5-DOF robotic manipulator that detects, picks up and shoots a ping-pong ball into a hole
The 5-DOF Robotic Manipulator Project was the final project for MECH 440 - Robotics I at North Central College, where students applied their knowledge of kinematics, MATLAB simulations, and robotic path/trajectory planning to optimize and automate a robotic system.
The manipulator was preassembled before the project began, meaning our primary tasks were troubleshooting mechanical and electrical connections, performing kinematic calculations, developing MATLAB simulations, and programming the robot using Arduino. Unlike other aspects of robotic design, the dynamics of the system were pre-defined by the professor, so our focus was on ensuring the kinematic accuracy and functional performance of the manipulator.
The objective was to automate the pickup and placement of a ping-pong ball, with an additional mechanism to detect and shoot the ball into a target hole. Through troubleshooting, iterative optimization, and integration of ultrasonic sensors, PWM motor control, and automated decision-making, we developed a fully functional robotic system that outperformed other teams in the class.
Our team’s efforts led to a 100% success rate in ball placement and shooting in (20/20 tries), achieving first place in the class competition and earning the "Best Robotics Project - Fall 2024" award.
Once the project was introduced, our first step was to strategically assign tasks based on each team member's strengths and experience. Since the 5-DOF robotic manipulator was preassembled, our focus was on troubleshooting, programming, kinematic analysis, and automation.
To ensure efficiency, we met after class to discuss our individual skill sets and how we could contribute to different aspects of the project. We divided responsibilities as follows:
By clearly defining roles early on, we streamlined the workflow and ensured that each aspect of the project was covered, which I believe was a key step that helped us to be successful on this project. Our next step was to test and troubleshoot the manipulator's hardware and connections, which became the first major challenge we had to overcome.
Before we could begin programming and optimizing the robotic manipulator, we first had to troubleshoot and resolve hardware issues. Since the manipulator was preassembled, we expected it to function correctly, but upon testing, we discovered multiple challenges that needed to be addressed:
To resolve these issues, we systematically:
Once the hardware was functional, the next step was to map out each joint and the end effector, allowing us to define and control movement sequences accurately.
With the mechanical and electrical setup complete, we:
At this stage, the manipulator was successfully moving to defined positions, but was not yet optmized and would often fail to grab the ball properly (shown in video below). However, we were ready to proceed with kinematic modeling and simulation validation.
With the robotic manipulator fully functional after troubleshooting, the next step was to develop accurate kinematic models and validate them through simulations. Since the system was preassembled, we needed to ensure that all joint movements were mathematically correct and that the end effector followed the desired trajectory.
To control the manipulator accurately, we:
Once the basic kinematic models were established, we:
To validate our kinematic solutions, we:
With the kinematic models and simulations validated, we shifted our focus to enhancing the physical system by integrating additional hardware components to improve automation and functionality.
Although the robotic manipulator was preassembled, we made key modifications to enhance its performance, including:
To make the robotic manipulator more autonomous, we integrated ultrasonic sensors at two key locations:
At this stage, we implemented Pulse Width Modulation (PWM) control for the servo motors, allowing us to:
Final Arduino code is attached to the bottom of this post.
By modifying the hardware, integrating sensors, and refining motor control, we significantly improved the manipulator’s automation capabilities, preparing it for final testing and optimization.
The video below shows the manipulator succesfully completing all the movements(but without the ultrasonic sensors):
After completing the mechanical modifications, sensor integration, and programming, we conducted extensive testing and performance evaluations to ensure the robotic manipulator operated as intended.
The final version of our robotic manipulator successfully completed the entire automated sequence:
✅ Detecting the ball at the pickup location (ultrasonic sensor activation)
✅ Picking up the ball using precise servo-controlled movements
✅ Moving to the intermediate position for a smooth transition
✅ Placing the ball at the designated drop-off location
✅ Detecting the ball at the drop-off using the second ultrasonic sensor
✅ Kicking the ball into the hole with the ball-shooting mechanism
Through rigorous testing, we refined the sensor response times, adjusted motor speeds, and fine-tuned position accuracy to achieve a highly consistent and efficient system.
