Method for determining interaction force between crawler running system and soft ground

Abstract

The invention relates to the field of dynamics of tracked vehicles in soft ground, in particular to a method for determining interaction force between a tracked running system and the soft ground. According to different types of soft grounds, different design parameters of the crawler belt driving system, and traction force, motion resistance and hook traction force applied to the crawler belt driving system by the soft grounds in different driving states of the crawler belt driving system, the traction performance of the crawler belt driving system on different types of soft grounds can be predicted more accurately. The method is beneficial for establishing a more accurate kinetic model of the tracked vehicle in the soft ground environment, the tracked vehicle driving control method suitable for the soft ground environment is researched based on the whole vehicle model, and the automation and intelligence level of the tracked vehicle in the soft ground environment can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of tracked vehicle dynamics on soft ground, and in particular to a method for determining the interaction force between a tracked vehicle system and the soft ground. Background Art

[0002] Tracked vehicles are important means of transportation in soft terrain environments such as snow, swamps, and deserts. Research on the driving dynamics of tracked vehicles on soft terrain can effectively improve their maneuverability. Developing driving control methods for tracked vehicles on soft terrain based on their dynamics model can significantly enhance the intelligence of tracked vehicles on soft terrain.

[0003] However, due to the lack of a theoretical model that accurately characterizes the interaction forces between the tracked vehicle system and soft ground, the development of tracked vehicle dynamics models in soft ground has been relatively slow, and the tracked vehicle driving control methods developed based on hard ground environments have poor applicability in soft ground environments.

[0004] In order to solve the above problems, it is urgent to propose a method to determine the interaction force between the track driving system and the soft ground, including the track ground pressure distribution, track driving system sinking, track driving system traction, motion resistance and hook traction, and based on this, build a track vehicle dynamics model in soft ground and develop a track vehicle driving control method suitable for soft ground. Summary of the Invention

[0005] The technical problem solved by the present invention is: to overcome the shortcomings of the existing technology and propose a method for determining the interaction force between the tracked driving system and the soft ground. The method can reflect the mechanical properties of the soft ground, the main design parameters of the tracked driving system and the influence of the driving state of the tracked driving system on the interaction force between the two, thereby accurately establishing the dynamic model of the tracked vehicle under different types of soft ground.

[0006] The technical solution of the present invention is:

[0007] A method for determining the interaction force between a crawler system and soft ground, the method comprising the following steps:

[0008] Step 1: Obtain the mechanical properties of soft ground;

[0009] Step 2, give the initial value z0 of the track travel system sinking amount;

[0010] Step 3: Divide the ground track into three parts: the first, second, and third sections. Assume that there are n road wheels above the ground track. The track section before the first road wheel is the first section, and the track section below the i-th road wheel is marked as Li. The second section includes L1, L2, ..., Ln. The track section between the i-th road wheel and the i+1-th road wheel is marked as Qi(i+1). The third section includes Q12, Q23, ..., Q(n-1)n.

[0011] Step 4: Set the initial value of the shape parameter of the first segment to α0, and the initial value of the shape parameter of Qi(i+1) in the third segment to α i ;

[0012] Step 5, calculate the position coordinates and derivative values ​​of the two end points of the first segment;

[0013] Step 6: Based on the pitch angle β of the crawler system, the longitudinal slip state s of the crawler system, the mechanical properties of the soft ground obtained in step 1, the initial value z0 of the crawler system sinkage given in step 2, and the initial value α0 of the shape parameter of the first segment in step 4, a force balance equation is established in the horizontal direction for the first segment, and the tension forces at both ends of the first segment are calculated.

[0014] Step 7: Based on the initial value α0 of the shape parameter of the first segment given in step 4, calculate the difference δ between the vertical resultant force of the tension force at both ends of the first segment, the soft ground pressure and the soft ground shear force obtained in step 6 and the gravity of the first segment itself. w0 ;

[0015] Step 8: Given the judgment value δ w0_critical , when |δ w0 |>δ w0_critical When α0 is changed, repeat steps 5 to 7 until |δ w0 |≤δ w0_critical When , it is considered that the first segment reaches the force balance under this shape parameter;

[0016] Step 9: Based on the initial value α of the shape parameter of the Qi(i+1) track segment in step 4 i , the mechanical properties of the soft ground obtained in step 1, the shape parameters of the first segment obtained in step 8, and the tension at both ends of the first segment obtained in step 6, calculate the tension at both ends of Li;

[0017] Step 10: Calculate the position coordinates and derivative values ​​of Qi(i+1) at both ends of the third segment based on the tension at both ends of Li obtained in step 9 and the mechanical properties of the soft ground obtained in step 1.

