초록 ▼

Methods and apparatus for steering a vehicle are disclosed. A vehicle in accordance with an exemplary embodiment of the present invention is capable of operating in a first steering mode and a second steering mode. The vehicle may comprise an input device capable of providing an input signal indica

Methods and apparatus for steering a vehicle are disclosed. A vehicle in accordance with an exemplary embodiment of the present invention is capable of operating in a first steering mode and a second steering mode. The vehicle may comprise an input device capable of providing an input signal indicating that operation in the second steering mode is desired. The vehicle may comprise an electronic control unit (ECU) capable of providing an enabling signal when the ECU determines that operation in the second steering mode is appropriate for the present riding conditions.

대표청구항 ▼

What is claimed is: 1. A vehicle for traveling along the ground, the vehicle comprising: at least one rear wheel; at least one front wheel; an actuator coupled to the at least one rear wheel for rotating the at least one rear wheel about a steering axis; an input device operable to select one of a

What is claimed is: 1. A vehicle for traveling along the ground, the vehicle comprising: at least one rear wheel; at least one front wheel; an actuator coupled to the at least one rear wheel for rotating the at least one rear wheel about a steering axis; an input device operable to select one of a plurality of steering modes, the input device providing an input signal corresponding to the selected one of the plurality of steering modes; a means for providing an enabling signal for enabling the selected one of the plurality of steering modes, the means for providing an enabling signal including at least one sensor and a comparator, the comparator operably coupled to the at least one sensor for detecting a degree of slippage between either one of the front and rear wheels and the ground, the comparator comparing the degree of slippage to a threshold and generating the enabling signal when the degree of slippage is greater than the threshold; and a controller responsive to the input signal and the enabling signal for controlling the actuator to rotate the at least one rear wheel in accordance with the selected one of the plurality of steering modes. 2. The vehicle of claim 1, wherein the plurality of steering modes includes a front only steering mode. 3. The vehicle of claim 1, wherein the plurality of steering modes includes a tight turning radius steering mode. 4. The vehicle of claim 3, wherein the at least one front wheel has a steering axis, the at least one front wheel and the at least one rear wheel rotate in an opposite-phase relationship about their relative steering axes when the tight turning radius steering mode is selected. 5. The vehicle of claim 3, wherein a ratio of a rear wheel steering angle of the vehicle to a front wheel steering angle of the vehicle is less than about zero when the tight turning steering mode is selected. 6. The vehicle of claim 5, wherein the ratio of the rear wheel steering angle of the vehicle to the front wheel steering angle of the vehicle is about negative one. 7. The vehicle of claim 1, wherein the plurality of steering modes includes a first steering mode and a second steering mode, the vehicle has a first turning radius when the first steering mode is selected and a second turning radius when the second steering mode is selected; and the second turning radius is smaller than the first turning radius. 8. The vehicle of claim 1, wherein the plurality of steering modes includes a crab steering mode. 9. The vehicle of claim 8, wherein a ratio of a rear wheel steering angle of the vehicle to a front wheel steering angle of the vehicle is greater than about zero when the crab steering mode is selected. 10. The vehicle of claim 9, wherein the ratio of the rear wheel steering angle of the vehicle to the front wheel steering angle of the vehicle is about one. 11. The vehicle of claim 8, wherein the at least one front wheel has a steering axis, the at least one front wheel and the at least one rear wheel rotate in a same-phase relationship about their relative steering axes when the crab steering mode is selected. 12. The vehicle of claim 1, wherein the input device comprises an electric switch. 13. The vehicle of claim 1, wherein the vehicle comprises more than one rear wheel. 14. The vehicle of claim 13, wherein the actuator steers all the rear wheels of the vehicle. 15. The vehicle of claim 1, wherein the at least one rear wheel does not rotate about the steering axis when the first steering mode is selected. 16. The vehicle of claim 1, wherein the at least one sensor comprises a steering input sensor producing a steering input signal indicative of a position of a steering input device of the vehicle. 17. The vehicle of claim 16, wherein the at least one sensor includes a yaw acceleration sensor measuring the acceleration of the vehicle in a lateral direction and generating a yaw acceleration signal, the comparator receives the yaw acceleration signal and the steering input signal and generates the enabling signal in response to a comparison of the yaw acceleration signal and the steering input signal. 18. The vehicle of claim 1, wherein the vehicle comprises: a first rear wheel and a second rear wheel; the first rear wheel rotatable about a first steering axis by a first steering angle and the second rear wheel rotatable about a second steering axis by a second steering angle. 19. The vehicle of claim 18, wherein the first steering angle is equal to the second steering angle. 20. The vehicle of claim 18, wherein the first steering angle is less than the second steering angle. 21. The vehicle of claim 18, wherein the first steering angle is greater than the second steering angle. 22. The vehicle of claim 1, wherein the input device comprises a switch disposed on an arm of a handlebar of the vehicle. 