Wheel load estimation device, vehicle, program, and wheel load estimation method

Abstract

The invention provides a wheel load estimation device and the like which can reduce the calculation load compared with the prior art when estimating the wheel load. According to one aspect of the present invention, there is provided a wheel load estimation device that estimates a wheel load applied to each wheel provided in a vehicle. The wheel load estimation device includes an acquisition unit, a calculation unit, and an estimation unit. The acquisition unit acquires a detection value output from the sensor as a parameter. The parameter is a parameter related to movement of the vehicle. The calculation unit calculates an inertia force generated in the vehicle on the basis of the parameter and the mass of the vehicle. The estimation unit estimates the wheel load on the basis of the inertia force and a predetermined estimation formula.

Description

Technical Field

[0001] The present invention relates to a wheel load estimation device, a vehicle, a program, and a wheel load estimation method. Background Art

[0002] Patent Document 1 discloses a method for estimating the current load of a vehicle.

[0003] This method will be described. A filter bank includes filters for different weight classifications, and each filter is equipped with a vehicle model for estimating the current mass of the vehicle. Based on vehicle data representing the current driving condition of the vehicle and filter parameters inherent to each weight classification, each filter provides a load estimation value as an estimation inherent to the filter of the current load of the vehicle. Patent Document 1 discloses the following formula (1).

[0004] [Mathematical Formula 1]

[0005]

[0006] Patent Document 2 discloses a method for determining a quantity representing the driving state of a vehicle.

[0007] This method will be described. In the case of a lateral inclination of the road surface and / or a roll motion of the vehicle, in order to ensure the stability or good quality of yaw torque control, it is necessary to identify the lateral inclination. This is performed by calculating the lateral inclination angle αq. In the case where the lateral inclination has been identified, the calculation device of the vehicle can be designed to operate roughly for the lateral inclination. The calculation of the lateral inclination angle is based on coordinate transformation. The value detected by a lateral acceleration measuring device fixed to the vehicle is associated with the value of the lateral acceleration related to the earth calculated from other sensor signals according to formula (2). Solving this formula yields the lateral inclination angle.

[0008] [Mathematical Formula 2]

[0009] a qm = a q ·cos(α q ) - g·sin(α q ) ...(2)

[0011] Prior Art Documents

[0012] Patent Documents

[0013] Patent Document 1: Japanese Patent Application Laid-Open No. 2011-505566

[0014] Patent Document 2: Japanese Patent Application Laid-Open No. 2002-515972 Summary of the Invention

[0015] Problems to be Solved by the Invention

[0016] However, in the methods disclosed in Patent Documents 1 and 2, complex calculations are required when estimating the wheel load.

[0017] In view of the above circumstances, the present invention provides a wheel load estimation device and the like that can reduce the calculation load compared with the prior art when estimating the wheel load.

[0018] Solutions for Solving the Problems

[0019] According to one aspect of the present invention, there is provided a wheel load estimation device for estimating the wheel load applied to each wheel of a vehicle. The wheel load estimation device includes an acquisition unit, a calculation unit, and an estimation unit. The acquisition unit acquires a detection value output from a sensor as a parameter. The parameter is a parameter related to the movement of the vehicle. The calculation unit calculates an inertial force generated in the vehicle based on the parameter and the mass of the vehicle. The estimation unit estimates the wheel load based on the inertial force and a predetermined estimation formula.

[0020] According to such an aspect, by applying the detection value output from the sensor to the wheel load estimation logic, the above problems can be solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram showing the configuration of the vehicle 600.

[0022] Figure 2 is a diagram showing the vehicle coordinate system with respect to the ground coordinate system.

[0023] Figure 3 is a diagram showing the posture angle of the vehicle coordinate system with respect to the ground coordinate system.

[0024] Figure 4 is a block diagram showing the hardware configuration of the vehicle 600.

[0025] Figure 5 is a block diagram showing the hardware configuration of the wheel load estimation device 100.

[0026] Figure 6 is a block diagram showing the functions implemented by the wheel load estimation device 100 (control unit 110).

[0027] Figure 7 is a schematic diagram schematically showing the difference in the inertia principal axis caused by the difference in the lifting height of the load 602.

[0028] Figure 8 is a diagram showing the pitch rotation center of the vehicle 600.

[0029] Figure 9 This is a diagram showing the roll center of the vehicle 600.

[0030] Figure 10 This is a diagram showing the longitudinal forces acting on the vehicle 600.

[0031] Figure 11 This is a diagram showing a schematic of the measurements by an IMU (acceleration sensor) during straight driving on an inclined road.

[0032] Figure 12 This is a diagram showing the lateral forces acting on the vehicle 600.

[0033] Figure 13 This is a diagram showing a schematic of the measurements by an IMU (acceleration sensor) during crossing driving on an inclined road.

[0034] Figure 14 This is an activity diagram showing the process of information processing executed by the wheel load estimation device 100 when the IMU 200 is used.

[0035] Figure 15 This is a block diagram showing the hardware configuration of the vehicle 600.

[0036] Figure 16 This is a block diagram showing the functions implemented by the wheel load estimation device 102 (control unit 110).

[0037] Figure 17 This is an activity diagram showing the process of information processing executed by the wheel load estimation device 102 when the wheel speed sensor 202, gyro sensor 204, and attitude angle sensor 206 are used.

[0038] Figure 18 This is a diagram showing the situation of a three-wheeled forklift equipped with an IMU 200 driving on an inclined road.

[0039] Figure 19 This is showing in Figure 18 a diagram of the result of estimating the wheel loads of the three-wheeled forklift.

[0040] Figure 20 This is a block diagram showing the functions implemented by the vehicle 600.

[0041] Figure 21 This is an activity diagram showing the process of information processing executed by the vehicle 600.

[0042] Figure 22 This is an activity diagram showing the process of information processing executed by the vehicle 600.

[0043] Figure 23 This is an activity diagram showing the process of information processing executed by the vehicle 600.

[0044] Figure 24 is an activity diagram showing the flow of information processing performed by vehicle 600.

[0045] Figure 25 is an activity diagram showing the flow of information processing performed by vehicle 600.

[0046] Figure 26 is an activity diagram showing the flow of information processing performed by vehicle 600.

[0047] Explanation of Reference Signs

[0048] 10: Lateral acceleration acquisition unit

[0049] 11: Wheel speed acquisition unit

[0050] 12: Three-axis angular velocity acquisition unit

[0051] 13: Pitch angular velocity acquisition unit

[0052] 15: Attitude angle acquisition unit

[0053] 16: Load payload acquisition unit

[0054] 18: Lift height acquisition unit

[0055] 20: Loading position acquisition unit

[0056] 21: Steering angle acquisition unit

[0057] 25: Wheel acceleration calculation unit

[0058] 26: Angular acceleration calculation unit

[0059] 27: Pitch angular acceleration calculation unit

[0060] 30: Center of gravity inertia value calculation unit

[0061] 31: Straight-ahead determination unit

[0062] 34: Wheel load variation estimation unit

[0063] 35: Wheel load variation estimation unit

[0064] 36: Wheel load calculation unit

[0065] 37: Wheel load calculation unit

[0066] 56: Center of gravity inertia value calculation unit

[0067] 100: Wheel load estimation device

[0068] 102: Wheel load estimation device

[0069] 110: Control Unit

[0070] 120: Storage Unit

[0071] 130: Display Unit

[0072] 140: Input Unit

[0073] 150: Communication Unit

[0074] 160: Communication Bus

[0075] 202: Wheel Speed Sensor

[0076] 204: Gyro Sensor

[0077] 206: Attitude Angle Sensor

[0078] 300: Pressure Sensor

[0079] 400: Encoder

[0080] 500: Operation Amount Sensor

[0081] 600: Vehicle

[0082] 600A: Center of Gravity Position

[0083] 601: Vehicle Body

[0084] 602: Load

[0085] 603: Fork

[0086] 604: Outer Mast

[0087] 605: Inner Mast

[0088] 710: Detection Unit

[0089] 720: Operation Unit

[0090] 730: Load Calculation Unit

[0091] 740: Center of Gravity Calculation Unit

[0092] 750: Tire Ground Load Calculation Unit

[0093] 760: Vehicle Speed Calculation Unit

[0094] 770: Attitude Angle Calculation Unit

[0095] 780: Judgment Unit

[0096] 790: Display Unit

[0097] 810: Drive Instruction Generation Unit

[0098] 820: Driving device

[0099] 830: Oil control valve

[0100] 840: Cargo handling device. Detailed implementation manners

[0101] Hereinafter, each embodiment of the present invention will be described with reference to the accompanying drawings. Various characteristic matters shown in the embodiments described below can be combined with each other. In addition, sometimes the embodiments are collectively referred to as the present embodiment.

[0102] However, the program for implementing the software that appears in the present embodiment can be provided as a computer-readable non-transitory recording medium, can also be provided in a manner that can be downloaded from an external server, and can also be provided in a manner that the function is implemented on a client terminal by starting the program through an external computer (so-called cloud computing).

[0103] In addition, in the present embodiment, a "part" may include, for example, a configuration that combines hardware resources implemented by a general circuit and information processing of software that can be specifically implemented by these hardware resources. In addition, in the present embodiment, various information is processed, and this information is represented by, for example, a physical value indicating a signal value of voltage / current, a high or low of a signal value that is a set of bits of a binary number composed of 0 or 1, or quantum superposition (so-called quantum bits), and communication / operation can be performed on a general circuit.

[0104] In addition, a general circuit refers to a circuit implemented by appropriately combining at least a circuit, circuitry, a processor, and a memory. That is, an application specific integrated circuit (ASIC), a programmable logic device (for example, a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA), etc.).

[0105] <First Embodiment>

[0106] First, the first embodiment of the present invention will be described.

[0107] 1. Hardware configuration

[0108] In the first section, the hardware configuration of the first embodiment will be described.

[0109] 1-1. Vehicle 600

[0110] Figure 1 is a schematic diagram showing the configuration of vehicle 600. Vehicle 600 is a vehicle configured to include a vehicle body 601, a load 602, a fork 603, an outer mast 604, and an inner mast 605. In Figure 1 it, at the center-of-gravity positions of the respective component parts, marks indicating the center-of-gravity positions are shown, and are denoted by reference numerals with "A" appended to the end of the reference numerals of the respective component parts. In addition, the size of the circle indicating the center-of-gravity position roughly represents the size of each component part. In addition, hereinafter, vehicle 600 including load 602 will also be referred to as "the entire vehicle 600".

[0111] Vehicle 600 includes elements that give changes to the center of gravity. Vehicle 600 travels with load 602 loaded on fork 603 that can be moved up and down. It is assumed that vehicle 600 is a forklift having four wheels in the front, rear, left, and right and supported independently by each wheel. In the first embodiment, the case of estimating the load on each wheel will be described. In the first embodiment, it is premised on measuring vehicle behavior including the longitudinal acceleration, lateral acceleration, roll angular velocity, pitch angular velocity, and yaw angular velocity of vehicle 600. In the first embodiment, it is a prerequisite that the mass of load 602, the lifting height, and the loading position of load 602 relative to fork 603 can be detected.

[0112] Figure 2 is a diagram showing the vehicle coordinate system with respect to the ground coordinate system. In the vehicle coordinate system, the longitudinal traveling direction of vehicle 600 is the x-axis, the lateral direction (width direction) is the y-axis, and the vertical direction is the z-axis. Figure 3 is a diagram showing the attitude angle of the vehicle coordinate system with respect to the ground coordinate system. The vehicle attitude angle is represented as the vehicle roll angle vehicle pitch angle θ, and vehicle yaw angle ψ, and is the rotation angle of each axis of the vehicle coordinate system with respect to the ground coordinate system. Each coordinate system is set as a right-handed system with the z-axis upward.

