Customer SolutionsUsing Compact FieldPoint for Underwater Crawler Control and Data Acquisition
Author(s):Baskar Ceri, Apna Technologies & Solutions Private Limited; Unnikrishnan ., National Institute of Ocean Technology India; Vishwananth B O, National Institute of Ocean Technology India; Binu Balakrishnan, National Institute of Ocean Technology India; Senthil Raj Desappan, Apna Technologies & Solutions Pvt Ltd; Valliappan M, Apna Technologies & Solutions Pvt Ltd
Industry:Research, Water/Wastewater
Product:Compact FieldPoint, Data Acquisition, FieldPoint, LabVIEW, LabVIEW Real-Time, PXI/CompactPCI
The Challenge:Building the data acquisition and control system for an underwater crawler that can operate on the seabed up to a depth of 600 meters.
The Solution:Using National Instruments LabVIEW, PXI Real-Time and Compact FieldPoint Real-Time Modules to develop the system.
NIOT Builds Crawler Collects Seabed Material The National Institute of Ocean Technology (NIOT) developed an underwater crawler for mining at a depth of 600 m that travels on the seabed, fitted with equipment for cutting, collecting, and transporting material. Launched from a ship, we control all the operations via a local subsea PC in the crawler, which acquires data from various underwater sensors, taking commands from the operator in the ship control room using remote data link to the control room PC, and controls the various output devices in the crawler both in manual and automatic mode. We established the communication between the ship control and subsea PC using a multimode fiber optic link. To acquire various signals, such as speed, direction, and temperature readings from crawler, we use user interface screens present in the ship control room. The control room unit gathers the appropriate control inputs from the user in the control console and then translates and communicates the same to the underwater system. To be flexible, we designed the system so that the communication between crawler unit and ship control room is through TCP/IP (default communication mode), and if any communication failure occurs in TCP/IP, the communication automatically switches to serial mode. If TCP/IP communication reconnects, the communication mode switches back to TCP/IP. The system is so flexible that at the time of the main as well as backup communication failure between crawler and ship control room, the crawler is maintained at a user-specified safe position until communication resumes. System Description We developed the data acquisition and control system for the underwater crawler using the following:
The compact embedded system in the crawler in is a Compact FieldPoint-based Real-Time system comprising of the following:
The underwater crawler consists of the following:
Crawler Control and Data Acquisition We chose NI Compact FieldPoint for the underwater crawler control system because of its ruggedness and compactness. We implemented a Compact FieldPoint system comprising of the cFP-2020, the high-end embedded controller with 512MB compact flash memory running a LabVIEW Real-Time program, cFP-RTD-122 for temperature inputs, cFP-AI-110 for analog inputs, cFP-AO-210 for controlling the drive and the direction providing PID outputs, cFP-DO-403 for digital inputs, and cFP-CTR-502 for speed inputs. We control all the crawler components using the Compact FieldPoint real-time controller and Compact FieldPoint I/O modules. We launch the crawler along with the Compact FieldPoint modules into the seabed at a depth of 600m from ship control room. The PXI system comprises of PXI-1002 chassis with PXI-8176RT embedded controller running a LabVIEW Real-Time application, PXI-6508 to take the digital inputs from the user control panel, and PXI- 6031E for the analog inputs on the control panel. Crawler Control Module: This is the main controller program running the Compact FieldPoint real-time controller in the crawler. We wrote this module in LabVIEW Real-Time. This module continuously acquires data from various sensors in the sensor head and performs a two-way communication between a PXI real-time controller present in ship control room. PXI and Compact FieldPoint real-time controllers communicate through TCP/IP. When TCP/IP fails, the communication switches to serial mode. We designed the module in such a way that when it receives any command from a PXI real-time controller, the module checks for critical interlock conditions specified by the user before actuating the corresponding outputs from the Compact FieldPoint modules. We maintain separate data log, event log, and error log files in the Compact FieldPoint memory when there is no communication between the ship and the crawler. Once the communication is re-established between PXI and Compact FieldPoint, we upload the stored log files to PXI. This module also brings the crawler to safety position if there is no communication between the crawler and the ship control room for a specified time period. This module runs the required PID algorithms to control the crawler direction, speed, and slip control between the two belts of the crawler in the auto mode of operation. Communication Module This module is the heart of all the communication that happens between various modules – between the master and slave PC, the PXI controller and Compact FieldPoint controller, and the master PC and PXI controller. Most of the communication is based on TCP/IP. Between the PXI controller and Compact FieldPoint Controller, there is the redundant communication built-in the module. TCP/IP communication is the default mode of communication, and if there is any error in the TCP/IP communication, the module switches automatically to then serial (RS232) mode without losing any control from the ship. The module continuously verifies whether TCP/IP communication re-establishes and when TCP/IP starts working, the mode of communication automatically switches back to TCP/IP owing to its high speed of data transfer. This module is responsible for the automatic switching between TCP/IP and serial mode of communication. Data logging Module The data logging module runs in the master PC, PXI controller, and Compact FieldPoint controller. The master PC contains all the data stored as per the date of operation. The PXI controller contains all the data as a backup. Compact FieldPoint stores the data only when there is no communication between the Compact FieldPoint controller and the PXI controller. When communication gets re-established, these files stored at the Compact FieldPoint controller are later transferred to the PXI controller. We maintain separate data, error, and event log files are maintained. The data log contains all the data from the sensors from in the crawler. The error log contains all the errors during the operation. And the event log contains all the events, like any action performed by the user in the ship control panel or in the master/slave user interface, the corresponding events in the crawler, along with the time. The system performs data logging as per the log rate (in seconds) specified by the user. The user can read the stored data anytime using the review module. Conclusion We built the underwater crawler data acquisition and control system using the NI virtual instrumentation concept. Using LabVIEW, PXI Real-Time, and Compact FieldPoint Real-Time, we built the underwater crawler data acquisition and control system using the application in the most effective manner. The system not only acquires all the signals from the crawler, which is at a depth of 600m in the ocean bed, it also controls the crawler. Finally, we reduced the development time and have the option of future enhancements. For more information, contact: Baskar Ceri Managing Director Apna Technologies & Solutions Private Limited M2 Industrial Estate Guindy, Chennai 600032 Tel: +91-44-22321202 Fax: +91-44-22331107 E-mail: baskar@apnagroup.com |
