A Multi-Cylinder Flow Coupling and Decoupling Control Method

Abstract

This invention discloses a multi-cylinder flow coupling and decoupling control method, belonging to the field of intelligent control technology. It is used for high-precision trajectory tracking control in parallel drive conditions of multiple hydraulic cylinders such as boom, stick, and bucket. The method includes real-time acquisition of multi-actuator pressure data, construction of valve orifice flow equations, linearization of the valve orifice flow equations at the operating point, calculation of key parameters of each parallel branch, and construction of a multi-actuator pressure and flow coupling model. A cross-coupling gain matrix is ​​constructed to obtain the nominal valve core displacement command of each parallel branch. Based on the cross-coupling gain matrix, the comprehensive decoupling compensation amount of each parallel branch is calculated, the nominal valve core displacement command is compensated, and the compensated valve core displacement command is output to drive the movement of the hydraulic cylinder of the corresponding branch. This invention reduces the active joint trajectory tracking error by 3.9% and the passive joint motion error by 2.1%, effectively improving the end-effector trajectory tracking accuracy of the excavator.

Description

Technical Field

[0001] This invention relates to the field of intelligent control technology for engineering machinery, and more particularly to the field of trajectory tracking control technology for the end effector of a robotic arm. Specifically, it refers to a multi-cylinder flow coupling and decoupling control method, which is suitable for high-precision trajectory tracking control under the condition of parallel drive of multiple hydraulic cylinders. Background Technology

[0002] In multi-actuator parallel systems, the hydraulic cylinders are typically supplied with oil by a single main pump. In actual operation, the actuators are coupled through the oil supply lines, resulting in severe flow competition and pressure coupling, significantly impacting the trajectory tracking accuracy of the robotic arm's end effector. For example, in the robotic arm control of a hydraulic excavator, when the boom hydraulic cylinder moves significantly while the stick hydraulic cylinder moves slightly or remains stationary, increasing the boom valve opening increases the flow into that cylinder, raising the total flow in the oil supply line. This increases the friction loss and local resistance along the pipeline, causing a drop in the common oil supply pressure before the valve. With the stick valve opening unchanged, the valve pressure differential decreases, passively reducing the flow into the stick hydraulic cylinder, thus generating undesirable dragging motion. Conversely, when the load on the boom hydraulic cylinder increases (e.g., encountering hard soil resistance), its load pressure rises, the valve pressure differential decreases, and the flow into the boom decreases. This decrease in total flow leads to a lower pipeline pressure drop and an increase in the pressure before the valve, further increasing the valve pressure differential and passively increasing the flow in the stick hydraulic cylinder, similarly triggering dragging motion.

[0003] Existing decoupling control methods are mainly divided into two categories. One category is hardware decoupling schemes based on mechanical and hydraulic structures, such as load-sensitive (LS) systems and load-independent flow distribution (LUDV) systems. These schemes maintain a constant pressure difference between the valve ports through pressure compensation valves, which can suppress steady-state flow coupling to a certain extent. However, they cannot completely eliminate pressure fluctuation interference during dynamic processes and increase system complexity and cost. The other category is software decoupling schemes based on control algorithms, such as neural network decoupling and fuzzy decoupling. These schemes do not require hardware modifications, but they usually rely on a large amount of experimental data for offline training. The model's generalization ability is limited, and the computational complexity is high, making it difficult to run in real time on the vehicle controller.

[0004] Therefore, there is an urgent need for a decoupling control method that requires less computation, does not require additional hardware costs, and can run online in real time, in order to effectively suppress flow and pressure coupling in multi-actuator parallel systems and improve the trajectory tracking control accuracy of the robotic arm end effector. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-cylinder flow coupling and decoupling control method to solve the problems of existing decoupling control schemes that rely on offline training, are costly, computationally complex, and difficult to run in real time online.

[0006] To achieve the above objectives, the present invention provides a multi-cylinder flow coupling and decoupling control method, comprising: S1. Real-time acquisition of multi-actuator pressure data through sensors, including the valve pre-supply pressure of the multi-actuator parallel system, the large chamber pressure of each parallel branch, and the small chamber pressure of each parallel branch; S2. Under the quasi-static assumption, construct the valve orifice flow equation, calculate the valve orifice flow of each parallel branch based on the pressure data of multiple actuators, linearize the valve orifice flow equation at the operating point, calculate the key parameters of each parallel branch, and construct a multi-actuator pressure and flow coupling model. The key parameters include flow gain, oil supply pressure and flow coefficient, and load pressure and flow coefficient. S3. Based on the key parameters of each parallel branch, the coupling gain of valve port action between each parallel branch and the coupling gain of load change between each parallel branch are calculated through the multi-actuator pressure and flow coupling model, and a cross-coupling gain matrix is ​​constructed. S4. Obtain the nominal valve core displacement command of each parallel branch, calculate the comprehensive decoupling compensation amount of each parallel branch based on the valve port action coupling gain and load change coupling gain of each parallel branch, compensate the nominal valve core displacement command of the corresponding parallel branch through the comprehensive decoupling compensation amount of each parallel branch, and output the compensated valve core displacement command to drive the movement of the hydraulic cylinder of the corresponding branch.

[0007] In S2, the valve orifice flow equation is: ; ; In the formula, Indicates the flow rate at the valve orifice. Indicates the valve orifice flow coefficient. Indicates the valve orifice area gradient. Indicates valve core displacement. Indicates the density of hydraulic oil. Indicates the oil supply pressure before the valve. Indicates equivalent load pressure. Indicates external load force. Indicates the effective area of ​​the piston. Indicates the pressure in the large cavity. Indicates the pressure in the small cavity. Indicates the effective working area of ​​the large cavity. This indicates the effective working area of ​​the small cavity.