[0113] Figure 4 is a block diagram showing the hardware configuration of vehicle 600. Vehicle 600 includes a wheel load estimation device 100 and a detection unit. The detection unit can correspond to IMU 200, pressure sensor 300, encoder 400, and operation amount sensor 500. Here, IMU is an abbreviation for Inertial Measurement Unit (inertial measurement unit). Wheel load estimation device 100 is connected to the above-mentioned IMU 200, pressure sensor 300, encoder 400, and operation amount sensor 500.

[0114] Each detection unit detects information related to the movement of the vehicle 600. The wheel load estimation device 100 receives the information detected by each detection unit. The vehicle 600 can be equivalent to a vehicle that travels while loading the load 602 in various states, such as a forklift, a truck, a trailer, a bus, etc. In the present embodiment, the vehicle 600 is described as a rear-wheel-steering forklift. Here, the IMU 200, the pressure sensor 300, the encoder 400, and the operation amount sensor 500 will be further described.

[0115] The IMU 200 is composed of an acceleration sensor and a gyro sensor based on a strain type, a MEMS (Micro-Electro-Mechanical System) type, etc. The IMU 200 detects the acceleration in the three-axis directions of the vehicle coordinate system and the angular velocity around the three axes, and outputs the detection values. The IMU 200 is arranged at an arbitrary position of the vehicle 600.

[0116] The pressure sensor 300 is provided on the entire surface of the loading surface of the fork 603 on which the load 602 is loaded. The pressure sensor 300 is, for example, a sheet-like sensor, detects the pressure applied to each position of the loading surface, and outputs the detection values.

[0117] The encoder 400 detects the rotation angle of the unloading hydraulic motor for moving the inner mast 605 up and down, and outputs the detection values.

[0118] The operation amount sensor 500 respectively detects the accelerator pedal depression amount, the brake pedal depression amount, and the steering angle, and outputs the detection values.

[0119] 1-2. Wheel Load Estimation Device 100

[0120] Figure 5 It is a block diagram showing the hardware configuration of the wheel load estimation device 100. The wheel load estimation device 100 has a control unit 110, a storage unit 120, a display unit 130, an input unit 140, and a communication unit 150, and these components are electrically connected via a communication bus 160 inside the wheel load estimation device 100. Each component will be further described.

[0121] The control unit 110 processes / controls the overall operation related to the wheel load estimation device 100. The control unit 110 is, for example, a central processing unit (CPU) not shown in the figure. The control unit 110 realizes various functions related to the wheel load estimation device 100 by reading a prescribed program stored in the storage unit 120. That is, the information processing based on the software stored in the storage unit 120 is specifically realized by the control unit 110 which is an example of hardware, and can be executed as each functional unit included in the control unit 110. These contents are further described in detail in the second section. In addition, the control unit 110 is not limited to being single, and may also be implemented in such a manner that there are multiple control units 110 for each function. Alternatively, it may be a combination thereof.

[0122] The storage unit 120 stores various information required for the information processing of the wheel load estimation device 100. It can be implemented, for example, as a storage device such as a solid state drive (SSD) that stores various programs and the like related to the wheel load estimation device 100 executed by the control unit 110, or as a memory such as a random access memory (RAM) that stores information (parameters, arrangements, etc.) temporarily required for the operation of the program. Alternatively, it may be a combination thereof.

[0123] The display unit 130 may be included in the housing of the wheel load estimation device 100 or may be external. The display unit 130 displays a screen of a graphical user interface (GUI) that can be operated by the user. It can be equivalent to, for example, a CRT monitor, a liquid crystal display, an organic EL display, and a plasma display.

[0124] The input unit 140 may be included in the housing of the wheel load estimation device 100 or may be external. For example, the input unit 140 may be integrated with the display unit 130 and implemented as a touch panel. If it is a touch panel, the user can input tap operations, swipe operations, etc. Of course, a switch button, a mouse, a QWERTY keyboard, etc. may be used instead of the touch panel. That is, the input unit 140 receives operation inputs made by the user. This input is transmitted as a command signal to the control unit 110 via the communication bus 160. Then, the control unit 110 can execute prescribed control or arithmetic operations as needed.

[0125] Although the communication unit 150 is preferably a wired communication unit such as USB, IEEE 1394, Thunderbolt (registered trademark; Lightning), or wired LAN network communication, it may also include wireless LAN network communication, mobile communication such as 5G / LTE / 3G, Bluetooth (registered trademark; Bluetooth) communication, etc., as needed. That is, it is more preferably implemented as a collection of these multiple communication units. That is, the wheel load estimation device 100 communicates various information with each component via the communication unit 150.

[0126] 2. Functional configuration

[0127] In the second section, the functional configuration of the first embodiment will be described. As described above, the information processing based on the software stored in the storage unit 120 is specifically implemented by the control unit 110 as an example of hardware, and can be executed as each functional unit included in the control unit 110.

[0128] Figure 6 It is a block diagram showing the functions implemented by the wheel load estimation device 100 (control unit 110). Specifically, the wheel load estimation device 100 (control unit 110) includes a longitudinal and lateral acceleration acquisition unit 10, a three-axis angular velocity acquisition unit 12, a load acquisition unit 16, a lifting height acquisition unit 18, a loading position acquisition unit 20, an angular acceleration calculation unit 26, a centroid inertia value calculation unit 30, a wheel load change estimation unit 34, and a wheel load calculation unit 36. The vehicle specification DB (Database) 28 is provided as a read-only memory (ROM) and as a storage unit different from the storage unit 120 by the wheel load estimation device 100. The wheel load estimation device 100 estimates the wheel loads applied to each wheel of the vehicle 600.

[0129] In other words, the wheel load estimation device 100 (control unit 110) includes an acquisition unit (longitudinal and lateral acceleration acquisition unit 10, three-axis angular velocity acquisition unit 12, load acquisition unit 16, lifting height acquisition unit 18, loading position acquisition unit 20), a calculation unit (angular acceleration calculation unit 26, centroid inertia value calculation unit 30), and an estimation unit (wheel load change estimation unit 34). Moreover, the wheel load estimation device 100 includes the vehicle specification DB 28 as a storage unit, and the control unit 110 of the wheel load estimation device 100 includes a wheel load calculation unit 36.

[0130] The longitudinal and lateral acceleration acquisition unit 10 receives the detection values output from the IMU 200, and uses the acceleration S in the x-axis direction included in the detection values x and the angular velocities P, Q, R and angular accelerations around each axis and uses them as the longitudinal and lateral accelerations S at the center of gravity CG all of the vehicle 600xCG to obtain. Moreover, the longitudinal and lateral acceleration acquisition unit 10 receives the detection values output from the IMU 200, and uses the acceleration S in the y direction included in the detection values y and the angular velocities P, Q, R about each axis and the angular accelerations and obtains the lateral acceleration S at the center of gravity CG all of the vehicle 600 yCG to obtain.

[0131] The three-axis angular velocity acquisition unit 12 receives the detection values output from the IMU 200, obtains the angular velocity about the x axis included in the detection values as the roll angular velocity P, obtains the angular velocity about the y axis included in the detection values as the pitch angular velocity Q, and obtains the angular velocity about the z axis included in the detection values as the yaw angular velocity R.

[0132] The load acquisition unit 16 obtains the mass M of the load 602 loaded on the fork 603 by receiving the detection values output from the pressure sensor 300 and converting the detection values representing the pressure into mass α .

[0133] The lift height acquisition unit 18 receives the detection values output from the encoder 400, calculates the height of the fork 603 relative to the reference position (for example, the lowest position) based on the rotation angle of the unloading hydraulic motor represented by the detection values, and obtains this height as the lift height.

[0134] The load position acquisition unit 20 receives the detection values output from the pressure sensor 300, and obtains the position where the maximum detection value is detected on the loading surface of the fork 603 as the position of the load 602 loaded on the fork 603.

[0135] In this way, the acquisition unit obtains the detection values output from the respective sensors as parameters. The parameters are parameters related to the movement of the vehicle, and in the first embodiment, include at least one of the acceleration of the vehicle and the angular velocity and angular acceleration of the vehicle about the three axes.

[0136] The angular acceleration calculation unit 26 calculates the roll angular acceleration the pitch angular acceleration and the yaw angular acceleration

[0137] Various data related to the vehicle 600 are stored in the vehicle specification DB 28. Specifically, it stores the roll center h R , the mass M β , the static load FL of each wheel z0 , FR z0 , RLz0 , RR z0 , roll stiffness distribution α f , α r , the shape and mass m of each component part j Information including the structure and the arrangement of each wheel, etc.

[0138] The center-of-gravity inertia value calculation unit 30 adds the mass M of the load 602 obtained by the load acquisition unit 16 α and the mass M of the vehicle 600 stored in the vehicle specification DB28 β to calculate the mass M of the entire vehicle 600 including the load 602 all . Based on the information obtained by the load acquisition unit 16, the lift height acquisition unit 18, and the load position acquisition unit 20 respectively, the center-of-gravity inertia value calculation unit 30 calculates the position 602A of the center of gravity of the load 602. As a method for calculating the position 602A of the center of gravity of the load 602, for example, the method described in Japanese Patent Laid-Open No. 2020-93741 can be adopted.

[0139] Based on the position 602A of the center of gravity of the load 602 and the structure of each component part stored in the vehicle specification DB28, the center-of-gravity inertia value calculation unit 30 calculates the position 600A of the center of gravity CG of the entire vehicle 600 all , and the positions 601A, 603A, 604A, 605A of the centers of gravity of the component parts j. Further, the center-of-gravity inertia value calculation unit 30 calculates the differences (Δx all , Δy j , and Δz j ) in each axial direction between the position 600A of the center of gravity CG of the entire vehicle 600 and the positions 601A, 602A, 603A, 604A, 605A of the centers of gravity of the component parts j. In addition, the center-of-gravity inertia value calculation unit 30 uses the calculated Δx j , Δy j , and Δz j , and the mass m of the component part j stored in the vehicle specification DB28 j to calculate the inertia tensor J j . all

[0140] The center-of-gravity inertia value calculation unit 30 sets the position in the z-axis direction among the positions 600A of the center of gravity CG of the entire vehicle 600 calculated as h all (= z CG ). CG

[0141] In this way, the calculation unit calculates the inertial force generated in the vehicle based on the acquired parameters and the mass of the vehicle.

[0142] ​​The wheel load change estimation unit 34 calculates h calculated by the center of gravity inertia value calculation unit 30 CG and the position h of the roll center stored in the vehicle specification DB 28 R , calculates the distance in the z-axis direction between CG all and the roll center h R (h CG -h R ). Further, the wheel load change estimation unit 34 uses the longitudinal acceleration S xCG and the lateral acceleration S yCG acquired by the longitudinal and lateral acceleration acquisition unit 10, the roll angular velocity P, the pitch angular velocity Q, and the yaw angular velocity R acquired by the three-axis angular velocity acquisition unit 12, the roll angular acceleration pitch angular acceleration and the yaw angular acceleration the mass M of the entire vehicle 600 calculated by the center of gravity inertia value calculation unit 30 all , the inertia tensor J all and the position h of CG all in the z-axis direction, the calculated distance in the z-axis direction between CG CG and the roll center h all (h R -h CG ), and the distances t R in the x- and y-axis directions of each wheel with respect to CG all , t l , l r , l f , and the roll stiffness distribution α r , α f , α r to estimate the change amounts ΔFL z , ΔFR z , ΔRL z and ΔRR z .

[0143] The wheel load calculation unit 36 calculates the wheel loads FL z , FR z , RL z and RR z by adding the change amounts ΔFL z0 , ΔFR z0 , ΔRL z0 and ΔRR z0 estimated by the wheel load change estimation unit 34 to the static loads FL z , FR z , RL z and RR z, and output it as a presumption result.

[0144] In this way, the presumption unit presumes each wheel load based on the calculated inertial force and the specified presumption formula described in the third section.

