Bearing Assembly Having a Flex Pivot to Limit Gimbal Bearing Friction for Use in a Gimbal Servo System
A bearing assembly suitable for use in a gimbal servo system is provided. The bearing assembly comprises a housing, a first shaft, a bearing rotatingly coupling the first shaft to the housing such that the first shaft is adapted to rotate about an axis relative to the housing, a second shaft having a first end adapted to be coupled to a payload, and a flex pivot element pivotally coupling an end of the first shaft to a second end of the second shaft such that the second shaft is adapted to rotate relative to the first shaft via the flex pivot element. In response to a rotation of the second shaft, the flex pivot element is adapted to pivot an angle about the first shaft axis. The pivot angle reflects a displacement of the second shaft relative to the first shaft and corresponds to a friction disturbance of the bearing.
1 . A bearing assembly suitable for use in a gimbal servo system, comprising:
a housing;
a first shaft having an end and an axis;
a bearing rotatingly coupling the first shaft to the housing such that the first shaft is adapted to rotate about the axis relative to the housing;
a second shaft having a first end and a second end, the first end being adapted to be coupled to a payload; and
a flex pivot element pivotally coupling the end of the first shaft to the second end of the second shaft such that the second shaft is adapted to rotate relative to the first shaft via the flex pivot element;
wherein, in response to a rotation of the second shaft, the flex pivot element is adapted to pivot an angle about the first shaft axis, the pivot angle reflecting a displacement of the second shaft relative to the first shaft.
2 . A bearing assembly as set forth in claim 1 , wherein the second shaft is in coaxial alignment with the first shaft.
3 . A bearing assembly as set forth in claim 1 , wherein the pivot angle corresponds to a friction disturbance imparted by the bearing on the first shaft due to the rotation of the second shaft relative to the housing.
4 . A bearing assembly as set forth in claim 1 , further comprising a first motor operatively configured to rotate the second shaft relative to the housing.
5 . A bearing assembly as set forth in claim 4 , further comprising a position transducer disposed in proximity to the flex pivot element, the position transducer being adapted to sense the pivot angle and output a corresponding displacement signal, wherein the first motor is operatively coupled to the displacement signal and adapted to torque the second shaft in accordance with the displacement signal.
6 . A bearing assembly as set forth in claim 4 , further comprising:
a position transducer disposed in proximity to the flex pivot element, the position transducer being adapted to sense the pivot angle and output a corresponding displacement signal; and
a servo controller operatively coupled to the displacement signal and operatively configured to output a torque compensation signal based on the rotation of the second shaft offset by a torque reflected by the displacement signal,
wherein the first motor is operatively coupled to the torque compensation signal and adapted to rotate the second shaft relative to the housing in accordance with the torque compensate signal.
7 . A bearing assembly as set forth in claim 6 , further comprising a rate sensor adapted to sense an angular velocity of the payload about the axis of the first shaft gimballed axis of the platform and output a corresponding angular velocity signal, wherein the servo controller is operatively coupled to the angular velocity signal and outputs the torque compensation signal based on the angular velocity signal offset by the torque reflected by the displacement signal.
8 . A bearing assembly as set forth in claim 6 , further comprising a bearing motor operatively coupled to the displacement signal and operatively configured to rotate the first shaft relative to the housing to compensate for the torque reflected by the displacement signal.
9 . A bearing assembly as set forth in claim 1 , wherein the bearing includes an inner race member attached to the first shaft, an outer race member attached to the housing, and one of a ball bearing or a roller bearing disposed between the inner race member and the outer race member.
10 . A bearing assembly suitable for use in a gimbal servo system, comprising:
a housing;
a first shaft having an end and an axis;
a bearing rotatingly coupling to the first shaft to the housing such that the first shaft is adapted to rotate about the axis relative to the housing;
a second shaft having a first end and a second end, the first end being adapted to be coupled to a payload;
a flex pivot element pivotally coupling the end of the first shaft to the second end of the second shaft such that the second shaft is adapted to rotate relative to the first shaft via the flex pivot element; and
wherein, in response to a rotation of the second shaft, the flex pivot element is adapted to pivot an angle about the first shaft axis, the pivot angle reflecting a displacement of the second shaft relative to the first shaft and corresponding to a friction disturbance imparted by the bearing on the first shaft due to the rotation of the second shaft relative to the housing.
11 . A bearing assembly as set forth in claim 10 , wherein the second shaft is in coaxial alignment with the first shaft.
12 . A bearing assembly as set forth in claim 10 , further comprising a first motor operatively configured to rotate the second shaft relative to the housing.
13 . A bearing assembly as set forth in claim 12 , further comprising a position transducer disposed in proximity to the flex pivot element, the position transducer being adapted to sense the pivot angle and output a corresponding displacement signal, wherein the first motor is operatively coupled to the displacement signal and adapted to torque the second shaft in accordance with the displacement signal to counter the friction disturbance of the bearing.
14 . A bearing assembly as set forth in claim 13 , further comprising a bearing motor operatively coupled to the displacement signal and operatively configured to rotate the first shaft relative to the housing to compensate for the torque reflected by the displacement signal.
15 . A bearing assembly as set forth in claim 12 , further comprising:
a position transducer disposed in proximity to the flex pivot element, the position transducer being adapted to sense the pivot angle and output a corresponding displacement signal; and
a servo controller operatively coupled to the displacement signal and operatively configured to output a torque compensation signal based on the rotation of the second shaft offset by a torque reflected by the displacement signal,
wherein the first motor is operatively coupled to the torque compensation signal and adapted to rotate the second shaft relative to the housing in accordance with the torque compensate signal.
16 . A bearing assembly as set forth in claim 15 , further comprising a rate sensor adapted to sense an angular velocity of the payload about the axis of the first shaft gimballed axis of the platform and output a corresponding angular velocity signal, wherein the servo controller is operatively coupled to the angular velocity signal and outputs the torque compensation signal based on the angular velocity signal offset by the torque reflected by the displacement signal.
17 . A bearing assembly as set forth in claim 15 , wherein the servo controller has a lead-lag compensator operatively configured to output a bearing compensation signal based on the displacement signal, the bearing assembly further comprising a bearing motor operatively coupled to the bearing compensation signal and adapted to rotate the first shaft relative to the housing to compensate for the torque reflected by the bearing compensation signal.