Excavator hydraulic servo system control method based on fuzzy flow parameters

Abstract

The invention discloses an excavator hydraulic servo system control method based on fuzzy flow parameters, and mainly relates to the technical field of excavator automatic control, in particular to the excavator hydraulic servo system control method based on the fuzzy flow parameters. According to the method, by collecting the valve opening degrees of a movable arm, a bucket rod and a bucket of the excavator during multi-joint linkage of the excavator, the flow distributed to three joints during multi-joint linkage of the excavator, namely the load flow of the three joints, is accurately calculated through a continuity equation and a force balance equation of a valve-controlled hydraulic cylinder. And according to the valve opening and the load flow, a fuzzy control rule table is constructed, fuzzy parameters are calculated, and fuzzy control rules are summarized. The sliding mode control based on the index approaching rate is adopted according to the fuzzy control rule, the system control rate is calculated, the control quantity of a system controller is corrected, the control precision of the system is improved, meanwhile, a flow sensor does not need to be installed, and cost is reduced.

Description

Technical Field

[0001] The invention relates to the field of excavator control technology, mainly to the field of excavator automatic control technology, and specifically refers to a control method for an excavator hydraulic servo system based on fuzzy flow parameters. Background Art

[0002] With the continuous development of science and technology, automation technology has been widely used in various fields. The construction machinery industry is also facing the transformation and upgrading of automation. The development of excavator automation not only improves the labor intensity of workers and overcomes the harsh construction conditions, but also improves the operation efficiency and quality.

[0003] In recent years, the automatic control technology of excavators has developed rapidly, but most of the current excavator electronic servo hydraulic system modeling is based on a single-cylinder model, and rarely involves linkage. However, the actual hydraulic system is a multivariable coupling system. Because the total flow of the oil supply pipeline is limited and the oil pressure is limited, when the flow exceeds the upper limit, the flow entering each joint will decrease. In addition, in order to achieve functions including straight-line walking, rotation priority, walking boost, confluence, and regeneration, a complex circuit structure is adopted. When multiple joints are linked, the flow of each joint is coupled with each other, and it is difficult to accurately calculate the flow allocated to each joint, resulting in changes in model parameters and increasing the difficulty of control. At the same time, each excavator has differences due to its manufacturing and assembly errors. The debugging process before leaving the factory will also cause different control parameters of the whole machine, so even the same model of excavator product model parameters are not exactly the same. Summary of the invention

[0004] Aiming at the problem that it is difficult to accurately calculate the flow rate allocated to each joint when multiple joints are linked in the existing electronically controlled servo hydraulic system of an excavator, which affects the control accuracy of the system, the present invention provides an excavator hydraulic servo system control method based on fuzzy flow parameters.

[0005] A control method for an excavator hydraulic servo system based on fuzzy flow parameters, comprising:

[0006] S1. Set key points, install angle sensors at the three joints of the excavator's boom, arm, and bucket, obtain absolute angle data of the three joints of the excavator, and calculate the joint angles based on the absolute angle data;

[0007] S2. Calculate the linear displacement of the cylinder piston of the corresponding joint according to the conversion relationship between the joint angle and the linear displacement of the joint cylinder piston;

[0008] S3. Calculate the load flow rate through the continuity equation and force balance equation of the valve-controlled hydraulic cylinder according to the joint angle and the linear displacement of the cylinder piston;

[0009] S4. Obtain the valve opening corresponding to different load flows, and summarize the fuzzy control rules according to the valve opening and load flow;

[0010] S5. Construct a multi-input multi-output MIMO model, calculate the system model parameters according to the fuzzy control rules, and correct the output control quantity of the system model;

[0011] S6. Perform sliding mode control on the excavator hydraulic servo system based on the output control quantity of the modified system model.

[0012] In S1, the key points are set to include the connection between the excavator body and the boom as point O, the connection between the boom hydraulic cylinder and the body as point A, the connection between the boom hydraulic cylinder and the boom as point B, the connection between the dipper arm hydraulic cylinder and the boom as point C, the connection between the dipper arm hydraulic cylinder and the dipper arm as point D, the connection between the boom and the dipper arm as point E, the connection between the bucket hydraulic cylinder and the dipper arm as point F, the connection between the bucket hydraulic cylinder and the rocker arm and the connecting rod as point I, the connection between the rocker arm and the dipper arm as point G, the connection between the connecting rod and the dipper arm as point J, the connection between the bucket and the dipper arm as point H, and the bucket tooth tip as point L;

[0013] Angle sensors are installed at the three joints of the excavator's boom, arm, and bucket. The angle sensor of the boom joint is parallel to BE, the angle sensor of the arm joint is parallel to EH, and the angle sensor of the bucket joint is parallel to GI. The data obtained by the angle sensor is the angle data between the three joints of the excavator's boom, arm, and bucket and the horizontal plane, which is the absolute angle data of the three joints of the excavator, recorded as θ 10 ,θ 20 ,θ 30 , construct the DH coordinate system, convert the absolute angle data of the three joints of the excavator according to the DH method, record the converted absolute angle data of the three joints of the excavator as θ1, θ2, and θ3 respectively, and calculate the joint angles of the three joints of the excavator according to the DH conversion angle data.

