Analog Lead Compensator Circuit

Introduction

Part 1 of Benchtop Labs for Digital Control course.

The purpose of this lab experiment is to model a satellite in the analog domain as a double integrator using op amps. As a double integrator is inherently unstable, an analog controller must be added to the system. In this experiment, a lead compensator is to be used as the controller for this system.

Full project details

Project Overview

Type: Individual
Timeframe: Approx. 1 month
Relevant Concepts/Skills: Research, component selection, analog circuit design, analog circuit testing, control theory, analog controller design, (lead) compensator, circuit simulation, operational amplifier (op-amp)
Tools: Simulink, Cadence OrCAD PSPICE, digital function generator, digital multimeter (DMM), DC power supply, digital oscilloscope
Deliverable(s): Physical circuit, demo, lab report

Procedures

Selected components
Designed circuit structure
Designed lead compensator based on given transfer function
Built Simulink model and simulated step response
Built physical circuit and obtained step response
Adjusted component values to optimize circuit: lower overshoot, decrease settling time

Results

Overall, the circuit worked as intended, but was very slow. This meant that the controller was only able to function at a very low frequency. It is possible that this was due to the fact that a single-supply op-amp was used.

Rise time: ~2s
Settling time: ~7.5s
Percent overshoot: 23%

It should be noted that due to technical issues with the oscilloscope probes, the amplitude shown are ~10x the actual value.

Future Work

Though this analog circuit design fulfilled its overall purpose of implementing a double integrator plant, as well as a lead compensator to control the unstable double integrator signal, the slow speed of its response was a major deficiency, limiting the frequencies at which the circuit can serve its function. In future design iterations, changing from the use of single-supply op amps to dual-supply op amps could be a significant step towards improving the performance of the circuit.