Robotics Motors - Basics

Motors are the most common actuator in the robotics world, providing rotational movement that can be or not transformed in lineal movement by using several mechanic elements, like gears. They are typically used with wheels, but can be also used with other effectors.

They work by converting electricity into mechanical energy, by using magnets, loops of wire and electric current. The current has to work in the appropriate voltage, or it wil not provide enough power or will make the motor to break sooner if it’s too high. The current that is draw is proportional to the work that is done.

The amount of power is proportional to:

• Torque: rotational force.
• Rotational velocity.

Gearing

Gearing is a mechanism that is used to change the speed and torque of motors. The design and quality of the gear is what affects the error in the gear movement, and also to the energy wasted in the mechanism.

• A small to large gear reduces the speed but increases the torque.
• A large to small gear reduces the torque but increases the speed.

DC and Servo motors

DC Motors are motors that move continuously in one direction.

A servo motor is a DC motor that can move to a particular position. They use gear reduction and a position sensor to determine the position by using an electric circuit. The electric signal that the servo receives is used to determine the amount of turn that is needed, creating a waveform where the duration of the pulse determines the movement. The width of the pulse is what determines the movement, so it is needed to be very precise to reduce the amount of error.

Rotation measurement

If we want to measure the rotation of the motor, we can use an infra-red sensor to measure both the amount of rotation and the direction, using shaft encoders. 20210528204840

Notes References

20210514183815 INDEX - Robotics

20210514185045 Robotic Effectors and Actuators - Basics

20210528204840 Infra-red sensors are used in motors as shaft encoders to keep track of rotation

References