Vehicle Steering Control Without Mechanical Connection Between the Steering Wheel and the Steered Wheels

• US 20080177445A1
• Filed: 03/24/2006
• Published: 07/24/2008
• Est. Priority Date: 04/01/2005
• Status: Active Grant

• Current Assignee: Michelin Recherche et Technique SA (Compagnie Generale DES Etablissements Michelin SCA)
• Original Assignee: Michelin Recherche et Technique SA (Compagnie Generale DES Etablissements Michelin SCA)
• Inventors: Auguet, Thierry, Sebe, Marc
• Granted Patent: US 8,036,793 B2
• Time in Patent Office: Days
• US Class Current: 701/42
• CPC Class Codes: B62D 6/003 in order to control vehicle yaw movement, i.e. around a vertical axis B62D6/007 takes precedence
• CPC Class Codes: B62D 7/159 characterised by computing methods or stabilisation processes or systems, e.g. responding to yaw rate, lateral wind, load, road condition

Abstract

Steering control system with variable ratio, comprising a control member (2) available to a driver to act on the vehicle steering, the said control member being able to be manoeuvred within a maximum range (θ_max) between a stop to the left and a stop to the right and delivering a requested steering signal (θ) quantified in terms of amplitude and direction, the said steering system comprising at least one actuator (3) for acting on the steering angle of the at least one steered wheel, the said steering system comprising a controller (4) using as input variables at least the speed of the vehicle (V) and the said requested steering signal (θ) in order to determine, for each of the actuators, a control angle (α) according to which the actuator is controlled for the steering, comprising a first unit (41) for determining, at least according to the speed of the vehicle (V) and preferably according to the maximum transverse acceleration (γ_{y max}) of the vehicle, a maximum steering (β_max) on the single steered wheel on an equivalent bicycle model of the vehicle, a second unit (42) for determining a gearing-down ratio (RD) according to the said maximum range (θ_max) of the control member and the said maximum steering angle (β_max), a final unit (43) for determining the said steering angle or angles (α) according to the said gearing-down ratio (RD) and the said requested steering signal (θ).

Claims

1-16. -16. (canceled)

17. A steering control system with variable ratio for a land vehicle that includes two or more wheels, at least one of which is steered, the vehicle including a control member available to a driver for steering the vehicle, the control member being maneuverable within a maximum range between a leftward stop and a rightward stop and delivering a requested steering signal quantified in terms of amplitude and direction, the steering control system comprising:

at least one actuator configured to act on a steering angle of the at least one steered wheel; and

a controller that uses as input variables at least a speed of the vehicle and the requested steering signal in order to determine, for each actuator, a control angle according to which the actuator is controlled for steering the vehicle, wherein the controller includes;

a first unit configured to determine, at least according to the speed of the vehicle and a parameter characteristic of an equilibrium of the vehicle, a maximum steering angle on a steered wheel of an equivalent bicycle model of the vehicle,

a second unit configured to determine a gearing-down ratio according to the maximum range of the control member and the maximum steering angle, and

a third unit configured to determine a steering angle according to the gearing-down ratio and the requested steering signal.

18. A system according to claim 17,

wherein the first unit is configured to determine the maximum steering angle from a minimum steering radius of the vehicle, and

wherein the minimum steering radius is determined according to the speed of the vehicle.

19. A system according to claim 17, wherein the parameter characteristic of the equilibrium of the vehicle is a maximum transverse acceleration parameter of the vehicle.

20. A system according to claim 18, wherein the parameter characteristic of the equilibrium of the vehicle is a maximum transverse acceleration parameter of the vehicle.

21. A system according to claim 19, wherein the maximum transverse acceleration parameter is a parameter of adjustment of the system and keeps a fixed value during a functioning of the system.

22. A system according to claim 20, wherein the maximum transverse acceleration parameter is a parameter of adjustment of the system and keeps a fixed value during a functioning of the system.

23. A system according to claim 19, wherein the maximum transverse acceleration parameter is calculated in real time according to conditions of use of the vehicle.

24. A system according to claim 20, wherein the maximum transverse acceleration parameter is calculated in real time according to conditions of use of the vehicle.

25. A system according to claim 17,

wherein the vehicle includes a steered axle with two steered wheels mechanically connected in terms of steering, and

wherein an actuator is utilized on the steered axle, so that the steering angle determined by the third unit is unique and is a function of the gearing-down ratio and the requested steering signal.

