Vehicle steering system

Abstract

An apparatus has a chassis that has a pair of rear wheels that passively rotate and a pair of front wheel sets. Each pair of front wheel sets has an upright with an affixed motor. A front wheel is fixed relative to the upright and engages with the motor. A linkage connects the chassis to each of the uprights and is configured to move the uprights in a first range of motion. A linkage actuator actuates the linkage.

What is claimed is: 
     
         1 . An apparatus comprising:
 a chassis;   a pair of rear wheels passively rotatably coupled to the chassis;   a pair of front wheel sets, wherein each pair of front wheel sets comprises:
 an upright; 
 a motor fixed to the upright; and 
 a front wheel fixed relative to the upright and engaged with the motor; 
   a linkage coupling the chassis to each of the uprights of the pair of front wheel sets, wherein the linkage is configured to move the uprights in a first range of motion; and   a linkage actuator for actuating the linkage.   
     
     
         2 . The apparatus of  claim 1 , further comprising a controller fixed to the chassis for sending control signals to the motors and the linkage actuator. 
     
     
         3 . The apparatus of  claim 2 , further comprising a pair of trailing link actuators, and wherein each front wheel set comprises a trailing link connecting the upright to one of the pair of trailing link actuators. 
     
     
         4 . The apparatus of  claim 3 , wherein the trailing link is configured to allow movement of the upright in a second range of motion different than the first range of motion. 
     
     
         5 . The apparatus of  claim 4 , wherein the first range of motion and the second range of motion are substantially orthogonal. 
     
     
         6 . The apparatus of  claim 1 , wherein the linkage includes Ackermann steering geometry. 
     
     
         7 . The apparatus of  claim 2 , wherein the controller is configured to send a motor signal to at least one of the motors so as to at least one of (1) rotate the front wheels at different rotational speeds, and (2) rotate the front wheels in different rotational directions. 
     
     
         8 . The apparatus of  claim 3 , wherein the controller is configured to send an actuator signal to at least one of the trailing link actuators so as to actuate at least one of the trailing links. 
     
     
         9 . The apparatus of  claim 1 , wherein each of the pair of rear wheels comprise a coefficient of friction less than a coefficient of friction of each of the pair of front wheels. 
     
     
         10 . The apparatus of  claim 1 , wherein the pair of rear wheels are coupled to by an axle that is configured to pivot relative to the chassis. 
     
     
         11 . A method of moving a vehicle along a ground surface in a general direction of a curve, wherein the curve comprises a curve radius and a center point, and wherein the vehicle comprises a plurality of driven front wheels and a plurality of passive rear wheels, and wherein the plurality of driven front wheels comprise an inside front wheel disposed proximate to the center point and an outside front wheel disposed distal from the center point, the method comprising:
 moving the vehicle in a default direction of travel by applying a first force from a ground-engaging surface of at least one of the plurality of driven front wheels to the ground surface;   turning a leading surface of the plurality of driven front wheels in a wheel direction away from a general direction of the curve; and   applying a second force from the ground-engaging surface of at least one of the plurality of driven front wheels to the ground surface, so as to move the vehicle in the general direction of the curve.   
     
     
         12 . The method of  claim 11 , wherein applying the second force comprises accelerating a rotational speed of the outside wheel to an accelerated rotational speed greater than a default rotational speed applied to the outside wheel during the default moving operation. 
     
     
         13 . The method of  claim 11 , wherein applying the second force comprises decelerating a rotational speed of the inside wheel to a decelerated rotational speed less than a default rotational speed applied to the inside wheel during the default moving operation. 
     
     
         14 . The method of  claim 11 , wherein applying the second force comprises reversing a direction of rotation of the inside wheel to a reversed rotational direction opposite a default rotational direction applied to the inside wheel during the default moving operation. 
     
     
         15 . The method of  claim 11 , wherein applying the second force comprises changing a center of gravity of the vehicle. 
     
     
         16 . The method of  claim 15 , wherein changing the center of gravity of the vehicle comprises elevating at least a portion of the vehicle proximate the outside wheel to a raised elevation higher than a default elevation of the portion of the vehicle during the default moving operation. 
     
     
         17 . A method of controlling a vehicle, the method comprising:
 sending a default signal to a vehicle control module, wherein the vehicle control module controls at least one of a rotational speed of a wheel, a rotational direction of the wheel, a center of gravity of the vehicle, and an elevation of a portion of the vehicle;   receiving a desired direction signal from a vehicle driving controller, wherein the desired direction signal is associated with a desired direction of a turn of the vehicle;   based at least in part on the desired direction signal, sending a linkage direction signal to the control module so as to change a directional position of the wheel, wherein the changed directional position of the wheel is in a direction generally opposite the desired direction of the turn of the vehicle; and   based at least in part on the desired direction signal, sending a command signal to the control module so as to turn the vehicle generally in the desired direction.   
     
     
         18 . The method of  claim 17 , wherein the command signal increases the rotational speed of the wheel to a command signal speed greater than a default speed associated with the default signal. 
     
     
         19 . The method of  claim 17 , wherein the command signal decreases the rotational speed of the wheel to a command signal speed less than a default speed associated with the default signal. 
     
     
         20 . The method of  claim 17 , wherein the command signal reverses the rotational direction of the wheel to a command signal rotational direction opposite a default rotation associated with the default signal. 
     
     
         21 . The method of  claim 17 , wherein the command signal changes a center of gravity of the vehicle to a command signal center of gravity different than a default center of gravity associated with the default signal. 
     
     
         22 . The method of  claim 17 , wherein the command signal changes the elevation of the portion of the vehicle to a command signal elevation different than a default elevation associated with the default signal.