[0008] Calculate the valve orifice flow rate for each parallel branch based on the valve orifice flow equation: ; In the formula, Indicates branch index, Indicates the first The valve orifice flow rate of each parallel branch Indicates the first The valve orifice flow coefficient of each parallel branch Indicates the first The valve port area gradient of a parallel branch Indicates the first The valve core displacement of each parallel branch Indicates the first The equivalent load pressure of each parallel branch.

[0009] The valve orifice flow equation is linearized at the operating point, including in the first... At the steady-state operating point of each parallel branch, for Perform total differential and calculate the first... The flow increment of each parallel branch : ; In the formula, Indicates increment, To represent partial derivatives, Indicates only When changing rate of change, Indicates only When changing rate of change, Indicates only When changing rate of change, This indicates solving for the partial derivative at the steady-state operating point. Indicates the valve core displacement increment. This indicates an increase in oil supply pressure. This indicates the increase in load pressure.

[0010] Calculate the key parameters of each parallel branch based on the flow gain; No. The flow gain of each parallel branch is: ; No. The oil supply pressure and flow coefficient of each parallel branch are: ; No. The load pressure and flow coefficient of each parallel branch are: ; Based on the key parameters of each parallel branch, the linearized incremental equation is constructed: ; In the formula, Indicates the first The flow gain of each parallel branch Indicates the first The oil supply pressure and flow coefficient of each parallel branch, Indicates the first The load pressure and flow coefficient of each parallel branch.

[0011] Under the quasi-static assumptions, the oil supply pressure satisfies static force equilibrium, and the dynamic equation for the oil supply pressure is: ; ; In the formula, Indicates the rated oil supply pressure. This represents the sum of the flow rates at the valve ports of all parallel branches. Indicates the equivalent oil supply resistance. Indicates the total pressure drop in the pipeline. This is the flow index.

[0012] Under the quasi-static assumptions, based on the dynamic equation of the oil supply pressure, an incremental equation for the oil supply pressure is constructed: ; By combining the dynamic equation of oil supply pressure with the linearized incremental equation, a multi-actuator pressure-flow coupling model is constructed: ; In the formula, Indicates branch index, This indicates the total number of parallel branches.

[0013] In S3, the valve port action coupling gain is: ; In the formula, , indicating the index of the coupling interference branch, Indicates a branch For branch roads The valve port action coupling gain characterizes the branch. Valve movement affects branch The impact on traffic; The load change coupling gain is: ; In the formula, Indicates a branch For branch roads The load variation coupling gain characterizes the branch. Load changes affect branches The impact on traffic.

[0014] Calculate the overall decoupling compensation amount based on the valve port action coupling gain and load change coupling gain: ; ; In the formula, Indicates the first The comprehensive decoupling compensation amount for each parallel branch, Indicates the first The overall flow gain of each parallel branch.

[0015] Obtain the nominal valve core displacement command of each parallel branch, and compensate the nominal valve core displacement command of the corresponding parallel branch based on the comprehensive decoupling compensation amount of each parallel branch to obtain the compensated valve core displacement command: ; ; In the formula, Indicates the compensation after the first Valve core displacement command for each parallel branch Indicates the first The nominal valve core displacement command of each parallel branch This is the proportional control coefficient. For displacement error, The differential control coefficient, This represents the rate of change of error.

[0016] Compared with the prior art, the present invention has the following advantages: This invention constructs a multi-actuator pressure and flow coupling model and introduces a cross-coupling gain matrix. From a control principle perspective, it actively eliminates pressure and flow coupling interference between branches, achieving active decoupling compensation for flow competition between parallel hydraulic cylinders. This simultaneously suppresses the driving error of active joints (such as the boom) and the entanglement motion error of passive joints (such as the stick and bucket), improving the system's motion coordination and stability under complex working conditions. Simulation experiments demonstrate that, after adopting the multi-cylinder flow coupling decoupling control method provided by this invention, the trajectory tracking error of active joints is reduced by 3.9%, and the entanglement motion error of passive joints is reduced by 2.1%, effectively improving the overall positioning accuracy and trajectory smoothness of the excavator bucket end in complex trajectory operations. The decoupling control method of the present invention has a clear structure and a well-defined calculation process. It does not require additional hardware sensors and is easy to program and implement in the controllers of existing construction machinery (such as excavators and loaders). It is applicable to most multi-actuator parallel systems and has universality. Attached Figure Description

[0017] Figure 1The overall control flowchart of the multi-cylinder flow coupling and decoupling control method provided by the present invention is shown below. Figure 2 This is a schematic diagram of the equivalent model of the multi-actuator parallel oil supply system provided by the present invention; Figure 3 The displacement tracking comparison diagram of cylinder 1 (active cylinder) in the simulation of the two-cylinder parallel system provided by this invention; Figure 4 for Figure 3 Enlarged detail view of area A in the middle; Figure 5 The displacement tracking comparison diagram of cylinder 2 (passive cylinder) in the simulation of the two-cylinder parallel system provided by this invention; Figure 6 for Figure 5 A magnified view of the details in region B. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0019] A multi-cylinder flow coupling and decoupling control method includes: S1. Real-time acquisition of multi-actuator pressure data through sensors, including the valve pre-supply pressure of the multi-actuator parallel system, the large chamber pressure of each parallel branch, and the small chamber pressure of each parallel branch; S2. Under the quasi-static assumption, construct the valve orifice flow equation, calculate the valve orifice flow of each parallel branch based on the pressure data of multiple actuators, linearize the valve orifice flow equation at the operating point, calculate the key parameters of each parallel branch, and construct a multi-actuator pressure and flow coupling model. The key parameters include flow gain, oil supply pressure and flow coefficient, and load pressure and flow coefficient. S3. Based on the key parameters of each parallel branch, the coupling gain of valve port action between each parallel branch and the coupling gain of load change between each parallel branch are calculated through the multi-actuator pressure and flow coupling model, and a cross-coupling gain matrix is ​​constructed. S4. Obtain the nominal valve core displacement command of each parallel branch, calculate the comprehensive decoupling compensation amount of each parallel branch based on the valve port action coupling gain and load change coupling gain of each parallel branch, compensate the nominal valve core displacement command of the corresponding parallel branch through the comprehensive decoupling compensation amount of each parallel branch, and output the compensated valve core displacement command to drive the movement of the hydraulic cylinder of the corresponding branch.

