Integrated gearbox/encoder and control system

1. An integrated gearbox/encoder and control system, comprising:

a gearbox with a first output shaft that couples to a mechanical load;

a first sensor integrated into said gearbox, said first sensor detecting a rotary position of said first output shaft of said gearbox;

a motor with a second output shaft that couples to said gearbox;

motor drive electronics connected to said motor controlling motive power supplied to said motor to control motion of said motor;

a second sensor coupled to said second output shaft of said motor detecting rotary position of said second output shaft of said motor; and

a system controller connected to said motor drive electronics, said first sensor and said second sensor, said system controller controlling motion of said motor through said motor drive electronics, said system controller operable to measure a gearbox backlash by

controlling said motor to advance at a low velocity and a low acceleration until detecting motion at said first sensor,

thereafter storing a first detected rotary position of said first sensor and a first detected rotary position of said second sensor,

controlling said motor to reverse direction and advance at said low velocity and said low acceleration until detecting motion at said first sensor,

thereafter storing a second detected rotary position of said first sensor and a second detected rotary position of said second sensor, and

calculating a backlash from a difference between a difference between said second and first detected rotary positions of said second sensor and a difference between said second and first detected rotary positions of said first sensor.

2. The integrated gearbox/encoder and control system of claim 1 , wherein:

said system controller is operable to periodically measure said gearbox backlash.

3. The integrated gearbox/encoder and control system of claim 1 , wherein:

said system controller is operable to measure said gearbox backlash once each initial application of electric power.

4. The integrated gearbox/encoder and control system of claim 1 , wherein:

said system controller is further operable to

compare said measured gearbox backlash to a standard,

continue system controller operation upon a first result of said comparison, and

abort system controller operation and request remedial action upon a second result of said comparison opposite to said first result.

5. The integrated gearbox/encoder and control system of claim 4 , wherein:

said system controller is operable to

compare said measured gearbox backlash to a sum of an initial measured backlash and an empirically determined constant,

said first result of said comparison is said backlash less than or equal to said sum, and

said second result of said comparison is said backlash greater than said sum.

6. The integrated gearbox/encoder and control system of claim 1 , wherein:

said system controller is further operable to

detect commanded direction reversal of said motor, and

upon detection of a commanded direction reversal of said motor add said measured gearbox backlash to a calculated position control term in controlling motion of said motor.

7. The integrated gearbox/encoder and control system of claim 1 , wherein:

said system controller is further operable to

detect a commanded change in control of said motor from zero acceleration to non-zero acceleration, and

upon detection of said commanded change in control of said motor from zero acceleration to non-zero acceleration, command said motor at low acceleration until said second sensor indicates an movement corresponding to said measured gearbox backlash greater than said first sensor indicates movement.

8. The integrated gearbox/encoder and control system of claim 1 , wherein:

said system controller is further operable to

detect commanded change in control of said motor from non-zero acceleration to zero acceleration, and

upon detection of said commanded change in control of said motor from non-zero acceleration to zero acceleration, command said motor at reduced acceleration for an amount before said commanded change in control of said motor from non-zero acceleration to zero acceleration corresponding to said measured gearbox backlash.

9. A integrated gearbox/encoder and control system comprising:

a gearbox with a first output shaft that couples to a mechanical load;

a first sensor integrated into said gearbox, said first sensor detecting a rotary position of said first output shaft of said gearbox;

a motor with a second output shaft that couples to said gearbox;

motor drive electronics connected to said motor controlling motive power supplied to said motor to control motion of said motor;

a second sensor coupled to said second output shaft of said motor detecting rotary position of said second output shaft of said motor;

a current sensor connected to said motor drive electronics detecting drive current from said motor drive electronics to said motor; and

a system controller connected to said motor drive electronics, said first sensor and said second sensor, said system controller controlling motion of said motor through said motor drive electronics, said system controller operable to

determine a vibration signature for said motor from said drive current,

compare said vibration signature to a standard,

continue system controller operation upon a first result of said comparison, and

abort system controller operation and request remedial action upon a second result of said comparison opposite to said first result.

