Signal feedforward and feedback control method based on pump valve proportional speed regulation performance

Abstract

The invention discloses a signal feedforward and feedback control method based on proportional speed regulation performance of a pump valve, which comprises the following steps of: a precise valve control method: a valve core displacement is caused by a control current value generated after an original handle is operated, a feedback numerical value is detected through a valve core displacement sensor arranged on a valve, and the control current value is corrected; according to the precise pump control adjusting method, the output value of the control current is obtained according to the current rotating speed, pump drainage is obtained, and according to a pressure difference delta P signal of the multi-way valve, the control current value capable of controlling the electric control pump is fed back for correction. The problems of unstable operation control, time delay or shaking and the like caused by poor performance consistency of a hydraulic electric control pump and an electric control multi-way valve can be solved, the problem of large parameter adjustment difficulty of an electro-hydraulic control system under the heavy-load composite action working condition can be solved, and the controllability level of a product loading operation system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electric power control systems, and in particular to a signal feedforward and feedback control method based on the proportional speed regulation performance of a pump valve. Background Art

[0002] Engineering machinery products play a vital role in my country's engineering construction. Due to the characteristics of large torque, strong power, high power-to-weight ratio, etc. of their working devices, most engineering machinery products use hydraulic transmission technology. Take a certain wheeled crane product as an example. During the hoisting operation, the system hydraulic energy is transmitted to the upper vehicle through the engine gearbox and hydraulic pump unit, and then transmitted to the hydraulic cylinder and hydraulic motor through the multi-way valve control, and the latter drives the actuator to move.

[0003] In the hydraulic system for on-board operations, the boom, telescopic and winch systems are usually controlled by 1 or 2 electric proportional variable pumps + 1 electro-hydraulic proportional multi-way valve. According to the system load pressure detection, the existing open-loop control strategy can also meet the speed controllable operation under single-action light load or heavy load conditions; but in the case of 2 or more compound operations, due to the difference in the load of the actuators and the inaccurate control of the spool position of the multi-way valve, the multi-action compound operation cannot be completed, and some will even shake or stop, seriously affecting the user's operating experience.

[0004] In the prior art, the patent number is: CN202310302969.3, and the patent name is: A construction machinery pump-controlled hydraulic system, including: an oil tank; a variable pump assembly; a relief valve; at least two sets of hydraulic actuators, including: a hydraulic actuator; a proportional reversing valve; a one-way valve, the oil inlet of the one-way valve is connected to the third oil port, the third oil port and the second oil port of the proportional reversing valve at the first valve position, the third valve position and the second valve position of the proportional reversing valve, respectively; a first pressure sensor, detecting the oil inlet of the one-way valve; a first valve, whose oil inlet and oil outlet are respectively connected to the variable pump assembly and the oil tank, the first valve includes a first elastic control end and a first hydraulic control port that make its valve body tend to close, the first hydraulic control port is connected to the oil outlet of the one-way valve, the first valve also includes a second hydraulic control port that provides a hydraulic oil pressure that makes its valve body tend to move in the direction of opening the connecting passage between its oil inlet and oil outlet, and the second hydraulic control port of the first valve is connected to the oil inlet of the first valve. This electro-hydraulic control system identifies different operating conditions through pressure detection at the main valve oil inlet P port and the actuator load port. Under light-load and high-speed conditions, pump-controlled volume speed regulation is used to achieve high efficiency and energy saving. Under heavy-load and low-speed conditions, valve port throttling speed regulation is used, sacrificing a certain amount of energy consumption in exchange for system robustness and avoiding jitter.

[0005] The above patent provides a system architecture of an electronically controlled pump + an electronically controlled valve, as well as a pump control + valve control compound adjustment method for single action, but it cannot solve the problem of proportional flow distribution under compound action conditions.

[0006] Here are the reasons:

[0007] 1. The relationship between the control current, valve core displacement and output flow of the multi-way valve is nonlinear. Due to the differences in the machining, manufacturing and assembly of the valve core and valve body, the multi-way valves produced in the same batch have poor performance consistency. Therefore, the same product will have a large difference in performance when the same control parameters are input.

