Build Your Own Combat Robot

300 Build Your Own Combat Robot
about half of them have lower current ratings in reverse than in forward. You will
need an ESC that has the same capabilities in forward and in reverse.
Most ESCs advertise the peak current capacity. This is a very misleading value.
It is usually a theoretical value under ideal operating conditions, and not to exceed
that value for more than one second. In reality, if the motors are drawing current
near this advertised value for more than a few seconds, you will let the “magic
smoke” out of the ESC, and it will stop working. Since sumos spend a lot of their
time pushing other robots around, the motors will be drawing near maximum current
for long periods of time. Because of this, you will need to look at the 30-second
and 5-minute current ratings of the ESC. The ideal ESC will have a 30-second
current rating greater than the stall current of the motor. Obtaining this information
usually means contacting the manufacturer. One method to obtain a little
performance improvements out of the ECS is to add a cooling fan above the heat
sinks on the ESC.
Generally, the R/C style electronic speed controllers are the easiest and most
cost-effective solution to driving the motors. These controllers can be found at
most hobby stores. Another source for electronic speed controllers is using
H-Bridge type controllers. There are many companies that sell a wide variety of
these types of controllers. One of the big differences in these controllers is that
they accept a true pulse-width modulation (PWM) signal to vary the motor speed,
which can give you better speed, braking, and direction control resolution. Many
bot builders build their own version of a high-powered speed controller using
MOSFET power transistors. Although this can be done, it is generally a difficult
task to produce a reliable controller. In the end, off-the-shelf speed controllers are
less frustrating and cost less to implement.
Advanced Sensors Because the international robot sumo class is much larger
than the mini sumo class, there’s a lot of extra room for sensors. Most international
sumo bots use more than one type of sensor. The edge-detection sensor is
still used. Some bots use more than two sets of these, and some bots even have
them on their backs to detect whether they are being pushed out to the sumo ring.
The infrared object-detector circuit is very popular, and is used on the larger sumo
bots. A new type of sensor that is used on the larger sumo bots is the range-detecting
sensor. The two most common methods used are ultrasonic sensors and infrared
range detectors.
Ultrasonic Range Detectors
Ultrasonic range detectors are becoming more popular because they are becoming
more widely available. They work by measuring the time of flight from a sound
signal being reflected off an object. The object’s distance is computed by multiplying
the measured time by the speed of sound in the current air conditions. For robotic
sumo applications, any returned signal outside 5 feet can be ignored because