The video below showcases the final robotic manipulator system successfully completing all movements, demonstrating the smooth operation and efficiency of our design.
The 5-DOF Robotic Manipulator Project was a challenging yet rewarding experience that strengthened our understanding of robotic automation, kinematics, and system integration. Through troubleshooting, coding, sensor integration, and MATLAB simulations, we transformed a preassembled manipulator into an autonomous system capable of efficiently completing a complex task.
The final result was an automated system that performed very well, earning us the "Best Robotics Project - Fall 2024" award. This project reinforced our ability to integrate engineering concepts into a real-world application, further preparing us for careers in robotics, automation, and mechanical design.
A special thank you to North Central College for providing the necessary components, tools, and facilities that made this project possible.
Final Arduino Code:
#include <Adafruit_PWMServoDriver.h>
// Initialize the PCA9685 board with the default I2C address (0x40)
Adafruit_PWMServoDriver board1 = Adafruit_PWMServoDriver(0x40);
// Define minimum and maximum pulse lengths for the servos
#define SERVOMIN 125 // Minimum pulse length count (out of 4096)
#define SERVOMAX 625 // Maximum pulse length count (out of 4096)
// Ultrasonic sensor pins
const int trigPin = 9;
const int echoPin = 10;
const int trigPinPickup = 11; // Trig pin for second ultrasonic sensor
const int echoPinPickup = 12; // Echo pin for second ultrasonic sensor
// Function to convert an angle (0-180) into the corresponding PWM pulse
int angleToPulse(int ang) {
int pulse = map(ang, 0, 180, SERVOMIN, SERVOMAX); // Map angle 0-180 to pulse width
return pulse;
}
// Function to calculate distance using ultrasonic sensor
float getDistance(int trigPin, int echoPin) {
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);
long duration = pulseIn(echoPin, HIGH);
float distance = duration * 0.034 / 2; // Convert duration to distance in cm
return distance;
}
void setup() {
Serial.begin(9600);
Serial.println("6-Servo Robotic Arm Test!");
// Ultrasonic sensor setup
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
pinMode(trigPinPickup, OUTPUT); // Second ultrasonic sensor
pinMode(echoPinPickup, INPUT); // Second ultrasonic sensor
board1.begin();
board1.setPWMFreq(60); // Set frequency to 60 Hz for the servos
}
// Channels for each servo
#define theta1 0 // BASE_SERVO_CHANNEL
#define theta2 1 // LIFT_SERVO_CHANNEL
#define theta3 2 // ROTATE_SERVO_CHANNEL
#define theta4 3 // BEND_SERVO_CHANNEL
#define theta5 4 // END_EFFECTOR_ROTATE_CHANNEL
#define EE_ANGLE 5 // CLAW_SERVO_CHANNEL
#define kickAngle 6 // KICK SERVO_CHANNEL
// Function to move servo smoothly by incrementing PWM pulse
void moveServoSmoothPWM(int channel, int startPulse, int endPulse, int increment, int stepDelay) {
if (startPulse < endPulse) {
for (int pulse = startPulse; pulse <= endPulse; pulse += increment) {
board1.setPWM(channel, 0, pulse);
delay(stepDelay); // Small delay to control speed
}
} else {
for (int pulse = startPulse; pulse >= endPulse; pulse -= increment) {
board1.setPWM(channel, 0, pulse);
delay(stepDelay); // Small delay to control speed
