Page 135 - Toucpad robotics C11

Proportional (P) Term: This term generates a control output that is proportional to the current error.
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∑ Effect: The larger the error, the stronger the immediate corrective action. It helps to quickly reduce the error.
∑ Drawback: Can lead to oscillations (overshooting the target and then undershooting) or a persistent
“steady-state error” (not quite reaching the target perfectly).
Integral (I) Term: This term sums up the past errors over time.
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∑ Effect: It helps to eliminate steady-state errors. If a small error persists for a long time, the Integral term will
gradually increase the control output until the error becomes zero.
∑ Drawback: Can make the system slow to respond and prone to “wind-up” if not properly managed.
Derivative (D) Term: This term considers the rate of change of the error (how fast the error is increasing or decreasing).
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∑ Effect: It acts as a “damper” or “predictor,” helping to reduce overshoot and oscillations by anticipating future
changes. If the robot is approaching the target too quickly, the Derivative term applies a braking action.
∑ Drawback: Highly sensitive to noise in sensor readings, which can cause erratic movements if not filtered.

How it Works (Combined)
The PID controller calculates the final control signal by summing up the outputs from the Proportional, Integral, and
Derivative terms, each weighted by a specific “gain” (a numerical factor).
Control Output = (Proportional Gain × Current Error) + (Integral Gain × Sum of Past Errors) + (Derivative Gain × Rate
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of Change of Error)
Tuning

The “gains” (weights) for P, I, and D terms need to be carefully “tuned” for each specific robot and task. Incorrect tuning
can lead to instability, slow response, or oscillations. This tuning process often involves a mix of mathematical analysis,
simulation, and trial-and-error.

Applications
PID controllers are widely used in robotics for:
Motor Speed Control: Maintaining a constant motor speed despite varying loads.
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Position Control: Moving a robotic arm or a mobile robot to an exact desired position.
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Temperature Control: In processes where a robot might regulate temperature.
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Trajectory Tracking: Making a robot follow a predefined path smoothly.
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REBOOT

Answer the following Questions:

1. Why do we call actuators the “muscles” of robots?
2. What is the difference between open-loop and closed-loop systems?
3. Why is feedback important in control systems?
4. What are two uses of ultrasonic sensors?

5. How does PWM help in controlling a motor?

Ensuring Accurate, Efficient, and Safe Robot Performance
Control systems are fundamental to achieving these performance metrics:

Accuracy and Precision
How: Closed-loop feedback (especially with PID control) constantly measures the robot’s actual position/speed and
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compares it to the desired. Any tiny deviation is immediately corrected. High-resolution sensors provide the accurate
feedback needed.
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Electrical and Control Systems