Power assisted steering for motorized pallet truck

Abstract

A system for controlling the acceleration, deceleration, braking, travel speed, and power assisted steering of a pallet truck, comprising setting a steering system and a traction system performance as a function of a position and rate of change of position of a control arm in a vertical axis and a horizontal axis of rotation.

The invention claimed is: 
     
       1. A method for controlling a motorized vehicle, comprising:
 measuring a steering angle of a steering control, wherein the steering angle is determined according to a rotation of the steering control about an approximately vertical axis of rotation; 
 setting a level of performance of a traction system as a function of the steering angle of the steering control; and 
 adjusting the level of performance of the traction system as the steering control is rotated between a first steering angle and a second steering angle, wherein the level of performance of the traction system indicates a maximum allowable travel speed of the motorized vehicle. 
 
     
     
       2. A method for controlling a motorized vehicle, comprising:
 measuring a steering angle of a steering control, wherein the steering angle is determined according to a rotation of the steering control about an approximately vertical axis of rotation; 
 measuring a braking position of the steering control, wherein the braking position is determined according to a rotation of the steering control about an approximately horizontal axis of rotation; 
 setting a level of performance of a traction system as a function of the steering angle of the steering control; and 
 adjusting the level of performance of the traction system, as the steering control is rotated between a first steering angle and a second steering angle, according to both the steering angle and the braking position of the steering control. 
 
     
     
       3. A method for controlling a motorized vehicle, comprising:
 measuring a steering angle of a steering control, wherein the steering angle is determined according to a rotation of the steering control about an approximately vertical axis of rotation; 
 setting a level of performance of a traction system as a function of the steering angle of the steering control; and 
 adjusting the level of performance of the traction system as the steering control is rotated between a first steering angle and a second steering angle, wherein the level of performance of the traction system decreases when the steering control approaches a maximum turning angle. 
 
     
     
       4. A method for controlling a motorized vehicle, comprising:
 measuring a steering angle of a steering control, wherein the steering angle is determined according to a rotation of the steering control about an approximately vertical axis of rotation; 
 setting a level of performance of a traction system as a function of the steering angle of the steering control; and 
 adjusting the level of performance of the traction system as the steering control is rotated between a first steering angle and a second steering angle, wherein the level of performance of the traction system is adjusted by an on-board processor based on a position of the steering control. 
 
     
     
       5. The method according to  claim 4  including accessing a data map to set the level of performance of the traction system according to predetermined values in the data map that correspond to the position of the steering control. 
     
     
       6. The method according to  claim 1  wherein the level of performance of the traction system further indicates a level of vehicle acceleration. 
     
     
       7. A method for controlling a motorized vehicle, comprising:
 measuring a steering angle of a steering control, wherein the steering angle is determined according to a rotation of the steering control about an approximately vertical axis of rotation; 
 setting a level of performance of a traction system as a function of the steering angle of the steering control; 
 adjusting the level of performance of the traction system as the steering control is rotated between a first steering angle and a second steering angle; and 
 dividing the steering angle into predefined discrete ranges of motion about the vertical axis of rotation, wherein the level of performance of the traction system is set according to the where the steering control is located within the predefined discrete ranges of motion. 
 
     
     
       8. The method according to  claim 7  wherein the steering angle is divided into three or more predefined discrete ranges of motion. 
     
     
       9. The method according to  claim 2  including identifying the braking position as predefined discrete ranges of motion about the horizontal axis of rotation, wherein the level of performance of the traction system is set according to where the steering control is located within the predefined discrete ranges of motion about both the approximately vertical and horizontal axes of rotation. 
     
     
       10. A method for controlling a motorized vehicle, comprising:
 measuring a steering angle of a steering control, wherein the steering angle is determined according to a rotation of the steering control about an approximately vertical axis of rotation; 
 setting a level of performance of a traction system as a function of the steering angle of the steering control; and 
 adjusting the level of performance of the traction system as a function of a rate of change of position of the steering control as the steering control is rotated between a first steering angle and a second steering angle, wherein the rate of change of position identifies an angular acceleration of the steering control about the approximately vertical axis of rotation. 
 
     
     
       11. The method according to  claim 10  wherein the rate of change of position further identifies an angular acceleration of the steering control about an approximately horizontal axis of rotation. 
     
     
       12. The method according to  claim 10  including accessing a data map to set the level of performance according to predetermined settings based on a discrete position of the steering control and the rate of change of position of the steering control. 
     
     
       13. The method according to  claim 10  including further setting the level of performance of the traction system as a function of a rate of travel of the motorized vehicle. 
     
     
       14. A method for controlling a motorized vehicle, comprising:
 measuring a position of a steering control, wherein the position is determined according to a rotation of the steering control about one or more axes of rotation; 
 detecting a steer effort applied to the steering control; 
 selecting a level of power assistance provided by a steering motor, wherein the steering motor is configured to provide a plurality of levels of power assistance greater than zero power, and wherein the level of power assistance is selected from the plurality of levels as a function of the position of the steering control; and 
 actuating the steering motor when the detected steer effort is greater than a threshold torque value. 
 
