Project Vulcan 24-25, Airbrakes Controls

Closed-loop airbrake control with Kalman-based state estimation, HIL/SIL validation, and flight testing.

Overview

The airbrake control system regulates aerodynamic braking to ensure the Vulcan rocket reaches its target apogee. Our research explored advanced methods such as PID and adaptive control, but given time and experience constraints, we implemented a simplified threshold-based deployment strategy. This mechanism activates the airbrakes when the error signal—defined as the difference between modeled and measured drag—exceeds a predefined threshold.

Fail-safes are incorporated to guarantee reliability:

  • Timed activation within a defined flight window.
  • Sensor cross-validation to reduce false triggers.
  • Real-time health checks for actuator/sensor integrity.

Design Analysis

In aerospace applications, a control system is best understood as the integration of three interdependent functions:

  • Navigation — estimating the vehicle’s state (position, velocity, acceleration, orientation) using onboard sensors.
  • Guidance — generating target instructions, such as desired apogee altitude.
  • Control — executing guidance commands via actuators (airbrake servos in our case).

For Vulcan, analysis focuses on the midcourse (coasting) phase—the period between motor burnout and apogee. During this phase:

  • Thrust is zero, so both mass and inertia are constant.
  • The rocket behaves as a rigid body under translational and rotational motion.
  • Dominant forces are:
    • Gravitational force ((F_g))
    • Aerodynamic drag force ((F_A(u))), modulated by airbrake openness (u)
    • Disturbance forces ((F_N)) such as wind or turbulence

System Overview

Sensor → Estimator (Kalman) → Controller → Airbrake Actuator.

Stack & Hardware

  • MCU: STM32
  • Buses: I2C for IMU/Baro, UART for telemetry, CAN for inter-board
  • Tooling: PlatformIO, MATLAB/Simulink, Python, Post-processing in Jupyter

References