A walking excavator direction correction method

Abstract

The application discloses a walking excavator direction correction method during a process of loading a vehicle, which is used for realizing direction position adjustment in front of a walking excavator to meet parameter requirements of loading a vehicle. The method comprises the following steps: setting a posture parameter sensor to obtain a posture of the walking excavator; establishing a kinematics and mechanics model of the walking excavator; establishing a two-stage optimization model of a direction correction control parameter; and performing posture control parameter planning calculation by using a microprocessor. The application can replace a common adjustment mode of manual operation, repeated reversing, steering and advancing in front of the walking excavator during loading the vehicle, so as to improve efficiency, reduce equipment operation difficulty and reduce requirements on a space of a site.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of direction adjustment of walking excavator, in particular to a walking excavator direction deviation rectification method. BACKGROUND

[0002] The walking excavator is a special engineering machinery suitable for plateau and mountain operation, mainly composed of walking working device 2, rotating platform 3 and chassis 4. The walking chassis 4 is a multi-degree-of-freedom structure system connected by multiple joints, legs and wheels. The four walking legs cooperate with the working device 2 with telescopic function, which is equivalent to a walking mechanism with five legs, so that the walking excavator has special functions such as obstacle crossing, climbing, wading and crossing trench, and can walk and work in complex terrain environment.

[0003] Due to the low speed of the walking excavator, special vehicles are generally used for long-distance transportation. During the self-transportation of the walking excavator 1, it needs to be centered and positioned. Due to the long wheelbase and large turning radius of the walking excavator, if the method of repeatedly reversing, turning and advancing is adopted, a large space is needed behind the transport vehicle to complete the direction adjustment, which is complex to control and requires high operation experience and long time. SUMMARY

[0004] The purpose of the present application is to provide a walking excavator direction deviation rectification method, which adopts a walking excavator working device to assist in rectification and control, so as to realize direction deviation rectification and shorten the direction position rectification time.

[0005] The technical solution for achieving the purpose of the present application is:

[0006] A walking excavator direction deviation rectification method, comprising:

[0007] A ranging sensor is arranged at the center point o1 of the rotating platform of the walking excavator to obtain the spatial position of the rotating platform center o1 point relative to the transport vehicle;

[0008] A rotation angle sensor relative to the initial position is arranged at the center point o1 of the rotating platform to measure the rotation angle and speed of the rotating platform relative to the chassis, the swing angle γ of the working device and the angle at which the chassis swings relative to the axis of the rotating platform;

[0009] A ranging sensor is arranged at the center point o1 of the rotating platform to obtain the spatial position of the rotating platform center o1 point relative to the transport vehicle;

[0010] Manipulate the walking excavator, make the initial position of the walking excavator consistent with the optimization parameter result according to the sensor feedback value, and make the slewing platform rotate at the rotation speed in the optimization model until the walking excavator chassis rotates to the optimization value of the swing angle alpha relative to the slewing platform.

[0011] The three optimization objectives are that the walking excavator slewing platform center point o1 position coincides with the longitudinal axis of the transport vehicle, and the two front wheel support points A and B are respectively symmetrically located on both sides of the longitudinal axis. The constraint condition is that the initial positions of the support points A and B are located on both sides of the longitudinal axis, and the approach angle is less than a certain angle. Therefore, the following multi-objective optimization model is constructed:

[0012]

[0013] s.t. lambda < lambda0, A y > 0, B y < 0

[0014] In the formula: w1, w2 and w3 are weight coefficients of the three optimization objectives, o 1y , A y , B y are the longitudinal coordinates of the two front wheel support points A and B in the first base coordinate system {w0}-x0o0y0; lambda0 is the upper limit value of the approach angle lambda; o 1y , A y , B y are the slewing platform center point o1, l2 is the length of the left front wheel support point A and the slewing platform center o1 point, and beta is the included angle between the two front wheel support points A and B and the slewing platform center o1 point.

[0015] The first base coordinate system {w0}-x0o0y0 takes the midpoint o0 of the ground projection of the rear end of the transport vehicle as the coordinate origin, the x0 axis direction is horizontal backward along the longitudinal axis of the transport vehicle, and the y0 axis direction is counterclockwise rotation of 90° in the x0 axis direction.

[0016] Compared with the prior art, the present application has the following advantages:

[0017] (1) The walking excavator direction correction control parameter optimization model established by the present application can determine the initial position parameters of the walking excavator before direction adjustment according to the current different angle lambda between the walking excavator and the longitudinal axis of the transport vehicle, guide the equipment operator, and display the walking excavator posture and spatial position parameters in real time through the sensor, thereby reducing the difficulty of equipment operation and improving the safety of equipment operation, and avoiding the risk caused by equipment misoperation.

