Steering system and method for independent steering of wheels

• US 20100106375A1
• Filed: 10/27/2008
• Published: 04/29/2010
• Est. Priority Date: 10/27/2008
• Status: Active Grant

• Current Assignee: A.K. Waizuddin Ahmed, Rama B. Bhat, Vaibhav Rawat
• Original Assignee: Concordia University
• Inventors: Bhat, R.B., Rawat, Vaibhav, Ahmed, A.K. Waizuddin
• Granted Patent: US 8,126,612 B2
• Time in Patent Office: Days
• US Class Current: 701/42
• CPC Class Codes: B62D 3/12 of rack-and-pinion type
• CPC Class Codes: B62D 5/008 Changing the transfer ratio between the steering wheel and the steering gear by variable supply of energy, e.g. by using a superposition gear
• 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 7/09 characterised by means varying the ratio between the steering angles of the steered wheels varying the ratio automatically depending on driving conditions B62D6/00

Abstract

A steering system comprises a steering wheel adapted to receive a driver'"'"'s rotational input. Left and right wheel units are rotatable along a steering angle for adjusting a direction of the vehicle during the driving movement. A steering mechanism converts the rotational input to a variation of the steering angle of the wheel units. The steering mechanism comprises a steering shaft connected to the steering wheel, and gear steering units for each said wheel unit. The gear steering units are connected to the steering shaft for mechanically converting the rotational input to steering outputs for both said wheel units to concurrently vary the steering angle of said wheel units. Independent steering units for each wheel unit each adjusting the steering angle of a respective one of the wheel units independently from the rotational input and from the other wheel unit.

Claims

1. A steering system comprising:

a steering wheel adapted to receive a driver'"'"'s rotational input;

left and right wheel units adapted to rollingly interface a vehicle to a ground for driving movement of the vehicle, each wheel unit being rotatable along a steering angle for adjusting a direction of the vehicle during the driving movement;

a steering mechanism for converting the rotational input to a variation of the steering angle of the wheel units, the steering mechanism comprising a steering shaft connected to the steering wheel, and gear steering units for each said wheel unit, the gear steering units connected to the steering shaft for mechanically converting the rotational input to steering outputs for both said wheel units to concurrently vary the steering angle of said wheel units, and independent steering units for each said wheel unit, the independent steering units each adjusting the steering angle of a respective one of the wheel units independently from the rotational input and from the other wheel unit.

2. The steering system according to claim 1, wherein the gear steering units each comprise a planetary gear system for receiving the rotational output from the steering shaft, and a rack and pinion assembly connected to the planetary gear system for transmitting the steering output to a respective wheel unit in a translational degree of freedom.

3. The steering system according to claim 2, wherein a sun gear of the planetary gear system is secured to the steering shaft, and a pinion of the rack and pinion assembly is secured to a planet carrier of the planetary gear system.

4. The steering system according to claim 3, wherein the steering shaft, the sun gears and the pinions rotate about a coincident axis.

5. The steering system according to claim 2, wherein the independent steering units each have an electric motor outputting rotational motion to an independent-steer gear, with the independent-steer gear being meshed with a ring of the respective planetary gear system to adjust the steering angle of the respective wheel unit.

6. The steering system according to claim 2, wherein the planetary gear systems are symmetrically similar.

7. The steering system according to claim 1, wherein the independent steering units are each connected to one of the gear steering units to adjust the steering angle through the gear steering unit.

8. A method for adjusting a steer angle of wheels of a vehicle comprising:

measuring a steering input from the driver of the vehicle and a vehicle velocity;

calculating a reference yaw rate for the vehicle from the steering input and from the vehicle velocity;

measuring an actual yaw rate for the vehicle;

determining a corrective value for a first wheel of the vehicle as a function of the reference yaw rate and the actual yaw rate, and of the steering input;

adjusting the steer angle of said first wheel by said corrective value.

9. The method according to claim 8, wherein determining a corrective value comprises determining a corrective value for at least a second wheel, and adjusting the steer angle comprises adjusting the steer angle of said first wheel and said second wheel independently from one another.

10. The method according to claim 8, wherein adjusting the steer angle comprises actuating an electric motor to mechanically adjust the steer angle of said first wheel.

11. The method according to claim 8, wherein determining a corrective value comprises identifying said first wheel from a direction of said steering input and from an understeer/oversteer characteristic of the vehicle.

12. The method according to claim 11, wherein identifying said first wheel comprises identifying the outer wheel as said first wheel for an understeer characteristic for the vehicle.