Manipulator Model Validation via Force Difference Comparison

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Solution Overview

Problem

Model-based control of manipulators faces challenges due to inaccuracies in mechanical models, leading to undesired dynamics and unforeseen movements, often caused by incorrect parameters, sensor misadjustments, and external disturbances, which degrade performance and safety.

Innovation Solution

A method for validating the mechanical model of a manipulator by comparing virtual and real forces before applying target forces, ensuring the difference remains within specified limit values to prevent undesired dynamics, involving multiple validation stages based on the manipulator's state and environmental conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If model-based control is used to achieve desired dynamics, then control performance is improved, but model inaccuracies cause undesired movements and degrade reliability

Engineering Contradiction:
Improvecontrol reliabilityVSAvoidmodel accuracy
Core Design Contradiction:
ReliabilityVSMeasurement precision

Solution Approach 1:

The patent applies preliminary validation of the mechanical model before executing model-based control actions. The system validates the model by comparing predicted forces with actual forces under current operating conditions, and only proceeds with control actions if validation succeeds. This preliminary check prevents unreliable control actions caused by model inaccuracies.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent implements a feedback mechanism where the actual forces experienced by the manipulator are continuously measured and compared with the forces predicted by the mechanical model. This feedback loop enables the system to detect model inaccuracies and trigger re-validation or fallback to safe modes, thereby maintaining control reliability despite model imperfections.

Inventive Principle:
Principle #23Feedback

2Reliability

If model validation is performed to ensure accuracy, then control safety is improved, but validation time and system complexity increase

Engineering Contradiction:
Improvecontrol safetyVSAvoidvalidation time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The patent makes the validation process dynamic by adapting validation frequency and depth to current operating conditions. Validation is performed continuously in the background, with full validation triggered only when necessary (e.g., when model drift is detected or operating conditions change significantly). This dynamic approach balances safety requirements with time efficiency.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent implements partial validation by checking only critical model parameters and forces relevant to current operational context, rather than validating the entire model comprehensively. This selective validation approach provides sufficient safety assurance while minimizing validation time and computational overhead.

Inventive Principle:
Principle #16Partial or excessive action

3Reliability

If comprehensive model validation is performed, then undesired dynamics are prevented, but device complexity increases

Engineering Contradiction:
Improvedynamics controlVSAvoidvalidation system complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent enables the control system to perform self-validation using its own operational data. The system uses forces it experiences during normal operation to validate its mechanical model, eliminating the need for external validation equipment or complex separate validation systems. This self-service approach reduces device complexity while maintaining comprehensive validation.

Inventive Principle:
Principle #25Self-service

Data Source

PatentEP2072194B1Method and device for model-based controlling of a manipulator
Publication Date: 2019.05.08 KUKA DEUT GMBH
  • EP2072194B1 patent drawingFigure 1~2
  • EP2072194B1 patent drawing
  • EP2072194B1 patent drawing

AI summary

The method involves determining a virtual force exerted by a manipulator e.g. industrial robot, based on a model of the manipulator, and determining a real force exerted by the manipulator. The difference between the virtual force and the real force is compared with a maximum limit value. The manipulator is subjected only with a reference force determined based on the model of the manipulator when the difference between the virtual force and the real force is smaller than the maximum limit value. Independent claims are also included for the following: (1) a control device for a manipulator, for executing a method for model-based controlling of the manipulator (2) a computer program for executing a method for model-based controlling of a manipulator (3) a computer program product with a program code including a computer program for executing a method for model-based controlling of a manipulator.