Students plug a gap

Education | Katie Hung 16 Apr 2019

For most of us, a dead battery on our phone is already an inconvenience. But imagine it happening to an electric wheelchair.

A real-life scenario of being stuck in the gap between the platform and MTR train, told by a non-government organization, the Direction Association for the Handicapped, to Alex Liu Chun-for, a MPhil student from the Department of Electronic Engineering at City University, his professor Henry Chung Shu-hung and year three undergraduate Tam Nga-wing got them thinking. The team, which is now collaborating with the association, researched and developed a battery diagnostic module to prevent wheelchairs from running out of power and stopping midway.

"Electric wheelchair users currently rely on their own experience to estimate how far one full-charged battery can support them," said Liu. "But when the lifespan of the battery drops, it fails to run for that distance even if it is fully charged.

"Many times, they have to wait until the battery is dead, or for the day it doesn't work any more to change for a new one. Our system can check the battery's lifespan, so they can switch to a new one in advance so that it won't happen in cases like being stuck in the gap between platform and train, or stopping in the middle of a road."

The module, which is installed externally right next to the original battery from the wheelchair below the seat, can prevent switching the battery too soon, and thereby preventing unnecessary electrical waste with a check on the battery condition.

Apart from its lifespan shown in percent, it can estimate the temperature of the battery, the remaining power - also shown in percent - and how many kilometers the vehicle can run on. These are all displayed on a small cube-shaped monitor attached to the wheelchair.

With funding from the university, the project has been in development for about 18 months.

It was showcased at the university's Employers' Luncheon 2019 last week with nearly 40 other projects to more than 350 employers.

The team estimates the cost of the module to be about HK$500, or even less if mass produced. It was tested by two wheelchair users for three months.

A new fully charged battery should be able to run for 30 kilometers, says data from the wheelchair manufacturer. But Liu found out through testing that it runs for only about half that after two or three years.

Both over-charging and depleting the battery would cut the its life span, Chung said. And the situation is similar to the human body: filling up the belly does not equal eating healthily.

"By the same token, though we see the battery is 100 percent charged, that means how much quantity of electricity it has. But whether it is healthy or not, we don't know," Chung said.

They were surprised to find the wheelchair battery was seriously out of shape in the study. "The battery actually has a cover, shaped like a box. How many people do you think will literally open the cover and take a look at it? So it is kept inside, letting it get charged in the morning, or at night, and use it whenever they have to travel. They wouldn't know the battery condition," he said.

The general test on the battery condition usually requires it to be taken apart and move to a laboratory to connect with another machine for monitoring.

However, the university work, which uses artificial intelligence to record and analyze the data, can produce results within two minutes while the wheelchair is still in use.

The module is still at the testing stage and is being discussed with the association. But they would like to improve communication between humans and machines for further enhancement of the module.

Liu said they are thinking of joining the module to a global positioning system so the family of users can identify their locations in case of accidents.

He is also looking to upload all the data recorded by the module to the cloud system.

The center of the non-government organization can remotely monitor the batteries' condition and remind users when it is time to switch to a new battery, or if any abnormal situation with the battery, such as staying hot for a long time, is identified.

This is also expected to lead to better maintenance as it is more convenient for the association to swap and gather all wheelchair batteries at once.

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