     
     
       15. The method according to  claim 14  wherein the position of the steering control is measured about a horizontal axis of rotation. 
     
     
       16. The method according to  claim 14  wherein the position of the steering control is measured about a vertical axis of rotation. 
     
     
       17. The method according to  claim 16  wherein the steering motor is set to a first level of power assistance with the steering control positioned in an approximate center position, and wherein the steering motor is set to a second level of power assistance when the steering control is positioned in a maximum left or right steering position, the second level of power assistance greater than the first level of power assistance. 
     
     
       18. The method according to  claim 15  wherein the steering motor is set to a first level of power assistance with the steering control positioned in an approximate center position, and wherein the steering motor is set to a second level of power assistance with the steering control positioned in a braking position, the second level of power assistance greater than the first level of power assistance. 
     
     
       19. The method according to  claim 18  wherein the braking position is identified by a substantially vertical position of the steering control. 
     
     
       20. The method according to  claim 16  including dividing the rotation of the steering control into predefined discrete ranges of motion about the vertical axis of rotation, wherein the level of power assistance is selected according to where the steering control is located within the predefined discrete ranges of motion. 
     
     
       21. The method according to  claim 20  wherein the rotation of the steering control is divided into three or more predefined discrete ranges of motion. 
     
     
       22. The method according to  claim 14  including dividing the rotation of the steering control into predefined discrete ranges of motion about the one or more axes of rotation, wherein the level of power assistance of the steering motor is further selected according to where the steering control is located within the predefined discrete ranges of motion. 
     
     
       23. The method according to  claim 14  wherein the level of power assistance of the steering motor varies depending if the motorized vehicle is traveling in a low speed mode or a high speed mode. 
     
     
       24. A system for controlling a pallet truck, comprising:
 a control arm configured to steer a drive wheel that controls a direction of travel of the pallet truck; 
 a steer motor configured to provide torque for steering the drive wheel; and 
 a processor configured to vary an amount of the torque provided by the steer motor according to a rate of change of position of the control arm with respect to time, wherein the rate of change of position of the control arm is monitored in one or both of a vertical direction of movement and a horizontal direction of movement. 
 
     
     
       25. A system for controlling a pallet truck, comprising:
 a control arm configured to steer a drive wheel that controls a direction of travel of the pallet truck; 
 a steer motor configured to provide torque for steering the drive wheel; and 
 a processor configured to vary an amount of the torque provided by the steer motor according to a rate of change of position of the control arm with respect to time, wherein the processor further varies the amount of torque provided by the steer motor to assist in steering the steer drive wheel according to an amount of torque applied to the control arm. 
 
     
     
       26. A method for controlling a motorized vehicle, comprising:
 measuring a position of a steering controller, wherein the position is determined according to a rotation of the steering controller about an approximately vertical axis of rotation and about an approximately horizontal axis of rotation; 
 measuring a rate of change of position of the steering controller; and 
 controlling acceleration, deceleration, braking, and travel speed of the motorized vehicle according to the position of the steering controller in conjunction with the rate of change of position of the steering controller. 
 
     
     
       27. A method for controlling a motorized vehicle, comprising:
 measuring a steering angle of a steering control, wherein the steering angle is determined according to a rotation of the steering control about an approximately vertical axis of rotation; 
 setting a level of performance of a traction system as a function of the steering angle of the steering control; and 
 adjusting the level of performance of the traction system as the steering control is rotated between a first steering angle and a second steering angle, wherein the level of performance of the traction system is further selected as a function of a rate of travel of the motorized vehicle. 
 
     
     
       28. The method according to  claim 14  wherein the level of power assistance provided by the steering motor is further selected from the plurality of levels of power assistance as a function of the detected steer effort. 
     
     
       29. The method according to  claim 14  wherein the level of power assistance provided by the steering motor is further selected as a function of a rate of travel of the motorized vehicle. 
     
     
       30. The method according to  claim 23  wherein the level of power assistance of the steering motor varies for the same steer effort applied to the steering control. 
     
     
       31. The method according to  claim 1  wherein the traction system comprises a traction motor, and wherein the level of performance of the traction motor is adjusted as the steering control is rotated between the first steering angle and the second steering angle. 
     
     
       32. The method of claim 1, wherein setting the level of performance of the traction system comprises setting a level of vehicle acceleration, and wherein adjusting the level of performance of the traction system comprises adjusting the level of vehicle acceleration as the steering control is rotated between the first steering angle and the second steering angle.  
     
     
       33. The method of claim 2, wherein the level of performance of the traction system is further adjusted according to a rate of rotation of the steering control between the first steering angle and the second steering angle.  
     
     
       34. The method of claim 3, wherein setting the level of performance of the traction system comprises setting an allowable vehicle acceleration, and wherein adjusting the level of performance of the traction system comprises adjusting the allowable vehicle acceleration.  
     
     
       35. The method of claim 4, wherein the level of performance of the traction system is adjusted according to a rate of rotation of the steering control between the first steering angle and the second steering angle.  
     
