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Plan-Based Robot Control Joachim Hertzberg Contents What is Plan-Based Robot Control? Examples Research Areas Conclusion 1. What is Plan-Based Robot Control? Examples Research Areas Conclusion Planning in Autonomous Robotics/AI Robotics [Murphy]

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Plan based robot control l.jpg
Plan-Based Robot Control

  • Joachim Hertzberg

Contents l.jpg

  • What is Plan-Based Robot Control?

  • Examples

  • Research Areas

  • Conclusion

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  • What is Plan-Based Robot Control?

  • Examples

  • Research Areas

  • Conclusion

Robot plans classical non classical l.jpg

Planning in Autonomous Robotics/AI Robotics [Murphy]

The plan is that part of the robot’s program,whose future execution the robot reasons about explicitly[D. McDermott, 1992]

…and typically does so on-line and on-board. [JH, 2003]

Robot Plans – Classical & Non-Classical

  • Types of Planning in Automation-Style Robotics

  • Path Planning

  • Trajectory Planning

  • Motion Planning

  • Inverse Kinematics

  • Control Theory

  • Scheduling

The application impact of ai robotics robot plans l.jpg

Plans serve as abstract, high-granular descriptions of robot action


The Application Impact of AI Robotics & Robot Plans

  • Increase the automation degree in poorly controlled environments

  • Populated areas (e.g., supermarket cleaning, airport courier DTVs)

  • Areas with independent processes going on (e.g., multi-agent domains)

  • Areas with adversarial processes going on (e.g., military/security applications)

  • Areas with lack of detailed domain knowledge (e.g., inspection, space, rescue)

NASA Mars Exploration Rover Mission

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  • What is Plan-Based Robot Control?

  • Examples

  • Research Areas

  • Conclusion

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Pose planning

View Pose Planning in 3D SLAM

  • 3D SLAM means:

  • Registration of scans from different poses;

  • planning and collision-free execution

  • of feasible trajectories through known open space

  • to poses of locally maximal expected info. gain

[Surmann&al., ISR-2001]

[Nüchter&al., ICAR-2003]

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Digression: Virtual Flight through the 3D Model

Voxels coloured bylaser remission values

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Monitoring Intricate Closed-Loop Motion

Application Task

Control closed-loop turn or turn&climb manoeuvres of an articulated 21 DOF multi-segement robot in confined space (sewer pipe junctions)

Technical Problem

Provide robust on-line error diagnosis and recovery in case the manoeuvre fails(and detect failure in the first place)

Solution idea

Represent turning manoeuvres as (carefully handcrafted!) HTNs with alternative expansions and sense-able operator preconditions and postconditions

[Streich et al., 2000; Robotik-2000][Rome et al., 1999; J.Urban Water]

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Mission-Level User Interaction

  • Sewer map

  • Sensor modules

  • Inspection tasks

  • Proceed along path p; thereby:with localization do:

  • Note house inlets

  • Note changes in pipe diameter

  • Take photos of grown-in tree roots

[Streich et al., Robotik-2000]

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Performance Optimization in Indoor Navigation

Application Task (RHINO robot):

Indoor navigation using a given map

Technical Problem

Optimize expected travel time by context-dependent changes of navigation control

Solution Idea

Represent mid-level navigation actions as HTNs with alternative expansions and sense-able operator preconditions and postconditions(e.g. SET-TARGET(x,y,d), TURN-TO(x,y), MOVE-FWD(d); APPROACH-POINT(x,y,d), MDPGOTO(x,y))

[Belker et al., 2003; ICRA]

Operator expansion hierarchy l.jpg

dx,dy in {1m, 2m, 4m} dist.

d e {0.5m, 1m, 2m}











Operator Expansion Hierarchy


Plan execution example l.jpg

APPROACH-POINT(2,pending, 1434,1009,1m)


SET-TARGET(3,pending, 1434,1009,1m)



APPROACH-POINT(4,pending, 1477,1158,1m)


SET-TARGET(5,pending, 1477,1158,1m)