}
}
}
void loop() {
//INITIAL POSITION
//
delay(500);
moveServoSmoothPWM(theta2, angleToPulse(140), angleToPulse(115), 1, 20);
delay(500);
moveServoSmoothPWM(theta3, angleToPulse(140), angleToPulse(140), 1, 20);
moveServoSmoothPWM(theta4, angleToPulse(140), angleToPulse(130), 1, 20);
moveServoSmoothPWM(theta1, angleToPulse(145), angleToPulse(145), 1, 20);
moveServoSmoothPWM(theta5, angleToPulse(166), angleToPulse(166), 1, 20);
moveServoSmoothPWM(EE_ANGLE, angleToPulse(50), angleToPulse(50), 1, 20);
delay(500);
// // Wait until a ball is detected at the pickup location
// Serial.println("Waiting for ball at the pickup location...");
// float pickupDistance = getDistance(trigPinPickup, echoPinPickup);
//
while (true) { // Infinite loop to wait for the ball
float distance = getDistance(trigPinPickup, echoPinPickup);
Serial.print("Distance: ");
Serial.print(distance);
Serial.println(" cm");
if (distance <= 7) { // If the ball is detected within 6 cm
// Ball detected, proceed with the pickup sequence
Serial.println("Ball detected at the pickup location. Starting pickup sequence.");
break; // Exit the loop once the ball is detected
} else {
Serial.println("No ball detected. Waiting...");
delay(500); // Wait before checking again to avoid excessive CPU usage
}
}
//
delay(500);
// PICKUP POSITION (TOP1)
moveServoSmoothPWM(theta2, angleToPulse(115), angleToPulse(115), 1, 20);
moveServoSmoothPWM(theta3, angleToPulse(140), angleToPulse(140), 1, 20);
moveServoSmoothPWM(theta4, angleToPulse(140), angleToPulse(140), 1, 20);
moveServoSmoothPWM(theta1, angleToPulse(180), angleToPulse(180), 1, 20);
moveServoSmoothPWM(theta5, angleToPulse(166), angleToPulse(166), 1, 20);
moveServoSmoothPWM(EE_ANGLE, angleToPulse(50), angleToPulse(50), 1, 20);
delay(500);
//PICKUP POSITION (BOTTOM)
//
// Move rotate servo from 115 to 104 degrees, with PWM increment of 1 and 20ms delay
moveServoSmoothPWM(theta2, angleToPulse(115), angleToPulse(104), 1, 10);
delay(150);
moveServoSmoothPWM(theta3, angleToPulse(140), angleToPulse(140), 1, 20);
moveServoSmoothPWM(theta4, angleToPulse(140), angleToPulse(140), 1, 20);
moveServoSmoothPWM(theta1, angleToPulse(180), angleToPulse(180), 1, 20);
moveServoSmoothPWM(theta5, angleToPulse(166), angleToPulse(166), 1, 20);
moveServoSmoothPWM(EE_ANGLE, angleToPulse(50), angleToPulse(50), 1, 20);
//CLOSE THE END-EFFECTOR
moveServoSmoothPWM(EE_ANGLE, angleToPulse(85), angleToPulse(85), 1, 20);
delay(800);
//PICKUP POSITION (TOP2)
//
moveServoSmoothPWM(theta2, angleToPulse(115), angleToPulse(115), 1, 20);
moveServoSmoothPWM(theta3, angleToPulse(140), angleToPulse(140), 1, 20);
moveServoSmoothPWM(theta4, angleToPulse(140), angleToPulse(140), 1, 20);
moveServoSmoothPWM(theta1, angleToPulse(180), angleToPulse(180), 1, 20);
moveServoSmoothPWM(theta5, angleToPulse(166), angleToPulse(166), 1, 20);
moveServoSmoothPWM(EE_ANGLE, angleToPulse(85), angleToPulse(85), 1, 20);
delay(500);
//INTERMEDIATE POSITION
//
moveServoSmoothPWM(theta2, angleToPulse(140), angleToPulse(140), 1, 20);
moveServoSmoothPWM(theta3, angleToPulse(140), angleToPulse(140), 1, 20);
moveServoSmoothPWM(theta4, angleToPulse(105), angleToPulse(105), 1, 20);
moveServoSmoothPWM(theta1, angleToPulse(180), angleToPulse(80), 1, 5);
