Estimation device, vehicle, and estimation method

1. An estimation device that estimates a stroke quantity indicating a displacement in an up-and-down direction of a vehicle, in a multistage elastic member in which a plurality of members, each having a different load displacement characteristic indicating a relationship between a load and the displacement, are disposed, the estimation device comprising:

a load calculation unit configured to calculate a variable ground contact load received by a wheel of the vehicle from a ground contact surface, based on a detection signal of a wheel speed sensor for detecting a wheel speed of the vehicle;

a state quantity estimation unit configured to estimate the stroke quantity generated in the multistage elastic member, based on the multistage elastic member and the variable ground contact load, the multistage elastic member having a load displacement characteristic of any one of the plurality of members set as an initial value; and

a characteristic change unit configured to change a setting of the initial value to an estimated load displacement characteristic, in a case where the estimated load displacement characteristic corresponding to the stroke quantity that is estimated by the state quantity estimation unit and the load displacement characteristic that is set as the initial value are different from each other,

wherein the state quantity estimation unit corrects the stroke quantity, based on a result of an estimation operation in which the estimated load displacement characteristic that is changed by the characteristic change unit is set as a changed initial value.

2. The estimation device according to claim 1 , wherein the multistage elastic member includes a spring of a first member and a spring of a second member, and

inclinations are discontinuous at a connection point where a straight line indicating a first load displacement characteristic having a first elastic coefficient of the first member as an inclination is connected with a straight line indicating a second load displacement characteristic having a combined elastic coefficient as an inclination acquired by combining the first elastic coefficient with a second elastic coefficient of the second member.

3. The estimation device according to claim 2 , wherein in a case where the state quantity estimation unit estimates a stroke quantity that falls within a stroke range of the second load displacement characteristic as the estimated load displacement characteristic by an arithmetic operation in which the first load displacement characteristic is set as an initial value,

the characteristic change unit changes the first load displacement characteristic that is set as the initial value to the second load displacement characteristic.

4. The estimation device according to claim 3 , wherein the state quantity estimation unit corrects the stroke quantity that is estimated by the arithmetic operation in which the first load displacement characteristic is set as the initial value, based on a result of an estimation operation in which the second load displacement characteristic is set as a changed initial value.

5. The estimation device according to claim 2 , wherein in a case where the state quantity estimation unit estimates a stroke quantity that falls within a stroke range of the first load displacement characteristic as the estimated load displacement characteristic by an arithmetic operation in which the second load displacement characteristic is set as an initial value,

the characteristic change unit changes the second load displacement characteristic that is set as the initial value to the first load displacement characteristic.

6. The estimation device according to claim 5 , wherein the state quantity estimation unit corrects the stroke quantity that is estimated by the arithmetic operation in which the second load displacement characteristic is set as the initial value, based on a result of an estimation operation in which the first load displacement characteristic is set as a changed initial value.

7. The estimation device according to claim 1 , wherein the multistage elastic member includes a spring of a first member and rubber of a third member, and

inclinations are discontinuous at a connection point where a straight line indicating a first load displacement characteristic having a first elastic coefficient of the first member as an inclination is connected with a third load displacement characteristic having a combined elastic coefficient as an inclination acquired by combining the first elastic coefficient with a third elastic coefficient of the third member.

8. The estimation device according to claim 7 , wherein in a case where the state quantity estimation unit estimates a stroke quantity that falls within a stroke range of the third load displacement characteristic as the estimated load displacement characteristic by an arithmetic operation in which the first load displacement characteristic is set as an initial value,

the characteristic change unit changes the first load displacement characteristic that is set as the initial value to the third load displacement characteristic.

9. The estimation device according to claim 8 , wherein the state quantity estimation unit corrects the stroke quantity that is estimated by the arithmetic operation in which the first load displacement characteristic is set as the initial value, based on a result of an estimation operation in which the third load displacement characteristic is set as a changed initial value.

10. The estimation device according to claim 7 , wherein in a case where the state quantity estimation unit estimates a stroke quantity that falls within a stroke range of the first load displacement characteristic as the estimated load displacement characteristic by an arithmetic operation in which the third load displacement characteristic is set as an initial value,

the characteristic change unit changes the third load displacement characteristic that is set as the initial value to the first load displacement characteristic.

11. The estimation device according to claim 10 , wherein the state quantity estimation unit corrects the stroke quantity that is estimated by the arithmetic operation in which the third load displacement characteristic is set as the initial value, based on a result of an estimation operation in which the first load displacement characteristic is set as a changed initial value.

