Precision Ball Control Platform
Senior Capstone Project
Summary :
The Precision Ball Control Platform is a three-degree-of-freedom Stewart platform designed to precisely manipulate a ball’s movement using real-time computer vision and PID control. The system tracks the ball’s position with a camera, calculates necessary platform adjustments using inverse kinematics, and actuates three linear actuators to control tilt.
A PID controller ensures smooth and stable ball movement, overcoming challenges like system latency, actuation lag, and dynamic stability. This project showcases expertise in mechanical design, control systems, and mechatronics, integrating kinematics, automation, and embedded systems to achieve high-precision motion control.
Project Overview
What?
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Design and fabricate a dynamic system that balances a ball on a platform with 3DOF.
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Uses linear actuators to achieve control of the platforms tilt.
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Fully autonomous control of the balls position.
How?
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Designed in SolidWorks applied DFA.
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Built for rapid prototyping with off-the-shelf components in critical areas to ensure reliability.
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Designed a PID Control algorithm using Matlab Control System toolbox and implemented on Arduino.
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Derived the system's dynamic mathematical model and inverse kinematics.
Results
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The design fulfilled its purpose achieving a ball settling time of 8.6s demonstrating efficient stabilization.
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Zero-order hold method with a 0.2-second sampling time successfully achieved discretization for microcontroller implementation while maintaining performance.
Mechanical Model
Specifications
Development Stages
1) Concept & Mathematical Modeling
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Defined system requirements: three actuators with RPS (Revolute-Prismatic-Spherical) joints to manipulate the platform.
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Derived the dynamic model of the ball’s motion using the Euler-Lagrange method to analyze system stability.
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Converted the continuous model into a discrete domain for digital PID control implementation
2) Inverse Kinematics & Actuator Design
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Developed the inverse kinematics equations to determine actuator lengths based on platform tilt requirements.
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Designed the actuator assembly, ensuring stability and precision in motion.
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Considered workspace constraints to optimize the platform’s movement range.
3) Control System Implementation
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Control System Implementation
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Implemented a PID control system to adjust platform tilt based on real-time feedback.
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Tuned PID parameters, balancing response time and stability, noting that derivative gain (Kd) added excessive sensitivity.
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Converted the desired platform angles into actuator height adjustments.
4) Computer Vision Integration
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Positioned a camera above the platform (noting its x-y coordinate inversion).
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Used real-time image processing to track ball position and provide feedback to the controller.
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Implemented coordinate transformations, factoring in platform offsets from pixel coordinate (xOffset = 158 mm, yOffset = 102 mm).
5) Mechanical Fabrication & Testing
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Constructed the platform, ensuring accurate actuator placement for smooth motion.
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Conducted stability tests, adjusting PID parameters for optimal response.
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Validated system accuracy, testing real-time ball trajectory correction.