[0018] (2) the calculation result shows that the method can realize the adjustment of the walking excavator and the transport vehicle longitudinal axis angle of no less than 20° per time, and when the walking excavator and the transport vehicle longitudinal axis angle is less than 25°, the direction adjustment can be completed through one direction correction operation, which greatly reduces the direction adjustment process and time compared with the background technology.

[0019] (3) the walking excavator direction correction process of the present application adopts the bucket to support the two rear wheels, realizes the three-point support of the bucket and the two front wheels, makes the two front wheels slide along the ground, rotates around the bucket, and adjusts the direction, which does not involve the process of repeatedly reversing, turning and advancing, and has smaller requirement for the space. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 the flow chart of the method of the present application is shown.

[0021] Figure 2a 、 Figure 2b 、 Figure 2c 、 Figure 2d the front posture adjustment top view of the transport vehicle on the walking excavator.

[0022] Figure 3 the front posture adjustment side view of the transport vehicle on the walking excavator.

[0023] Figure 4 the steering kinematic model diagram of the walking excavator.

[0024] Figure 5 the force diagram of the whole mechanism of the walking excavator.

[0025] Figure 6 the force diagram of the working device of the walking excavator.

[0026] Figure 7 the force diagram of the chassis of the walking excavator.

[0027] Figure 8 the optimization target and the angle deviation curve diagram of the walking excavator and the transport vehicle after adjustment.

[0028] Figure 9 the longitudinal coordinate optimization result diagram of o1, A and B points corresponding to different approach angles. DETAILED DESCRIPTION

[0029] The present application will be further described below in combination with the drawings and specific embodiments.

[0030] The walking excavator direction correction method of the present application combines Figure 1 , including the following steps:

[0031] Step 1, set up sensor and controller: get the spatial attitude parameters of walking excavator and the relative position parameters of transport vehicle;

[0032] 1.1, set up distance measuring sensor S1 at the center point o1 of the walking excavator rotating platform 3, and connect the distance measuring sensor S1 with the controller by wire, as shown in Figure 2c and Figure 3 , set up distance measuring reference points R1, R2 and R3 at the left upper, middle lower and right upper sides of the rear side of the transport vehicle 1 respectively. By measuring the distance between the distance measuring sensor S1 and the distance measuring reference points R1, R2 and R3, the spatial position of the center o1 point of the rotating platform 3 relative to the transport vehicle 1 can be obtained, and further the distance h of the walking excavator across the longitudinal axis of the transport vehicle 1 can be obtained.

[0033] 1.2, as shown in Figure 3 , set up distance measuring reference point R4 at the point where the bucket 9 of the working device 2 contacts the ground, and by measuring the distance between the distance measuring sensor S1 and R4, the arm length l of the excavating working device can be further obtained. x

[0034] 1.3, set up the rotation angle sensor S2 relative to the initial position at the center point o1 of the rotating platform 3, and connect the rotation angle sensor S2 with the controller by wire, which is used to measure the rotation angle and speed of the rotating platform 3 relative to the chassis 4, the swing angle γ of the working device 2 and the angle α at the moment when the chassis 4 swings relative to the axis of the rotating platform 3.

[0035] 1.4, set up distance measuring sensor S3 at the middle axis position of the rear side of the chassis 4, and by measuring the distance between the distance measuring sensor S3 and R1, R2 and R3, the position of the distance measuring sensor S3 relative to the transport vehicle 1 can be obtained, combined with the distance between the distance measuring sensor S1 and the distance measuring reference points R1, R2 and R3, the position of the center point o1 of the rotating platform 3 relative to the transport vehicle 1 can be obtained. Further, the included angle λ of the longitudinal axis of the chassis 4 of the walking excavator and the axis of the transport vehicle 1 can be obtained.

[0036] Step 2, establish the spatial kinematics and mechanics model of the walking excavator

[0037] 2.1, establish the kinematics relationship

[0038] Figure 4 is the kinematics model when the walking excavator turns, wherein C point is the position of the bucket 9 of the working device 2 in the excavating driving state, P point is the hinge point position between the excavating working device 2 and the rotating platform 3, A and B points are respectively the contact points of the two front wheels (left 5 and right 6) and the ground, o1 point is the center of the excavator chassis rotating platform 3, and o point is the support point position of the bucket 9 after the working device 2 rotates by an angle γ. x ​and l2 are the length of the excavating working device 2 arm span CP and the distance from the center o1 of the slewing platform 3 to the A point or B point respectively; m1, m2 and m3 are the mass of the excavating working device 2, the slewing platform 3 and the chassis 4 respectively; the angle between the line connecting the two front wheels (left 5, right 6) and the center o1 of the slewing platform 3 is β.

