Issue
110, September 1999
Internet
Control
by
Jacob Apkarian
If you’re looking for a systematic
approach to designing and evaluating control system
performance, check out these CAD tools. They take
Jacob from making a mathematical model of his system
right down to generating and implementing code.
Start
• Model Derivation
• Linearization • Control-System
Design • Simulation
•
Coding •
Configurations•
Implementation •
Tuning and Results •
Ready for Takeoff •
Software
and Sources •
Equations PDF
The development of the fast PC, design software, and the affiliated Internet
technology have significantly improved the design cycles
in control system design and implementation.
In this article,
I describe the various tools available that can take
you from concept to real-time remote controller implementation,
tuning, and monitoring within a few hours.
The example
I use here is the 3DOF (degree of freedom) helicopter
experiment shown in Figure 1. The 3DOF helicopter consists
of a base on which a long arm is mounted. The arm carries
the helicopter body on one end and a counterweight on
the other.
Figure
1—The helicopter model consists
of two motors driving two propellers mounted on
a frame that can freely pitch. The frame is mounted
on a long arm with a counterbalance. The entire
arm can pivot and elevate, resulting in three
degrees of freedom of movement.
|
The arm can
tilt on an elevation axis as well as swivel on a vertical
(travel) axis. Quadrature optical encoders mounted on
these axes measure the elevation and travel of the arm.
The helicopter body is mounted at the end of the arm.
The helicopter
body is free to pitch about the pitch axis. The pitch
angle is measured via a third encoder.
Two motors
with propellers mounted on the helicopter body can generate
a force proportional to the voltage applied to the motors.
The force generated by the propellers causes the helicopter
body to lift off the ground.
The purpose
of the counterweight is to reduce the power requirements
on the motors. The counterweight is adjusted such that
the effective mass of the body is approximately 70 g.
All electrical
signals to and from the arm are transmitted via a slipring
with eight contacts. This setup eliminates the possibility
of tangled wires and reduces the amount of friction
and loading about the moving axes.
The purpose
of the exercise is to design a controller that enables
you to command the helicopter body to a desired elevation
and a desired travel position. So, I want to describe
a systematic approach to designing and evaluating control-system
performance using available CAD tools.