…(4, expanded,…))


MOVE-BACKWARD(6,pending, 30cm)

SET-TARGET(7,pending, 1477,1158,1m)



Plan Execution Example

MDPGOTO(1,pending, 1521,1563)

Assume executionwith success

No Admissible Trajectory!!

etc .…

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Solution 2

Project results of different HTN expansions; acquire models for expected execution times by learning

Learned Prediction Rule (expl.)

if path curvature < 1.05 and not crosses-door and path length ≥ 110 and path length < 130then duration = 1/23.99 * path length

Gain: ≈ 40%

Expansion Selection Alternatives

Solution 1

Hand-code context-dependencies(e.g., “If space gets narrow, set target points closer”).

Gain: ≈ 30%

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By-Products of the Plan-Based Representation

By-Product I

Transparent behavior in coping with navigation set-backs(e.g., blocked pathways, occlusion of intermediate target points)

By-Product II

Rational reconstruction of part of the navigation system, which allows for much higher code transparency

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SHAKEY, 1969


  • What is Plan-Based Robot Control?

  • Examples

  • Research Areas

  • Conclusion

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a? dv/dt?

Integration/ Robot Control Architectures

  • “Eternal Constraints”

  • Never run down your batteries!

  • Give priority to directors’ missions!

  • Schedule for June 16, 2003

  • Update map of 1st floor

  • Deliver mail at 10:00

  • Pick up visitor at the gate at 13:30

  • Recent Information

  • Elevator maintenance 8:00–10:00

  • Secretary is on vacation

The modern solution: Hybrid Architectures [Murphy, 2000]

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Turning Sensor Signals into Symbols

Potentially very rich sensor information is available for mobile robots

  • To use it in plan-based robot control,

  • Symbolic facts / fact hypotheses need to be extracted from that;

  • on-line update of knowledge bases needs to be performed;

  • sensor readings may be unreliable, knowledge may come with different time stamps;

  • planning must work on possibly inconsistent/para-consistent knowledge bases

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Topics List

  • Robot plan ontologies

  • Planning under uncertainty

  • Planning under inconsistency

  • Anytime planning for robot control

  • Practical knowledge base update

  • Plan execution monitoring

  • Symbol grounding / object anchoring

  • Learning for robot plan optimization

  • Learning for robot plan ontology optimization

Whatever it is,remember you are dealing with complete robot systems(mechanics, electronics, sensors, control theory, …)

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  • What is Plan-Based Robot Control?

  • Examples

  • Research Areas

  • Conclusion

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Some Sources of Further Information

  • Beetz/ Hertzberg/ Ghallab/ Pollack (eds.):Advances in Plan-Based Control of Robotic AgentsSpringer (LNAI vol. 2466), 2002

  • Robin Murphy:Introduction to AI RoboticsMIT Press, 2000

  • Stay tuned to the NASA Mars Exploration Rover Missionafter landing in early January 2004

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Conclusion: Robot Plans …

  • … are control program bits that the robot is supposed to reason about

  • … are but one small part of an overall robot system

  • … may come in different syntactic forms and on different granularity levels

  • … may serve many different purposes, such as

    • performance optimization,

    • failure recovery,

    • learning, and more

  • … have been successful on a number of experimental or prototype robot systems

  • … have not yet been used in mass-market AI-type robots (“Service Robots”)

  • … still involve some basic research problems (integration, symbol grounding)

  • … are an enabling technology for building AI robot applications.

Plan-based robot control has to offer an enabling technology for increasing the automation degree in poorly controlled environments

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The End

  • What is Plan-Based Robot Control?

  • Examples

  • Research Areas

  • Conclusion

  • The End

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Scan Matching

  • Algorithm ICP (Besl, McKay & al., 1992)

  • Our variant:

    • on-line, on-board

    • registers 2 scans (181x256) in <1.4 sec.

    • Robot pose correction as a by-product

    • Registration of multiple scans

From Point Clouds to a 3D Geometry Model: Registration

AIS 3D-Laser Scanner