[0014] In S2, the conversion relationship between the excavator joint angle and the linear displacement of the joint cylinder piston is:

[0015]

[0016] ∠AOB=∠EOB+θ1+∠AOx;

[0017]

[0018] ∠CED=π-∠CEO-∠HED+θ2;

[0019]

[0020] ∠FGI=2π-∠FGE-∠EGH-∠HGI;

[0021] In the formula, π dB 、x dA 、x dBu are the linear displacements of the cylinder pistons corresponding to the three joints of the boom, the dipper arm, and the bucket, π is the flat angle, l OA , l OB are the distances from point O to point A and point B, ∠AOB and ∠EOB are the angles between the lines AO, EO and OB, ∠AOx is the angle between the line AO ​​and the horizontal direction x, l CE , l DE are the distances from point C and point D to point E, ∠CED is the angle between the straight lines CE and ED, ∠CEO is the angle between the straight lines CE and EO, ∠HED is the angle between the straight lines HE and ED, l FG , l IG are the distances from point F and point I to point G respectively, ∠FGI is the angle between the straight lines FG and GI, ∠FGE is the angle between the straight lines FG and GE, ∠EGH is the angle between the straight lines EG and GH, and ∠HGI is the angle between the straight lines HG and GI.

[0022] In S3, the continuity equation of the valve-controlled hydraulic cylinder is:

[0023]

[0024] p L =p1-np2;

[0025]

[0026] Where Q1 is the flow rate into the hydraulic cylinder, d() is the derivative, and x d is the linear displacement of the cylinder piston, dt is the time step, C i is the internal leakage coefficient, C e is the external leakage coefficient, C iL is the equivalent leakage coefficient, C es is the additional leakage coefficient, p1 and p2 are the oil pressures of the rodless and rod chambers of the hydraulic cylinder respectively, β e is the effective bulk elastic modulus, V1 is the volume of the rodless chamber of the hydraulic cylinder, is the first-order differential of the linear displacement of the cylinder piston; p L is the load pressure of the hydraulic cylinder, p s is the oil source pressure, is the equivalent volume, is the equivalent load pressure, n is the flow ratio, A1 and A2 are the piston areas of the rodless and rod chambers of the hydraulic cylinder respectively, Q L is the load flow, C d is the flow coefficient of the slide valve, ω is the area gradient of the slide valve, Xv is the valve opening, and ρ is the pressure oil density.

[0027] In S3, the force balance equation is:

[0028]

[0029] In the formula, is the second-order differential of the linear displacement of the cylinder piston, M is the load mass, B p is the viscous damping coefficient, K is the elastic coefficient, F l is the external interference force;

[0030] According to the continuity equation and force balance equation of the valve-controlled hydraulic cylinder, the load flow is:

[0031]

[0032] K F It is a fuzzy parameter, which represents the influence degree between the three joints when the joints are linked. The maximum membership average method is used to calculate the fuzzy parameter. The fuzzy parameter is divided into five levels: very small influence VS, small influence S, medium influence M, large influence L, and very large influence VL.

[0033] In S4, the valve opening is divided into three levels: small opening SD, medium opening MD, and large opening LD. The handle command is input to one of the three joints of the excavator boom, dipper arm, and bucket respectively. According to the valve opening of the other two joints, the triangular membership function is constructed, and the joint membership corresponding to the different levels of valve opening of the other two joints is calculated. The fuzzy control algorithm Mamdani algorithm is used to calculate the fuzzy parameters of the input handle command joint according to the joint membership of the other two joints, summarize the fuzzy control rules, and construct a fuzzy control rule table.

[0034] Construct a multiple-input multiple-output MIMO model and define the input matrix x and output matrix y as follows:

[0035]

[0036] In the formula, x i , i=1, 2, 3…9, represents the i-th input parameter of the system; represents the first-order differential of the i-th input parameter of the system; x dB 、x dA 、x dBu are the linear displacements of the cylinder pistons of the boom, arm, and bucket, respectively, v dB 、v dA 、v dBu are the linear displacement speeds of the cylinder pistons of the boom, dipper rod, and bucket, respectively, and a dB 、a dA 、a dBuare the linear displacement accelerations of the cylinder pistons of the boom, arm, and bucket, respectively; a 1n , m = 1, 2, 3, represents the nominal value of the mth sub-model of the system; a 2n , m = 1, 2, 3, represents the model parameters of the mth sub-model of the system; d n , m = 1, 2, 3, represents the external interference of the mth sub-model of the system; u m , m = 1, 2, 3, represents the control rate of the mth sub-model of the system, and sgn() is the sign function.