[0018] Step 11, establish the force balance equation of Qi(i+1) in the third segment in the horizontal direction, and obtain the tension forces at both ends of Qi(i+1) in the third segment;

[0019] Step 12: Based on the mechanical properties of the soft ground medium obtained in step 1, calculate the difference δ between the resultant vertical force of the tension force, soft ground pressure, and shear force at both ends of Qi(i+1) in the third segment obtained in step 11 and the gravity of Qi(i+1) itself in the third segment. wi ;

[0020] Step 13: Given the judgment value δ wi_critical , when |δ wi |>δ wi_critical When changing α i Repeat steps 9 and 12 until |δ wi |≤δ wi_critical When , it is considered that Qi(i+1) in the third segment reaches force equilibrium under this shape parameter;

[0021] Step 14: Calculate the difference δ between the vertical force exerted by the soft ground on the crawler track and the load on the crawler system. w ;

[0022] Step 15: Given the judgment value δ w_critical , when |δ w |>δ w_critical When , change the value of z0 and repeat steps 3 to 14 until |δ w |≤δ w_critical When , it is considered that the track reaches force balance in the ground section, and the interaction force between the track travel system and the soft ground is obtained. The interaction force includes traction, motion resistance and pull rod tension.

[0023] In step 1, the mechanical properties of the soft ground include pressure-settlement characteristics and shear force-shear displacement characteristics, the pressure-settlement characteristics are obtained by disk loading, and the shear force-shear displacement characteristics are obtained by shearing experiments;

[0024] The pressure-sinking characteristic is expressed as formula (1) or formula (2);

[0025]

[0026] Among them, k c is the cohesive deformation modulus of the soft ground medium, is the friction deformation modulus of soft ground medium, b plate is the width of the disc in the pressure subsidence test; z is the subsidence amount on soft ground, n terrain is the subsidence index of soft ground medium, z w The asymptote of the pressure settlement curve is defined, and its value can be approximated as the depth of the soft ground. w It is an empirical parameter whose value is equal to the settlement z wThe pressure corresponding to 95% of the load is 1 / 3. Formula (1) is widely used in soil mechanics. Formula (2) can better reflect the pressure-settlement relationship when the bearing capacity is small and the hard base has a greater impact on the stress distribution of soft ground media.

[0027] The shear force-shear displacement characteristics are expressed as formula (3), (4) or (5);

[0028]

[0029] Among them, τ max is the peak value of shear force, which can be expressed as c is the cohesive force of the soft ground medium, p is the vertical load applied to the soft ground, is the internal friction angle of the soft ground medium, j is the longitudinal shear displacement, K is the shear deformation modulus, K r and K w is an empirical parameter related to the maximum shear force.

[0030] In step 3, the first segment is in contact only with the soft ground; the second segment is in contact with both the road wheel and the soft ground; and the third segment is in contact only with the soft ground; the shape of the second segment is consistent with the outer contour of the road wheel, and the shapes of the first and third segments are set to the cubic equation f(x)=ax 3 +bx 2 +cx+d, the coefficients of the equation need to be solved;

[0031] In step 4, the shape parameter α0 of the first section refers to the change in the angle between the first section of the crawler and the soft ground after the crawler system sinks into the soft ground;

[0032] In step 5, the position coordinates and derivative values ​​of the two end points of the first segment are expressed as formulas 6 to 11

[0033] x 01 =x det +(0-z det ) / tan(α in +β-α0) (6)

[0034] z 01 =0 (7)

[0035] k 01 =tan(α in +β-α0) (8)

[0036] x 02 =0-Rsin(α in +β+α0) (9)

[0037] z 02 =z0-R+Rcos(αin +β+α0) (10)

[0038] k 02 =tan(α in +β+α0) (11)

