Braking assembly for applying a controllable braking force to a rotatable joint
Rotatable joints may include one or more braking assemblies. The one or more braking assemblies may control a degree of movement of the rotatable joint to provide a range of damping. In some instances, the braking assemblies may include brake band(s) that tighten and loosen around a hub, or other rotatable member of the rotatable joint. The amount of braking, or tautness of the brake band(s), may be variably controlled to arrest the hub by different amounts. In some instances, the tightening of the brake band(s) around the hub may be controlled using linear actuator(s) and/or magnetic element(s). Implementing braking assemblies having controlled actuation may improve control of rotatable joints without adding cost, complexity, weight, or bulk.
1. A brake mechanism for applying a selective braking force to a rotatable joint, comprising:
a first brake including:
a first brake band having a first fixed end and a first free end, the first brake band being configured to apply a first braking torque to at least a first portion of a hub of the rotatable joint in a clockwise direction, the first fixed end and the first free end being disposed on a first plane,
a first linear actuator configured to supply a first force to tighten the first brake band around the hub in the clockwise direction, and
a first lever arm having:
a first arm coupled to the first free end, and
a second arm coupled to the first linear actuator;
a second brake including:
a second brake band having a second fixed end and a second free end, the second brake band being configured to apply a second braking torque to at least a second portion of the hub of the rotatable joint in a counter-clockwise direction, the second fixed end and the second free end being disposed on a second plane spaced apart from the first plane,
a second linear actuator configured to supply a second force to tighten the second brake band around the hub in the counter-clockwise direction, and
a second lever arm having:
a third arm coupled to the second free end, and
a fourth arm coupled to the second linear actuator;
and
a controller for selectively controlling the first linear actuator and the second linear actuator to apply a desired braking force to the hub.
2. The brake mechanism of claim 1 , further comprising a pin, wherein:
the first lever arm rotates about the pin during actuation of the first linear actuator; and
the second lever arm rotates about the pin during actuation of the second linear actuator.
3. The brake mechanism of claim 1 , wherein:
actuation of the first linear actuator in a first direction causes the first free end to move in a second direction to apply the first braking torque;
actuation of the first linear actuator in a third direction causes the second free end to move in a fourth direction to apply the second braking torque;
the second direction is opposite the first direction; and
the fourth direction is opposite the third direction.
4. The brake mechanism of claim 1 , wherein:
the first arm includes a first length that is less than a second length of the second arm; and
the third arm includes a third length that is less than a fourth length of the fourth arm.
5. A device comprising:
a housing including:
a first end,
a second end opposite the first end,
a first side,
a second side opposite the first side,
a top, and
a bottom opposite the top;
a rotatable member located closer to the first end than the second end;
a first braking assembly disposed within the housing, the first braking assembly including:
a first brake band wrapped around the rotatable member, the first brake band having a first fixed end and a first free end; and
a first actuator for controllably tightening the first free end around the rotatable member, the first free end being located closer to the first side than the second side, wherein actuating the first actuator in a first direction causes the first brake band to tighten around the rotatable member and actuating the first actuator in a second direction that is different than the first direction causes the first brake band to loosen around the rotatable member; and
a second braking assembly disposed within the housing, closer to the bottom than the first braking assembly, the second braking assembly including:
a second brake band wrapped around the rotatable member, the second brake band having a second fixed end and a second free end; and
a second actuator for controllably tightening the second free end around the rotatable member, the second free end being located closer to the second side than the first side, wherein actuating the second actuator in the first direction causes the second brake band to tighten around the rotatable member and actuating the second actuator in the second direction causes the second brake band to loosen around the rotatable member.
6. The device of claim 5 , further comprising a first support coupled to the housing and a second support coupled to the housing, wherein:
the first fixed end couples to the first support; and
the second fixed end couples to the second support.
7. The device of claim 5 , wherein:
the first free end couples to the first actuator through a first lever arm having a first arm and a second arm that pivot around a first pivot point; and
the second free end couples to the second actuator through a second lever arm having a third arm and a fourth arm that pivot around a second pivot point.
8. The device of claim 7 , wherein the first actuator and the second actuator comprise at least one of a linear actuator, eccentric cam, cable, or a motor.
9. The device of claim 8 , wherein:
the first free end couples to the first arm;
the first actuator couples to the second arm;
the second free end couples to the third arm; and
the second actuator couples to the fourth arm.
10. The device of claim 5 , further comprising a controller configured to independently controllably tighten the first brake band and the second brake band.
11. The device of claim 5 , wherein:
the first free end couples to a first lever arm;
the second free end couples to a second lever arm;
the first lever arm includes first arms having first magnets that interact with second magnets of a third lever arm to tighten or loosen the first brake band around the rotatable member; and
the second lever arm includes second arms having third magnets that interact with fourth magnets of a fourth lever arm to tighten or loosed the second brake band around the rotatable member.
12. The device of claim 11 , wherein:
the first arms are of unequal length; and
the second arms are of unequal length.
13. The device of claim 5 , wherein:
the first brake band at least partially wraps around the rotatable member in a counter-clockwise direction; and
the second brake band at least partially wraps around the rotatable member in a clockwise direction.
14. The device of claim 5 , wherein the first braking assembly is disposed vertically above the second braking assembly within the housing.
15. The device of claim 5 , further comprising an arm coupled to the rotatable member, and disposed adjacent to the top of the housing.
16. A mechanical joint comprising:
a first brake band including:
a first length that surrounds at least a first portion of a hub, and
a first free end;
a first actuator configured to actuate in a first direction to displace a first magnetic element to apply a first force to the first free end in a second direction, the second direction being opposite the first direction;
a second brake band including:
a second length that surrounds at least a second portion of the hub, and
a second free end; and
a second actuator configured to actuate in a third direction to displace a second magnetic element to apply a second force to the second free end in a fourth direction, the fourth direction being opposite the third direction.
17. The mechanical joint of claim 16 , further comprising:
a first lever arm including:
a first arm coupled to the first free end, and
a second arm having the first magnetic element;
a second lever arm including:
a third arm coupled to the second free end, and
a fourth arm having the second magnetic element;
a third lever arm including:
a fifth arm coupled to the first actuator, and
a third magnetic element that opposes the first magnetic element; and
a fourth lever arm including:
a sixth arm coupled to the second actuator, and
a fourth magnetic element that opposes the second magnetic element.
18. The mechanical joint of claim 16 , wherein at least one of the first actuator or the second actuator is non-backdrivable.
19. The mechanical joint of claim 16 , further comprising a first lever arm including a first arm coupled to the first free end, and a second lever arm including a second arm coupled to the second free end, wherein:
the first force is applied in a first direction;
the second force is applied in a second direction;
a plane is defined through a center of the hub, a first center of rotation of the first lever arm, and a second center of rotation of the second lever arm;
the first direction is in line with the plane; and
the second direction is in line with the plane.
20. The mechanical joint of claim 16 , further comprising a controller for selectively controlling the first actuator and the second actuator to apply a desired braking force to the hub.