# Session 3

Electronics - Devices

Nov 2, 2013 (4 years and 6 months ago)

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Robotics Intensive:

Day 3

Gui

Cavalcanti

1/17/2012

Class Goals

1.
Discuss open loop vs. closed loop control

2.
Discuss PID

3.
Review control project goals

4.
Work on control systems

5.
Demo control systems!

Open Loop vs. Closed Loop Control

Open Loop Control

Issuing commands based on how you
think a system will react, without taking
into consideration how it is actually
reacting

Common examples:

Sprinkler Systems

Washing Machines

3pi spelling your name

Open Loop Pitfalls

Easy to develop, and thus easy to assume
it’s a good solution

You have no idea what’s actually
happening, or even if the robot is
successful

Closed Loop Control

Issuing commands based on both how you think
a system will react and the current state of the
system

Common examples

Aircraft Autopilot

Car Cruise Control

3pi following a line

Cruise Control

System Parts:

Microcontroller

Speed Sensor

Engine Control Actuator

Decision
-
Making:

Microcontroller says “I want 50 MPH”

Speed Sensor says “We’re driving 45 MPH”

Microcontroller says “Actuator, make us go
faster”

Cruise Control

50 mph

45 mph

5 mph

TOO
SLOW!

GO
FASTER!

Increase
Throttle

Repeat again and again.

PID Control

PID Control

Most common type of closed loop control,
commonly used in robotics

PID:

Proportional

Integral

Derivative

What you control around
matters!

Proportional Control

Equivalent to a big spring.

Amount system responds is proportional
to how large the error is.

Integral Control

Equivalent to filling a bucket over time.

Amount system responds is proportional
to how long the error has existed.

Derivative Control

Equivalent to running through water.

Amount system responds is proportional
to how fast the system is moving.

Controls Project Goals

The Mission

Project Description

1.
Implement the basic line following
algorithm from the
mbed

Cookbook.

2.
Implement the PID line following
algorithm from the
mbed

Cookbook.

3.
Demonstrate identification of and use of
intersections.

4.
Demonstrate travel to every branch of the
map.

Bonus Points

Fastest time

Ability to travel to a specific intersection

Ability to travel to a specific intersection
by more than one route

Demonstrate (software
-
based) object
detection

Work on demos!