[0037] In S6, the synovial surface s is:

[0038] s=C1e1+C2e2+e3;

[0039]

[0040] In the formula, C1>0, C2>0, C1 and C2 are error coefficients, e1 is tracking error, e2 and e3 are definition errors, are the first-order differentials of the linear displacements of the cylinder pistons of the boom, arm, and bucket, respectively. They are the second-order differentials of the linear displacements of the cylinder pistons corresponding to the three joints of the boom, arm, and bucket.

[0041] Differentiate the synovial surface s and get

[0042]

[0043] In the formula, is the first-order differential of the tracking error, is the first-order differential of the definition error, are the third-order differential values ​​of the linear displacement of the cylinder piston corresponding to the three joints of the boom, the dipper arm, and the bucket; g(x v ) m , m = 1, 2, 3, represents the output of the mth sub-model of the system, and g(x) is the system output; represents the first-order differential of the external disturbance force, u is the control rate of the system, x vV 、x vA 、x vBu They represent the valve openings corresponding to the three joints of the boom, arm and bucket respectively; a1 is the system nominal value matrix; a2 is the system model parameter matrix.

[0044] right Adopt sliding mode control based on exponential reaching rate:

[0045]

[0046] y=Cx+Du;

[0047] Where ε>0, k c >0, ε represents the control parameter, k c represents the leakage coefficient, x is the input matrix, The first-order differential matrix of the input matrix, y is the output matrix, A is the input coefficient, B is the input control coefficient, C is the output coefficient, and D is the output control coefficient;

[0048] The control rate u of the system is:

[0049]

[0050] The initial control rate u of the system is obtained by inputting the preset trajectory. During the actual control process of the system, the fuzzy flow parameters are calculated in real time, and the control rate of the system is also updated in real time.

[0051] Compared with the prior art, the present invention has the following beneficial effects: the present invention collects the valve openings of the excavator boom, dipper rod and bucket when the excavator has multiple joints, and accurately calculates the flow rate allocated to the three joints of the excavator when the excavator has multiple joints, that is, the load flow rate of the three joints, through the continuity equation and force balance equation of the valve-controlled hydraulic cylinder. According to the valve opening and the load flow rate, a fuzzy control rule table is constructed, the fuzzy parameters are calculated, and the fuzzy control rules are summarized. According to the fuzzy control rules, sliding mode control based on the exponential approach rate is adopted to calculate the system control rate, correct the control amount of the system controller, and improve the control accuracy of the system. In addition, the present invention collects the excavator joint angle data through an angle sensor, calculates the linear displacement of the cylinder piston according to the conversion relationship between the joint angle and the linear displacement of the cylinder piston of the corresponding joint, and then calculates the joint load flow rate through the continuity equation and force balance equation of the valve-controlled hydraulic cylinder. Therefore, the system does not need to install a flow sensor when it is applied, which reduces the application cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 A schematic diagram of the installation position of the angle sensor in S1 and a schematic diagram of the key point setting position provided in an embodiment of the present invention;

[0053] Figure 2 A system control flow chart of a control method for an excavator hydraulic servo system based on fuzzy flow parameters provided by an embodiment of the present invention;

[0054] Figure 3 A data graph of the linear velocity of the boom joint cylinder piston collected when the excavator boom instruction 700 is provided in an embodiment of the present invention;

[0055] Figure 4This is a data graph of the linear velocity of the joint cylinder piston corresponding to the joint linkage when the excavator boom instruction 700, the dipper arm instruction 200, and the bucket instruction 300 are collected in accordance with the embodiment of the present invention. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] A control method for an excavator hydraulic servo system based on fuzzy flow parameters, comprising:

[0058] S1. Set key points, install angle sensors at the three joints of the excavator's boom, arm, and bucket, obtain absolute angle data of the three joints of the excavator, and calculate the joint angles based on the absolute angle data;

[0059] S2. Calculate the linear displacement of the cylinder piston of the corresponding joint according to the conversion relationship between the joint angle and the linear displacement of the joint cylinder piston;

[0060] S3. Calculate the load flow rate through the continuity equation and force balance equation of the valve-controlled hydraulic cylinder according to the joint angle and the linear displacement of the cylinder piston;

[0061] S4. Obtain the valve opening corresponding to different load flows, and summarize the fuzzy control rules according to the valve opening and load flow;

[0062] S5. Construct a multi-input multi-output MIMO model, calculate the system model parameters according to the fuzzy control rules, and correct the output control quantity of the system model;

[0063] S6. Perform sliding mode control on the excavator hydraulic servo system based on the output control quantity of the modified system model.

