DESC:FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)

Title: DESIGN AND DEVELOPMENT OF TRANSCEIVER ELECTRONICS AND DIGITAL METHOD FOR ESTIMATION OF PARAMETERS OF ELECTROMAGNETIC LOG

APPLICANT DETAILS:
(a) NAME: BHARAT ELECTRONICS LIMITED
(b) NATIONALITY: Indian
(c) ADDRESS: Outer Ring Road, Nagavara, Bangalore 560045, Karnataka, India

PREAMBLE TO THE DESCRIPTION:
The following specification (particularly) describes the nature of the invention (and the manner in which it is to be performed):

DESIGN AND DEVELOPMENT OF TRANSCEIVER ELECTRONICS AND DIGITAL METHOD FOR ESTIMATION OF PARAMETERS OF ELECTROMAGNETIC LOG

FIELD OF INVENTION:
The present disclosure relates to the design and development of transceiver electronics and digital method for estimation of parameters of electromagnetic log in a marine vehicle wherein the parameters include speed, direction & distance.

BACKGROUND OF THE INVENTION:
The following background discussion includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication expressly or implicitly
A conventional method of designing the hardware is using a separate ac power supply for excitation of sensor coil as transmitter and analog receiver. This method uses transformer, servo motor, synchro sensor, dial, integrator with time motor as receiver hardware for estimation of speed and distance.
In a conventional arrangement disclosed in US patent US3362220, “Electromagnetic Log”, measures speed and distance of a ship by sensing the velocity of the water with respect to the hull. The electrical signal of a rodmeter is amplified with transformers and transferred to speed servo which in turn is connected mechanically to synchro transmitter, speed dial, integrator with time motor for estimation of speed and distance. A separate ac power supply is used for excitation of sensor coil as transmitter.
Another approach disclosed in US 4079626, “Electromagnetic Flow Meter”, mainly claims about the design of fluid flow meter transducer design, placement of electrodes, transducer housing structure & velocity of fluid. It mainly consists of analog based transmitter and receiver circuit, amplifier for receiving the transducer signal, which in turn feeds the signal to synchronous detector (motor) for estimating the velocity of fluid.
In another arrangement disclosed in US 4472966, “Marine Speed Log”, it aims to provide speed, distance and direction in both salt and fresh water without any change in calibration. It mainly claims for Speed log sensor, Analog based transmitter and receiver circuit without the consideration of water properties like salinity, temperature, pressure of sea water, divide mode, no correction of statically induced emf with respect to operating frequency of speed log etc.,
Hence, there is a need to design and development of transceiver electronics and digital method for estimation of parameters of electromagnetic log in a marine vehicle wherein the parameters include speed, direction & distance.

OBJECTIVES OF THE INVENTION:
The primary object of the present invention is to overcome the problem stated in the prior art.
Another object of the present invention is to provide a transceiver electronics and digital method for estimation of parameters of electromagnetic log in a marine vehicle wherein the parameters include speed, direction & distance, considering the marine water properties like pressure, salinity, temperature etc. From other sensor at regular intervals for different dive modes.

SUMMARY OF THE INVENTION:
The present invention provides a system for estimating parameters of electromagnetic log in a marine vehicle comprising:
a) a controller based two channel transmitter card;
b) at least two channel receiver card; and
c) a FPGA based card that monitors and manages the transmit and receive cards, and computes speed, distance and direction;
wherein, a communication system is implemented between the transmit and receive cards to manage the health status.
In an embodiment, each transmitter card has two channels where one channel is meant for Log rod (Fixed probe) Sensor’s excitation and another for Flush Probe Sensor’s excitation.
In an embodiment, the transmitter card takes input of 48V DC and converts it into 57Vrms, 64Hz AC signal which is connected to the sensors via a power transformer (64Hz).
In an embodiment, the transmitter card reads the pressure sensor data and transfers it to the control card for selection of appropriate probe.
In an embodiment, the receiver card with the controller card includes a preamplifier, filtering circuit and ADC which is plugged on to a SoC based controller board.
In an embodiment, the digitized data from ADC is captured in the controller card which has SoC with both FPGA and processor on the same chip.
In an embodiment, the ADC is having a serial peripheral interface (SPI) for data transfer and the digitized data is captured by FPGA over SPI interface at a rate of 1.6MHz sampling rate.
The present invention provides a method for estimating parameters of electromagnetic log in a marine vehicle comprising:
automatically selection of probe (fixed and flush probe) based on speed and pressure data, reading the pressure sensor by a data transmitter card reads and transferring this to the control card for selection of appropriate probe, passing the information regarding the probe selection on to the transmit card and receive cards for enabling only the corresponding channels.

