P15310: SATCOM on the Move
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Sub Systems Design

Table of Contents

For this phase of MSD I, we're continuing to redefine and develop our solution for Spectracom. As per customer instruction, we have prepared two options for the camera mounting system - one that can simply be purchased and easily interfaced with; the other a custom-built mount with customized motors, gears, and mounts.

ServoCity PT785-S

Analysis

Benchmarking

While these systems may or may not work for our project, they do give some perspective on the capabilities of the parts that are out there and their prices.

It is important to note that these complete systems are for industrial and military satellite communication. This is NOT the goal of this project. We will likely be well off from their milspec standards. The scale of out project is to show something on camera, not make a connection with a satellite in orbit.

Option Comparison

This budget was used to estimate our two mount options. The custom made system required that the camera mount be built from scratch and have extremely precise motors. The second option was a pre-built system that was less precise, but cheaper. Spectracom agreed that this system would be sufficient to demonstrate the Geo-PNT capabilities. In addition, it would take lead time from the mechanical engineering and save it for the software engineering, testing, and video.

Modelling/General Schematics

The general outline of our system, showing power and data connections is as follows:
General Schematic

General Schematic

The component layout, inside the enclosure will have this general outline:
System Enclosure Layout

System Enclosure Layout

The Program

This is a high level drawing of the program flow. This system should run completely from the microprocessor development board.

Input

The program will receive data from one of two source. The Geo-PNT will be sending data via Ethernet on a normal run, but we will likely be using the option of reading from a file to start. We can simulate Geo-PNT data packets for testing purposes without the complexity of a full system with GPS.

Data Processing

This is the heart of the program. The program starts by parsing the data into usable formats/units. Mainly, the current coordinates, attitudes, and signal strength must be monitored and processed for the next step.

The next step would be to calculate the pointing direction. The calculations involved are summarized in the Pointing Calculations document. These calculations are short and simple, giving the program plenty of headroom should there be any need for additions. This need may arise if smoother transitions are needed and the video looks like it stutters. A simple integral algorithm should be sufficient, though a full PID algorithm is also an option.

The final step would be to convert the data to an instruction for the mount. Due to the nature of the mount, only a select number of options is available, so a simple look up table will likely be used.

Output

The program's final step will be to send the correct control instructions down to the motor controller. This process is repeated at every full data packet.
Program Flow Chart

Program Flow Chart


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