[0008] 2. The total efficiency of the electronically controlled pump varies with the displacement and outlet pressure. Under a fixed input speed, the relationship between the control current, pump displacement and output flow of the electronically controlled pump is also nonlinear. In addition, the friction damping characteristics of the pump variable mechanical device cause the output flow corresponding to the lift of the pump control current and the return stroke to have a hysteresis loop. If the system wants to provide accurate flow, it is more difficult to control. Summary of the invention

[0009] In view of this, in order to solve the problem that the hydraulic system for vehicle operation in the prior art cannot solve the problem of proportional flow distribution under compound action conditions, the present invention proposes a signal feedforward and feedback control method based on the proportional speed regulation performance of a pump valve.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] A signal feedforward and feedback control method based on the proportional speed regulation performance of a pump valve comprises the following steps:

[0012] Step 1, precise valve control method: the control current value generated after the original handle operation causes the valve core to move, and the valve core displacement sensor set on the valve detects the feedback value to correct the control current value;

[0013] Step 2, precise pump control adjustment method: According to the handle operation, throttle operation and the corresponding working mode selection, the required flow is obtained, so as to obtain the output value of the control current and further obtain the theoretical pump discharge, and then according to the pressure difference ΔP signal of the multi-way valve, the control current value of the electronically controlled pump can be fed back for correction.

[0014] As a further improvement of the above technical solution:

[0015] Preferably, the specific steps in Step 1 are as follows:

[0016] Step 11. Calculate the required flow rate Qd under the current working conditions by operating the handle;

[0017] Step 12, calculate the MAX value of the required flow rate Qd according to the required flow rate Qd of the system, the maximum flow rate calculated by the system under throttle operation, and the operation mode selection;

[0018] Step 13, query the valve core displacement corresponding to the MAX value of the required flow rate Q according to the valve fitting curve array, and then output the control current value corresponding to the electric proportional pressure reducing valve under the valve core displacement;

[0019] Step 14, when the controller outputs the control current to the multi-way valve, the valve core fluid force and friction force will affect the valve core displacement. Through the detection and feedback correction of the valve core displacement sensor, the positioning accuracy of the valve core position will be improved, and the flow area A will be accurately controlled. Preferably, the valve fitting curve array includes a multi-way valve flow Q-valve core displacement x fitting curve and a multi-way valve valve core displacement x-control current I fitting curve.

[0020] Preferably, PID control is adopted in Step 13.

[0021] Preferably, the specific steps in Step 2 are as follows:

[0022] Step 21. Combined with the throttle operation or the handle operation, the system calculates the maximum flow value of the electronically controlled pump;

[0023] Step 22, according to the maximum flow value of the electronically controlled pump and the performance curve fitting array of the electronically controlled pump, the output value of the control current is directly obtained;

[0024] Step 23, according to the pressure difference ΔP signal between the P port and the Ls port of the multi-way valve, correct the control current of the pump to complete the load-sensitive and precise control of the pump oil supply flow.

[0025] Preferably, the performance curve fitting array of the electronically controlled pump includes a variable pump flow Q-speed n-pressure p curve and a variable pump displacement v-control current I fitting curve.

[0026] Preferably, PID control is adopted in Step 23.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention adds a valve core displacement sensor on the basis of the hydraulic system hardware of the existing electric control pump + electric proportional multi-way valve remains unchanged, and then combines the performance test data of the pump and valve components actually used in the product to provide a precise valve control method based on a feedforward control signal calibrated by a hydraulic multi-way valve proportional speed regulation performance test curve + a valve core displacement feedback signal, and a precise pump control adjustment method based on a feedforward control signal calibrated by an electric control pump proportional performance test curve + a multi-way valve pressure difference closed-loop feedback signal. The combination of the two can jointly improve the control speed regulation and process motion smoothness of the on-board operation system under single-action or multi-action conditions, solve the problems in the prior art, and improve the control performance under compound action conditions.

[0029] Therefore, the present invention can solve the problems of unstable operation control, delay or jitter caused by the poor performance consistency of the hydraulic electric-controlled pump and the electric-controlled multi-way valve, as well as the difficulty in adjusting the parameters of the electro-hydraulic control system under heavy-load compound action conditions, thereby improving the controllability of the product's on-vehicle operation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the pump control + valve control composite speed regulation logic control diagram of the present invention;

[0031] Figure 2 It is a schematic diagram of the flow rate-valve core displacement characteristic curve under a constant pressure difference of the present invention;

[0032] Figure 3 It is a schematic diagram of the valve core displacement-control current characteristic curve of the present invention;

