README.md

---
tags:
- robotics
- trajectory-generation
- diffusion-model
- navigation
- human-like-motion
- ddpm
library_name: pytorch
pipeline_tag: reinforcement-learning
license: mit
---

# 🤖🚶 Human-Like Robot Navigation Trajectory Generator

A **DDPM (Denoising Diffusion Probabilistic Model)** that generates human-like 2D navigation trajectories for robots.

## What It Does

Given a robot's current state (position + velocity) and a goal, this model generates future waypoints that mimic human walking — smooth curves, natural speed changes, and obstacle-aware paths.

```
Input:  [x, y, vx, vy] + [goal_x, goal_y]
  ↓ DDPM Reverse Diffusion (100 steps)
  ↓ 1D Temporal UNet + FiLM conditioning
Output: 16 future waypoints [dx, dy]
```

## Key Features

- 🚶 **Human-like paths** — smooth curves, not robotic straight lines
- ⚡ **Variable speed** — acceleration, cruising, deceleration like real walking
- 🧱 **Obstacle aware** — learned from social force model training data
- 🎲 **Multi-modal** — generates diverse trajectory samples via diffusion
- 🎯 **Goal-directed** — conditions on target position

## Architecture

| Component | Details |
|-----------|---------|
| Backbone | 1D Temporal UNet ([64, 128, 256]) |
| Conditioning | FiLM (Feature-wise Linear Modulation) |
| Noise Schedule | Cosine (Improved DDPM) |
| Diffusion Steps | 100 |
| Parameters | 1,801,538 (1.8M) |
| Prediction | ε-prediction (noise) |

## Based On

- [Diffusion Policy](https://arxiv.org/abs/2303.04137) (Chi et al., RSS 2023)
- [TRACE](https://arxiv.org/abs/2304.01893) (Rempe et al., CVPR 2023)
- [Improved DDPM](https://arxiv.org/abs/2102.09672) (Nichol & Dhariwal, 2021)

## Training Data

2,000 synthetic episodes in a 20m × 20m environment with 8 obstacles:
- Social Force Model physics (Helbing & Molnar 1995)
- ~156K frames at 10 Hz
- Speed range: 0.3-2.0 m/s (avg ~1.3 m/s, matching human walking)

## Quick Start

```python
import torch, json, numpy as np

# Load
config = json.load(open('config.json'))
stats = json.load(open('normalization_stats.json'))

# Build model (copy architecture classes from this repo)
model = HumanTrajDiffusion(ad=2, sd=4, gd=2, H=16, T=100, dims=tuple(config['down_dims']))
model.load_state_dict(torch.load('model.pt', map_location='cpu'))
model.eval()

# Robot at (5,5) moving NE → goal (15,15)
state = np.array([5.0, 5.0, 0.5, 0.3])
goal = np.array([15.0, 15.0])

state_n = torch.tensor((state - stats['state_mean']) / stats['state_std'], dtype=torch.float32)
goal_n = torch.tensor((goal - stats['goal_mean']) / stats['goal_std'], dtype=torch.float32)

# Generate 5 diverse paths
trajectories = model.generate(state_n, goal_n, n=5)

# → Real coordinates
traj = trajectories.numpy() * stats['action_std'] + stats['action_mean']
positions = np.cumsum(traj, axis=1) + state[:2]
# positions.shape = (5, 16, 2) — 5 paths, 16 waypoints, (x,y)
```

## Config
```json
{
  "horizon": 16,
  "action_dim": 2,
  "state_dim": 4,
  "goal_dim": 2,
  "num_diffusion_steps": 100,
  "down_dims": [
    64,
    128,
    256
  ],
  "batch_size": 32,
  "total_steps": 8000,
  "lr": 0.0002,
  "weight_decay": 1e-05,
  "warmup_steps": 200,
  "grad_clip": 10.0,
  "eval_freq": 2000,
  "log_freq": 25,
  "hub_model_id": "precison9/human-like-robot-nav-diffusion"
}
```

## Normalization Stats
```json
{
  "state_mean": [
    9.887735366821289,
    10.40771484375,
    0.02240574173629284,
    -0.010746479965746403
  ],
  "state_std": [
    4.021646976470947,
    3.9589571952819824,
    0.7364981174468994,
    0.7464056015014648
  ],
  "action_mean": [
    0.0022544937673956156,
    -0.001080495654605329
  ],
  "action_std": [
    0.07394769042730331,
    0.07494954019784927
  ],
  "goal_mean": [
    10.106578826904297,
    10.3273344039917
  ],
  "goal_std": [
    4.950056076049805,
    5.060120582580566
  ]
}
```

## Applications
- 🤖 Mobile robot navigation
- 🎮 NPC pedestrian AI
- 🏗️ Crowd simulation
- 📊 Trajectory prediction/planning