23. The vehicle of claim 22, wherein: the switch is disposed proximate a grip; and the switch and the grip are positioned and dimensioned such that the switch can be actuated by a thumb of a hand while another portion of the hand remains in contact with the grip. 24. The vehicle of claim 22, wherein: the switch is disposed proximate a grip; and the switch and the grip are positioned and dimensioned such that the switch can be actuated by a thumb of a hand while another portion of the hand grips the grip. 25. The vehicle of claim 22, further including a throttle mechanism disposed on a second arm of the handlebar. 26. The vehicle of claim 1, wherein the at least one sensor includes a vehicle acceleration sensor and a wheel rotation sensor, the vehicle acceleration sensor measuring the linear acceleration of the vehicle and generating a vehicle acceleration signal, the wheel rotation sensor measuring the acceleration of a ground contacting portion of one of the at least one rear and front wheels and generating a wheel rotation signal, the comparator receives the vehicle acceleration signal and the wheel rotation signal and detects inconsistency between the vehicle acceleration and the wheel rotation signals, the comparator comparing the inconsistency to a threshold. 27. A method comprising the steps of: providing a vehicle having at least one rear wheel and an actuator coupled to the at least one rear wheel for rotating the wheel about a steering axis; receiving an input signal from an input switch; providing an enabling signal for enabling a second steering mode of the vehicle when a degree of slippage is greater than a threshold; producing a control signal in response to the input signal and the enabling signal for actuating the actuator to rotate the at least one rear wheel about the steering axis thereof. 28. A vehicle comprising: at least one rear wheel; an actuator coupled to the at least one rear wheel for rotating the at least one rear wheel about a steering axis; a sensor array including a plurality of sensors each generating a sensor signal, the plurality of sensors including a vehicle acceleration sensor and a wheel rotation sensor, the vehicle acceleration sensor including an accelerometer positioned on the vehicle and measuring the linear acceleration of the vehicle, the vehicle acceleration sensor generating a first sensor signal indicative of the vehicle acceleration; the wheel rotation sensor coupled to at least one of the wheels and measuring the acceleration of a ground contacting portion of the at least one of the wheels, the wheel rotation sensor generating a second sensor signal indicative of the acceleration of the ground contacting portion of the at least one rear wheel; an ECU coupled to the actuator and the sensor array; and the ECU calculating a steering angle responsive to the first and the second sensor signals and providing a control signal to the actuator so that the at least one wheel is rotated about the steering axis by the steering angle. 29. A recreational vehicle having a first rear wheel, a second rear wheel, a pair of front wheels, and a steering member operably coupled to the pair of front wheels and adapted to be operated by the operator to steer the pair of front wheels about respective front steering axes, the vehicle comprising: an input device switch positioned on the steering member and switchable by the operator between a plurality of steering mode selections, the input device switch generating an input signal corresponding to the selected steering mode; at least one actuator operably coupled to the first and second rear wheels and adapted to selectively and independently rotate the first and second rear wheels about respective first and second rear steering axes; a sensor array including a plurality of sensors each generating a sensor signal, the plurality of sensors including a vehicle movement sensor and a wheel rotation sensor, the vehicle movement sensor positioned on the vehicle and measuring the linear movement of the vehicle, the vehicle movement sensor generating a first sensor signal indicative of the vehicle movement; the wheel rotation sensor coupled to at least one of the wheels and measuring the movement of a ground contacting portion of the at least one of the wheels, the wheel rotation sensor generating a second sensor signal indicative of the movement of the ground contacting portion of the at least one wheel; and a control unit coupled to the sensor array, the input device and the actuator, the control unit receiving the input signal, the first signal and the second signal, the control unit storing at least one threshold parameter, the control unit including a comparator operable to detect inconsistency between the first sensor signal and the second sensor signal and compare the inconsistency to the at least one threshold parameter, the comparator operable to generate an enabling signal enabling the selected steering mode when the inconsistency is greater than the at least one threshold parameter, the control unit controlling the actuator to affect the selective and independent rotation of first and second rear wheels about respective first and second rear steering axes in accordance with the selected steering mode. 30. The recreational vehicle of claim 29 wherein the sensor array also includes a left and a right rear wheel angle sensor generating left and right rear wheel angle signals, the control unit receiving the left and right rear wheel angle signals. 31. The recreational vehicle of claim 29 wherein the at least one actuator includes a first actuator coupled to the first rear wheel and a second actuator coupled to the second rear wheel. 32. The recreational vehicle of claim 29 wherein the at least one actuator includes an electric motor. 