Telescopic Ball Bar Measuring Device for Rotary Joint Calibration
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Solution Overview
Problem
Current measuring devices for checking geometric errors between rotary joints in positioning machines face limitations due to mechanical deformation, limited angular range of optical reflectors, and restricted linear measuring range, leading to inaccuracies and reduced usability in multilateration methods.
Innovation Solution
A measuring device with a telescoping connecting element and optical deflection system, where the reflector is arranged concentrically with the pivot point of the rotary joint, allowing precise tracking of the measuring beam and minimizing the impact of mechanical deformations, and featuring a control device and photodetector unit for automatic adjustment and correction of beam alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a telescopic ball bar with integrated displacement sensor is used, then mechanical rigidity and rotary joint functionality are provided, but the linear measuring range is limited to a few millimeters, restricting machine movements to circular or spherical paths
Solution Approach 1:
The patent combines a telescopic mechanical connection (ball bar) with an external optical length measuring system. The mechanical connection provides rigid support and rotary joint functionality, while the external optical system extends the measuring range beyond the limited few millimeters of the integrated sensor, enabling multilateration methods that require measurements across the entire working volume.
Solution Approach 2:
The patent introduces an external optical measuring system as an intermediary between the mechanical ball bar structure and the measurement process. This intermediary optical system (using lasers, interferometers, or other optical length measurement devices) translates the mechanical positioning capability into extended linear measuring range, allowing the system to function with both mechanical rigidity and expanded measurement versatility.
2Length of moving object
If telescopic extensions are used to increase measuring range, then the usable volume increases, but sagging due to weight and elasticity causes positioning deviations of several millimeters
Solution Approach 1:
The patent replaces direct mechanical measurement (which is limited by the rigidity and weight of telescopic extensions) with an optical measurement system. The optical system measures length independently of the mechanical extension's physical limitations, eliminating the several millimeter positioning deviations caused by sagging while still allowing extended measuring ranges through the telescopic structure.
Solution Approach 2:
The optical measurement system acts as an intermediary that decouples the measurement function from the mechanical support structure. The telescopic extension provides only mechanical support and positioning, while the optical system performs the actual length measurement without being affected by the extension's weight-induced sagging, thereby maintaining precision across extended ranges.
3Measurement precision
If a laser tracer with motorized tracking device is used, then continuous alignment and complete acquisition of geometric error parameters are achieved, but the device becomes cost-intensive and relatively large in size
Solution Approach 1:
The patent segments the measurement system into separate functional components: a simple telescopic mechanical connection providing structural support and rotary joints, and an external optical length measurement system performing the actual measurements. This segmentation eliminates the need for an integrated motorized tracking device, reducing system cost and size while maintaining the capability to acquire complete geometric error parameters through multilateration.
Solution Approach 2:
The patent enables the measuring device to self-align and self-correct through the concentric arrangement of the optical measurement system with the rotary joint pivot point. This geometric configuration automatically compensates for angular deviations and eliminates the need for expensive motorized tracking mechanisms, as the system inherently maintains measurement accuracy through its self-correcting geometric design.
4Measurement precision
If optical reflectors with maximum angular range of 160° are used, then optical length measurement is enabled, but the usable angular range is limited, reducing adaptability
Solution Approach 1:
The patent positions the optical length measurement system at the pivot point of the rotary joint, using this strategic intermediary location to maximize the usable angular range. By placing the optical system at the rotation center rather than at the end of an extension, the system can measure across the entire angular workspace without being constrained by the 160° limit of standard reflectors, as the measurement geometry radiates from the central pivot point.
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 solution provides accurate distance measurements between rotary joints, even with mechanical deformation, and allows for a larger pull-out ratio, reducing measurement uncertainties and enabling precise calibration of positioning machines without the need for manual beam adjustment.
Implementation Method 1
a device for optically measuring the length of the distance between the ball bodies from one another, which has at least one reflector device and a measuring beam
Implementation Method 2
a control device, a photodetector unit associated therewith and at least one optical deflection device assigned to the measurement beam
Data Source
Figure 1a~1b
Figure 2a~3b
Figure 4a~4b
AI summary
The invention relates to a measuring device for checking positioning machines for geometric errors between two rotational joints (2), comprising bearing ball elements (10, 20), which are mechanically connected to each other by means of a telescopic connecting element (30), and an apparatus (40) in order to measure the optical length of the spacing of the bearing ball elements (10, 20) from each other by means of at least one reflector apparatus (12, 22) and a measurement beam (50), wherein the at least one reflector apparatus (12, 22) is arranged in the bearing ball element (10, 20) in such a way that the reference point for the optical length measurement corresponds to the pivot point (11, 21) of the rotational joint (2).