Automatic system brake

1. A translation apparatus, comprising:

an elongate track;

an elongate fixed member extending parallel to the track in a fixed lengthwise position relative thereto; and

a stage mounted on the track and capable of movement along the track, the stage comprising:

a motive force generator operable to move the stage along the track,

a rotatable member coupled with the fixed member in a manner that converts movement of the stage relative to the fixed member into rotation of the rotatable member, and

a rotary brake selectively operable to apply a braking torque to the rotatable member.

2. The translation apparatus of claim 1 , in which:

the fixed member is flexible in a direction orthogonal to the length thereof;

the rotatable member comprises a pulley; and

the stage additionally comprises an idler pulley positioned to wrap the fixed member part-way around the pulley.

3. The translation apparatus of claim 1 , in which the fixed member and the rotatable member each comprise teeth.

4. The translation apparatus of claim 1 , in which the rotary brake has a default state in which the rotary brake applies the braking torque to the rotatable member and a released state in which it applies substantially no braking torque to the rotatable member.

5. The translation apparatus of claim 1 , in which the rotary brake comprises a mechanically-actuated braking mechanism for generating the braking torque and an electrically-actuated mechanism for selectively disengaging the braking mechanism.

6. The translation apparatus of claim 1 , in which the rotary brake comprises:

a magnetically-actuated braking mechanism for generating the braking torque, the magnetically-actuated braking mechanism comprising a permanent magnet; and

an electrically-actuated mechanism for selectively disengaging the braking mechanism.

7. The translation apparatus of claim 1 , in which the rotary brake comprises:

a rotatable element coupled to the rotatable member;

a fixed element fixed to the stage, the fixed element biased into contact with the rotatable element; and

an operating mechanism operable to move the fixed element out of contact with the rotatable element.

8. The translation apparatus of claim 1 , in which the rotary brake comprises:

a fixed element fixed to the stage;

a rotatable element coupled to the rotatable member, the rotatable element biased into contact with the fixed element; and

an operating mechanism operable to move the rotatable element out of contact with the fixed element.

9. The translation apparatus of claim 1 , in which:

the motive force generator comprises a linear motor rotor; and

the translation apparatus additionally comprises a linear motor stator arrayed along the track opposite the linear motor rotor.

10. The translation apparatus of claim 1 , in which the stage additionally comprises a rotary encoder coupled to the rotatable member.

11. The translation apparatus of claim 10 , in which the rotatable member comprises teeth arranged along a circumference thereof and configured to engage with the fixed member.

12. The translation apparatus of claim 11 , in which the fixed member comprises teeth arrayed along a length thereof, the teeth configured to engage with the teeth of the rotatable member.

13. The translation apparatus of claim 10 , in which the rotatable member comprises a toothed pulley, and the fixed member comprises a toothed ribbon.

14. The translation apparatus of claim 10 , in which:

the fixed member is flexible in a direction orthogonal to the length thereof and has a minimum radius of curvature; and

the rotatable member comprises a pulley having a radius no less than the minimum radius of curvature of the fixed member.

15. The translation apparatus of claim 10 , in which:

the fixed member comprises a rack, the toothed rack rigid in a direction orthogonal to the length thereof and comprising teeth arrayed therealong;

the rotatable member comprises a toothed wheel comprising teeth configured to engage with teeth of the rack.

16. The translation apparatus of claim 1 , in which:

the fixed member is flexible in a direction orthogonal to the length thereof and comprises teeth arrayed therealong;

the rotatable member comprises a pulley; and

the stage additionally comprises:

a toothed pulley positioned to wrap the fixed member part-way around the pulley, the toothed pulley comprising teeth configured to engage with the teeth of the fixed member, and

a rotary encoder rotationally coupled to the toothed pulley

17. A stage movable in translation relative to an elongate fixed member, the stage comprising:

an armature;

a motive force generator fixed to the armature and operable to move the stage relative to the fixed member;

a rotatable member configured to couple with the fixed member in a manner that converts movement of the stage relative to the fixed member to rotation of the rotatable member;

a rotary brake fixed to the armature and having a default state in which the rotary brake applies a braking torque to the rotatable member, the coupling between the rotatable member and the fixed member converting the braking torque to a braking force applied to the stage; and

a rotary encoder coupled to the rotatable member to quantify the rotation thereof.

18. The stage of claim 17 , additionally comprising a controller operable to perform operations comprising:

causing the rotary brake to release;

causing the motive force generator to generate a motive force effective to move the stage along the fixed member, and

determining a displacement of the stage relative to the fixed member in response to a signal received from the rotary encoder.

19. The stage of claim 18 , in which the controller is additionally operable to inhibit release of rotary brake unless the controller is causing the motive force generator to generate the motive force.

20. The stage of claim 17 , in which the controller is additionally operable to control operation of the motive force generator in response to the signal received from the rotary encoder.