Robot Reducer Error Correction from Partial Rotation Measurements

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Solution Overview

Problem

Existing methods for correcting angular transmission errors in robot arm reducers require rotating the drive shaft over its entire range, which is impractical in limited environments, leading to inaccurate error calculation and reduced drive accuracy.

Innovation Solution

A method that measures and records angular transmission errors within a smaller input rotation angular range, using an encoder and inertial sensor data, and creates correction data when the accumulated measurement time or range meets a predetermined threshold, allowing for accurate error correction without full-range rotation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the drive shaft is rotated over the entire range of the rotatable angle to measure angular transmission error, then the measurement accuracy is improved, but the operation time and system complexity increase

Engineering Contradiction:

Improveangular transmission error measurement accuracyVSAvoidtime required for full-range rotation

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent applies partial action by measuring angular transmission error only within a limited rotation angle range rather than requiring full-range rotation. The control apparatus accumulates measurement data over multiple partial rotations, using a cumulative measurement count threshold to determine when sufficient data has been collected for accurate correction data generation.

Inventive Principle:

Principle #16Partial or excessive action

2Reliability

If the drive shaft is rotated over the entire range of the rotatable angle, then complete error data is obtained, but the device complexity and operational constraints increase

Engineering Contradiction:

Improvecompleteness of error correction dataVSAvoidoperational flexibility in limited environments

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent implements dynamics by making the measurement range adaptive rather than fixed. The control apparatus dynamically adjusts the measurement process by accumulating data from multiple partial rotations and using a cumulative count threshold to determine when sufficient data has been collected, allowing the system to achieve reliable correction data without requiring full-range rotation in every case.

Inventive Principle:

Principle #15Dynamics

3Measurement precision

If multiple measurements are accumulated over time, then the measurement precision is improved, but the measurement time increases

Engineering Contradiction:

Improveangular transmission error correction accuracyVSAvoidspeed of correction data generation

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent applies feedback by continuously monitoring the cumulative measurement count and comparing it against a predetermined threshold. The control apparatus uses this feedback to automatically determine when sufficient measurement data has been accumulated, enabling it to stop the measurement process at the optimal point rather than requiring fixed-time or full-range measurements.

Inventive Principle:

Principle #23Feedback

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables accurate correction of angular transmission errors even in environments where full-range rotation is not possible, improving drive accuracy and motion precision of the robot arm.

Implementation Method 1

an encoder detecting a rotation angular position of the input shaft

Methodology Applied

Scientific EffectEncoder detection:

Implementation Method 2

an inertial sensor provided in the arm and detecting a rotation angular velocity of the arm

Methodology Applied

Scientific EffectInertial sensor detection:

Data Source

PatentUS12000476B2Method of correcting angular transmission error for reducer and robot system

Publication Date: 2024.06.04 SEIKO EPSON CORP

AI summary

A method of correcting an angular transmission error for a reducer of creating correction data for correction of an angular transmission error of the reducer in a robot system including an arm, the reducer having an input shaft and an output shaft, a motor, an encoder, and an inertial sensor, includes rotating the arm in an input rotation angular range smaller than a necessary input rotation angular range, measuring and recording the angular transmission error, determining whether or not an accumulated value of measurement times is equal to or larger than a predetermined value, when the accumulated value is smaller than the predetermined value, measuring the angular transmission error of the reducer and updating a record, and, when the accumulated value is equal to or larger than the predetermined value, creating the correction data based on the recorded angular transmission error of the reducer.