[0064] In S1, the key points are set to include the connection between the excavator body and the boom as point O, the connection between the boom hydraulic cylinder and the body as point A, the connection between the boom hydraulic cylinder and the boom as point B, the connection between the dipper arm hydraulic cylinder and the boom as point C, the connection between the dipper arm hydraulic cylinder and the dipper arm as point D, the connection between the boom and the dipper arm as point E, the connection between the bucket hydraulic cylinder and the dipper arm as point F, the connection between the bucket hydraulic cylinder and the rocker arm and the connecting rod as point I, the connection between the rocker arm and the dipper arm as point G, the connection between the connecting rod and the dipper arm as point J, the connection between the bucket and the dipper arm as point H, and the bucket tooth tip as point L;

[0065] Angle sensors are installed at the three joints of the excavator's boom, arm, and bucket. The angle sensor of the boom joint is parallel to BE, the angle sensor of the arm joint is parallel to EH, and the angle sensor of the bucket joint is parallel to GI. The data obtained by the angle sensor is the angle data between the three joints of the excavator's boom, arm, and bucket and the horizontal plane, which is the absolute angle data of the three joints of the excavator, recorded as θ 10 ,θ 20 ,θ 30 , construct the DH coordinate system, convert the absolute angle data of the three joints of the excavator according to the DH method, record the converted absolute angle data of the three joints of the excavator as θ1, θ2, and θ3 respectively, and calculate the joint angles of the three joints of the excavator according to the DH conversion angle data.

[0066] In S2, the conversion relationship between the excavator joint angle and the linear displacement of the joint cylinder piston is:

[0067]

[0068] ∠AOB=∠EOB+θ1+∠AOx;

[0069]

[0070] ∠CED=π-∠CEO-∠HED+θ2;

[0071]

[0072] ∠FGI=2π-∠FGE-∠EGH-∠HGI;

[0073] In the formula, x dB 、x dA 、x dBu are the linear displacements of the cylinder pistons corresponding to the three joints of the boom, the dipper arm, and the bucket, π is the flat angle, l OA , l OB are the distances from point O to point A and point B, ∠AOB and ∠EOB are the angles between the lines AO, EO and OB, ∠AOx is the angle between the line AO ​​and the horizontal direction x, l CE , l DE are the distances from point C and point D to point E, ∠CEO is the angle between the straight lines CE and ED, ∠CEO is the angle between the straight lines CE and EO, ∠HED is the angle between the straight lines HE and ED, l FG , l IGare the distances from point F and point I to point G, ∠FGI is the angle between the straight lines FG and GI, ∠FGE is the angle between the straight lines FG and GE, ∠EGH is the angle between the straight lines EG and GH, and ∠HGI is the angle between the straight lines HG and GI. Points A to L are the data points of the three joints of the excavator. The positions of the data are shown in the figure. Figure 1 As shown, the DH conversion angle data in S1 is differentiated to obtain the angular velocities of the three joints of the excavator. The distance between the excavator data points is calculated by combining the joint angles of the excavator and the lengths of the joint components.

[0074] In S3, the continuity equation of the valve-controlled hydraulic cylinder is:

[0075]

[0076] Where Q1 is the flow rate into the hydraulic cylinder, d() is the derivative, and x d is the linear displacement of the cylinder piston, dt is the time step, C i is the internal leakage coefficient, C e is the external leakage coefficient, C iL is the equivalent leakage coefficient, C es is the additional leakage coefficient, p1 and p2 are the oil pressures of the rodless and rod chambers of the hydraulic cylinder respectively, β e is the effective bulk elastic modulus, V1 is the volume of the rodless chamber of the hydraulic cylinder, is the first-order differential of the linear displacement of the cylinder piston; p L is the load pressure of the hydraulic cylinder, p s is the oil source pressure, is the equivalent volume, is the equivalent load pressure, n is the flow ratio, A1 and A2 are the piston areas of the rodless and rod chambers of the hydraulic cylinder respectively, Q L is the load flow, C d is the flow coefficient of the slide valve, ω is the area gradient of the slide valve, x v is the valve opening, and ρ is the pressure oil density.

[0077] In S3, the force balance equation is:

[0078]

[0079] In the formula, is the second-order differential of the linear displacement of the cylinder piston, M is the load mass, B p is the viscous damping coefficient, K is the elastic coefficient, F l is the external interference force;

[0080] According to the continuity equation and force balance equation of the valve-controlled hydraulic cylinder, the load flow is:

[0081]

[0082] K F It is a fuzzy parameter, which represents the influence degree between the three joints when the joints are linked. The maximum membership average method is used to calculate the fuzzy parameter. The fuzzy parameter is divided into five levels: very small influence VS, small influence S, medium influence M, large influence L, and very large influence VL.

