Wheel load estimation device and program

Abstract

To accurately estimate a wheel load without lowering rigidity of a rigid body even when a gravity center of the rigid body fluctuates.SOLUTION: A gravity center inertia value calculation part 36 calculates information on a gravity center of a vehicle including a loaded object, and calculates an inertia tensor Jall including an inertia main shaft and an inertia multiplication around the gravity center of the vehicle, a wheel load fluctuation estimation part 40 estimates a fluctuation amount of the vehicle load based on the inertia tensor Jall, angular speed P, Q and R and angular acceleration P., Q. and R. around the three axes of the vehicle including the loaded object, the front and the back of the vehicle and lateral acceleration GxCG and GyCG, a weight Mall of the vehicle including the loaded object, and information hR, hCG, tl, tr, lf and lr on the gravity center of the vehicle including the loaded object, and a wheel load calculation part 42 calculates the wheel load based on a fluctuation amount of the wheel load and a static load.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a wheel load estimation device and a wheel load estimation program.

Background Art

[0002] Conventionally, in a vehicle such as a forklift that lifts a load and travels, in order to avoid risks such as wheel lift-off and vehicle overturning due to the deviation of the vehicle center of gravity, the load on each wheel supporting the vehicle has been estimated.

[0003] For example, a technique has been proposed for a four-wheel vehicle to measure longitudinal and lateral accelerations, roll angular velocity, and pitch angular velocity (see Patent Document 1). In this technique, the load on each wheel is estimated based on the vertical rigidity of each wheel, longitudinal behavior, inclination of the roll inertia principal axis, pitch moment considering the gyro effect, and roll moment considering the lateral behavior.

[0004] Also, for example, a technique has been proposed for a four-wheel vehicle to measure longitudinal and lateral accelerations, roll angular acceleration, and pitch angular acceleration (see Patent Document 2). In this technique, the load on each wheel is estimated based on the pitch moment due to longitudinal behavior, the roll moment due to lateral behavior, the pitch inertia of the vehicle, and the roll inertia of the vehicle.

[0005] Also, for example, a technique has been proposed for a forklift to measure the load on each wheel and the wheel speeds of the two driving wheels (see Patent Document 3). In this technique, the wheel speeds are used to calculate the turning radius, and the steering amount and drive torque are adjusted in response to a decrease in any of the wheel load measurement values.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, the technologies described in Patent Documents 1 and 2 are targeted at general four-wheeled vehicles, and do not consider, for example, a forklift that travels while loading heavy loads in various states. Therefore, the technologies described in Patent Documents 1 and 2 have a problem that the wheel loads of vehicles that travel while loading heavy loads in various states cannot be appropriately estimated.

[0008] In addition, in the technology described in Patent Document 3, in order to measure the wheel load, the strain at the loading location of the load is used. However, in order to obtain the strain, it is necessary to reduce the rigidity of the loading location of the load, which causes a problem of safety risk.

[0009] The present invention has been made in view of the above circumstances, and an object thereof is to provide a wheel load estimation device and a program capable of accurately estimating the wheel load without reducing the rigidity of a rigid body even when the center of gravity of the rigid body fluctuates.

Means for Solving the Problems

[0010] In order to achieve the above object, the wheel load estimation device according to the present invention includes an acquisition unit that acquires the angular velocity, angular acceleration around three axes of a rigid body including an element that causes a change in the center of gravity, the acceleration in the longitudinal direction which is the traveling direction of the rigid body and the lateral direction which is the width direction of the rigid body, the weight of the element, and the position including the height of the element; a center-of-gravity inertia value calculation unit that calculates information regarding the center of gravity of the rigid body and calculates an inertia value including the principal axes of inertia around the center of gravity of the rigid body; a wheel load fluctuation estimation unit that estimates the fluctuation amount of the wheel load acting on each of a plurality of wheels that support the rigid body based on the angular velocity, the angular acceleration, and the accelerations in the longitudinal and lateral directions acquired by the acquisition unit, and the information regarding the center of gravity of the rigid body and the inertia value calculated by the center-of-gravity inertia value calculation unit; and a wheel load calculation unit that calculates the wheel load based on the fluctuation amount of the wheel load estimated by the wheel load fluctuation estimation unit and the static load acting on each of the wheels.

[0011] According to the wheel load estimation device of the present invention, the acquisition unit acquires the angular velocity, angular acceleration around three axes of a rigid body including an element that causes a change in the center of gravity, the acceleration in the longitudinal direction which is the traveling direction of the rigid body and the lateral direction which is the width direction of the rigid body, the weight of the element, and the position including the height of the element; the center-of-gravity inertia calculation unit calculates information regarding the center of gravity of the rigid body and calculates an inertia value including the principal axes of inertia around the center of gravity of the rigid body; the wheel load fluctuation amount estimation unit estimates the fluctuation amount of the wheel load acting on each of a plurality of wheels that support the rigid body based on the angular velocity, the angular acceleration, and the accelerations in the longitudinal and lateral directions acquired by the acquisition unit, and the information regarding the center of gravity of the rigid body and the inertia value calculated by the center-of-gravity inertia value calculation unit; and the wheel load calculation unit calculates the wheel load based on the fluctuation amount of the wheel load estimated by the wheel load fluctuation estimation unit and the static load acting on each of the wheels. Thereby, even when the center of gravity of the rigid body fluctuates, the wheel load can be accurately estimated without reducing the rigidity of the rigid body.

[0012] Further, the center-of-gravity inertia value calculation unit calculates the center-of-gravity positions of the rigid body including the element and each of the constituent parts based on the weight and position of the element acquired by the acquisition unit and the structure of each of the plurality of constituent parts constituting the rigid body, and uses the difference between the center-of-gravity position of the rigid body including the element and the center-of-gravity positions of each of the constituent parts to calculate the inertia value. Thereby, the inertia value corresponding to the variation of the center of gravity can be appropriately calculated.

[0013] Further, the center-of-gravity inertia value calculation unit can calculate the inertia value further including the product of inertia. Thereby, the inertia value corresponding to the variation of the center of gravity can be more appropriately calculated, and the wheel load can be estimated more accurately.

[0014] Further, the acquisition unit acquires the lateral force and longitudinal force acting on the wheel, and the wheel load variation estimation unit can further use the yaw moment around the center of gravity of the rigid body calculated based on the lateral force and the longitudinal force acquired by the acquisition unit to estimate the variation of the wheel load. Thereby, the wheel load can be estimated in consideration of the yaw moment around the center of gravity of the rigid body.

[0015] Further, the wheel load variation calculation unit can calculate the yaw moment around the center of gravity of the rigid body together with the variation of the wheel load under the constraint that the sum of the variations of the wheel load for each of the plurality of wheels is 0 and the relational expression between the roll synthesis distribution of the front and rear wheels and the load variation. Thereby, based on the information acquired by the acquisition unit, the yaw moment can be calculated together with the wheel load.

