Solar Array Current Voltage Measurement Switching Telemetry
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Solution Overview
Problem
Current systems for measuring current and voltage in spacecraft solar arrays are inadequate, as they often only measure total current or open circuit voltage, failing to provide the necessary data points to generate a current-voltage curve, and are unable to collect data quickly enough to avoid temperature-related inaccuracies.
Innovation Solution
A method and apparatus utilizing a set of switches, a measurement unit, and a telemetry subsystem to connect current sources to a power bus or measurement unit, allowing for the generation of current and voltage measurements while minimizing temperature changes, with data transmission to a remote location for analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large number of voltage and current data points are collected to create a high fidelity I-V curve, then measurement precision is improved, but the time required for data collection increases, causing temperature changes that affect measurement accuracy
Solution Approach 1:
The patent segments the solar array into multiple independently controllable strings, allowing selective measurement of individual strings rather than requiring simultaneous measurement of the entire array. This segmentation enables faster data collection from individual strings while maintaining the ability to construct comprehensive I-V curves through multiple rapid measurements.
Solution Approach 2:
The patent implements periodic switching between different measurement modes (individual string measurements, combined array measurements) to collect data in rapid succession. This periodic action allows the system to gather multiple data points quickly by alternating between measuring different subsets of the solar array, minimizing temperature drift effects.
2Productivity
If all solar strings are measured simultaneously to reduce temperature effects, then measurement speed is improved, but the complexity of the measurement system increases
Solution Approach 1:
The patent designs a universal measurement apparatus that can measure multiple solar strings through a single integrated system. The measurement device serves multiple functions by sequentially or simultaneously measuring different strings and combining the data, eliminating the need for separate measurement systems for each string while maintaining measurement speed.
Solution Approach 2:
The patent introduces a central control and switching mechanism that acts as an intermediary between the solar strings and the measurement device. This intermediary manages the complex routing and switching of multiple strings to the measurement apparatus, simplifying the overall system architecture while enabling simultaneous or rapid sequential measurements of multiple strings.
3Ease of operation
If voltage and current measurements are taken under varying temperature conditions, then ease of operation is improved, but measurement precision deteriorates due to temperature effects on solar cell characteristics
Solution Approach 1:
The patent incorporates temperature sensing and feedback mechanisms that monitor the thermal state of the solar array during measurements. This feedback allows the system to adjust measurement timing, select optimal measurement windows, or apply correction factors to compensate for temperature effects, maintaining measurement precision while allowing operations under varying environmental conditions.
Solution Approach 2:
The patent performs preliminary temperature assessments and selects measurement timing based on predicted thermal stability. By conducting measurements during pre-identified stable temperature periods or applying preliminary temperature-based corrections, the system maintains precision without requiring strict environmental control, thus preserving ease of operation.
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
Enables accurate and efficient collection of current and voltage data, reducing the need for onboard processing and storage, thereby minimizing spacecraft weight and complexity while maintaining data accuracy.
Implementation Method 1
A solar array consists of single or multiple solar panels which have a surface area that can be controlled to point towards the sun as a mechanism moves. More exposed surface area means that more electricity may be converted from light energy.
Data Source
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AI summary
An apparatus comprises switches, a measurement unit, and a telemetry subsystem. The switches connect the current sources to a power bus when in a first position and to the measurement unit when the switches are in a second position. The measurement unit generates a ramp signal to control the solar strings from an open circuit state to a short circuit state linearly in a short duration and provides continuous current and voltage telemetry data at the output while the set of switches is in the second position. The telemetry subsystem is pre-set to a dwell mode and samples a large amount of voltage and current telemetry data. The telemetry subsystem transmits this data to ground directly to eliminate the need for processing and storage resources in the spacecraft. The telemetry data is used to plot I-V curve for health monitoring.