[0145] 3. Principle

[0146] In the third section, the principle of the first embodiment will be described.

[0147] Different from a passenger car, a forklift travels while lifting a heavy load at various lifting heights. In addition, sometimes the loading position of the load also shifts in the y direction (the lateral direction of the forklift) relative to the center of gravity position of the forklift. Due to such a loading state of the load, the orientation 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 corresponding to the loading state of the load. Figure 7 is a schematic diagram schematically showing the difference in the principal axis of inertia caused by the difference in the lifting height of the load 602. As Figure 7 in (A), when the height of the lift on which the load is loaded is low, compared with the case where the height of the lift is high as Figure 7 in (B), the orientation of the principal axis of inertia changes.

[0148] In order to correspond to the difference in the loading state of the load as shown in Figure 7 , a six-degree-of-freedom model of the vehicle shown in Figure 2 and the following formulas (3) to (5) is used to describe the vehicle motion. In addition, formula (3) is an equation representing the rotational motion of the vehicle 600, formula (4) represents the translational motion of the vehicle 600, and formula (5) is an equation representing the update formula of the attitude angle of the vehicle coordinate system with respect to the ground coordinate system shown in Figure 3 .

[0149] [Mathematical formula 3]

[0150]

[0151]

[0152] In formulas (3) to (5), L v , M v , and N v are the torques (inertial forces) of roll, pitch, and yaw, respectively. In addition, U, V, and W are the velocities in the x, y, and z axis directions in the vehicle coordinate system. In addition, X v , Y v , and Z v are the longitudinal force, lateral force, and vertical force acting on the vehicle 600. The inertia tensor Jall Corresponding to the "inertia value" of the claim.

[0153] Regarding the setting of the inertia tensor J in Equation (3) all is described.

[0154] Equation (6) shows the composition of the inertia tensor J all In the right side of the following formula, the diagonal terms are the principal axes of inertia, and the off - diagonal terms are the products of inertia.

[0155] [Mathematical formula 4]

[0156]

[0157] In Equation (6), the subscript j is a variable that determines each component part, N is the total number of component parts, and m j is the mass of the component part j. The position (x all , y CG , z CG , z CG ) of the center of gravity CG of the entire vehicle 600 can be calculated using the mass of the load 602, the lifting height, and the loading position of the load 602 relative to the fork 603. In Equation (6), Δx j , Δy j and Δz j are the differences in the respective axial directions between the position 600A of the center of gravity CG of the entire vehicle 600 and the positions (x all , y j , z j , z j ) 601A, 602A, 603A, 604A, 605A of the center of gravity of the component part j, and are calculated by the following formula.

[0158] [Mathematical formula 5]

[0159] △x j = x j -x CG , Δy j = y j -y CG , Δz j = z j -z CG ...(7)

[0161] Figure 8 is a diagram showing the pitch rotation center of the vehicle 600. Figure 9 is a diagram showing the roll rotation center of the vehicle 600. J in Equation (6) A and J B are from Figure 8 and Figure 9The correction values of inertia when viewed from points A and B respectively are represented by the following formula. Here, Figure 8 Point A of Figure 8 is the pitch rotation center, and is set as the point where the vertical line passing through the center of gravity of the entire vehicle 600 when stationary on a flat road intersects the ground. In addition, Figure 9 Point B of Figure 9 is the roll rotation center, and is set as the point where the vertical line passing through the center of gravity of the entire vehicle 600 when stationary on a flat road intersects the roll center.

[0162] [Mathematical formula 6]

[0163] J A = M all ·(h CG - h R ) 2 ...(8)

[0165] J B = M all ·h CG 2 ...(9)

[0167] Figure 10 is a diagram showing the longitudinal forces acting on the vehicle 600. Use Figure 10 to explain the physical formula of the longitudinal force X v acting on the vehicle 600 when going straight downhill on an inclined road and there is a vehicle pitch angle θ due to the inclination angle Θ.

[0168] Based on Figure 10 , a physical formula showing the longitudinal force X v obtained from Equation (4) is shown. When the first column of Equation (4) is transformed,

[0169] The longitudinal force X v becomes the following formula.

[0170] [Mathematical formula 7]

[0171]

[0172] In Equation (10), is the longitudinal acceleration generated by vehicle behavior, and g·sinθ is the vehicle pitch angle component of gravitational acceleration. According to the physical formula of Equation (10), the longitudinal force on the inclined road is expressed by using, in addition to the acceleration components based on vehicle behavior V, W, and Q, R, the vehicle pitch angle θ component of gravitational acceleration.

[0173] Figure 11 is a diagram showing the measurement schematic diagram of the IMU (acceleration sensor) when driving straight on an inclined road. Figure 11(A) shows the case where the acceleration sensor tilts forward on an inclined road with a positive vehicle pitch angle. Figure 11 (B) of shows the deformation of the strain gauge at rest and during acceleration, taking the strain gauge type acceleration sensor as an example. According to Figure 11 (B), when at rest on an inclined road, due to the action of gravity, the Mass (mass block) of the sensor moves forward and the strain gauge becomes the stretching direction. When the vehicle is accelerating, due to the inertial force, the Mass of the sensor moves backward, and when the inertial force (acceleration) becomes larger, the strain gauge becomes the contracting direction. When the sign of the longitudinal acceleration detection of the vehicle during forward movement is positive, the sign of the gravitational acceleration g is negative. When the longitudinal acceleration detection value of the sensor is set to S xCG , according to Figure 11 the output sign of the strain gauge in (B), S xCG can be expressed by Equation (11).

[0174] [Mathematical formula 8]

[0175]

[0176] The content inside the parentheses on the right side of Equation (10) is the same as that on the right side of Equation (11). The longitudinal force X v uses S xCG and becomes Equation (12).

[0177] [Mathematical formula 9]

[0178]

[0179] Figure 12 is a diagram showing the lateral force acting on the vehicle 600. For the case where a vehicle roll angle Figure 12 is generated due to the tilt angle Θ when crossing the inclined road shown in , the physical formula for the lateral force Y v acting on the vehicle 600 is explained.

[0180] Based on Figure 12 , the physical formula for the lateral force Y v obtained according to Equation (4) is shown. When the second column of Equation (4) is deformed, the lateral force Y v becomes Equation (13).

[0181] [Mathematical formula 10]

[0182]

[0183] In Equation (13), is the lateral acceleration generated by vehicle behavior, is the roll angle of the gravitational acceleration Component. According to the physical formula of Equation (13), in the inclined road, in addition to using the acceleration components based on vehicle behavior U, W, and P, R, the lateral acceleration in the inclined road also uses the roll angle component of the vehicle of the gravitational acceleration to represent.

[0184] Figure 13 is a diagram showing the measurement of an IMU (acceleration sensor) when driving across an inclined road. Figure 13 (A) of shows the case where the acceleration sensor is tilted laterally due to the inclined road, Figure 13 (B) of shows the deformation of the strain gauge at rest and during a left turn. According to Figure 13 (B), when at rest on the inclined road, due to the action of gravity, the Mass of the sensor tilts to the right direction of the paper surface, and the strain gauge becomes the stretching direction. During a left turn, due to the inertial force, the Mass of the sensor further tilts to the right direction of the paper surface, and the strain gauge becomes the stretching direction as in the case of rest. When the sign of the lateral acceleration detection during a left turn is positive, the sign of the gravitational acceleration g is also positive. When the lateral acceleration detection value of the sensor is set as SyCG, according to Figure 13 the output sign of the strain gauge in (B), SyCG can be represented by Equation (14).

[0185] [Mathematical formula 11]

[0186]

[0187] The content in the parentheses on the right side of Equation (13) is the same as that on the right side of Equation (14), and the lateral force Y v uses SyCG and becomes Equation (15).

[0188] [Mathematical formula 12]

[0189]

[0190] According to Equation (15), the lateral acceleration SyCG of the IMU200 includes the roll angle of the vehicle and the pitch angle of the vehicle. Similar to the flat road, in the inclined road, the lateral force Y all can also be calculated by the product of the mass M yCG of the entire vehicle 600 and the lateral acceleration S v .

[0191] In wheel load estimation, it is necessary to calculate the moments L and M of the inertial force based on the longitudinal force X v and the lateral force Y v . According to Figure 10 and Figure 12 , noting that due to the inertial force of the lateral force Y v , the roll angular acceleration Increases due to the inertial force of the front and rear force X v and the pitch angular acceleration To reduce this situation, the moment L about point A and the moment M about point B become equations (16) and (17) according to equations (8) and (10).

[0192] [Mathematical formula 13]

[0193] L = Y v ·(h CG - h R ) = M all ·S yCG ·(h CG - h R ) ...(16)

[0195] [Mathematical formula 14]

[0196] M = -X v ·h CG = -M all ·S xCG ·h CG ...(17)

[0198] The roll moment L of equation (3) v is expressed by equation (18) using equation (16).

[0199] [Mathematical formula 15]

[0200] L v = L + (ΔFL z + ΔRL z )·t l - (ΔFR z + ΔRR z )·t r

[0201] = M all ·S yCG ·(h CG - h R ) + (ΔFL z + ΔRL z )·t l - (ΔFR z + ΔRR z )·t r ...(18)

[0203] The pitch moment M of equation (3) v is expressed by equation (19) using equation (17).

[0204] [Mathematical formula 16]

[0205] M v = M - (ΔFL z + ΔFR z )·l f +(ΔRL z + ΔRR z )·l r

[0206] = -M all ·S xCG ·h CG -(ΔFL z + ΔFR z )·l f +(ΔRL z + ΔRR z )·l r ...(19)

[0208] When the roll rigidities of the front and rear wheels are expressed as a f ( = k r / (k f + k f )) and a f ( = k r / (k r + k r )) using the vertical rigidities k f and k r of the front and rear wheels, Equation (20) holds between the change amounts of the wheel loads and the roll rigidity distribution at each wheel.

[0209] [Mathematical formula 17]

[0210] a r ·(ΔFL z - ΔFR z ) + a r ·(-ΔRL z + ΔRR z ) = 0 ...(20)

[0212] Regarding the sum of the changes in the wheel loads at each wheel, Equation (21) holds.

[0213] [Mathematical formula 18]

[0214] ΔFL z + ΔFR z + ΔRL z + ΔRR z = 0 ...(21)

[0216] It is assumed that the angular velocities (P, Q, and R) of roll, pitch, and yaw, as well as the longitudinal acceleration and lateral acceleration at the center of gravity CG of the entire vehicle 600, can be obtained through the IMU 200. all In addition, it is assumed that and are calculated by approximating the differentials of P, Q, and R measured at each sampling. In this case, in Equation (3), the wheel load variation and the yaw moment N v become unknown parameters. When using Equations (18) to (21) to represent Equation (3), the unknown parameters including the wheel load variation can be estimated through Equation (22).

[0217] [Mathematical formula 19]

[0218]

[0219] In Equation (22), i represents the sampling scale, and the -1 in the upper right corner of the first term on the right side represents the inverse matrix. The variation amounts ΔFL z , ΔFR z , ΔRL z and ΔRR z of each wheel load, and the static loads FL z0 , FR z0 , RL z0 and RR z0 stored in the vehicle specification DB 28 are added together to calculate the wheel loads FL z , FR z , RL z and RR z .

[0220] In addition, in Equation (22), J all * is Equation (23) obtained by transforming Equation (6).

[0221] [Mathematical formula 20]

[0222]

[0223] 4. Information processing method

[0224] In the fourth section, the information processing method of the aforementioned wheel load estimation device 100 will be described.

[0225] Figure 14 is an activity diagram showing the process of information processing executed by the wheel load estimation device 100 when using the IMU 200. Hereinafter, each activity of this activity diagram will be described.