[0039] Among them, [x 01 , z 01 , k 01 ] is the horizontal coordinate, vertical coordinate and derivative value of the first segment’s contact point with the soft ground, [x 02 , z 02 , k 02 ] are the horizontal coordinate, vertical coordinate and derivative value of the point where the first segment separates from the soft ground, R is the radius of the road wheel, α in is the designed approach angle of the crawler system. When the driving wheel of the crawler system is at the front in the driving direction, [x det , z det ] is the angle at which the first track section separates from the driving wheel. When the driving wheel of the track system is at the rearmost position in the driving direction, [x det , z det ] is the angle of separation between the first track section and the inducer, which can be expressed as the formula

[0040] x det =-l1cosβ+h1sinβ-Rsin(α in +β-α0) (12)

[0041] z det =x0-R-l1sinβ-h1cosβ+Rcos(α in +β-α0) (13) Among them, l1 and h1 are the distances between the first road wheel and the driving wheel (or inducer wheel) located in front of the first road wheel in the horizontal and vertical directions.

[0042] In step 6, the pitch angle of the crawler system refers to the angle between the line connecting the centers of all the road wheels and the horizontal direction. The longitudinal slip state of the crawler system can be expressed by the longitudinal travel speed of the crawler system and the rotational angular velocity of the driving wheel, as shown in formulas 14 to 15.

[0043]

[0044] In step 6, the force balance equation of the first section is expressed as formula 16

[0045]

[0046] Among them, T 01 is the tension at the point where the first section starts to contact the soft ground, T02 is the tension at the point where the first segment separates from the soft ground, k(x) is the slope of the first segment at any point x, p(x) is the pressure of the first segment at any point x, and τ(x) is the shear force of the first segment at any point x;

[0047] In step 7, the difference δ w0 Expressed as formula 17

[0048]

[0049] In step 8, when |δ w0 |>δ w0_critical When changing the value of α0, it means: when δ w0 >0, increase the value of α0, when δ w0 <0, reduce the value of α0;

[0050] In step 9, the initial value of the shape parameter α of the third segment i is the angle of separation between Qi(i+1) and the i-th road wheel, Li is consistent with the outer contour of the i-th road wheel, and the difference in tension at both ends of Li is the sum of the shear forces on the soft ground applied to Li; the tension at both ends of Li is expressed as formula 19

[0051]

[0052] Among them, T (i-1)2 Refers to the tension at the contact point with the i-th road wheel, T i1 is the tension at the separation point from the i-th road wheel;

[0053] In step 10, the position coordinates and derivative values ​​of Qi(i+1) at both ends in the third segment are expressed as formulas 10 to 25.

[0054] x i1 =(i-1)lcos(β)+Rsin(α i -β) (20)

[0055] z i1 =z0-R+(i-1)lsin(β)+Rcos(α i -β) (21)

[0056] k i1 = -tan(α i -β) (22)

[0057] x i2 =ilcos(β)-Rsin(α i +β) (23)

[0058] z i2=z0-R+ilsin(β)+Rcos(α i +β) (24)

[0059] k i1 =tan(α i +β) (25)

[0060] Among them, [x i1 , z i1 , k i1 ] are the horizontal coordinate, vertical coordinate and derivative value of the separation point between Qi(i+1) and the i-th road wheel, [x i2 , z i2 , k i2 ] are the abscissa, ordinate and derivative values ​​of the contact point between Qi(i+1) and the i+1th road wheel, β is the pitch angle of the track system, l is the distance between road wheels, and the distance between adjacent road wheels is the same;

[0061] In step 11, the force balance equation of Qi(i+1) in the horizontal direction in the third section is expressed as formula 26

[0062]

[0063] Among them, T i1 is the tension force at the contact point between Qi(i+1) and the i-th road wheel in the third section, T i2 is the tension at the contact point between Qi(i+1) and the i+1th road wheel in the third section;

[0064] In step 12, the difference δ w1 Expressed as formula 27

[0065]

[0066] In step 14, δ w Expressed as formula 28

[0067]

[0068] Where W is the vertical mass of the crawler system

[0069] In step 16, the required traction force T, motion resistance R and pull rod tension DB are expressed as formulas 29 to 31:

[0070]

[0071] DB=TR (31)

