Motor stall and trailer lift
A method detects and prevents stall of a drive motor of an autonomous electric tractor. A stall detector receives, at intervals, a motor current value from a drive circuit of the autonomous electric tractor, determines when the motor current value reaches or exceeds a first current threshold and applies brakes, inhibits a throttle controlling the drive motor, and sets a motor stall flag. A method determines a height above the ground of a landing gear of a trailer coupled with a tractor. A lift detector controls a hydraulic pump to pump a hydraulic fluid into a chamber of a piston coupled to a fifth wheel of the tractor to raise the fifth wheel. The lift detector senses, at intervals as the fifth wheel rises, a pressure value of the hydraulic fluid in the chamber and processes the pressure value to determine when the landing gear is lifted off the ground.
1. A method for detecting and preventing stall of a drive motor of an autonomous electric tractor, comprising:
receiving, at intervals, a motor current value from a drive circuit of the autonomous electric tractor;
determining when the motor current value reaches or exceeds a first current threshold; and
when the motor current value reaches or exceeds the first current threshold:
applying brakes; and
inhibiting a throttle controlling the drive motor.
2. The method of claim 1 , further comprising:
setting a motor stall flag;
determining a stall location based on a current location of the autonomous electric tractor; and
starting a timer.
3. The method of claim 2 , further comprising:
determining when, after exceeding the first current threshold, the motor current value is below a second current threshold or when the timer reaches a first time-limit; and
when the motor current value is below the second current threshold or when the timer reaches the first time-limit:
clearing the motor stall flag; and
un-inhibiting the throttle.
4. The method of claim 3 , further comprising:
waiting until the motor stall flag is cleared; and
implementing a stall recovery routine for the autonomous electric tractor.
5. The method of claim 4 , the step of implementing the stall recovery routine when attempting to couple with a trailer further comprising:
controlling the autonomous electric tractor to move forward a predetermined distance; and
controlling the autonomous electric tractor to attempt coupling with the trailer using a greater throttle setting than previously used.
6. The method of claim 4 , the step of implementing the stall recovery routine when attempting to reverse a trailer against at least one dock pad of a loading dock further comprising:
controlling the autonomous electric tractor to move forward a predetermine distance;
controlling the autonomous electric tractor to reverse the trailer against the at least one dock pad; and
determining the trailer is docked when the motor stall flag is set.
7. The method of claim 4 , the step of implementing the stall recovery routine of an apron maneuver when the autonomous electric tractor is traversing an apron of an autonomous yard further comprising:
triggering remote assist functionality;
receiving an instruction to retry the apron maneuver;
controlling the autonomous electric tractor to reverse direction for a predetermined distance; and
controlling the autonomous electric tractor to repeat the apron maneuver with a higher throttle setting.
8. The method of claim 7 , further comprising:
detecting when the current location of the autonomous electric tractor passes the stall location; and
setting the throttle of the autonomous electric tractor to a nominal throttle setting.
9. A method for preventing stall of a motor of an autonomous vehicle, comprising:
receiving, at intervals, a motor current value from a drive circuit of the autonomous electric tractor; and
when the motor current value reaches or exceeds a first current threshold:
applying brakes;
inhibiting a throttle controlling the drive motor for a predefined period from the determining the motor current value reached or exceeded the first current; and then
un-inhibiting the throttle.
10. The method of claim 9 , further comprising:
determining a stall location based on a current location of the autonomous electric tractor;
implementing, after the waiting, a stall recovery routine for the autonomous electric tractor.
11. The method of claim 10 , the stall recovery routine comprising:
determining the stall location indicates the autonomous electric tractor is attempting to hitch to a trailer;
controlling the autonomous electric tractor to move forward a predetermined distance; and
controlling the autonomous electric tractor to attempt coupling with the trailer using a greater throttle setting than previously used.
12. The method of claim 10 , the stall recovery routine comprising:
determining the stall location indicates the autonomous electric tractor is attempting to reverse a trailer against at least one dock pad of a loading dock;
controlling the autonomous electric tractor to move forward a predetermine distance;
controlling the autonomous electric tractor to reverse the trailer against the at least one dock pad; and
determining the trailer is docked when the motor current value reaches or exceeds the first current threshold.
13. The method of claim 10 , the stall recovery routine comprising:
determining the stall location indicates the autonomous electric tractor is traversing an apron of an autonomous yard;
controlling the autonomous electric tractor to reverse direction for a predetermined distance; and
controlling the autonomous electric tractor to repeat the apron maneuver with a higher throttle setting.
14. The method of claim 13 , the stall recovery routine further comprising:
detecting when the current location of the autonomous electric tractor passes the stall location; and
setting the throttle of the autonomous electric tractor to a nominal throttle setting.