Deneme2

AntigravityFOC: Bare-Metal CORDIC-Accelerated Motor Controller

A completely from-scratch, bare-metal implementation of Field-Oriented Control (FOC) tailored for ultra-low inductance (~3 µH) drone motors (e.g., A2212). Built on a custom-designed STM32G4 PCB, this project bypasses heavy abstraction layers (like HAL and ST MC SDK) to achieve microsecond-level execution times and maximum hardware utilization.

🚀 Key Engineering Achievements

• Blistering 40 kHz Control Loop: Pushed the STM32G4 (150 MHz) to a 25 µs execution window.
• Extreme Execution Efficiency: Through bare-metal register manipulation, FPU caching, and eliminating heavy libraries (fmodf), the complete FOC ISR execution time was profiled and reduced from 2700 ticks to just 1055 ticks (~7 µs). The CPU remains 72% idle even at 40 kHz.
• Ultra-Low Noise Sensing: Achieved an ADC noise floor of just 1.5 LSB standard deviation by utilizing 16x hardware oversampling and triggering the Injected ADC precisely at the TIM1 PWM valley (TRGO2).
• CORDIC Hardware Acceleration: Offloaded heavy trigonometry (Clarke/Park transforms) to the on-chip CORDIC co-processor, calculating simultaneous Sine and Cosine in Q1.31 format in just 24 cycles.

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🧠 System Architecture & Development Phases

1. Hardware Synchronization & Dead-Time

• TIM1 Configuration: Center-Aligned Mode 2 at 40 kHz. Dead-time is finely tuned to 45 ticks (~300 ns), verified against the PJD80N06SA-AU MOSFET specifications to ensure zero shoot-through.
• ADC Triggering: TIM1_CH5 generates a TRGO2 rising edge precisely at the PWM valley, ensuring phase currents are sampled when switching noise is mathematically zero.

2. Precision Current Sensing & VBUS Tracking

• Symmetry & Offset: The custom shunt architecture (5 mΩ + TLV9062) yielded a near-perfect hardware symmetry with a phase difference of only 21 raw counts.
• Dynamic VBUS Tracking: The system continuously monitors battery voltage and dynamically recalculates the Space Vector PWM (SVPWM) modulation limits in real-time.

3. High-Speed SPI & Angle Estimation

• Bare-Metal SPI: The AS5047D magnetic encoder is read via bit-banged SPI for maximum speed (≤ 9.375 Mbps), parsing the 14-bit absolute angle.
• Angle Extrapolation (Phase Delay Compensation): To combat the 5–8 µs calculation/ADC delay at high speeds (>5000 RPM), a predictive angle compensator ($\theta_{comp} = \theta_{measured} + \omega_{e} \times T_{delay}$) ensures the D-Q reference frame remains perfectly aligned.

4. Space Vector PWM (SVPWM)

• Implemented a highly optimized Min-Max Zero-Sequence Injection algorithm. This centers the duty cycles, maximizes DC bus utilization, and generates a mathematically perfect sine wave across the motor phases without using lookup tables.

5. Cascaded Control Loop (Custom Anti-Windup PI)

Instead of relying on standard library PID functions, the inner and outer loops are driven by a custom-written discrete PI controller architecture.

• Inner Current Loop (D-Q Axes): Targets a tight 3–5 kHz bandwidth to tame the massive $di/dt$ of the 3.08 µH motor. It features a custom Conditional Anti-Windup algorithm that smartly freezes the integrator only when the output is saturated in the direction of the error, allowing for instantaneous recovery from voltage limits.
• Outer Speed Loop: Eliminated 40 kHz high-frequency quantization noise by developing a custom Angle Accumulator with a 400x downsampling ratio (updating at 10 ms). The result is a buttery-smooth speed estimation fed into the outer PI controller, featuring a first-order setpoint ramp to prevent sudden torque steps while driving the motor up to 12,000 RPM.

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📊 Hardware & Telemetry Validation

To validate the math against physical reality, a custom non-blocking RAM logger was built to export high-speed telemetry without disrupting the 25 µs control loop. Detailed analysis is available in the /Results directory.

1. Outer Loop: Critically Damped Speed Response

The motor accelerates from 0 to 4000 RPM with an industrial-grade, critically damped profile. Zero overshoot, zero ringing.
(See: Results/Figure-3.png and Results/step_response.mp4)

2. Inner Loop: D-Q Current Stability

Maintaining $I_d = 0$ (Maximum Torque Per Ampere) while injecting the exact required $I_q$ (Torque) current to accelerate the rotor.
(See: Results/Figure-4.png)

3. Oscilloscope Proofs (SVPWM)

• Phase-to-GND (Saddle Wave): Physical proof of the FPU computing the Min-Max Zero-Sequence injection. (See Results/Figure-1.jpeg)
• Line-to-Line (Pure Sine): Proof that zero-sequence harmonics cancel out, delivering a pure sine wave to the stator. (See Results/Figure-2.jpeg)

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📂 Project Structure

• /Firmware - STM32CubeIDE project workspace containing the complete bare-metal C source code (/Core), CORDIC integration, and custom PI controllers.
• /Hardware
  • /Kicad_Files - Source files for the custom PCB design.
  • Board.jpeg - Photo of the physical PCB prototype.
  • Board_3DView.jpg - 3D render of the PCB.
  • BOM_LIST.csv - Bill of Materials.
  • Schematic.pdf - PDF schematic of the motor drive and MCU.
• /Results
  • Figure-X - Telemetry PNGs and Oscilloscope JPEGs verifying the control theory.
  • step_response.mp4 - Video of the motor achieving 4000 RPM seamlessly.
  • readme.md - In-depth breakdown of the telemetry and scope results.

📝 License

This project is open-source and available under the MIT License.