3.1 Project Results
3.1.1 Project Outcomes
The project has constructed a sonar system and an acoustic communication system using the software and hardware components described in Chapter 2. This Chapter will discuss the results of each of the systems.
One of the most significant advantages this project brings about is its low-cost compared to commercial underwater modems and drainage blockage detection systems. Table 3.1 lists out the costs of all components used for building these two systems. The costs are in the unit of Hong Kong Dollars.
Table 3.1: Project Component Cost
Component Cost (HKD) Unit
Texas Instruments F28379D Micro-Controller 300 2 LM380 Audio Power Amplifier IC 13.81 1
LM833DT Dual Channel Audio Amp 2.761 6
B18A001F Audio Transformer 80.60 1
PCB Boards Fabrication and Shipment 100
-Parasitic Components 16.8
-Batteries 135 4
This leads each system to have a total price of roughly HK$1370. In comparison to other current alternatives on the market, which can easily cost tens’ to hundreds’ of thousand Hong Kong Dollars, our system provides an a↵ordable and e↵ective alternative. By utilizing di↵erent components, we have been able to develop a system which can produce a comparable outcome, at a substantially lower price.
15
Project Development and Implementation 16 3.1.2 Sonar System Results
The blockage detection system is capable of utilizing sonar waves to e↵ectively detect and estimate the distance of any blockages within urban water supply systems. By transmitting sonar waves through pipelines and analyzing the received signal, we can e↵ectively estimate the location of any major blockages. As can be seen in Figure 3.1, a transmitted signal can be correlated against a received signal to e↵ectively determine the location of any such blockages.
Figure 3.1: Example Blockage (5m)
Although this system has only been tested in pipelines of up to 2 meters, due to the low cost of the system, it is highly scalable and is an a↵ordable alternative to current market options. By spanning these sensors in great numbers across urban pipelines, entire pipeline systems can be easily monitored remotely from a centralized point.
3.1.3 Acoustic Communication System Results
A communication bitrate of 1kbps has been successfully achieved across the 2m long water pipe. This is calculated from each bit being represented as 10 cycles of a 10kHz si-nusoid, which corresponds to 1ms of time per bit. Therefore, bitrate = t1
bit = 1000 bit/s.
Figure 3.2 shows an example of the received waveform from the modem containing a single ASCII character. In the example, the bit length has been used as 5 cycles, so the received wave(shown in the plot above) is convoluted with 5 cycles of the sinusoid to
Project Development and Implementation 17
Figure 3.2: Decoding received messages
generate the signal in the lower graph of Figure 3.2. The first maxima on receiving the training data of ¡111¿ is used as the first point for sampling and the convoluted signal is sampled every 5 milliseconds. The sample points are also marked on the graph, a high signal is treated as a binary 1 and a low is decoded as 0. Preliminary experimentation has shown to give perfect decoded results with no bit error.
3.2 Project Discussion
3.2.1 Limitations
The system has two main bottlenecks a↵ecting performance, range of blockage detection and communication bitrate. The current range of the blockage detection is 2m and the bitrate is 1kbps.
Achieving a higher range would require a higher power transducer to emit the acoustic impulses in order to overcome the attenuation of the signal in water. This attenuation is described mathematically by the equation for the link budget given below.
Preceived= Ptransmitted+ Pgain Ploss (3.1)
where P is the power of the signal measured in dB
Using transducers of higher power would be e↵ective yet extremely expensive and this would go against the objective of this project to develop this system at a low cost.
In order to improve the data transfer rate of the system, a more efficient modulation scheme would be needed. Using naive time-domain multiplexing as is being used now has several drawbacks in terms of efficiency. A better option would be to use frequency
Conclusion 18
division multiplexing(FDM) and in particular Orthogonal FDM(OFDM) that allocates channels of di↵erent specifically selected frequencies to minimize symbol and inter-channel interference.
3.2.2 Conclusion
To summarize, the system is e↵ective in providing a highly scalable, and a↵ordable solution as a non-destructive means of monitoring the quality of UWSS’ within urban environments.
The system operates by sending pulses through the water pipeline to check whether any blockages exist. If one exists, the system calculates the location of the blockage and transmits the information to a centralized user using the acoustic communication component of the system. Pipelines can therefore be monitored remotely, by collecting data from the receivers.
This concept can be extended to a wide variety of applications. One of which is in detecting faults and collecting information about the state of UWSS’. With the success of this application, huge losses in expenses and energy world wide could be saved on maintenance checks, leakage detection and blockage detection.
Another application exists in smart Building Management Systems. Information about the pressure, temperature, flow rate, leakage, blockage or any other fault in water and gas supply pipes in buildings could be monitored in real time. The smart monitoring system can be added to existing Building Management Systems, where monitoring of security systems, fire prevention systems, power supply, lifts, server rooms and pest control systems is done.
Smart pipelines is a concept for future cities and it is an upcoming field of intensive research. This project is just the beginning of an idea that can be magnified to cover every building and city in the world some day.
Bibliography
[1] United Nations. November 2014. URL http://www.un.org/en/development/desa/
news/population/world-urbanization-prospects-2014.html.
[2] Pan Zhengrong, Wang Chi, Han Xiao, and Yin Jingwei. Application of di↵erential amplitude and phase-shift keying in underwater acoustic communication based on orthogonal frequency division multiplexing. The Journal of the Acoustical Society of America, 133(5):3463–3463, 2013. doi: 10.1121/1.4806167. URL https://doi.org/
10.1121/1.4806167.
19