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A steering apparatus for a zero-turn radius vehicle using a steering mechanism coupled to a first set of wheel assemblies by a plurality of cables. User input to the steering mechanism causes the cables to turn the first set of wheel assemblies about a vertical axis. Specifically, the cables link th

A steering apparatus for a zero-turn radius vehicle using a steering mechanism coupled to a first set of wheel assemblies by a plurality of cables. User input to the steering mechanism causes the cables to turn the first set of wheel assemblies about a vertical axis. Specifically, the cables link the steering mechanism to cam mechanisms that are attached to each wheel assembly. The design of the cam mechanism, which preferably includes two cams of varying radii, enables the two wheel assemblies to rotate about their vertical axes at varied degrees of rotation and greater than ninety degrees from the forward facing position, thereby resulting in zero-turn radius capability.

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1. A steering apparatus for a vehicle, comprising: first and second wheel assemblies rotatably disposed on the vehicle, each wheel assembly having a first position corresponding to a forward direction of travel of the vehicle and each wheel assembly capable of rotating greater than 90 degrees from t

1. A steering apparatus for a vehicle, comprising: first and second wheel assemblies rotatably disposed on the vehicle, each wheel assembly having a first position corresponding to a forward direction of travel of the vehicle and each wheel assembly capable of rotating greater than 90 degrees from the first position about a substantially vertical axis;a steering shaft having a circumference and rotatably disposed on the vehicle;a first cable segment linking the steering shaft to the first wheel assembly;a second cable segment linking the steering shaft to the second wheel assembly;a third cable segment linking the steering shaft to the second wheel assembly;a fourth cable segment linking the steering shaft to the first wheel assembly; andwherein, when the first wheel assembly is in the first position, a portion of the first cable segment and a portion of the fourth cable segment are wrapped around the circumference of the steering shaft, and when the second wheel assembly is in the first position, a portion of the second cable segment and a portion of the third cable segment are wrapped around the circumference of the steering shaft;wherein rotation of the steering shaft in a first direction causes (i) the first cable segment to wrap around the steering shaft and rotate the first wheel assembly, (ii) the fourth cable segment to unwrap from the steering shaft and permit rotation of the first wheel assembly, (iii) the third cable segment to wrap around the steering shaft and rotate the second wheel assembly, and (iv) the second cable segment to unwrap from the steering shaft and permit rotation of the second wheel assembly; andwherein rotation of the steering shaft in a second direction causes (i) the fourth cable segment to unwrap from the steering shaft and permit rotation of the first wheel assembly, (ii) the first cable segment to unwrap from the steering shaft and permit rotation of the first wheel assembly, (iii) the second cable segment to wrap around the steering shaft and rotate the second wheel assembly, and (iv) the third cable segment to unwrap from the steering shaft and permit rotation of the second wheel assembly. 2. The steering apparatus of claim 1, further comprising a sensor mounted on the steering shaft for measuring the rotation of the steering shaft. 3. The steering apparatus of claim 2, wherein the sensor is a potentiometer. 4. The steering apparatus of claim 1, further comprising: a steering column connected to the steering shaft; anda steering input device connected to the steering column. 5. The steering apparatus of claim 1, wherein the first and second cable segments are each portions of a first unitary cable, and the third and fourth cable segments are each portions of a second unitary cable. 6. The steering apparatus of claim 1, wherein the first and fourth cable segments are each portions of a first unitary cable, and the second and third cable segments are each portions of a second unitary cable. 7. The steering apparatus of claim 1, wherein the first, second, third and fourth cable segments each have an end attached to the steering shaft. 8. The steering apparatus of claim 7, further comprising: a first cable mount extending from the steering shaft to attach the first cable segment to the steering shaft;a second cable mount extending from the steering shaft to attach the second cable segment to the steering shaft;a third cable mount extending from the steering shaft to attach the third cable segment to the steering shaft; anda fourth cable mount extending from the steering shaft to attach the fourth cable segment to the steering shaft. 9. The steering apparatus of claim 1 further comprising: a first drive device for driving a third wheel and a second drive device for driving a fourth wheel;an accelerator disposed on the vehicle; andan electronic drive control system disposed on the vehicle comprising: a first sensor in communication with the accelerator;a second sensor in communication with the steering shaft; andwherein input from the first and second sensors is used to facilitate independent adjustment of the first and second drive devices. 