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Moving forward for ECOSat, the use of simulations and a better focus on standardised documents will save both money and a lot of time by reducing the amount of work that tends to be re-done as well as reduce the amount of work that is done into hardware and processes that could have been caught as problems during simulation. The classic design process we have followed up untill now is the Design-Build-Test-Fix process, this is however just no good for a team that has members change once every 3.5 months, with the lack of documentation we have found ourselves stuck in the build-half test-fix loop. Moving forward to finalize the systems and actually become ready for launch we need to take a more professional approach to the design of the satellite.

Moving forward the idea is to develop a simulation framework in Matlab Simulink that simulates the attitude and orbit of the satellite and can provide environmental data for both software-in-loop and hardware-in-loop testing. The simulation will allow us to test algorithms used for communications, scheduling, and for the ADCS system and determine if they work before spending money on hardware, in addition with the embedded coder tool box some of these algorithms can be ported to our microcontrollers directly from the matlab environment for us (This is what NASA has done for the new Orion Spacecraft). The framework should allow us to:

  • Feed Solar Panel generation values from the simulated sSun angle to a solar cell simulator interface circuit to test charging, discharging, and reaction procedures to over and undercharge conditions for the power system
  • Feed Satellite position and velocity with respect to Uvic for communication system testing with simulated doppler shift, noise, and power
  • Feed simulated magnetic field data, gps data, gyroscopic, and accelerometer data to the ADCS system and read back magnetorquer settings to simulated and evaluated the ADCS system under different conditions in orbit.
  • Read and write to the CAN bus and other shared serial interfaces for Command and Data handling testing
  • General full stack testing over multiple simulated orbits.

To allow for this two new Electrical systems will be needed, first the solar cell simulator interface circuit will need to simulate the IV curve of our solar cells and be tunable to control the curves parameters to follow simulated Sun angle, this will require research into solar cell simulator circuits and how they are parametrized, selection of components, circuit simulation, schematic capture, and board layout (a nice start to finish project there). The second system needed is an interface for a test computer to read from and write to the bus connector (primarily the CAN bus).

Using this I want us to move from the design-build-test-fix process to one of Requirements → Simulate Environment → Algorithm design → Software In Loop test → fix Algorithms → Hardware and hardware interface design → Hardware in loop test → fix, in where:

  • Requirements: the system requirements are documented in the datasheet template, what are its required sensors, outputs, data processing (control loops or other critical tasks/functionality) etc
  • Simulate Environment: Simulate inputs of the system as it will operate in orbit or more generically in its intended environment. Any changes to the physical state of the system due to outputs of the system need to be included, for example the torque on the satellite due to a mangetorquer being turned on in the current simulated magnetic field.
  • Algorithm design: Control loops, digital signal processing, critical procedures and responses should be done in c or Matlab code to verify that they work as expected using the simulated sensor and output modelling.
  • Software-in-loop testing: All critical software algorthms, etc should be tested for normal operating environment, edge cases, and for long duration simulations (one year is our hopeful mission life)
  • fix Algorithms: Any issues found during software-in-loop testing should be fixed until we our confident that it is working or that a bigger change in design is needed
  • Hardware and hardware interface design: the hardware of the system as well as any interfaces needed to link the simulation with the hardware should be designed to meet the requirements and algorithm.
  • Hardware-in-loop testing: the same tests (with of course the exception of the full year simulation) should be run and pass on hardware as they did in software in loop testing
  • fix: firmware and hardware should be revised until tests are passed.

Orbital Simulation

Sensor Simulation for SIL

Test Interfacing for HIL

Bus Interface

The bus interface is being developed by Cass and Keith this term (May 2015)

basic features of the interface are

  1. provide control from a test computer of USB to
    1. The CAN bus
    2. 16 GPIO pins
    3. 1 UART
    4. 1 I2C
    5. 1 SPI
  2. generate the 5V5, 5V3 and 3V5 voltage rails within the 120pin bus connector

Unpopulated/Undeveloped features include

  1. control over the bus voltage rails
  2. current monitoring of the bus voltage rails

Solar Cell Simulation

The solar cell simulator has been taken on as an ELEC 499 project by Victor and Raymond, anyone interested in helping them should contact them during a meeting (MAY 2015).

The basic solar cell simulator requirements are:

  1. Mimic the current-voltage curve vs irradiance characteristics of seven solar cell arrays simultaneously
    1. Array Configuration of 2s6p + 1
  2. Provide a USB or UART interface for setting the irradiance of each simulated cell
  3. Address EMI considerations
    1. ferrite chokes on outputs of switching supplies
    2. decoupling capacitors on digital logic
    3. voltage clamps on outputs of solar simulators to protect the satellite systems from voltage spikes in the simulator

Optional features

  1. Provide expandability past 7 arrays
  2. Allow for control of other parameters not just irradiance
    1. parameters such as open circuit voltage would allow for testing with simulated radiation degredation

USRP configuration

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