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Reaction Wheel Balancing
Dynamic spacecraft attitude control using angular momentum exchange. Implements closed-loop stabilization with custom control loops and real-time angular momentum management.
Overview
Reaction Wheel Balancing demonstrates closed-loop attitude control of a spacecraft using angular momentum exchange. By spinning reaction wheels at controlled speeds, the system can torque the spacecraft body without expelling propellant — a core technique in modern satellite ADCS.
Control Architecture
The controller operates on a feedback loop:
- Sensing — IMU measurements provide angular velocity and attitude quaternion estimates.
- Error Computation — The error quaternion between current and desired attitude is extracted.
- Control Law — A PD controller generates a desired torque vector to drive the error to zero.
- Actuation — Torque commands are distributed across the wheel array using a pseudo-inverse allocation matrix.
Key Concepts
- Momentum saturation handling — Tracks accumulated angular momentum and applies desaturation maneuvers when wheels approach speed limits.
- Singularity avoidance — Wheel geometry is chosen to avoid gimbal-lock-like singular configurations.
- Real-time loop — The control loop runs at a fixed rate using a timer interrupt to guarantee deterministic execution.