🤖 KUKA LBR iiwa – Null-Space Obstacle Avoidance

🧠 Overview

This project focuses on controlling a 7-DOF redundant manipulator (KUKA LBR iiwa) to track Cartesian trajectories while avoiding obstacles in real time.

The main idea is simple but powerful:

• Use CLIK (Closed-Loop Inverse Kinematics) for tracking
• Exploit redundancy to handle obstacle avoidance in the null space

The system is implemented in MATLAB and simulated in CoppeliaSim via the ZeroMQ Remote API.

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⚙️ How it works (intuition first)

Check the diagram above 👆

Pipeline:

1. A Cartesian trajectory is defined
2. A PI controller generates desired velocity
3. CLIK maps it to joint velocities
4. A secondary objective handles obstacle avoidance

👉 Key idea:
Obstacle avoidance is handled in the null space, so it does not interfere with the main tracking task.

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🧮 Control Law

[ \dot{q} = J^\dagger v + (I - J^\dagger J) z ]

• First term → tracking
• Second term → null-space action (avoidance)

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🎯 Primary Task — Tracking

• Cartesian PI controller
• Waypoint tracking
• Velocity saturation

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🚧 Secondary Task — Obstacle Avoidance

Potential Fields (Khatib)

• Repulsive action from obstacles

Vortex Component

• Adds tangential motion
• Prevents local minima

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🛡️ Robustness Strategies

• Damped Least Squares → stable near singularities
• Task relaxation → reduces tracking priority near obstacles
• Anti-stall mechanism → helps escape stuck situations

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📊 Results

• Stable tracking
• No collisions
• Smooth motion

Metrics:

• Cartesian error
• Minimum distance
• Joint velocities

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▶️ How to Run

1. MATLAB setup

addpath('src')

2. Open CoppeliaSim

Load:

sim/kuka_scene.ttt

⚠️ Do NOT press Play manually.

3. Run

run('src/main_avoidance.m')

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📂 Repository Structure

KUKA-iiwa-Obstacle-Avoidance/
├── src/                      # MATLAB source code (core logic)
│   ├── main_avoidance.m      # Main script: runs simulation and control loop
│   ├── controller_nullspace.m # Implements CLIK + null-space control law
│   ├── RemoteAPIClient.m     # Interface with CoppeliaSim (ZeroMQ)
│   └── cbor.m                # Serialization utility for communication
│
├── model/                    # Robot model definition
│   ├── kukanomesh.urdf       # URDF used in MATLAB
│   └── meshes/               # STL mesh files for visualization
│
├── sim/                      # Simulation environment
│   └── kuka_scene.ttt        # CoppeliaSim scene (robot + obstacles)
│
├── control_scheme.png        # Controller block diagram (this README)
├── kuka_avoidance.gif        # Demo of the robot behavior
├── README.md                 # Documentation
└── LICENSE                   # MIT License

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👤 Author

Giorgio De Santis
MSc AI & Robotics

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📄 License

MIT License