Section outline

  • Servo Motors – Control and Calibration

    Servo motors are the building blocks of precise robotic movement. Unlike regular DC motors, servo motors allow for accurate control over angular position, making them ideal for robotic joints such as shoulders, elbows, and wrists. In a robotic arm, each joint is typically powered by a servo motor to ensure controlled movement within a specified range.

    • How Servo Motors Work

      A servo motor contains a small DC motor, a feedback sensor (usually a potentiometer), and a control circuit. When a control signal is sent to the servo, the internal circuitry adjusts the motor’s position to match the desired angle. Most hobby-grade servos used in educational robotics rotate from 0 to 180 degrees.

      • Pulse Width Modulation (PWM): Servos are controlled using PWM signals, where the width of the pulse determines the angle.
      • Control Signal Frequency: Standard servos expect a 50 Hz signal (one pulse every 20 ms).
      • Typical Pulse Ranges: A 1 ms pulse sets the position to 0°, 1.5 ms to 90°, and 2 ms to 180°.

      Types of Servo Motors

      • Standard Servo: Provides rotation between 0°–180°, most commonly used in robotic arms.
      • Continuous Rotation Servo: Rotates freely like a DC motor, used for drive wheels, not joints.
      • High Torque Servo: Designed for heavier loads, used in industrial or advanced robotics projects.

    • Calibrating a Servo Motor

      Calibration ensures that your servo accurately reaches its target angles. An improperly centered servo can lead to unexpected arm behavior or mechanical strain.

      1. Connect the servo to the Arduino and power supply.
      2. Upload a simple sketch that sets the servo angle to 90°.
      3. Physically align the joint or arm part to the neutral position at this angle.
      4. Fix the servo horn in place and recheck movement at different angles (0°, 90°, 180°).

      Practical Tips

      • Do not force a servo beyond its range — it can get damaged.
      • Use an external power supply if controlling multiple servos.
      • Let the servo rest during extended idle periods to prevent overheating.

      With a clear understanding of servo types, control techniques, and calibration methods, you are now ready to map out how these motors will power each joint in your robotic arm and deliver accurate motion.