Creating an Advanced Motion Control and Image Processing System for Non-Destructive Inspection of Subsea Mooring Lines

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"Using LabVIEW and NI hardware, we could efficiently and effectively test new ideas and experiment with different designs throughout the development process. Having a single development platform that can incorporate vision, motion, I/O, and HMIs, and can be deployed to numerous processing targets such as FPGAs, real-time controllers, and PCs, is crucial when developing an integrated system such as this."

- Darcy Bachert, CEO, Prolucid Technologies, Inc.

The Challenge:
We needed to develop a subsea system to process and transmit data to the surface for control, logging, and analytics.

The Solution:
We took advantage of the unrivaled integration capabilities and extreme ruggedness of the CompactRIO platform to develop a control system that could perform motion control and high-speed video and sensor data capture in a harsh environment.

Author(s):
Marcus Jacob, Systems Integrator - Prolucid Technologies, Inc.
Darcy Bachert, CEO - Prolucid Technologies, Inc.

Overview

Welaptega is one of the world’s foremost innovators in offshore asset inspection and relies on critical non-destructive video inspection and sensor data to quantify degradation and damage to components. Welaptega deploys subsea mooring line inspection systems to assess the current physical condition of the asset and identify operational risk per the condition of system components.                                                  

Welaptega needed a solution that could perform motion control, high-speed video, and sensor data capture with the capability to process and transmit data to the surface for control, logging, and analysis. To continue advancing its inspection capabilities, Welaptega sought a technology partner who could not only help with enhancements to core products but who would also advise on the right technologies to help build out the next generation of innovative inspection product development. To achieve this, Welaptega required partners with deep expertise in embedded and vision software development who could integrate the solution with existing systems, so the company turned to NI and Prolucid.

Our Approach

Prolucid’s successful history combined with deep expertise in embedded and vision software development for critical non-destructive inspection test systems provided Welaptega with the confidence that we could deliver a solution. In addition, our agile approach to software development helped us meet Welaptega’s critical application requirements while also having the flexibility to showcase the changing technologies and innovations in subsea measurement and inspection.

Working together with Welaptega, we helped define the project scope including NI hardware and software platforms. The CompactRIO platform was a perfect fit for this application due to its rugged and compact form factor and ability to perform high-speed signal acquisition and processing, along with advanced motion control.

Our solution has two main components:

  • CompactRIO serves as the embedded system that operates subsea to acquire and process sensor data, as well as perform advanced motion control.
  • A PC-based control station located at the surface controls the subsea unit and conducts the vision inspection.

Embedded System

The CompactRIO hardware is part of the Semi-Autonomous Mooring Inspection Robot (SAMIR) that Welaptega operates by deploying it underwater using a subsea remotely operated vehicle (ROV). Once in place on a mooring line, we can operate it remotely for motion control and data acquisition. The sensors include pressures and temperatures for calculating water depth, an encoder for positioning, and a stepper motor for its main drive mechanism. It relies on the embedded FPGA inside CompactRIO to run a high-speed, multiplexed analog input array of 128 magnetic sensor points. These sensor points can detect magnetic flux leakage (MFL) with the ability to identify and quantify broken wires and the extent of corrosion in both sheathed and unsheathed cable lines. This design paired with the speed of the FPGA saved significant costs by reducing the physical input channels and modules necessary, since fast multiplexed switching could replace that.

We used the CompactRIO hardware to keep the equipment small and inexpensive, yet still capable of scanning a high number of sensors. We achieved this by using 250 KHz+ C Series modules and performing multiplexed digital switching, all within the FPGA of the CompactRIO hardware. Welaptega could keep the hardware package small and affordable, yet still achieve the overall sample rates needed for 1 mm scan accuracy, while travelling at speeds up to 0.5 m/s.

We use the motion control to move SAMIR into place along a line and set the speed and direction during a scan, which ensures the MFL, depth, and video data all correlate with the linear position of the tool.

Vision Inspection and Remote Station

The vision acquisition hardware is at the surface, using five camera feeds from the subsea SAMIR tool. A LabVIEW application runs on the control station and allows live monitoring and calibration of the cameras, as well as high-speed image analysis. We use TCP communication to transfer all data to the surface for graphing, logging, and analysis. The operator controls the equipment, views of the data acquisition, and live streams of all the cameras. The vision component includes various image processing and analysis tools that capture video-based cable diameters and panorama image stitching of the cable’s unwrapped circumference. In addition, complete recording, playback, and reprocessing are available with any of the live data.

Results

The solution we built using LabVIEW and NI vision for visual inspection, and CompactRIO for motion control and high-speed data capture, solves Welaptega’s challenge of identifying the degradation and damage to components using high-speed data processing and real-time visualization. Our solution based on NI hardware and software empowers Welaptega operators to view all the captured data in real time at the surface on a custom-developed user interface, while also logging the data for post-job playback and analysis.

We created the necessary LabVIEW applications to give operators motion control of their subsea equipment, while acquiring data from a large number of magnetic sensors, which are multiplexed into a high-speed capture solution using the FPGA on the CompactRIO. This is performed simultaneously with the vision inspection, using five cameras, showing critical real-time data to the operator about the health of the mooring line under inspection.

As part of the project, we also developed full playback capability into the application, which delivered two major benefits:

  • Welaptega has complete post-job playback control of data sets and can adjust the vision processing parameters for further analysis to help identify defects.
  • Welaptega could leverage distributed development by saving test runs and playback at the development site. This increases the development velocity by empowering developers to quickly run simulated scans without having to deal with hardware and setup times.

Overall benefits of the application are that it:

  • Offers remote motion control, scan path planning, and precise movement of an underwater tool, which was previously unavailable
  • Captures and streams high-speed MFL data at 250 Mhz from 128 sensors, delivering a huge amount of information, with a small footprint and relatively low-cost measurement systems
  • Calculates a real-time diameter measurement, using edge detection through the cameras, and performs image stitching algorithms to present data that physical sensors cannot measure directly
  • Records with full playback and reprocessing capabilities, five simultaneous video streams, all correlated and timestamped along with the sensor data
  • Provides an easy-to-use application interface for capturing project data and job measurements, and for tagging and processing any of the video and sensor data

Conclusion

Prolucid and NI provided Welaptega with a system that can detect degradation and damage of subsea mooring lines using non-destructive vision inspection and data acquisition, mounted to an unmanned ROV. Our Embedded Control Specialty and Vision Specialty certifications from NI made quick and reliable transition from prototype to complete system easier. We worked with NI’s integrated ecosystem of hardware and software to create a complex and high-quality solution that Welaptega trusts will provide them with the best data quality, analysis, and control available.

 

Author Information:
Darcy Bachert, CEO
Prolucid Technologies, Inc.
Tel: 416-840-6634

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