Author: Andrew Hrisak Project Type: Aerospace Engineering Project | Georgia Institute of Technology
This repository contains the flight control software and mechanical design for a custom 2-axis Thrust Vector Control (TVC) gimbal. Utilizing a Teensy 4.1 and an Adafruit BNO055 IMU, the system provides active stabilization for model rocket motors by reacting to gravity vector deflection in real-time.
The gimbal assembly was engineered in SolidWorks with a focus on optimizing weight-to-strength ratios and part durability under high-vibration aerospace environments.
- Material Science: Utilizes PETG for its superior impact resistance and thermal stability over PLA, ensuring structural integrity during motor ignition and flight loads.
- Selective Infill Optimization:
- Structural Components: 15% infill to minimize rotational inertia, reducing the torque required for high-frequency corrections.
- Power Transmission (Gears): 100% infill to ensure maximum shear strength of gear teeth and to maintain precise mesh under load.
- Actuation: Driven by EMAX ES08MA II metal-gear micro servos, selected for their superior durability and 2.0 kg/cm stall torque.
- Controller: Teensy 4.1
- IMU: BNO055
- Mechanical Advantage:
- Lower Axis (Pitch): 120mm Gear / 24mm Pinion (5.0:1 Ratio).
- Upper Axis (Yaw): 166mm Gear / 24mm Pinion (6.91:1 Ratio).
- Precision: The high reduction ratios significantly increase effective torque and provide high-resolution angular control (approx. 0.14° per servo step on the upper axis).
| Component | Pin | Function |
|---|---|---|
| BNO055 SDA | 18 | I2C Data |
| BNO055 SCL | 19 | I2C Clock |
| Lower Servo | 0 | PWM Control |
| Upper Servo | 1 | PWM Control |
The system utilizes a Proportional (P) Feedback Loop. By leveraging the IMU's gravity vector rather than Euler angles, the controller avoids gimbal lock during high-dynamic vertical flight.
Control Law:
Where
Status: Validation Ongoing. Testing is currently underway to implement a full PID controller to incorporate derivative damping, effectively counteracting angular momentum and reducing oscillations during high-velocity maneuvers.
To account for mechanical mounting variances, specific offsets are applied to establish a "True Vertical" baseline:
- Lower Axis (Y) Offset: 0.50.
- Upper Axis (Z) Offset: -0.52.
The firmware includes a 1-second startup safety lock. During this phase, servos are held at neutral trim positions (Low: 82.5° / Up: 95.0°) to allow for physical inspection and sensor stabilization before reactive mode begins.