[0072] Through the above calculations, we can obtain different types of soft ground, different design parameters of the tracked driving system, and the traction, motion resistance and hook traction exerted by the soft ground on the tracked driving system under different driving conditions of the tracked driving system. This can more accurately predict the traction performance of the tracked driving system on different types of soft ground, which is conducive to establishing a more accurate dynamic model of the tracked vehicle in the soft ground environment. In addition, based on the whole vehicle model, the driving control method of the tracked vehicle suitable for the soft ground environment is studied, which can effectively improve the automation and intelligence level of the tracked vehicle in the soft ground environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 It is the pressure subsidence characteristic of soft ground;

[0074] Figure 2 is the shear force-shear displacement characteristic of soft ground;

[0075] Figure 3 This is a schematic diagram of the interaction between the tracked driving system and the soft ground;

[0076] Figure 4 It is the force diagram of the track section in front of the road wheel;

[0077] Figure 5 It is the force diagram of the track section under the road wheel;

[0078] Figure 6 It is the force diagram of the track section between adjacent road wheels;

[0079] Figure 7 The calculation results and experimental results of ground pressure distribution are shown in Figure 2.

[0080] Figure 8 These are the theoretical calculation results and virtual prototype simulation results of the hook traction force of the tracked driving system. DETAILED DESCRIPTION

[0081] In order to more clearly illustrate the objectives, technical solutions, and advantages of the present invention, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0082] The present invention provides a method for determining the interaction between a tracked vehicle system and soft ground. The method comprises the following steps: after determining the shape of the ground-engaging track segment, calculating the traction force, motion resistance and hook traction force of the tracked vehicle system, so as to predict the traction performance of the tracked vehicle system in soft ground, establish a more accurate dynamic model of the tracked vehicle in a soft ground environment, and develop a travel control method for the tracked vehicle in a soft ground environment.

[0083] This example provides a method for determining the interaction forces between a tracked vehicle system and soft ground. This method is applicable to determining the traction force, motion resistance, and hook traction force within the full slip range of a tracked vehicle system on soft ground surfaces such as soil, snow, and swamps. The method's execution process is as follows:

[0084] Example

[0085] A method for determining the interaction force between a crawler system and soft ground, comprising the following steps:

[0086] Step 1: Obtain the mechanical properties of soft ground, such as Figure 1 and Figure 2 They are respectively the pressure settlement characteristics and shear force and displacement characteristics of soft ground;

[0087] Step 2, give the initial value z0 of the track travel system sinking amount;

[0088] Step 3: Divide the ground track into three parts, such as Figure 3 As shown, they are the first, second and third sections respectively. Assume that the track system has n road wheels, the track section before the first road wheel is the first section, the track section below the i-th road wheel is marked as Li, then the second section includes L1, L2, ... Ln, the track section between the i-th road wheel and the i+1-th road wheel is marked as Qi(i+1), then the third section includes Q12, Q23, ..., Q(n-1)n;

[0089] Step 4: Set the initial value of the shape parameter of the first segment to α0, and the initial value of the shape parameter of Qi(i+1) in the third segment to α i ;

[0090] Step 5, calculate the position coordinates and derivative values ​​of the two end points of the first segment;

[0091] Step 6: Based on the pitch angle β of the crawler system, the longitudinal slip state s of the crawler system, the mechanical properties of the soft ground obtained in step 1, the initial value z0 of the crawler system sinkage given in step 2, and the initial value α0 of the shape parameter of the first section in step 4, establish the force balance equation of the first section in the horizontal direction and calculate the tension at both ends of the first section. The force condition of the first section of the crawler is as follows: Figure 4 As shown;

[0092] Step 7: Based on the initial value α0 of the shape parameter of the first segment given in step 4, calculate the difference δ between the vertical resultant force of the tension force at both ends of the first segment, the soft ground pressure and the soft ground shear force obtained in step 6 and the gravity of the first segment itself. w0 ;

[0093] Step 8: Given the judgment value δ w0_critical , when |δ w0 |>δw0_critical When α0 is changed, repeat steps 5 to 7 until |δ w0 |≤δ w0_critical When , it is considered that the first segment reaches the force balance under this shape parameter;

[0094] Step 9: Based on the initial value α of the shape parameter of the Qi(i+1) track segment in step 4 i , the mechanical properties of the soft ground obtained in step 1, the shape parameters of the first section obtained in step 8, and the tension at both ends of the first section obtained in step 6, calculate the tension at both ends of Li, where the force on the crawler track of the Li section is as follows Figure 5 As shown;

[0095] Step 10: Calculate the position coordinates and derivative values ​​of Qi(i+1) at both ends of the third segment based on the tension at both ends of Li obtained in step 9 and the mechanical properties of the soft ground obtained in step 1.

