Request for Approval

Description

The request for approval (RFA) is the very first step in successfully completing a senior design project. Before submitting your RFA, you must post your project idea to the Web Board using the "Idea" post type. Once your idea has been fleshed out through the Web Board, you can move on request for approval through PACE under the My Project page. Once submitted, your project will be cloned to the Web Board as "Project Request" post. You can edit the project on the My Project page, add your teammates and see comments from the instructors. The course staff may provide feedback on your idea (which will appear at the bottom of your project's page), or suggest changes in the scope of the project and ask you to re-submit an RFA. Based on your incorporation of feedback your project will be approved or rejected. If it is rejected, the My Project page will revert back to it's original format and your project will disappear.

Once the course staff has approved the project idea, you will receive instructions on how to submit your project through PACE, at which time you will be assigned a project number in the Projects list, a TA, and a locker in the lab. Once your project is approved, please go to the Projects page, log into the PACE system, and make sure all of the information is correct.

Video Lecture

Video, Slides

Requirements and Grading

The RFA is graded credit/no credit based on whether your project is approved before the deadline. Note that submitting an RFA before the deadline does not guarantee approval before the deadline. The RFA is submitted through PACE under the My Project page, and should be Markdown-formatted with the following information:

# Title

Team Members:
- Student 1 (netid)
- Student 2 (netid)
- Student 3 (netid)

# Problem

Describe the problem you want to solve and motivate the need.

# Solution

Describe your design at a high-level, how it solves the problem, and introduce the subsystems of your project.

# Solution Components

## Subsystem 1

Explain what the subsystem does.  Explicitly list what sensors/components you will use in this subsystem.  Include part numbers.

## Subsystem 2

## ...

# Criterion For Success

Describe high-level goals that your project needs to achieve to be effective.  These goals need to be clearly testable and not subjective.

Projects must be legal and ethical. They must have significant scope and complexity commensurate with the size of the team. This is, of course, a subjective assessment of the course staff. To gain some insight into this judgment, please browse projects from previous semesters. The project must involve the design of a significant hardware component at the circuit level. In exceptional cases, projects not meeting this criteria may be acceptable when augmented by a Special Circuit assignment (however this is typically a last resort).

Beyond these basic requirements, you have total discretion in proposing a project. This is a great opportunity for you to pursue your own interests. Since you choose your own projects, we expect a high level of enthusiasm from you and your team.

Submission and Deadlines

The RFA submission deadline may be found on the Course Calendar. Typically, approval of the RFA is due during the afternoon of the third Thursday of the semester.

Quick Tips and Helpful Hints

Posting: Choosing a project: Choosing partners: Some general project ideas that are fraught with pitfalls:

ATTITUDE DETERMINATION AND CONTROL MODULE FOR UIUC NANOSATELLITES

Shamith Achanta, Rick Eason, Srikar Nalamalapu

Featured Project

Team Members:

- Rick Eason (reason2)

- Srikar Nalamalapu (svn3)

- Shamith Achanta (shamith2)

# Problem

The Aerospace Engineering department's Laboratory for Advanced Space Systems at Illinois (LASSI) develops nanosatellites for the University of Illinois. Their next-generation satellite architecture is currently in development, however the core bus does not contain an Attitude Determination and Control (ADCS) system.

In order for an ADCS system to be useful to LASSI, the system must be compliant with their modular spacecraft bus architecture.

# Solution

Design, build, and test an IlliniSat-0 spec compliant ADCS module. This requires being able to:

- Sense and process the Earth's weak magnetic field as it passes through the module.

- Sense and process the spacecraft body's <30 dps rotation rate.

- Execute control algorithms to command magnetorquer coil current drivers.

- Drive current through magnetorquer coils.

As well as being compliant to LASSI specification for:

- Mechanical design.

- Electrical power interfaces.

- Serial data interfaces.

- Material properties.

- Serial communications protocol.

# Solution Components

## Sensing

Using the Rohm BM1422AGMV 3-axis magnetometer we can accurately sense 0.042 microTesla per LSB, which gives very good overhead for sensing Earth's field. Furthermore, this sensor is designed for use in wearable electronics as a compass, so it also contains programable low-pass filters. This will reduce MCU processing load.

