ADCS Sun Sensor and Star Tracker Miniaturization
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Solution Overview
Problem
Conventional space vehicle attitude determination and control systems (ADCS) face challenges in miniaturization, high power consumption, and cost, particularly for small space vehicles like cubesats, due to large and expensive sun sensors and star trackers, as well as design issues with reaction wheels that are prone to failure under stress and misalignment.
Innovation Solution
The proposed ADCS system incorporates 2D photodiode sun sensors with pinhole cameras for accurate sun position determination, a miniature intelligent star tracker for improved pointing accuracy, and a robust reaction wheel assembly using pliable rivets to reduce mechanical stress and misalignment, enabling efficient attitude control in small space vehicles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional sun sensors are used in ADCS systems, then sun position detection function is provided, but the sensor consumes excessive volume and cost for small space vehicles
Solution Approach 1:
The sun sensor is segmented into multiple functional layers: pinhole aperture layer, light-tight housing, and 2D photodiode array layer. This segmentation allows each component to be optimized independently, achieving compact form factor while maintaining detection precision through the coordinated function of the pinhole geometry and photodiode array.
Solution Approach 2:
The patent replaces conventional mechanical sun sensor mechanisms with a pinhole camera optical system combined with 2D photodiode detection. This substitution eliminates complex mechanical moving parts and reduces volume while maintaining measurement capability through optical projection and electronic detection.
2Use of energy by stationary object
If conventional star trackers are used in ADCS systems, then attitude determination function is provided, but the tracker has high power consumption and large volume
Solution Approach 1:
The star tracker is merged with the sun sensor platform, sharing common structural support, power supply, and data processing resources. This integration reduces overall power consumption and volume while maintaining attitude determination accuracy through coordinated observation of stellar and solar positions.
Solution Approach 2:
The ADCS sensor platform is designed with multi-functionality, serving both as a sun sensor for solar position detection and as a star tracker for stellar navigation. This universal design eliminates the need for separate dedicated star tracker hardware, reducing power consumption and volume while maintaining both detection functions.
3Volume of moving object
If reaction wheels are mounted directly to motor drive shaft, then compact design is achieved, but high stresses during vibration testing cause damage or destruction
Solution Approach 1:
A flexible coupling intermediary is introduced between the motor drive shaft and the reaction wheel mounting flange. This intermediary component absorbs and isolates vibration stresses, preventing direct transmission of high-frequency loads to the wheel assembly while maintaining mechanical connectivity and compact overall dimensions.
Solution Approach 2:
The patent employs flexible coupling elements with compliant geometry that can deform elastically under vibration stress. These flexible components act as shock-absorbing intermediaries, protecting the rigid reaction wheel assembly from damaging stresses while maintaining the compact integrated design.
4Weight of moving object
If high rotation rates are used for reaction wheels, then sufficient moment of inertia is achieved, but high precision in fabrication and assembly is required to prevent rapid failure
Solution Approach 1:
The flexible coupling intermediary is installed beforehand to cushion and absorb imbalances and misalignments in the reaction wheel assembly. This pre-installed protective element compensates for manufacturing tolerances and assembly variations, allowing the wheel to operate at high rotation rates without rapid failure from imbalances.
Solution Approach 2:
The patent changes the mechanical coupling parameters from rigid to flexible, allowing the system to tolerate higher rotation rates with relaxed precision requirements. The flexible coupling modifies the dynamic parameters of the assembly, reducing the sensitivity to manufacturing and assembly tolerances while maintaining sufficient moment of inertia.
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 solution provides a compact, low-cost, and accurate attitude determination and control system suitable for small space vehicles, reducing power consumption and mechanical stress, while enhancing pointing accuracy and reliability through the use of 2D photodiode sun sensors, miniature star trackers, and a robust reaction wheel design.
Implementation Method 1
a sensor including a two-dimensional (2D) photodiode configured to receive light from the pinhole aperture
Implementation Method 2
The ADCS module includes a wheel assembly and a motor assembly that are connected to one another via pliable rivets
Data Source
AI summary
An ADCS module may be configured to use coordinate data from 2D photodiodes in one or more sun sensors to determine a sun vector. The ADCS module may then use the sun vector in reference to its own body faced (BF) coordinate system to calculate a change in the orientation of the space vehicle. The change in orientation mechanism may be accomplished by reaction wheels, ion thrusters, or other orientation altering mechanisms. A miniature, intelligent star tracker may be included that improves satellite attitude determination and pointing accuracy. An improved reaction wheel assembly may be included that is more robust and suitable for inclusion in small space vehicles.