26. A system according to claim 17,

wherein the vehicle includes four steered wheels mechanically connected in terms of steering via a plurality of axles such that an actuator is utilized per axle,

wherein the third unit is configured to determine a transverse coordinate of an instantaneous center of rotation of the vehicle by determining an equivalent turning angle on the steered wheel of the equivalent bicycle model as a function of the gearing-down ratio and the requested steering signal, by marking an intersection between a straight line perpendicular to a plane of a non-steered wheel of the bicycle model and a straight line perpendicular to a plane of the steered wheel of the equivalent bicycle model turned through the equivalent turning angle, and by adopting, as a value of the transverse coordinate of the instantaneous center of rotation of the vehicle, a value of a transverse coordinate of the intersection,

wherein the system further comprises a module configured to control a steering behaviour of the vehicle to enable a determination of a longitudinal coordinate of the instantaneous center of rotation of the vehicle from the speed of the vehicle, and

wherein the third unit is configured to determine a respective control angle of each of the plurality of axles from the transverse and longitudinal coordinates of the instantaneous center of rotation of the vehicle.

27. A system according to claim 17,

wherein the vehicle includes a steered axle connected to two steered wheels,

wherein the system comprises an actuator per steered wheel, and

wherein the third unit is configured to determine an equivalent steering angle on the steered wheel of the equivalent bicycle model as a function of the gearing-down ratio and the requested steering signal, to mark an intersection between a straight line perpendicular to a plane of a non-steered wheel of the equivalent bicycle model and a straight line perpendicular to a plane of the steered wheel of the equivalent bicycle model turned through the equivalent steering angle, the intersection giving a transverse coordinate of the instantaneous center of rotation of the vehicle, and to determine a respective control angle of each of the steered wheels.

28. A system according to claim 17,

wherein the vehicle includes four steered wheels,

wherein the system comprises an actuator per steered wheel,

wherein the third unit is configured to determine an equivalent steering angle on the steered wheel of the equivalent bicycle model as a function of the gearing-down ratio and the requested steering signal, to mark an intersection between a straight line perpendicular to a plane of a non-steered wheel of the equivalent bicycle model and a straight line perpendicular to a plane of the steered wheel of the equivalent bicycle model turned through the equivalent steering angle, the intersection giving a transverse coordinate of the instantaneous center of rotation of the vehicle,

wherein the system further comprises a module configured to control a behaviour of the vehicle in terms of steering to enable a determination of a longitudinal coordinate of the instantaneous center of rotation of the vehicle from the speed of the vehicle, and

wherein the third unit determines a respective control angle of each of the steered wheels from the transverse and longitudinal coordinates of the instantaneous centre of rotation.

29. A system according to claim 17, wherein the requested steering signal delivered by the control member is an electrical signal, and wherein each actuator is electrical.

30. A system according to claim 26,

wherein the module is configured to calculate a connecting curve between an initial center of rotation at zero speed and an instantaneous transition center of rotation at a transition speed, the connecting curve being tangent to a straight line parallel to an axle of the vehicle, and

wherein the longitudinal coordinate of the instantaneous center of rotation of the vehicle is determined by reading a transverse coordinate at a site that includes the connecting curve and the straight line parallel to the axle of the vehicle for a speed of the vehicle less than the transition speed, and

wherein the longitudinal coordinate of the instantaneous center of rotation of the vehicle is equal to a longitudinal coordinate that is a function of a speed of the vehicle beyond the transition speed.

31. A system according to claim 28,

wherein the module is configured to calculate a connecting curve between an initial center of rotation at zero speed and an instantaneous transition center of rotation at a transition speed, the connecting curve being tangent to a straight line parallel to an axle of the vehicle, and

wherein the longitudinal coordinate of the instantaneous center of rotation of the vehicle is determined by reading a transverse coordinate at a site that includes the connecting curve and the straight line parallel to the axle of the vehicle for a speed of the vehicle less than the transition speed, and

wherein the longitudinal coordinate of the instantaneous center of rotation of the vehicle is equal to a longitudinal coordinate that is a function of a speed of the vehicle beyond the transition speed.

32. A system according to claim 30, wherein the connecting curve is an ellipse.

33. A system according to claim 31, wherein the connecting curve is an ellipse.

34. A system according to claim 30, where a transverse coordinate of the instantaneous center of rotation at the transition speed is determined by using as an input parameter a maximum transverse acceleration parameter of the vehicle and the transition speed.

35. A system according to claim 31, where a transverse coordinate of the instantaneous center of rotation at the transition speed is determined by using as an input parameter a maximum transverse acceleration parameter of the vehicle and the transition speed.

36. A system according to claim 34, wherein the maximum transverse acceleration parameter is a parameter for adjusting the system and keeps a fixed value during a functioning of the system.

37. A system according to claim 35, wherein the maximum transverse acceleration parameter is a parameter for adjusting the system and keeps a fixed value during a functioning of the system.

38. A system according to claim 34, wherein the maximum transverse acceleration parameter is calculated in real time according to conditions of use of the vehicle.

39. A system according to claim 35, wherein the maximum transverse acceleration parameter is calculated in real time according to conditions of use of the vehicle.