10. A integrated gearbox/encoder and control system comprising:

a gearbox with a first output shaft that couples to a mechanical load;

a first sensor integrated into said gearbox, said first sensor detecting a rotary position of said first output shaft of said gearbox;

a motor with a second output shaft that couples to said gearbox;

motor drive electronics connected to said motor controlling motive power supplied to said motor to control motion of said motor;

a second sensor coupled to said second output shaft of said motor detecting rotary position of said second output shaft of said motor; and

a system controller connected to said motor drive electronics, said first sensor and said second sensor, said system controller controlling motion of said motor through said motor drive electronics, said system controller operable to

determine a deflection characteristic for said motor from said first sensor and said second sensor,

compare said deflection characteristic to a standard,

continue system controller operation upon a first result of said comparison, and

abort system controller operation and request remedial action upon a second result of said comparison opposite to said first result.

11. A method of motor control comprising the steps of:

detecting a rotary position of an output shaft of a gearbox connected to a load;

driving an input shaft of the gearbox with a motor;

supplying motive power to the motor;

detecting rotary position of the input shaft of the gearbox;

controlling the motive power supplied to the motor in conjunction with the detected rotary positions of the gearbox input shaft and output shaft to control position of the load; and

measuring a gearbox backlash by

controlling said motor to advance at a low velocity and a low acceleration until detecting motion at said first sensor,

thereafter storing a first detected rotary position of said first sensor and a first detected rotary position of said second sensor,

controlling said motor to reverse direction and advance at said low velocity and said low acceleration until detecting motion at said first sensor,

thereafter storing a second detected rotary position of said first sensor and a second detected rotary position of said second sensor, and

calculating a backlash from a difference between a difference between said second and first detected rotary positions of said second sensor and a difference between said second and first detected rotary positions of said first sensor.

12. The method of claim 11 , wherein:

said step of measuring a gearbox backlash includes periodically measuring the gearbox backlash.

13. The method of claim 12 , wherein:

said step of periodically measuring the gearbox backlash includes measuring the gearbox backlash once each initiation of the method.

14. The method of claim 11 , further comprising the steps of:

comparing the measured gearbox backlash to a standard;

continuing operation upon a first result of the comparison; and

aborting operation and requesting remedial action upon a second result of the comparison opposite to the first result.

15. The integrated gearbox/encoder and control system of claim 14 , wherein:

said step of comparing the measured gearbox backlash to a standard compares the measured gearbox backlash to a sum of an initial measured backlash and an empirically determined constant;

said first result of said comparison is the backlash less than or equal to said sum, and

said second result of said comparison is the backlash greater than said sum.

16. The method of claim 11 , further comprising the steps of:

detecting a commanded direction reversal of the motor; and

upon detection of a commanded direction reversal of the motor adding the measured gearbox backlash to a calculated position control term in controlling motion of the load.

17. The method of claim 11 , further comprising the steps of:

detecting a commanded change in control of the motor from zero acceleration to non-zero acceleration; and

upon detection of the commanded change in control of the motor from zero acceleration to non-zero acceleration, commanding the motor at low acceleration until the detected rotary position of the input shaft of the gearbox indicates a movement corresponding to said measured gearbox backlash greater than the detected rotary of the output shaft of the gearbox indicates movement.

18. The method of claim 11 , further comprising the steps of:

detecting a commanded change in control of the motor from non-zero acceleration to zero acceleration; and

upon detection of a commanded change in control of the motor from non-zero acceleration to zero acceleration, commanding the motor at reduced acceleration for an amount before the commanded change in control of the motor from non-zero acceleration to zero acceleration corresponding to the measured gearbox backlash.

19. A method of motor control comprising the steps of:

detecting a rotary position of an output shaft of a gearbox connected to a load;

driving an input shaft of the gearbox with a motor;

supplying motive power to the motor;

detecting rotary position of the input shaft of the gearbox;

controlling the motive power supplied to the motor in conjunction with the detected rotary positions of the gearbox input shaft and output shaft to control position of the load;

detecting drive current of the motor;

determining a vibration signature for the motor from the detected drive current;

comparing the vibration signature to a standard;

continuing operation upon a first result of the comparison; and

aborting system operation and requesting remedial action upon a second result of the comparison opposite to the first result.

20. A method of motor control, comprising the steps of:

detecting a rotary position of an output shaft of a gearbox connected to a load;

driving an input shaft of the gearbox with a motor;

supplying motive power to the motor;

detecting rotary position of the input shaft of the gearbox;

controlling the motive power supplied to the motor in conjunction with the detected rotary positions of the gearbox input shaft and output shaft to control position of the load;

determining a deflection characteristic for the motor from the detected rotary positions of the input and output of the gearbox;

comparing the deflection characteristic to a standard;

continuing operation upon a first result of the comparison; and

aborting operation and requesting remedial action upon a second result of the comparison opposite to the first result.