[0226] The control unit 110 obtains from the vehicle specification DB28 information including the roll center h R , the mass M β , the static load FL of each wheel z0 , FR z0 , RL z0 , RR z0 , the shapes and masses m of the respective constituent parts j , information including the structure, the arrangement of each wheel, and the roll stiffness distribution α f , α r (Activity A110).

[0227] For example, in Activity A110, the following two-stage information processing is performed. (1) The control unit 110 reads out each piece of information stored in the vehicle specification DB28. (2) The control unit 110 stores (holds) each piece of this information in the storage unit 120.

[0228] Next, the control unit 110 obtains the mass M of the load 602 loaded on the fork 603 α and the loading position of the load 602, and also obtains the lifting height (Activity A120).

[0229] In Activity A120, for example, the following two-stage information processing is performed. (1) The control unit 110 obtains the mass M of the load 602 α , the loading position of the load 602, and the lifting height based on the detection values of the pressure sensor 300 and the encoder 400. (2) The control unit 110 stores the information on the mass M of the load 602 α , the loading position of the load 602, and the lifting height in the storage unit 120.

[0230] Next, the control unit 110 calculates the mass M of the entire vehicle 600 all and the position 6000A of the center of gravity CG all , the positions 601A, 602A, 603A, 604A, 605A of the centers of gravity of the constituent parts j, and further calculates the inertia tensor J all (Activity A130).

[0231] In Activity A130, for example, the following three-stage information processing is performed. (1) The control unit 110 reads out each piece of information obtained in Activities A110 and A120 from the storage unit 120. (2) The control unit 110 performs a calculation process to calculate the mass M of the entire vehicle 600 all and the position 600A of the center of gravity CG all , the positions 601A, 602A, 603A, 604A, 605A of the centers of gravity of the constituent parts j, and the inertia tensor J all. (3) The control unit 110 stores the calculated information in the storage unit 120.

[0232] In other words, the calculation unit calculates the center of gravity position of the vehicle 600. The calculation unit calculates the inertia value related to the inertia at the center of gravity position 600A of the vehicle 600 based on the center of gravity position 600A of the vehicle 600 and the mass M of the vehicle 600 all , and through activities A110 and A120, the control unit 110 calculates the mass M of the entire vehicle 600 including the load 602 all , the inertia tensor J all , the position h in the z-axis direction of the center of gravity CG of the entire vehicle 600 all , the distance t in the y-axis direction between the left and right wheels relative to CG CG , and t all , and the distance l in the x-axis direction between the front and rear wheels relative to CG l and l r , and the distance l in the x-axis direction between the front and rear wheels relative to CG all , and l f and l r .

[0233] Next, the control unit 110 acquires the roll angular velocity P, the pitch angular velocity Q, and the yaw angular velocity R (activity A140).

[0234] In activity A140, for example, the following two-stage information processing is performed. (1) The control unit 110 acquires the roll angular velocity P, the pitch angular velocity Q, and the yaw angular velocity R based on the detection values of the IMU 200. (2) The control unit 110 stores the information of P, Q, and R in the storage unit 120.

[0235] Next, the control unit 110 calculates the roll angular acceleration the pitch angular acceleration and the yaw angular acceleration respectively (activity A150).

[0236] In activity A150, for example, the following three-stage information processing is performed. (1) The control unit 110 reads out the information of the roll angular velocity P, the pitch angular velocity Q, and the yaw angular velocity R stored in the storage unit 120. (2) The control unit 110 performs a calculation process based on approximate differentiation to calculate the roll angular acceleration the pitch angular acceleration and the yaw angular acceleration (3) The control unit 110 stores the calculated information in the storage unit 120.

[0237] Next, the control unit 110 acquires S xCG , S yCG as the longitudinal acceleration and the lateral acceleration of the center of gravity position (activity A160).

[0238] In activity A160, for example, the following four-phase information processing is performed. (1) The control unit 110 obtains the longitudinal acceleration S based on the detection values of the IMU 200. x , the lateral acceleration S y . (2) The control unit 110 reads out the roll angular velocity P, pitch angular velocity Q, yaw angular velocity R, roll angular acceleration , pitch angular acceleration , and yaw angular acceleration stored in the storage unit 120. (3) The control unit 110 calculates the relative distances Δx sf , y sf , z sf between the mounting position (x all ) of the IMU 200 on the vehicle 600 in the vehicle coordinate system stored in the vehicle specification DB 28 and the center of gravity CG sf of the vehicle 600, Δy sf , and Δz sf . (4) Based on the obtained accelerations S x , S y , angular velocities P, Q, R, angular accelerations , and relative distances Δx sf , Δy sf , Δz sf , the longitudinal acceleration S xCG and lateral acceleration S yCG of the center of gravity position are calculated, and the information of S xCG , S yCG is stored in the storage unit 120.

[0239] Next, the control unit 110 estimates the change amounts ΔFL z , ΔFR z , ΔRL z , and ΔRR z of each wheel load (activity A170).

[0240] In activity A170, for example, the following four-phase information processing is performed. (1) The control unit 110 performs a calculation process to calculate the distance in the z-axis direction between the CG all and the roll center h R (h CG - h R ). (2) The control unit 110 reads out S xCG , S yCG , P, Q, R, , M all , J all , h CG , N v , t l , tr and l f and l r and α f and α r . (3) The control unit 110 estimates the change amounts ΔFL z , ΔFR z , ΔRL z and ΔRR z of the loads on each wheel based on the information calculated in (1) and the respective information read in (2). z (4) The control unit 110 stores the change amounts ΔFL z , ΔFR z , ΔRL z and ΔRR of the loads on each wheel in the storage unit 120.

[0241] In other words, the estimation unit estimates the wheel loads applied to each wheel of the vehicle 600 based on the inertia value related to the inertia at the center of gravity position of the vehicle 600, at least one of the angular velocity and angular acceleration of the vehicle 600 about the three axes, the inertial force generated in the vehicle 600, and a prescribed estimation formula.

[0242] Next, the control unit 110 calculates the loads on each wheel and outputs them as the estimation results of the loads on each wheel (operation A180).

[0243] In operation A180, for example, the following four-stage information processing is performed. (1) The control unit 110 reads the change amounts ΔFL z , ΔFR z , ΔRL z and ΔRR z of the loads on each wheel stored in the storage unit 120. (2) The control unit 110 reads the static loads FL z0 , FR z0 , RL z0 , RR z0 of each wheel stored in the storage unit 120. (3) The control unit 110 performs a calculation process to calculate the loads on each wheel. (4) The control unit 110 outputs the calculated loads on each wheel.

[0244] Next, the control unit 110 transfers to the process of operation A120. That is, while the vehicle 600 is in motion, the control unit 110 repeatedly performs the processes from operation A120 to operation A180. The output estimation results of the wheel loads are used for control such as preventing the vehicle 600 from tipping over.

[0245] In other words, the acquisition unit continuously acquires the parameters output from the IMU 200. The calculation unit continuously calculates the inertial force generated in the vehicle 600 based on the continuously acquired parameters and the mass of the vehicle 600. The estimation unit continuously estimates the wheel loads applied to the respective wheels provided in the vehicle 600 in time series based on the continuously calculated inertial force and a prescribed estimation formula.

[0246] <Second Embodiment>

[0247] Next, a second embodiment of the present invention will be described.

[0248] 5. Hardware Configuration

[0249] In Section 5, the hardware configuration of the second embodiment will be described.

[0250] In Section 5, a three-wheeled forklift is targeted. Hereinafter, the differences in the hardware configuration related to a four-wheeled forklift from the first embodiment will be described, and the description of the same content will be appropriately omitted.

[0251] The configuration of the vehicle 600 is substantially the same as that of the Figure 1 first embodiment, but the difference is that the rear wheels are one wheel. In the second embodiment, as an example of the vehicle 600 including an element that gives a change to the center of gravity, the case of estimating the wheel loads of a forklift having two front left and right wheels and one rear wheel will be described.

[0252] 6. Functional Configuration

[0253] In Section 6, the functional configuration of the second embodiment will be described.

[0254] The wheel load change estimation unit 34 uses the distances t l 、t r in the y-axis direction of the front left and right wheels and the distances l f 、l r in the x-axis direction of the front and rear wheels to estimate the change amounts ΔFL z 、ΔFR z and ΔR z of the respective wheel loads.

[0255] The wheel load calculation unit 36 calculates the respective wheel loads FL z 、ΔFR z by adding the change amounts ΔFL z 、ΔFR of the front wheel loads estimated by the wheel load change estimation unit 34 z0 、FR z0 and the change amount ΔR of the rear wheel load z0 to the static loads FL z 、FR z and Rz , and output it as the presumptive result.

[0256] 7. Principle

[0257] In Section 7, the principle of the second embodiment is described.

[0258] Noting that in a three-wheel forklift, one of the rear wheels is arranged at the center of the vehicle, the roll moments L v and pitch moments M v become Expressions (24) and (25), respectively.

[0259] [Mathematical formula 21]

[0260] L v = L + ΔFL z ·t l –ΔFR z = M all ·S yCG ·(h CG -h R ) + ΔFL z ·t l -FR z ·t r ...(24)

[0262] [Mathematical formula 22]

[0263] M v = M - (△FL z +ΔFR z )·l f +ΔR z ·l r

[0264] = M all ·S xCG ·h CG -(ΔFL z +ΔFR z )·l f +ΔR z ·l r ...(25)

[0266] In addition, the sum of the wheel load variations of each wheel is the same as Expression (21) and becomes Expression (26).

[0267] [Mathematical formula 23]

[0268] ΔFL z +ΔFR z +ΔR z = 0 ...(26)

[0270] In a three - wheel forklift, there are three objects for which the wheel load is estimated. Based on three balance equations of the roll moment, pitch moment, and the sum of wheel load variations, the wheel load variations of the three wheels can be calculated. The roll stiffness distribution a f , a r is no longer required. According to equations (24) to (26), when equation (22) is rewritten for use in a three - wheel forklift, it becomes equation (27).

[0271] [Mathematical formula 24]

[0272]

[0273] By adding the wheel load variations obtained from equation (27) to the static loads FL z0 , FR z0 and R z0 stored in the vehicle specification DB28, the wheel loads FL z , FR z and R z are calculated. Among them, in equation (27), J all * is equation (28) obtained by transforming equation (6).

[0274] [Mathematical formula 25]

[0275]

[0276] 8. Information processing method

[0277] In Section 8, regarding the information processing method of the wheel load estimation device 100 related to the second embodiment, the differences from the first embodiment will be emphasized.

[0278] The activity diagram showing the information processing flow executed by the wheel load estimation device 100 of the second embodiment using the IMU200 is omitted because it is Figure 14 the same. However, since the object changes from a four - wheel forklift to a three - wheel forklift, the processing content is slightly different. Hereinafter, the differences will be described, and the description of the same content will be appropriately omitted.

[0279] The control unit 110 obtains from the vehicle specification DB28 information including the roll center h R , mass M β , the static loads FL z0 , FR z0 of the front wheels, and the static load R z0 of the rear wheel, the shape of each component part, mass m j , including the structure and the configuration of each wheel (activity A110).

[0280] The control unit 110 calculates the mass M of the entire vehicle 600 including the load 602 all , the inertia tensor J all , the center of gravity CG of the entire vehicle 600 all in the z-axis direction at position h CG , relative to CG all the y-axis direction distance t of the front left and right wheels l and t r , and relative to CG all the x-axis direction distance l of the front and rear wheels f and l r (Activity A130).

[0281] The control unit 110 estimates the change amount ΔFL of each wheel load z , ΔFR z and ΔR z (Activity A170).