     
       36. A system, comprising:
 a control arm configured to steer a vehicle;   a steering detector configured to measure a steering angle of the control arm, wherein measuring the steering angle comprises detecting a rate of change in position of the control arm with respect to time from a first steering angle to a second steering angle about an approximately vertical axis of rotation;   a throttle configured to generate a speed request as a function of the steering angle, wherein a maximum allowable travel speed of a vehicle traction system is associated with the speed request; and   a processor configured to reduce the maximum allowable travel speed of the vehicle traction system based, at least in part, on the rate of change in position of the control arm with respect to time from the first steering angle to the second steering angle, wherein the rate of change in position of the control arm identifies an angular acceleration of the control arm about the approximately vertical axis of rotation.    
     
     
       37. The system according to claim 36 wherein the processor is further configured to modify the speed request based, at least in part, on the rate of change in position of the control arm.  
     
     
       38. The system according to claim 36 wherein the steering detector is further configured to detect a change in position of the control arm comprising angle data associated with the position of the control arm in the horizontal direction, and wherein the maximum allowable travel speed is reduced based, at least in part, on a detected change in the angle data.  
     
     
       39. The system according to claim 38, wherein the processor is further configured to determine the maximum allowable travel speed based, at least in part, on the angle data.  
     
     
       40. The system of claim 36, wherein the processor is further configured to reduce a maximum allowable vehicle acceleration based, at least in part, on the rate of change in position of the control arm from the first steering angle to the second steering angle.  
     
     
       41. A system, comprising:
 a control arm configured to steer a vehicle;   a steering detector configured to measure a position of the control arm according to a rotation of the control arm about an approximately vertical axis of rotation and about an approximately horizontal axis of rotation, wherein the steering detector is further configured to measure a rate of change in position of the control arm with respect to time, wherein the change in position of the control arm comprises a first steering position and a second steering position;   a throttle configured to generate a speed request associated with a traction system; and   a processor configured to reduce the speed request associated with the traction system based, at least in part, on the position of the control arm in conjunction with the rate of change in position of the control arm with respect to time when the control arm is moved from the first steering position to the second steering position.    
     
     
       42. The system according to claim 41 wherein the first steering position comprises a central position of the control arm, and wherein the second steering position is associated with a maximum turning angle of the vehicle.  
     
     
       43. The system according to claim 41 wherein a maximum allowable travel speed is associated with the speed request, and wherein the processor is further configured to modify the maximum allowable travel speed based on the rate of change in position of the control arm.  
     
     
       44. The system according to claim 41 wherein the steering detector is further configured to detect a change in position of the control arm comprising angle data associated with the first steering position and the second steering position, and wherein the speed request is reduced based, at least in part, on a detected change in the angle data.  
     
     
       45. The system of claim 41, wherein the steering detector is further configured to detect a rate of change in the position of the control arm with respect to time in a vertical direction, and wherein the processor is further configured to reduce the speed request associated with the traction system based, at least in part, on the rate of change in the position of the control arm in the vertical direction.  
     
     
       46. The system of claim 41, wherein the processor is further configured to reduce the speed request associated with the traction system based, at least in part, on the rate of change in the position of the control arm when the control arm is moved from the first steering position to the second steering position.  
     
     
       47. The system of claim 41, wherein the rate of change in position of the control arm identifies an angular acceleration of the control arm about the approximately vertical axis of rotation.  
     
     
       48. An apparatus, comprising:
 means for detecting a change in position of a steering control about an axis of rotation, wherein the change in position comprises a first position of the steering control and a second position of the steering control;   means for detecting a steer effort applied to the steering control;   means for selecting a level of power assistance provided by a steering motor, wherein the steering motor is configured to provide a plurality of levels of power assistance greater than zero power, wherein the level of power assistance is selected from the plurality of levels as a function of the position of the steering control, and wherein the selected level of power assistance associated with the second position is greater than the selected level of power assistance associated with the first position for a same amount of detected steer effort; and   means for actuating the steering motor when the detected steer effort is greater than a threshold torque value.    
     
     
       49. The apparatus according to claim 48 wherein the change in position further comprises an approximately vertical rotation of the steering control about the axis of rotation toward a braking position.  
     
     
       50. An apparatus, comprising:
 means for detecting a change in position of a steering control about an axis of rotation, wherein the change in position comprises an approximately vertical rotation of the steering control about the axis of rotation toward a braking position;   means for detecting a steer effort applied to the steering control;   means for selecting a level of power assistance provided by a steering motor, wherein the steering motor is configured to provide a plurality of levels of power assistance greater than zero power, and wherein the level of power assistance is selected from the plurality of levels as a function of the position of the steering control; and   means for actuating the steering motor when the detected steer effort is greater than a threshold torque value.    
     
     
       51. The apparatus according to claim 50 wherein the level of power assistance increases as the steering control approaches the braking position.  
     
     
       52. The apparatus according to claim 51 wherein the braking position is associated with an approximately vertical orientation of the steering control.