[0016] Further, the rigid body is a vehicle, and the element that gives a variation to the center of gravity can be the load carried on the vehicle. Further, the vehicle is a forklift, and the load can be assumed to be loaded on forks that can operate up and down. Thereby, for a vehicle that travels while loading a load in various states, such as a forklift, the wheel load can be accurately estimated.

[0017] In addition, the information regarding the center of gravity of the rigid body can include the vertical distance between the center of gravity position of the rigid body and the roll center of the rigid body, the lateral position of the center of gravity position of the rigid body, and the lateral distance between each of the plurality of wheels and the center of gravity position of the rigid body.

[0018] Further, the wheel load estimation program according to the present invention is a program for causing a computer to function as each part of the above wheel load estimation device.

Advantages of the Invention

[0019] According to the wheel load estimation device and program of the present invention, even when the center of gravity of the rigid body fluctuates, the wheel load can be accurately estimated without reducing the rigidity of the rigid body.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Mode for Carrying Out the Invention

[0021] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0022] <First Embodiment> First, the principle of the first embodiment will be described. In the first embodiment, as an example of a rigid body including an element that gives a variation to the center of gravity, a forklift having four wheels in the front, rear, left, and right that travels with a load loaded on a fork that can operate vertically will be described for the case of estimating each wheel load. Further, in the first embodiment, it is assumed that vehicle behavior including the longitudinal acceleration, lateral acceleration, roll angular velocity, pitch angular velocity, and yaw angular velocity of the forklift is measured. Further, in the first embodiment, it is assumed that the weight of the load, the lift height, and the loading position of the load with respect to the fork can be detected.

[0023] Unlike a passenger car, a forklift travels while lifting a heavy load at various lift heights. Also, the loading position of the load may shift in the y-direction (the lateral direction of the forklift) with respect to the center-of-gravity position of the forklift. Depending on the loading state of such a load, the direction of the principal axis of inertia changes with respect to each of the roll, pitch, and yaw rotation axes. Therefore, in the first embodiment, the principal axis of inertia and the products of inertia are set according to the loading state of the load. FIG. 1 is a conceptual diagram schematically showing the difference in the principal axis of inertia due to the difference in the lift height of the load. As shown in FIG. 1(A), when the height of the lift with the load is low and as shown in FIG. 1(B), when the lift height is high, the direction of the principal axis of inertia changes.

[0024] To cope with the difference in the loading state of the load as shown in FIG. 1, the vehicle motion is described using the 6-degree-of-freedom model of the vehicle shown in FIG. 2 and the following equations (1) to (3). Note that equation (1) is the rotational motion of the vehicle, equation (2) is the translational motion of the vehicle, and equation (3) is an equation representing the attitude of the vehicle coordinate system (the coordinate system of x, y, and z in FIG. 2) with respect to the ground coordinate system (the coordinate system of x e , y e , z e in FIG. 2). In the vehicle coordinate system, the longitudinal direction (travel direction) of the vehicle is the x-axis direction, the lateral direction (width direction) of the vehicle is the y-axis direction, and the vertical direction is the z-axis direction.

[0025]

Equation

[0026] In equations (1) to (3), P, Q, and R are the angular velocities [rad / s] of roll, pitch, and yaw, respectively, L v , M v , and N v are the moments [Nm] of roll, pitch, and yaw, respectively. Also, U, V, and W are the velocities [m / s] in the x, y, and z axis directions in the vehicle coordinate system, and φ, θ, and ψ are the attitude angles [rad] of the vehicle coordinate system with respect to the ground coordinate system. Also, X v , Y v , and Z vare the longitudinal force, lateral force, and vertical force [N] acting on the vehicle. Also, J all is the inertia tensor [kg·m 2 consisting of the principal axes of inertia and products of inertia in the directions of the x, y, and z axes, M all is the total mass [kg] obtained by combining the mass of the load and the vehicle mass. The inertia tensor is an example of the "inertia value" of the present invention.

[0027] Also, Fig. 3 shows the acting forces related to each of the roll moment L v , pitch moment M v , and yaw moment N v . Point A in Fig. 3(A) is the roll rotation center, which is the point where the vertical line passing through the center of gravity of the entire vehicle at rest intersects the roll axis. Point B in Fig. 3(B) is the pitch rotation center, which is the point where the vertical line passing through the center of gravity of the entire vehicle at rest intersects the ground surface. Also, CG all is the center of gravity of the forklift including the load (hereinafter referred to as "the entire vehicle"), G xCG and G yCG are the longitudinal acceleration and lateral acceleration [m / s all at the center of gravity CG 2 of the entire vehicle, and g is the gravitational acceleration [m / s 2 . Also, ΔFL z , ΔFR z , ΔRL z , and ΔRR z are the fluctuations in the wheel loads of the front, rear, left, and right wheels [N], FL Fx and FR Fx are the longitudinal forces of the tires of the left and right front wheels [N], FL Fy , FR Fy , RL Fy , and RR Fy are the lateral forces of the tires of each wheel. Also, h CG is the distance in the z-axis direction between the ground surface and CG all (center of gravity height) [m], h R is the distance in the z-axis direction between the ground surface and point A (roll center) [m], t l and t r are the distances in the y-axis direction of the left and right wheels with respect to CG all [m], l f and l r are the distances in the y-axis direction of the left and right wheels with respect to CG allis the distance [m] in the x-axis direction of the front and rear wheels with respect to it.

[0028] In the first embodiment, the part related to the rotational motion of the vehicle in equation (1) is utilized. Referring to FIG. 4, the inertial tensor J in equation (1) all will be described. FIG. 4 shows the schematics of each component part of the entire vehicle 100, together with the center of gravity of each component part, the center of gravity of the entire vehicle, and the coordinate origin. In the example of FIG. 4, as the component parts of the forklift, the vehicle body 102, the load 104, the forks 106, the outer mast 108, and the inner mast 110 are assumed. Note that the component parts also include an IMU (Inertial Measurement Unit) 112. Here, it is considered that the IMU 112 is extremely lightweight and does not affect the center of gravity of the entire vehicle 100. In FIG. 4, at the center of gravity position of each component part, a mark indicating the center of gravity position is shown by a symbol with "A" added to the end of the symbol of each component part. Note that the size of the circle indicating the center of gravity position roughly represents the magnitude of the weight of each component part.

[0029] The configuration of the inertial tensor J all is shown in the following equation (4). On the right side of equation (4), the diagonal terms are the principal axes of inertia and the off-diagonal terms are the products of inertia.