[0282] In Activity A170, for example, the following four-stage information processing is performed. (1) The control unit 110 performs a calculation process to calculate the distance in the z-axis direction between CG all and the roll center h R (h CG -h R ). (2) The control unit 110 reads S xCG , S yCG , P, Q, R, M all , M all , J all , h CG , N v , t l , t r , l f , l r stored in the storage unit 120. (3) The control unit 110 estimates the change amount ΔFL of each wheel load based on the information calculated in (1) and each information read in (2) z , ΔFR z and ΔR z . (4) The control unit 110 stores the change amount ΔFL of each wheel load z , ΔFR z and ΔR z into the storage unit 120. In other words, the estimation unit estimates the wheel loads applied to each wheel of the vehicle 600 based on the inertia values related to the inertia at the center of gravity position of the vehicle 600, at least one of the angular velocity and angular acceleration of the vehicle 600 around the three axes, the torque acting on the vehicle 600, and a prescribed estimation formula.

[0283] Next, the control unit 110 calculates the load on each wheel and outputs it as an estimation result of the load on each wheel (operation A180).

[0284] In operation A180, for example, the following four-stage information processing is performed. (1) The control unit 110 reads out the amount of change ΔFL in the load on each wheel stored in the storage unit 120 z , ΔFR z and ΔR z . (2) The control unit 110 reads out the static load FL on each wheel stored in the storage unit 120 z0 , FR z0 and R z0 . (3) The control unit 110 performs a calculation process to calculate the load on each wheel. (4) The control unit 110 outputs the calculated load on each wheel.

[0285] <Third Embodiment>

[0286] Next, a third embodiment of the present invention will be described.

[0287] Regarding the estimation of the wheel load in a driving state where the vehicle is traveling straight on an inclined road and the up-and-down movement of the vehicle is small, the wheel load can be estimated by a wheel speed sensor, a gyro sensor for one axis, and a posture angle sensor. The straight-ahead state is detected based on the steering angle, for example. In the third embodiment, it is assumed that a four-wheel or three-wheel forklift is the object, and the sum of the wheel loads of the left and right wheels is estimated for both the front wheels and the rear wheels. Hereinafter, the differences from the first and second embodiments will be described, and the description of the same content will be omitted as appropriate.

[0288] 9. Hardware Configuration

[0289] In Section 9, the hardware configuration of the third embodiment will be described. In the third embodiment, it is premised on measuring the vehicle behavior including the wheel speed, pitch angular velocity, and vehicle pitch angle of the vehicle 600, and the steering angle.

[0290] Figure 15 is a block diagram showing the hardware configuration of the vehicle 600. The vehicle 600 includes a wheel load estimation device 102 and a detection unit. The detection unit can correspond to a wheel speed sensor 202 that measures the wheel speed of any one or both of the front left and right wheels, a gyro sensor 204 that measures the pitch angular velocity Q, a posture angle sensor 206 that measures the vehicle pitch angle θ, a pressure sensor 300, an encoder 400, and an operation amount sensor 500. The wheel load estimation device 102 is connected to the above-mentioned wheel speed sensor 202, gyro sensor 204, posture angle sensor 206, pressure sensor 300, encoder 400, and operation amount sensor 500.

[0291] The wheel speed sensor 202 is composed of an electromagnetic pickup, a Hall sensor, etc., and outputs a detected value of the rotational speed of the wheel.

[0292] The gyro sensor 204 is a MEMS-based angular velocity sensor, and outputs a detected value of the angular velocity about the y-axis in the vehicle coordinate system. The gyro sensor 204 is arranged at an arbitrary position of the vehicle 600.

[0293] The attitude angle sensor 206 is composed of an IMU, etc., and outputs a detected value of the vehicle attitude angle.

[0294] 10. Functional composition

[0295] In the tenth section, the functional composition of the third embodiment will be described.

[0296] Figure 16 It is a block diagram showing the functions realized by the wheel load estimation device 102 (control unit 110). Specifically, the wheel load estimation device 102 (control unit 110) includes: a wheel speed acquisition unit 11, a pitch angular velocity acquisition unit 13, an attitude angle acquisition unit 15, a loaded load acquisition unit 16, a lift height acquisition unit 18, a loading position acquisition unit 20, a steering angle acquisition unit 21, a wheel acceleration calculation unit 25, a pitch angular acceleration calculation unit 27, a center of gravity inertia value calculation unit 30, a straight-ahead determination unit 31, a wheel load variation estimation unit 34, and a wheel load calculation unit 36. The vehicle specification DB28 is provided as a read-only memory (ROM) and as a storage unit different from the storage unit 120 by the wheel load estimation device 102.

[0297] In other words, the wheel load estimation device 102 (control unit 110) includes acquisition units (wheel speed acquisition unit 11, pitch angular velocity acquisition unit 13, attitude angle acquisition unit 15, loaded load acquisition unit 16, lift height acquisition unit 18, loading position acquisition unit 20, steering angle acquisition unit 21), calculation units (wheel acceleration calculation unit 25, pitch angular acceleration calculation unit 27, and center of gravity inertia value calculation unit 30), an estimation unit (wheel load variation estimation unit 34), and a determination unit (straight-ahead determination unit 31). Moreover, the wheel load estimation device 102 includes the vehicle specification DB28 as a storage unit, and the control unit 110 of the wheel load estimation device 102 includes a wheel load calculation unit 36.

[0298] The wheel speed acquisition unit 11 receives the detected value output from the wheel speed sensor 202 and acquires it as the wheel speed U. When the wheel speed sensors are assembled on the left and right wheels, the average of the detected values of both is acquired as the wheel speed U.

[0299] The pitch angular velocity acquisition unit 13 receives the detection value output from the gyro sensor 204, and acquires the angular velocity of the vehicle 600 around the y-axis as the pitch angular velocity Q.

[0300] The posture angle acquisition unit 15 receives the detection value output from the posture angle sensor 206, and acquires it as the vehicle pitch angle θ of the vehicle 600 around the y-axis.

[0301] In this way, the acquisition unit acquires the detection values output from the respective sensors as parameters. The parameters include at least one of the wheel speed and the first wheel acceleration of the vehicle, at least one of the angular velocity and the angular acceleration of the vehicle around the pitch axis, and the posture angle of the vehicle around the pitch axis.

[0302] Various data related to the vehicle 600 are stored in the vehicle specification DB 28. Specifically, it stores the mass M β , the sum F of the static loads of the front, rear, left, and right wheels z0 , R z0 , the shapes of the respective components, the mass m j , and information including the structure and the arrangement of the respective wheels.

[0303] The wheel acceleration calculation unit 25 calculates the wheel acceleration by approximate differentiation of the wheel speed U acquired by the wheel speed acquisition unit 11.

[0304] The straight-ahead determination unit 31 determines whether the vehicle is traveling straight by comparing the steering angle acquired by the steering angle acquisition unit 21 with a threshold value.

[0305] When it is determined by the straight-ahead determination unit 31 that the vehicle is going straight, the wheel load change estimation unit 35 uses h calculated by the center of gravity inertia value calculation unit 30 CG , the wheel acceleration calculated by the wheel acceleration calculation unit 25 the pitch angular acceleration calculated by the pitch angular acceleration calculation unit 27 , the vehicle pitch angle θ acquired by the posture angle acquisition unit 15, the gravitational acceleration g, the mass M of the entire vehicle 600 calculated by the center of gravity inertia value calculation unit 30 all , the inertia tensor J all , the distance l in the x-axis direction of each wheel with respect to the center of gravity CG all , l f , l r , to estimate the load change amounts ΔF z , ΔR z .

[0306] The wheel load calculation unit 36 calculates the front and rear wheel load change amounts ΔF z , ΔR zThe sum of the static loads F and R of the front and rear wheels stored in the vehicle specification DB28 is used to calculate the loads F and R of the front and rear wheels, and the result is output as an estimation result. z0 , R z0 Based on the sum of the static loads F and R of the front and rear wheels stored in the vehicle specification DB28, the loads F and R of the front and rear wheels are calculated, and the result is output as an estimation result. z , R z , and the result is output as an estimation result.

[0307] In this way, when the wheel acceleration (the first wheel acceleration) is included as the acquired parameter, the calculation unit calculates the second wheel acceleration obtained by correcting the wheel acceleration based on the first wheel acceleration and the vehicle pitch angle θ (posture angle). The second wheel acceleration is obtained by correcting the first wheel acceleration by applying the direction component related to the inclination direction of the vehicle 600 calculated from the parameter and the component of the gravitational acceleration to the first wheel acceleration . Then, the calculation unit calculates the inertial force generated by the vehicle 600 based on the second wheel acceleration and the mass of the vehicle 600. (the first wheel acceleration) is included as the acquired parameter, the calculation unit calculates the second wheel acceleration obtained by correcting the wheel acceleration based on the first wheel acceleration and the vehicle pitch angle θ (posture angle). The second wheel acceleration is obtained by correcting the first wheel acceleration by applying the direction component related to the inclination direction of the vehicle 600 calculated from the parameter and the component of the gravitational acceleration to the first wheel acceleration . Then, the calculation unit calculates the inertial force generated by the vehicle 600 based on the second wheel acceleration and the mass of the vehicle 600. corrected (the second wheel acceleration). The second wheel acceleration is obtained by correcting the first wheel acceleration by applying the direction component related to the inclination direction of the vehicle 600 calculated from the parameter and the component of the gravitational acceleration to the first wheel acceleration . Then, the calculation unit calculates the inertial force generated by the vehicle 600 based on the second wheel acceleration and the mass of the vehicle 600. (the first wheel acceleration) to correct the first wheel acceleration. Then, the calculation unit calculates the inertial force generated by the vehicle 600 based on the second wheel acceleration and the mass of the vehicle 600.

[0308] 11. Principle

[0309] In Section 11, the principle of the third embodiment is described.

[0310] When the approximate differential value of the wheel speed U acquired by the sensor is set to Since the up and down movement is small during straight running and V≈0, W≈0, P≈0, R≈0, according to Equation (11), the front and rear acceleration S xCG becomes Equation (29).

[0311] [Mathematical formula 26]

[0312]

[0313] The front and rear force X v According to Equations (10) and (29), it becomes Equation (30).

[0314] [Mathematical formula 27]

[0315]

[0316] According to Equation (30), when calculating the front and rear force X v during the use of the wheel speed sensor, the measured value of the vehicle pitch angle θ is used. The moment M around point B is expressed by Equation (31) using Equation (30).

[0317] [Mathematical formula 28]

[0318] M = -X v ·h CG = -Mall ·[S xCG -g·sinθ]·h CG ...(31)

[0320] According to the sum of the wheel load changes ΔF of the front left and right wheels z and the sum of the wheel load changes ΔR of the rear left and right wheels z , Equation (26) becomes Equation (32).

[0321] [Mathematical formula 29]

[0322] △F z +ΔR z =0 ...(32)

[0324] Using Equation (31) and Equation (32), similar to Equation (22) and Equation (27), the sum of the wheel load changes ΔF z and ΔR z of the left and right wheels of the front and rear wheels can be calculated by Equation (33).

[0325] [Mathematical formula 30]

[0326]

[0327] J in Equation (33) all(2，2) represents the element J in the second row and second column of Equation (6) yy .

[0328] 12. Information processing method

[0329] In Section XII, the information processing method of the wheel load estimation device 102 of the third embodiment will be described. This information processing method is specifically executed as a method for estimating the wheel loads of the front and rear wheels of a four-wheel or three-wheel forklift. Hereinafter, only the differences from the first embodiment and the second embodiment will be described.

[0330] Figure 17 is an activity diagram showing the process of information processing executed by the wheel load estimation device 102 when using the wheel speed sensor 202, the gyro sensor 204, and the posture angle sensor 206. Hereinafter, each activity of this activity diagram will be described.

[0331] The control unit 110 obtains from the vehicle specification DB28 information including the mass M β , the sum of the static loads F z0 , R z0 , the shapes of the respective components, the mass m j of the front, rear, left, and right wheels, etc., including the structure and the arrangement of each wheel (activity A210).

