Steering method for a trailing section of an articulated vehicle

Abstract

This invention relates generally to systems used to steer trailing sections of articulated vehicles and trailers. The preferred embodiment of this invention is a steerable dolly that can be manually and/or automatically switched among multiple modes. The dolly receives its primary input from the angle of the rear of the front trailer (or other towing vehicle). There are at least two modes. In one mode the wheels of the dolly are steered in the opposite direction as the rear trailer, providing more maneuverability. In the other mode the wheels are steered in the same direction, providing a more stable mode. It is envisioned that the more stable mode would be used at high speeds while the more maneuverable mode would be used at lower speeds. There is also disclosed an alternate steering algorithm, which provides for additional maneuverability beyond that of the mode in which the wheels are steered in an opposite direction.

What we claim is:  
     
         1 . A trailer dolly for connecting a rear trailer to a front trailer comprising: 
 a tongue;    a steering axle assembly which is rotatable with respect to said tongue;    a gear switch control device;    a means for shifting steering ratios further comprised of a rotational input, a rotational output, and a plurality of steering ratios;    a means for said tongue to rotate with respect to a front trailer;    a means for translating the rotation of said tongue with respect to a front trailer into a rotational output;    a means for translating a rotational input into rotation of said steering axle assembly with respect to said tongue; and    a means for a rear trailer to rotate with respect to said tongue.    
     
     
         2 . A trailer dolly as in  claim 1  further comprising a neutral-lock device comprised of a rotational input and a rotational output.  
     
     
         3 . A trailer dolly as in  claim 2  wherein: 
 said means for said tongue to rotate with respect to a front trailer is a hitch bar;  
 said means for translating the rotation of said tongue with respect to a front trailer into a rotational output is a front partial circular track gear train;  
 said means for translating a rotational input into rotation of said steering axle assembly with respect to said tongue is a lower rear partial circular track gear train; and  
 said means for a rear trailer to rotate with respect to said tongue is a double fifth wheel on a central pivot mounting bar.  
 
     
     
         4 . A trailer dolly as in  claim 3  wherein: 
 said rotational output from said front partial circular track gear train is said rotational input to said means for shifting steering ratios;  
 said rotational output from said neutral-lock device is said rotational input to said lower rear partial circular track gear train; and  
 said rotational output from said means for shifting steering ratios is said rotational input to said neutral-lock device.  
 
     
     
         5 . A trailer dolly as in  claim 4  wherein said means for shifting steering ratios may be switched to select from at least one positive steering ratio approximately between 0.6 and 0.8 and at least one negative steering ratio approximately between −1 and −6 using said gear switch control device.  
     
     
         6 . A trailer dolly as in  claim 1  further comprising an oversteer device and a means for translating the rotation of a rear trailer with respect to said tongue into a rotational output, wherein said oversteer device further comprises a first rotational input, a second rotational input, and a rotational output.  
     
     
         7 . A trailer dolly as in  claim 6  further comprising a neutral-lock device comprised of a rotational input and a rotational output.  
     
     
         8 . A trailer dolly as in  claim 7  wherein: 
 said means for said tongue to rotate with respect to a front trailer is a hitch bar;  
 said means for translating the rotation of said tongue with respect to a front trailer into a rotational output is a front partial circular track gear train;  
 said means for translating a rotational input into rotation of said steering axle assembly with respect to said tongue is a lower rear partial circular track gear train;  
 said means for a rear trailer to rotate with respect to said tongue is a double fifth wheel on a central pivot mounting bar, and  
 said means for translating the rotation of a rear trailer with respect to said tongue into a rotational output is an upper rear partial circular track gear train.  
 
     
     
         9 . A trailer dolly as in  claim 8  wherein: 
 said rotational output from said front partial circular track gear train is said first rotational input to said oversteer device;  
 said rotational output from said upper rear partial circular track gear train is said second rotational input to said oversteer device;  
 said rotational output from said oversteer device is said rotational input to said means for shifting steering ratios;  
 said rotational output from said means for shifting steering ratios is said rotational input to said neutral-lock device; and  
 said rotational output from said neutral-lock device is said rotational input to said lower rear partial circular track gear train.  
 
     
     
         10 . A trailer dolly as in  claim 9  wherein said means for shifting steering ratios may be switched to select from at least one positive steering ratio approximately between 0.6 and 0.8 and at least one negative steering ratio approximately between −1 and −6 using said gear switch control box.  
     