12. The estimation device according to claim 1 , wherein the multistage elastic member includes a spring of a first member, a spring of a second member, and a rubber of a third member,

inclinations are discontinuous at a connection point where a straight line indicating a first load displacement characteristic having a first elastic coefficient of the first member as an inclination is connected with a straight line indicating a second load displacement characteristic having a combined elastic coefficient as an inclination acquired by combining the first elastic coefficient with a second elastic coefficient of the second member, and

inclinations are discontinuous at a connection point where the straight line indicating the second load displacement characteristic is connected with a third load displacement characteristic having a combined elastic coefficient as an inclination acquired by combining the second elastic coefficient with a third elastic coefficient of the third member.

13. The estimation device according to claim 12 , wherein in a case where the state quantity estimation unit estimates, as the estimated load displacement characteristic, either one of a stroke quantity that falls within a stroke range of the second load displacement characteristic or a stroke quantity that falls within a stroke range of the third load displacement characteristic by an arithmetic operation in which the first load displacement characteristic is set as an initial value,

the characteristic change unit changes the first load displacement characteristic that is set as the initial value to a load displacement characteristic corresponding to the one of the stroke quantities.

14. The estimation device according to claim 13 , wherein the state quantity estimation unit corrects the stroke quantity that is estimated by the arithmetic operation in which the first load displacement characteristic is set as the initial value, based on a result of an estimation operation in which a load displacement characteristic corresponding to the one of the stoke quantities is set as a changed initial value.

15. The estimation device according to claim 12 , wherein in a case where the state quantity estimation unit estimates a stroke quantity that falls within a stroke range of the first load displacement characteristic as the estimated load displacement characteristic by an arithmetic operation in which either one of the second load displacement characteristic or the third load displacement characteristic is set as an initial value,

the characteristic change unit changes the one of the load displacement characteristics that is set as the initial value to the first load displacement characteristic.

16. The estimation device according to claim 15 , wherein the state quantity estimation unit corrects the stroke quantity that is estimated by an arithmetic operation in which the one of the load displacement characteristics that is set as the initial value, based on a result of an estimation operation in which the first load displacement characteristic is set as a changed initial value.

17. The estimation device according to claim 1 , wherein in a case where an estimated load displacement characteristic corresponding to a stroke quantity that is estimated by the state quantity estimation unit and the load displacement characteristic that is set as an initial value match each other, the characteristic change unit maintains a setting of the initial value.

18. The estimation device according to claim 1 , further comprising a control processing unit configured to control damping force of a viscous damping member included in a vibration reduction mechanism,

wherein the control processing unit controls the damping force of the viscous damping member by adjusting a flow path area of a throttle of hydraulic oil filled inside the viscous damping member, based on the stroke quantity that is estimated.

19. A vehicle including an estimation device that estimates a stroke quantity indicating a displacement in an up-and-down direction of the vehicle, in a multistage elastic member in which a plurality of members, each having a different load displacement characteristic indicating a relationship between a load and the displacement, are disposed, the estimation device comprising:

a load calculation unit configured to calculate a variable ground contact load received by a wheel of the vehicle from a ground contact surface, based on a detection signal of a wheel speed sensor for detecting a wheel speed of the vehicle;

a state quantity estimation unit configured to estimate the stroke quantity generated in the multistage elastic member, based on the multistage elastic member and the variable ground contact load, the multistage elastic member having a load displacement characteristic of any one of the plurality of members set as an initial value; and

a characteristic change unit configured to change a setting of the initial value to an estimated load displacement characteristic, in a case where the estimated load displacement characteristic corresponding to the stroke quantity that is estimated by the state quantity estimation unit and the load displacement characteristic that is set as the initial value are different from each other,

wherein the state quantity estimation unit corrects the stroke quantity, based on a result of an estimation operation in which the estimated load displacement characteristic that is changed by the characteristic change unit is set as a changed initial value.

20. An estimation method of an estimation device that estimates a stroke quantity indicating a displacement in an up-and-down direction of a vehicle, in a multistage elastic member in which a plurality of members, each having a different load displacement characteristic indicating a relationship between a load and the displacement, are disposed, the estimation method comprising:

calculating, by a load calculation unit, a variable ground contact load received by a wheel of the vehicle from a ground contact surface, based on a detection signal of a wheel speed sensor for detecting a wheel speed of the vehicle;

estimating, by a state quantity estimation unit, the stroke quantity generated in the multistage elastic member, based on the multistage elastic member and the variable ground contact load, the multistage elastic member having a load displacement characteristic of any one of the plurality of members set as an initial value;

changing, by a characteristic change unit, a setting of the initial value to an estimated load displacement characteristic, in a case where the estimated load displacement characteristic corresponding to the stroke quantity that is estimated by the estimating and the load displacement characteristic that is set as the initial value are different from each other; and

correcting, by the state quantity estimation unit, the stroke quantity, based on a result of an estimation operation in which the estimated load displacement characteristic that is changed by the changing is set as a changed initial value.