[0033] Figure 4 It is a schematic diagram of the flow-speed-pressure curve of the variable pump of the present invention;

[0034] Figure 5 It is a schematic diagram of the swash plate angle-control current curve of the electronically controlled pump of the present invention;

[0035] Figure 6 It is a schematic diagram for comparing flow-valve core displacement test curves of the main volume and auxiliary volume of the multi-way valve of the present invention;

[0036] Figure 7 It is the total efficiency-outlet pressure test curve of the electronically controlled pump of the present invention at different displacements. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0038] In the description of the present invention, unless otherwise specified, "plurality" means two or more than two; the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0039] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] This technical solution mainly includes the following two methods:

[0041] 1. A precise valve control method based on a feedforward control signal + valve core displacement feedback signal calibrated by a hydraulic multi-way valve proportional speed regulation performance test curve;

[0042] 2. A precise pump control adjustment method based on a feedforward control signal calibrated by a proportional performance test curve of an electronically controlled pump + a multi-way valve pressure difference closed-loop feedback signal;

[0043] The combination of the above two solutions can jointly improve the control speed regulation and process motion smoothness of the vehicle operation system under single or multi-action conditions.

[0044] As attached Figure 1 As shown, it is the control logic diagram of this technical solution.

[0045] Among them, handle operation, throttle operation, and operation mode selection are all inputs;

[0046] The multi-way valve control current output and the variable pump control current output are both outputs;

[0047] The required flow input Qd, MAX maximum value, calculation of the maximum available flow, and PID control are all calculated control signals;

[0048] The engine speed, the measured valve core displacement x value, the pressure at the P port of the multi-way valve, and the pressure at the Ls port of the multi-way valve are all detection signals;

[0049] The multi-way valve flow Q-valve core displacement x fitting curve, the multi-way valve valve core displacement x-control current I fitting curve, the variable pump flow Q-speed n-pressure p curve, and the variable pump displacement v-control current I fitting curve are all curve fitting arrays.

[0050] The detailed explanation of the figure is as follows:

[0051] 1. Choice of operation mode

[0052] Users have different operating habits and different requirements for the efficiency and stability of lifting operations. Therefore, many crane products are equipped with operation model selection items on the onboard operation display interface. By selecting different operation modes, the internal control strategy will calculate and match the handle input signal and the maximum operating speed of the system, so that the system supply can meet the needs.

[0053] Both handle operation and throttle operation are inputs given by the user. The larger the control angle (handle or throttle pedal), the faster the user requires the work speed, and the greater the required flow of the hydraulic system.

[0054] 2. A precise valve control method based on the feedforward control signal + valve core displacement feedback signal calibrated by the hydraulic multi-way valve proportional speed regulation performance test curve. The main point is that the handle feedforward signal controls the valve core, and then the valve core displacement sensor detection signal feedback is used for correction;

[0055] 1. Multi-way valve performance curve fitting array

[0056] According to the bench test of the multi-way valve performance: flow rate under constant pressure difference-valve core displacement characteristics (such as attached Figure 2 As shown in the figure), valve core displacement-control current characteristic curve (as ... Figure 3 As shown), etc., you can get its fitting array.

[0057] When the program is running, the handle input corresponds to the required flow rate Qd under the current working conditions. The required flow rate Qd = N*V, where N is the engine speed and V is the pump discharge.

[0058] Then, the valve core displacement corresponding to the MAX maximum value of Qd is queried according to the fitting curve array, and then the control current value corresponding to the electric proportional pressure reducing valve under the valve core displacement is output.

[0059] The solution to the maximum value of Qd mainly depends on the choice of operation mode, the required flow rate Qd, and the calculated flow rate of the throttle, for example:

[0060] The system has two modes (high speed and low speed). The product encounters two common operating scenarios: high-speed lifting and lowering of the hook with no load and steady lifting with heavy load. The former requires fast speed (recommended mode 1), while the latter requires slow and steady speed (recommended mode 2).

[0061] If low-speed mode 2 is selected in high-speed operation scenario 1, its demand flow and supply flow will be multiplied by a coefficient of less than 1, which will reduce the speed of the entire operation.

[0062] 2. Closed-loop feedback control of valve core displacement

[0063] When the controller outputs control current to the multi-way valve, the valve core will switch to output hydraulic oil into the actuator to drive the load to move. At this time, the oil flows through the multi-way valve, and a pressure difference will be generated before and after the reversing valve. The valve core hydraulic force and friction will affect the valve core displacement. The valve core displacement sensor detection and feedback correction will improve the positioning accuracy of the valve core position and achieve precise control of the flow area A.