[0030]

Equation

[0031] In equation (4), the subscript j is a variable that specifies each component part, N is the total number of component parts, and m j is the weight of component part j. The position (x all , y CG , z CG , z CG ) of the center of gravity CG j of the entire vehicle 100 can be calculated using the weight of the load 104, the lift height, and the loading position of the load 104 with respect to the forks 106. In equation (4), Δx j , Δy j , and Δz all are the center of gravity CG allThe position 100A and the position (x j , y j , z j ) of the center of gravity of the component part j, 102A, 104A, 106A, 108A, 110A respectively, are the differences in each axial direction and are calculated by the following formula (5).

[0032]

Equation

[0033] J in formula (4) A and J B are correction values of inertia as seen from points A and B in Fig. 3 respectively, and are expressed by the following formulas (6) and (7).

[0034]

Equation

[0035] The roll moment L v and the pitch moment M v in formula (1) are expressed by the following formulas (8) and (9) as the sum of the moment acting on the vehicle by the lateral force and longitudinal force of the tire and the moment by the tire spring (vertical spring) reaction force based on Figs. 3(A) and (B).

[0036]

Equation

[0037] Formulas (8) and (9) represent the moment around the center of gravity CG all of the entire vehicle 100, and the sum of the longitudinal forces and the sum of the lateral forces of the tires of each wheel are represented using the longitudinal acceleration G all and the lateral acceleration G xCG around the center of gravity CG yCG of the entire vehicle 100 and the mass M all . As shown in Fig. 4, when the IMU 112 is attached to an arbitrary position of the vehicle body 102, the measured values G x and G y of the IMU 112 are the center of gravity CG of the entire vehicle 100all shall be converted into the acceleration at the position. Yaw moment N v is, based on FIG. 3(C), the sum of the moments by the front and rear forces FL Fx and FR Fx of the driving two wheels, and the lateral forces FL Fy and FR Fy of each wheel, RL Fy and RR Fy and is expressed by the following formula (10).

[0038]

Equation

[0039] The IMU 112 can measure the accelerations (P, Q, and R) of roll, pitch, and yaw, and the longitudinal acceleration and lateral acceleration at the center of gravity CG all of the entire vehicle 100. The yaw moment N Fx is obtained by detecting the front and rear forces FL Fx and FR Fy of the tires and the lateral forces FL Fy and FR Fy of the tires, RL Fy and RR v of the tires. Also, P · in formula (1) (a dot is placed above "P" in the formula, and the same applies to Q and R below), Q · and R · shall be calculated by approximate differentiation or the like of P, Q, and R measured for each sampling. In this case, only the wheel loads in formula (1) are unknown parameters. By expressing formula (1) using formulas (4) to (10) and obtaining the variations of the wheel loads, which are the unknown parameters, the following formula (11) holds.

[0040]

Equation

[0041] In equation (11), the '+' on the upper right of the first term on the right side represents the pseudo-inverse matrix, and the variation of the wheel load on the left side is obtained as an approximate value. Therefore, the relationship between the left side and the right side of equation (11) is expressed as '≒'. Hereafter, when using the pseudo-inverse matrix, all relationships between the left side and the right side will be expressed as '≒'. The subscript i represents the sampling interval. The reason why the element in the third row of the first term on the right side is 0 is that the variation of each wheel load in the vertical direction does not contribute to the yaw rotation motion. Regarding this, J all , R · (i) , N v(i) Since they do not affect the variation of each wheel load, they can be arbitrary values. Each wheel load is calculated by the sum of the static load and the variation of the wheel load estimated by equation (11).

[0042] Also, as a deformation of equation (11), it is also possible to estimate the variation of each wheel load and the yaw moment as unknown parameters. In this case, equation (11) is deformed as shown in the following equation (12).

[0043]

Equation

[0044] Also, for equation (12), the following two conditions are added. The sum of the variations of each wheel load at each sampling time i is 0, and the following equation (13) holds.

[0045]

Equation

[0046] Also, using the vertical rigidities k f , k r of the front and rear wheels, the roll rigidity distribution of the front and rear wheels is a f (=k f / (k f +k r ))), a r (=k r / (k f +k rWhen expressed as ( )), Equation (14) holds between each wheel load variation and the roll rigidity distribution.

[0047]

Number

[0048] When adding the relationships of Equation (13) and Equation (14) to Equation (12), the following Equation (15) holds, and using Equation (15), it is possible to estimate the variation of each wheel load and the yaw moment. The ‘-1’ on the upper right of the first term on the right side of Equation (15) represents the inverse matrix.

[0049]

Number

[0050] However, in Equation (15), J all * becomes the following Equation (16) obtained by transforming Equation (4).

[0051]

Number

[0052] Next, the configuration of the wheel load estimation device according to the first embodiment will be described.

[0053] As shown in FIG. 5, an IMU 112, a pressure sensor 114, an encoder 116, and an operation amount sensor 118 are connected to the wheel load estimation device 10 according to the first embodiment. The wheel load estimation device 10 is installed at an arbitrary position of the vehicle (forklift).

[0054] As described above, the IMU 112 is installed at an arbitrary position of the vehicle (forklift), detects the angular acceleration around each of the three axes of the vehicle coordinate system and the acceleration in each axis direction, and outputs the detected values. The pressure sensor 114 is, for example, a sheet-shaped sensor provided on the entire loading surface of the fork 106 on which the load 104 is loaded, detects the pressure applied to each position of the loading surface, and outputs the detected values. The encoder 116 detects the rotation angle of the hoisting hydraulic motor for raising and lowering the inner mast 110, and outputs the detected values. The operation amount sensor 118 detects each of the accelerator pedal depression amount, the brake pedal depression amount, and the steering angle, and outputs the detected values.

[0055] As shown in FIG. 6, functionally, the wheel load estimation device 10 includes a longitudinal acceleration acquisition unit 12, a lateral acceleration acquisition unit 14, a roll angular velocity acquisition unit 16, a pitch angular velocity acquisition unit 18, and a yaw angular velocity acquisition unit 20. Further, the wheel load estimation device 10 includes a payload acquisition unit 22, a load position acquisition unit 24, a lift height acquisition unit 26, a tire longitudinal force acquisition unit 28, and a tire lateral force acquisition unit 30. Further, the wheel load estimation device 10 includes an angular acceleration calculation unit 32, a vehicle specifications DB (Database) 34, a center of gravity inertia value calculation unit 36, a yaw moment calculation unit 38, a wheel load variation estimation unit 40, and a wheel load calculation unit 42.

