Automatic brake verification system

1. A method of testing a braking device in a drivetrain of a vehicle which includes at least one tractive element coupled to an electric traction motor, the method comprising:

applying the braking device to the tractive element;

using an electronic controller, causing the traction motor to apply a predetermined force to the tractive element;

using the controller, monitoring the tractive element for movement while the force is being applied;

initially setting the predetermined force at a magnitude that will not cause movement of the tractive element when the braking device is applied;

increasing the force until movement of the tractive element occurs; and

recording the magnitude of the force which causes movement of the tractive element.

2. The method of claim 1 further comprising:

modulating the force applied to the tractive element so as to drive the tractive element at a substantially constant speed; and

recording the force required to drive the tractive element at the substantially constant speed.

3. The method of claim 1 further comprising using the controller to apply the braking device before applying the predetermined force to the tractive element.

4. The method of claim 1 further comprising using the controller to confirm that the braking device is applied before applying the predetermined force to the tractive element.

5. The method of claim 1 wherein the braking device is a friction service brake.

6. The method of claim 1 wherein the braking device is a friction parking brake.

7. The method of claim 1 further comprising displaying the results of the test to the driver.

8. The method of claim 1 further comprising storing at least one parameter representative of the test for later retrieval.

9. A system for testing a braking device in a drivetrain of a vehicle, comprising:

(a) a prime mover coupled to a power source;

(b) at least one electric traction motor electrically coupled to the power source, the traction motor coupled to at least one tractive element;

(c) at least one braking device arranged to act on the tractive element; and

(d) an electronic controller operably connected to the traction motor, the controller configured to:

(i) cause the traction motor to apply a predetermined force to the tractive element while the braking device is applied to the tractive element;

(ii) monitor the tractive element for movement while the force is being applied;

(iii) initially set the predetermined force at a magnitude that will not cause motion of the tractive element when the braking device is applied;

(iv) increase the force until movement of the tractive element occurs; and

(v) record the magnitude of the force which causes movement of the tractive element.

10. The system of claim 9 wherein:

(a) the predetermined force is of a magnitude that should not cause movement of the tractive element when the braking device is applied, if the braking device is operating properly; and

(b) the controller is programmed to declare the braking device to be operating properly if the tractive element does not move during the test.

11. The system of claim 9 wherein the controller is further programmed to:

(vi) after step (v), modulate the force applied to the tractive element as to drive the tractive element at a substantially constant speed; and

(vii) record the force required to drive the tractive element at the substantially constant speed.

12. The system of claim 9 wherein the controller is further programmed to apply the braking device before applying the predetermined force to the tractive element.

13. The system of claim 9 wherein the controller is further programmed to confirm that the braking device is applied before applying the predetermined force to the tractive element.

14. The system of claim 9 wherein the controller is further programmed to display the results of the test to the driver.

15. The system of claim 9 wherein the controller is further programmed to store at least one parameter representative of the test for later retrieval.