6U CubeSat with Orthogonal Spinning Sensors

UC Berkeley, Autodesk, National Instruments, & Space Sciences Laboratory

Introduction

To improve the sensitivies of measurements, we examine the design of a spacecraft capable of using spinning probes on two orthogonal axes to gather data. The objective of this research project is to build simulation models of the satellite and perform experiments to improve our confidence in the control of the spacecraft in a zero-gravity environment.

Computer Aided Design

Using Autodesk Inventor, we create an accurate CAD model of the satellite and extract mass properties for the simulation model. Key components of the satellite include the flywheels for attitude control, the four-bar deployment mechanism for the spinning booms, and electronics to control the flywheel and spinning booms. We create various designs to optimize the locations of the flywheels and use simulation to guide our final decision. We studied tumbling and torques required to stabilize the satellite to create motor specifications necessary for attitude control.

Simulation & Control System Design

Using Modelica MultiBody Library, we can create a simulation model of the CubeSat and add appropriate multimedia elements for control. Flywheels and spinning booms were created with revolute joints and body cylinders from the Modelica MultiBody Library. The following two videos show the CubeSat with and without an attitude control system. By using LabVIEW and hardware from National Instruments, we can use the same control system developed using the simulation for the real-time system. Using the Functional Mockup Interface (FMI), we can produce a Functional Mockup Unit (FMU) using JModelica and import the Modelica model into LabVIEW.

Rapid Prototyping

Once behavior of the satellite in simulation is satisfactory, the CubeSat is manufactured from the CAD model and tested against the simulations to verify the accuracy of the models and effectiveness of the attitude control system.

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Model-Based Design of a Satellite with Orthogonal Spinning Sensors