the shock value UE, wherein, when U(t)≤Emax, =0, when U(t)>Emax, =U(t)-Emax.

6. The control system of an electric oil pump according to claim 5, wherein According to the oscillation value, execute the corresponding strategy: An oscillation range is set. If the oscillation value is within the oscillation range, the current switching duration T is retrieved and increased by an increment of ΔT to obtain the latest switching duration, which is then updated to the dual-tube coordination module. If the oscillation value exceeds the upper limit of the oscillation range, a conservative mode is triggered. The specific conservative mode is as follows: Lock the flow rate at an intermediate value, ensuring that the buffer line and the regular line each provide 50% of the flow to avoid greater disturbances caused by frequent switching. Stop using feedforward compensation and simplify the system to pure feedback control to avoid greater oscillations caused by model bias or prediction errors. Then reduce the PID gain to a conservative level. In conservative mode, automatically interlock the safety valve or mechanical relief valve. In conservative mode, control the direct return of some oil to the oil tank to quickly decouple the high pressure and protect the pipeline and components.

7. A control method of an electric oil pump ， characterized in that The control system is applied to the electronic oil pump of any one of claims 1-6, comprising: Step one, store the pump characteristic curve of the oil pump, and monitor and collect the pressure and flow of the oil pump in real time and store; based on the pump characteristic curve and the system impedance curve derived by combining the Darcy-Weisbach formula and the accumulator cavity effect, draw the curves of the two curves in the same pressure-flow coordinate system and numerically solve the intersection point, and according to the intersection point, locate the cross unstable interval, and when the pump operating point enters this interval, send the damping adjustment instruction to step two, and send the valve adjustment instruction to step three; Step two, when receiving the damping adjustment instruction, send adjustment instructions to the damping hole and adjustable throttle valve connected in parallel to the main line, and adjust the valve opening through proportional or PI algorithm to suppress the oscillation in the cross unstable interval; Step three, when receiving the valve control instruction, use the three-way proportional valve to follow the designed cosine buffer function to smoothly and impact-free convert the flow distribution from the buffer pipeline to the regular pipeline within the given switching time window, and combine the feedforward compensation term and the damping coupling term, and then assist with PID feedback adjustment to realize accurate tracking and oscillation suppression of the oil pressure trajectory; Step four, after each adjustment is completed, open the observation window after maintaining for a set period of time, continuously sample the difference between the actual pressure and the expected pressure, draw the real-time error curve and compare it with the threshold value, calculate the overrun error integral, that is, the oscillation value, and execute the corresponding strategy according to the oscillation value.

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