[0083] In S4, the valve opening is divided into three levels: small opening SD, medium opening MD, and large opening LD. The handle command is input to one of the three joints of the excavator boom, dipper rod, and bucket respectively. According to the valve opening of the other two joints, the triangular membership function is constructed to calculate the joint membership corresponding to the different levels of valve opening of the other two joints. The fuzzy control algorithm Mamdani algorithm is used to calculate the fuzzy parameters of the input handle command joint according to the joint membership of the other two joints, summarize the fuzzy control rules, and construct a fuzzy control rule table. Taking the extension of the hydraulic cylinder of the excavator boom as an example, the handle command of the extension of the excavator boom is input, and the linear position x of the piston of the excavator boom shutdown cylinder is calculated. dB , collect the valve opening of the excavator arm and bucket, respectively recorded as x vA 、x vBu , take the triangular membership function, calculate the joint membership of the bucket and bucket of different levels, and the bucket membership is recorded as μ according to the valve level SA , μ MA , μ LA , the bucket membership is recorded as μ SBu , μ MBu , μ LBu , the fuzzy parameters are calculated according to the valve opening and joint membership, and are successively introduced into the load flow calculation equation to calculate the load Q of the excavator boom extension corresponding to different valve levels LB , construct the fuzzy control rule table, and the fuzzy control rule table corresponding to the excavator boom extension is shown in Table 1.

[0084] Table 1 Fuzzy control rules for excavator boom extension

[0085]

[0086] In the table, K FB is the fuzzy parameter corresponding to the excavator boom extension command, SD A ,MD A , LD A There are three levels of valve opening for the boom joint, SD Bu ,MD Bu , LD Buare the three levels of valve opening of the bucket joint, VS, S, M, L, and VL are the influence of the excavator arm and bucket on the excavator boom when the excavator boom is extended. It can be seen from Table 1 that x vA 、x vBu The larger the K F The larger the x vA 、x vBu Moderate, K F Moderate; x vA 、x vBu The smaller the K F According to the nine fuzzy control rules from VS (1) to VL (9), the output fuzzy quantity is calculated by the output fuzzy quantity calculation formula to obtain the fuzzy parameters.

[0087] The output fuzzy quantity calculation formula is: Output control quantity: U * is the sum of the output fuzzy quantities, j = 1, 2, 3…9 are the nine fuzzy control rules in the fuzzy control rule table, To obtain the union of the nine fuzzy control rules, For the larger-smaller synthesis method, R j is the implication relation of each fuzzy rule, () T represents the matrix transpose, is the membership degree of each fuzzy rule. The same applies to the boom retracted, the arm, and the bucket.

[0088] Construct a multiple-input multiple-output MIMO model and define the input matrix x and output matrix y as follows:

[0089]

[0090] In the formula, x i , i=1, 2, 3…9, represents the i-th input parameter of the system; represents the first-order differential of the i-th input parameter of the system; x dB 、x dA 、x dBu are the linear displacements of the cylinder pistons of the boom, arm, and bucket, respectively, v dB 、v dA 、v dBu are the linear displacement speeds of the cylinder pistons of the boom, dipper rod, and bucket, respectively, and a dB 、a dA 、a dBu are the linear displacement accelerations of the cylinder pistons of the boom, arm, and bucket, respectively; a 1m , m = 1, 2, 3, represents the nominal value of the mth sub-model of the system; a 2m , m = 1, 2, 3, represents the model parameters of the mth sub-model of the system; d m, m = 1, 2, 3, represents the external interference of the mth sub-model of the system; u m , m = 1, 2, 3, represents the control rate of the mth sub-model of the system, sgn() is the sign function. The system control model provided in the trial embodiment of the present invention includes 3 sub-models, a 21

[0091] In S6, the synovial surface s is:

[0092] s=C1e1+C2e2+e3;

[0093]

[0094] In the formula, C1>0, C2>0, C1 and C2 are error coefficients, e1 is tracking error, e2 and e3 are definition errors, are the first-order differentials of the linear displacements of the cylinder pistons of the boom, arm, and bucket, respectively. They are the second-order differentials of the linear displacements of the cylinder pistons corresponding to the three joints of the boom, arm, and bucket.

[0095] Differentiate the synovial surface s and get

[0096]

[0097] In the formula, is the first-order differential of the tracking error, is the first-order differential of the definition error, are the third-order differential values ​​of the linear displacement of the cylinder piston corresponding to the three joints of the boom, the dipper arm, and the bucket; g(x v ) m , m = 1, 2, 3, represents the output of the mth sub-model of the system, and g(x) is the system output; represents the first-order differential of the external disturbance force, u is the control rate of the system, x vB 、x vA 、x vBu They represent the valve openings corresponding to the three joints of the boom, arm and bucket respectively; a1 is the system nominal value matrix; a2 is the system model parameter matrix.

[0098] right Adopt sliding mode control based on exponential reaching rate:

[0099]

[0100] y=Cx+Du;

[0101] Where ε>0, k c >0, ε represents the control parameter, k crepresents the leakage coefficient, x is the input matrix, The first-order differential matrix of the input matrix, y is the output matrix, A is the input coefficient, B is the input control coefficient, C is the output coefficient, and D is the output control coefficient;

[0102] The control rate u of the system is:

[0103]

[0104] The initial control rate u of the system is obtained by inputting the preset trajectory. During the actual control process of the system, the fuzzy flow parameters are calculated in real time, and the control rate of the system is also updated in real time.