[0056] The longitudinal acceleration acquisition unit 12 receives the detected value output from the IMU 112, and uses the acceleration G in the x-axis direction included in the detected value as the longitudinal acceleration G at the center of gravity CG of the entire vehicle 100. Similarly, the lateral acceleration acquisition unit 14 receives the detected value output from the IMU 112, and uses the acceleration G in the y-axis direction included in the detected value as the lateral acceleration G at the center of gravity CG of the entire vehicle 100. x at the center of gravity CG of the entire vehicle 100 all as the longitudinal acceleration G xCG at the center of gravity CG of the entire vehicle 100 y as the lateral acceleration G all at the center of gravity CG of the entire vehicle 100 yCG and acquires it.

[0057] The roll angular velocity acquisition unit 16 receives the detection value output from the IMU 112, and acquires the angular velocity around the x-axis included in the detection value as the roll angular velocity P. The pitch angular velocity acquisition unit 18 receives the detection value output from the IMU 112, and acquires the angular velocity around the y-axis included in the detection value as the pitch angular velocity Q. The yaw angular velocity acquisition unit 20 receives the detection value output from the IMU 112, and acquires the angular velocity around the z-axis included in the detection value as the yaw angular velocity R.

[0058] The loaded weight acquisition unit 22 receives the detection value output from the pressure sensor 114, and converts the detection value indicating the pressure into weight, thereby obtaining the weight M of the load 104 loaded on the fork 106. α The loaded position acquisition unit 24 receives the detection value output from the pressure sensor 114, and acquires the position where the largest detection value is detected on the loading surface of the fork 106 as the position of the load 104 loaded on the fork 106. The lift height acquisition unit 26 receives the detection value output from the encoder 116, calculates the height of the fork 106 with respect to the reference position (for example, the lowest position) from the rotation angle of the hoisting hydraulic motor indicated by the detection value, and acquires this height as the lift height.

[0059] The tire longitudinal force acquisition unit 28 receives the detection value output from the operation amount sensor 118, and inputs each of the accelerator pedal depression amount, the braking force based on the brake pedal depression amount, and the steering angle indicated by the detection value into a predefined tire characteristic model, thereby obtaining the tire longitudinal forces FL Fx 、FR Fx Thereby obtaining. Similarly, the tire lateral force acquisition unit 30 receives the detection value output from the operation amount sensor 118, and inputs the accelerator pedal depression amount, the braking force based on the brake pedal depression amount, the steering angle, the vehicle speed, the yaw rate, etc. indicated by the detection value into a predefined tire characteristic, thereby obtaining the tire lateral forces FL Fy 、FR Fy 、RL Fy 、RR Fy Thereby obtaining.

[0060] The angular acceleration calculation unit 32 approximately differentiates each of the roll angular velocity P, pitch angular velocity Q, and yaw angular velocity R obtained at each sampling in each of the roll angular velocity acquisition unit 16, pitch angular velocity acquisition unit 18, and yaw angular velocity acquisition unit 20, thereby obtaining the roll angular acceleration P · , pitch angular acceleration Q · , and yaw angular acceleration R · are each calculated.

[0061] The vehicle specifications DB 34 stores various data related to the vehicle. Specifically, the roll center h R , weight M β , the static load FL of each wheel z0 , FR z0 , RL z0 , RR z0 , the shape of each component part, the weight m j , etc., the structure including the structure, and information including the arrangement of each wheel are stored.

[0062] The center of gravity inertia value calculation unit 36 adds the weight M α of the load 104 obtained by the load weight acquisition unit 22 and the weight M β of the vehicle stored in the vehicle specifications DB 34 to calculate the weight M all of the entire vehicle 100 including the load 104. Further, the center of gravity inertia value calculation unit 36 calculates the position 104A of the center of gravity of the load based on the information obtained by each of the load weight acquisition unit 22, load position acquisition unit 24, and lift height acquisition unit 26. As a method for calculating the position 104A of the center of gravity of the load, for example, the method described in Japanese Patent Application Laid-Open No. 2020-93741 can be adopted.

[0063] Further, the center of gravity inertia value calculation unit 36 calculates the position 100A of the center of gravity CG all of the entire vehicle 100 and the positions 102A, 106A, 108A, 110A of the centers of gravity of the component parts j based on the position 104A of the center of gravity of the load and the structure of each component part stored in the vehicle specifications DB 34. Then, the center of gravity inertia value calculation unit 36 uses equation (5) to calculate the center of gravity CG allThe differences (Δx j , Δy j , and Δz j ) in each axial direction between the position 100A and the positions 102A, 104A, 106A, 108A, 110A of the center of gravity of the component part j are calculated. Further, the center of gravity inertia value calculation unit 36 uses the calculated Δx j , Δy j , and Δz j and the weight m j of the component part j stored in the vehicle specifications DB 34 to calculate the inertia tensor J all according to equation (4).

[0064] Further, the center of gravity inertia value calculation unit 36 sets the position in the z-axis direction among the positions 100A of the center of gravity CG all of the entire vehicle 100 calculated to be h CG .

[0065] Based on the position 100A of the center of gravity CG all of the entire vehicle 100 calculated by the center of gravity inertia value calculation unit 36 and the information on the arrangement of each wheel stored in the vehicle specifications DB 34, the yaw moment calculation unit 38 calculates the distances t all and t l in the y-axis direction of the left and right wheels with respect to CG r , and the distances l all and l f in the x-axis direction of the front and rear wheels with respect to CG r . Then, the yaw moment calculation unit 38 uses the calculated t l , t r , l f , l r and the tire longitudinal forces FL Fx , FR Fx , and the tire lateral forces FL Fy , FR Fy , RL Fy , RR Fy obtained by the tire longitudinal force acquisition unit 28 and the tire lateral force acquisition unit 30 to calculate the yaw moment N v according to equation (10).

[0066] The wheel load fluctuation estimation unit 40 uses h CGand the position h of the roll center stored in the vehicle specifications DB34 R From this and CG all and the roll center h R the distance in the z-axis direction between them (h CG -h R ) is calculated. Then, the wheel load fluctuation estimation unit 40 uses the longitudinal acceleration G acquired by the longitudinal acceleration acquisition unit 12 xCG and the lateral acceleration G acquired by the lateral acceleration acquisition unit 14 yCG and the roll angular velocity P acquired by the roll angular velocity acquisition unit 16, the pitch angular velocity Q acquired by the pitch angular velocity acquisition unit 18, the yaw angular velocity R acquired by the yaw angular velocity acquisition unit 20, and the roll angular acceleration P calculated by the angular acceleration calculation unit 32 · , the pitch angular acceleration Q · , the yaw angular acceleration R · and the weight M of the entire vehicle 100 calculated by the center of gravity inertia value calculation unit 36 all , the inertia tensor J all , CG all the position h in the z-axis direction of CG and the calculated CG all and the roll center h R the distance in the z-axis direction between them (h CG -h R ) and the yaw moment N calculated by the yaw moment calculation unit 38 v , CG all the distances t in the x and y-axis directions of each wheel with respect to l , t r , l f , l r to estimate the fluctuations ΔFL z , ΔFR z , ΔRL z , and ΔRR z of each wheel load according to equation (11).

