Amazing Ball Control with PD Controller on dsPIC33F

Implementation of a PD-controlled ball balancing system on a dsPIC33F-based touchscreen servo platform

In the MW2411 – Concepts and Software Design for Cyber-Physical Systems laboratory, we worked with the Amazing Ball System (ABS) — an embedded real-time control platform built around a Microchip dsPIC33FJ256MC710 microcontroller, servomotors, and a 4-wire resistive touchscreen.

🔹 Project Goal

The objective of Amazing Ball Control was to design a real-time PD controller capable of moving a steel ball along a circular trajectory on the touchscreen by precisely tilting the plate through servo actuation. The system continuously tracks the ball’s position and corrects deviations from the reference trajectory in real-time.

🔹 System Architecture

The hardware consists of:

  • dsPIC33FJ256MC710 microcontroller (40 MIPS)
  • Two servo motors for X/Y plate actuation
  • 4-wire resistive touchscreen for real-time position feedback
  • LCD module (UART-based) for displaying system status and deadline misses
  • FLEX-UI board stack with LEDs, joystick, and DACs for interfacing and debugging

All software was implemented in C using MPLAB X IDE, with direct register-level programming for the ADC, timers, PWM output, and UART peripherals.

🔹 Control & Software Design

  • Sampling: Touchscreen X/Y coordinates were read alternately at 100 Hz.
  • Filtering: A 1st-order Butterworth low-pass filter (3 Hz cutoff) was implemented to remove signal noise.
  • Control Law: Independent PD controllers were developed for each axis. Controller parameters were tuned experimentally to ensure smooth circular motion.
  • Reference Trajectory: Circular path generated at 50 Hz, configurable via preprocessor macros.
  • Scheduling: A periodic timer interrupt maintained strict real-time execution; a counter tracked any missed deadlines.
  • Display: The system printed real-time performance metrics and deadline counts to the LCD at 5 Hz.

🔹 Engineering Highlights

  • Integrated multiple peripherals (ADC, PWM, UART, LCD, touchscreen) within a deterministic real-time loop.
  • Achieved stable circular ball motion through optimized PD gains and signal filtering.
  • Validated real-time performance via deadline monitoring and debugging using LEDs and LCD output.
  • Developed under strict timing constraints to ensure system responsiveness and control precision.

🔹 Outcome

Our group successfully demonstrated continuous circular motion of the ball on the touchscreen..

🎥 Watch Demo Video on YouTube

Team: Oğuzhan Eşen, Ercan Kaçmaz, Mert Kulak, Iliasu Salaudeen