Motors

Most mobile robots have actuators that rotate continuously – often these drive wheels.

As a motor rotates, so the wheel rotates and the robot moves. Many robots have two wheels, one on either side. If one wheel goes forward and the other back, the robot turns.

Such wheeled robots work well on smooth surfaces.

For covering uneven terrain, however, tracks may be used.

Types of motor

There are lots of motors to choose from but not all are appropriate. For example, a tiny pager motor has a weight located off the motor axis so that when the motor spins the whole system vibrates. These are used in pagers/mobile phones – but not for robots.

There are dc motors

• You apply a voltage to them and they rotate continuously – reverse the polarity of the voltage and they rotate in the reverse direction.

• Later we will explain how feedback control is beneficial.

Stepper motors exist

• You apply a pulse and the motor turns a bit,

• Then another pulse and it turns further, etc.

There are servomotors – which have feedback control. Often motors with gears are needed, just like a bicycle has gears to help you go up hill.

Let’s consider how we actually drive motors on robots… and, as a by product, measure the actual speed of the robot.