---
license: gemma
language:
- en
tags:
- vision-language-action
- humanoid-robotics
- telepathy
- multimodal
- robotics-control
- lora
- pytorch
base_model: lerobot/pi05_base
datasets:
- lerobot/svla_so101_pickplace
library_name: transformers
pipeline_tag: other
author: "Libo Wang"
---

# Sigma: The Key for Vision–Language–Action Models toward Telepathy

[![Model Card](https://img.shields.io/badge/HF-Sigma-orange?logo=huggingface)](https://huggingface.co/Veltraxor/Sigma)
[![Base Model](https://img.shields.io/badge/base-lerobot%2Fpi05__base-blue)](https://huggingface.co/lerobot/pi05_base)
[![Dataset](https://img.shields.io/badge/dataset-lerobot%2Fsvla__so101__pickplace-green)](https://huggingface.co/datasets/lerobot/svla_so101_pickplace)

Sigma is a **telepathy-style Vision–Language–Action (VLA) model** built on top of `lerobot/pi05_base`.  
It adds a semantic “telepathy” path and LoRA adapters that steer continuous robot control using internal **semantic memory** and **intent states**, while keeping the original π0.5 backbone weights intact and recoverable.

---

## 1. Summary

- **Base policy**: `lerobot/pi05_base` (π0.5)  
- **Author**: **Libo Wang**  
- **GPU for training**: single RTX 4090 (24GB)  
- **Data**: `lerobot/svla_so101_pickplace`  
- **Objective**:  
  Make a π0.5-style VLA **use internal semantic & intent states** to refine continuous control, rather than only imitating trajectories.

Sigma keeps the perception and control structure of π0.5, and introduces an additional pathway that:

- fuses **vision, language, and robot state** into a shared latent sequence,
- maintains a **semantic state** m_t and an **intent vector** z_intent over time,
- converts them into **telepathy factors** that modulate the policy’s action outputs as residual corrections.

---

## 2. Architecture at a Glance

Sigma can be seen as **π0.5 + telepathic head + LoRA adapters**:

- **Vision / State stream**  
  - reuse π0.5 encoders for images and robot state;  
  - add FiLM-style modulation from telepathy factors on vision tokens.

- **Language–semantic stream**  
  - take text tokens, vision tokens, and state tokens into a shared MLLM backbone;  
  - derive:
    - a **semantic memory** m_t that accumulates cross-time information,
    - an **intent vector** z_intent,
    - pooled **semantic factors** aligned with the text embedding space.

- **Action stream (three branches)**  
  - treat π0.5 outputs as **baseline**:  
    - action vector (per-step),  
    - action chunk (short horizon),  
    - action trajectory (full horizon);  
  - learn **residual actions** driven by telepathy factors on all three branches.

The resulting policy still *looks like* π0.5 from the outside (same inputs, same output types), but actions are now corrected by an internal telepathy pathway that is aware of **deep semantics and associative intent**.

---

## 3. Training Setup

### 3.1 Dataset & preprocessing

- **Upstream dataset**: `lerobot/svla_so101_pickplace`  
- **Task**: pick-and-place style manipulation with multi-frame RGB + robot state + continuous actions.

A preprocessing script (`dataset_preprocess_sigma_vla.py`) does:

- sliding-window segmentation with horizon `T = 16`,  
- filtering out windows with nearly zero action norm to remove static segments,  
- packing vision frames, robot state, and 3-scale action targets into tensor batches,  
- exporting three sharded files:

```text
storage/sigma_pickplace/shard_00000.pt
storage/sigma_pickplace/shard_00001.pt
storage/sigma_pickplace/shard_00002.pt
```

These shards are the **only** data used for Sigma training and evaluation.

### 3.2 LoRA fine-tuning (Sigma training)

Training is performed on a **single RTX 4090** using `train_sigma_telepathy_vla_lora.py`:

```bash
python train_sigma_telepathy_vla_lora.py \
  --base_model_id lerobot/pi05_base \
  --dataset_dir /workspace/storage/sigma_pickplace \
  --output_dir /workspace/storage/sigma_lora_out \
  --batch_size 4 \
  --gradient_accumulation_steps 4 \
  --max_steps 300 \
  --dtype bf16
```

Key aspects:

- freeze backbone weights from `lerobot/pi05_base`;  
- attach **LoRA** on key projections (q, k, v, o) and the telepathy heads;  
- jointly optimize:
  - **three control losses**:
    - `L_act_vec` for per-step action vectors,
    - `L_act_chk` for short-horizon chunks,
    - `L_act_trj` for full trajectories;
  - **semantic & telepathy regularizers**:
    - alignment of semantic factors with text embeddings,
    - control of telepathy factor norm `tau_l2`.

