Compensated Position Control for Linear Motion Track Joints

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Solution Overview

Problem

In motion control systems with distributed position sensing, errors and jitter occur when movers transition between track segments due to differences in position measurement values between adjacent controllers, caused by asynchronous sampling and manufacturing tolerances, leading to torque pulsations and position determination inaccuracies.

Innovation Solution

Implementing a system where each track segment controller communicates and compensates position values with adjacent controllers, using either an average or weighted average of local and shared position measurements to determine a compensated position, which is then used for smooth transitions and reduced jitter, by sharing measured position values between adjacent segment controllers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If distributed position sensing is used with each controller determining position independently, then communication bandwidth requirements are reduced, but position measurement accuracy deteriorates due to asynchronous sampling and manufacturing tolerances

Engineering Contradiction:

Improvecommunication bandwidthVSAvoidposition measurement accuracy

Core Design Contradiction:

Loss of energyVSMeasurement precision

Solution Approach 1:

The system implements a feedback mechanism where each controller determines a compensated position value based on its local position sensor measurement and the shared position value from the adjacent controller. This feedback loop allows each controller to adjust its position determination to account for discrepancies between segments, maintaining accuracy without requiring high-bandwidth centralized communication.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent introduces an intermediary compensated position value that mediates between the local position sensor measurement and the shared position value from the adjacent controller. This intermediary value serves as a compromise that smooths transitions between segments, reducing the impact of manufacturing tolerances and asynchronous sampling while maintaining distributed control architecture.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Speed

If asynchronous sampling is used in distributed control, then real-time control of high-speed movers is enabled, but position continuity deteriorates causing jitter and torque pulsations

Engineering Contradiction:

Improvemover travel speedVSAvoidposition continuity

Core Design Contradiction:

SpeedVSStability of the object's composition

Solution Approach 1:

The system performs preliminary compensation of position values before the mover actually transitions between track segments. By determining compensated position values in advance based on shared position information from adjacent controllers, the system prepares smooth transition data that eliminates jitter and torque pulsations when the mover crosses segment boundaries, maintaining position continuity despite asynchronous sampling.

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If manufacturing tolerances in track segment assembly are present, then ease of assembly is improved, but position accuracy deteriorates at segment junctions

Engineering Contradiction:

Improvetrack segment assemblyVSAvoidposition accuracy at junctions

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent changes the parameter used for position control from raw position sensor values to compensated position values. This parameter transformation allows the system to account for manufacturing tolerances and gaps between track segments by incorporating offset values that compensate for physical misalignments, thereby maintaining position accuracy despite variations in assembly tolerances.

Inventive Principle:

Principle #35Parameter changes

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

This approach reduces step changes in position values during transitions, minimizing jitter and torque pulsations, and enhances the accuracy of mover positioning across track segment junctions.

Implementation Method 1

Successive activation of the coils establishes a moving electromagnetic field that interacts with the movers and causes the mover to travel along the track

Methodology Applied

Scientific EffectElectromagnetic field interaction: Electromagnetic Induction

Implementation Method 2

at least one first position sensor operative to detect a location of each of the movers on the first track segment

Methodology Applied

Scientific EffectPosition sensing:

Data Source

PatentUS11027615B2System and method for improving travel across joints in a track for a linear motion system

Publication Date: 2021.06.08 ROCKWELL AUTOMATION TECH INC

AI summary

A system for determining the position of a mover as the mover transitions between segments along a track includes a first controller on a first track segment and a second controller on a second track segment. The first and second track segments are adjacent to each other and a junction is located between the two segments. The first and second controllers are in communication with each other and share a locally determined position value with the other controller. Each controller determines a compensated position value as a function of both a locally determined position value and the shared position value received from the other controller. Each controller utilizes the compensated value of the position value as determined on that controller to control operation of the mover while it is present on the corresponding track segment.