[0067] The wheel load calculation unit 42 uses the fluctuations ΔFL z , ΔFR z , ΔRL z , and ΔRR z of each wheel load estimated by the wheel load fluctuation estimation unit 40 and the static wheel loads FL z0 , FR z0 , RL z0 , and RR stored in the vehicle specifications DB34z0 By the sum with, each wheel load FL z , FR z , RL z , and RR z are calculated and output as an estimation result.

[0068] FIG. 7 is a block diagram showing the hardware configuration of the wheel load estimation device 10 according to the first embodiment. As shown in FIG. 7, the wheel load estimation device 10 includes a CPU (Central Processing Unit) 52, a memory 54, a storage device 56, an input device 58, an output device 60, a storage medium reader 62, and a communication I / F (Interface) 64. Each component is connected to be communicable with each other via a bus 66.

[0069] The storage device 56 stores a wheel load estimation program for executing the wheel load estimation process. The CPU 52 is a central processing unit that executes various programs and controls each component. That is, the CPU 52 reads a program from the storage device 56 and executes the program using the memory 54 as a work area. The CPU 52 performs control of each of the above components and various arithmetic processes according to the program stored in the storage device 56.

[0070] The memory 54 is composed of a RAM (Random Access Memory) and temporarily stores programs and data as a work area. The storage device 56 is composed of a ROM (Read Only Memory), an HDD (Hard Disk Drive), an SSD (Solid State Drive), etc., and stores various programs including an operating system and various data.

[0071] The input device 58 is a device for performing various inputs, such as a keyboard or a mouse. The output device 60 is a device for outputting various information, such as a display or a printer. By adopting a touch panel display as the output device 60, it may function as the input device 58. The storage medium reader 62 reads data stored in various storage media such as CD (Compact Disc)-ROM, DVD (Digital Versatile Disc)-ROM, Blu-ray Disc, and USB (Universal Serial Bus) memory, and writes data to the storage medium.

[0072] The communication I / F 64 is an interface for communicating with other devices. For example, standards such as Ethernet (registered trademark), FDDI, and Wi-Fi (registered trademark) are used.

[0073] Next, the operation of the wheel load estimation device 10 according to the first embodiment will be described. When the forklift starts to run, the wheel load estimation process shown in FIG. 8 is executed in the wheel load estimation device 10.

[0074] In step S10, each of the center of gravity inertia value calculation unit 36, the yaw moment calculation unit 38, the wheel load fluctuation estimation unit 40, and the wheel load calculation unit 42 acquires necessary information from the vehicle specifications DB 34. In step S12, the load weight acquisition unit 22 acquires the weight M α of the load 104 loaded on the fork 106 from the detection value of the pressure sensor 114, the load position acquisition unit 24 acquires the position of the load 104 from the detection value of the pressure sensor 114, and the lift height acquisition unit 26 acquires the lift height from the detection value of the encoder 116.

[0075] Next, in step S14, the center of gravity inertia value calculation unit 36 calculates the weight M all and the center of gravity CG all of the entire vehicle 100 and the positions 100A of the center of gravity, 102A, 104A, 106A, 108A, 110A of the center of gravity of the component part j, and calculates the inertia tensor J by the formula (4) allCalculate it.

[0076] Next, in step S16, the longitudinal tire force acquisition unit 28 and the lateral tire force acquisition unit 30, based on the detection value of the operation amount sensor 118 and a predefined tire characteristic model, calculate the longitudinal tire forces FL Fx , FR Fx and the lateral tire forces FL Fy , FR Fy , RL Fy , RR Fy and acquire them.

[0077] Next, in step S18, each of the longitudinal acceleration acquisition unit 12, the lateral acceleration acquisition unit 14, the roll angular velocity acquisition unit 16, the pitch angular velocity acquisition unit 18, and the yaw angular velocity acquisition unit 20 obtains the longitudinal acceleration G xCG , the lateral acceleration G yCG , the roll angular velocity P, the pitch angular velocity Q, and the yaw angular velocity R respectively from the detection values of the IMU 112.

[0078] Next, in step S20, the angular acceleration calculation unit 32 approximately differentiates each of the roll angular velocity P, the pitch angular velocity Q, and the yaw angular velocity R obtained in step S18 above, to calculate each of the roll angular acceleration P · , the pitch angular acceleration Q · , and the yaw angular acceleration R · .

[0079] Next, in step S22, the yaw moment calculation unit 38 calculates the distances t all in the y-axis direction of the left and right wheels with respect to the CG l and t r , and the distances l all in the x-axis direction of the front and rear wheels with respect to the CG f and l r . Then, the yaw moment calculation unit 38 uses the calculated t l , t r , l f , l r and the longitudinal tire forces FL Fx , FR Fx , and the lateral tire forces FL Fy , FR Fy , RLFy , RR Fy Using RR, the yaw moment N is calculated by equation (10). v Calculate it.

[0080] Next, in step S24, the wheel load fluctuation estimation unit 40 calculates the distance (h all - h R ) in the z-axis direction between the CG and the roll center h CG - h R ). Then, the wheel load fluctuation estimation unit 40 uses G xCG , G yCG , P, Q, R, P · , Q · , R · , M all , J all , h CG , N v , t l , t r , l f , l r - h CG - h R ) calculated above and equation (11) to estimate the fluctuations ΔFL z , ΔFR z , ΔRL z , and ΔRR z of each wheel load.

[0081] Next, in step S26, the wheel load calculation unit 42 calculates each wheel load by adding the fluctuations ΔFL z , ΔFR z , ΔRL z , and ΔRR z estimated in step S24 above to the static wheel loads FL z0 , FR z0 , RL z0 , RR z0 obtained in step S10 above, and outputs it as an estimation result. Then, the process returns to step S12, and while the forklift is running, the processes of steps S12 to S26 are repeatedly executed. The estimated result of the wheel load output is used for control such as preventing the forklift from tipping over.

[0082] As described above, according to the wheel load estimation device according to the first embodiment, by setting the principal axis of inertia and the products of inertia according to the loading state of the load and estimating each wheel load, the wheel load can be accurately estimated. Further, since the wheel load can be estimated only by mounting a simple sensor such as an IMU, it is not necessary to perform load measurement using a general strain gauge, load cell, or the like. Therefore, since the wheel load can be estimated without reducing the rigidity of the fork portion, the risk of rigidity reduction can be avoided.

[0083] Further, according to the wheel load estimation device according to the first embodiment, by utilizing the fact that the sum of the fluctuations of each wheel load becomes zero, in addition to each wheel load, the yaw moment can also be estimated. The estimated yaw moment can be used for the control of torque vectoring.

