Robotic Task Sequencing With Demonstration-Guided Primitive Planning

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Solution Overview

Problem

Designing controllers for long-horizon, sequential robotic tasks is challenging due to a large search space and the need for careful reward engineering in reinforcement learning, making it inefficient and data-intensive.

Innovation Solution

The proposed method uses learning from demonstration (LfD) to decompose long demonstrations into meaningful sequences and compose them optimally for novel tasks, employing dynamic movement primitives and graph-search based planning to identify and execute sequences efficiently.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If reinforcement learning is used to learn sequences for long-horizon tasks, then the robot can find solutions in the large search space, but it requires enormous amount of data and careful reward engineering

Engineering Contradiction:
Improveability to perform novel tasksVSAvoidamount of data required
Core Design Contradiction:
Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

The patent segments long-horizon tasks into smaller sub-tasks or sequences. Instead of learning entire long sequences at once, the system breaks down complex tasks into manageable chunks that can be learned and reused. This segmentation allows the robot to learn from demonstrations more efficiently without requiring enormous amounts of data, as each segment can be independently learned and then composed to solve novel tasks.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent employs preliminary action by pre-segmenting demonstrated tasks into reusable sequences before encountering novel tasks. The system learns from demonstrations in advance, creating a library of sequences that can be later composed to solve new tasks. This preliminary learning phase reduces the data requirements when facing novel tasks, as the system already has pre-learned sequences to work with.

Inventive Principle:
Principle #10Preliminary action

2Device complexity

If the robot learns full tasks as single motor skills, then the learning process is simplified, but it cannot handle sequential tasks with multiple steps

Engineering Contradiction:
Improvelearning model complexityVSAvoidability to perform sequential tasks
Core Design Contradiction:
Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent applies segmentation by dividing long-horizon tasks into multiple sequences or sub-tasks. Instead of treating each task as a single monolithic skill, the system breaks them down into smaller, reusable sequence segments. This allows the robot to maintain simpler learning models for each segment while still handling complex sequential tasks through composition of these segments.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent introduces dynamics by making the task representation flexible and composable. The system learns sequences that can be dynamically selected and composed based on the specific task requirements. This dynamic composition capability allows the robot to adapt to different sequential tasks using the same set of learned sequences, maintaining simplicity while achieving versatility.

Inventive Principle:
Principle #15Dynamics

3Manufacturing precision

If reinforcement learning with dense rewards is used for long-horizon tasks, then the robot can learn optimal sequences, but it requires prohibitive amount of data and complex reward engineering

Engineering Contradiction:
Improvesequence optimization accuracyVSAvoidreward engineering complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent extracts the reward engineering complexity from the overall system by using demonstration-based learning instead of reinforcement learning. Instead of requiring complex reward functions to guide learning, the system extracts sequences directly from demonstrations, which inherently contain the optimal behavior. This extraction approach achieves sequence optimization without the need for complex reward engineering.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent uses copying by replicating sequences from demonstrations rather than learning them from scratch through reinforcement learning. The system copies successful sequences from demonstrated tasks and reuses them for novel tasks, achieving optimization accuracy without requiring the prohibitive data and complex reward structures that reinforcement learning would demand.

Inventive Principle:
Principle #26Copying

Data Source

PatentEP4460412B1System and method for learning sequences in robotic tasks for generalization to new tasks
Publication Date: 2025.04.09 MITSUBISHI ELECTRIC CORP
  • EP4460412B1 patent drawingFigure 1
  • EP4460412B1 patent drawingFigure 2A
  • EP4460412B1 patent drawingFigure 2B

AI summary

A robotic controller is provided for generating sequences of movement primitives for sequential tasks of a robot having a manipulator. The controller includes at least one control processor, and a memory circuitry storing a dictionary including the movement primitives, a pretrained learning module, and a graph-search based planning module having instructions stored thereon. The controller to perform steps acquiring a planned task provided by an interface device operated by a user, wherein the planned task is represented by an initial state and a goal state with respect to an object, generating a planning graph by searching a feasible path of the object for the novel task using the graph-search based planning module and selecting movement primitives from the dictionary in the pretrained learning module, wherein the pretrained learning module has been trained based on demonstration tasks, parameterizing the feasible path represented by the movement primitives as dynamic movement primitives (DMPs) using the initial state and goal state, and implementing the parameterized feasible path as a trajectory according to the selected movement primitives using the manipulator of the robot by tracking and following the parameterized for the planned task.