[0096] Step 11: Establish the force balance equation of Qi(i+1) in the third segment in the horizontal direction to obtain the tension at both ends of Qi(i+1) in the third segment. The force condition of Qi(i+1) in the third segment is as follows: Figure 6 As shown;

[0097] Step 12: Based on the mechanical properties of the soft ground medium obtained in step 1, calculate the difference δ between the resultant vertical force of the tension force, soft ground pressure, and shear force at both ends of Qi(i+1) in the third segment obtained in step 11 and the gravity of Qi(i+1) itself in the third segment. wi ;

[0098] Step 13: Given the judgment value δ wi_critical , when |δ wi |>δ wi_critical When changing α i Repeat steps 9 to 12 until |δ wi |≤δ wi_critical When , it is considered that Qi(i+1) in the third segment reaches force equilibrium under this shape parameter;

[0099] Step 14: Calculate the difference δ between the vertical force exerted by the soft ground on the crawler track and the load on the crawler system. w ;

[0100] Step 15: Given the judgment value δ w_critical , when |δ w |>δ w_critical When , change the value of z0 and repeat steps 3 to 14 until |δ w |≤δ w_criticalWhen the track reaches the ground contact section, it is considered that the track reaches the force balance, and the interaction force between the track system and the soft ground is obtained. The interaction force includes traction, motion resistance and pull rod tension. The final calculation result of the track ground pressure distribution is as follows: Figure 7 shown.

[0101] like Figure 8 The calculated results of the hook traction force shown are basically consistent with the virtual prototype simulation results within the full slip range, which verifies the accuracy of the method.

[0102] Specifically, the mechanical properties of the soft ground in step 1 include pressure settlement characteristics and shear force-shear displacement characteristics. The pressure settlement characteristics obtained by the disc loading method can be expressed as formula 32, and the shear force-shear displacement characteristics of the soft ground obtained by the shear test on the soft ground can be expressed as formula 33.

[0103]

[0104] Where p is the pressure of the soft ground, kPa; z is the lower limit of the test disc, m; τ is the shear stress of the soft ground, kPa; j is the shear displacement of the soft ground, m.

[0105] Specifically, in step 2, the initial sinking amount of the crawler system is set to 0.01m;

[0106] Specifically, in step 3, it is assumed that the crawler system has 4 road wheels.

[0107] Specifically, in step 4, the shape parameter α0 of the first segment is set to 0 degrees, and the shape parameters of the third segments Q12, Q23, and Q34 are set to 0.1 degrees, 0.1 degrees, and 0.1 degrees respectively;

[0108] Specifically, in step 5, when the pitch angle of the crawler driving system is 0 degrees, the position coordinates and derivative values ​​of the two end points of the first segment are [x 01 , z 01 , k 01 ]=[-0.005,0,1.732],[x ,2 , z 02 , k 02 ]=[-0.002,0.074,1.732];

[0109] Specifically, in step 6, when the slip rate of the crawler driving system is 0, the tension forces at the two end points of the first section are calculated as follows: 01 The tension at point x is 3000N, which is the initial tension of the crawler system. 02 The tension at the point is 3053.4N;

[0110] Specifically, the difference δ in step 7 w0 =321.5N, which means that the resultant vertical force of the external force on the first track section is greater than the gravity of the track section.

[0111] Specifically, the given judgment value δ in step 8 w0_critical =0.1N,δ w0 >δ w0_critical , so it is necessary to increase the α0 set in step 4. By repeating steps 5 to 7 multiple times, when |δ w0 |≤δ w0_critical When , it is considered that the first section of the crawler reaches the force balance under this shape parameter. Through iterative calculation, the final α0 value obtained is 12.4 degrees.

