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

1 . A vehicle comprising:

a wheel load estimation device that estimates a longitudinal force (Xv) as a wheel load acting on a wheel of the vehicle when traveling straight downhill on a slope,

the wheel load estimation device including at least one sensor configured to output detection values including an acceleration (Sx) in a forward/rearward traveling direction of the vehicle, angular velocities (P, Q, R), and angular accelerations ({dot over (P)}, {dot over (Q)}, {dot over (R)}) about axes along the forward/rearward traveling direction, a lateral direction, and a vertical direction of the vehicle; and

at least one processor configured to:

acquire the detection values output from the at least one sensor as parameters related to a motion of the vehicle,

acquire a longitudinal acceleration (S xCG ) at a center of gravity (CG all ) of the vehicle using the detection values,

estimate the wheel load based on a product of a mass (M all ) of the vehicle and the longitudinal acceleration (S xCG ) at the center of gravity (CG all ) of the vehicle,

determine whether limiting a motion of the vehicle is necessary based on the estimated wheel load and reference information, the reference information being information indicating a relationship between the estimated wheel load and whether limiting the motion of the vehicle is necessary; and

based upon the determination that limiting the motion of the vehicle is necessary, limit at least one of: a traveling speed of the vehicle, an acceleration of the vehicle, a deceleration of the vehicle, a lifting speed of a fork of the vehicle, a tilting speed of the fork, a load handling operation of the vehicle, or traveling of the vehicle.

2 . The vehicle according to claim 1 , wherein

the parameters further include a lateral acceleration of the vehicle and a vertical acceleration of the vehicle.

3 . The vehicle according to claim 2 , wherein

the acceleration in the forward/rearward traveling direction, the lateral acceleration, and the vertical acceleration constitute accelerations is an acceleration in three axial directions of the vehicle,

the at least one processor is further configured to:

calculate a position of a center of gravity of the vehicle,

calculate an inertia value relating to an inertia at the position of the center of gravity of the vehicle based on the position of the center of gravity of the vehicle and the mass of the vehicle, and

estimate the wheel load based on the inertia value, an inertial force, and a predetermined estimation equation.

4 . The vehicle according to claim 1 , wherein

the parameters further 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 about a pitch axis of the vehicle, and an attitude angle of the vehicle about the pitch axis of the vehicle.

5 . The vehicle according to claim 4 , wherein

the parameters include the first wheel acceleration,

the at least one processor calculates a second wheel acceleration by correcting the first wheel acceleration based on the first wheel acceleration and the attitude angle, and calculates an inertial force based on the second wheel acceleration and the mass.

6 . The vehicle according to claim 5 , wherein

the second wheel acceleration is obtained by correcting the first wheel acceleration with a directional component based on an inclination direction of the vehicle calculated from the parameters and a gravitational acceleration applied to the first wheel acceleration.

7 . The vehicle according to claim 1 , wherein

the at least one processor is further configured to:

calculate a position of a center of gravity of the vehicle,

calculate an inertia value relating to an inertia at the position of the center of gravity of the vehicle based on the position of the center of gravity of the vehicle and the mass of the vehicle, and

estimate the wheel load based on the inertia value, an inertial force, and a predetermined estimation equation.

8 . The vehicle according to claim 1 , wherein

the at least one processor is further configured to:

continuously acquire the parameters,

continuously calculate an inertial force based on the continuously acquired parameters and the mass of the vehicle, and

continuously estimate the wheel load in time series based on the continuously calculated inertial force and a predetermined estimation equation.

9 . The vehicle according to claim 1 , further comprising a fork, wherein

the vehicle is a forklift truck.

10 . The vehicle according to claim 9 , further comprising

at least one sensor configured to detect an operation amount of the fork, wherein

the at least one processor is further configured to

determine whether limiting the motion of the vehicle is necessary, based on the estimated wheel load, the detected operation amount, and the reference information,

the reference information is information indicating a relationship among the estimated wheel load, the operation amount, and whether limiting a motion of the vehicle is necessary.

11 . A non-transitory computer-readable storage medium storing a program for causing a computer to execute processing comprising:

acquiring a detection value output from at least one sensor as a parameter, the parameter being related to a motion of a vehicle, the at least one sensor being configured to output detection values including an acceleration (Sx) in a forward/rearward traveling direction of the vehicle, angular velocities (P, Q, R), and angular accelerations ({dot over (P)}, {dot over (Q)}, {dot over (R)}) about axes along the forward/rearward traveling direction, a lateral direction, and a vertical direction of the vehicle;

acquiring a longitudinal acceleration (S xCG ) at a center of gravity (CG all ) of the vehicle using the detection values;

estimating a longitudinal force as acting on a wheel of the vehicle when traveling straight downhill on a slope, based on a product of a mass (M all ) of the vehicle and the longitudinal acceleration (S xCG ) at the center of gravity (CG all ) of the vehicle;

determining whether limiting a motion of the vehicle is necessary based on the estimated wheel load and reference information, the reference information being information indicating a relationship between the estimated wheel load and whether limiting the motion of the vehicle is necessary; and

based upon the determination that limiting the motion of the vehicle is necessary, limiting at least one of: a traveling speed of the vehicle, an acceleration of the vehicle, a deceleration of the vehicle, a lifting speed of a fork of the vehicle, a tilting speed of the fork, a load handling operation of the vehicle, or traveling of the vehicle.

12 . A wheel load estimation method comprising:

acquiring a detection value output from at least one sensor as a parameter, the parameter being related to a motion of a vehicle, the at least one sensor being configured to output detection values including an acceleration (Sx) in a forward/rearward traveling direction of the vehicle, angular velocities (P, Q, R), and angular accelerations ({dot over (P)}, {dot over (Q)}, {dot over (R)}) about axes along the forward/rearward traveling direction, a lateral direction, and a vertical direction of the vehicle;

acquiring a longitudinal acceleration (S xCG ) at a center of gravity (CG all ) of the vehicle using the detection values;

estimating a longitudinal force as acting on a wheel of the vehicle when traveling straight downhill on a slope, based on a product of a mass (M all ) of the vehicle and the longitudinal acceleration (S xCG ) at the center of gravity (CG all ) of the vehicle;

determining whether limiting a motion of the vehicle is necessary based on the estimated wheel load and reference information, the reference information being information indicating a relationship between the estimated wheel load and whether limiting the motion of the vehicle is necessary; and

based upon the determination that limiting the motion of the vehicle is necessary, limiting at least one of: a traveling speed of the vehicle, an acceleration of the vehicle, a deceleration of the vehicle, a lifting speed of a fork of the vehicle, a tilting speed of the fork, a load handling operation of the vehicle, or traveling of the vehicle.