[0105] like Figure 1 The key points shown in the figure are set at the connection between the excavator body and the boom as point O, the connection between the boom hydraulic cylinder and the body as point A, the connection between the boom hydraulic cylinder and the boom as point B, the connection between the dipper arm hydraulic cylinder and the boom as point C, the connection between the dipper arm hydraulic cylinder and the dipper arm as point D, the connection between the boom and the dipper arm as point E, the connection between the bucket hydraulic cylinder and the dipper arm as point F, the connection between the bucket hydraulic cylinder and the rocker arm and the connecting rod as point I, the connection between the rocker arm and the dipper arm as point G, the connection between the connecting rod and the dipper arm as point J, the connection between the bucket and the dipper arm as point H, and the tip of the bucket tooth as point L. Angle sensors are installed at the three joints of the excavator boom, dipper arm, and bucket. The angle sensor of the boom joint is parallel to BE, the angle sensor of the dipper arm joint is parallel to EH, and the angle sensor of the bucket joint is parallel to GI. The angles between the three joints of the excavator boom, dipper arm, and bucket and the horizontal direction are collected by the angle sensors to obtain the absolute angle data of the three joints. The absolute angle data of the three joints of the excavator boom, dipper arm, and bucket are recorded as θ respectively. 10 ,θ 20 ,θ 30 , construct the kinematic coordinate system DH coordinate system, recorded as θ1, θ2, θ3 respectively, and calculate the joint angle of the excavator according to the DH conversion angle data. Perform differential calculation on the DH conversion angle data to obtain the joint angular velocity of the three joints of the excavator. Combine the joint angle of the excavator and the length of the joint component to calculate the distance between the data points of the three joints of the excavator. According to the conversion relationship between the joint angle of the excavator and the linear displacement of the joint cylinder piston in S2, calculate the linear displacement of the cylinder piston of the three joints of the excavator. Substitute the linear displacement of the cylinder piston of the three joints of the excavator into the continuity equation of the valve-controlled hydraulic cylinder in S3 respectively, and the flow into the corresponding joint hydraulic cylinder can be obtained, and then the load flow of the joint can be obtained.

[0106] Figure 2A system control flow chart of an excavator hydraulic servo system control method based on fuzzy flow parameters provided in an embodiment of the present invention. After the excavator is started, the system starts to work, reads the input preset trajectory, obtains the system initial control rate u according to the input preset trajectory, and performs synovial control on the excavator hydraulic servo system. During the control process, the system calculates the joint angle according to the DH method based on the data collected by the angle sensor, calculates the load flow through the continuity equation and the force balance equation of the valve-controlled hydraulic cylinder, and calculates the load flow of the three joints of the excavator in real time to determine whether the flow limit is exceeded. If it is monitored that the flow limit is exceeded, fuzzy flow calculation of each joint is performed, fuzzy rules are summarized, and model parameters are modified. If it is not exceeded, the model parameters corresponding to the input preset trajectory are used as system model parameters to control the system and detect whether the end point has been reached. If not, a new round of synovial control is started. If it has been reached, the system ends control.

[0107] Figure 3 The data diagram of the linear velocity of the boom joint cylinder piston collected when the excavator boom instruction 700 is provided in an embodiment of the present invention, Figure 4 The data diagram of the linear velocity of the joint oil cylinder piston corresponding to the joint linkage when the excavator boom instruction 700, the dipper arm instruction 200, and the bucket instruction 300 provided in the embodiment of the present invention are collected. Through the continuity equation of the valve-controlled hydraulic cylinder, it can be known that the greater the linear displacement of the oil cylinder piston, the greater the flow rate flowing into the hydraulic cylinder, and the greater the load flow of the corresponding joint. Figure 3 and Figure 4 The linear velocity of the oil cylinder piston is the linear displacement velocity of the oil cylinder piston, where the “-” sign only indicates the direction of the linear displacement velocity of the oil cylinder piston, not the magnitude. The magnitude of the linear displacement velocity of the oil cylinder piston is the magnitude of the absolute value of the linear velocity of the oil cylinder piston. The magnitude of the absolute value of the linear displacement velocity of the oil cylinder piston can directly reflect the linear displacement magnitude of the oil cylinder piston of the corresponding joint at the current moment, and further reflect the magnitude of the load flow of the corresponding joint at the current moment, that is, the greater the linear velocity of the oil cylinder piston, the greater the load flow of the corresponding joint. By comparison Figure 3 and Figure 4 It can be seen that when the excavator boom command is 700, the linear displacement speed of the cylinder piston of the excavator boom joint when there is joint linkage ( Figure 4 ) is significantly smaller than the linear displacement speed of the cylinder piston of the excavator boom joint when there is no joint linkage ( Figure 3 ), therefore, in the joint linkage of the excavator boom instruction 700, the dipper arm instruction 200, and the bucket instruction 300, the sum of the flow rates of the three joints of the excavator boom, dipper arm and bucket exceeds the maximum value, resulting in a reduction in the flow rate entering each joint. It is necessary to calculate the fuzzy flow parameters and adjust the system control amount.

