Stand-Alone Controller for Electroacoustic Resonators

Embedded impedance synthesis controller for active acoustic absorption

Overview

Semester project at EPFL (Laboratory of Wave Engineering) in collaboration with LG Electronics.

This project focused on migrating an impedance synthesis control architecture for electroacoustic absorbers from a laboratory-grade Speedgoat real-time system to a stand-alone embedded solution based on the STM32F767ZI microcontroller.

The goal was to implement a second-order impedance control law derived from the physical loudspeaker model, enabling active low-frequency acoustic absorption in a compact and cost-effective system.

The continuous-time controller was discretized using the bilinear (Tustin) transform and implemented as a real-time biquad filter running at 20 kHz on an ARM Cortex-M7 MCU with hardware FPU support.

Technical Highlights

  • Derived and discretized a second-order impedance synthesis controller
  • Implemented deterministic timer-driven real-time control (interrupt-based architecture)
  • Integrated CMSIS-DSP to leverage hardware floating-point acceleration
  • Designed full ADC/DAC signal chain with DC bias handling and output conditioning
  • Validated transfer function using hardware-in-the-loop measurements
  • Benchmarked embedded implementation against Speedgoat reference system

The final MCU-based controller successfully reproduced the qualitative behavior of the reference system, demonstrating that a low-cost microcontroller architecture can replace high-end rapid-prototyping hardware for this application.

Custom Tooling

To streamline experimentation, I developed a Python-based GUI that:

  • Computes continuous and discrete filter coefficients
  • Generates firmware parameters automatically
  • Builds and flashes the MCU firmware
  • Provides transfer-function validation before deployment

The GUI is distributed through a GitHub Actions CI pipeline generating standalone installers.

  • 🔗 The full implementation is available on GitHub
  • 📄 PDF Report: View Report

Supervisor

  • Dr. Hervé Lissek