[0332] The control unit 110 acquires the wheel speed U, the pitch angular velocity Q, and the vehicle pitch angle θ (operation A240).

[0333] In operation A140, for example, the following two-stage information processing is performed. (1) The control unit 110 acquires the wheel speed U from the detection value of the wheel speed sensor 202, the pitch angular velocity Q from the detection value of the gyro sensor 204, and the vehicle pitch angle θ from the detection value of the attitude angle sensor 206. (2) The information of the acquired U, Q, and θ is stored in the storage unit 120.

[0334] Next, the control unit 110 calculates the differential value (wheel acceleration) of the wheel speed U Pitch angular acceleration (operation A250).

[0335] In operation A150, for example, the following two-stage information processing is performed. (1) The control unit 110 reads out the wheel speed U and the pitch angular velocity Q stored in the storage unit 120, and calculates the wheel acceleration Pitch angular acceleration (2) The calculated is stored in the storage unit 120.

[0336] Next, the control unit 110 calculates the longitudinal acceleration S xCG . Reads out the wheel acceleration stored in the storage unit 120 Vehicle pitch angle θ, calculates the longitudinal acceleration S xCG (operation A260).

[0337] In operation A260, for example, the following two-stage information processing is performed. (1) The control unit 110 reads out the wheel acceleration stored in the storage unit 120 Vehicle pitch angle θ, based on θ and the gravitational acceleration g, calculates the longitudinal acceleration S xCG . (2) The calculated S xCG is stored in the storage unit 120.

[0338] Next, the control unit 110 estimates the change amounts ΔF z and ΔR z (operation A270).

[0339] In operation A270, for example, the following three-stage information processing is performed. (1) The control unit 110 reads out the S xCG , M all , J all , hCG , l f , l r . (2) Based on each piece of information read out in (1), the change amounts ΔF z and ΔR z are estimated. (3) The control unit 110 stores the change amounts ΔF z and ΔR z of the wheel loads in the storage unit 120.

[0340] In other words, the estimation unit estimates the wheel loads applied to the front and rear wheels of the vehicle 600 based on the inertia value related to the inertia at the center of gravity position of the vehicle 600, at least one of the angular velocity and angular acceleration of the vehicle 600 about one axis, the torque acting on the vehicle 600, and a prescribed estimation formula.

[0341] Next, the control unit 110 calculates the sum of the front and rear left and right wheel loads and outputs it as the wheel load estimation result (operation A280).

[0342] 3. Experimental Example

[0343] In Section XIII, the experimental example of the second embodiment will be described.

[0344] Figure 18 is a diagram showing a situation where a three-wheel forklift equipped with the IMU 200 travels on an inclined road. Figure 19 is a diagram showing Figure 18 the result of estimating the wheel loads of the three-wheel forklift. More specifically, in Figure 18 and Figure 19 , the actual vehicle measurement values of the longitudinal acceleration S x , lateral acceleration S y , roll angular velocity P, pitch angular velocity Q, and yaw angular velocity R using the IMU 200 are used to estimate the wheel loads of the three-wheel forklift based on Equation (27). However, in Equation (27), it is assumed that h r = 0. In addition, the roll angular acceleration pitch angular acceleration yaw angular acceleration obtained by approximately differentiating the angular velocities P, Q, and R about each axis as the actual vehicle measurement values all have large vibration components, so they are always set to 0

[0345] As Figure 19 shows, even in a situation where vehicle roll and pitch angles occur, the estimated values of the wheel loads are roughly consistent with the actual vehicle measurement values, and the wheel loads can be estimated with good accuracy.

[0346] <Fourth Embodiment>

[0347] Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, a forklift equipped with a fork 603 is taken as a specific example of the vehicle 600, and a case where the movement of the vehicle 600 is restricted using the wheel loads estimated by the wheel load estimation device 100 will be described.

[0348] 14. Functional Configuration

[0349] In the fourteenth section, the functional configuration of the fourth embodiment will be described.

[0350] Figure 20 It is a block diagram showing the functions implemented by the vehicle 600. The vehicle 600 includes a detection unit 710, an operation unit 720, a load calculation unit 730, a center of gravity calculation unit 740, a tire ground load calculation unit 750, a vehicle speed calculation unit 760, a posture angle calculation unit 770, a determination unit 780, a display unit 790, a drive instruction generation unit 810, a drive device 820, an oil control valve 830, a cargo handling device 840, and a wheel load estimation device 100.

[0351] The detection unit 710 includes: a wheel speed sensor 202 for detecting the vehicle speed; a pressure sensor 300 for detecting the weight of the load 602; a load sensor for measuring the tilting thrust that causes the mast to tilt and move; and an IMU 200.

[0352] The operation unit 720 transmits the operations intended by the operator, such as the operation of the cargo handling lever (raising and lowering, tilting movement of the mast, etc.) and the operation of the accelerator pedal and brake pedal during the forward and backward movement / braking of the vehicle 600, to the vehicle.

[0353] The load calculation unit 730 calculates the weight of the load 602 based on the pressure sensor 300.

[0354] The center of gravity calculation unit 740 calculates the center of gravity of the entire vehicle 600 and the center of gravity of the load 602 based on the tilt angle sensor, the load sensor for measuring the tilting thrust, the encoder 400, the weight of the load 602 calculated by the load calculation unit 730, and the vehicle specification DB28.

[0355] The tire ground load calculation unit 750 calculates the tire ground load (static load) at rest based on the load calculation unit 730, the center of gravity calculation unit 740, and the vehicle specification DB28.

[0356] The vehicle speed calculation unit 760 calculates and corrects the speed of the vehicle 600 based on the tire ground load calculation unit 750, the wheel speed sensor 202 included in the detection unit 710, and tire specifications such as the dynamic load radius.

[0357] The posture angle calculation unit 770 calculates the tilt angles of the vehicle 600 in the front-rear direction and the left-right direction based on the calculation results of the IMU 200 and the vehicle speed calculation unit 760.

[0358] Based on the center of gravity calculation result, the load calculation result, the posture angle calculation result, the vehicle speed calculation result, the measurement result of the detection unit 710, and the operation result of the operation unit 720, the determination unit 780 calculates the limit values of the vehicle speed and the acceleration / deceleration of the vehicle 600, the lifting height at which the cargo can be loaded and unloaded, and the angle at which the mast can be tilted and moved. The determination unit 780 determines whether intervention in the cargo loading and unloading operation and intervention in the driving control are required. The determination unit 780 issues control instructions to the drive device 820 and the cargo handling device 840. The determination unit 780 notifies the display unit 790 of the respective limit values and the limit states.

[0359] The display unit 790 displays the detection result of the detection unit 710, the limit values calculated by the determination unit 780, the limit states, and the like.

[0360] Based on the output result of the determination unit 780, the drive instruction generation unit 810 generates an instruction signal for the drive device 820. The drive instruction generation unit 810 transmits the instruction signal to the drive device 820.

[0361] The drive device 820 is driven based on the instruction signal transmitted by the drive instruction generation unit 810. The drive device 820 causes the vehicle 600 to travel by driving. The drive device 820 includes a motor, an engine, or the like.

[0362] The oil control valve 830 controls the hydraulic pressure based on the output result of the determination unit 780.

[0363] The cargo handling device 840 is connected to the oil control valve 830 via a hydraulic circuit and operates according to the controlled hydraulic pressure.

[0364] The wheel load estimation device 100 estimates the wheel loads applied to the respective wheels of the vehicle 600 using the logics illustrated in the first to third embodiments.

[0365] 15. Information Processing Method

[0366] In Section 15, an information processing method executed by the vehicle 600 is described.

[0367] Figures 21 - 26 is an activity diagram showing the flow of information processing executed by the vehicle 600. Hereinafter, each activity of this activity diagram will be described. Here, sometimes the main body executing each activity is shown as a functional unit, and the functional units are collectively shown as the control unit 110.

[0368] First, the vehicle 600 holds the load 602 (Activity A310). In Activity A310, the detection unit 710 measures the geometries of the fork 603, the outer mast 604, and the inner mast 605 (Activity A310).

[0369] Next, the load calculation unit 730 calculates the weight of the load 602 based on the pressure sensor 300 (Activity A320).

[0370] Next, the center of gravity calculation unit 740 calculates the center of gravity of the load 602 and the center of gravity of the entire vehicle 600 based on the tilt angle sensor, the load sensor for measuring tilt thrust, the encoder 400, the weight of the load 602 calculated by the load calculation unit 730, and the vehicle specification DB28 (Activity A330).

[0371] Next, the tire ground contact load calculation unit 750 calculates the load on each wheel when the vehicle 600 is stationary (initial wheel load) based on the load calculation unit 730, the center of gravity calculation unit 740, and the vehicle specification DB28 (Activity A340).

[0372] Next, the determination unit 780 calculates the following parameters (hereinafter also referred to as "first limit values") based on the calculated weight of the load 602 (operation A350). (1) Vehicle speed limit value when the vehicle 600 is moving forward, (2) Vehicle speed limit value when the vehicle 600 is moving backward, (3) Acceleration limit value when the vehicle 600 is moving forward, (4) Acceleration limit value when the vehicle 600 is moving backward, (5) Deceleration limit value when the vehicle 600 is moving forward, (6) Deceleration limit value when the vehicle 600 is moving backward, (7) Limit value of the change in the posture angle in the pitching direction when the vehicle 600 is traveling, (8) Allowable value of the reduction in the tire ground contact load when the vehicle 600 is traveling, (17) Lift height threshold for applying a lift speed limit during a lift ascending operation, (18) Lift height threshold for applying a lift stop limit during a lift ascending operation, (19) Ascending speed of the load 602 when a lift stop limit is applied during a lift ascending operation, (20) Lift height threshold when the limit is released after the intervention of cargo handling during the lift ascending, (21) Tilt angle for applying a tilt forward speed limit during a tilt forward operation, (22) Tilt angle for applying a tilt forward stop limit during a tilt forward operation, (23) Limit speed when a tilt speed limit is applied during a tilt forward operation, (24) Release threshold angle for releasing the limit when tilting backward after the speed limit and forward tilt stop during a tilt forward operation, (25) Tilt angle for applying a tilt backward speed limit during a tilt backward operation, (26) Tilt angle for applying a tilt backward stop limit during a tilt backward operation, (27) Limit speed when a tilt speed limit is applied during a tilt backward operation, (28) Release threshold angle for releasing the limit when tilting forward after the speed limit and backward tilt stop during a tilt backward operation, (29) Angle threshold (angle change amount) of the posture angle used during the intervention of cargo handling in the monitoring of the change in wheel load and angle during cargo handling operation, (30) Wheel load threshold (wheel load change amount) used during the intervention of cargo handling in the monitoring of the change in wheel load and angle during cargo handling operation, (31) Angle threshold of the posture angle used for releasing the intervention after the intervention of cargo handling in the monitoring of the change in wheel load and angle during cargo handling operation, (32) Wheel load threshold used for releasing the intervention after the intervention of cargo handling in the monitoring of the change in wheel load and angle during cargo handling operation.

[0373] Next, the wheel load estimation device 100 estimates the wheel loads applied to the respective wheels of the vehicle 600 (operation A360).

[0374] Next, the determination unit 780 determines the motion mode of the vehicle 600 (stopped, in motion, or during cargo handling) (activity A370). When it is determined that the vehicle 600 is stopped, the control unit 110 transfers to the process of activity A320. When it is determined that the vehicle 600 is in motion, the control unit 110 transfers to the process of activity A380. When it is determined that the vehicle 600 is during cargo handling, the control unit 110 transfers to the processes of activities A430 and A490.

[0375] Next, the case where the vehicle 600 is in motion will be described. The determination unit 780 performs speed limit processing of the vehicle 600 and acceleration / deceleration limit processing of the vehicle 600 based on the calculated first limit values (activity A380). That is, the determination unit 780 performs the driving process of the vehicle 600 with each limit value calculated as the first limit values (1) to (6) as the upper limit.