[0084] <Modification Example of the First Embodiment> In the wheel load fluctuation estimation unit 40 of the wheel load estimation device 10 according to the first embodiment, the fluctuations of each wheel load and the yaw moment may be estimated. FIG. 9 shows a functional block diagram of a wheel load estimation device 10A according to a modification example of the first embodiment. Hereinafter, in the wheel load estimation device 10A, differences from the wheel load estimation device 10 will be described.

[0085] In the wheel load estimation device 10A, the tire longitudinal force acquisition unit 28, the tire lateral force acquisition unit 30, and the yaw moment calculation unit 38 of the wheel load estimation device 10 according to the first embodiment are omitted.

[0086] The center-of-gravity inertia value calculation unit 36A calculates the weight M of the entire vehicle 100 including the load 104, the inertia tensor J, and the position h in the z-axis direction of the center of gravity CG of the entire vehicle 100, in the same manner as the center-of-gravity inertia value calculation unit 36. Further, the center-of-gravity inertia value calculation unit 36A, based on the position 100A of the center of gravity CG of the entire vehicle 100 and the information on the arrangement of each wheel stored in the vehicle specifications DB 34, calculates the distance t in the y-axis direction of each front and rear wheel with respect to CG. all , the inertia tensor J all , and the center of gravity CG of the entire vehicle 100 all of the position h in the z-axis direction CG to calculate. Further, the center-of-gravity inertia value calculation unit 36A, the position 100A of the center of gravity CG of the entire vehicle 100 all , and based on the information of the arrangement of each wheel stored in the vehicle specifications DB34, CG all for each front and rear wheels in the y-axis direction of the distance t land t r and CG all The distance l in the x - axis direction of the front and rear wheels with respect to CG f and l r are calculated.

[0087] The wheel load fluctuation estimation unit 40A, similar to the wheel load fluctuation estimation unit 40, calculates the distance (h all - h R in the z - axis direction between CG and the roll center h CG ). Then, the wheel load fluctuation estimation unit 40A uses the longitudinal acceleration G R , the lateral acceleration G xCG , the roll angular velocity P, the pitch angular velocity Q, the yaw angular velocity R, the roll angular acceleration P yCG , the pitch angular acceleration Q · , the yaw angular acceleration R · , the weight M of the entire vehicle 100 · , the inertia tensor J all , the position h of CG in the z - axis direction all , CG all , the calculated (h CG - h CG ), the distances t R , t all in the x and y - axis directions of each wheel with respect to CG l , t r , l f , l r , and the roll synthesis distribution α f , α r of the front and rear wheels to estimate the fluctuations ΔFL z , ΔFR z , ΔRL z , and ΔR z of each wheel load and the yaw moment N v according to equation (15).

[0088] <Second Embodiment> Next, the second embodiment will be described. First, the principle of the second embodiment will be explained. In the second embodiment, the case of estimating the wheel loads of a three - wheel forklift with two front wheels and one rear wheel will be described. Also, the pre - conditions are the same as those in the first embodiment.

[0089] In the case of a three-wheeled forklift, since the rear wheels are arranged at the center of the rear axle and do not contribute to the roll behavior but only to the pitch behavior, considering this, the formula (11) in the first embodiment is rewritten as the following formula (17).

[0090]

Equation

[0091] Also, when the formula (12) in the first embodiment is rewritten in the same manner as above, it becomes the following formula (18).

[0092]

Equation

[0093] Also, the description regarding the rear wheel load in the formula (13) (ΔRL z +ΔRR z ) is replaced with ΔR z and added to the formula (18), resulting in the following formula (19).

[0094]

Equation

[0095] As described above, in the case of a three-wheeled forklift as well, the load on each wheel can be estimated in the same manner as in the case of the four-wheeled forklift described in the first embodiment.

[0096] Next, the configuration of the wheel load estimation device according to the second embodiment will be described. In the wheel load estimation device according to the second embodiment, the same components as those in the wheel load estimation device 10 according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

[0097] As shown in FIG. 10, an IMU 112, a pressure sensor 114, and an encoder 116 are connected to the wheel load estimation device 210 according to the second embodiment. The wheel load estimation device 210 is installed at an arbitrary position of the vehicle (forklift).

[0098] As shown in FIG. 11, the wheel load estimation device 210 functionally includes a longitudinal acceleration acquisition unit 12, a lateral acceleration acquisition unit 14, a roll angular velocity acquisition unit 16, a pitch angular velocity acquisition unit 18, and a yaw angular velocity acquisition unit 20. Further, the wheel load estimation device 210 includes a payload acquisition unit 22, a payload position acquisition unit 24, and a lift height acquisition unit 26. Further, the wheel load estimation device 210 includes an angular acceleration calculation unit 32, a vehicle specification DB 34, a center of gravity inertia value calculation unit 236, a wheel load fluctuation estimation unit 240, and a wheel load calculation unit 242.

[0099] Similar to the center of gravity inertia value calculation unit 36 in the first embodiment, the center of gravity inertia value calculation unit 236 calculates the weight M of the entire vehicle 100 including the load 104 all , the inertia tensor J all , and the position h of the center of gravity CG of the entire vehicle 100 in the z-axis direction all . Further, the center of gravity inertia value calculation unit 236 calculates, based on the position 100A of the center of gravity CG of the entire vehicle 100 and the information on the arrangement of each wheel stored in the vehicle specification DB 34, the distances t in the y-axis direction from the front left and right wheels to the CG CG and t all , and the distances l in the x-axis direction from the front and rear wheels to the CG all and l l and t r and the distances l in the x-axis direction from the front and rear wheels to the CG all and l f and l r .

[0100] Similar to the wheel load fluctuation estimation unit 40 in the first embodiment, the wheel load fluctuation estimation unit 240 calculates the distance (h all - h R ) in the z-axis direction between the CG CG and the roll center h R . Then, the wheel load fluctuation estimation unit 240 calculates the longitudinal acceleration G xCG , the lateral acceleration G yCG , the roll angular velocity P, the pitch angular velocity Q, the yaw angular velocity R, the roll angular acceleration P · , the pitch angular acceleration Q · , the yaw angular acceleration R · , the weight M of the entire vehicle 100 all , and the inertia tensor J alland CG all The position h in the z-axis direction of CG and the calculated (h CG -h R ) and the distances t in the x- and y-axis directions of each wheel with respect to CG all are used to estimate the fluctuations ΔFL l , ΔFR r , l f , l r of each wheel load and the yaw moment N z by Equation (19). z and ΔR z and the yaw moment N v are estimated.

