Low weight and inertia self balancing testbed for a 3U cubesat attitude control system

The design, implementation, and testing of an Attitude Control System (ACS) for nanosatellites require a simulated environment that replicates the conditions of Low Earth Orbit. Key factors such as the absence of friction and gravitational effects must be achieved in an attitude control testbed. Additionally, a platform with low weight and inertia ensures that the small actuators of a CubeSat can rotate the system without requiring excessive effort. The testbed developed at Universidad Católica San Pablo was manufactured using lightweight materials, including 3D-printed PLA parts, carbon fiber tubes, and acrylic boards. Unlike other self-balancing testbeds, this work introduces a shifting mass approach, where a DC motor acts as both actuator and shifting mass, significantly reducing weight. The position of the shifting masses along their axis is controlled by a Linear Quadratic Regulator (LQR). The platform’s attitude estimation is performed using an Extended Kalman Filter (EKF), which combines data from low-cost accelerometer, gyroscope, and magnetometer sensors. A nonlinear control system is implemented for the automatic balancing procedure, mitigating gravitational disturbance torque by using the estimated gravity vector to drive the shifting masses and minimize platform tilt. Finally, a Least Squares Method (LSM) compensates for residual vertical misalignment after the balancing procedure, enabling precise center of mass (CM) control in all axes. Obtained results demonstrate the DC motor shifting mass approach reduces total platform weight by 72% compared to other works while achieving precise balancing with less than 210 μm residual misalignment between the center of mass (CM) and center of rotation (CR) and 92% reduction in kinetic energy variance during operation.