# ECE 3510 – Introduction to Feedback Systems – Labs

Project: Magnetic Levitation Control System

This is a five week long experiment about frequency and amplitude modulation. Using electronic components, students build a frequency shift keying (FSK) circuit. Both modulator and demodulator modules are constructed and tested. The carrier frequencies used here are 1 kHz and 5 kHz, for representation of logical 0 and 1, respectively. We have purposefully chosen these low frequencies to allow straightforward prototyping in the laboratory using bread boards. The concepts from this experiment are expanded in the EM class where students build the FSK system in the MHz range.

## Project 1 – Control of Brush DC motor Lab 1- Step Response of a First order system

The objective of this lab is to study the characteristics of step responses of first-order systems. A brush DC motor is used for the experiments. Concepts of time constant and DC gain are introduced. Discrepancies between the idealized first-order model and the actual responses are observed. An objective of the first lab is also to become familiar with the hardware and the software in the lab.

Voltage Control Lab (pdf),
Experiment files

Lab 2- Step Response and sinusoidal response of a second order system

The objective of this lab is to study the characteristics of step responses and of sinusoidal responses for second-order systems. Critically damped and underdamped systems are considered. Concepts of rise time, settling time, percent overshoot, and frequency of oscillations are introduced for step responses. For sinusoidal inputs, the steady-state responses are studied first, and peaking in the frequency domain is observed for underdamped systems. Transient responses are also investigated.

Proportional Control Lab (pdf),
Experiment files

Lab 3 – Proportional-Integral-Derivative controls law

The objective of this lab is to study basic design issues for proportional-integral-derivative control laws. Emphasis is placed on transient responses and steady-state errors.
The first control problem consists in the regulation of velocity for brush DC motors and is solved using proportional-integral control. The second problem consists in the regulation
of position and requires derivative compensation in the form of velocity feedback.

PID Control Lab (pdf),
Experiment files

Dspace system tutorial

## Project 2 – Timing acquisition Lab 4 – Basic Phased-Lock Loop concepts

The objective of this lab is to learn the basic concepts of operation of phase-locked loops (PLL). Experiments cover the measurement of the gain of a voltage-controlled oscillator and the construction of a PLL with a first-order filter. PLL properties such as capture range, hold range, transient response, and steady-state ripple are measured, and correlated with analysis results.

Basic PLL (pdf)

Lab 5 – Advanced Phase-Locked Loop Concepts

The objective of this lab is to refine the design of the loop filter used in the basic PLL lab, and to evaluate the improvements in performance. A second-order filter replaces the first-order filter of the basic PLL lab, and a better phase detector is used. The selection of the filter is an example of control system design with integral action and lead compensation.

Specs. for CD4046

## Project 3 – Applications of Motor Control Lab 6 – Control of an Inverted Pendulum

The objective of this lab is to experiment with the stabilization of an unstable system. The inverted pendulum problem is taken as an example and the animation program gives a feel for the challenges of manual control. A stabilizing linear controller is designed using root-locus techniques, and the controller is refined to enable stabilization of the inverted pendulum at any position on the track.

Inverted Pendulum (pdf)

Lab 7 – Control of a Flexible Beam

The objective of this lab is to learn about the challenges posed by resonances in feedback systems. An intuitive understanding will be gained through the manual control of a flexible beam resembling a large space robotic arm. Control design will be performed in the frequency domain using a lead controller. A notch filter will be incorporated in the feedback loop in order to reduce the excitation of resonances.

Flexible Beam (pdf)

Ball and Beam (pdf)