[0020] In S2, the valve orifice flow equation is: ; ; In the formula, Indicates the flow rate at the valve orifice. Indicates the valve orifice flow coefficient. Indicates the valve orifice area gradient. Indicates valve core displacement. Indicates the density of hydraulic oil. Indicates the oil supply pressure before the valve. Indicates equivalent load pressure. Indicates external load force. Indicates the effective area of ​​the piston. Indicates the pressure in the large cavity. Indicates the pressure in the small cavity. Indicates the effective working area of ​​the large cavity. This indicates the effective working area of ​​the small cavity.

[0021] Calculate the valve orifice flow rate for each parallel branch based on the valve orifice flow equation: ; In the formula, Indicates branch index, Indicates the first The valve orifice flow rate of each parallel branch Indicates the first The valve orifice flow coefficient of each parallel branch Indicates the first The valve port area gradient of a parallel branch Indicates the first The valve core displacement of each parallel branch Indicates the first The equivalent load pressure of each parallel branch.

[0022] The valve orifice flow equation is linearized at the operating point, including in the first... At the steady-state operating point of each parallel branch, for Perform total differential and calculate the first... The flow increment of each parallel branch : ; In the formula, Indicates increment, To represent partial derivatives, Indicates only When changing rate of change, Indicates only When changing rate of change, Indicates only When changing rate of change, This indicates solving for the partial derivative at the steady-state operating point. Indicates the valve core displacement increment. This indicates an increase in oil supply pressure. This indicates the increase in load pressure.

[0023] Calculate the key parameters of each parallel branch based on the flow gain; No. The flow gain of each parallel branch is: ; No. The oil supply pressure and flow coefficient of each parallel branch are: ; No. The load pressure and flow coefficient of each parallel branch are: ; Based on the key parameters of each parallel branch, the linearized incremental equation is constructed: ; In the formula, Indicates the first The flow gain of each parallel branch Indicates the first The oil supply pressure and flow coefficient of each parallel branch, Indicates the first The load pressure and flow coefficient of each parallel branch.

[0024] Under the quasi-static assumptions, the oil supply pressure satisfies static force equilibrium, and the dynamic equation for the oil supply pressure is: ; ; In the formula, Indicates the rated oil supply pressure. This represents the sum of the flow rates at the valve ports of all parallel branches. Indicates the equivalent oil supply resistance. Indicates the total pressure drop in the pipeline. This is the flow index.

[0025] Under the quasi-static assumptions, based on the dynamic equation of the oil supply pressure, an incremental equation for the oil supply pressure is constructed: ; By combining the dynamic equation of oil supply pressure with the linearized incremental equation, a multi-actuator pressure-flow coupling model is constructed: ; In the formula, Indicates branch index, This indicates the total number of parallel branches.

[0026] In S3, the valve port action coupling gain is: ; In the formula, , indicating the index of the coupling interference branch, Indicates a branch For branch roads The valve port action coupling gain characterizes the branch. Valve movement affects branch The impact on traffic; The load change coupling gain is: ; In the formula, Indicates a branch For branch roads The load variation coupling gain characterizes the branch. Load changes affect branches The impact on traffic.

[0027] Calculate the overall decoupling compensation amount based on the valve port action coupling gain and load change coupling gain: ; ; In the formula, Indicates the first The comprehensive decoupling compensation amount for each parallel branch, Indicates the first The overall flow gain of each parallel branch.

[0028] Obtain the nominal valve core displacement command of each parallel branch, and compensate the nominal valve core displacement command of the corresponding parallel branch based on the comprehensive decoupling compensation amount of each parallel branch to obtain the compensated valve core displacement command: ; ; In the formula, Indicates the compensation after the first Valve core displacement command for each parallel branch Indicates the first The nominal valve core displacement command of each parallel branch This is the proportional control coefficient. For displacement error, The differential control coefficient, This represents the rate of change of error.

[0029] like Figure 1 As shown, a multi-cylinder flow coupling and decoupling control method includes: Step 1 (S1): Sensor signal acquisition to obtain the oil supply pressure before the valve (main pump outlet pressure), the large chamber pressure of each hydraulic cylinder, and the small chamber pressure of each hydraulic cylinder. Pressure sensors are installed at the valve pre-supply pressure measuring point, the large cavity pressure measuring point of each actuator (each parallel branch), and the small cavity pressure measuring point of each actuator in the engineering machinery. The sensors collect the multi-actuator pressure data of the multi-actuator parallel system in real time, including the valve pre-supply pressure of the multi-actuator parallel system, the large cavity pressure of each parallel branch, and the small cavity pressure of each parallel branch. The valve pre-supply pressure measuring point is located on the main oil supply pipeline before the branch point of all parallel branches and after the return oil filter and the check valve. The large cavity measuring point is located near the oil inlet on the rodless side of the cylinder head, and the small cavity measuring point is located near the oil inlet on the rod side of the cylinder bottom.

