What problem the system is trying to solve
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Very often, it is difficult to locate shared resources, such as wheelchairs at a hospital, when they are needed most. This causes inconvenience and sometimes frustration to the patients, their caregivers and hospital staff. The root cause is: after the wheelchairs are used, they are not returned to the designated spots where other users can easily locate them.
How can technology be used to track the wheelchairs, so that the hospital staff can locate them and return them to the designated spots for other users?
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GPS, or Global Positioning System only works in outdoor environment where the microwave signal from the satellites can be received. RFID, or Radio Frequency Identification, requires the installation of huge “readers” all over the hospital compound. WiIFi tracking, based on the WiFi signal strength can be used, but this poses a security concern, as the small trackers to be placed on the wheelchairs will be in the same wireless network as the computers being used by the hospital staff.
Hence, a viable alternative is to use ZigBee.
Who the beneficiaries are
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Patients and their caregivers, for moving between cars/taxis and the hospital wards. Hospital staff, for improving service and operation efficiency.
How the system works
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ZigBee, based on IEEE802.15.4, is often used in WPAN (Wireless Personal Area Network), for wireless communication, wireless sensor network, automation etc. This innovation project, however, uses ZigBee for a different purpose: asset tracking. A ZigBee network consists of one Coordinator (for setting up the network), one or more Routers (for routing packets), and one or more End-devices. Illustration 1 shows a mesh network formed by C, R1, R2 and R3. There are two End-devices: E1 & E2.
Let’s say that initially, a wheelchair with the End-device E1 attached, is in a room with Router R2. E1 will be connected (wirelessly) to R2. If the wheelchair is moved to another room with Router R1, E1 will become connected to R1, due to the stronger signal from R1. When E1 detects a change in “parent” (i.e. the connected router), it will report to the Coordinator/Data Concentrator, via the ZigBee wireless mesh network. In this way, the Data Concentrator has a record of the last known location of every asset item. Illustration 2 shows what the hospital staff will see when the wheelchair is moved.
To deploy this tracking methodology, the Coordinator and Routers must be strategically positioned, so that each identifiable venue has one of them. Furthermore, the End-devices or “trackers” must be made small, reliable and low power (*). They must also be securely attached to the asset items. Needless to say, setting up should be fairly straightforward, and there should be minimum maintenance once the devices are deployed in the field.
(*) The 2000mAh battery can last up to 3 months, based on empirical measurement and calculation.
Illustration 3 shows, on the right, a ZigBee router, and on the left, a ZigBee tracker. Each costs around $49.4 to manufacture. So, to track 45 wheelchairs moving about in 15 identifiable venues, 60 such boards will be required, and the cost would be $2965.
