This paper presents the full research and development cycle of a high-precision absolute linear encoder based on a standard calibrated scale. Already available and used in industry standard scales of invar alloy were employed in the study. The scales have incremental indexes with 1 mm spacing intervals without an absolute code. However, the existing technical task is to measure the absolute position in the range of 2 m with accuracy less than 5 μm. For that, the developed encoder rationally combines magnetic measuring channel for the index numbering and an optical channel for the precise estimation of the encoder position. First, for the development, a simulation was performed to synthesize and analyze an image of an index. This image was used to develop a real-time double-threshold image processing algorithm to estimate the index position. Later the developed image processing algorithm was verified by preliminary testing and supported by a presented three-stage calibration procedure. The final measurements proved that the designed and developed encoder has the accuracy of 1.65 μm (3 standard deviations) at the speed up to 3 m/s. The possibility of use of standard calibrated scales with the presented encoder to solve existing and new industrial tasks forms the value of this paper. A possible use of the existing scales also provides unification and compatibility with conventional metrology equipment.

Reliable measurement of a deflection magnitude refers to one of the most important tasks in floating dry dock operation. Current and accurate information about the deflection can prevent structural damage and failure by activating alarms and on-board deflection compensation systems. This paper describes the development of a deflection measuring system for floating dry docks. The measuring system is capable of measuring the actual deflection of a dock structure in real-time and fully automatic mode. The system consists of a set of reference marks based on light emitting diodes and a measurement unit with two oppositely directed camera-based channels. The measurement unit is placed in the middle of a wing deck of the dock. The measurement unit and the reference marks are aligned along the wing deck. The accuracy of deflection measurement of ±1.5mm in the range of ±150 mm for the docks in length more than 100 m was achieved during laboratory tests. The system resistance to harsh environment (salt fog, temperature gradient, high humidity, etc.) and the ability to perform measurements in 24/7 regime was proved through field tests at a floating dry dock in operation.