Modular Behavior Trees for Transferable Robot Task Control

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Solution Overview

Problem

Existing behavior tree implementations for robot control are complex, labor-intensive, prone to errors, inefficient, and not easily transferable between similar tasks due to intertwined device-specific action blocks, leading to high computational costs and maintenance challenges.

Innovation Solution

A modular behavior tree system with a planner section and activation sections that dynamically adjust execution based on apparatus state and environment, allowing for interchangeable sub-trees and efficient resource management, enabling parallel and sequential task execution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If behavior trees are used to control robots performing complex layered tasks, then the robot can execute diverse and simultaneous tasks, but the behavior tree becomes complex and highly specialized requiring expert knowledge and being labor intensive to implement

Engineering Contradiction:

Improvetask execution capabilityVSAvoidbehavior tree complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The behavior tree is segmented into reusable subtrees that can be independently developed, tested, and maintained. Each subtree encapsulates specific task logic (e.g., navigation, manipulation) that can be composed to form complex behaviors, reducing overall system complexity while maintaining versatility.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Universal behavior tree nodes and subtrees are designed to perform multiple functions across different tasks and apparatus types. Standardized interfaces and parameterization allow the same subtree to be reused in various contexts, reducing the need for expert knowledge and lowering implementation effort.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If behavior trees contain repeated subtrees for high level tasks depending on executing similar core functions, then task coverage is improved, but complexity and efficiency deteriorate as the time necessary to query the behavior tree increases

Engineering Contradiction:

Improvetask coverageVSAvoidquery efficiency

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

Instead of physically copying subtree definitions throughout the behavior tree, the system uses references or pointers to shared subtree templates. This allows multiple tasks to reference the same core function subtree without duplicating its code, improving query efficiency while maintaining task coverage.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The behavior tree structure becomes dynamic through lazy evaluation and selective expansion of subtrees. Only the necessary portions of repeated subtrees are evaluated during query execution, reducing the effective query time while preserving comprehensive task coverage.

Inventive Principle:

Principle #15Dynamics

3Reliability

If behavior trees are made complex to handle varying preconditions and postconditions for different apparatus types, then task specificity is improved, but transferability between apparatus deteriorates

Engineering Contradiction:

Improvetask execution reliabilityVSAvoidapparatus transferability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The behavior tree nodes are parameterized to accommodate different apparatus types through configuration parameters rather than structural changes. Preconditions and postconditions are expressed as parameter constraints that can be satisfied by different apparatus implementations, maintaining reliability while enabling transferability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

An intermediary layer of abstraction is introduced between the behavior tree logic and apparatus-specific implementations. This mediator handles apparatus-specific variations in preconditions and postconditions, allowing the core behavior tree to remain apparatus-agnostic while ensuring reliable task execution for each specific apparatus type.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Speed

If behavior trees are traversed at high tick frequency to ensure responsive execution, then task responsiveness is improved, but computational cost increases

Engineering Contradiction:

Improvetask responsivenessVSAvoidcomputational cost

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The behavior tree traversal is performed periodically at optimized tick frequencies rather than continuously at maximum frequency. Event-driven triggers and state change detection allow the system to maintain responsiveness by executing traversals only when necessary, reducing computational cost while preserving task responsiveness.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS12379711B2Controlling an apparatus with a behavior tree

Publication Date: 2025.08.05 JUNGHEINRICH AG

AI summary

A method and a system for controlling an apparatus using a behavior tree for an assigned task performed by the apparatus. The behavior tree includes a planner section and an activation section. The method includes calling the planner section, determining the state of the apparatus and setting an activation status by the planner section in response to being called, and evaluating the activation status before executing the assigned task.