Development and Implementation of Algorithm for Synthetic Steering of Acoustic beam

Project Title

Development and Implementation of Algorithm for Synthetic Steering of Acoustic beam

Project Area of Specialization Electrical/Electronic EngineeringProject Summary

Acoustic beam suffers from losses and absorption when transmitted in any channel. This makes it difficult to concentrate the intensity of beam in a particular direction for various applications. Beam steering can be used to steer  main lobe of beam so that the intensity can be focused in the required direction for a particular application. An algorithm for electronic beam steering will be developed and implemented for both terrestrial and underwater environment in our project. The hardware will consist of a planar array of piezoelectric transducers fabricated after calculations and considerations of important parameters. This array will allow the sound intensity to be focused in shape of a beam and beam will be electronically steered in the required direction using the concept of phase delay between the successive elements of an array. The algorithm and results will be verified by real time signal analyses on MATLAB which will show greatest intensity at the desired angle. Major advantage of this over manually steering the sound source is that it is quick and efficient, doesn’t generate any self radiated noise and requires no mechanical power. This approach and hardware is an innovative way by which we can solve existing problems which require focusing both on surface and water. Furthermore since sound is the only feasible medium by which we can communicate in water, our project can also be used to explore the underwater environment.

Project Objectives

The main objective of this project is to design and fabricate a sensor array consisting of piezoelectric transducers which will be able to electronically steer an acoustic beam over the azimuth plane. A lot of applications require the intensity of sound to be focused and that losses should be minimal. Major problem which arises when transmitting sound is that it suffers from distortion and loss of intensity when propagating whether on surface or water. Hence the intensity of sound may not enough for a particular application. Our objective is to cater this problem and allow the sound intensity to be focused in the shape of a beam through the formation of an array. A sensor array is a combination of transducers arranged in a geometrical pattern which forms an acoustic beam through the phenomena of constructive and destructive interference of the sound waves. Once the sound intensity is focused through a beam, we will electronically steer it so that intensity can be further focused at a particular angle.

We will be using method of electronic steering instead of manual steering. Manually steering the sound source generates a lot of self-radiated noise, uses mechanical power, is inefficient and takes a long time whereas electronically steering the beam doesn’t require any mechanical power, it is quick , doesn’t generate any self-radiated noise and is an efficient method. The algorithm that we will use to steer the beam relies on time delay. A calculated time delay will be given to a group of transducers in the array which will shift the interference pattern and the main lobe of the beam will get steered. Our project can be used in many applications and can be a breakthrough in solving many of the existing problems.

Project Implementation Method

First process in implementation was thorough research and study to get familiar with basic concepts of behavior of sound on surface and in water. It was decided to go for simulations first so that important parameters and challenges can be analyzed. A 4x4 planar array was designed using piezoelectric transducers on MATLAB. The array is in the shape of 4 x 4 matrix and transducer spacing was calculated using the formula d = 0.5? . After these calculations  array was simulated for both terrestrial and underwater environment. The beam was formed and steered in the required direction.

For hardware part, piezoelectric transducers were carefully fixed on a PCB sheet after carefully marking the dimensions. Spacing between transducers was same as kept in simulation. After the array was fabricated, steering algorithm was needed to be implemented.  Method of electronic beam steering was preferred because manual steering generates a lot of self-radiated noise and its extremely inefficient. Electronic beam steering relies on time delay or phase difference between the individual elements. The interference pattern shifts due to delay and main lobe gets steered according to the angle required. Time delay was calculated using ?t=(dsinØ)/c where d is spacing between the elements, Ø is the angle in which the beam is to be steered and c is the speed of sound. The calculation was made for an angle of 45 degrees for both the terrestrial and underwater environment and time delay was calculated. We grouped four transducers to give them same delay as the number of ports of Arduino are limited and it was impossible to give a separate delay to each and every single transducer. Using DAQ card will allow a separate delay for every single transducer as DAQ card has a greater number of ports.