[0039] For the convenience of analysis, the steering process of the walking excavator can be simplified as a two-dimensional motion with the ground as the plane, a first base coordinate system {w0}-x0o0y0 is established with the midpoint o0 of the ground projection of the rear end of the transport vehicle 1 as the coordinate origin, a second base coordinate system {w}-xoy is established with the support point o of the bucket 9 of the working device 2 as the coordinate origin, and a third base coordinate system {w1}-x1o1y1 is established with the center o1 point of the slewing of the chassis 4 as the coordinate origin. The coordinate axis directions are shown in Figure 4 Fig. 1, the x0 axis direction is horizontally backward along the longitudinal axis of the transport vehicle, the x axis points to the P point along the ground support point o of the bucket 9, the x1 axis points to the front wheel direction along the longitudinal axis of the chassis 4 of the walking excavator, and the y0, y, y1 axes are rotated counterclockwise by 90° in the x0, x, x1 axis directions respectively. Before the direction correction, the x direction distance d and the y direction distance h of the slewing center o1 relative to the midpoint o0 of the rear end of the transport vehicle, the rotation angle γ and the included angle λ between the longitudinal axis of the excavator and the axis of the transport vehicle 1 are measured by the sensor, so as to determine the initial position relationship of the second base coordinate system {w}-xoy origin relative to the first base coordinate system {w0}-x0o0y0 origin and the third base coordinate system {w1}-x1o1y1 relative to the first base coordinate system {w}-xoy.

[0040] Let θ0 be the rotation angle of the second base coordinate system {w}-xoy origin relative to the first base coordinate system {w0}-x0o0y0 origin, is the coordinate of the o point in the first base coordinate system {w0}-x0o0y0; let θ 01 is the rotation angle of the third base coordinate system {w1}-x1o1y1 relative to the second base coordinate system {w}-xoy, w o 1x , w o 1y is the coordinate of the o1 point in the second base coordinate system {w}-xoy. By using the Denavit and Hartenberg method, the posture conversion matrix between each mechanism during the steering of the walking excavator can be established as

[0041]

[0042] In the formula (1), (2) The transformation matrix of the second base coordinate system {w}-xoy relative to the first base coordinate system {w0}-x0o0y0 and the transformation matrix of the third base coordinate system {w1}-x1o1y1 relative to the second base coordinate system {w}-xoy, respectively.

[0043] The coordinate vectors of the points P, o1, A and B in the first base coordinate system {w0}-x0o0y0 are represented by vectors w w The coordinate vectors of the points P and o1 in the second base coordinate system {w}-xoy are represented by vectors

[0044]

[0045] Similarly, the coordinate vectors of the working device 2, the slewing platform 3 and the chassis 4 in the first base coordinate system {w0}-x0o0y0 are obtained, and the positional relationship between the motion mechanisms in the direction correction process is further obtained.

[0046] 2.2 Establishment of a mechanical model

[0047] In the direction correction process of the excavator, the motion can be simplified as uniform motion, and the speed is slow. The two-degree-of-freedom motion mechanism can be simplified as a static mechanical model at each moment. The force diagram of the entire mechanism is shown in Figure 5

[0048] 2.2.1 Determination of the direction of friction

[0049] The motion of the point A in the front wheel (left 5) is a compound motion around the point o and the point o1. The direction of the sliding friction of the point A is mainly caused by the compound motion speed v A A The direction of the friction f A of the point A is opposite to the direction of the speed v

[0050] The absolute speed of the point A is the resultant of the relative angular speed ω1 around the point o and the relative angular speed ω2 around the point o1, and is

[0051]

[0052] ​​​​​​Where ω1 is the angular velocity of the working device 2 relative to the point o of the bucket 9, the angle of deflection of the straight line ool relative to the x0 axis is denoted by θ1, and ω1 = dθ1 / dt, t is time; ω2 is the driving angular velocity of the motor of the slewing platform 3, as shown in Figure 5 Figure, the angle of oscillation of the chassis 4 relative to the slewing platform 3 is denoted by α, and ω2 = dα / dt, which is a known variable; l o1A is the length of the member o1A; the distance between the point o of the support point of the bucket 9 and the point A of the front wheel (left 5), where l1 is the length of the member ool, and l2 = l o1A is the length of the member o1A, and β is the included angle between the member o1A and the member o1B, which is a constant.

[0053] It is easy to obtain that the included angle between the lines oA and o1A is

[0054]

[0055] The included angle between the lines oB and o1B is

[0056]

[0057] Where is the distance between the point o of the support point of the bucket 9 and the point B of the front wheel (right 6).