[0030] Step 2 (S2): Calculate key parameters online based on the signals collected by the sensors; First, the valve orifice flow equation is constructed. Based on the inlet oil pressure (main pump outlet pressure), the large cavity pressure of each hydraulic cylinder, and the small cavity pressure of each hydraulic cylinder, the flow rate through the valve of each hydraulic cylinder is calculated. The flow rate of each branch is calculated using total differential to obtain the flow rate increment of the corresponding branch. The flow rate increment of each branch is then linearized, and the key parameters of each branch are calculated online. Based on the key parameters of each branch, the elements of the cross-coupling gain matrix are calculated, and the cross-coupling gain matrix is ​​constructed to obtain the linearized flow rate increment equation. Under the quasi-static assumption, the oil supply pressure dynamic equation is constructed. The linearized flow rate increment equation and the oil supply pressure dynamic equation are combined to establish a multi-actuator pressure-flow coupling model. The quasi-static assumption means ignoring the instantaneous influence of oil compressibility and pipeline cavity effect on pressure dynamics in the oil supply line, assuming that the inlet oil pressure... The fluctuation is determined solely by the sum of the flow rates of each branch. Equivalent hydraulic resistance through the oil supply line The pressure drop generated determines the pressure transmission, which is completed instantaneously in the pipeline. The hydraulic valve orifice flow rate is calculated using the valve orifice flow equation under the quasi-static assumption. The flow rate through the electro-hydraulic proportional valve is calculated using the valve orifice flow equation, where the valve orifice flow rate is... The flow rate through the valve orifice is expressed in m³ / s. The orifice flow coefficient is a dimensionless constant determined by the valve orifice geometry, reflecting the shape of the throttling orifice and the effect of fluid contraction; it is typically taken as 0.60 to 0.65. The orifice area gradient is expressed in meters (m). For electro-hydraulic proportional valves, the orifice area gradient is the circumferential width of the valve core; for spool valves, the orifice area gradient refers to the rate of change of the flow area per unit displacement of the valve core, i.e., the circumferential width of the valve orifice. The valve core displacement is expressed in meters (m), representing the valve orifice opening. The hydraulic oil density is expressed in kg / m³. The upstream oil supply pressure is the pressure delivered from the main pump outlet to the valve inlet via pipeline, equivalent to the main pump outlet pressure (main pump outlet pressure in a multi-actuator parallel system), expressed in Pa. The equivalent load pressure refers to the hydraulic cylinder working chamber pressure or the valve outlet pressure, expressed in Pa. The external load force acting on the piston rod of the hydraulic cylinder is such that the effective working area of ​​the large cavity is equal to the effective area of ​​the piston, i.e. .

[0031] The valve orifice flow equation quantitatively describes the nonlinear relationship between the throttling flow rate at the valve orifice, the valve orifice opening, and the pressure difference across the valve orifice. In a multi-actuator parallel system of a hydraulic excavator, this formula reveals the root cause of flow competition: when the valve orifice opening of a certain branch (such as the boom) increases, the flow rate of that branch... The increase leads to an increase in total flow and a rise in pipeline pressure drop, thus increasing the pressure on the public oil supply. Descending; for other branches (such as the boom), if their valve opening remains unchanged, due to The drop leads to a pressure difference Reduce its flow rate Passive descent (the mathematical essence of coupling interference). When multiple actuators are connected in parallel, the sum of the flow rates in each branch changes the total flow rate in the oil supply line, which in turn affects the hydraulic resistance of the line. Causes oil supply pressure before valve The changes in pressure create flow-pressure coupling between branches. To quantitatively describe this coupling, the valve orifice flow equation needs to be linearized at the operating point.

[0032] In the The steady-state operating point of each branch ( ) Perform total differential: ; In the formula, To represent partial derivatives, To represent the differential, Indicates only When changing rate of change, Indicates only When changing rate of change, Indicates only When changing Rate of change; expressed in increments. Replace the differential symbol And at the steady-state operating point ( The partial derivative is calculated at point () to obtain the flow increment. The expression; where, This indicates solving for the partial derivative at the steady-state operating point, and represents the value of that partial derivative at a specific operating point (usually denoted as the steady-state operating point value). This indicates calculation at the steady-state operating point. (equivalent to calculation) (and by substituting the steady-state operating point for numerical solution), this is used to calculate the rate of change in flow rate caused by minute changes in valve core displacement, reflecting the valve's sensitivity. This indicates calculation at the steady-state operating point. It is used to calculate the rate of change in flow rate caused by a small change in oil supply pressure. This indicates calculation at the steady-state operating point. Used to measure the rate of change in flow rate caused by minute changes in load pressure. Indicates the first The valve core displacement increment of each parallel branch This indicates an increase in oil supply pressure. Indicates the first The load pressure increment of each parallel branch. The working equations of a hydraulic system are nonlinear, and their partial derivatives (such as flow gain) change with the operating point. The steady-state operating point is the numerical combination of a multi-actuator parallel system under a certain steady-state condition, satisfying... This indicates that the first-order Taylor expansion at that point only occurs under small perturbations. Valid within the specified range. Subscript for branch road number, , indicating the branch being analyzed.

[0033] No. Flow gain of each parallel branch Indicates the oil supply pressure and load pressure Under the condition that remains unchanged, the first The change in flow rate caused by a unit change in the valve core displacement of each branch. This parameter reflects the branch's sensitivity to valve core displacement commands. The larger the value, the greater the flow rate change that the same change in valve core displacement can produce. , Indicates the first Steady-state valve core displacement of a parallel branch Steady-state main pump outlet pressure, No. Steady-state load pressure of a parallel branch.

[0034] No. Oil supply pressure and flow coefficient of each parallel branch Indicates the valve core displacement and load pressure The change in flow rate caused by a unit change in oil supply pressure, while remaining constant. This parameter reflects the sensitivity of the branch to fluctuations in oil supply pressure. The larger the value, the more easily fluctuations in the oil supply pressure can cause passive changes in the flow rate of that branch, meaning that the branch is more susceptible to coupling interference from other branches.

