In mechatronics, controllers are essential components that regulate the behavior of mechanical and electronic systems to achieve desired performance. They process input signals from sensors, apply control algorithms, and generate output signals to actuators, ensuring stability, precision, and efficiency. Controllers can be simple, like on-off control, or complex, such as PID (Proportional-Integral-Derivative) and adaptive controllers. They are widely used in robotics, automation, and embedded systems to optimize performance and maintain system reliability.