Custom BLDC Motor & DSP-Based Control System

## Overview This project covered the full stack of brushless DC motor design: mechanical construction, power electronics, and real-time DSP firmware. The goal was a working open-loop SPWM drive as a foundation for a future closed-loop FOC implementation. ## Motor Construction Designed and hand-wound a **9-pole stator BLDC motor** with a **6-magnet (3 pole-pair) rotor**. The winding process required evaluating startup torque, rotor inertia, and thermal current limits to set safe operating parameters before any firmware was written. ## Firmware — Open-Loop SPWM Implemented open-loop sinusoidal PWM firmware on a **TI TMS320F28377D dual-core DSP**, generating real-time three-phase inverter gate signals. Development and debugging was done via **isolated JTAG** in Code Composer Studio. The firmware generates six PWM channels at a configurable carrier frequency, applies dead-time insertion to prevent shoot-through, and ramps frequency on startup to build back-EMF before transferring to the target speed. ## Fault Diagnosis Diagnosed a **stall and oscillation-under-load fault** traced to a pole-pair mismatch in the open-loop frequency calculation. The firmware had assumed 4 pole-pairs; the motor has 3. Correcting the constant immediately restored stable rotation — a good reminder to verify mechanical parameters match firmware constants before chasing electrical faults. ## Hardware Revisions Resolved failures across **three inverter hardware revisions**: - **Rev 1** — ESC threshold mismatch; bootstrap capacitor sizing caused gate undervoltage lockout at low duty cycles. - **Rev 2** — MOSFET shoot-through due to insufficient dead-time margin at higher switching frequencies. - **Rev 3** — Coil overheating under sustained load; resolved with reduced duty cycle ceiling and improved thermal relief in the PCB layout. ## Path Forward Defined the transition path to: 1. **Hall-effect feedback** for rotor position sensing 2. **Space Vector PWM (SVPWM)** for improved DC bus utilization 3. **Closed-loop Field Oriented Control (FOC)** for torque-controlled operation