[0058] Let τ1 = ∠oAo1 and τ2 = ∠oBo1, and in numerical values, it can be obtained from equation (7) that

[0059] v A 2 = v A1 2 + v A2 2 - 2v A1 v A2 cosτ1 (10)

[0060] Where v A1 = l oA · dθ1 / dt, and v A2 = l2· dα / dt, which are the decomposed velocities of the velocity of the point A in the vertical directions of oA and o1A, respectively.

[0061] Again, using v A2 2 = v A 2 + v A1 2 - 2v A v A1 cosθ2, the angle θ2 between the velocities v A and v A1 can be obtained, that is,

[0062]

[0063] Thus the velocity v A The direction of the front wheel (left 5) friction force f A The direction of v A is opposite to the direction of v

[0064] Similarly, the velocity of point B is v

[0065] v B 2 = v B1 2 + v B2 2 - 2v B1 v B2 cos τ2 (12)

[0066] where v B1 = l oB · dθ1 / dt, v B2 = l2· dα / dt are the decomposed velocities of the velocity of point B in the vertical direction of oB and o1B respectively.

[0067] Again, v B2 2 = v B 2 + v B1 2 - 2v B v B1 cos θ3 can be obtained, and the angle θ3 between v B and v B1 is θ3 = arccos (v B / v B ).

[0068]

[0069] Thus the velocity v B The direction of the front wheel (right 6) friction force f B The direction of v B is opposite to the direction of v

[0070] In addition, A and B are symmetrical structures relative to point o1, and in numerical value, v B2 = v A2 .

[0071] From the above analysis, it can be seen that, in formula (12) and formula (13), except θ1, are unknown variables, other parameters are known.

[0072] 2.2.2 Normal pressure calculation

[0073] Using the moment balance condition, the normal pressures of points A, B and o are respectively

[0074]

[0075] N o = T3 - N A = N B (16)

[0076] wherein: T1 = g(m1x1 + m2x2 + m3x3), T2 = g(m1y1 + m2y2 + m3y3), T3 = (m1 + m2 + m3)g, T4 = (x A - x0)(y B - y0) - (y A - y0)(x B - x0), wherein (x i , y i ) are the mass center coordinates of the masses m i (i = 1,... 3) in the first base coordinate system {w0} - x0o0y0, (x0, y0), (x A , y A ) and (x B , y B ) are the coordinates of the points o, A, B in the first base coordinate system {w0} - x0o0y0, and g is the acceleration due to gravity.

[0077] 2.2.3 Mechanical analysis

[0078] Taking the component ooi as the research object, Figure 6 using horizontal force balance ∑X = 0, vertical force balance ∑Y = 0, and o point moment balance ∑M o = 0, we have

[0079]

[0080] wherein: F ox , F oy are the forces of the support point o in the x0, y0 axis direction of the first base coordinate system {w0}; are the forces of the hinge point oi in the x0, y0 axis direction of the first base coordinate system {w0}; is the moment of the rotary platform 3 applied to the working device 2; M o is the moment of the rotary friction force acting on the excavator bucket 9.

[0081] Taking the component o1AB as the research object, Figure 7 using horizontal force balance ∑X = 0, vertical force balance ∑Y = 0, and o1 point moment balance we have

[0082]

[0083] where φ A , φ B are the angles between f A and f B and the positive direction of x-axis, respectively, and φ A = -π / 2 - θ1- θ2- τ1+ α+ β, φ B = -π / 2 - θ1+ α+ τ2+ θ3; ψ1 is the angle between f A and the connecting rod o1A, ψ1= 3π / 2 - τ1- θ2, ψ2 is the angle between f B and the connecting rod o1B, ψ2= -π / 2 + τ2+ θ3. are the reaction forces of o1A and o1B, respectively; are the reaction torques of o1A and o1B, respectively.

[0084] Taking the whole mechanism as the research object, Figure 5 the moment balance ∑M o = 0 at o is used, and there are

[0085]

[0086] Using formula (17), (18), (20), (21) and the relationship there are

[0087] F ox = -f A cosφ A -f B cosφ B (24)

[0088] F oy = -f A sinφ A -f B sinφ B (25)

[0089] From formula (19), (22), (24) and (25), using the relationship there are

[0090] F ox l1sinθ1+F oy l1cosθ1-M o = -f A l2sinψ1-f B l2sinψ2 (26)

[0091] Further simplification is

[0092] l1f​​A cos(a + b - 02 - ti) + li f B cos(03 + t2 + a) - M o = f A l2 cos(t1 + 02) + f B l2 cos(t2 + 03) (27)

[0093] where f A = μN A , f B = μN B , μ is the friction coefficient.

