University of Toronto Students Work with Space Flight Laboratory Engineers to Design and Simulate Nanosatellite Control Systems

In addition to mass and volume constraints, nanosatellites have a limited ability to generate power. SFL’s tight budget and accelerated launch schedule led the engineers to use readily available, lower-cost commercial electronics instead of radiation-hardened components. “To ensure that these parts will work reliably in space, we need to be very careful in how we design around them,” says Zee.

Because the effects of gravity and air currents make it impossible to fully test a precision attitude control system in the lab, SFL had to rely on simulation to predict on-orbit performance.

To train graduate students in space systems engineering, SFL required development tools that students already knew or could learn quickly. The tools needed to facilitate collaboration between engineering teams and enable the students to acquire practical experience that they could leverage in their careers.

Graduate students and space systems engineers at SFL used MathWorks tools to design, simulate, and build the attitude control systems for CanX-2 and other nanosatellites.

Before working at SFL, the graduate students completed Microsatellite Design I and II, courses taught by Zee, in which they used MATLAB^® and Simulink^® to build a preliminary design of a satellite system.

In Simulink, the SFL team modeled the sensors used to determine the nanosatellite’s position and orientation, including sun sensors, magnetometers, star trackers, and GPS receivers. They also modeled the components used to control the satellite, including reaction wheels, cold gas propulsion systems, and magnetorquers. The component models reflected the actual satellite’s interface and sampling period.

SFL used MATLAB and Control System Toolbox™ to develop control algorithms for the attitude control system. Using Simulink they combined the sensor, actuator, and controller models with a model of the satellite’s mass, and then simulated the system to assess its performance in a zero-gravity environment.

Aerospace Toolbox enabled the team to estimate atmospheric drag and perform re-entry analysis for de-orbiting scenarios.

SFL used a thermal chamber to test the electronic components in temperature ranges encountered in space. Using Data Acquisition Toolbox™ they collected the test data for analysis in MATLAB. MATLAB was also used to model power systems and perform transient power condition analysis of the nanosatellites’ batteries.

The team is using MATLAB to analyze telemetry data downloaded from CanX-2 and CanX-6, which are now on orbit.

Currently, SFL is working on CanX-4 and CanX-5, two nanosatellites that will demonstrate precise autonomous formation flying in low earth orbit, as well as CanX-3, a group of four nanosatellites that will be used for space astronomy.