Page 134 - Toucpad robotics C11

Applications
Best suited for tasks in very stable, predictable environments where the exact relationship between input and output is
known and constant.

Example
A toaster: You set a timer for 2 minutes. The toaster heats for 2 minutes regardless of how well the bread is toasted
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(e.g., if the bread was already partially toasted, or if the voltage fluctuated).
A simple traffic light system: It operates on a fixed timer sequence, regardless of traffic density.
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A basic stepper motor: If commanded to move 10 steps, it assumes it has moved 10 steps, without a sensor to
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confirm its exact position.

Closed-Loop Control Systems (Feedback Control Systems)
Description

In a closed-loop system, the control action depends on the output. The system continuously measures the actual output
using sensors and compares it with the desired output. Any difference (error) is used by the controller to adjust the input
to the actuators, thereby correcting the robot’s behaviour.

Working Principle

Command Controller Actuator Robot Action (Output) Sensor (measures Output) Feedback to Controller
(compares with Command). This forms a continuous loop.

Characteristics
High Accuracy and Precision: Can achieve and maintain desired positions or speeds very accurately by continuously
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correcting errors.
Robustness to Disturbances: Can compensate for external disturbances (like friction, changing loads, unexpected
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forces) or internal variations (like motor wear).
Adaptability: Can adapt to changing environmental conditions.
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More Complex Design: Requires sensors, a more sophisticated controller, and careful tuning.
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Applications

Essential for any robotic task requiring precision, stability, safety, and adaptability to real-world conditions.

Example
An air conditioner with a thermostat: You set the desired temperature (command). The thermostat (sensor)
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measures the actual room temperature (output). If it’s too high, the air conditioner (actuator) turns on until the
desired temperature is reached.
A robot arm precisely placing an object: An encoder on each joint measures its actual angle. The controller compares
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this to the desired angle. If there’s a difference, it adjusts the motor’s power until the correct angle is achieved.
A self-balancing robot: It constantly uses gyroscopes and accelerometers to measure its tilt (output). If it starts to
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lean, the controller commands the motors to adjust wheel speed to push itself back to an upright position.
Essential Control Algorithms (Proportional-Integral-Derivative - PID Control)
Within closed-loop systems, various algorithms determine how the controller calculates corrective actions. One of the
most common and versatile is the Proportional-Integral-Derivative (PID) controller.

Concept
A PID controller calculates a control output based on three factors related to the error (the difference between the desired
value and the measured value):

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