Inconsistencies in Models ofAdaptive Service Robots

Ivan Ruchkin *PhD Student in Software Engineering

Institute for Software ResearchCarnegie Mellon University

* with images from Jonathan Aldrich, Javier Cámara, and Bradley Schmerl

Software Research Seminar (SSSG)April 10, 2017

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Service robot missions

● Autonomy in the face of uncertainty● Timeliness, power, safety

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Centralized online adaptation

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Centralized online adaptation

Does it work?

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How to check if it works

Run the system

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How to check if it works

Run the system

Run the simulation

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How to check if it works

Run the system

Run the simulation

Analyze the models

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How to check if it works

Run the system

Run the simulation

Analyze the models

Analyze the code

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How to check if it works

Run the system

Run the simulation

Analyze the models

Analyze the code

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Plan for today

● Inconsistency 1: power● Inconsistency 2: turns● What is common? ● Tentative approach: detection

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Inconsistency 1: power in simulation vs hardware

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Inconsistency 1: power in simulation vs hardware

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Inconsistency 1: power in simulation vs hardware

Model source: hardware experiments

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Inconsistency 1: power in simulation vs hardware

Model source: hardware experiments

Simulation: fixed increments

Simulation

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Inconsistency 1: power in simulation vs hardware

Model source: hardware experiments

Simulation: fixed increments

Simulation

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Inconsistency 1: models

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Inconsistency 1: models

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Inconsistency 1: summary

● Hardware power predictions do not match the simulation– Initially optimistic, later pessimistic

● Obscured by mixing power dynamics– Mode switching

– CPU and sensors

● Definition: – What deviations are acceptable, over what time?

● Assurance: – Simulation, corner case tests

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Inconsistency 2: turning in instruction graphs vs planning

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Inconsistency 2: turning in instruction graphs vs planning

A

B

C

D

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Inconsistency 2: turning in instruction graphs vs planning

A

B

C

D

Instructiongraph A B C D

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Inconsistency 2: turning in instruction graphs vs planning

A

B

C

D

A Planning + cost(C)

B D

Instructiongraph A B C D

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Inconsistency 2: turning in instruction graphs vs planning

A

B

C

D

A Planning + cost(C)

B D

Instructiongraph A B C D

State estimation = ?

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Inconsistency 2: models

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Inconsistency 2: models

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● Planning and execution represent turning differently ● State estimation is uncertain during a turn

– If optimistic, can run out of power

– If pessimistic, can waste time on charging

● Definition: – Bound of utility loss from state estimation uncertainty

● Assurance: – Quantitative model checking

Inconsistency 2: summary

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What is common?

A

B D

A B C D

Power in simulation/hardware Turns in planning/execution

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Models: big picture

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Models: big picture

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Models: big picture

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What is common?

A

B D

A B C D

Power in simulation/hardware Turns in planning/execution

● Several models with differing assumptions● Definition: bounded mismatch● Checking requires multiple semantics

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Detecting Inconsistencies

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Detecting Inconsistencies

1. Relate models ● Manual

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Relating models

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Relating models

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Detecting Inconsistencies

1. Relate models ● Manual

2. Specify consistency properties● Manual

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Specifying consistency

“Predicted and simulated power always stay within a fixed error bound”

□ ∀p, t · p = PowPred(t) → □ ( time = t → | PowSim – p | < ε)

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Detecting Inconsistencies

1. Relate models ● Manual

2. Specify consistency properties● Manual

3. Find potential inconsistencies● Automated

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Finding potential inconsistencies

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Finding potential inconsistencies

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Detecting Inconsistencies

1. Relate models ● Manual

2. Specify consistency properties● Manual

3. Find potential inconsistencies● Automated

4. Check if the consistency properties hold ● Automated

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Checking properties

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Summary

Four-step approach: Relate – Specify – Find – Check