[0035] No. Load pressure and flow coefficient of each parallel branch Indicates the valve core displacement and oil supply pressure Under the condition of constant load pressure, the change in flow rate caused by a unit change in load pressure. Since the pressure difference at the valve orifice decreases and the flow rate decreases when the load pressure increases, its partial derivative is negative; therefore, after taking the negative sign... It is positive. Numerically... This parameter reflects the degree to which changes in the branch's own load affect its flow rate.

[0036] The above three parameters are all calculated in real time from the oil supply pressure, load pressure and valve core displacement at the current working point, and are the basis for subsequent calculation of the cross-coupling gain matrix.

[0037] The main pump and oil supply lines are treated as a non-ideal constant pressure source, and an equivalent oil supply hydraulic resistance is introduced. Under the quasi-static assumption, neglecting the pipeline cavity and oil compressibility, the oil supply pressure is no longer an independent state variable, but instantaneously satisfies static force equilibrium. A dynamic equation for the oil supply pressure is then constructed to characterize the common oil supply pressure before the valve. Sum of flow rates of each branch Relationship; ; in, This refers to the pump outlet rated pressure, which is also the rated oil supply pressure. This is the sum of the valve orifice flow rates of all parallel branches. Indicates branch index, This represents the total number of parallel branches, used for summing and traversing all branches.

[0038] Equivalent oil supply resistance Defined as the distance from the main pump outlet to each multi-port valve. The total pressure loss coefficient of the oil supply pipeline is determined by both the friction loss and the local resistance loss along the pipeline: ; In the formula, This refers to the total pressure drop in the pipeline, which is the total pressure drop generated by the oil flowing through the oil supply pipeline from the main pump outlet to the inlet of each parallel branch proportional valve / multi-way valve. It is equal to the friction loss along the pipeline. express of Power of 1 This is the flow index. It can be obtained through offline experimental calibration before leaving the factory, or it can be estimated online during operation using the recursive least squares method.

[0039] Step 3 (S3): Derive the cross-coupling gain matrix; From the fuel supply pressure increment equation With the linearized flow increment equation By combining the equations, a unified expression for the increment of oil supply pressure is derived, and a multi-actuator pressure-flow coupling model is constructed. The unified expression for the increment of oil supply pressure indicates that the oil supply pressure fluctuation... The valves of all branches are activated ( ) and load changes ( The denominator is jointly determined. This term reflects the system's pressure stiffness. The larger the value, the lower the sensitivity of pressure fluctuations to disturbances. To quantify the two types of coupled disturbances separately, the multi-actuator pressure-flow coupling model is discussed under two operating conditions, and the branches are substituted back for each condition. The linearized incremental equation.

[0040] First, calculate the valve port coupling gain between each parallel branch; Valve port coupling refers to only branch-type coupling. The valve opening changes ( The valve ports of the remaining branches remain unchanged. ), and the load on all branches remains unchanged ( Substituting the valve port actuation coupling condition into the multi-actuator pressure and flow coupling model, the oil supply pressure increment under the valve port actuation coupling condition is calculated: ; Substituting the above formula into the branch... The linearized incremental equation, and in , Under the following conditions: ; Define valve port action coupling gain branch road Valve opening degree for branch Partial derivative of flow rate ( ): ; The valve port action coupling gain was quantized. When the opening of each branch valve increases by one unit, the decrease in oil supply pressure leads to the... The amount by which the flow of a branch is passively reduced. A negative value indicates that an increase in the opening of the other branch leads to a decrease in the flow of this branch.

[0041] Then calculate the load change coupling gain between each parallel branch; Load variation coupling refers to only branch coupling The load changes ( The loads of the remaining branches remain unchanged. ), and the opening degree of all valve ports remains unchanged ( ).

[0042] Substituting the load variation coupling condition into the multi-actuator pressure-flow coupling model, the oil supply pressure increment under the load variation coupling condition is calculated: ; Substituting the above formula into the branch... The linearized incremental equation, and in , Under the following conditions: ; Define load variation coupling gain branch road Load pressure on branch Partial derivative of flow rate ( ): ; The load variation coupling gain quantized the first When the load pressure of each branch increases by one unit, the increase in oil supply pressure leads to the... The amount of passive increase in traffic on each branch. A positive value indicates that an increase in the load on the other side has led to an increase in the flow of this branch.

[0043] Establish the cross-coupling gain matrix; Integrated valve port action coupling gain Coupling gain with load variation The coupling relationships between the branches are organized into a matrix form. For those containing For a system with multiple parallel branches, the relationship between the flow rate increment vector, the valve core displacement increment vector, and the load pressure increment vector is as follows: ; in, The valve port action coupling gain matrix ( Its diagonal elements are the overall flow gain of each branch. Off-diagonal elements are ( ); For load variation coupling gain matrix ( Its diagonal elements are the load influence coefficients of each branch. Off-diagonal elements are ( ).

[0044] Two types of cross-coupling gains are derived from a unified expression for the oil supply pressure increment: valve orifice action coupling gain and load change coupling gain. The valve orifice action coupling gain is represented by the matrix elements of the valve orifice action coupling gain matrix, and the load change coupling gain is represented by the matrix elements of the load change coupling gain matrix. The relationship between the flow rate increment vector, the valve core displacement increment vector, and the load pressure increment vector forms the core theoretical basis for the decoupling compensation module. In each control cycle, based on the real-time acquired oil supply pressure... Load pressure of each branch and valve core displacement Online calculation of each branch , , Based on each branch , , Calculate the elements of the coupling gain matrix and Construct the cross-coupling gain matrix. This is done through real-time calculation. and The matrix can accurately quantify the interference intensity of any joint movement on any other joint, and then feedforward compensation in the controller can be used to cancel the interference.

[0045] Step 4: Calculate the overall decoupling compensation amount online; Using a PD controller, the nominal valve core displacement command for each parallel branch is calculated in real time based on the error between the desired and actual displacement. ; ; ; in, The proportional control coefficient is taken as follows: , Let be the differential control coefficient, and take . , For displacement error, The rate of change of error, the differential term It is used to predict future trends of errors, increase the system footprint, and suppress overshoot and oscillations.

