Control Moment Gyroscope Stator Assembly Torque Path
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Solution Overview
Problem
Conventional control moment gyroscopes (CMGs) have a lengthy and inefficient rotor-to-spacecraft load path due to a thin-walled and flexible inner gimbal assembly housing, which results in poor torque transmission and heat conduction, and suffer from undesirable twisting and bending during operation.
Innovation Solution
A CMG design featuring a stator assembly with a large bore gimbal bearing positioned close to the spin axis and adjacent to the spacecraft interface, reducing the length of the rotor-to-spacecraft load path and incorporating a torque module assembly proximate to the signal module assembly to minimize bending forces, while maintaining a compact and lightweight structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the IGA housing is made thin-walled and flexible, then the CMG structure is lightweight and compact, but the torque transmission and heat conduction efficiency deteriorates
Solution Approach 1:
The CMG is divided into two separate housing structures: the IGA housing that supports the rotor and spin motor, and the stator assembly housing that supports the TMA and SMA. This segmentation allows each housing to be optimized independently - the IGA housing can remain thin-walled and lightweight while the stator assembly housing provides the stiff torque transmission path directly to the spacecraft interface.
Solution Approach 2:
The stator assembly housing acts as an intermediary structure between the TMA and the spacecraft interface. It provides a direct, stiff load path for torque transmission from the TMA to the spacecraft, bypassing the need for the IGA housing to be structurally stiff. The gimbal bearing serves as the intermediary that connects the rotating IGA to the stationary stator assembly housing.
2Strength
If the IGA housing is stiffened by thickening walls or adding ribs, then torque transmission improves, but the CMG weight increases
Solution Approach 1:
The torque transmission function is extracted from the IGA housing and transferred to the stator assembly housing. The IGA housing is freed from the requirement to be structurally stiff for torque transmission, allowing it to remain thin-walled and lightweight. The stiff torque transmission path is taken out and implemented as a separate structural element (the stator assembly housing) that directly connects to the spacecraft interface.
3Stability of the object's composition
If the TMA and SMA are mounted to opposite ends of the IGA housing, then the CMG structure is balanced, but twisting of the IGA housing occurs during gimbaling
Solution Approach 1:
The TMA and SMA are merged into a single structural assembly (the stator assembly) that is mounted to the stator assembly housing. This combining of the torque and signal module assemblies into a unified structure mounted to a common housing eliminates the twisting problem that would occur if they were mounted to opposite ends of the IGA housing, while maintaining structural balance through the rigid stator assembly housing.
4Device complexity
If the rotor-to-spacecraft load path is made lengthy and passes through the IGA housing, then the CMG structure is simple, but the thermal conduction efficiency deteriorates
Solution Approach 1:
The stator assembly housing is designed with local structural features (such as thick walls and direct mounting to the spacecraft interface) that provide high thermal conduction efficiency specifically along the torque transmission path. This localized optimization of thermal properties allows efficient heat conduction from the TMA to the spacecraft without requiring the entire CMG structure to be complex or heavy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design provides a short and stiff torque transmission path and efficient thermal conduction, reducing bending forces and enhancing mission capability by improving torque and heat dissipation to the spacecraft, while maintaining a compact and scalable structure.
Implementation Method 1
gimbal bearings are disposed between the IGA and the CMG housing
Implementation Method 2
A gimbal bearing is disposed between the IGA housing and the stator assembly housing
Implementation Method 3
a spin motor. The IGA, in turn, may be rotated about a gimbal axis by a torque module assembly (TMA)
Implementation Method 4
The spinning rotor is of sufficient mass and is spinning at such a rate that movement of the rotor out of its plane of rotation induces a significant torque
Implementation Method 5
Control moment gyroscopes (CMGs) are commonly employed in satellite attitude control systems
Implementation Method 6
The spinning rotor is of sufficient mass and is spinning at such a rate that movement of the rotor out of its plane of rotation induces a significant torque about an output axis that is normal to the spin and gimbal axes
Implementation Method 7
Spin bearings are disposed around the shaft ends to facilitate the rotational movement of the shaft
Implementation Method 8
Spin bearings are disposed around the shaft ends
Implementation Method 9
This torque is transmitted from the CMG rotor to the spacecraft along a rotor-to-spacecraft load path
Implementation Method 10
heat generated at the spin bearings as the result of friction may also be conducted to the spacecraft along the rotor-to-spacecraft load path
Data Source
Figure 1
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Figure 3
AI summary
A control moment gyroscope (CMG) (60) comprises an inner gimbal assembly (IGA) (64) including an IGA housing (72), a rotor (76) rotatably coupled to the IGA housing, and a spin motor (86) coupled to the IGA housing and configured to rotate the rotor about a spin axis (88). The CMG further comprises a stator assembly (62), which includes: (i) a stator assembly housing (96) rotatably coupled to the IGA housing, and (ii) a torque module assembly (98) coupled to the stator assembly housing and configured to rotate the IGA about a gimbal axis (102). A gimbal bearing (68) is disposed between the IGA housing and the stator assembly housing. The gimbal bearing resides between the spin axis and the torque module assembly such that the distance between the gimbal bearing and the spin axis is less than the distance between the gimbal bearing and the torque module assembly.