DETAILED DESCRIPTION OF DRAWINGS:
To further clarify advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of their scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings in which:

Fig. 1: illustrates a card level connection diagram.
Fig. 2: illustrates a block diagram of 2 ch- rx with controller card.
Fig. 3: illustrates a block diagram of 2 ch- tx card.
Fig. 4: illustrates a flow chart for digital method of estimating the speed of marine vehicle.
Fig. 5: illustrates a flow chart for digital method of rms computation of pick-up voltage.
Fig. 6: illustrates a flow chart for digital method of direction detection.

DETAILED DESCRIPTION:
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.
The terms “comprises”, “comprising”, “includes”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, device or method that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device or method. In other words, one or more elements in a system or apparatus proceeded by “comprises... a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or method.
The Emlog sensors are hull mounted sensors with 2 varieties. Each differing in their electrical and mechanical characteristics. The fixed probe sensor protrudes out of the hull whereas the flush sensor is attached to the hull.
Power to both the sensors is provided from the transmit (Tx) card (independent channels) and the signal received (pick up signal) from both the sensors is processed independently through the receiver (Rx) with controller card. Pressure sensor, water salinity, Temperature data are fed to controller data as shown in fig1.
The connection to sensors and communication to the External system, internal communication between TX & RX is as shown in fig1.
Each TX card has 2 channel. One channel is meant for Log rod (Fixed probe) Sensor’s excitation and another for Flush Probe Sensor’s excitation. The card takes input of 48V DC and converts it into 57Vrms, 64Hz AC signal which is connected to the sensors via a power transformer (64Hz) as shown fig 3. It has additional features of programmable frequency and amplitude of excitation signals to the underwater sensor. It reads the pressure sensor data and transfers it to the control card for selection of appropriate probe. The information regarding the probe selection will then be passed on to the transmit card and receive cards for enabling only the corresponding channels as shown in block diagram of TX card fig 3.
As shown block diagram of Rx with controller card fig 2, hardware realized for receiver of includes a preamplifier, filtering circuit and ADC which can be plugged on to a SoC based controller board. The digitized data from ADC is captured in the controller card which has SoC with both FPGA and processor on the same chip. ADC is having serial peripheral interface (SPI) for data transfer and the digitized data is captured by FPGA over SPI interface at a rate of 1.6MHz sampling rate.
As per Faraday’s principle induced voltage is directly proportional to the speed of the vessel. The input signal pertaining to supply for the electromagnet to the sensor is a low frequency AC sine wave of 57V RMS and 64Hz frequency. In this contest this signal is referred to as the Excitation signal. The excitation signal produces an alternating magnetic field of 64Hz, which is in phase with excitation signals current. The alternating magnetic field induces an alternating EMF in the seawater as the vessel translates, the frequency of which is same as that of the excitation signal. This induced EMF signal is termed as the receive signal or pick up voltage. The receive signal has a differential output whose amplitude is of the order of microvolts.
Typically, the amplitude of induced EMF depends upon the sensitivity of the sensor which is generally of the order of 10 - 200 uVpp/knots. Here as the vehicle moves continuously, the induced EMF generated is monitored and stored to compute the RMS value of voltage. The RMS computation is performed at ARM processor side of SoC The data captured at FPGA side is continuously transferred to ARM side through AXI DMA. The scheme is implemented in such a way that 32 samples are getting transferred to ARM side every 20 µs with each sample time stamped, as shown in Fig 5. At the ARM side RMS value is computed with the received samples at a rate of 8 times per second (Every 125ms). In the implementation discussed here, for each 20 µs time interval, 32 samples are received and therefor at every 125ms, 2 Lakhs samples are available to compute RMS value of pick-up voltage.
In the estimation of the speed of marine vehicle, there are several factors affecting the pickup voltage or received signal or sensor signal. Those are salinity, temperature of water, dive mode, Pressure etc.,
(Salinity of Marine water is important in electromagnetic logs because it directly affects the electrical conductivity of water.
Marine water has a negative temperature coefficient, which means that its electrical conductivity decreases as the temperature increases.
As pressure increases, typically its conductivity also increases. In general, an increase in pressure tends to increase the ion concentration and mobility within the sea water, leading to higher electrical conductivity.)
Therefore, by considering the marine water properties like pressure, salinity, temperature etc. From other sensor at regular intervals for different dive modes, the coefficient in the range 0 to 1 is derived for estimating the true Pick up voltage, which is in turn is used for estimating the speed of marine vehicle as shown in flow chart Fig 5. Integration of speed with respect to time gives the distance travelled by the marine vehicle.
The direction of the vessel is estimated by comparing the time stamp of the peak amplitude of received sample of sensor signal (Signed data) (Va)with that of the excitation signal of the sensor (Vref) Depending on the excitation frequency of sensor signal, a direct relationship can be generated between time difference and angles as shown in flow chart Fig 6.
If Va is 180 deg out of phase with Vref, then direction of marine vehicle is Reverse.
If Va is in phase with Vref, then direction of marine vehicle is Forward.
Automatic selection of probe (fixed and flush probe) based on speed and pressure data. The transmitter card reads the pressure sensor data and transfers this to the control card for selection of appropriate probe based on the depth at which the vehicle is located. The information regarding the probe selection will then be passed on to the transmit card and receive cards for enabling only the corresponding channels. Control card communicates with transmit and receive cards to monitor and manage the health status of both the cards and the sensors.
In one embodiment, the hardware computes the speed of the marine vehicle by computing the RMS value of received samples over a time period where the samples are time stamped before processing.
Further, the hardware computes the direction of motion of the marine vehicle by a method called peak amplitude detection with time, through which phase of the received sample set is compared with the phase of the excitation signal set and is able to generate excitation signal for sensor, having the feature of programmable frequency and amplitude, thereby providing flexibility to generate desired excitation signal.
Further, the hardware is capable of exciting 2 underwater sensors at a time, with closed loop current control, where the closed loop current control mechanism ensures noise free signal excitation. It is capable of automatic selection of probe (fixed and flush probe) based on speed and pressure data and the communication between these manages the health status of the system.
The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the substance of the invention may occur to person skilled in the art, the invention should be construed to include everything within the scope of the invention.