[0112] Specifically, in step 9, when the initial value of the shape parameter of the given Q12 crawler segment is 0.1 degrees, the tension forces at both ends of L1 are calculated to be x 02 The tension at point x is 3053.4N. 11 The tension at the point is 4012.4N;

[0113] Specifically, in step 10, the position coordinates and derivative values ​​of the two end points of Q12 are calculated as [x 11 , z 11 , k 11 ]=[0.034,0.159,-0.039],[x 12 , z 12 , k 12 ]=[0.38,0.163,0.041];

[0114] Specifically, in step 11, by calculating the force balance equation of the third segment Q12 in the horizontal direction, the tensioning force at both ends of the third segment Q12 can be obtained as x 11 The tension at point x is 4012.4N. 12 The tension at point is 7210.8N;

[0115] Specifically, in step 12, the required δ wi =89.5N, which means that the resultant vertical force of the external force on this track section is less than the total mass of this track section;

[0116] Specifically, in step 13, the judgment value δ is given w1_critical =0.1,δ wi >δ w1_critical , so it is necessary to increase the α1 set in step 4. By repeating steps 9 to 12 multiple times, when |δ w0 |≤δ w0_criticalWhen the first track section reaches force equilibrium under these shape parameters, the iterative calculation results in an α1 value of 1.8 degrees. The same iterative calculation is repeated for α2 and α3 in steps 9 to 12, resulting in final α2 and α3 values ​​of 1.8 and 1.7 degrees, respectively.

[0117] Specifically, in step 14, the difference between the vertical force on the crawler track in the ground contact section and the load on the crawler system is calculated to be δ w =-1433.9N, indicating that the force exerted by the soft ground on the grounded crawler track is less than the load on the crawler travel system;

[0118] Specifically, in step 15, the judgment value δ is given w_critical =10,δ w <δ w_critical , it is necessary to increase the sinking amount z0 of the crawler driving system in step 2, and repeat steps 3 to 14 several times to obtain |δ w |<δ w_critical , it is considered that the track system has reached force balance. By calculating the traction force, motion resistance and hook traction force, the traction force is obtained as T = 1825.4N, the motion resistance is R = 130.8N, and the hook traction force is DB = 1694.6N.

[0119] Based on the results obtained, the traction performance of the tracked driving system under soft ground can be predicted more accurately, and the parameters of the tracked driving system traveling on different types of soft ground can be optimized; a more accurate dynamic model of the tracked vehicle under soft ground environment can be established, and a driving control method for the tracked vehicle under soft ground can be developed, thereby improving the driving performance and intelligence level of the tracked vehicle under soft ground environment.

