Page 130 - Toucpad robotics C11

This budget dictates the size and capacity of the battery, the type of power regulation needed, and ultimately, how long
a mobile robot can operate autonomously. Understanding these requirements is fundamental for efficient and effective
robot design.
Motors (Actuators for Movement)

Motors are typically the most power-hungry components in a robot, as they are responsible for generating mechanical
motion, especially when performing strenuous tasks. Their power consumption depends heavily on their type, size, and
the load they are moving.
Direct Current (DC) Motors

Power Consumption: Varies widely, from a few milliwatts (mW) for tiny hobby motors to hundreds of watts (W) or
u
even kilowatts (kW) for large industrial motors.
Factors Influencing Consumption:
u
∑ Size and Torque: Larger motors designed to produce more torque (turning force) consume more power. A small
motor in a toy car might draw tens of milliamperes (mA), while a motor for a heavy industrial conveyor could draw
tens of amperes (A).
∑ Load: The heavier the load the motor has to move or lift, the more current it draws, and thus the more power it
consumes. Stalled motors (when they are trying to move but cannot) draw maximum current, leading to high
power consumption and potential overheating.
∑ Speed: Power consumption generally increases with speed, as more energy is expended per unit of time to
maintain higher rotational velocities against friction and load.
∑ Efficiency: More efficient motors convert a higher percentage of electrical power into mechanical power, losing less
as heat. Brushless Direct Current motors, for instance, are generally more efficient than brushed Direct Current
motors, especially under varying loads.
Typical Range:
u
∑ Small hobby Direct Current motors (e.g., for simple educational robots): 0.1 Watts to 10 Watts (drawing tens to
hundreds of milliamperes at typical voltages like 3V to 12V).
∑ Medium-sized Direct Current motors (e.g., for robotic vacuum cleaners or mid-sized mobile robots): 10 Watts to
100 Watts (drawing a few amperes at 12V or 24V).
∑ Large industrial Direct Current motors (e.g., in heavy machinery): Hundreds of Watts to several Kilowatts.

Servo Motors

u Power Consumption: Varies significantly based on size and the torque required.
Factors Influencing Consumption:
u
∑ Size and Torque Rating: Similar to Direct Current motors, larger servo motors with higher torque capabilities
consume more power.
∑ Holding Torque: A unique characteristic of servo motors is their ability to hold a position. Even when stationary,
they consume some power to maintain their commanded position against external forces or gravity. This “holding
current” is often significantly less than their “moving current.”
∑ Movement Speed and Load: During movement, especially when accelerating or moving against a heavy load,
servo motors draw much higher current (and thus power) to achieve the commanded motion.
∑ Number of Servos: Robots with many degrees of freedom (like humanoid robots) will have many servo motors,
and their combined power consumption can be very high.
Typical Range:
u
∑ Small hobby servo motors (e.g., for robotic car steering, small robot joints): 0.5 Watts to 5 Watts (drawing tens
to hundreds of milliamperes at 5V to 7.4V).

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