,CLAIMS:We Claim:

1. A design and development of transceiver Electronics and Digital method for estimation of Speed, direction & distance of Electromagnetic Log in a marine vehicle comprising: a controller based 2 channel transmitter card along with an FPGA based two channel receiver card, where the FPGA card computes speed, distance and direction.
2. The digital method as claimed in claim 1, wherein the digital method of RMS computation on received samples for estimation of speed and distance of marine vehicle by storing the received samples with time stamp.
3. The digital method as claimed in claim 1, wherein the digital method for phase detection of received signals to estimate the direction of marine vehicle.
4. A compact transmitter hardware design capable of exciting 2 underwater sensors at a time, with closed loop current control comprising:
a) Transmitter card with additional feature of programmable frequency and amplitude of excitation signals to the underwater sensor.
b) Estimation algorithm for true speed, distance & direction, considering the water salinity, pressure and temperature at regular intervals.
c) Automatic selection of probe (fixed and flush probe) based on speed and pressure data. Transmitter card reads the pressure sensor data and transfers this to the control card for selection of appropriate probe. The information regarding the probe selection will then be passed on to the transmit card and receive cards for enabling only the corresponding channels.
d) FPGA card communicates with transmit and receive cards to monitor and manage the health status of both the cards and the sensors.
e) Multiple sets of transmit receiver and control cards can be used to add additional pair of sensors to the marine vehicle.