[0064] From the pressure difference-flow formula of orifice flow, we know that flow rate Q = C*A*sqrt(ΔP / ρ),

[0065] Among them, C is flow coefficient; A is flow area; ρ is hydraulic oil density; when the pressure difference before and after the valve is constant, the flow rate Q is proportional to the flow area A, that is, the output flow can be accurately controlled by adjusting the valve opening.

[0066] 3. A precise pump control adjustment method based on the feedforward control signal calibrated by the proportional performance test curve of the electronically controlled pump + the closed-loop feedback signal of the multi-way valve pressure difference. The main point is that the handle + throttle + mode signal determines the operator's intention to calculate the required flow rate. It feedforward controls the pump current to a theoretical displacement value, and then detects the signal through the pressure sensor before and after the main valve (the difference is calculated to reach the pressure difference before and after the valve), and the feedback control current is corrected;

[0067] 1. Electronically controlled pump performance curve fitting array

[0068] The engine speed is obtained based on the throttle operation, and then the system calculates the maximum flow rate available at the engine speed. However, there is an ECO mode that does not require the accelerator pedal to be pressed. The engine speed is obtained by operating the handle only, and the required flow rate Qd is obtained. Therefore, the throttle operation is automatically controlled to rise and fall with the size of the handle operation.

[0069] Then, based on the maximum flow rate obtained above and the performance of the electric control pump on the bench test, such as the variable pump flow-speed-pressure curve (such as Figure 4 As shown in the figure, we can know the characteristics of the electronically controlled variable pump: the lower the speed and the higher the outlet pressure, the smaller the flow rate output by the pump at the maximum displacement) and the pump displacement-control current curve (as shown in the attached figure) Figure 5 As shown, 1 is the pump swash plate angle-control current fitting curve, 2 is the pump swash plate angle-control current test curve under light load condition, and 3 is the pump swash plate angle-control current test curve under heavy load condition). The required flow rate is calculated by combining the handle input, and the displacement value of the electronically controlled pump can be calculated from the current speed. Then, according to the performance curve fitting array of the electronically controlled pump, the output value of the control current is directly obtained, which is used as the feedforward signal for controlling the pump.

[0070] 2. Valve port pressure difference closed loop feedback control

[0071] According to the pressure difference ΔP signal between the P port and Ls port of the multi-way valve, the displacement change of the electronically controlled pump can be controlled. This is similar to the working principle of the hydraulic load-sensitive pump: when the control current of the multi-way valve increases and the valve port opens wide, the pressure difference ΔP decreases. At this time, the control current of the electronically controlled pump automatically increases, increasing the oil supply flow, which will increase the pressure difference before and after the valve; if the pressure difference ΔP increases to a value greater than the set value, the control current of the electronically controlled pump automatically decreases, reducing the oil supply flow.

[0072] The main control objects of this method are electric proportional variable pumps and electro-hydraulic proportional load-sensitive multi-way valves. It requires multi-way valve spool displacement sensors, multi-way valve oil inlet P port and load feedback Ls port pressure sensors. By detecting the handle control signal and the pump input speed signal, the required flow of the electro-hydraulic system is calculated. Then, based on the bench performance fitting array of the electric control pump and the multi-way valve, the feedforward control signals of the multi-way valve and the electric control pump are output. The spool displacement signal of the former is used as closed-loop feedback to control the output current of the multi-way valve; the latter uses the pressure difference as closed-loop feedback to control the output current of the electric control pump. The two work together to achieve smooth control performance under single action and compound action conditions.

[0073] Example

[0074] 1. Through bench testing of a multi-way valve for a wheeled crane product, the design requires that the main and auxiliary windings have the same performance, and the hoisting device and electro-hydraulic components are interchangeable. The main and auxiliary windings on the multi-way valve are designed and manufactured to have the same structural dimensions of the reversing valve core, but actual field testing found that under the same working conditions, the flow-displacement performance of the main and auxiliary windings is quite different. The test curve is shown in the attached figure. Figure 1 As shown,

[0075] From the attached Figure 6 It can be seen that 1 is the output flow-valve core displacement test curve of the main volume, and 2 is the output flow-valve core displacement test curve of the auxiliary volume. The dead zone or flow starting point of the valve core is different, with a difference of 0.3-0.5mm; the larger the valve core opening, the larger the flow hysteresis loop, and there is a flow difference of 70-80L / min at the 11mm position. Therefore, we adopt the new valve core displacement detection method, and feed back the displacement signal to the control system in real time, so that the valve core can be quickly corrected in the compound action condition and controlled at the required position.