[0108] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A control method for an excavator hydraulic servo system based on fuzzy flow parameters, characterized in that: include: S1. Set key points, install angle sensors at the three joints of the excavator's boom, arm, and bucket, obtain absolute angle data of the three joints of the excavator, and calculate the joint angles based on the absolute angle data; S2. Calculate the linear displacement of the cylinder piston of the corresponding joint according to the conversion relationship between the joint angle and the linear displacement of the joint cylinder piston; S3. Calculate the load flow rate through the continuity equation and force balance equation of the valve-controlled hydraulic cylinder according to the joint angle and the linear displacement of the cylinder piston; S4. Obtain the valve opening corresponding to different load flows, and summarize the fuzzy control rules according to the valve opening and load flow; S5. Construct a multi-input multi-output MIMO model, calculate the system model parameters according to the fuzzy control rules, and correct the output control quantity of the system model; S6. Perform sliding mode control on the excavator hydraulic servo system based on the output control quantity of the modified system model.

2. The control method of an excavator hydraulic servo system based on fuzzy flow parameters according to claim 1 is characterized in that: In S1, the key points are set to include the connection between the excavator body and the boom as point O, the connection between the boom hydraulic cylinder and the body as point A, the connection between the boom hydraulic cylinder and the boom as point B, the connection between the dipper arm hydraulic cylinder and the boom as point C, the connection between the dipper arm hydraulic cylinder and the dipper arm as point D, the connection between the boom and the dipper arm as point E, the connection between the bucket hydraulic cylinder and the dipper arm as point F, the connection between the bucket hydraulic cylinder and the rocker arm and the connecting rod as point I, the connection between the rocker arm and the dipper arm as point G, the connection between the connecting rod and the dipper arm as point J, the connection between the bucket and the dipper arm as point H, and the bucket tooth tip as point L; Angle sensors are installed at the three joints of the excavator's boom, arm, and bucket. The angle sensor of the boom joint is parallel to BE, the angle sensor of the arm joint is parallel to EH, and the angle sensor of the bucket joint is parallel to GI. The data obtained by the angle sensor is the angle data between the three joints of the excavator's boom, arm, and bucket and the horizontal plane, which is the absolute angle data of the three joints of the excavator, recorded as θ 10 ,θ 20 ,θ 30 , construct the DH coordinate system, convert the absolute angle data of the three joints of the excavator according to the DH method, record the converted absolute angle data of the three joints of the excavator as θ1, θ2, and θ3 respectively, and calculate the joint angles of the three joints of the excavator according to the DH conversion angle data.

3. The control method of an excavator hydraulic servo system based on fuzzy flow parameters according to claim 2 is characterized in that: In S2, the conversion relationship between the excavator joint angle and the linear displacement of the joint cylinder piston is: ∠AOB=∠EOB+θ1+∠AOx; ∠CED=π-∠CEO-∠HED+θ2; ∠FGI=2π-∠FGE-∠EGH-∠HGI; In the formula, x dB 、x dA 、x dBu are the linear displacements of the cylinder pistons corresponding to the three joints of the boom, the dipper arm, and the bucket, π is the flat angle, l OA , l OB are the distances from point O to point A and point B, ∠AOB and ∠EOB are the angles between the lines AO, EO and OB, ∠AOx is the angle between the line AO ​​and the horizontal direction x, l CE , l DE are the distances from point C and point D to point E, ∠CED is the angle between the straight lines CE and ED, ∠CEO is the angle between the straight lines CE and EO, ∠HED is the angle between the straight lines HE and ED, l FG , l IG are the distances from point F and point I to point G respectively, ∠FGI is the angle between the straight lines FG and GI, ∠FGE is the angle between the straight lines FG and GE, ∠EGH is the angle between the straight lines EG and GH, and ∠HGI is the angle between the straight lines HG and GI.

4. The control method of an excavator hydraulic servo system based on fuzzy flow parameters according to claim 3 is characterized in that: In S3, the continuity equation of the valve-controlled hydraulic cylinder is: p L =p1-np2; Where Q1 is the flow rate into the hydraulic cylinder, d() is the derivative, and x d is the linear displacement of the cylinder piston, dt is the time step, C i is the internal leakage coefficient, C e is the external leakage coefficient, C iL is the equivalent leakage coefficient, C es is the additional leakage coefficient, p1 and p2 are the oil pressures of the rodless and rod chambers of the hydraulic cylinder respectively, β e is the effective bulk elastic modulus, V1 is the volume of the rodless chamber of the hydraulic cylinder, is the first-order differential of the linear displacement of the cylinder piston; p L is the load pressure of the hydraulic cylinder, p s is the oil source pressure, is the equivalent volume, is the equivalent load pressure, n is the flow ratio, A1 and A2 are the piston areas of the rodless and rod chambers of the hydraulic cylinder respectively, Q L is the load flow, C d is the flow coefficient of the slide valve, ω is the area gradient of the slide valve, x v is the valve opening, and ρ is the pressure oil density.