[0120] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for determining the interaction force between a crawler system and soft ground, characterized in that The steps of the method include: Step 1: Obtain the mechanical properties of soft ground; Step 2, give the initial value z0 of the track travel system sinking amount; Step 3: Divide the ground track into three parts: the first, second, and third sections. Assume that there are n road wheels above the ground track. The track section before the first road wheel is the first section, and the track section below the i-th road wheel is marked as Li. The second section includes L1, L2, ..., Ln. The track section between the i-th road wheel and the i+1-th road wheel is marked as Qi(i+1). The third section includes Q12, Q23, ..., Q(n-1)n. Step 4: Set the initial value of the shape parameter of the first segment to α0, and the initial value of the shape parameter of Qi(i+1) in the third segment to α i ; Step 5, calculate the position coordinates and derivative values ​​of the two end points of the first segment; Step 6: Based on the pitch angle β of the crawler system, the longitudinal slip state s of the crawler system, the mechanical properties of the soft ground obtained in step 1, the initial value z0 of the crawler system sinkage given in step 2, and the initial value α0 of the shape parameter of the first segment in step 4, a force balance equation is established in the horizontal direction for the first segment, and the tension forces at both ends of the first segment are calculated. Step 7: Based on the initial value α0 of the shape parameter of the first segment given in step 4, calculate the difference δ between the vertical resultant force of the tension force at both ends of the first segment, the soft ground pressure and the soft ground shear force obtained in step 6 and the gravity of the first segment itself. w0 ; Step 8: Given the judgment value δ w0_critical , when |δ w0 |>δ w0_critical When α0 is changed, repeat steps 5 to 7 until |δ w0 |≤δ w0_critical When , the first segment reaches force balance under this shape parameter; Step 9: Based on the initial value α of the shape parameter of the Qi(i+1) track segment in step 4 i , the mechanical properties of the soft ground obtained in step 1, the shape parameters of the first segment obtained in step 8, and the tension at both ends of the first segment obtained in step 6, calculate the tension at both ends of Li; Step 10: Calculate the position coordinates and derivative values ​​of Qi(i+1) at both ends of the third segment based on the tension at both ends of Li obtained in step 9 and the mechanical properties of the soft ground obtained in step 1. Step 11, establish the force balance equation of Qi(i+1) in the third segment in the horizontal direction, and obtain the tension forces at both ends of Qi(i+1) in the third segment; Step 12: Based on the mechanical properties of the soft ground medium obtained in step 1, calculate the difference δ between the resultant vertical force of the tension force, soft ground pressure, and shear force at both ends of Qi(i+1) in the third segment obtained in step 11 and the gravity of Qi(i+1) in the third segment. wi ; Step 13: Given the judgment value δ wi_critical , when |δ wi |>δ wi_critical When changing α i Repeat steps 9 and 12 until |δ wi |≤δ wi_critical When , Qi(i+1) in the third segment reaches force equilibrium under this shape parameter; Step 14: Calculate the difference δ between the vertical force exerted by the soft ground on the crawler track and the load on the crawler system. w ; Step 15: Given the judgment value δ w_critical , when |δ w |>δ w_critical When , change the value of z0 and repeat steps 3 to 14 until |δ w |≤δ w_critical When the track reaches the ground contact section, the force balance is achieved, and the interaction force between the track travel system and the soft ground is obtained. The interaction force includes traction, motion resistance and pull rod tension.

2. The method for determining the interaction force between a crawler system and soft ground according to claim 1, characterized in that: In step 1, the mechanical properties of the soft ground include pressure-settlement characteristics and shear force-shear displacement characteristics, the pressure-settlement characteristics are obtained by disk loading, and the shear force-shear displacement characteristics are obtained by shearing experiments; The pressure-sinking characteristic is expressed as formula (1) or formula (2); Among them, k c is the cohesive deformation modulus of the soft ground medium, is the friction deformation modulus of soft ground medium, b plate is the width of the disc in the pressure subsidence test; z is the subsidence amount on soft ground, n terrain is the subsidence index of soft ground medium, z w The asymptote of the pressure settlement curve is defined as the depth of the soft ground, p w It is an empirical parameter whose value is equal to the settlement z w 1 / 3 of the pressure corresponding to 95%; The shear force-shear displacement characteristics are expressed as formula (3), (4) or (5); Among them, τ max is the peak shear force, expressed as c is the cohesive force of the soft ground medium, p is the vertical load applied to the soft ground, is the internal friction angle of the soft ground medium, j is the longitudinal shear displacement, K is the shear deformation modulus, K r and K w is an empirical parameter related to the maximum shear force.

3. The method for determining the interaction force between a crawler system and soft ground according to claim 2, characterized in that: In step 3, the first segment is in contact only with the soft ground; the second segment is in contact with both the road wheel and the soft ground; and the third segment is in contact only with the soft ground; the shape of the second segment is consistent with the outer contour of the road wheel, and the shapes of the first and third segments are set to the cubic equation f(x)=ax 3 +bx 2 +cx+d.

4. A method for determining the interaction force between a crawler system and soft ground according to claim 2 or 3, characterized in that: In step 4, the shape parameter α0 of the first section refers to the change in the angle between the first section of the crawler track and the soft ground after the crawler travel system sinks into the soft ground.