[0101] The wheel load calculation unit 242 calculates the fluctuations ΔFL z , ΔFR z , and ΔR z of each wheel load estimated by the wheel load fluctuation estimation unit 240 and the static loads FL z0 , FR z0 , and R z0 of each wheel stored in the vehicle specifications DB 34 to calculate the wheel loads FL z , FR z , and R z of each wheel. Then, the wheel load calculation unit 242 outputs the calculated wheel loads and the yaw moment N v estimated by the wheel load fluctuation estimation unit 240 as estimation results.

[0102] Since the hardware configuration of the wheel load estimation device 210 according to the second embodiment is the same as the hardware configuration of the wheel load estimation device 10 according to the first embodiment shown in FIG. 6, the description thereof is omitted.

[0103] Next, the operation of the wheel load estimation device 210 according to the second embodiment will be described. When the forklift starts running, the wheel load estimation process shown in FIG. 12 is executed in the wheel load estimation device 210. In the wheel load estimation process in the second embodiment, the same processes as those in the wheel load estimation process in the first embodiment are given the same step numbers, and detailed descriptions thereof are omitted.

[0104] After steps S10 and S12, in the next step S214, the center-of-gravity inertia value calculation unit 236 calculates the weight M of the entire vehicle 100 including the load 104 all , the inertia tensor J all , the position h in the z-axis direction of the center of gravity CG of the entire vehicle 100 all , the distances t in the y-axis direction of the left and right front wheels with respect to CG CG , CG all , the distances t in the y-axis direction of the left and right front wheels with respect to CG l and t r , and the distances l in the x-axis direction of the front and rear wheels with respect to CG all , and l f and l r .

[0105] Next, after steps S18 and S20, in the next step S224, the wheel load fluctuation estimation unit 240 calculates the distance (h all -h R ) in the z-axis direction between CG CG and the roll center h R . Then, the wheel load fluctuation estimation unit 240 uses G xCG , G yCG , P, Q, R, P · , Q · , R · , M all , J all , h CG , t l , t r , l f , l r calculated above and (h CG -h R ) to estimate the fluctuations ΔFL z , ΔFR z , and ΔR z of each wheel load and the yaw moment N v .

[0106] Next, in step S226, the wheel load calculation unit 242 uses the fluctuations ΔFL z , ΔFR z , and ΔR z of each wheel load estimated in the above step S224 and the static loads FL z0 , FR z0 , and R z0By adding them, each wheel load is calculated, and the yaw moment N estimated in the above step S224 v are output as estimation results together. Then, the process returns to step S12, and while the forklift is running, the processes of steps S12 to S226 are repeatedly executed. The output estimation results of the wheel loads are used for control such as forklift tipping prevention as in the first embodiment, and the output yaw moment is used for control such as torque vectoring.

[0107] As described above, according to the wheel load estimation device according to the second embodiment, the same effects as those of the first embodiment can be achieved even for a three-wheel forklift.

[0108] <Modification Example of the Second Embodiment> In the wheel load estimation device 210 according to the second embodiment, after calculating the yaw moment, in the wheel load fluctuation estimation unit 240, the fluctuation amount of each wheel load may be estimated. FIG. 13 shows an example of the functional configuration of a wheel load estimation device 210A according to a modification example of the second embodiment. Hereinafter, the differences between the wheel load estimation device 210A and the wheel load estimation device 210 will be described. Note that the wheel load estimation device 210A is also connected to the operation amount sensor 118 in the same manner as the wheel load estimation device 10 (see FIG. 5).

[0109] In the wheel load estimation device 210A, similar to the wheel load estimation device 10 according to the first embodiment, a tire longitudinal force acquisition unit 28, a tire lateral force acquisition unit 30A, and a yaw moment calculation unit 38A are included. The tire lateral force acquisition unit 30A receives the detection value output from the operation amount sensor 118, and inputs the longitudinal driving force, steering angle, vehicle speed, yaw rate, etc. based on the accelerator pedal depression amount and brake pedal depression amount indicated by the detection value into the predefined tire characteristics, thereby obtaining the tire lateral forces FL Fy 、FR Fy 、R Fy .

[0110] Here, FIG. 14 shows the yaw moment N in the case of a three-wheel forklift with two front wheels and one rear wheel, of the formula (1). vshows the acting force involved. Based on FIG. 14, the yaw moment calculation unit 38A calculates the yaw moment using equation (10) with (RL Fy +RR Fy ) replaced by R Fy .

[0111] Similar to the wheel load fluctuation estimation unit 240, the wheel load fluctuation estimation unit 240A calculates the distance (h all -h R ) in the z-axis direction between the CG CG and the roll center h R . Then, the wheel load fluctuation estimation unit 240A uses the longitudinal acceleration G xCG , the lateral acceleration G yCG , the roll angular velocity P, the pitch angular velocity Q, the yaw angular velocity R, the roll angular acceleration P · , the pitch angular acceleration Q · , the yaw angular acceleration R · , the weight M all of the entire vehicle 100, the inertia tensor J all , the position h all in the z-axis direction of the CG , the calculated (h CG -h CG ), the distances t R , t all in the x and y-axis directions of each wheel with respect to the CG l , t r , l f , l r , and the yaw moment N v to estimate the fluctuations ΔFL z , ΔFR z , and ΔR z of each wheel load using equation (17).

[0112] In addition, in each of the above embodiments, the case of obtaining the lift height from the rotation angle of the hoisting hydraulic motor detected by the encoder 116 has been described, but it is not limited thereto. For example, a wire may be provided on the fork, and the lift height may be obtained by measuring the change in the length of the wire during hoisting. Also, other values obtained by each acquisition unit are not limited to being obtained by the methods of the above embodiments, and may be obtained by other methods.

[0113] In addition, in each of the above embodiments, the case where the wheel load estimation device is mounted on a forklift has been described. However, the present invention is not limited to this, and it may be configured as an external device. In this case, the forklift is provided with a communication unit that transmits the detection values of the IMU 112, the pressure sensor 114, the encoder 116, and the operation amount sensor 118 to the wheel load estimation device. The wheel load estimation device configured as an external device may acquire various information transmitted from the communication unit of the forklift and estimate the wheel load by the same processing as in each of the above embodiments.

[0114] In addition, in each of the above embodiments, the case where the vehicle is a forklift has been described. However, the present invention can also be applied to vehicles that carry loads in various states and travel, such as trucks and the like.

[0115] Here, FIG. 15 shows an example of the wheel load estimation result when a three-wheel forklift is used to perform a forward right turn. In FIG. 15, the estimated values of each wheel load estimated by the formula (19) are compared with the measured values of the actual wheel load. As shown in FIG. 15, the estimated values and the measured values of the wheel load are substantially the same, and the wheel load can be estimated with high accuracy.

