Actuator

Actuators are the output devices of a robotic system. While sensors gather information about the environment, actuators act upon it. The choice of actuator significantly impacts a robot's speed, force, precision, and energy efficiency. Main types of actuators: 1. Electric actuators (most common in modern robotics): - DC motors: Simple, speed-controllable via PWM - 

Servo motors: Position-controlled, feedback via encoder - 

Stepper motors: Precise angular steps without feedback - Linear actuators: Convert rotation to linear motion 2. Hydraulic actuators: - Use pressurized fluid to generate high force - Common in heavy industrial robots and construction equipment - Disadvantage: Leakage risk, complex plumbing 3. Pneumatic actuators: - Use compressed air - Fast, lightweight, but less precise - Common in pick-and-place robots 4. Smart / novel actuators: - Shape Memory Alloys (SMA): Contract when heated - Piezoelectric actuators: Nanometer-level precision - Soft pneumatic actuators: Used in soft robotics Key performance metrics: - Torque or force output (Nm or N) - Speed (RPM or m/s) - Backdrivability (can the output move the input?) - Power-to-weight ratio Practical example: A robotic gripper uses a servo motor actuator. The controller sends a PWM signal specifying a target angle; the servo's internal feedback loop adjusts the motor until the horn reaches that exact position, closing the gripper around an object. In legged robots like Boston Dynamics' Spot, actuators must be both powerful and backdrivable to absorb impacts and maintain balance on uneven terrain.