[0046] Based on the valve orifice action coupling gain and load change coupling gain, calculate the first... The overall decoupling compensation amount of each branch : ; In the formula, To account for the overall flow gain after oil supply pressure feedback: ; ; Step 5: Superimpose the comprehensive decoupling compensation amount with the nominal valve core displacement command to generate the compensated valve core control command; For the Each actuator (parallel branch) adds the comprehensive decoupling compensation amount to the nominal valve core displacement command to obtain the compensated valve core displacement command.

[0047] Step six: Send the compensated valve core control command to the electro-hydraulic proportional valve to drive the hydraulic cylinder to move.

[0048] S5 corresponds to steps four and five.

[0049] The boom hydraulic cylinder (cylinder 1, the active cylinder) and stick hydraulic cylinder (cylinder 2, the passive cylinder) of a 22-ton hydraulic excavator were used as the subjects of this study. Cylinder 1 performs a large-amplitude sinusoidal motion (amplitude 0.15m, frequency 0.4Hz), while cylinder 2 performs a small-amplitude sinusoidal motion (amplitude 0.03m, frequency 0.3Hz), simulating the coordinated working condition of active boom lifting and stick fine-tuning in actual operation. Both cylinders share the same main pump for oil supply, and the equivalent hydraulic resistance of the oil supply pipeline is [not specified]. The main parameters of the multi-cylinder system are shown in Table 1.

[0050] Table 1. Main parameters of the multi-cylinder system; .

[0051] The experiment was divided into two groups for comparison: Group A was a control experiment without decoupling compensation; Step A1: Set the desired trajectory in the main controller.

[0052] The desired displacement of cylinder 1 is: m; The desired displacement of cylinder 2 is: m; In the formula, Indicates the time.

[0053] Step A2: Using a PD controller, calculate the nominal valve core displacement commands for the driving cylinder and the driven cylinder based on the error between the desired displacement and the actual displacement. and .

[0054] Step A3, calculate the nominal valve core displacement command in step A2. and It is sent directly to the electro-hydraulic proportional valve without any decoupling compensation processing.

[0055] In step A4, the electro-hydraulic proportional valve drives the two hydraulic cylinders according to the received instructions.

[0056] Step A5: Repeat steps A1 to A4 in each control cycle until the simulation ends.

[0057] Group B consists of experiments using the decoupling compensation method of this invention; Step B1 is the same as step A1; the desired trajectory is set in the main controller. The desired displacement of cylinder 1 is... m, the desired displacement of cylinder 2 is m, Indicates the time.

[0058] Step B2 is the same as step A2. Using a PD controller, the nominal valve core displacement commands for the driving cylinder and the driven cylinder are calculated based on the error between the desired displacement and the actual displacement. and .

[0059] Step B3: The decoupling compensation module reads the current oil supply pressure. Two-cylinder load pressure (Calculated by combining the pressure sensors of each chamber with the piston area) and the current valve core displacement of each cylinder. .

[0060] Step B4: Calculate the flow gain of each cylinder at the current operating point. And oil supply pressure and flow coefficient ; Step B5: Calculate the elements of the cross-coupling gain matrix to construct the cross-coupling gain matrix. Wherein... Indicates the branch that produces coupling. The valve's movement affects the branch currently being analyzed. The impact of traffic ( ), Indicates a branch Load changes affect branches The impact of traffic ( ):in, This represents the total number of parallel branches; Step B6: Calculate the decoupling compensation amount ( ); Step B7: Superimpose the decoupling compensation amount with the nominal valve core displacement command to obtain the compensated valve core displacement command; Step B8: Send the compensated valve core displacement command to the electro-hydraulic proportional valve to drive the two hydraulic cylinders to move; Step B9: Repeat steps B1 to B8 in each control cycle until the simulation ends.

[0061] Comparison of experimental results: Both sets of experiments used the exact same desired trajectory, controller parameters, and hydraulic system parameters. The only difference was that group B added the decoupling compensation module of this invention between the PD controller and the electro-hydraulic proportional valve. The experimental results are as follows: Figure 3 , Figure 4 As shown in Table 2.

[0062] Table 2 Comparison of performance indicators before and after decoupling compensation; .

[0063] As shown in Table 2, in Group A (no decoupling), the large-amplitude movement of cylinder 1 causes fluctuations in the fuel supply pressure, resulting in a dragging motion error in cylinder 2. In Group B (with decoupling), the decoupling compensation module actively corrects the valve core displacement commands of the two cylinders by calculating the cross-coupling gain in real time, reducing the mutual interference caused by flow competition. This reduces the tracking error of cylinder 1 by 3.9% and the dragging motion error of cylinder 2 by 2.1%. As shown in Table 2, the error of cylinder 2 is greater than that of cylinder 1 and exhibits higher frequency fluctuations. This is because cylinder 2 has a small movement amplitude, a weak controller output signal, and poor anti-interference ability against fuel supply pressure fluctuations. By calculating the cross-coupling gain in real time and performing feedforward compensation, the errors of both cylinder 2 and cylinder 1 are reduced, demonstrating the applicability of the multi-cylinder flow coupling decoupling method under different motion states.

[0064] It should be noted that although the above derivation uses a constant pressure variable pump as a reference, the core of this invention lies in compensating for the hydraulic resistance in the oil supply line. This leads to dynamic pressure coupling among multiple actuators. For systems using fixed displacement pumps, the flow competition and pressure coupling phenomena generated by the actuators through common pipeline sections are equally significant. For load-sensitive pump systems, although the mutual influence of actuator loads can be isolated by pressure compensation valves in steady state, both the pump variable displacement mechanism and the pressure compensation valve exhibit response lag during dynamic response. The multi-cylinder flow coupling decoupling method provided in this invention can serve as a beneficial supplement to existing multi-actuator systems. Therefore, as long as a measurable oil supply pressure exists in the system... and load pressure The multi-cylinder flow coupling decoupling method is applicable and has good universality.

