Components of robots - Drives - "muscles" of robots

Drives: Drives are the “muscles” of robots. Currently, the most popular motors in drives are electric, but others are used that use chemicals or compressed air.

• DC motors: Currently, most robots use electric motors , which can be of several kinds.
• Stepper motors: As the name suggests, stepper motors do not rotate freely, like DC motors. They rotate step by step at a certain angle under the control of the controller. This allows you to do without a position sensor, since the angle at which the turn was made is known to the controller; therefore, such engines are often used in drives of many robots and CNC machines.

• Piezo motors: A modern alternative to DC motors is piezo motors, also known as ultrasonic motors. The principle of their work is quite original: tiny piezoelectric legs, vibrating at a frequency of more than 1000 times per second, cause the motor to move in a circle or a straight line. The advantages of such engines are high nanometric resolution, speed and power, which is incommensurable with their size. Piezo motors are already available commercially and are also used on some robots.
• Air muscles: Air muscles are a simple but powerful device to provide traction. When inflating with compressed air, muscles can contract up to 40% of their length. The reason for this behavior is weaving, visible from the outside, which causes the muscles to be either long and thin, or short and thick. Since the way they work is similar to biological muscles, they can be used to produce robots with muscles and a skeleton, similar to the muscles and the skeleton of animals.
• Electroactive polymers: Electroactive polymers are a type of plastic that changes shape in response to electrical stimulation. They can be designed in such a way that they can bend, stretch or contract. However, at present there are no EAPs suitable for the production of commercial robots, since all of their current samples are ineffective or fragile.
• Flexible nanotubes: This is a promising experimental technology that is in early development. The absence of defects in nanotubes allows the fiber to elastically deform by several percent. The human biceps can be replaced by a wire of such material with a diameter of 8 mm. Such compact "muscles" can help robots in the future to overtake and jump over a person.