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Lesson 14 of 21 in this unit

Build AI Systems · ORIGINAL LEARN AI LESSON

Predict actions from observations.

Train an imitation policy and diagnose closed-loop distribution shift.

By the end: Train an imitation policy and diagnose closed-loop distribution shift.

Start with the exampleJump to the experimentRead the explanation
Prerequisites and path options

Why learn this? Learn how observation-conditioned action fitting differs from executing a safe and successful whole task.

01 · TRY

Start with something concrete.

A student driver can match familiar steering demonstrations yet fail after drifting away from the road centre. Robot imitation has the same feedback problem.

Try the interactive model
02 · PREDICT
Before you experiment

What does low error on demonstrated actions establish?

What does low error on demonstrated actions establish?
03 · EXPERIMENT

Change one thing. Watch what follows.

Loading this browser experiment…

04 · UNDERSTAND
READ & CONNECT

Understand what changed.

Back to the experiment

A shorter explanation, with the original worked examples available below. Both explain the same experiment and its limits.

Same learning goal in both modes: Train an imitation policy and diagnose closed-loop distribution shift.

The question

A student driver can match familiar steering demonstrations yet fail after drifting away from the road centre. Robot imitation has the same feedback problem.

Try it and inspect what changed

Train the policy, introduce a 0.3 m displacement and inspect its recovery.

Compare initial and trained policies at the same start and disturbance. Inspect the observation used for a poor action. Was that observation represented in collection? Add a recovery demonstration before claiming the architecture needs to be larger.

The calculation in words

The network receives six numbers: puck x/y, goal x/y and two instruction indicators. Eight tanh hidden units produce six tanh outputs: three planar commands. Training minimizes mean half-squared command error. Every gradient uses the same preceding checkpoint; the update rate is 0.6 and the interface performs at most five updates per action.

Keep the conclusion within the evidence

Our coordinates come directly from the rendered scene, so this is learned control from visual positions, not a learned image detector. The teacher is a proportional controller with saturation. Compare it directly with the network: a learned approximation is not automatically better than its teacher. Training only sees supplied and explicitly recorded training trajectories.

Repeated public development runs support debugging, not a final generalization claim. Four hundred updates is a work limit, not a convergence guarantee. A policy checkpoint does not authenticate how it was trained.

You can explore every lesson directly. Completing this page, submitting a project report and demonstrating understanding on a separate case are different records. Optional code is available in the robot-learning studio; it does not increase guided lesson completion requirements.

Open the full worked examples, calculations and limitations

This is the same reference used in Technical mode. Expand it whenever you need the exact numbers, assumptions or further explanation.

Start with the task

A student driver can match familiar steering demonstrations yet fail after drifting away from the road centre. Robot imitation has the same feedback problem.

Mechanism and units

The network receives six numbers: puck x/y, goal x/y and two instruction indicators. Eight tanh hidden units produce six tanh outputs: three planar commands. Training minimizes mean half-squared command error. Every gradient uses the same preceding checkpoint; the update rate is 0.6 and the interface performs at most five updates per action.

Our coordinates come directly from the rendered scene, so this is learned control from visual positions, not a learned image detector. The teacher is a proportional controller with saturation. Compare it directly with the network: a learned approximation is not automatically better than its teacher. Training only sees supplied and explicitly recorded training trajectories.

Work through the evidence

Compare initial and trained policies at the same start and disturbance. Inspect the observation used for a poor action. Was that observation represented in collection? Add a recovery demonstration before claiming the architecture needs to be larger.

Train the policy, introduce a 0.3 m displacement and inspect its recovery.

What this experiment can establish

Repeated public development runs support debugging, not a final generalization claim. Four hundred updates is a work limit, not a convergence guarantee. A policy checkpoint does not authenticate how it was trained.

Keep collection, fitting, frozen execution and interpretation as separate records. Save the configuration and complete result, including failures, in the robot-learning project. Report submission checks required evidence and text presence; reasoning and implementation quality need independent review.

05 · APPLY
Check your understanding

A policy matches demonstration actions but fails after a push off its usual path. What comparison diagnoses this?

A policy matches demonstration actions but fails after a push off its usual path. What comparison diagnoses this?
06 · CONTINUE

Take this idea with you.

Repeated public development runs support debugging, not a final generalization claim. Four hundred updates is a work limit, not a convergence guarantee. A policy checkpoint does not authenticate how it was trained.

My Learning
Explore related topics and the topic map

How this topic connects

Explore this topic on the interactive map

Use these connections to review a foundation or choose where to go next. You can open any topic without completing the others.

What it builds on

  • Geometry and control

    Prevent coordinate-frame mistakes when combining robot positions, sensor readings and targets.

You are herePredict actions from observations

Train an imitation policy and diagnose closed-loop distribution shift.

What it enables

  • Robot-learning project Apply in a project

    Combine demonstration provenance, policy comparisons and complete-task evidence in the robot-learning project; keep embodiment limits and review status explicit.

Original Learn AI lesson ·Primary robotics reference