[0094] From equation (11) and equation (13), it can be seen that θ2 and θ3 are related to , in addition to θ1, which is an unknown variable, others are known parameters, in which is a known value, therefore, equation (23) and equation (27) can be regarded as a first-order differential equation group, that is

[0095]

[0096] θ1(t), a(t), respectively represent θ1 angle and its first-order differential angular velocity, angle a and its first-order differential angular velocity at different t time; respectively represent θ1(t), a(t), satisfy equation (23) and equation (27).

[0097] Equation (28) can be regarded as the constraint equation of a two-degree-of-freedom motion mechanism, which is a first-order implicit differential equation group.

[0098] Step 3, establishing a direction correction control parameter optimization model

[0099] In order to obtain the control parameters of the walking excavator when correcting the direction, it is necessary to solve the ordinary differential equation group of equation (28) first. Since the control equation is an ordinary differential equation group, a first-order optimization model is constructed to solve it. Then, a second-order optimization model is constructed to optimize the direction correction control parameters.

[0100] 3.1 Kinematics parameter solving

[0101] Firstly, the Euler method is used to convert equation (28) into a difference equation, and the principle is

[0102] θ1(t n+1 ) = θ1(t n ) + hf(t n , θ1(t n)) (n = 0, 1, 2,..., N) (29)

[0103] where t n represents the time of the nth node, N represents the total number of nodes; θ1(t n ) represents the value of θ1 at t n ; θ1(t n+1 ) represents the value of θ1 at t n+1 ; h = t n+1 - t n is the time step; f(t n , θ1(t n )) represents the differential value of θ1 with respect to time at t n ; using the above formula, θ1(t1), θ1(t2),..., θ1(t n ) can be calculated step by step from the known θ1(t0).

[0104]

[0105] In this way, the entire time period is divided into several time intervals, and in each time interval, formula (29) and (30) are used to discretize formula (28) into several algebraic equations, and it is difficult to obtain a numerical solution. Therefore, an optimization method is used to solve it.

[0106] For each time t n , a state optimization model is constructed to solve θ1(t n ) at each time as the optimization variable, to satisfy formula (27) as the optimization objective, and to satisfy formula (23) and the support point reaction force of A and B greater than zero as the constraint condition optimization model, that is,

[0107]

[0108] In the formula: α(t n ) represents the value of α at t n ; represents the differential value of α with respect to time at t n .

[0109] Using the optimization method to solve the above formula, the change rule of θ1(t n ) with respect to time t n can be obtained, and the change of various parameters of the walking excavator during steering can be obtained.

[0110] 3.2 Control parameter solving optimization model

[0111] ​The first-order optimization model gives the variation of the working device 2 and the chassis 4 with time under a certain initial condition of the walking excavator. In engineering, the goal of one-time direction correction is achieved by changing the initial state parameters of the walking excavator.

[0112] When the walking excavator approaches at an angle of deviation from the longitudinal axis λ of the transport vehicle 1, the distance h across the longitudinal axis, the swing angle γ of the working device 2, and the arm length l of the working device 2 x The three variables can determine the spatial relative position of the walking excavator at the starting time of direction correction and the transport vehicle 1, and the swing angle α of the chassis 4 relative to the axis of the slewing platform 3 at the end time can control when the direction correction ends. The swing angle value at the end time is α'. In this paper, the above four variables are selected as the optimization design variables to achieve one-time direction correction of the walking excavator.

[0113] The three optimization objectives are: the center point o1 of the slewing platform 3 of the walking excavator is coincident with the longitudinal axis of the transport vehicle 1; and the support points A and B of the two front wheels (left 5 and right 6) are symmetrically located on both sides of the longitudinal axis. The constraint conditions are that the initial positions of the support points A and B are located on both sides of the longitudinal axis, and the approach angle is less than a certain angle. Therefore, the following multi-objective optimization model is constructed:

[0114]

[0115] s.t.λ<λ0,A y >0,B y <0

[0116] In the formula, w1, w2, and w3 are weight coefficients of the three optimization objectives, The weight coefficients can be determined according to the requirements; o 1y , A y , B y are the longitudinal coordinates of the center point o1 of the slewing platform 3, the support points A and B in the first base coordinate system {w0}-x0o0y0; λ0 is the upper limit value of the approach angle, which is related to the structure of the walking excavator. The above formula is solved by using the step-by-step quadratic programming method to obtain the control parameters of the walking excavator for one-time direction correction under different approach angles.

[0117] The first-order optimization model is the basis of the second-order optimization model, and the second-order optimization model mainly optimizes the initial conditions of the first-order optimization model to obtain the corresponding direction correction control parameters.

[0118] Step 4, direction correction scheme of the walking excavator

[0119] Combined Figure 1 with the flowchart of the direction correction method of the walking excavator, the direction correction scheme of the walking excavator is as follows.