[0076] 2. Through bench testing of an electric variable pump for a wheeled crane product, it was found that its volumetric efficiency under different input speeds, different output pressures, and different control displacements varies greatly.

[0077] Take a set of volumetric efficiency test curves under fixed speed 1000rpm, different outlet pressures and displacements, as shown in the attached figure. Figure 7As shown, 1 is the test curve at maximum displacement, 2 is the test curve at 50% displacement, 3 is the test curve at 70% displacement, and 4 is the test curve at 85% displacement. The total efficiency of the pump shows a trend of first increasing and then decreasing with the increase of outlet pressure, but there are still certain differences in its efficiency values ​​at different displacements.

[0078] In order to solve the problem of inaccurate flow calculation caused by volumetric efficiency error, we adopt a pressure difference closed-loop feedback control strategy. When the actual output flow of the pump is insufficient, the hydraulic system automatically fails to form the corresponding pressure difference value, thus avoiding volumetric efficiency errors under different loads and speeds.

[0079] The above are only preferred specific implementation modes of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A signal feedforward and feedback control method based on the proportional speed regulation performance of a pump valve, characterized in that: The following steps are involved: Step 1, precise valve control method: the control current value generated after the original handle operation causes the valve core to move, and the valve core displacement sensor set on the valve detects the feedback value to correct the control current value; Step 2, precise pump control adjustment method: According to the handle operation, throttle operation and the corresponding working mode selection, the required flow is obtained, so as to obtain the output value of the control current and further obtain the theoretical pump discharge, and then according to the pressure difference ΔP signal of the multi-way valve, the control current value of the electronically controlled pump can be fed back for correction.

2. The signal feedforward and feedback control method based on the proportional speed regulation performance of a pump valve according to claim 1 is characterized in that: The specific steps in Step 1 are as follows: Step 11. Calculate the required flow rate Qd under the current working conditions by operating the handle; Step 12, calculate the MAX value of the required flow rate Qd according to the required flow rate Qd of the system, the maximum flow rate calculated by the system under throttle operation, and the operation mode selection; Step 13, query the valve core displacement corresponding to the MAX value of the required flow rate Q according to the valve fitting curve array, and then output the control current value corresponding to the electric proportional pressure reducing valve under the valve core displacement; Step 14. When the controller outputs the control current to the multi-way valve, the valve core hydraulic force and friction will affect the valve core displacement. Through the valve core displacement sensor detection and feedback correction, the positioning accuracy of the valve core position will be improved, and the precise control of the flow area A will be achieved.

3. The signal feedforward and feedback control method based on the proportional speed regulation performance of a pump valve according to claim 2 is characterized in that: The valve fitting curve array includes a multi-way valve flow Q-valve core displacement x fitting curve and a multi-way valve valve core displacement x-control current I fitting curve.

4. The signal feedforward and feedback control method based on the proportional speed regulation performance of a pump valve according to claim 2, characterized in that: PID control is adopted in Step 13.

5. The signal feedforward and feedback control method based on the proportional speed regulation performance of a pump valve according to claim 1, characterized in that: The specific steps in Step 2 are as follows: Step 21. Combined with the throttle operation or the handle operation, the system calculates the maximum flow value of the electronically controlled pump; Step 22, according to the maximum flow value of the electronically controlled pump and the performance curve fitting array of the electronically controlled pump, the output value of the control current is directly obtained; Step 23, according to the pressure difference ΔP signal between the P port and the Ls port of the multi-way valve, correct the control current of the pump to complete the load-sensitive and precise control of the pump oil supply flow.

6. The signal feedforward and feedback control method based on the proportional speed regulation performance of a pump valve according to claim 5, characterized in that: The performance curve fitting array of the electronically controlled pump includes a variable pump flow Q-speed n-pressure p curve and a variable pump displacement v-control current I fitting curve.

7. The signal feedforward and feedback control method based on the proportional speed regulation performance of a pump valve according to claim 5, characterized in that: PID control is adopted in Step 23.

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