Decoupled Vertical Position Measurement Using Cable and Pulley
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Solution Overview
Problem
Existing position measurement systems, such as linear measuring systems and cable pull transducers, suffer from inaccuracies and geometric errors, particularly in applications requiring high precision like radiotherapy, and are unsuitable for measuring vertical positions in apparatuses with complex geometries.
Innovation Solution
A measuring system comprising a sensor tape, sensor, traction cable, and deflection pulley that allows for precise measurement of vertical positions by deflecting the traction cable from a first direction into a second direction, enabling a spatially separated and robust measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If cable pull transducers are used for position measurement, then the measuring system can be installed without direct attachment to the measurement axis, but the measurement precision deteriorates due to cable winding inaccuracies and non-constant errors over the measuring range
Solution Approach 1:
The patent introduces a pulley as an intermediary mechanical element that redirects the cable pull transducer's measurement axis. The cable is routed through the pulley so that the measurement axis becomes parallel to the scissor mechanism's movement direction rather than requiring direct attachment. This intermediary arrangement maintains installation flexibility while improving measurement precision by eliminating geometric errors associated with direct attachment to complex mechanisms.
2Measurement precision
If linear measuring systems are arranged directly at the measurement axis, then measurement precision is improved, but the device complexity increases and direct attachment becomes necessary
Solution Approach 1:
The pulley serves as a mediator that decouples the linear measuring system from direct attachment to the measurement axis. By routing the cable through the pulley, the system achieves direct measurement of the scissor mechanism's movement without requiring complex integration of the measuring system into the mechanism's structure, thus reducing device complexity while maintaining high precision.
Solution Approach 2:
The measuring system is segmented into separate functional components: the cable pull transducer, the pulley, and the scissor mechanism. This segmentation allows each component to be optimized independently - the scissor mechanism handles the lifting function while the cable pull transducer with pulley handles the measurement function, simplifying the overall system configuration.
3Length of stationary object
If the measuring length of cable pull transducer is increased to cover the full vertical range, then the measuring range is improved, but the measurement precision deteriorates due to accumulated cable winding errors
Solution Approach 1:
The pulley acts as a mechanical intermediary that changes the direction of cable pull, allowing the cable pull transducer to measure vertical displacement over a long range without the cable winding through multiple layers on the drum. The cable is routed through the pulley in a way that maintains consistent tension and minimizes winding errors, enabling accurate measurement over the full vertical range of the scissor mechanism.
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 and robust measurement of vertical positions over the entire measuring range, reducing geometric errors and measurement inaccuracies, and allowing for precise determination of height and length values without the need for direct attachment to the measurement axis.
Implementation Method 1
a deflection pulley (11) that deflects the traction cable (10) from a first direction (R1) into a second direction (R2)
Data Source
AI summary
A system for ascertaining position information for a measuring position of a measurement object, comprises: a sensor tape; a sensor configured to capture position information on the sensor tape; a traction cable configured to transmit the measuring position of the measurement object to the sensor; and at least one deflection pulley configured to deflect the traction cable from a first direction in a second direction.