[0120] 4.1, when the walking excavator is self-transported to the transport vehicle 1, first, the rear wheels are directed towards the transport vehicle 1( Figure 2a ), and the angle λ between the axis of the chassis 4 and the longitudinal axis of the transport vehicle 1 is obtained by the distance measuring sensors S1, S3 set in step 1.

[0121] 4.2, the distance h of the walking excavator across the longitudinal axis of the transport vehicle 1, the swing angle γ of the working device 2, the arm length l of the excavating working device 2, and the angle α' of the chassis 4 relative to the axis of the rotary platform 3 at the end of swing are solved by using the spatial kinematics and mechanics model of the walking excavator established in step 2 and the direction correction control parameter optimization model established in step 3. x

[0122] 4.3, according to the sensor feedback values in step 1, the operator controls the walking excavator to adjust the posture, so that the distance h of the walking excavator across the longitudinal axis, the working device 2 is rotated to a certain angle γ by the rotary platform 3( Figure 2b ), and the arm length l of the excavating working device 2 is adjusted to l x , so that the bucket 9 is placed on the ground, and the distance L between the support point o and the center point o1 of the rotary platform 3, the hydraulic cylinder drives the working device 2, and the rear wheels (7, 8) are lifted a certain distance d0( Figure 3 ), so that the three optimization parameters h, γ, and l x are consistent with the optimization results.

[0123] 4.4, the operator controls the walking excavator, the hydraulic motor drives the rotary platform 3, and according to the feedback value of the rotation angle sensor S2, the walking excavator rotary platform 3 rotates at the speed in the optimization model, and the walking excavator chassis 4 rotates an angle α relative to the rotary platform 3 to the optimization result α'( Figure 2c ).

[0124] 4.5, according to the distance measuring sensors S1, S3, whether the angle λ between the axis of the walking excavator and the axis of the transport vehicle and the positioning of the center point o1 of the rotary platform 3 meet the positioning requirements of the transport vehicle, if yes, go to step 4.6, if not, return to step 4.1.

[0125] 4.6, lift the working device 2, so that the rear wheels (7, 8) are on the ground, then the hydraulic motor drives the rotary platform 3, so that the straight line CP of the working device 2 is parallel to the longitudinal axis of the chassis 4, and the bucket 9 is placed on the ground again, so that the rear wheels (7, 8) are lifted a certain distance, and then the rear wheels (7, 8) are folded, as shown in( Figure 2d ), then lift the working device 2, so that the rear wheels (7, 8) are on the ground, and the direction correction adjustment of the excavator is completed.

[0126] Example 1:​

[0127] Take a certain machine as an example, it is known that l2=2.3116m, β=55.1°, The working device 2 has a mass of 1200kg, and its center of mass is 1.915m away from the point P. The slewing platform 3 has a mass of 3300kg, and its center of mass is 0.65m away from the axis of the slewing platform 3. The chassis 4 has a mass of 5500kg, and its center of mass is 0.32m away from the axis of the slewing platform 3. The slewing platform 3 has a rotational speed of 2rpm. The ground friction coefficient μ1=0.5. The friction coefficient of the support point of the excavator bucket 9 is μ2=0.6. The M o =2 / 3rN o μ2(exert a resistance torque on the support point of the bucket, where r is the radius of the contact surface of the bucket, and is taken as 0.2m.

[0128] The multi-objective optimization model is used to optimize the same, and the target values under different approaching angles λ can be obtained. The angle between the longitudinal axis of the walking excavator and the longitudinal axis of the transport vehicle 1 after adjustment of the optimization parameters is shown in FIG. 5, and the longitudinal coordinates of the three points o1, A and B are shown in FIG. 6. Figure 8 Figure 9 From the optimization results, when λ≤20°, the maximum value of the optimization target is 0.0019m, the maximum value of the angle between the longitudinal axis of the walking excavator and the longitudinal axis of the transport vehicle 1 after adjustment is 0.1433°, and the maximum values of the deviations of the longitudinal coordinates of the three points o1, A and B from the expected positions are 0.0051m, 0.0019m and 0.0019m respectively. It can be seen that the deviations after adjustment are very small, the walking excavator is accurately positioned with the transport vehicle 1, and the requirements for the walking excavator to be loaded onto the transport vehicle 1 are met.

