Movable barrier operator multi-technique excess force avoidance apparatus and method

1. A method comprising: at a movable barrier operator:

using a first technique to detect force as is applied with respect to selective movement of a movable barrier to provide a first detected force result;

using a second technique, which is different from the first technique, to detect the force to provide a second detected force result;

using the first and second detected force result to assess whether the movable barrier operator has available a reliable indication of the force;

using the reliable indication of the force during normal operation when the reliable indication of the force is available;

taking a predetermined action when the reliable indication of the force is not available.

2. The method of claim 1 wherein the first technique is based upon at least one of the following phenomena:

revolutions per a given time period of a rotating member of a movable barrier operator motor;

time between pulses of a revolutions per minute sensor;

elapsed time as occurs between specific positions of the movable barrier during movable barrier travel;

observed change in impedance of a positional potentiometer;

back electromotive force as produced by a movable barrier operator direct current motor;

elapsed time as occurs between instances of movable barrier operator motor brush switching events;

elapsed time as occurs between movable barrier operator motor slippage events; and

mechanical clutch slippage.

3. The method of claim 2 wherein the phenomena of elapsed time as occurs between specific positions of the movable barrier during movable barrier travel includes at least one of:

elapsed time as occurs between a movable barrier travel limit and an intermediate pass point;

elapsed time as occurs between an intermediate pass point and a movable barrier travel limit;

elapsed time as occurs between at least two intermediate pass points;

elapsed time as occurs between sensed indicia of absolute position.

4. The method of claim 1 wherein the first technique and the second technique are each based upon at least one of the following phenomena:

revolutions per a given time period of a rotating member of a movable barrier operator motor;

time between pulses of a revolutions per minute sensor;

elapsed time as occurs between specific positions of the movable barrier during movable barrier travel;

observed change in impedance of a positional potentiometer;

back electromotive force as produced by a movable barrier operator direct current motor;

elapsed time as occurs between instances of movable barrier operator motor brush switching events;

elapsed time as occurs between movable barrier operator motor slippage events; and

mechanical clutch slippage.

5. The method of claim 1 wherein using a first technique to detect force includes using the first technique to detect force as is being presently applied to selectively move the movable barrier.

6. The method of claim 1 wherein:

using a first technique to detect force includes using the first technique to detect force as is being presently applied to selectively move the movable barrier;

using a second technique to detect force includes using the second technique to detect force as is being presently applied to selectively move the movable barrier.

7. The method of claim 1 wherein:

using a first technique to detect force includes using a first processing platform to use the first technique; and

using a second technique to detect force includes using a second processing platform to use the second technique.

8. The method of claim 7 wherein using a second processing platform to use the second technique includes using a second processing platform to use both the first technique and another technique to detect force as is being presently applied to selectively move the movable barrier.

9. The method of claim 1 wherein using a first technique and using a second technique includes using a first processing platform to use both the first and second technique.

10. The method of claim 1 wherein using the first and second detected force result to asses whether the movable barrier operator has available a reliable indication of the force includes comparing the first and second detected force results with one another.

11. The method of claim 10 wherein comparing the first and second detected force results with one another includes comparing a resultant difference with at least a first threshold.

12. The method of claim 1 wherein taking a predetermined action includes automatically halting movement of the movable barrier.

13. The method of claim 1 wherein taking a predetermined action includes automatically reversing movement of the movable barrier.

14. A method for use by a movable barrier operator comprising:

providing a first and second controller;

providing travel limit information to both the first and second controller;

providing movable barrier travel information to both the first and second controller;

maintaining a history of previous movable barrier travels at the second controller; at the first controller:

selectively causing the movable barrier to move from a first position to a second position, wherein the second position has associated therewith a first travel limit; at the second controller while the first controller selectively causes the movable barrier to move to the second position:

using the travel limit information, the movable barrier travel information, and the history of previous movable barrier travels to determine when movement of the movable barrier by the first controller should be over-ridden by the second controller.

15. The method of claim 14 wherein providing travel limit information includes providing at least one of an upper position limit and a lower position limit.

16. The method of claim 15 wherein providing travel limit information includes providing at least both of an upper position limit and a lower position limit.

17. The method of claim 14 wherein providing movable barrier travel information includes providing information regarding revolutions per a given time period as corresponds to a revolving member of a movable barrier operator motor.

18. The method of claim 14 wherein maintaining a history of previous movable barrier travels includes maintaining a history of a distance traversed by the movable barrier when moving to the second position.

19. The method of claim 14 wherein using the travel limit information, the movable barrier travel information, and the history of previous movable barrier travels to determine when movement of the movable barrier by the first controller should be over-ridden by the second controller includes determining when a present confluence of the travel information and the travel limit information is inconsistent with the history of previous movable barrier travels.

20. A movable barrier operator comprising:

a first force detector having an output comprising a first indication of present force as is being exerted during movement of a movable barrier, which first indication is based, at least in part, upon a first technique to ascertain the present force;

a second force detector having an output comprising a second indication of present force as is being exerted during movement of a movable barrier, which second indication is based, at least in part, upon a second technique to ascertain the present force and which second technique is different from the first technique;

a comparison unit that is operably coupled to the outputs of the first and second force detector and that has a measured force unreliability indicator output.

21. The movable barrier operator of claim 20 and further comprising an operation over-ride unit that is operably responsive to the measured force unreliability indicator output.

22. The movable barrier operator of claim 21 wherein the operation over-ride unit comprises a predetermined action output.

23. The movable barrier operator of claim 20 and further comprising first control means that is operably coupled to the measured force unreliability indicator output for controlling the movable barrier operator pursuant to a first control strategy when the present force is being reliably detected.

24. The movable barrier operator of claim 23 and further comprising second control means that is operably coupled to the measured force unreliability indicator output for controlling the movable barrier operator pursuant to a second control strategy when the present force is not being reliably detected.

25. A method comprising:

at a movable barrier operator:

using a first technique based on a predefined parameter to prevent an excess application of force at least a first predetermined potential movable barrier operator position;

using a second technique, which is different from the first technique, based on predefined parameter to prevent an excess application of force at least the first predetermined potential movable barrier operator position;

using the first and second techniques that are based on the predefined parameter to assess whether the movable barrier operator will reliably avoid an application of excess force at the first predetermined potential movable barrier operator position;

conducting normal operation of the movable barrier operator when the application of excess force will be avoided;

taking a predetermined action when the first and second techniques indicate that the application of excess force may not be avoided.