Underwater remotely operated vehicles (ROVs) play an important role in a number of shallow and deepwater missions for marine science, oil and gas extraction, exploration and salvage. In these applications, the motions of the ROV are guided either by a human pilot on a surface support vessel through an umbilical cord providing power and telemetry, or by an automatic pilot. In the case of automatic control, ROV state feedback is provided by acoustic and inertial sensors and this state information, along with a controller strategy, is used to perform several tasks such as station-keeping and autoimmersion/heading, among others. In this paper, the modelling, design and control of the Kaxan ROV is presented: i) The complete six degrees of freedom, non linear hydrodynamic model with its parameters, ii) the Kaxan hardware/software architecture, iii) numerical simulations in Matlab/Simulink platform of a model-free second order sliding mode control along with ocean currents as disturbances and thruster dynamics, iv) a virtual environment to visualize the motion of the Kaxan ROV and v) experimental results of a one degree of freedom underwater system.

This paper presents the improvement of an ultrasonic pulse generator for a pipeline inspection gauge (PIG), which uses 64 transducers for inspecting distances up to 100 km with an axial resolution fixed at 3 mm and variable speeds between 0 and 2 m/s. An ultrasonic pulse generator is composed of a high-voltage (HV) MOSFETs, driver logic and an HV power supply. We used a DC-HV DC converter device as the HV power supply because it reduces the size of the ultrasound system considerably. However, pipeline geometry and inspection effects such as hammer and shock cause a variable pulse repetition frequency (PRF), producing voltage drops, poor quality of the HV pulse generated, failures in the dimensioning of defects and damage to devices by over-voltage. Our improvement is to implement a control scheme to maintain the high quality of the HV regardless of the variable PRF. To achieve this, we characterized three transfer functions of the DC-HV DC converter, varying the connected load to 10%, 45% and 80%. For the characterization, we used the least squares technique, considering an autoregressive exogenous (ARX) model. Later, we compared three control schemes: (1) proportional-integral-derivative (PID) tuned by simultaneous optimization of several responses (SOSR), (2) PID tuned by a neural network (NN) and (3) PI tuned by the analytical design method (ADM). The metrics used to compare the control schemes were the recovery time, the maximum over-voltage and the excess energy when the shock and hammer effects happen to occur. Finally, to verify the improvement of the HV pulser, we compared the ultrasonic pulses generated for various frequencies and amplitudes using the pulse generator with and without the control scheme.

In this manuscript, we present a redundant data storage system based on NAND flash memory chips for in-line Pipeline Inspection Gauges (PIGs). The system is the next step for a technique that reduces data from 1,024 to 37 bytes by 80 transducers used for straight-beam ultrasonic inspection. Each inspection is costly, because PIGs check pipelines up to 100 Km, collecting data every 3 mm and reaching speeds of 2 m/s. These conditions require that the storage system must be redundant, and able to maintain a minimum data flow, thus avoiding bottlenecks. To achieve this, we analyzed the variables that influence the inspection process in real-time, and we structured our Flash Translation Layer (FTL) to eliminate the latencies generated by the computation of the Error Correcting Codes (ECC) and redundancy bytes. Our controller computes the ECC and redundancy bytes while it transfers the information to the cache register of the selected die in the memory chips. At the hardware level, we interleaved 8 NAND flash chips in a Redundant Array of Independent Disks (RAID) type-6 architecture. We tested the storage system considering the incorrect response of up to 2 chips and ensuring a throughput up to 7.28 MB/s. Finally, we expanded the analysis of the data flow, whereby this system is profitable for different pipeline diameters or compression techniques.Index Terms-Data storage systems, error correction codes (EEC), field programmable gate arrays (FPGA), NAND flash memory, parallel architectures, pipeline inspection gauge (PIG), reed-solomon codes (RS)

The present work shows the development of both a pulse-receiver circuit and acquisition circuit prototypes of ultrasonic signals for the measurement of thickness in oil pipelines using a Pipeline Inspection Gauge (PIG). The development parameters count with restrictions of space, sampling velocity and storage capacity, and besides they have to satisfy the norms applied in oil pipeline inspection by the PIG. The prototypes consist of several functional blocks; a pulsed circuit that excites the transducer generating a high voltage pulse of about -200V, a receiver circuit for the reception of the transducer signal, a filter and amplifying block, and finally acquisition and processing step for signals composed by one ADC, a FPGA and a microcontroller.

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