Prismatic/revolute orienting apparatus
A two degree-of-freedom parallel device for orienting or pointing an end effector with vibration suppression is described. The two end effector degrees-of-freedom are decoupled by connecting fast actuators to the effector by passive joints. The stiffness of the linkages and the high speed of the revolute and prismatic actuators employed permit the application of large feedback useful for disturbance rejection.
1. An apparatus for orienting an end effector, comprising in combination:
a first rod;
a prismatic actuator effective for linearly translating said first rod;
a second rod;
a universal joint rigidly attached at one end to said first rod and at a second end to said second rod;
a third rod rigidly attached to said end effector;
a spherical joint rigidly attached at one end to said second rod and rigidly attached at a second end to the end of said third rod opposite to the end thereof attached to said end effector;
a revolute joint to which said end effector is rotatably fastened, thereby defining a first axis of rotation for said end effector, wherein said first prismatic actuator, said universal joint, said spherical joint, said first rod, said second rod, and said third rod cooperate to rotate said end effector about the first axis of rotation; and
a revolute actuator having a spindle coaxial with said first rod and rigidly connected to said revolute joint, effective for rotating said revolute joint about a second axis of rotation perpendicular to and decoupled from the first axis of rotation.
2. The apparatus of claim 1 , wherein said revolute joint comprises a U-joint having a base, the base being rigidly connected to the second end of said spindle.
3. The apparatus of claim 1 , further comprising a first controller for directing said prismatic actuator to provide linear motion to said first rod, and a second controller for directing said revolute actuator to rotate said revolute joint.
4. The apparatus of claim 1 , further including a base member to which said prismatic actuator and said revolute actuator are attached.