5. The method for determining the interaction force between a crawler system and soft ground according to claim 1, characterized in that: In step 5, the position coordinates and derivative values ​​of the two end points of the first segment are expressed as: x 01 =x det +(0-z det ) / and(α in +β-α0) ( 6 z 01 ＝0 (7) k 01 =tan(α in +β-α0) (8) x 02 =0-Rsin(α in +β+α0) (9) z 02 =z0-R+Rcos(α in +β+α0) (10) k 02 =tan(α in +β+α0) (11) Among them, [x 01 , z 01 , k 01 ] is the horizontal coordinate, vertical coordinate and derivative value of the first segment’s contact point with the soft ground, [x 02 , z 02 , k 02 ] are the horizontal coordinate, vertical coordinate and derivative value of the point where the first segment separates from the soft ground, R is the radius of the road wheel, α un is the designed approach angle of the crawler system. When the driving wheel of the crawler system is at the front in the driving direction, [x det , z det ] is the angle at which the first track section separates from the driving wheel. When the driving wheel of the track system is at the rearmost position in the driving direction, [x det , z det ] is the angle of separation between the first track section and the inducer, which can be expressed as the formula x det =-l1cosβ+h1sinβ-Rsin(α in +β-α0) (12) z det =x0-R-l1sinβ-h1cosβ+Rcos(α in +β-α0) (13) Among them, l1 and h1 are the distances in the horizontal and vertical directions between the first road wheel and the driving wheel or the inducer wheel located in front of the first road wheel.

6. The method for determining the interaction force between a crawler system and soft ground according to claim 5, characterized in that: In step 6, the pitch angle of the tracked driving system refers to the angle between the line connecting the centers of all road wheels and the horizontal direction. The longitudinal slip state of the tracked driving system is represented by the longitudinal driving speed of the tracked driving system and the rotational angular velocity of the driving wheel: In step 6, the force balance equation of the first section is expressed as: Among them, T 01 is the tension at the point where the first section starts to contact the soft ground, T 02 is the tension at the point where the first section separates from the soft ground, k(x) is the slope of the first section at any point x, p(x) is the pressure of the first section at any point x, and τ(x) is the shear force of the first section at any point x.

7. The method for determining the interaction force between a crawler system and soft ground according to claim 6, characterized in that: In step 7, the difference δ w0 Expressed as: In step 8, when |δ w0 |>δ w0_critical When changing the value of α0, it means: when δ w0 >0, increase the value of α0, when δ w0 <0, reduce the value of α0.

8. The method for determining the interaction force between a crawler system and soft ground according to claim 7, characterized in that: In step 9, the initial value of the shape parameter α of the third segment i is the angle at which Qi(i+1) separates from the i-th road wheel. Li is consistent with the outer contour of the i-th road wheel. The difference in tension at both ends of Li is the sum of the shear forces on Li due to the soft ground. The tension at both ends of Li is expressed as: Among them, T (i-1)2 Refers to the tension at the contact point with the i-th road wheel, T i1 is the tension at the separation point from the i-th road wheel; In step 10, the position coordinates and derivative values ​​of the two ends of Qi(i+1) in the third segment are expressed as: x i1 =(i-1)lcos(β)+Rsin(α i -b) (20) z i1 =z0-R+(i-1)lsin(β)+Rcos(α i -b) (21) k i1 =-tan(α i -b) (22) x i2 =ilcos(β)-Rsin(α i +b) (23) z i2 =z0-R+ilsin(β)+Rcos(α i +b) (24) k i1 =tan(α i +b) (25) Among them, [x i1 , z i1 , k i1 ] are the horizontal coordinate, vertical coordinate and derivative value of the separation point between Qi(i+1) and the i-th road wheel, [x i2 , z i2 , k i2 ] are the horizontal coordinate, vertical coordinate and derivative value of the contact point between Qi(i+1) and the i+1th road wheel, β is the pitch angle of the track system, l is the distance between the road wheels, and the distance between adjacent road wheels is the same.

9. The method for determining the interaction force between a crawler system and soft ground according to claim 8, characterized in that: In step 11, the force balance equation of Qi(i+1) in the horizontal direction in the third section is expressed as formula 26 Among them, T i1 is the tension force at the contact point between Qi(i+1) and the i-th road wheel in the third section, T i2 is the tension at the contact point between Qi(i+1) and the i+1th road wheel in the third section; In step 12, the difference δ w1 Expressed as: In step 14, δ w Expressed as: Where W is the vertical mass of the track system.

10. The method for determining the interaction force between a crawler system and soft ground according to claim 9, characterized in that: In step 16, the required traction force T, motion resistance R and pull rod tension DB are expressed as: DB=TR (31).

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