[0065] Figure 2 This is a schematic diagram of the equivalent model of the multi-actuator parallel oil supply system addressed in this invention. Taking a three-cylinder parallel system as an example, this model reveals the physical mechanism of flow-pressure coupling between the hydraulic cylinders, which forms the basis for the subsequent decoupling control method. Figure 2 As shown, the hydraulic oil output from the main pump is delivered to each proportional valve via the supply pipeline. The rated outlet pressure of the main pump (steady-state outlet pressure of the main pump) is... Due to friction loss and local resistance loss in the oil supply pipeline, hydraulic oil experiences a pressure drop within the pipeline. In this model, the pressure loss characteristics of the oil supply pipeline are represented as an equivalent oil supply resistance, and the total flow rate in the pipeline is the sum of the flow rates of each parallel branch, i.e. The common oil supply pressure before the valve is calculated based on the oil supply pressure increment equation. When the flow rate of any cylinder changes, This change leads to variations in pipeline pressure drop, which in turn causes fluctuations in the common pressure upstream of the valve. This common pressure upstream of the valve acts simultaneously on the inlet of each proportional valve in the series. The valve core displacement of the first proportional valve is denoted as... Its export flow is The hydraulic cylinder 1 is driven to move, and the piston displacement is denoted as... The speed of motion is denoted as The piston rod of hydraulic cylinder 1 is subjected to an external load force. (Including the effects of the robotic arm's own weight, inertia, and working resistance). Similarly, the second and third links respectively... , For valve core displacement, , To achieve the desired outlet flow rate, hydraulic cylinders 2 and 3 are driven, with each cylinder bearing its own external load force. and This model reveals two transmission paths for coupled interference in a multi-cylinder parallel system. Path one is valve port action coupling, which occurs when the valve port opening of the proportional valve in a certain branch changes (e.g., when the valve port opening changes). (Increase), the flow rate of this branch The increase led to a decrease in total flow. Increased pressure leads to increased pressure drop in the oil supply line and increased common pressure before the valve. The pressure decreases. This pressure decrease is transmitted through the other branch valves in parallel. With the opening degree of the other branch valves remaining unchanged, the pressure difference at their valve ports decreases, and the flow rate... , Passive reduction causes unintended dragging motion in the undisturbed hydraulic cylinders. Path two is load change coupling; when the external load force in one branch changes (e.g., ... (Increase), the equivalent load pressure increases, and the flow rate of this branch remains constant. Reduce, total flow As a result, the pressure drop in the pipeline decreases, and the common pressure before the valve decreases. The pressure rises, which in turn increases the differential pressure at the valve ports of other branches, passively increasing the flow rate and similarly generating undesirable entanglement motion. Based on Figure 2The above coupling mechanism of the equivalent model shown can be used to design a feedforward decoupling compensator by calculating the cross-coupling gain between each branch online, and then correcting the valve core displacement command in real time, thereby eliminating the flow-pressure coupling interference between cylinders and realizing high-precision collaborative control of multiple cylinders.

[0066] Figure 3 The displacement tracking comparison diagram of cylinder 1 (active cylinder) in the simulation of the two-cylinder parallel system provided by this invention; Figure 4 for Figure 3 Enlarged detail view of area A in the middle; Figure 3 The horizontal axis represents time, ranging from 0 to 6 seconds, and the vertical axis represents displacement, ranging from 0.35 to 0.7 meters. Figure 4 The horizontal axis represents time, ranging from 0.3 to 0.9 seconds, and the vertical axis represents displacement, ranging from 0.61 to 0.66 meters. The black dashed line represents the desired displacement of cylinder 1 (the active cylinder), with a period of 2.5 seconds, an amplitude of 0.15 meters, and a mean of 0.5 meters (peak value ≈ 0.65 meters, valley value ≈ 0.35 meters). Figure 3 and Figure 4 As shown, cylinder 1 itself has weak coupling interference (because cylinder 2 moves slowly and with small amplitude). The curves with and without decoupling (red) and with decoupling (blue) highly coincide with the desired trajectory. At the peaks and troughs, the curve with decoupling (blue) fits the desired trajectory even better. The desired peak value reaches 0.65 m at t≈0.625s. Before reaching the peak, the curves with and without decoupling almost completely overlap, and there is a slight difference after reaching the peak, reflecting the optimization of detail tracking by decoupling.

[0067] Figure 5 The displacement tracking comparison diagram of cylinder 2 (passive cylinder) in the simulation of the two-cylinder parallel system provided by this invention; Figure 6 for Figure 5 Enlarged detail view of region B in the middle; Figure 5 The horizontal axis represents time, ranging from 0 to 6 seconds, and the vertical axis represents displacement, ranging from 0.36 to 0.44 meters. The black dashed line represents the desired displacement of cylinder 2 (the passive cylinder), with a period of approximately 3.33 seconds, an amplitude of 0.03 meters, and a mean of 0.4 meters (peak value approximately 0.43 meters, valley value approximately 0.37 meters). Figure 5 and Figure 6 As shown, the undecoupled (red) curve exhibits slight high-frequency fluctuations, while the decoupled (blue) curve shows relatively smoother fluctuations, better matching the expected value. The expected peak value reaches 0.433 m at t≈0.83s; the fluctuation amplitude of the undecoupled curve is approximately ±0.003 m, while the fluctuation amplitude of the decoupled curve is approximately ±0.002 m, indicating a significant reduction in deviation with decoupling.

