09-05-2011, 12:15 PM
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TITLE
“BUS IDENTIFICATION SYSTEM FOR VISION IMPAIRED”
AUTHORS
V.APARNA VALLI B.V.H.H.SUDHEER
Abstract
Many commercial products developed allow those with disabilities to substantially improve their quality of life.The use of these devices allows the user to experience the freedom of certain aspects of life such as mobility, communication and other fundamental tasks. Examples of such solutions include cochlear implants, prosthetic limbs and text-to-speech devices. The BEACON follows in this same spirit, by providing visually impaired persons (VIPs) the freedom to independently commute via public bus transportation.
Through the use of BEACON transmitters placed on local buses, VIPs are able to safely catch buses with the aid of a portable handheld device and an audio and tactile interface. The wireless communication system between the transmitter and the portable receiver can be achieved through a number of current technologies. With more exotic approaches like Bluetooth still maturing in terms of financial and performance viability, the cheaper and more ubiquitous approach of radio frequency technology points towards a more feasible solution that can be produced at a reasonable cost for either the direct purchase by VIPs or a government subsidised initiative.
With the aid of the current bus transportation system, the BEACON transmitter is able to filter existing vehicle identification information for retransmission to a nearby VIP. The BEACON receiver is thus able to identify buses and their corresponding routes, and consequently inform the VIP of the bus‘ imminent arrival.
For the purposes of the BEACON prototype, communication is facilitated through FM transmissions at around 90MHz (within the commercial FM broadcast range). In addition, the solution attempts to resolve the problem through one-way communication from bus transmitterto handheld receiver. This project has the potential for vast improvement by implementing a duplex communication system, whereby the bus driver is able to identify the presence of VIPs and vice versa. In this way, the process of catching a bus can be further streamlined for efficiency, convenience and safety.
Activites and goals
The proposed solution involves the development of a device which allows VIPs to detect the arrival of particular buses. To achieve this, each bus will transmit its route information, while a handheld receiver will be used to notify the VIP through audio and tactile interfaces.
On completion of this project, VIPs will be able to catch public buses with the same ease, convenience and safety of the average commuter. As visual cues no longer constrain the distance required to identify a bus, VIPs will benefit from the additional notification time. Such a system will directly influence the quality of life of VIPs, by providing the freedom to travel independently.
The complete scope of the project includes the tasks of identifying, catching and de- boarding a bus; this thesis will only be involved in facilitating the communication required for bus identification
implementation Options
Strategic Options for Communication
In order to solve the problem in consideration, we must start with the user requirement of providing audio notification and then work backwards in an attempt to achieve the desired outcome. The five stages of the development process are shown
in Figure 4-1.
It can be seen that the above situation involves the one-way transmission of data
from bus transmitter to VIP receiver. This approach has been guided by the known fact that BCC buses already transmit their details. However, this is not the only approach that can be taken. The three options for communication are detailed below.
Stage 1: Acquisition of Bus Information
Stage 2: Transmission of Bus Information
Stage 3: Reception of Bus Information
Stage 4: Processing of Bus Information
Stage 5: Audio Output for VIP Interaction
Figure 4-1: Stages of the Actual Development Process
Approach 1: VIP Carries a Receiver œ Bus Carries a
Transmitter
¢ Advantage: An attractive approach if it is possible to receive the transmitted
VIT signal.
¢ Disadvantage: VIPs will need to locate the bus once it has been identified.
This becomes more difficult when there are multiple buses waiting at a common bus stop.
Approach 2: VIP Carries a Transmitter œ Bus Carries
Receiver
¢ Advantage: Bus drivers will know if a VIP is in the vicinity and is looking to catch that particular bus. This approach solves the problem with multiple buses, as bus drivers can find a VIP even though a VIP cannot identify a particular bus from a group of possible buses.
¢ Disadvantage: VIPs have no indication of when and if the bus is arriving.
Approach 3: VIP and Bus Carry a Transceiver
¢ Advantage: Inherits the advantages and overcomes the disadvantages of the first two approaches.