After this a complete experiment was designed to verify the algorithm. For testing on surface, the array was kept stationary and three laptops were used as receivers which were kept at angles of 45, 0 and -45 degrees with the centre position being 0 degree. The signal was given through Arduino and a sound beam was generated and its intensity was measured at the three angles stated above. Highest intensity was recorded at 45 degrees which showed that our implementation was accurate. We are currently working to implement this experiment in water. Three microphones can be used as receivers and they can then be wired to the laptops on the surface where real time signal analyses can be performed on MATLAB as performed for surface. However  array and microphones have to be properly sealed and made waterproof  before testing. The array can be sealed by fixing it in an acrylic box and drilling the box for wiring .The drilling holes can then be sealed with epoxy glue. The signal can be given through Arduino after changes in the code for  new calculated time delay and a sound beam will be  generated. The result will be somewhat similar to results on surface. Maximum intensity will be recorded at 45 degree

Benefits of the Project

The major benefit of this project is that it will be an innovative solution developed and manufactured locally which will result in reduced cost. This can help to solve the existing problems our country is facing. The most recent problem which occurred in Punjab was that the highways had to be closed due to foggy conditions. In economic crisis Pakistan is at the moment ,we can’t afford our economic activity to be stopped especially through roads. To solve this problem we can install our system in front of a vehicle and it will scan or sweep through an area in front of the vehicle. It will alert the driver if there’s an obstacle in front of  vehicle and the driver can slow down. This can help prevent accidents and continue the economic activity.  

Another application in which our system can be used is in non destructive testing . The hardware can help to simplify inspection problems particularly for structures having complicated geometries. From a single fixed position, the beam can be swept like a searchlight throughout the object, pinpointing the location of cracks and flaws. This is a far less labor intensive approach and may eventually lead to faster inspection times, as well as more accurate assessment of the damage in the material.

Finally our product can be used for underwater exploration and monitoring. Since acoustic medium is the only medium by which we can communicate in water, we can use the acoustic beam to detect an underwater target. The beam can be electronically steered in water and a target can be detected upon the reflection of the beam using direction of arrival algorithm. This can be used for security purposes as our system can be deployed in the form of sensor networks. It will help to electronically scan the underwater area and detect underwater enemy vessel. This will help to protect vital assets located along the coastline such as oil rigs and nuclear powerplant

Technical Details of Final Deliverable

Final deliverable of our project will consist of a 4x4  planar array which will be fabricated from piezoelectric transducers. There will be basically two arrays each for terrestrial and underwater environment. The only parameter the two arrays will differ from each other will be the transducer spacing between the elements. This is because speed of sound in air is 330 m/s where as in water it is 1500 m/s. This leads to a different wavelength in both the channels and hence different spacing which is calculated by 0.5 ?. The transducer spacing for the terrestrial array will be 0.033m or 3.3 cm whereas spacing for underwater array will be 0.025m or 2.5 cm.

The signal to the array will be given at 5khz which is the resonant frequency of the transducers we have used and it will be given in the form of PWM waves from Arduino’s PWM port. For giving the time delay signal separately to each and every single transducer instead of giving it in groups, we can use a DAQ card which has greater number of ports and it will allow us to generate a more accurate result.

The Final deliverable product will be able to electronically steer the acoustic beam in the azimuth plane of 180 degrees in the required direction. The range will 5 to 10m however it can be improved if good quality transducers are used.

Final Deliverable of the Project HW/SW integrated systemCore Industry OthersOther Industries IT , Transportation , Security Core Technology OthersOther TechnologiesSustainable Development Goals Industry, Innovation and Infrastructure, Life Below WaterRequired Resources

Item Name	Type	No. of Units	Per Unit Cost (in Rs)	Total (in Rs)
			Total in (Rs)	77500
Piezoelectric Transducers	Equipment	50	200	10000
PCB Sheet	Equipment	4	300	1200
Arduino	Equipment	2	1500	3000
DAQ Card	Equipment	1	40000	40000
Microphone	Equipment	3	5000	15000
Wiring	Miscellaneous	10	100	1000
Breadboard	Miscellaneous	2	200	400
Sealing	Miscellaneous	4	1500	6000
Impedance Matching Oil	Miscellaneous	1	300	300
Epoxy Glue	Miscellaneous	2	300	600