Course materials · Reinforcement Learning for Electrical Engineering

Robot dataset analysis and VLA inputs/outputs

English translation

Graduate course · Research application activities

Read public demonstration data and establish evaluation criteria, then check the meanings of inputs and outputs connected to vision, language, and action models.

Before practice

01 Does low prediction error on recorded actions imply robot task success?

Description

Consecutive frames are strongly correlated, so random frame splits can differ from episode-level splits. Also distinguish recorded action prediction errors from actual task success rates.

02 How does a VLM's scene description differ from a VLA's action output?

Description

Camera input, current robot state, and language instructions lead to an action chunk. Using a pretrained policy requires knowing the robot-specific action representation, normalization, and timing.

Execution conditions

Small-scale data analysis requires requests, pandas, pyarrow, and scikit-learn. Read only one public Parquet file; an internet connection is required.

VLA model inference and training use separate hardware and model-specific environments.

If the required package is missing, run %pip install pyarrow==23.0.1 in a Colab or Jupyter code cell.

Applications

From demonstration data to a pick-and-place policy

Inspect public grasping and movement demonstrations to check the meaning of actions and the evaluation split. Extend a small offline baseline model toward policies using vision and language.

Observation·State
Synchronized camera images, robot states, and task instructions. Check the dataset features and time basis.
Action
Dataset-defined joint and gripper actions, and action chunks. First map their representation and normalization.
Reward·Constraint
Separate imitation-learning prediction error from actual task success. Record joint and input ranges and failure conditions.
Comparison baseline
Offline action prediction with state-only Ridge. Evaluate the closed-loop policy separately.
Metrics to check
Component-wise MAE for episode-level splits. Add success rate, safety violations, and latency for real or simulated execution.

Practice

Preview practice notebookDownload practice notebook

1. Analyze states and actions in a robot dataset

Starting conditions

Read the first Parquet shard of LeRobot svla_so100_pickplace. Do not download videos or model weights.

Procedure

  1. Use the provided code to check repository revision, FPS, episode count, and state/action shapes.
  2. Plot Episode 0 state and action against time, and compare the components and units of both arrays with the data card.
  3. State which metadata and features correspond to the camera, robot state, and natural-language instructions.

Results to retain

Items to record and points to check
Item
Feature·metadata
Shape and units
Verified meaning

Points to check

  • Did you avoid assuming joint targets equal current joint states?
  • Did you check the dataset revision and terms of use?

2. Episode-level evaluation and information leakage

Starting conditions

Split the loaded episodes into the first 80% and last 20%. Build a Ridge baseline model that predicts actions from states.

Procedure

  1. Sort the unique values of episode_index, use the first 80% of complete episodes for training and the remaining complete episodes for testing. Keep frames from the same episode from appearing in both sets, and record the episode IDs and frame counts for train/test.
  2. Train Ridge(alpha=1.) on the training set's state and action. Calculate component-wise MAE between test predictions action and ground truth using multioutput="raw_values".
  3. Also train and evaluate the same model with a random 80/20 split of frame indices from the same complete dataset. Tabulate MAE for each action component by split, and plot the true and predicted values of one component in the corresponding test order.
  4. Using the results from both splits, explain the difference between placing adjacent frames in both training and test sets and evaluating new episodes.

Results to retain

Items to record and points to check
Split
Number of training episodes
Number of evaluation episodes
Component-wise MAE
Potential leakage

Points to check

  • Did you exclude evaluation episodes from preprocessing and regression fitting?
  • Did you avoid calling prediction error on recorded actions a robot task success rate?

3. Inputs needed to extend to VLA

Starting conditions

Use the official SmolVLA explanation and the current dataset's features. Complete the input/output and evaluation design instead of training the entire model.

Procedure

  1. Tabulate the mapping from camera, current state, and instructions to action chunks.
  2. Identify where to check action normalization, coordinate systems, control periods, and delays during chunk execution.
  3. Design one additional observation, instruction, or evaluation episode needed for your research. When a GPU is ready, extend to pretrained policy inference using the official example.

Results to retain

Items to record and points to check
Inputs and outputs
Dataset mapping
Normalization and time basis
Evaluation method

Points to check

  • Did you distinguish VLA action outputs from VLM scene descriptions?
  • Did you avoid assuming a pretrained model immediately fits a different robot or action representation?

Explore further

  1. When using a VLM to interpret high-level goals, test image and instruction → structured goal conversion with vLLM's multimodal input examples.
  2. Measure inference latency and output validity, and separately validate coordinates and ranges before connecting to low-level robot actions.

Official examples and data