[0129] When 20°<λ≤25°, as λ increases, the optimization target gradually increases, the longitudinal coordinates of the points A and B gradually deviate from the expected positions, the longitudinal coordinate of the point o1 deviates slightly from the expected position, the overall positioning deviation of the walking excavator gradually increases, and the angle between the longitudinal axis of the walking excavator and the longitudinal axis of the transport vehicle 1 increases, and the deviation of the centering increases. When reaching 25°, the average deviations of the centering and positioning after adjustment of the longitudinal axis reach the maximum values. At this time, the longitudinal axis after adjustment has an angle of 3.808°, the optimization target, i.e. the average deviations of the longitudinal coordinates of the points o1, A and B are 0.09039m, and the deviations of the longitudinal coordinates of the three points o1, A and B from the expected positions are -0.00573m, -0.1442m and -0.1396m respectively. According to the width size of the transport vehicle 1, the deviation angle and distance can still meet the requirements for the walking excavator to be loaded onto the transport vehicle 1.

[0130] When 20°<λ≤25°, as λ increases, the optimization target gradually increases, the longitudinal coordinates of the points A and B gradually deviate from the expected positions, the longitudinal coordinate of the point o1 deviates slightly from the expected position, the overall positioning deviation of the walking excavator gradually increases, and the angle between the longitudinal axis of the walking excavator and the longitudinal axis of the transport vehicle 1 increases, and the deviation of the centering increases. When reaching 25°, the average deviations of the centering and positioning after adjustment of the longitudinal axis reach the maximum values. At this time, the longitudinal axis after adjustment has an angle of 3.808°, the optimization target, i.e. the average deviations of the longitudinal coordinates of the points o1, A and B are 0.09039m, and the deviations of the longitudinal coordinates of the three points o1, A and B from the expected positions are -0.00573m, -0.1442m and -0.1396m respectively. According to the width size of the transport vehicle 1, the deviation angle and distance can still meet the requirements for the walking excavator to be loaded onto the transport vehicle 1.

[0131] ​When λ > 25°, as λ increases, the optimization target value continues to increase, the A and B points continue to deviate from the expected position, the o1 point continues to deviate slightly from the expected position, and the adjusted longitudinal axis angle continues to increase. At this time, the overall positioning and centering deviation of the walking excavator increases unidirectionally, and the walking excavator cannot meet the loading requirements through one-time directional correction. For example Figure 8 As shown in the figure, the single-time correction can realize the adjustment of the walking excavator longitudinal axis and the transport vehicle 1 longitudinal axis angle λ not less than 20°. The remaining transport vehicle 1 longitudinal axis angle λ after adjustment is used as the initial parameter again to calculate the value of the four optimization parameter variables by using the optimization model, and then the directional adjustment is performed again. By adopting the multi-time correction method, the centering positioning with the transport vehicle can be realized.

Claims

1. A method for directional correction of a walking-type excavator, characterized in that, include: A distance sensor is installed at the center point o1 of the slewing platform of the walking excavator to obtain the spatial position of the center point o1 of the slewing platform relative to the transport vehicle. An angle sensor relative to the initial position is set at the center point o1 of the rotary platform to measure the rotation angle and speed of the rotary platform relative to the chassis, the swing angle γ of the working device, and the angle at the end of the swing of the chassis relative to the axis of the rotary platform. A distance measuring sensor is installed at the center axis of the rear side of the chassis to obtain the position of the distance measuring sensor relative to the transport vehicle. Combined with the distance measuring sensor at the center point o1 of the slewing platform, the spatial position and attitude of the walking excavator chassis relative to the transport vehicle are obtained. Maneuver the walking excavator to make its initial position consistent with the optimized parameters based on the feedback values ​​from the aforementioned sensors, and make the slewing platform rotate at the speed in the optimized model until the walking excavator chassis swings relative to the slewing platform at the optimized value. The three optimization objectives are: the center point o1 of the walking excavator's slewing platform coincides with the longitudinal axis of the transport vehicle; the two front wheel support points A and B are symmetrically located on both sides of the longitudinal axis; the constraints are that the initial positions of support points A and B are located on both sides of the longitudinal axis, and the approach angle is less than a certain angle; the following multi-objective optimization model is constructed: s.t.λ<λ0,A y >0,B y <0 In the formula: w1, w2, and w3 are the weight coefficients of the three optimization objectives, respectively, o 1y A y B y Let $l$ be the ordinates of the center point $o1$ of the slewing platform and the two front wheel support points $A$ and $B$ in the first base coordinate system ${w0}-x0o0y0$; $λ0$ is the upper limit of the approach angle $λ$; $l2$ is the length between the front wheel support point $A$ or $B$ and the center point $o1$ of the slewing platform; and $β$ is the angle between the lines connecting the two front wheel support points $A$ and $B$ and the center point $o1$ of the slewing platform. The first base coordinate system {w0}-x0o0y0 takes the midpoint o0 of the ground projection at the rear end of the transport vehicle as the origin, the x0 axis is horizontally backward along the longitudinal axis of the transport vehicle, and the y0 axis is rotated 90° counterclockwise in the x0 axis direction.

