Articulated Robot Joint Torque Correction Using Angle Information

Solution Overview

Problem

Existing articulated robots face challenges in accurately detecting torque about the axis line of a joint due to loads applied in directions other than the axis line, leading to incorrect torque correction and potential operational errors.

Innovation Solution

A robot configuration that includes torque sensors, angle information detection units, and a correction unit to estimate and correct torque changes caused by loads other than the axis line torque, using rotation angle characteristics and physical parameters to accurately calculate and apply correction torques, thereby isolating actual torque applied to the axis line.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If torque sensors are installed on all joints to accurately detect torque, then measurement precision is improved, but device complexity and cost increase

Engineering Contradiction:

Improvetorque detection accuracyVSAvoidnumber of torque sensors

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The invention extracts and eliminates the unwanted torque components (torque about axes other than the target joint's axis line) from the torque sensor detection. By using angle information from other joints to calculate and subtract these extraneous torque components, the system achieves accurate target joint torque measurement without requiring torque sensors on all joints.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention introduces angle information detection units and a correction calculation unit as intermediary elements. These intermediaries bridge the gap between the single torque sensor and the multiple joints, enabling the torque sensor's detection to be corrected for influences from other joints through mathematical calculation based on detected angle information.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If torque sensors are installed on all joints to accurately detect torque, then measurement precision is improved, but cost increases

Engineering Contradiction:

Improvetorque detection accuracyVSAvoidmanufacturing cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The invention extracts and eliminates the unwanted torque components (torque about axes other than the target joint's axis line) from the torque sensor detection. By using angle information from other joints to calculate and subtract these extraneous torque components, the system achieves accurate target joint torque measurement without requiring torque sensors on all joints.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention replaces expensive torque sensors with cheaper angle information detection units on joints other than the target joint. The correction is achieved through calculation rather than additional expensive sensing hardware, significantly reducing the overall system cost while maintaining measurement precision.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Device complexity

If torque about axis line is detected directly without correction, then device complexity is reduced, but measurement precision deteriorates due to load interference

Engineering Contradiction:

Improvetorque sensor configurationVSAvoidtorque measurement accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The invention implements a feedback mechanism where angle information from all joints is continuously detected, used to calculate the torque components about axes other than the target joint's axis line, and then this calculated information is fed back to correct the torque sensor detection. This closed-loop correction ensures accurate torque measurement while maintaining simple device configuration.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The invention introduces angle information detection units and a correction calculation unit as intermediary elements. These intermediaries bridge the gap between the single torque sensor and the multiple joints, enabling the torque sensor's detection to be corrected for influences from other joints through mathematical calculation based on detected angle information.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS11691293B2Robot

Publication Date: 2023.07.04 FANUC LTD

AI summary

A robot including a plurality of joints each configured to rotate about an axis line; a torque sensor S1 configured to detect torque about the axis line of a target joint as one of the plurality of joints; angle information detection units configured to detect information related to a rotation angle of each of the joints about the axis line; a torque change amount estimation unit configured to estimate a change amount of the torque detected by the torque sensor due to a load other than the torque about the axis line of the target joint based on the detected information; and a correction unit configured to correct the torque detected by the torque sensor by using the estimated change amount.