[0116] In addition, the results of confirming the effect of changing the inertia value according to the lift height will be described. FIG. 16 shows the results of estimating each wheel load by the formula (19) when a three-wheel forklift is run with a load of 800 kg, a lift height of 1.5 m, and reverse braking. FIG. 16(A) shows the case where the actual lift height is not considered and the inertia tensor J all is set to 0.2 m, and FIG. 16(B) shows the case where the inertia tensor J all is set to the same 1.5 m as the actual lift height. As shown in FIG. 12, when the wheel load is estimated with J all set to 0.2 m of the lift height, the estimation error is large. On the other hand, when the wheel load is estimated with J all set to the same lift height of 1.5 m as the actual, the estimation error is small. From this, the effect of changing the inertia value according to the lift height can be confirmed.

[0117] Next, FIG. 17 will explain the comparison of the estimated results of the wheel loads with and without considering the products of inertia when performing the same driving as in the case of FIG. 15. FIG. 16(A) shows the case without the product of inertia term, and FIG. 17(B) shows the case with the product of inertia term. In both cases, the lift height during the calculation of the inertia tensor J all is set to 1.5 m, and only the influence of the setting of the product of inertia term is compared. As shown in FIG. 17, the setting of the product of inertia term can reduce the estimation error of the wheel load. Note that even when there is no product of inertia term, the wheel load can be estimated with a certain degree of accuracy. Therefore, the present invention does not necessarily require considering the product of inertia. When not considering the product of inertia, in each of the above embodiments, the off-diagonal terms of the inertia tensor J all may be set to 0.

[0118] Note that in each of the above embodiments, the wheel load estimation process in which the CPU reads and executes software (program) may be executed by various processors other than the CPU. Examples of the processor in this case include a PLD (Programmable Logic Device) whose circuit configuration can be changed after manufacturing, such as an FPGA (Field-Programmable Gate Array), and a dedicated electric circuit which is a processor having a circuit configuration dedicated to executing a specific process, such as an ASIC (Application Specific Integrated Circuit). Also, the wheel load estimation process may be executed by one of these various processors, or may be executed by a combination of two or more processors of the same type or different types (for example, a combination of a plurality of FPGAs, and a combination of a CPU and an FPGA, etc.). Further, the hardware structure of these various processors is more specifically an electric circuit combining circuit elements such as semiconductor elements.

[0119] In addition, in each of the above embodiments, the aspect where the wheel load estimation program is pre-stored (installed) in the storage device has been described, but the present invention is not limited to this. The program may be provided in a form stored in a storage medium such as a CD-ROM, DVD-ROM, Blu-ray Disc, or USB memory. Further, the program may be in a form downloaded from an external device via a network.

Explanation of Signs

[0120] 10, 10A, 210, 210A Wheel load estimation device 12 Longitudinal and lateral acceleration acquisition unit 14 Lateral acceleration acquisition unit 16 Roll angular velocity acquisition unit 18 Pitch angular velocity acquisition unit 20 Yaw angular velocity acquisition unit 22 Payload acquisition unit 24 Payload position acquisition unit 26 Lift height acquisition unit 28 Tire longitudinal force acquisition unit 30, 30A Tire lateral force acquisition unit 32 Angular acceleration calculation unit 34 Vehicle specifications DB 36, 36A, 236 Center of gravity inertia value calculation unit 38, 38A Yaw moment calculation unit 40, 40A, 240, 240A Wheel load fluctuation estimation unit 42, 242 Wheel load calculation unit 44 Communication I / F 52 CPU 54 Memory 56 Storage device 58 Input device 60 Output device 62 Storage medium reading device 66 Bus 100 Entire vehicle 102 Vehicle body 104 Load 106 Fork 108 Outer mast 110 Inner mast 114 Pressure sensor 116 encoder 118 operation amount sensor

Claims

1. An acquisition unit that acquires the angular velocity, angular acceleration around three axes of a rigid body including an element that gives a variation to the center of gravity, the acceleration in the front-rear direction which is the traveling direction of the rigid body and the lateral direction which is the width direction of the rigid body, the weight of the element, and the position including the height of the element; A center-of-gravity inertia value calculation unit that calculates information regarding the center of gravity of the rigid body and calculates inertia values including the principal axes of inertia around the center of gravity of the rigid body; Based on the angular velocity, the angular acceleration, and the accelerations in the front-rear direction and the lateral direction acquired by the acquisition unit, and the information regarding the center of gravity of the rigid body and the inertia values calculated by the center-of-gravity inertia value calculation unit, a wheel load variation estimation unit that estimates the variation in the wheel load acting on each of a plurality of wheels that support the rigid body; A wheel load calculation unit that calculates the wheel load based on the variation in the wheel load estimated by the wheel load variation estimation unit and the static load acting on each of the wheels; A wheel load estimation device including the above.

2. The center-of-gravity inertia value calculation unit calculates the center-of-gravity positions of each of the rigid body including the element and each of the constituent parts based on the weight and position of the element acquired by the acquisition unit and the structure of each of the plurality of constituent parts that make up the rigid body, and uses the difference between the center-of-gravity position of the rigid body including the element and the center-of-gravity positions of each of the constituent parts to calculate the inertia value. The wheel load estimation device according to Claim 1.

3. The wheel load estimation device according to Claim 1 or Claim 2, wherein the center-of-gravity inertia value calculation unit calculates the inertia value further including the product of inertia.

4. The acquisition unit acquires the lateral force and the longitudinal force acting on the wheel, The wheel load variation estimation unit further uses the yaw moment around the center of gravity of the rigid body calculated based on the lateral force and the longitudinal force acquired by the acquisition unit to estimate the variation in the wheel load. The wheel load estimation device according to any one of Claims 1 to 3.

5. The wheel load variation estimation unit, under the constraint that the sum of the variations in the wheel load for each of the plurality of wheels is 0 and the relational expression between the roll synthesis distribution of the front and rear wheels and the load variation, estimates the yaw moment around the center of gravity of the rigid body together with the variation in the wheel load. The wheel load estimation device according to any one of Claims 1 to 3.

6. The wheel load estimation device according to any one of Claims 1 to 5, wherein the rigid body is a vehicle, and the element that gives a variation to the center of gravity is a load carried on the vehicle.

7. The vehicle is a forklift, and the load is loaded on forks that can operate vertically. The wheel load estimation device according to claim 6.

8. The information regarding the center of gravity of the rigid body includes the vertical distance between the center of gravity position of the rigid body and the roll center of the rigid body, the lateral position of the center of gravity position of the rigid body, and the lateral distance between each of the plurality of wheels and the center of gravity position of the rigid body. The wheel load estimation device according to any one of claims 1 to 7.

9. A wheel load estimation program for causing a computer to function as each part constituting the wheel load estimation device according to any one of claims 1 to 8.

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