Team Vision for Detailed Design PhaseDuring the fourth phase, a detailed design was developed. The goals for the fourth phase are outlined below:
- Reaction Wheel
- Create a finalized model and drawing of the motor and flywheel.
- Develop a generic motor controller model.
- Raspberry Pi
- Prototype the camera.
- Prototype interfacing with the temperature and pressure sensors.
- Prototype the current draw.
- Prototype the communication between a Raspberry Pi and a MSP430
- Create a schematic for booster pack (Pi Hat)
- Create a connections schematic
- Create a schematic for the interface between power and sensors
- Prototype the IMU, SD cards, motor control, UART, COMMs, SPI.
- Create a schematic of the main host board.
- Create a schematic for the system level design.
- Create a software flowchart.
- Finalize cut-down mechanism design, schematic, and functionality.
- Create a wiring schematic.
- Decide if a custom PCB is needed.
- Part selection with footprints for the board.
- Create a schematic in Eagle.
- Other Documentation
- Develop detailed block diagrams for each of the subsystems.
- Create a complete bill of materials, with cost, vendor lead time, and weight information provided.
The above goals were completed as fully as time could allow. All of the goals, aside from those stated below, were completed:
- Reaction Wheel
- A general outline of the reaction wheel controller was developed, with the constants to be determined next semester. The motor and controller were delivered in the middle of the semester, without enough time to do testing.
- Raspberry Pi
- Create a layout for the Pi Hat board.
- Update the software to be best practice/ready for launch.
- Motor control
- A nearly completed bill of materials may be found below.
The tables below show the progress of the team prior to Thanksgiving break on November 22nd. By the end of the semester and upon the completion of MSD I, it is hoped to have the “percent complete” column to be 100% for all task items.
This report shows multiple tables, including the tasks needed to be accomplished prior to the detailed design review, the tasks currently completed, remaining tasks to be completed, as well as an overview of the drawings and schematics that will be needed for this project. Other questions that were asked to be reviewed by the guide may also be seen below.
What decisions have been made so far?
The need to create a custom PCB boards for both Raspberry Pi and MSP430 for power and sensor connections has been decided. The majority of components have also been decided upon.
What questions does the team have for the customer and/or guide in order to continue moving forward?
Do we need a 3D wiring model? This was discussed in class last week with Vince.
What % of critical parts or material ordered?
Approximately 80% of critical parts have been ordered for early stage development in MSD I.
What % of critical parts actually received or fabricated?
Approximately 70% of critical parts have been received by the team.
What % completed of the wiring/harnessing design?
Approximately 10% of the wiring/harnessing has been completed. There has been more work in regards to how all of the sensors will be physically connected and mounted. The design of the Pi Hat and MSP430 Booster pack will finalize this.
Updated High Level System DiagramMajor changes from the previous architecture include:
- Use of two MSP430 controllers (denoted HOST and MOTOR). The HOST controller activates the emergency cutdown if necessary.
- Use of custom Raspberry Pi Zero HATs for power conversion and sensor acquisition.
- Detailed design of the GRSS module.
Prototyping, Engineering Analysis, Simulation
Reaction Wheel Analysis
From these calculations, it may be determined that a flywheel may not be necessary, as the motor itself has a rotor housing that rotates. This rotor housing, with the correct acceleration and velocity, may be able to supply enough movement and momentum to counteract the movement of the instrumentation platform. Several flywheel sizes however will be tested during MSD II in order to determine the best way to rotate the instrumentation platform.
The two pictures above show the two views of the software available for the motor controller. This allows the user to change the speed of the motor, gains of the controller, and other relevant information to the controller.
Drawings, Schematics, Flow Charts, Simulations
Reaction Wheel AssemblyThe picture below show the assembly models and drawings for the reaction wheel assembly. Although the calculations above show that the motor assembly may not be necessary for the instrumentation platform, a drawing was made so that flywheels can still be tested.
To view the drawing above closely, please see the PDF below. The drawing above will be updated with tolerances once a subject matter expert is spoken to.
The active working document for the motor model can be found here.
The active working document for the flywheel model can be found here.
The active working document for the assembly can be found here.
The active working document for the motor assembly drawing can be found here.
Updated Motor ControllerThe motor controller flowchart was updated to include an angular velocity PID controller, as well as a power PID controller. The constants for the PID controllers have not been determined yet, but will be finished and tested next semester.
GRSSThe GRSS has been updated to utilize the LMC555 timer from TI because it can use a lower supply voltage. Therefore, it has been configured for a 50% duty cycle 1Hz square wave that will continuously turn the lights and buzzer on and off. A Power FET has been chosen that has a gate voltage of 2V. Therefore, since the 555 timer oscillates between 1/3 and 2/3 Vin, a 4.5V LDO has been selected to have the gate of the FET oscillate from 1.5V to 3V.
The schematic for the GRSS can be found here: GRSS Schematic
The schematic for the GRSS Board can be found here: GRSS Board Schematic
The BOM can be found here: GRSS BOM
DAQCS Host MSP430 Board High Level System Diagram
DAQCS Host MSP430 PCB Board SchematicsThe MSP430 Host Board will be used to mount connectors and sensors that will be directly interfacing with both of the MSP430 host controllers. One of the MSP430's will be used to handle the communcations between boards, and the other will be responsible for controlling the motor and collecting various sensor data.
A PDF of the schematic can be found here: DAQCS Host MSP430 PCB Board Schematics
DAQCS Host MSP430 PCB Board BOM
A working document of the BOM can be found here: DAQCS Host MSP430 BOM
Host MSP430 Software FlowchartThe following flowchart is a high level diagram outlining the firmware functionality of the Host MSP430. This functionality includes interfacing with all of the Raspberry Pis and sending commands to the Motor MSP430.
Motor MSP430 Software FlowchartThe following flowchart is a high level diagram outlining the firmware functionality of the Motor MSP430. This functionality includes interfacing with the motor and sensors necessary to drive the reaction wheel.
Raspberry Pi Zero Power/Sensor HAT Block Diagram
Raspberry Pi Zero Power/Sensor HAT Schematics
Raspberry Pi Zero Power/Sensor HAT BOM
Component Schematics & Data SheetsA separate page has been created create a repository for the components' schematics and data that were bought.
This page may be accessed by clicking here.
Design Review MaterialsThe Detailed Design Review presentation can be found here.
Schematics covered during the review are located on this page.
Plans for Next PhaseMSD II Schedule & Plan
Individual PlansSydney Kaminski's Three Week Plan: Sydney's Goals
Steven Giewont's Three Week Plan: Steven's Goals
Lincoln Glauser's Three Week Plan: Lincoln's Goals
Chris Schwab's Three Week Plan: Chris's Goals