[0376] Next, the determination unit 780 determines whether the first limit value (7) is exceeded or whether the first limit value (8) is exceeded (activity A390). When the first limit value (7) is exceeded or the first limit value (8) is exceeded, the control unit 110 transfers to the process of activity A400 ( "Yes" in activity A390). When it is less than or equal to the first limit value (7) and less than or equal to the first limit value (8), the control unit 110 continues the process of activity A390 ( "No" in activity A390).

[0377] Next, the determination unit 780 calculates the following parameters (hereinafter also referred to as "second limit values") based on the calculated weight of the load 602 (activity A400). (9) Vehicle speed limit value when the vehicle 600 moves forward, (10) Vehicle speed limit value when the vehicle 600 moves backward, (11) Acceleration limit value when the vehicle 600 moves forward, (12) Acceleration limit value when the vehicle 600 moves backward, (13) Deceleration limit value when the vehicle 600 moves forward, (14) Deceleration limit value when the vehicle 600 moves backward, (15) Angle threshold of the posture angle used during intervention release in the monitoring of the change in wheel load and angle when the vehicle 600 is in motion, (16) Wheel load threshold used during intervention release in the monitoring of the change in wheel load and angle when the vehicle 600 is in motion.

[0378] Next, the determination unit 780 performs speed limit processing of the vehicle 600 and acceleration / deceleration limit processing of the vehicle 600 based on the calculated second limit values (activity A410). That is, the determination unit 780 performs the driving process of the vehicle 600 with each limit value calculated as the second limit values (9) to (16) as the upper limit.

[0379] Next, the determination unit 780 determines whether it is less than the second limit value (15) and exceeds the second limit value (16) (activity A420). In the case where it is less than the second limit value (15) and exceeds the second limit value (16), the control unit 110 transfers to the process of activity A380 (the "Yes" of activity A320). In the case where it is equal to or greater than the second limit value (15) or equal to or less than the second limit value (16), the control unit 110 continues the process of activity A420 (the "No" of activity A420).

[0380] Next, a case where the vehicle 600 is in the process of loading and unloading goods will be described. The determination unit 780 determines whether it exceeds the first limit value (29) or is less than the first limit value (30) (activity A430). In the case where it exceeds the first limit value (29) or is less than the first limit value (30), the control unit 110 transfers to the process of activity A440 (the "Yes" of activity A430). In the case where it is less than or equal to the first limit value (29) and greater than or equal to the first limit value (30), the control unit 110 continues the process of activity A430 (the "No" of activity A430).

[0381] Next, the determination unit 780 performs a stop process of the loading and unloading operation (loading and unloading intervention process) (activity A440).

[0382] Next, the determination unit 780 determines whether the lever for the loading and unloading operation has been returned to neutral (activity A450). In the case where the lever has been returned, the control unit 110 transfers to the process of activity A460 (the "Yes" of activity A450). In the case where the lever has not been returned, the control unit 110 continues the process of activity A450 (the "No" of activity A450).

[0383] Next, the determination unit 780 partially releases the restriction of the loading and unloading operation (activity A460). Here, it is assumed that the reverse operation of the operation immediately before the stop process can be performed. For example, it is assumed that when the lift has stopped while rising, only the lift lowering operation can be performed.

[0384] Next, the determination unit 780 determines whether it is less than the first limit value (31) and exceeds the first limit value (32) (activity A470). In the case where it is less than the first limit value (31) and exceeds the first limit value (32), the determination unit 780 transfers to the process of activity A480 (the "Yes" of activity A470). In the case where it is equal to or greater than the first limit value (31) or equal to or less than the first limit value (32), the determination unit 780 continues the process of activity A470 (the "No" of activity A470).

[0385] Next, the determination unit 780 releases all restrictions on the cargo handling operation (activity A480). The processes from activity A430 to A480 are repeatedly executed during the period when it is determined in activity A370 that "cargo is being handled".

[0386] Next, the determination unit 780 determines the cargo handling mode (lifting or tilting) of the vehicle 600 (activity A490). When it is determined that the vehicle 600 is in the lifting state, the control unit 110 transfers to the process of activity A500. When it is determined that the vehicle 600 is in the tilting state, the control unit 110 transfers to the process of activity A590.

[0387] Next, the determination unit 780 determines the lifting mode (ascending, descending, or stopped) of the vehicle 600 (activity A500). When it is determined that the fork 603 of the vehicle 600 is ascending, the control unit 110 transfers to the process of activity A510. When it is determined that the fork 603 of the vehicle 60 is descending, the control unit 110 continues the process of activity A500. When it is determined that the fork 603 of the vehicle 600 has stopped, the control unit 110 transfers to the process of activity A310.

[0388] Next, the case where the fork 603 of the vehicle 600 is ascending will be described. The determination unit 780 determines whether the first limit value (17) is exceeded (activity A510). When the first limit value (17) is exceeded, the control unit 110 transfers to the process of activity A520 ( "Yes" in activity A510). When it is less than or equal to the first limit value (17), the control unit 110 continues the process of activity A510 ( "No" in activity A510).

[0389] Next, the determination unit 780 restricts the ascending speed of the fork 603 based on the first limit value (19) (activity A520).

[0390] Next, the determination unit 780 determines whether the first limit value (18) is exceeded (activity A530). When the first limit value (18) is exceeded, the determination unit 780 transfers to the process of activity A540 ( "Yes" in activity A530). When it is less than or equal to the first limit value (18), the determination unit 780 continues the process of activity A530 ( "No" in activity A530).

[0391] Next, the determination unit 780 performs the stop process of the cargo handling operation (elevator stop intervention) and the travel prohibition process of the vehicle 600 (activity A540).

[0392] Next, the determination unit 780 determines whether the lever for the loading and unloading operation has been returned (activity A550). When the lever for the loading and unloading operation has been returned, the control unit 110 transfers to the process of activity A560 ("Yes" in activity A550). When the lever for the loading and unloading operation has not been returned, the control unit 110 continues the process of activity A550 ("No" in activity A550).

[0393] Next, the determination unit 780 partially releases the restrictions on the loading and unloading operation (activity A560). Here, only the lowering operation of the fork 603 is released.

[0394] Next, the determination unit 780 determines whether it is less than the first limit value (20) (activity A570). When it is less than the first limit value (20), the control unit 110 transfers to the process of activity A580 ("Yes" in activity A570). When it is equal to or greater than the first limit value (20), the control unit 110 continues the process of activity A570 ("No" in activity A570).

[0395] Next, the determination unit 780 releases all the restrictions on the loading and unloading operation (activity A580). After that, the control unit 110 transfers to the process of activity A490.

[0396] Next, the case where it is determined as "tilting" in activity A490 will be described. The determination unit 780 determines the tilting direction (forward tilting, backward tilting, or stopped) of the fork 603 (activity A590). When it is determined that the fork 603 of the vehicle 600 is in the forward tilting state, the control unit 110 transfers to the process of activity A600. When it is determined that the fork 603 of the vehicle 600 is in the backward tilting state, the control unit 110 transfers to the process of activity A680. When it is determined that the fork 603 of the vehicle 600 has stopped, the control unit 110 transfers to the process of activity A310.

[0397] Next, the case where the fork 603 of the vehicle 600 is in the forward tilting state will be described. The determination unit 780 determines whether it has exceeded the first limit value (21) (activity A600). When it has exceeded the first limit value (21), the control unit 110 transfers to the process of activity A610 ("Yes" in activity A600). When it is equal to or less than the first limit value (21), the control unit 110 continues the process of activity A600 ("No" in activity A600).

[0398] Next, the determination unit 780 restricts the tilting speed of the fork 603 based on the first limit value (23) (activity A610).

[0399] Next, the determination unit 780 determines whether the first limit value (22) has been exceeded (operation A620). If the first limit value (22) has been exceeded, the determination unit 780 proceeds to the process of operation A630 (Yes in operation A620). If it is equal to or less than the first limit value (22), the determination unit 780 continues the process of operation A620 (No in operation A620).

[0400] Next, the determination unit 780 performs a stop process for the cargo handling operation (tilt stop intervention) and a travel prohibition process for the vehicle 600 (operation A630).

[0401] Next, the determination unit 780 determines whether the lever for the cargo handling operation has been returned (operation A640). If the lever for the cargo handling operation has been returned, the control unit 110 proceeds to the process of operation A650 (Yes in operation A640). If the lever for the cargo handling operation has not been returned, the control unit 110 continues the process of operation A640 (No in operation A640).

[0402] Next, the determination unit 780 partially releases the restriction on the cargo handling operation (operation A650). Here, only the backward tilt operation of the fork 603 is released.

[0403] Next, the determination unit 780 determines whether it is less than the first limit value (24) (operation A660). If it is less than the first limit value (24), the control unit 110 proceeds to the process of operation A670 (Yes in operation A660). If it is equal to or greater than the first limit value (24), the control unit 110 continues the process of operation A660 (No in operation A660).

[0404] Next, the determination unit 780 completely releases the restriction on the cargo handling operation (operation A670). After that, the control unit 110 proceeds to the process of operation A370.

[0405] Next, the case where the fork 603 of the vehicle 600 is in the backward tilt state will be described. The determination unit 780 determines whether the first limit value (25) has been exceeded (operation A680). If the first limit value (25) has been exceeded, the control unit 110 proceeds to the process of operation A690 (Yes in operation A680). If it is equal to or less than the first limit value (25), the control unit 110 continues the process of operation A680 (No in operation A680).

[0406] Next, the determination unit 780 restricts the tilt speed of the fork 603 based on the first limit value (27) (operation A690).

[0407] Next, the determination unit 780 determines whether the first limit value (26) has been exceeded (Activity A700). If the first limit value (26) has been exceeded, the control unit 110 transfers to the process of Activity A710 ("Yes" in Activity A700). If it is equal to or less than the first limit value (26), the control unit 110 continues the process of Activity A700 ("No" in Activity A700).

[0408] Next, the determination unit 780 performs a stop process for the cargo handling operation (tilt stop intervention) and a travel prohibition process for the vehicle 600 (Activity A710).

[0409] Next, the determination unit 780 determines whether the lever for the cargo handling operation has been returned (Activity A720). If the lever for the cargo handling operation has been returned, the control unit 110 transfers to the process of Activity A730 ("Yes" in Activity A720). If the lever for the cargo handling operation has not been returned, the control unit 110 continues the process of Activity A720 ("No" in Activity A720).

[0410] Next, the determination unit 780 partially releases the restriction on the cargo handling operation (Activity A730). Here, only the forward tilt operation of the fork 603 is released.

[0411] Next, the determination unit 780 determines whether it is less than the first limit value (28) (Activity A740). If it is less than the first limit value (28), the control unit 110 transfers to the process of Activity A750 ("Yes" in Activity A740). If it is equal to or greater than the first limit value (28), the control unit 110 continues the process of Activity A740 ("No" in Activity A740).

[0412] Next, the determination unit 780 completely releases the restriction on the cargo handling operation (Activity A750). After that, the control unit 110 transfers to the process of Activity A370.

[0413] As described above, by using the wheel load estimation device 100 in the forklift, it is possible to balance the stability and workability of the forklift.

[0414] In other words, if the fourth embodiment is described differently, the vehicle 600 includes a wheel load estimation device 100, a determination unit 780 having the function of a restriction unit, and an operation unit 720 (operation amount detection unit). The wheel load estimation device 100 outputs the estimated wheel load. The operation unit 720 detects the operation amount of the fork 603. The determination unit 780 determines whether it is necessary to restrict the movement of the vehicle 600 based on the estimated wheel load, the detected operation amount, and the reference information. The reference information is information indicating the relationship among the estimated wheel load, the detected operation amount, and whether it is necessary to restrict the movement of the vehicle 600. The determination unit 780 (restriction unit) restricts the movement of the vehicle 600 when it is determined that it is necessary to restrict the movement of the vehicle 600.

