Suspension control device

1. A suspension control device comprising:

a wheel grip state estimation means for estimating a grip state of vehicle wheels based on variations of aligning torque of wheels to be steered, the grip state representing the degree of a lateral force that tires of the vehicle wheels generate relative to the maximum degree of the lateral force that the tires generate with a percentage of allowance to a limit;

aligning torque estimation means for estimating the aligning torque on the basis of a pneumatic trail;

a vehicle rolling control means for controlling vehicle rolling; and

a control parameter setting means for setting a control parameter of the vehicle rolling control means based on at least estimated grip state of the wheel grip state estimation means.

2. The suspension control device according to claim 1 , further comprising:

a vehicle roll stiffness control means for controlling vehicle roll stiffness for restraining vehicle rolling; and

wherein the control parameter setting means sets a control parameter of the vehicle roll stiffness control means based on at least estimated grip state of the wheel grip estimation means.

3. The suspension control device according to claim 2 , wherein the wheel grip state estimation means comprises an aligning torque estimation means for estimating aligning torque generated at the wheels, a vehicle state amount detection means for detecting state amount of the vehicle, a wheel index estimation means for estimating at least one of wheel indexes including side force and a wheel slip angle relative to the wheel, and a wheel grip factor estimation means for estimating wheel grip factor relative to the wheels based on the variations of the aligning torque estimated by the aligning torque estimation means.

4. The suspension control device according to claim 3 , wherein the wheel grip state estimation means includes a reference aligning torque setting means for setting reference aligning torque based on the wheel index estimated by the wheel index estimation means and the aligning torque estimated by the aligning torque estimation means, and the wheel grip factor estimation means estimate the wheel grip factor relative to the wheels based on comparison result of the reference aligning torque determined by the reference aligning torque setting means and the aligning torque estimated by the aligning torque estimation means.

5. The suspension control device according to claim 4 , further comprising:

a driving means for conducting steering control of the vehicle, the driving means being mechanically separated from an operation means for an operator; and

a driving signal detection means for detecting driving signal of the driving means under steering control by the driving means; wherein

the aligning torque estimation means estimates the aligning torque based on detected result by the driving signal detection means.

6. The suspension control device according to claim 3 , further comprising:

a driving means for conducting steering control of the vehicle, the driving means being mechanically separated from an operation means for an operator; and

a driving signal detection means for detecting driving signal of the driving means under steering control by the driving means; wherein

the aligning torque estimation means estimates the aligning torque based on detected result by the driving signal detection means.

7. The suspension control device according to claim 2 , further comprising:

a frictional coefficient estimation means for estimating a frictional coefficient of the vehicle relative to a road surface based on the wheel grip factor estimated by the wheel grip factor estimation means; wherein

the control parameter setting means determines the control parameter at least based on the frictional coefficient estimated by the frictional coefficient estimation means.

8. The suspension control device according to claim 1 , further comprising:

a vehicle roll stiffness distribution control means for controlling vehicle roll stiffness distribution for controlling vehicle steering characteristics; and

wherein the control parameter setting means sets a control parameter of the vehicle roll stiffness distribution control means based on at least estimated grip state of the wheel grip estimation means.

9. The suspension control device according to claim 8 , wherein the wheel grip state estimation means comprises an aligning torque estimation means for estimating aligning torque generated at the wheels, a vehicle state amount detection means for detecting state amount of the vehicle, a wheel index estimation means for estimating at least one of wheel indexes including side force and a wheel slip angle relative to the wheel, and a wheel grip factor estimation means for estimating wheel grip factor relative to the wheels based on the variations of the aligning torque estimated by the aligning torque estimation means.

10. The suspension control device according to claim 9 , wherein the wheel grip state estimation means includes a reference aligning torque setting means for setting reference aligning torque based on the wheel index estimated by the wheel index estimation means and the aligning torque estimated by the aligning torque estimation means, and the wheel grip factor estimation means estimate the wheel grip factor relative to the wheels based on comparison result of the reference aligning torque determined by the reference aligning torque setting means and the aligning torque estimated by the aligning torque estimation means.

11. The suspension control device according to claim 10 , further comprising:

a driving means for conducting steering control of the vehicle, the driving means being mechanically separated from an operation means for an operator; and

a driving signal detection means for detecting driving signal of the driving means under steering control by the driving means; wherein

the aligning torque estimation means estimates the aligning torque based on detected result by the driving signal detection means.

12. The suspension control device according to claim 9 , further comprising:

a driving means for conducting steering control of the vehicle, the driving means being mechanically separated from an operation means for an operator; and

a driving signal detection means for detecting driving signal of the driving means under steering control by the driving means; wherein

the aligning torque estimation means estimates the aligning torque based on detected result by the driving signal detection means.

13. The suspension control device according to claim 8 , further comprising:

a frictional coefficient estimation means for estimating a frictional coefficient of the vehicle relative to a road surface based on the wheel grip factor estimated by the wheel grip factor estimation means; wherein

the control parameter setting means determines the control parameter at least based on the frictional coefficient estimated by the frictional coefficient estimation means.

14. The suspension control device according to claim 1 , wherein the wheel grip state estimation means comprises an aligning torque estimation means for estimating aligning torque generated at wheels, a vehicle state amount detection means for detecting state amount of the vehicle, a wheel index estimation means for estimating at least one of wheel indexes including side force and a wheel slip angle relative to the wheel, and a wheel grip factor estimation means for estimating wheel grip factor relative to the wheels based on the variations of the aligning torque estimated by the aligning torque estimation means.

15. The suspension control device according to claim 14 , further comprising:

a driving means for conducting steering control of the vehicle, the driving means being mechanically separated from an operation means for an operator; and

a driving signal detection means for detecting driving signal of the driving means under steering control by the driving means; wherein

the aligning torque estimation means estimates the aligning torque based on detected result by the driving signal detection means.

16. The suspension control device according to claim 14 , wherein the wheel grip state estimation means includes a reference aligning torque setting means for setting reference aligning torque based on the wheel index estimated by the wheel index estimation means and the aligning torque estimated by the aligning torque estimation means, and the wheel grip factor estimation means estimate the wheel grip factor relative to the wheels based on comparison result of the reference aligning torque determined by the reference aligning torque setting means and the aligning torque estimated by the aligning torque estimation means.

17. The suspension control device according to claim 16 , further comprising:

a driving means for conducting steering control of the vehicle, the driving means being mechanically separated from an operation means for an operator; and

a driving signal detection means for detecting driving signal of the driving means under steering control by the driving means; wherein

the aligning torque estimation means estimates the aligning torque based on detected result by the driving signal detection means.

18. The suspension control device according to claim 1 , further comprising:

a frictional coefficient estimation means for estimating a frictional coefficient of the vehicle relative to a road surface based on the wheel grip factor estimated by the wheel grip factor estimation means; wherein

the control parameter setting means determines the control parameter at least based on the frictional coefficient estimated by the frictional coefficient estimation means.

19. The suspension control device according to claim 1 , wherein the vehicle rolling control means controlling vehicle roll stiffness for restraining vehicle rolling.

20. The suspension control device according to claim 1 , wherein the vehicle rolling control means controlling vehicle roll stiffness distribution for controlling vehicle steering characteristics.

21. The suspension control device according to claim 1 , wherein the aligning torque comprises a reference aligning torque and an actual aligning torque, and the aligning torque estimation means estimates the reference aligning torque.