All LoRA and telepathy parameters are stored under:

```text
storage/sigma_lora_out/
  sigma_telepathy_heads.pt
  adapter_config.json
  adapter_model.bin
  ...
```

### 3.3 Telepathy-aware training logic

Two key training mechanisms are implemented inside the loss:

- **Telepathic Residual Action Focusing (TRAF)**  
  Focuses learning on *residual actions* instead of full actions, and uses **hard-sample mining** (top-k error segments) to allocate more gradient budget to difficult humanoid control windows.

- **Telepathic Semantic Alignment Curriculum (TSAC)**  
  Gradually increases the weights of:
  - semantic memory–text alignment,
  - intent–telepathy alignment,
  while maintaining action regression as the primary objective early on.  
  Late in training, Sigma is encouraged to let **internal semantic/intent structure** drive the residual corrections.

---

## 4. Inference-time Telepathy Adapter

A lightweight adapter (`sigma_adapter.py`) controls how much the telepathy residuals are allowed to modify the baseline π0.5 actions:

- reads:
  - baseline π0.5 actions (`base_action_vector`, …),
  - Sigma residuals,
  - telepathy diagnostics (norms, cosine alignments),
- computes a **risk-aware scaling factor** in min_scale, max_scale,
- blends:

```python
action = base_action + scale * telepathy_residual
```

If residuals are too large or misaligned, `scale` is pushed toward 0, effectively reverting to π0.5 behavior.  
If residuals are moderate and well aligned, `scale` approaches 1, enabling telepathy-enhanced control.

---

## 5. Evaluation Protocol

Evaluation uses `eval_sigma_vla_rollout.py` in **offline closed-loop replay**:

- both Sigma and the baseline:
  - use the *same* preprocessed shards (`shard_0000x.pt`),
  - share the *same* telepathy heads file `sigma_telepathy_heads.pt`,
- **only Sigma**:
  - loads LoRA weights,
  - activates telepathy residuals and the adapter in control output.

### 5.1 CHECK A – telepathy geometry & alignment sanity

CHECK A verifies that **telepathy geometry is identical** between experimental and control runs:

- `heads_tensors = 325`  
- `mean ≈ 0.002`, `std ≈ 0.107`, `rms ≈ 0.107` for telepathy head weights  
- `avg_tau_l2 ≈ 51.6` – average L2 norm of telepathy factors  
- `avg_semantic_text_alignment ≈ 0.13` – semantic factor vs. text embedding alignment

These numbers are matched between Sigma and the π0.5 baseline, so behavior differences cannot be explained by changing telepathy parameters or text alignment geometry.

### 5.2 CHECK B – multiscale control & telepathy metrics

CHECK B defines and reports:

- `mse_vec` – per-step action vector MSE (fine-grain control precision)  
- `mse_chk` – short segment chunk MSE (local motion consistency)  
- `mse_trj` – full trajectory MSE (long-horizon tracking)  
- `tau_l2` – telepathy factor norms (activation strength)  
- `sem_align` – semantic alignment (e.g., cosine) between semantic factors and text embeddings

On the same 723 samples and 181 batches:

- Sigma shows **consistently lower `mse_vec`, `mse_chk`, `mse_trj`** than the baseline,
- while **`tau_l2` and `sem_align` remain similar** between both models.

This pattern supports the interpretation that Sigma **uses the same semantic / telepathy geometry more effectively**, converting it into tangible gains in control accuracy instead of merely altering the embedding space.

---

## 6. How to Use Sigma

> ⚠️ You must have access to `lerobot/pi05_base` and the preprocessed shards or an equivalent environment to reproduce full experiments.