moveServoSmoothPWM(theta5, angleToPulse(166), angleToPulse(166), 1, 20);
moveServoSmoothPWM(EE_ANGLE, angleToPulse(85), angleToPulse(85), 1, 20);
//DROPOFF LOCATION (TOP)
//
// Move rotate servo from 105 to 140 degrees, with PWM increment of 1 and 20ms delay
moveServoSmoothPWM(theta4, angleToPulse(105), angleToPulse(140), 1, 20);
// Move rotate servo from 140 to 115 degrees, with PWM increment of 1 and 20ms delay
moveServoSmoothPWM(theta2, angleToPulse(140), angleToPulse(115), 1, 20);
moveServoSmoothPWM(theta3, angleToPulse(140), angleToPulse(140), 1, 20);
// Move base servo from 80 to 108 degrees, with PWM increment of 1 and 20ms delay
moveServoSmoothPWM(theta1, angleToPulse(80), angleToPulse(108), 1, 20);
moveServoSmoothPWM(theta5, angleToPulse(166), angleToPulse(166), 1, 20);
moveServoSmoothPWM(EE_ANGLE, angleToPulse(85), angleToPulse(85), 1, 20);
//DROPOFF POSITION (BOTTOM)
//
// Move rotate servo from 115 to 104 degrees, with PWM increment of 1 and 20ms delay
moveServoSmoothPWM(theta2, angleToPulse(115), angleToPulse(104), 1, 15);
delay(100);
moveServoSmoothPWM(theta3, angleToPulse(140), angleToPulse(140), 1, 20);
moveServoSmoothPWM(theta4, angleToPulse(140), angleToPulse(140), 1, 20);
moveServoSmoothPWM(theta1, angleToPulse(108), angleToPulse(108), 1, 20);
moveServoSmoothPWM(theta5, angleToPulse(166), angleToPulse(166), 1, 20);
moveServoSmoothPWM(EE_ANGLE, angleToPulse(50), angleToPulse(50), 1, 20);
delay(500);
//DROPOFF LOCATION (TOP2)
//
moveServoSmoothPWM(theta4, angleToPulse(140), angleToPulse(140), 1, 20);
// Move rotate servo from 105 to 115 degrees, with PWM increment of 1 and 20ms delay
moveServoSmoothPWM(theta2, angleToPulse(105), angleToPulse(115), 1, 10);
moveServoSmoothPWM(theta3, angleToPulse(140), angleToPulse(140), 1, 20);
moveServoSmoothPWM(theta1, angleToPulse(108), angleToPulse(108), 1, 20);
moveServoSmoothPWM(theta5, angleToPulse(166), angleToPulse(166), 1, 20);
moveServoSmoothPWM(EE_ANGLE, angleToPulse(50), angleToPulse(50), 1, 20);
// PRE INITIAL POSITION
moveServoSmoothPWM(theta2, angleToPulse(115), angleToPulse(140), 1, 20);
moveServoSmoothPWM(theta3, angleToPulse(140), angleToPulse(140), 1, 20);
moveServoSmoothPWM(theta4, angleToPulse(140), angleToPulse(130), 1, 20);
moveServoSmoothPWM(theta1, angleToPulse(145), angleToPulse(145), 1, 20);
moveServoSmoothPWM(theta5, angleToPulse(166), angleToPulse(166), 1, 20);
moveServoSmoothPWM(EE_ANGLE, angleToPulse(50), angleToPulse(50), 1, 20);
delay(1000);
// Ultrasonic sensor check
Serial.println("Waiting for the ball...");
while (true) { // Infinite loop to wait for the ball
float distance = getDistance(trigPin, echoPin);
Serial.print("Distance: ");
Serial.print(distance);
Serial.println(" cm");
if (distance <= 6) { // If the ball is detected within 6 cm
Serial.println("Ball detected! Moving kick servo.");
moveServoSmoothPWM(kickAngle, angleToPulse(90), angleToPulse(180), 15, 15); // Kick action
delay(100);
moveServoSmoothPWM(kickAngle, angleToPulse(180), angleToPulse(90), 10, 15); // Return to default
delay(500);
break; // Exit the loop once the ball is detected and kicked
} else {
Serial.println("No ball detected. Waiting...");
delay(500); // Wait before checking again to avoid excessive CPU usage
}
}
}
