Ⅲ. EMI/RFI
EMI/RFI Warnings
Laboratory studies by the Food and Drug Administration (FDA) have shown that radio waves can cause the unintended
movement of electric vehicles. Radio waves are a form of electromagnetic energy (EM). When electromagnetic energy
adversely affects the operation of an electrical device, this adverse effect is called electromagnetic interference (EMI) or
radio frequency interference (RFI).
EMI/RFI Frequently Asked Questions (FAQs)
The following FAQs summarize what you need to know about EMI/RFI. Use this information to minimize the risk that
electromagnetic interference / radio interference will adversely affect the mobile vehicle.
Where are radio waves coming from?
Radio waves are emitted from cellphones antennas, mobile radiotelephones (such as walkie-talkies and CB radios), radio stations,
television stations, amateur radio (HAM) transmitters, wireless computer links, microwave sources, and paging transmitters. Radio
waves are a form of electromagnetic energy (EM). The EM is more intense closer to the transmit antennas that are the source of the
emission. The greater the transmission power, the greater the concern for electric mobility vehicle users.
If EMI/RFI is affecting my wheelchair, what kind of movements can I expect?
It is hard to predict. The answer depends on many factors:
Radio wave strength.
Design of a specific mobile vehicle.
The position of the electric wheelchair (whether it is on flat ground or on a slope).
The electric wheelchair is in motion.
Any electric wheelchair, affected by EMI/RFI, may have erratic movement. The wheelchair may stop suddenly or move in an
uncontrolled manner. It is also possible that the EMI/RFI will release the wheelchair brakes. Some intense electromagnetic/radio
interference can even damage components of the wheelchair's control system.
Is there any way to determine if radio waves are causing the vehicle to move unintentionally?
Unfortunately, EMI/RFI can be difficult to recognize because signals from radio sources are invisible and may be intermittent.
However, the FDA recommends reporting to the manufacturer all instances of unintentional movement or unintentional release of
the wheelchair brake and, if possible, determining whether there was a source of radio waves in the vicinity of the incident.
One of the precautions that can be taken against unintentional movement of the wheelchair is to make sure that you or another
person are not causing the movement.
When getting on or off the electric wheelchair, switch off the electric wheelchair by removing the ignition key.
Never leave the ignition key in an unattended wheelchair.
By following these steps, you greatly reduce the risk of you or anyone else accidentally hitting the throttle control levers,
causing unintended movement of the truck.
Has anyone been injured by the irregular, unintentional movement of the electric
wheelchair?
The FDA reports injuries caused by the uncontrolled movement of electric trucks. However, it is not clear how many of these
injuries were actually caused by EMI/RFI.
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