Building a 4-DOF Robotic Arm: TowerPro Servos, Inverse Kinematics & Joystick Control

Robotic arms form the backbone of industrial automated manufacturing. This desktop 4-DOF (Degrees of Freedom) robotic manipulator features base rotation (yaw), shoulder flexion, elbow extension, and a mechanical end-effector gripper, controlled by twin analog joysticks.

1. System Anatomy

• Base Waist Servo (MG996R / MG90S): 0° to 180° horizontal panning
• Shoulder Joint Servo (MG996R): High-torque vertical elevation
• Elbow Joint Servo (MG90S): Forward and backward reach
• End-Effector Gripper Servo (SG90): Claws open and close
• Controller: Arduino UNO with dedicated 5V 3A external servo supply rail

2. Wiring Schematic

Connect dual analog joystick potentiometers to Arduino inputs:

• Joystick 1 X-axis → Analog A0 (Base Yaw)
• Joystick 1 Y-axis → Analog A1 (Shoulder)
• Joystick 2 X-axis → Analog A2 (Elbow)
• Joystick 2 Y-axis → Analog A3 (Gripper Open/Close)

cpp
#include <Servo.h>

Servo baseServo, shoulderServo, elbowServo, gripServo;

void setup() {
  baseServo.attach(3);
  shoulderServo.attach(5);
  elbowServo.attach(6);
  gripServo.attach(9);
}

void loop() {
  int x1 = analogRead(A0);
  int y1 = analogRead(A1);
  int x2 = analogRead(A2);
  int y2 = analogRead(A3);

  baseServo.write(map(x1, 0, 1023, 0, 180));
  shoulderServo.write(map(y1, 0, 1023, 15, 165));
  elbowServo.write(map(x2, 0, 1023, 10, 170));
  gripServo.write(map(y2, 0, 1023, 0, 90));

  delay(20);
}