2. The method for directional correction of a walking excavator according to claim 1, characterized in that, The optimization model establishment process is as follows: a. Establish a first base coordinate system with the midpoint o0 of the ground projection at the rear of the transport vehicle as the origin, a second base coordinate system with the bucket support point o in the working device as the origin, and a third base coordinate system with the center point o1 of the slewing platform as the origin; based on the coordinate relationship, obtain the hinge point P between the excavating working device and the slewing platform, the center point o1 of the slewing platform, the two front wheel support points A and B, and the coordinate vectors of the center of mass of the working device, the slewing platform, and the chassis in the first base coordinate system; b. Simplify the motion of the excavator's directional correction process into a static mechanical model, obtain the direction of friction force at the two front wheel support points A and B, and solve for the normal force at the two front wheel support points A and B and the bucket support point o in the working device; through force balance and torque balance, obtain the mechanical model of the walking excavator. c. Transform the mechanical model into a system of first-order differential equations, construct a first-level optimization model to solve the system of first-order differential equations, and then construct a second-level optimization model to optimize the direction correction control parameters.

3. The method for directional correction of a walking excavator according to claim 2, characterized in that, The directions of friction at the two front wheel support points A and B are: The velocity v at point A is determined by the following formula. A direction: θ2 is the velocity v at point A. A With v A1 The included angle, v A1 v A2 These are the decompositions of the velocity at point A in the vertical directions of oA and o1A, respectively; oA is the straight line between the bucket support point o and the front wheel support point A; o1A is the straight line between the center point o1 of the slewing platform and the front wheel support point A; In the formula v A1 =l oA ·dθ1 / dt,v A2 = l2·dα / dt; l2 is the length of o1A; l oA θ is the distance between the bucket support point O and the front wheel support point A; θ1 is the deflection angle of the straight line oo1 relative to the x0 axis; t is time; Friction force f at point A in the left front wheel A Direction and v A In the opposite direction; similarly, the frictional force f at point B in the right front wheel can be obtained. B The direction.

4. The method for directional correction of a walking excavator according to claim 2, characterized in that, The normal forces at the two front wheel support points A and B and the bucket support point o in the working device are respectively: N o < T3-N A -N B Intermediate quantities T1 = g(m1x1 + m2x2 + m3x3), T2 = g(m1y1 + m2y2 + m3y3), T3 = (m1 + m2 + m3)g, T4 = (x A -x0)(y B -y0)-(y A -y0)(x B -x0); (x i y i The coordinates of the center of mass of the working device, the rotating platform, and the chassis in the first base coordinate system {w0}-x0o0y0 are respectively, i = 1,...3; m1, m2, and m3 are the masses of the working device, the rotating platform, and the chassis, respectively; (x0, y0), (x A y A ) and (x B y B ) are the coordinates of points o, A, and B in the first base coordinate system, respectively.

5. The method for directional correction of a walking excavator according to claim 2, characterized in that, The mechanical model of the walking excavator is as follows: l1f A cos(α+β-θ2-τ1)+l1f B cos(θ3+τ2+α)-M o =f A l2cos(τ1+θ2)+f B l2cos(τ2+θ3)(2) Where M o The frictional torque acting on the bucket's rotation; oA f is the distance between the bucket support point O and the front wheel support point A; A f B θ2 represents the frictional forces at points A and B on the two front wheels; θ2 is the velocity v at point A. A With v A1 The included angle, v A1 Let θ be the velocity decomposition of point A in the direction perpendicular to oA; θ3 is the velocity decomposition of point B and v. B1 The included angle, v B1 The velocity at point B is the decomposed velocity in the direction perpendicular to oB; l oB Let θ be the distance between the bucket support point o and the front wheel point B; l1 and l2 are the lengths of oo1 and o1A respectively; β is the angle between component o1A and component o1B; τ1 = ∠oAo1, τ2 = ∠oBo1.

6. The method for directional correction of a walking excavator according to claim 5, characterized in that, The mechanical model is transformed into a system of first-order differential equations as follows: θ1(t), α(t), Let θ1 and its first differential angular velocity be represented at different times t, and let α be the swing angle of the chassis relative to the rotary platform and its first differential angular velocity. θ1 is the deflection angle of the straight line oo1 relative to the x0 axis. Represent θ1(t), α(t), It satisfies equations (1) and (2).

7. The method for directional correction of a walking excavator according to claim 6, characterized in that, The first-order optimization model is constructed as follows: Where t n This represents the time of the nth node; θ1(t n ) represents t n The value of θ1 at time 1; Indicates t n The derivative of time θ1 with respect to time; α(t) n ) represents t n The value of α at time t; Indicates t n The differential of time α with respect to time; N A N B The positive forces at points A and B are respectively.

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