Page 208 - Hacking Roomba

Using Roomba as chapter

an Input Device

he Roomba’s sensors are designed to sense the world in very particu-
lar ways. Unlike our own “sensors” which have a wide sensing range
Tand can be adapted for a variety of tasks, each of the Roomba’s sen-
sors are extremely limited. The limitation is partly due to cost reasons (this
is a price-sensitive consumer device after all) and partly because creating
high dynamic range durable sensors is hard. Current electronic vision sen- in this chapter
sors are low-resolution and require an enormous amount of space and com-
putation when compared to even simple organic eyes. There has yet to be Alternative uses for
invented a touch sensor that responds as accurately and complexly as skin. Roomba sensors
For now robots must make do with simple sensors that detect only a small
bit of their environment. Such sensors are custom designed for a particular Use Roomba as a
task and aren’t meant for any other. But that doesn’t mean you can’t co-opt mouse
the sensors and make them do more.
The Roomba can act as a general-purpose input device. The sensors it nor- Make a theremin
mally uses to avoid obstacles and know its world can be turned upside with Roomba
down (literally as you’ll see) and made to work as a multi-dimensional input
device for whatever you can dream up. This chapter presents a few different Turn Roomba into
examples of how to use the Roomba’s inputs in ways its designers never an alarm clock
imagined.

Ways to Use the Roomba’s Sensors

As discussed in Chapter 7, Roomba has two different classes of sensors:
internal and external. The internal sensors provide data about the internal
Roomba state: how far it has gone, how much it has rotated, battery charge
and drain, and so on. Another factor to consider is the sensor resolution.
Most sensors are a single binary value: on or off, cliff detected or not, button
pressed or not. A few Roomba sensors have greater resolution than one bit.
It turns out that all the sensors with greater resolution than a single bit,
except one (the dirt sensor), are internal sensors. Roomba needs accurate
internal knowledge about its power system, so that makes sense. For the
external sensors, it’s usually easier to design a sensor for the physical world
that unambiguously detects if a quantity is above or below a predefined
value than it is to measure that quantity precisely.