5. The control method of an excavator hydraulic servo system based on fuzzy flow parameters according to claim 4 is characterized in that: In S3, the force balance equation is: In the formula, is the second-order differential of the linear displacement of the cylinder piston, M is the load mass, B p is the viscous damping coefficient, K is the elastic coefficient, F l is the external interference force; According to the continuity equation and force balance equation of the valve-controlled hydraulic cylinder, the load flow is: K F It is a fuzzy parameter, which represents the influence degree between the three joints when the joints are linked. The maximum membership average method is used to calculate the fuzzy parameter. The fuzzy parameter is divided into five levels: very small influence VS, small influence S, medium influence M, large influence L, and very large influence VL.

6. The control method of an excavator hydraulic servo system based on fuzzy flow parameters according to claim 5, characterized in that: In S4, the valve opening is divided into three levels: small opening SD, medium opening MD, and large opening LD. The handle command is input to one of the three joints of the excavator boom, dipper arm, and bucket respectively. According to the valve opening of the other two joints, the triangular membership function is constructed, and the joint membership corresponding to the different levels of valve opening of the other two joints is calculated. The fuzzy control algorithm Mamdani algorithm is used to calculate the fuzzy parameters of the input handle command joint according to the joint membership of the other two joints, summarize the fuzzy control rules, and construct a fuzzy control rule table.

7. The control method of an excavator hydraulic servo system based on fuzzy flow parameters according to claim 6 is characterized in that: Construct a multiple-input multiple-output MIMO model and define the input matrix x and output matrix y as follows: In the formula, x i , i=1, 2, 3…9, represents the i-th input parameter of the system; represents the first-order differential of the i-th input parameter of the system; x dB 、x dA 、x dBu are the linear displacements of the cylinder pistons of the boom, arm, and bucket, respectively, v dB 、v dA 、v dBu are the linear displacement speeds of the cylinder pistons of the boom, dipper rod, and bucket, respectively, dB 、a dA 、a dBu are the linear displacement accelerations of the cylinder pistons of the boom, dipper arm, and bucket, respectively; a 1m , m = 1, 2, 3, represents the nominal value of the mth sub-model of the system; a 2m , m = 1, 2, 3, represents the model parameters of the mth sub-model of the system; d m , m = 1, 2, 3, represents the external interference of the mth sub-model of the system; u m , m = 1, 2, 3, represents the control rate of the mth sub-model of the system, and sgn( ) is the sign function.

8. The control method of an excavator hydraulic servo system based on fuzzy flow parameters according to claim 7 is characterized in that: In S6, the synovial surface s is: s=C1e1+C2e2+e3; In the formula, C1>0, C2>0, C1 and C2 are error coefficients, e1 is tracking error, e2 and e3 are definition errors, are the first-order differentials of the linear displacements of the cylinder pistons of the boom, arm, and bucket, respectively. They are the second-order differentials of the linear displacements of the cylinder pistons corresponding to the three joints of the boom, arm, and bucket.

9. The control method of an excavator hydraulic servo system based on fuzzy flow parameters according to claim 8, characterized in that: Differentiate the synovial surface s and get In the formula, is the first-order differential of the tracking error, is the first-order differential of the definition error, are the third-order differential values ​​of the linear displacement of the cylinder piston corresponding to the three joints of the boom, the dipper arm, and the bucket; g(x v ) m , m = 1, 2, 3, represents the output of the mth sub-model of the system, and g(x) is the system output; represents the first-order differential of the external disturbance force, u is the control rate of the system, x vB 、x vA 、x vBu They represent the valve openings corresponding to the three joints of the boom, arm and bucket respectively; a1 is the system nominal value matrix; a2 is the system model parameter matrix.

10. The control method of an excavator hydraulic servo system based on fuzzy flow parameters according to claim 9, characterized in that: right Adopt sliding mode control based on exponential reaching rate: y′=Cx+Du; Where ε>0, k c >0, ε represents the control parameter, k c represents the leakage coefficient, x is the input matrix, The first-order differential matrix of the input matrix, y is the output matrix, A is the input coefficient, B is the input control coefficient, C is the output coefficient, and D is the output control coefficient; The control rate u of the system is: The initial control rate u of the system is obtained by inputting the preset trajectory. During the actual control process of the system, the fuzzy flow parameters are calculated in real time, and the control rate of the system is also updated in real time.

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