33. The recreational vehicle of claim 29 wherein said sensor array includes a vehicle position sensor, the vehicle position sensor including a global positioning system, the vehicle position sensor transmitting a vehicle position signal to the control unit. 34. The recreational vehicle of claim 29 wherein the plurality of vehicle steering modes includes a tight turning radius steering mode, wherein the first and second rear wheels are rotated about respective first and second rear steering axes in an opposite phase relationship with respect to the rotation of the front wheels about the front steering axes. 35. The recreational vehicle of claim 29 wherein the plurality of vehicle steering modes includes a crab steering mode wherein said first and second rear wheels are rotated about respective first and second rear steering axes in a same-phase relationship with respect to the rotation of the front wheels about the front steering axes. 36. The recreational vehicle of claim 29 wherein the plurality of vehicle steering modes includes a front-only steering mode wherein the first and second rear wheels are positioned parallel to a longitudinal axis of the vehicle and only the pair of front wheels may be rotated by the steering member. 37. The recreational vehicle of claim 29 wherein the actuator may be deactivated with first and second wheels in a non-parallel position relative to a longitudinal axis of the vehicle, thereby locking first and second wheels in the non-parallel position. 38. The recreational vehicle of claim 29, wherein the vehicle movement sensor comprises a vehicle acceleration sensor measuring the linear acceleration of the vehicle, and the wheel rotation sensor measures the acceleration of the ground contacting portion. 39. A recreational vehicle having a vehicle frame, a pair of front wheels rotatably coupled to the vehicle frame and a steering member operably coupled to the pair of front wheels and adapted to be operated by the operator to steer the pair of front wheels about respective front wheel axes, the vehicle comprising: a pair of rear wheel assemblies, each rear wheel assembly including a rear wheel, a knuckle rotatably coupled to said rear wheel and having an upper end and a lower end, upper and lower ball joints respectively disposed on the upper and lower ends of the knuckle, and upper and lower support arms pivotably coupled at one end to the upper and lower ball joints, respectively, and coupled at the opposite end to the vehicle frame, the knuckle defining a rear steering axis; an input device switch positioned on the steering member and switchable by the operator between a plurality of steering mode selections, the input device generating an input signal corresponding to the selected steering mode; at least one actuator operably coupled to the pair of rear wheel assemblies and adapted to selectively and independently rotate the rear wheels about the rear steering axes; a sensor array including a plurality of sensors each generating a sensor signal; and a control unit coupled to the sensor array, the input device and the actuator, the control unit receiving the sensor signal of each of the plurality of sensors and the input signal, the control unit storing at least one threshold parameter, the control unit including a comparator, the comparator comparing the sensor signal to said at least one threshold parameter, the control unit generating an enabling signal enabling the selected steering mode, the enabling signal based on said comparator's comparisons, the control unit controlling said actuator to affect the selective and independent rotation of the rear wheels about respective said rear steering axes in accordance with the selected steering mode. 40. The recreational vehicle of claim 39 wherein the plurality of sensors includes a vehicle acceleration sensor, the vehicle acceleration sensor includes an accelerometer positioned on the vehicle and measuring the linear acceleration of the vehicle. 41. The recreational vehicle of claim 40 wherein the plurality of sensors includes a wheel rotation sensor, the wheel rotation sensor is coupled to at least one of the wheels and measures the acceleration of a ground contacting portion of the at least one of the wheels, the vehicle acceleration sensor generates a first sensor signal indicative of the linear acceleration of the vehicle, the wheel rotation sensor generates a second sensor signal indicative of the acceleration of the ground contacting portion of the at least one wheel, the comparator comparing said first signal to said second signal. 42. The recreational vehicle of claim 39 wherein the sensor array also includes left and right rear wheel angle sensors respectively generating left and right rear wheel angle signals, the control unit receiving said left and right rear wheel angle signals. 43. The recreational vehicle of claim 39 wherein the at least one actuator includes a first actuator coupled to the first rear wheel and a second actuator coupled to the second rear wheel. 44. The recreational vehicle of claim 39 wherein the at least one actuator includes an electric motor. 45. The recreational vehicle of claim 39 wherein the sensor array includes a vehicle position sensor, the vehicle position sensor including a global positioning system, the vehicle position sensor transmitting a vehicle position signal to the control unit. 46. The recreational vehicle of claim 39 wherein the plurality of vehicle steering modes includes a tight turning radius steering mode, wherein the first and second rear wheels are rotated about respective first and second rear steering axes in an opposite phase relationship with respect to the rotation of the front wheels about the front steering axes. 47. The recreational vehicle of claim 39 wherein the plurality of vehicle steering modes includes a crab steering mode wherein said first and second rear wheels are rotated about respective first and second rear steering axes in a same-phase relationship with respect to the rotation of the front wheels about the front steering axes. 48. The recreational vehicle of claim 39 wherein the plurality of vehicle steering modes includes a front-only steering mode wherein the first and second rear wheels are positioned parallel to a longitudinal axis of the vehicle and only the pair of front wheels may be rotated by the steering member.