     
         11 . A trailer dolly as in  claim 10  wherein said oversteer device further comprises a planetary gear set which combines said rotational output from said upper rear partial circular track gear train with said rotational output from said front partial circular track gear train, resulting in said rotational output from said oversteer device, which acts as said rotational input to said means for shifting steering ratios.  
     
     
         12 . A method for steering a trailing section attached to follow a leading section of an articulated mobility device with a plurality of steering ratios available, wherein said trailing section further comprises a steering axle assembly, comprising the steps of: 
 Sensing the speed of said articulated mobility device;    Determining the appropriate steering ratio to apply to said trailing section based upon the sensed speed; and    Applying the appropriate steering ratio to steer said trailing section as it follows said leading section.    
     
     
         13 . A method for steering a trailing section attached to follow a leading section of an articulated mobility device with a plurality of steering ratios available, wherein said trailing section further comprises a steering axle assembly, comprising the steps of: 
 Sensing the orientation of said trailing section with respect to said leading section;    Determining the appropriate steering ratio to apply to the trailing section based upon the sensed orientation; and    Applying the appropriate steering ratio to steer said trailing section as it follows said leading section.    
     
     
         14 . A method as in  claim 13  further comprising the step of decreasing the steering ratio being applied as said articulated mobility device undergoes cornering motion.  
     
     
         15 . A method for steering as in  claim 13  further comprising the step of applying a steering ratio more towards the positive end of the available range of steering ratios when said articulated mobility device is experiencing primarily forward motion and applying a steering ratio more towards the negative end of the available range of steering ratios when said articulated mobility device is experiencing primarily cornering motion.  
     
     
         16 . A method for steering as in  claim 13  further comprising the steps of: 
 Determining if an oversteer correction is necessary to correct the path of said trailing section so that it more closely tracks the path of said leading section during primarily cornering motion, and  
 Applying the appropriate oversteer correction to steer said trailing section so that the path of movement for said trailing section closely tracks the path of said leading section.  
 
     
     
         17 . A method as in  claim 16  further comprising the step of applying a steering ratio more towards the positive end of the available range of steering ratios when said articulated mobility device is experiencing primarily forward motion and applying a steering ratio more towards the negative end of the available range of steering ratios when said articulated mobility device is experiencing primarily cornering motion.  
     
     
         18 . A method as in  claim 12  further comprising the step of applying a steering ratio more towards the positive end of the available range of steering ratios when said articulated mobility device is experiencing highway speeds, and applying steering ratios more towards the negative end of the available range of steering ratios when said articulated mobility device is experiencing cornering speeds.  
     
     
         19 . A method for steering a trailer dolly with a steering axle assembly connecting a rear trailer to a leading trailer comprising the steps of: 
 Sensing the relative or absolute orientation of said rear trailer with respect to said leading trailer in an approximately horizontal plane, or sensing the rate of change of said relative or absolute orientation of said rear trailer with respect to said leading trailer in an approximately horizontal plane;    Determining the appropriate steering ratio to apply to the trailer dolly in a given situation based upon the sensed orientation or rate of change of orientation; and    Steering said dolly in order to apply an appropriate steering ratio.    
     
     
         20 . A method as in  claim 19  wherein said sensed orientation or rate of change of orientation is used to determine if said dolly is experiencing primarily cornering motion or primarily forward motion.  
     
     
         21 . A method as in  claim 20  further comprising the step of applying a steering ratio more towards the positive end of the available range of steering ratios when said dolly is experiencing primarily forward motion and applying a steering ratio more towards the negative end of the available range of steering ratios when said dolly is experiencing primarily cornering motion.  
     
     
         22 . A method as in  claim 20  further comprising the steps of: 
 Determining if an oversteer correction is necessary to correct the path of said dolly so that it more closely tracks the path of said leading trailer during primarily cornering motion, and  
 Applying the appropriate oversteer correction to steer said dolly so that the path of movement for said rear trailer closely tracks the path of said leading trailer.  
 
     
     
         23 . A method as in  claim 21  further comprising the steps of: 
 Determining if an oversteer correction is necessary to correct the path of said dolly so that it more closely tracks the path of said leading trailer during primarily cornering motion, and  
 Applying the appropriate oversteer correction to steer said dolly so that the path of movement for said rear trailer closely tracks the path of said leading trailer.  
 
     
     
         24 . A method as in  claim 19  wherein the appropriate steering ratio is selected manually from the available range of steering ratios depending upon the particular circumstances.  
     
     
         25 . A method as in  claim 21  wherein the appropriate steering ratio is automatically and continuously selected from the available range of steering ratios based upon the sensed orientation.