[0415] As described above, the embodiments of the present invention have been described, but the present invention is not limited thereto, and appropriate changes can be made without departing from the technical idea of the present invention.

[0416] 16. Modification

[0417] In the sixteenth section, the modification of the present embodiment will be described.

[0418] The solution of the present embodiment may also be a program. This program causes a computer to function as each part of the wheel load estimation device 100.

[0419] The solution of the present embodiment may also be a wheel load estimation method. This wheel load estimation method includes processes executed by each part of the wheel load estimation device 100 as each step.

[0420] The control unit 110 performs a write process (storage process) and a read process on the storage unit 120 with respect to various data and various information, but is not limited thereto. For example, registers or cache memories in the control unit 110 may be used to execute information processing of each activity.

[0421] The acceleration used in the present embodiment may also be the acceleration in the three-axis directions of the vehicle 600.

[0422] In activities A140 and A150, both the angular velocity and angular acceleration of the vehicle 600 around the three axes are obtained, but it is not limited thereto. The acquisition unit only needs to obtain at least one of the angular velocity and angular acceleration of the vehicle 600 around the three axes.

[0423] In activity A190, the wheel load is estimated based on at least one of the inertia value related to the inertia at the center of gravity position, the angular velocity and angular acceleration, the inertial force generated in the vehicle 600, and a prescribed estimation formula, but it is not limited thereto. The estimation unit only needs to estimate the wheel load applied to each wheel included in the vehicle 600 based on at least the torque acting on the vehicle 600 and a prescribed estimation formula.

[0424] In this embodiment, the case where the lifting height is obtained from the rotation angle of the unloading hydraulic motor detected by the encoder 400 has been described, but it is not limited thereto. For example, the lifting height may also be obtained by providing a wire on the fork 603 and measuring the change in the length of the wire during unloading. In addition, the other values obtained by each obtaining unit are not limited to the cases obtained by the methods of the above-described embodiments, and may also be obtained by other methods.

[0425] In this embodiment, the case where the wheel load estimation device 100 is mounted on the vehicle 600 has been described, but it is not limited thereto, and it may also be configured as an external device. In this case, a communication unit that transmits the detection values of the IMU 200, the pressure sensor 300, the encoder 400, and the operation amount sensor 500 to the wheel load estimation device 100 may be provided in the vehicle 600, and the wheel load estimation device 100 configured as an external device obtains various information transmitted from the communication unit of the vehicle 600 and estimates the wheel load by the same processing as the above-described embodiments.

[0426] In the fourth embodiment, the determination unit 780 has been described as a configuration having the functions of both the "determination unit" and the "limitation unit" recited in the claims, but it is not limited thereto, and the vehicle 600 may further include a functional unit equivalent to the "limitation unit" independently of the determination unit 780.

[0427] 17. Others

[0428] It may also be provided by the following various aspects.

[0429] (1) A wheel load estimation device that estimates the wheel load applied to each wheel of a vehicle, comprising an acquisition unit, a calculation unit, and an estimation unit, where the acquisition unit acquires a detection value output from a sensor as a parameter, the parameter being a parameter related to the movement of the vehicle, the calculation unit calculates an inertial force generated in the vehicle based on the parameter and the mass of the vehicle, and the estimation unit estimates the wheel load based on the inertial force and a prescribed estimation formula.

[0430] According to such an aspect, when estimating the wheel load, the calculation load can be reduced compared to the prior art. Therefore, the saved resources can be used for other core functions.

[0431] (2) In the wheel load estimation device according to (1) above, the parameter includes at least one of the acceleration of the vehicle and the angular velocity and angular acceleration of the vehicle around three axes.

[0432] According to such an aspect, the detection values output from the IMU can be effectively utilized, and the wheel load estimation logic for a flat road can be used for an inclined road.

[0433] (3) In the wheel load estimation device described in (2) above, the acceleration is the acceleration in the three-axis directions of the vehicle.

[0434] According to such a solution, by using the acceleration in the three-axis directions of the vehicle, it is possible to accurately estimate the wheel load during traveling on an inclined road with good precision.

[0435] (4) In the wheel load estimation device described in (1) above, the parameter includes at least one of the wheel speed and the first wheel acceleration of the vehicle, at least one of the angular velocity and the angular acceleration of the vehicle about the pitch axis, and the attitude angle of the vehicle about the pitch axis.

[0436] According to such a solution, it is possible to effectively utilize the detection value output from the wheel speed sensor and use the wheel load estimation logic for a flat road as that for an inclined road.

[0437] (5) In the wheel load estimation device described in (4) above, the parameter includes the first wheel acceleration, and the calculation unit calculates a second wheel acceleration obtained by correcting the first wheel acceleration based on the first wheel acceleration and the attitude angle, and the calculation unit calculates the inertial force based on the second wheel acceleration and the mass.

[0438] According to such a solution, by performing the correction process unique to traveling on an inclined road, it is possible to accurately estimate the wheel load during traveling on an inclined road with good precision.

[0439] (6) In the wheel load estimation device described in (5) above, the second wheel acceleration is obtained by correcting the first wheel acceleration by applying a direction component to the first wheel acceleration, and the direction component is a direction component related to the inclination direction of the vehicle calculated from the parameter and the component of the gravitational acceleration.

[0440] According to such a solution, by performing the correction process unique to traveling on an inclined road, it is possible to accurately estimate the wheel load during traveling on an inclined road with good precision.

[0441] (7) In the wheel load estimation device according to any one of (1) to (6) above, the calculation unit calculates the center of gravity position of the vehicle, the calculation unit calculates an inertia value related to the inertia at the center of gravity position based on the center of gravity position and the mass, and the estimation unit estimates the wheel load based on the inertia value, the inertial force, and the estimation formula.

[0442] According to such a solution, by using the inertia tensor of the vehicle, it is possible to more accurately estimate the wheel load during traveling on an inclined road.

[0443] (8) In the wheel load estimation device according to any one of (1) to (7) above, the acquisition unit continuously acquires the parameters, the calculation unit continuously calculates the inertial force based on the continuously acquired parameters and the mass of the vehicle, and the estimation unit continuously estimates the wheel load in time series based on the continuously calculated inertial force and the estimation formula.

[0444] According to such a solution, the wheel load can be continuously estimated in time series.

[0445] (9) A vehicle includes the wheel load estimation device according to any one of (1) to (8) above, a determination unit, and a restriction unit. The wheel load estimation device outputs the estimated wheel load. The determination unit determines whether it is necessary to restrict the movement of the vehicle based on the estimated wheel load and reference information, where the reference information is information indicating the relationship between the estimated wheel load and whether it is necessary to restrict the movement of the vehicle. The restriction unit restricts the movement of the vehicle when it is determined that it is necessary to restrict the movement of the vehicle.

[0446] According to such a solution, the wheel load estimation device can be used to balance the stability and workability of the vehicle.

[0447] (10) In the vehicle according to (9) above, a fork is further provided, and the vehicle is a forklift.

[0448] According to such a solution, the wheel load estimation device can be appropriately installed on a forklift.

[0449] (11) In the vehicle according to (10) above, an operation amount detection unit is further provided. The operation amount detection unit detects the operation amount of the fork. The determination unit determines whether it is necessary to restrict the movement of the vehicle based on the estimated wheel load, the operation amount, and the reference information, where the reference information is information indicating the relationship between the estimated wheel load, the operation amount, and whether it is necessary to restrict the movement of the vehicle. The restriction unit restricts the movement of the vehicle when it is determined that it is necessary to restrict the movement of the vehicle.

[0450] According to such a solution, the wheel load estimation device can be used to balance the stability and workability of the vehicle.

[0451] (12) A program causes a computer to function as each part of the wheel load calculation device according to any one of (1) to (8) above.

[0452] According to such a solution, the calculation load can be reduced compared with the past when estimating the wheel load. Therefore, the saved resources can be used for other core functions.

[0453] (13)A wheel load estimation method includes processes executed by respective parts of the wheel load estimation device according to any one of the above (1) to (8) as respective steps.

[0454] According to such a solution, the computational load can be reduced compared with the prior art when estimating the wheel load. Therefore, the saved resources can be used for other core functions.

[0455] Of course, it is not limited thereto.

Claims

1. A wheel load estimating device for estimating a wheel load applied to each wheel of a vehicle, characterized in that: comprising an acquisition unit, a calculation unit and an estimation unit, The acquisition unit acquires a detection value output from a sensor as a parameter, The parameter is a parameter related to the movement of the vehicle, The calculation unit calculates the inertial force generated in the vehicle based on the parameter and the mass of the vehicle. The estimating unit estimates the wheel load based on the inertial force and a predetermined estimation formula.

2. The wheel load estimation device according to claim 1, wherein: The parameter includes the acceleration of the vehicle and at least one of the angular velocity and angular acceleration of the vehicle around three axes.

3. The wheel load estimation device according to claim 2, wherein: The acceleration is the acceleration of the vehicle in three axes.

4. The wheel load estimating device according to claim 1, wherein: The parameters include at least one of a wheel speed and a first wheel acceleration of the vehicle, at least one of an angular velocity and an angular acceleration of the vehicle around a pitch axis, and a posture angle of the vehicle around the pitch axis.

5. The wheel load estimating device according to claim 4, wherein: The parameters include the first wheel acceleration, The calculation unit calculates a second wheel acceleration obtained by correcting the first wheel acceleration based on the first wheel acceleration and the posture angle. The calculation unit calculates the inertial force based on the second wheel acceleration and the mass.

6. The wheel load estimating device according to claim 5, wherein: The second wheel acceleration is obtained by correcting the first wheel acceleration by applying a direction component to the first wheel acceleration, the direction component being a direction component related to a component based on a tilt direction of the vehicle and a gravity acceleration calculated from the parameter.

7. The wheel load estimating device according to claim 1, wherein: The calculation unit calculates the center of gravity position of the vehicle. The calculation unit calculates an inertia value related to the inertia at the center of gravity position based on the center of gravity position and the mass, The estimating unit estimates the wheel load based on the inertia value, the inertia force, and the estimation formula.

8. The wheel load estimating device according to claim 1, wherein: The acquisition unit continuously acquires the parameters. The calculation unit continuously calculates the inertial force based on the continuously acquired parameter and the mass of the vehicle. The estimating unit estimates the wheel load continuously in time series based on the continuously calculated inertial force and the estimation formula.

9. A vehicle, characterized in that: A wheel load estimating device according to any one of claims 1 to 8, a determination unit and a restriction unit, The wheel load estimating device outputs the estimated wheel load, The determination unit determines whether it is necessary to restrict the movement of the vehicle based on the estimated wheel load and reference information. The reference information is information indicating a relationship between the estimated wheel load and whether or not the movement of the vehicle needs to be restricted. The restriction unit restricts the movement of the vehicle when determining that the movement of the vehicle needs to be restricted.

10. The vehicle according to claim 9, wherein: It also has a fork. The vehicle is a forklift.

11. The vehicle according to claim 10, wherein: It also has an operation amount detection unit. The operation amount detection unit detects the operation amount of the fork, The determination unit determines whether the movement of the vehicle needs to be restricted based on the estimated wheel load, the operation amount, and the reference information. The reference information is information indicating a relationship between the estimated wheel load, the operation amount, and whether or not the movement of the vehicle needs to be restricted. The restriction unit restricts the movement of the vehicle when determining that the movement of the vehicle needs to be restricted.

12. A program, characterized in that A computer is made to function as each unit of the wheel load estimating device according to any one of claims 1 to 8.

13. A wheel load estimation method, characterized in that: A process executed by each unit of the wheel load estimating device according to any one of claims 1 to 8 is provided as each step.

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