Ball and Beam Balancing System with PID Control

The ball and beam is the canonical teaching rig for feedback control because it is simple to see and hard to tame: the ball accelerates away from any tilt, so only a well-tuned controller can hold it still. Students of control theory usually meet PID as equations on a slide; this project makes it physical. An ultrasonic sensor measures the ball's position along the beam, an Arduino runs the PID loop, and a servo tilts the beam through a linkage arm to drive the ball toward the setpoint. The real learning is the tuning: starting from proportional-only oscillation, adding derivative to damp it, and discovering what integral does to steady-state error — each stage documented with response plots from the student's own rig. It is the rare project where the viva practically runs itself.

1. The steel ball rests on the aluminium beam; the ultrasonic sensor at one end continuously measures the ball's distance (position).
2. The Arduino reads the position, computes the error against the setpoint, and runs the PID calculation each control cycle.
3. The PID output drives the servo, which tilts the beam through the linkage arm — tilting toward the ball to slow it, away to accelerate it back.
4. With proportional control only, the ball oscillates; the student increases derivative gain to damp the oscillation.
5. Integral gain is added to remove the steady-state offset, with anti-windup preventing overshoot after large disturbances.
6. The tuned system holds the ball at the setpoint and recovers from a finger-tap disturbance — the standard live demo.
7. Position data logged over serial produces step-response plots for the report, documenting each tuning stage quantitatively.

Tech stack:

• Arduino Uno (PID controller)
• Ultrasonic distance sensor
• High-torque servo motor
• Aluminium beam + pivot frame
• Linkage arm mechanism
• Serial data logging
• 5–6 V servo power supply
• PID tuning procedure

• [Full PID implementation] Position PID loop running on the Arduino with configurable Kp, Ki and Kd — the student tunes all three terms experimentally, not just in simulation.
• [Ultrasonic ball tracking] An ultrasonic sensor at the beam end measures ball position continuously, demonstrating real sensor feedback with noise and dead zones.
• [Servo-linkage actuation] A high-torque servo drives the beam through a mechanical linkage, showing how control signals become physical motion.
• [Setpoint control modes] Hold-position, step-change and (firmware option) sine-tracking modes let the student demonstrate different control scenarios.
• [Live tuning interface] PID gains adjustable via serial commands or potentiometers, so tuning iterations happen in seconds during the demo.
• [Response plotting] Logged position-vs-time data exports for step-response plots — the evidence section of the report comes from the student's own rig.
• [Anti-windup and filtering] Integral anti-windup and sensor filtering implemented in firmware, teaching the practical details textbooks gloss over.

• Ball-and-beam rig (assembled: beam, pivot, servo, linkage, sensor)
• Arduino controller (programmed with PID firmware)
• Complete firmware source code with gain-adjustment interface
• PID tuning procedure document (Ziegler-Nichols + manual method)
• Wiring diagram and mechanical assembly guide
• Data-logging guide for response plots
• Project report PDF (background, control theory, tuning study, results)
• PPT presentation for final review
• Viva Q&A preparation document (PID terms, stability, tuning, anti-windup)

• The ultrasonic sensor has a dead zone and noise; position accuracy is approximately ±5 mm, which the report states honestly.
• The rig balances one ball on one axis — it does not demonstrate multi-axis or nonlinear control beyond this plant.
• Servo backlash and linkage play limit the achievable precision; the tuning guide works within these mechanical realities.
• Aggressive gains cause oscillation or ball drop-off — the tuning procedure approaches stability conservatively by design.
• Step-response figures in the report come from the student's own rig and tuning session, presented as measured-on-prototype.
• The beam must be level-calibrated at setup; the procedure document covers this buyer-run step.