¢ Disadvantage: Requires the development of two transceivers. This increases the cost of production and may affect the financial feasibility of the product. It also significantly increases the complexity of the project.
selection of Communication Approach
It can be seen that the last approach involving a transceiver pair would be the most attractive option in terms of providing the best service to VIPs, whilst solving the
—multiple bus“ problem. Unfortunately, the development of such a product would require more time than is available for this particular project. The most suitable approach is the first, where the bus has a transmitter and the VIP has a receiver. It provides better service to the VIP than the second approach, as the VIP is given some indication of the arriving bus.
In all communication approaches, it can be seen that either the bus and/or VIP carries
a device which acts as a beacon to the other. The system will therefore be called the
BEACON system.
Given the choice of communication approach, it can be seen that the development stages in Figure 4-1 still applies. This structure can now be used to produce different approaches for actual development.
VIT-Integration
stage 1: Acquisition of Bus Information
If the signal transmitted by the VIT can be reliably received by a portable device at a distance of around 50 metres, then the acquisition and transmission stages will be satisfied in one fell swoop.
Stage 2: Transmission of Bus Information
As previously mentioned, this particular stage has been covered by the VIT.
Stage 3: Reception of Bus Information
A BEACON receiver needs to be developed which is able to receive the signal that is already being transmitted. Details about the existing transmission scheme is required.
Stage 4: Processing of Bus Information
The received signal needs to be decoded according to the encoding method employed by the existing VIT. The decoded information must then be processed for audio output in the next stage.
Stage 5: Audio Output for VIP Interaction
Once the received signal has been decoded, the data can be used to facilitate the audio interface. This stage forms the scope of a separate thesis project; hence the design will not be considered in this report. To facilitate autonomy between the two theses, a LCD display or PC interface should be used to visually demonstrate the completion of Stage 4.
approach 2: Retransmission of Information
Stage 1: Acquisition of Bus Information
If the VIT signal cannot be received, the data passed onto the VIT can still be intercepted through a RS-485 tap and processed for retransmission via a separate BEACON transmitter.
Stage 2: Transmission of Bus Information
A BEACON transmitter needs to be developed which is able to send the bus information to a portable handheld receiver.
Stage 3: Reception of Bus Information
A BEACON receiver needs to be designed in tandem with the newly designed transmitter.
Stage 4: Processing of Bus Information
The received signal needs to be processed for audio output in the next stage.
VIT-Integration Approach
An integrated system using bus VITs is a highly desirable solution. As the BEACON receiver would be the only unit requiring development, the solution becomes technically and financially attractive. With the VIT transmitting a 400kHz ASK signal
at 4800 baud, the receiver must have the following attributes.
¢ A suitable antenna to receive the signal.
¢ A filter to suppress unwanted signals.
¢ An ASK decoder to convert the analogue data to digital.
¢ A microcontroller to decode the digital data.
Figure 5-1: Development Blocks for the VIT-Integration Approach
Antenna Filter ASK Decoder Data Decoder
During development, the success of each stage must be verified before the next
stage can be investigated. This particular engineering practice ensures that problems can be isolated and investigated without the influence of problems in other stages. The design of each development block (including test procedures) is discussed below.
Stage 1: Antenna Design
The most critical stage in the VIT-Integration Approach involves the reception of the existing signal. The specifications in Chapter 3 indicated a maximum notification distance of 50 metres.
Assumption: It is assumed, for now, that the time from signal transmission to VIP notification is minimal.
It is known that the VITs have been designed to transmit their signal via induction. In fact, the system has been designed in such a way that the transmitted signal cannot
be received by antennas in adjacent road lanes; even with the transmitter placed 20
feet above the road.
It is possible that the VIT is also producing a propagated signal as a fringe effect. Although it is highly unlikely that that the signal can be received 50 metres away, the possility is certainly worth investigating.
Figure 5-2: Illustration of Existing VIT System
Road Receivers
Signal Not
Detected In
This Lane
Signal
Detected
Signal Not
Detected In
This Lane
BUS
Test Procedure: A loop antenna (eg. diameter of 8 cm, with an unwound length
equal to the signal‘s full wavelength) should be used to test signal reception with a spectrum analyser. If the VIT signal cannot be received by the antenna, then the rest of the design for the VIT- Integration approach can be abandoned.
