Collaborative Robot Arm Control System

Robotics Team Project

Overview

Team project developing a control system for a 6-DOF collaborative robot arm with force sensing and safety features.

Technologies Used

  • ROS2
  • C++
  • Python
  • Gazebo
  • MoveIt
  • Force/Torque Sensors

Links

Project Overview

As part of a collaborative team effort, we developed a comprehensive control system for a 6-DOF (six degrees of freedom) robotic arm designed for safe human-robot collaboration. The project focused on implementing advanced control algorithms, safety features, and intuitive interfaces for industrial applications.

Team Structure and My Role

As the Controls Lead, I was responsible for:

  • Designing and implementing the motion control algorithms
  • Integrating force/torque sensors for compliant control
  • Developing the trajectory planning system
  • Coordinating with team members on system integration

Key Features

  • Collision Detection: Real-time monitoring and collision avoidance
  • Force Control: Compliant motion using force/torque feedback
  • Path Planning: MoveIt integration for motion planning
  • Safety Systems: Emergency stop and speed limiting
  • Simulation: Gazebo integration for testing before deployment

Technical Implementation

Control Architecture

We implemented a hierarchical control system:

  1. Task Level: High-level task planning and coordination
  2. Motion Level: Trajectory generation and path planning
  3. Control Level: Joint-level servo control with force feedback
  4. Safety Level: Real-time monitoring and emergency response

Motion Control

Developed custom controllers for:

  • Position Control: PID controllers for each joint
  • Impedance Control: Variable stiffness for safe interaction
  • Hybrid Force-Position Control: Simultaneous position and force control

Integration with ROS2

The system is built on ROS2, providing:

  • Real-time communication between components
  • Distributed processing across multiple computers
  • Hardware abstraction for easy robot swapping
  • Comprehensive logging and diagnostics

Simulation and Testing

Before deployment on physical hardware, we extensively tested the system in simulation:

  • Created accurate robot model in URDF/SDF
  • Simulated force sensors and contact dynamics
  • Tested safety features in various scenarios
  • Validated motion planning algorithms

Safety Features

Safety was paramount in this collaborative robot design:

  • Speed Monitoring: Automatic speed reduction near humans
  • Force Limiting: Maximum force constraints to prevent injury
  • Safe Zones: Virtual barriers around the workspace
  • Emergency Stop: Multiple stop buttons and software triggers
  • Collision Detection: Immediate stop upon unexpected contact

Real-world Applications

The robot has been successfully deployed for:

  • Assembly tasks in manufacturing
  • Pick-and-place operations
  • Quality inspection
  • Human-robot collaborative assembly

Performance Results

  • Positioning Accuracy: ±0.5mm repeatability
  • Force Control: ±0.5N force accuracy
  • Cycle Time: 15% faster than baseline system
  • Safety: Zero safety incidents in 6 months of operation

Team Collaboration

This project required extensive collaboration:

  • Weekly team meetings and sprint planning
  • Code reviews and pair programming
  • Integrated testing sessions
  • Documentation and knowledge sharing

Challenges and Solutions

Challenge: Achieving smooth motion with force feedback Solution: Implemented advanced filtering and predictive algorithms

Challenge: Real-time safety monitoring Solution: Dedicated safety processor with hard real-time guarantees

Challenge: Integration of diverse hardware components Solution: Standardized interfaces and comprehensive testing framework

Future Enhancements

  • Machine learning for improved trajectory optimization
  • Computer vision integration for adaptive grasping
  • Multi-arm coordination for complex tasks
  • Remote operation capabilities

Acknowledgments

This project was a true team effort. Special thanks to my team members for their dedication and expertise in their respective areas.

Team Members

  • Alejandro Arteaga (Controls Lead)
  • Sarah Johnson (Hardware Integration)
  • Michael Chen (Computer Vision)
  • Emily Rodriguez (Safety Systems)