### 6.1 Installation (example)

```bash
# base env
pip install "transformers>=4.40.0" accelerate torch torchvision
pip install lerobot

# clone this repository (example path)
git clone https://github.com/Veltraxor/Sigma.git
cd Sigma
```

### 6.2 Loading Sigma on top of pi0.5

```python
import torch
from lerobot import Pi05Policy
from sigma_vla import SigmaTelepathyVLA, SigmaTelepathyAdapter

device = "cuda"
dtype = torch.bfloat16

# 1. Load base π0.5 policy
base_policy = Pi05Policy.from_pretrained("lerobot/pi05_base")

# 2. Build Sigma on top of the base policy
sigma_policy = SigmaTelepathyVLA.from_base(
    base_policy=base_policy,
    lora_dir="./storage/sigma_lora_out",
    telepathy_heads_path="./storage/sigma_lora_out/sigma_telepathy_heads.pt",
    device=device,
    dtype=dtype,
)

# 3. Optional runtime adapter
adapter = SigmaTelepathyAdapter(
    min_scale=0.0,
    max_scale=1.0,
    risk_temperature=1.0,
)

# 4. Single batch forward (offline replay)
batch = {
    "vis_obs": vis_obs_tensor,           # [B, T, C, H, W]
    "robot_state": robot_state_tensor,   # [B, T, D_state]
    "texts": list_of_text_prompts,       # length B
}

with torch.no_grad():
    out = sigma_policy(**batch, use_telepathy=True)
    blended_action = adapter(
        base_action_vector=out["base_action_vector"],
        telepathy_residual=out["telepathy_residual_vector"],
        telepathy_factors=out["telepathy_factors"],
    )
```

---

## 7. Repository Layout (typical)

A typical Sigma repo / model card includes:

```text
README.md                      # this file
sigma_env.example              # example env file for HF tokens, paths
dataset_preprocess_sigma_vla.py
train_sigma_telepathy_vla_lora.py
eval_sigma_vla_rollout.py
sigma_telepathy_vla.py         # model definition
sigma_adapter.py               # inference-time adapter

storage/
  sigma_pickplace/
    shard_00000.pt
    shard_00001.pt
    shard_00002.pt
  sigma_lora_out/
    sigma_telepathy_heads.pt
    adapter_config.json
    adapter_model.bin
    ...

logs/
  sigma_eval_report.json
  sigma_eval_checkA.json
  sigma_eval_checkB.json
```

You can adapt this layout to your own environment; the key assumption is that **Sigma is always loaded as a LoRA + telepathy delta on top of `lerobot/pi05_base`**.

---

## 8. Intended Use, Risks, and Limitations

- **Intended use**  
  Sigma is intended for **research and experimentation** on:
  - semantic / telepathy-style control in VLA systems,
  - offline trajectory analysis and simulation,
  - early-stage humanoid / manipulator control studies.

- **Not intended for**  
  - direct deployment on physical robots **without additional safety layers**;  
  - safety-critical or human-facing applications.

- **Known limitations**  
  - trained only on `svla_so101_pickplace`;  
  - evaluated only in offline replay;  
  - telepathy path tuned for a single task family and embodiment.

Users should treat Sigma as a **proof-of-concept** that demonstrates how “deep semantic + associative intent” can be engineered into residual control, not as a generic controller.

---

## 9. Author & Acknowledgements

- **Author**: **Libo Wang**  
- Base policy and dataset by **Physical Intelligence / LeRobot** teams.  
- Training environment based on a single RTX 4090 GPU; all scripts are structured to be portable to other single-GPU or multi-GPU setups with minimal changes.

---

## 10. Citation

If you use Sigma, please cite both the original π0.5 / OpenPI work and this Sigma extension.

**π0.5 / OpenPI:**

```bibtex
@article{openpi2024,
  title   = {Open-World Robotic Manipulation with Vision-Language-Action Models},
  author  = {Physical Intelligence},
  year    = {2024},
  url     = {https://github.com/Physical-Intelligence/openpi}
}
```

**Sigma (example entry):**

```bibtex
@article{sigma2025,
  title   = {Sigma: The Key for Vision--Language--Action Models toward Telepathy},
  author  = {Wang, Libo},
  year    = {2025},
  note    = {Telepathy-style extension of lerobot/pi05_base},
  url     = {https://huggingface.co/Veltraxor/Sigma}
}
```