Proportional control brake

1. A proportional braking system for use with a movable surface which is movable relative to a housing, the proportional braking system comprising:

a variable displacement brake which is configured for displacement toward or away from braking engagement with the movable surface in proportion to an input command; and

a brake driver which is receptive of data reflective of movements of the movable surface relative to the housing and which issues the input command to the variable displacement brake in accordance with the data,

wherein the variable displacement brake comprises:

a first body comprising brake plates;

a second body comprising thrust plates, the second body being disposed such that the thrust plates are interleaved with the brake plates and being rotatable and movable with respect to the first body;

an elastic element that urges the second body to move toward the first body such that the thrust plates are urged toward braking engagements with the brake plates to inhibit rotations of the second body with respect to the first body;

a coil at a first side of the brake plates, which, when energized, generates a flux moment on the second body in opposition to the urging of the elastic element; and

a booster coil at a second side of the brake plates, which, when energized, generates a second flux moment on the second body in support of the urging of the elastic element.

2. The proportional braking system according to claim 1 , wherein the variable displacement brake is disposed proximate to at least one of a drive unit of the movable surface and a tip of the housing.

3. The proportional braking system according to claim 1 , wherein the variable displacement brake is disposed along a driveline of the movable surface.

4. The proportional braking system according to claim 1 , wherein:

the variable displacement brake comprises a normally engaged brake and the input command comprises a duty cycle percentage, and

an applied brake load of the normally engaged brake decreases as the input duty cycle percentage increases.

5. The proportional braking system according to claim 1 , wherein:

the variable displacement brake comprises a normally engaged brake and the input command comprises an input current, and

an applied brake load of the normally engaged brake decreases as the input current increases.

6. The proportional braking system according to claim 1 , wherein:

the variable displacement brake comprises a normally disengaged brake and the input command comprises a duty cycle percentage, and

an applied brake load of the normally disengaged brake decreases as the input duty cycle percentage decreases.

7. The proportional braking system according to claim 1 , further comprising sensors configured to sense the movements of the movable surface relative to the housing and to generate the data accordingly.

8. An aircraft, comprising:

a fuselage;

wings extending outwardly from the fuselage and comprising movable surfaces which are movable relative to the wings;

a driving system configured to drive movements of the movable surfaces relative to the wings; and

a proportional braking system configured to apply a braking load to the movable surfaces to inhibit the movements thereof relative to the wings, the proportional braking system comprising:

variable displacement brakes which are each configured for displacement toward or away from braking engagement with a corresponding one of the movable surfaces in proportion to an input command; and

a brake driver which is receptive of data reflective of movements of the movable surfaces relative to the wings and which issues input commands to the variable displacement brakes in accordance with the data,

wherein each of the variable displacement brakes comprises:

a first body comprising brake plates;

a second body comprising thrust plates, the second body being disposed such that the thrust plates are interleaved with the brake plates and being rotatable and movable with respect to the first body;

an elastic element that urges the second body to move toward the first body such that the thrust plates are urged toward braking engagements with the brake plates to inhibit rotations of the second body with respect to the first body;

a coil at a first side of the brake plates, which, when energized, generates a flux moment on the second body in opposition to the urging of the elastic element; and

a booster coil at a second side of the brake plates, which, when energized, generates a second flux moment on the second body in support of the urging of the elastic element.

9. The proportional brake system according to claim 8 , wherein the variable displacement brakes are respectively disposed proximate to at least one of a drive unit of the movable surfaces and tips of the wings.

10. The proportional brake system according to claim 8 , wherein the variable displacement brakes are disposed along drivelines of the movable surfaces.

11. The proportional brake system according to claim 8 , wherein:

at least one of the variable displacement brakes comprises a normally engaged brake and the input command comprises a duty cycle percentage, and

an applied brake load of the normally engaged brake decreases as the input duty cycle percentage increases.

12. The proportional brake system according to claim 8 , wherein:

at least one of the variable displacement brakes comprises a normally engaged brake and the input command comprises an input current, and

an applied brake load of the normally engaged brake decreases as the input current increases.

13. The proportional brake system according to claim 8 , wherein:

at least one of the variable displacement brakes comprises a normally disengaged brake and the input command comprises a duty cycle percentage, and

an applied brake load of the normally disengaged brake decreases as the input duty cycle percentage decreases.

14. The proportional brake system according to claim 8 , further comprising sensors configured to sense the movements of the movable surfaces relative to the wings and to generate the data accordingly.

15. A method of operating a proportional braking system, the method comprising:

receiving a command for moving movable surfaces relative to a housing of the movable surfaces;

releasing variable displacement brakes disposed to prevent movements of the movable surfaces;

moving the movable surfaces relative to the housing in accordance with the command;

determining a difference between actual and target movements of the movable surfaces relative to the housing; and

generating, based on the difference, a proportional braking command to be issued to the variable displacement brakes for proportionally displacing the variable displacement brakes toward and away from braking engagement with the movable surfaces,

wherein:

each variable displacement brake comprises brake and thrust plates, an elastic element that causes the thrust plates to be urged toward braking engagements with the brake plates, a coil at a first side of the brake plates and a booster coil at a second side of the brake plates, and

the proportional braking command causes either the coil or the booster coil to become energized thereby generating a flux moment in opposition to or in support of the urging of the elastic element, respectively.

16. The method according to claim 15 , wherein:

at least one of the variable displacement brakes comprises a normally engaged brake and the proportional braking command comprises a duty cycle percentage, and

an applied brake load of the normally engaged brake decreases as the input duty cycle percentage increases.

17. The proportional brake system according to claim 15 , wherein:

at least one of the variable displacement brakes comprises a normally engaged brake and the proportional braking command comprises an input current, and

an applied brake load of the normally engaged brake decreases as the input current increases.

18. The proportional brake system according to claim 15 , wherein:

at least one of the variable displacement brakes comprises a normally disengaged brake and the proportional braking command comprises a duty cycle percentage, and

an applied brake load of the normally disengaged brake decreases as the input duty cycle percentage decreases.