1 of 1

Department of Electrical and Computer Engineering

Project Statement

Design a dual motor driver capable of taking commands from the OreSat Attitude Control and Determination System and translate the command to the respective actuator powered directly from the battery bank

OreSat

Oregon’s First Satellite

Portland State Aerospace Society

Attitude Control System (ACS)

Driver Board

Team Members

Andrew Capatina B.S. Computer Engineering

Chad Coates B.S. Computer Engineering

Armaan Roshani B.S. Computer Engineering

Max Schweitzer B.S. Computer Engineering

Nathaniel Dusciuc B.S. Electrical Engineering

Eric Ruhl B.S. Electrical Engineering, � B.S. Physics

​

​

Key Design Requirements

  • Able to communicate over and receive power from the OreSat Backplane
  • Minimize power usage while maintaining sufficient torque levels.
  • Minimize standby power consumption.
  • Adaptable design easily changed to accommodate different operational parameters
  • Board layout must accommodate a modular design with a maximum allowable driver system volume of 4 x (50mm)3
  • Runs from a microcontroller
  • Meets or exceeds OreSat Survivability Standards
  • Able to implement Phase Vector Control over the BLDC motor driver
  • Documentation of operation and source code for system implementation in previous Capstone Projects, including the EFS and eNSR

Future Implementation

  • Fully automated Motor Characterization
  • Power Optimization using current feedback
  • Acceleration curve adjustments made from inertial measurements of the motor

Background and Motivation

OreSat is Oregon’s first satellite. For purposes of communication and photography, OreSat will need to point at specific locations on Earth as it orbits overhead. To accomplish this, we will use an ACS consisting of four reaction wheels and three magnetorquers. Four ACS Driver Boards will be the interface between the orientation controller and these actuators.

For more information about the OreSat Project, visit oresat.org

Firmware

The ACS is written in C using the ChibiOS platform. ChibiOS is a powerful, light weight, and open source real time operating system.

We use ChibiOS drivers for reading ADC current feedback, communication with the encoder via SPI, and PWM for actuating the magnetorquers and reaction wheels.

​

The ACS functions using a Mealy state machine driven by CAN input from the flight computer. This state machine is used for partitioning the control logic between the magnetorquers and reaction

wheels.

Hardware

OreSat Standard-These are the parts that were recommended

TPS63070- Buck Boost Converter

TCAN330- CAN Transceiver

STM32F04K6- Cortex M0 microcontroller

​

Board Specific- These are parts that were selected by the capstone team and why

STSPIN230 - Brushless DC Motor Driver

  • Easy interface with STM32F0
  • Full Control over Phase Output
  • Minimal External Components
  • Satisfy thermal and voltage constraints

STSPIN250 - Brushed DC Motor Driver

  • Small package size
  • Basic Magnitude and Phase control
  • Minimal External Components
  • Satisfy thermal and voltage constraints

AS5047P - 14 bit Axial Encoder

  • High speed range & precision
  • No moving parts
  • Multiple output types for versatile control solutions

​

​

Development Process

  • The ACS team subdivided into two groups: hardware and software
    • Allowed for concurrent development of hardware and software
    • Three weekly meetings (general, hardware, firmware)
    • We set goals, discussed progress, assigned individual tasks, and completed weekly progress reports as a team

​

  • Firmware development:
    • Rapid prototyping via breakout boards and development tools
    • Individual subsystems developed, tested, and integrated using development kits

​

  • Hardware development:
    • Identified hardware components that satisfy the physical constraints of the project; such as, thermal and voltage requirements
    • Designed circuit schematics for necessary functionality
    • Designed board layout to meet dimensional constraints for compatibility with OreSat

Board Layout

The board layout was developed in conjunction with the mechanical engineer designing the structural mount for the control boards and motors (Fig. 4). The mount also act as thermal sinks which will mate to the large areas of exposed copper at the mounting interface.

GitHub Wiki

https://github.com/oresat/oresat-acs-board/wiki

Figure 3: Layout rev3 (above) Figure 4: Structural Mounting System (below)

Figure 2: Development Setup

Special Thanks

Miles Simpson

Help with implementing ChibiOS as well as working with us to maintain code consistency with the rest of OreSat

Joe Shields

Mounting and structure constraints and design, assisted with final board layout

Joshua Lake

Control theory and characterization, assisted with development of our design and control paradigm

Erin Schmitt

Answered conceptual and technical questions about the prior capstone focused on attitude control

Andrew Greenberg, our industry advisor

Yih-Chyun Jenq, our faculty advisor

​

Figure 1: System Diagram

BLDC Motor

ACS Driver Board