10. The steering apparatus of claim 9, further comprising: a first actuator in communication with the first drive device; anda second actuator in communication with the second drive device;wherein the first and second actuators facilitate independent adjustment of the respective first and second drive devices. 11. The steering apparatus of claim 10, further comprising: a third sensor in communication with the first actuator; anda fourth sensor in communication with the second actuator. 12. A vehicle steered by a steering apparatus, comprising: a first wheel assembly disposed on the vehicle and comprising a first wheel having a first axis of rotation;a second wheel assembly disposed on the vehicle and comprising a second wheel having a second axis of rotation;the first and second wheel assemblies each having a first position corresponding to a forward direction of travel of the vehicle;a third wheel driven by a first drive device and a fourth wheel driven by a second drive device, the third and fourth wheels sharing a common axis of rotation, wherein, during a turn of the vehicle, the first and second wheel assemblies are both capable of being rotated about their respective vertical axes of rotation such that the first axis of rotation and the second axis of rotation intersect at a point located generally proximate to the center point of the common axis of rotation between the third and fourth wheels;a steering shaft having a circumference and rotatably disposed on the vehicle;a first cable segment linking the steering shaft to the first wheel assembly;a second cable segment linking the steering shaft to the second wheel assembly;a third cable segment linking the steering shaft to the second wheel assembly;a fourth cable segment linking the steering shaft to the first wheel assembly; andwherein, when the first wheel assembly is in the first position, a portion of the first cable segment and a portion of the fourth cable segment are wrapped around the circumference of the steering shaft, and when the second wheel assembly is in the first position, a portion of the second cable segment and a portion of the third cable segment are wrapped around the circumference of the steering shaft;wherein rotation of the steering shaft in a first direction causes (i) the first cable segment to wrap around the steering shaft and rotate the first wheel assembly, (ii) the fourth cable segment to unwrap from the steering shaft and permit rotation of the first wheel assembly, (iii) the third cable segment to wrap around the steering shaft and rotate the second wheel assembly, and (iv) the second cable segment to unwrap from the steering shaft and permit rotation of the second wheel assembly; andwherein rotation of the steering shaft in a second direction causes (i) the fourth cable segment to unwrap from the steering shaft and permit rotation of the first wheel assembly, (ii) the first cable segment to unwrap from the steering shaft and permit rotation of the first wheel assembly, (iii) the second cable segment to wrap around the steering shaft and rotate the second wheel assembly, and (iv) the third cable segment to unwrap from the steering shaft and permit rotation of the second wheel assembly;an accelerator disposed on the vehicle; andan electronic drive control system disposed on the vehicle comprising: a first sensor in communication with the accelerator;a second sensor in communication with the steering shaft; andwherein input from the first and second sensors is used to facilitate independent adjustment of the first and second drive devices. 13. The vehicle of claim 12, wherein the second sensor is mounted on the steering shaft for measuring the rotation of the steering shaft. 14. The vehicle of claim 13, wherein the second sensor is a potentiometer. 15. The vehicle of claim 12, wherein the first and second drive devices are electric drive devices. 16. The vehicle of claim 12, further comprising: a steering column connected to the steering shaft; anda steering input device connected to the steering column. 17. The vehicle of claim 12, further comprising: a first actuator in communication with the first drive device; anda second actuator in communication with the second drive device;wherein the first and second actuators facilitate speed adjustment of the respective first and second drive devices. 18. The vehicle of claim 17, further comprising: a third sensor in communication with the first actuator; anda fourth sensor in communication with the second actuator. 19. The vehicle of claim 17, wherein the first and second drive devices are hydraulic drive devices. 20. The vehicle of claim 12, wherein the first and second cable segments are each portions of a first unitary cable and the third and fourth cable segments are each portions of a second unitary cable. 21. The vehicle of claim 12, wherein the first and fourth cable segments are each portions of a first unitary cable, and the second and third cable segments are each portions of a second unitary cable. 22. The vehicle of claim 12, wherein the first, second, third and fourth cable segments each have an end attached to the steering shaft.