[0068] The above 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 with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-cylinder flow coupling and decoupling control method, characterized in that, include: S1. Real-time acquisition of multi-actuator pressure data through sensors, including the valve pre-supply pressure of the multi-actuator parallel system, the large chamber pressure of each parallel branch, and the small chamber pressure of each parallel branch; S2. Under the quasi-static assumption, construct the valve orifice flow equation, calculate the valve orifice flow of each parallel branch based on the pressure data of multiple actuators, linearize the valve orifice flow equation at the operating point, calculate the key parameters of each parallel branch, and construct a multi-actuator pressure and flow coupling model. The key parameters include flow gain, oil supply pressure and flow coefficient, and load pressure and flow coefficient. S3. Based on the key parameters of each parallel branch, the coupling gain of valve port action between each parallel branch and the coupling gain of load change between each parallel branch are calculated through the multi-actuator pressure and flow coupling model, and a cross-coupling gain matrix is ​​constructed. S4. Obtain the nominal valve core displacement command of each parallel branch, calculate the comprehensive decoupling compensation amount of each parallel branch based on the valve port action coupling gain and load change coupling gain of each parallel branch, compensate the nominal valve core displacement command of the corresponding parallel branch through the comprehensive decoupling compensation amount of each parallel branch, and output the compensated valve core displacement command to drive the movement of the hydraulic cylinder of the corresponding branch.

2. The multi-cylinder flow coupling and decoupling control method according to claim 1, characterized in that, In S2, the valve orifice flow equation is: ； ； In the formula, Indicates the flow rate at the valve orifice. Indicates the valve orifice flow coefficient. Indicates the valve orifice area gradient. Indicates valve core displacement. Indicates the density of hydraulic oil. Indicates the oil supply pressure before the valve. Indicates equivalent load pressure. Indicates external load force. Indicates the effective area of ​​the piston. Indicates the pressure in the large cavity. Indicates the pressure in the small cavity. Indicates the effective working area of ​​the large cavity. This indicates the effective working area of ​​the small cavity.

3. The multi-cylinder flow coupling and decoupling control method according to claim 2, characterized in that, Calculate the valve orifice flow rate for each parallel branch based on the valve orifice flow equation: ； In the formula, Indicates branch index, Indicates the first The valve orifice flow rate of each parallel branch Indicates the first The valve orifice flow coefficient of each parallel branch Indicates the first The valve port area gradient of a parallel branch Indicates the first The valve core displacement of each parallel branch Indicates the first The equivalent load pressure of each parallel branch.

4. The multi-cylinder flow coupling and decoupling control method according to claim 3, characterized in that, The valve orifice flow equation is linearized at the operating point, including in the first... At the steady-state operating point of each parallel branch, for Perform total differential and calculate the first... The flow increment of each parallel branch : ； In the formula, Indicates increment, To represent partial derivatives, Indicates only When changing rate of change, Indicates only When changing rate of change, Indicates only When changing rate of change, This indicates solving for the partial derivative at the steady-state operating point. Indicates the valve core displacement increment. This indicates an increase in oil supply pressure. This indicates the increase in load pressure.

5. The multi-cylinder flow coupling and decoupling control method according to claim 4, characterized in that, Calculate the key parameters of each parallel branch based on the flow gain; No. The flow gain of each parallel branch is: ； No. The oil supply pressure and flow coefficient of each parallel branch are: ； No. The load pressure and flow coefficient of each parallel branch are: ； Based on the key parameters of each parallel branch, the linearized incremental equation is constructed: ； In the formula, Indicates the first The flow gain of each parallel branch Indicates the first The oil supply pressure and flow coefficient of each parallel branch, Indicates the first The load pressure and flow coefficient of each parallel branch.

6. The multi-cylinder flow coupling and decoupling control method according to claim 5, characterized in that, Under the quasi-static assumptions, the oil supply pressure satisfies static force equilibrium, and the dynamic equation for the oil supply pressure is: ； ； In the formula, Indicates the rated oil supply pressure. This represents the sum of the flow rates at the valve ports of all parallel branches. Indicates the equivalent oil supply resistance. Indicates the total pressure drop in the pipeline. This is the flow index.

7. The multi-cylinder flow coupling and decoupling control method according to claim 6, characterized in that, Under the quasi-static assumptions, based on the dynamic equation of the oil supply pressure, an incremental equation for the oil supply pressure is constructed: ； By combining the dynamic equation of oil supply pressure with the linearized incremental equation, a multi-actuator pressure-flow coupling model is constructed: ； In the formula, Indicates branch index, This indicates the total number of parallel branches.

8. The multi-cylinder flow coupling and decoupling control method according to claim 7, characterized in that, In S3, the valve port action coupling gain is: ； In the formula, , indicating the index of the coupling interference branch, Indicates a branch For branch roads The valve port action coupling gain characterizes the branch. Valve movement affects branch The impact on traffic; The load change coupling gain is: ； In the formula, Indicates a branch For branch roads The load variation coupling gain characterizes the branch. Load changes affect branches The impact on traffic.

9. The multi-cylinder flow coupling and decoupling control method according to claim 8, characterized in that, Calculate the overall decoupling compensation amount based on the valve port action coupling gain and load change coupling gain: ； ； In the formula, Indicates the first The comprehensive decoupling compensation amount for each parallel branch, Indicates the first The overall flow gain of each parallel branch.

10. The multi-cylinder flow coupling and decoupling control method according to claim 9, characterized in that, Obtain the nominal valve core displacement command of each parallel branch, and compensate the nominal valve core displacement command of the corresponding parallel branch based on the comprehensive decoupling compensation amount of each parallel branch to obtain the compensated valve core displacement command: ； ； In the formula, Indicates the compensation after the first Valve core displacement command for each parallel branch Indicates the first The nominal valve core displacement command of each parallel branch This is the proportional control coefficient. For displacement error, The differential control coefficient, This represents the rate of change of error.

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