Using the Bosch BMI270 3-axis gyroscope we can accurately sense rotation rate at between ~16 and ~260 LSB per dps, which gives very good overhead to sense low-rate rotation of the spacecraft body. This sensor also contains a programable low-pass filter, which will help reduce MCU processing load.

Both sensors will communicate over I2C to the MCU.

## Serial Communications

The LASSI spec for this module requires the inclusion of the following serial communications processes:

- CAN-FD

- RS422

- Differential I2C

The CAN-FD interface is provided from the STM-32 MCU through a SN65HVD234-Q1 transceiver. It supports all CAN speeds and is used on all other devices on the CAN bus, providing increased reliability.

The RS422 interface is provided through GPIO from the STM-32 MCU and uses the TI THVD1451 transceiver. RS422 is a twisted-pair differential serial interface that provides high noise rejection and high data rates.

The Differential I2C is provided by a specialized transceiver from NXP, which allows I2C to be used reliably in high-noise and board-to-board situations. The device is the PCA9615.

I2C between the sensors and the MCU is provided by the GPIO on the MCU and does not require a transceiver.

## MCU

The MCU will be an STM32L552, exact variant and package is TBD due to parts availability. This MCU provides significant processing power, good GPIO, and excellent build and development tools. Firmware will be written in either C or Rust, depending on some initial testing.

We have access to debugging and flashing tools that are compatible with this MCU.

## Magnetics Coils and Constant Current Drivers

We are going to wind our own copper wire around coil mandrels to produce magnetorquers that are useful geometries for the device. A 3d printed mandrel will be designed and produced for each of the three coils. We do not believe this to be a significant risk of project failure because the geometries involved are extremely simple and the coil does not need to be extremely precise. Mounting of the coils to the board will be handled by 3d printed clips that we will design. The coils will be soldered into the board through plated through-holes.

Driving the inductors will be the MAX8560 500mA buck converter. This converter allows the MCU to toggle the activity of the individual coils separately through GPIO pins, as well as good soft-start characteristics for the large current draw of the coils.

## Board Design

This project requires significant work in the board layout phase. A 4-layer PCB is anticipated and due to LASSI compliance requirements the board outline, mounting hole placement, part keep-out zones, and a large stack-through connector (Samtec ERM/F-8) are already defined.

Unless constrained by part availability or required for other reasons, all parts will be SMD and will be selected for minimum footprint area.

# Criterion For Success

Success for our project will be broken into several parts:

- Electronics

- Firmware

- Compatibility

Compatibility success is the easiest to test. The device must be compatible with LASSI specifications for IlliniSat-0 modules. This is verifiable through mechanical measurement, board design review, and integration with other test articles.

Firmware success will be determined by meeting the following criteria:

- The capability to initialize, configure, and read accurate data from the IMU sensors. This is a test of I2C interfacing and will be tested using external test equipment in the LASSI lab. (We have approval to use and access to this equipment)

- The capability to control the output states of the magnetorquer coils. This is a test of GPIO interfacing in firmware.

- The capability to move through different control modes, including: IDLE, FAULT, DETUMBLE, SLEW, and TEST. This will be validated through debugger interfacing, as there is no visual indication system on this device to reduce power waste.

- The capability to self-test and to identify faults. This will be validated through debugger interfacing, as there is no visual indication system on this device to reduce power waste.

- The capability to communicate to other modules on the bus over CAN or RS422 using LASSI-compatible serial protocols. This will be validated through the use of external test equipment designed for IlliniSat-0 module testing.

**Note:** the development of the actual detumble and pointing algorithms that will be used in orbital flight fall outside the reasonable scope of electrical engineering as a field. We are explicitly designing this system such that an aerospace engineering team can develop control algorithms and drop them into our firmware stack for use.

Electronics success will be determined through the successful operation of the other criteria, if the board layout is faulty or a part was poorly selected, the system will not work as intended and will fail other tests. Electronics success will also be validated by measuring the current consumption of the device when operating. The device is required not to exceed 2 amps of total current draw from its dedicated power rail at 3.3 volts. This can be verified by observing the benchtop power supply used to run the device in the lab.