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How EMI/EMC testing makes electric wheelchairs safe

2021/06/15 > Back

Electric wheelchair operating environments:
Electronic wheelchairs need to be capable of working in a variety of different environments, both indoors and outdoors. This means each chair needs to pass a series of tests that simulate all these locations. In indoor environments, an electronic wheelchair must withstand any home-level electronic disturbances; also needs to be able to handle conducted RF, such as those generated by amateur and professional radio stations.

There are some concerns about electromagnetic interference to powered wheelchairs and scooters. You need to know what EMI (Electromagnetic Interference) is and how to prevent such incidents. The following paragraphs suggested by the Food and Drug Administration (FDA) are intended to provide you some important information about this:

1. Electromagnetic interference (EMI) from radio wave sources:
Powered wheelchairs and motorized scooters may be susceptible to electromagnetic interference (EMI), which is interfering electromagnetic energy (EM) emitted from sources such as radio stations, TV stations, amateur radio (HAM) transmitters, two-way radios, and cellular phones. The interference (radio wave sources) can cause the powered wheelchair to release its brakes, move by itself, or move in unintended directions, it can also permanently damage the powered wheelchair’s control system.

2. There are ample sources of relatively intense electromagnetic fields in everyday environment. The sources of radiated EMI can be broadly classified into three types:

2-1. Hand-held portable transceivers:
Examples include: citizens band (CB) radios, walkie talkie, security, fire, and police transceivers, cellular telephones, and other personal communication devices. Note: Some cellular telephones and similar devices transmit signals while they are on, even when not being used.

2-2. Medium range mobile transceivers:
Examples include: those used in police cars, fire trucks, ambulances, and taxis. These usually have the antenna mounted on the outside of the vehicle.

2-3. Long-range transmitters and transceivers:
Examples include: commercial broadcast transmitters (radio and TV broadcast antenna towers) and amateur (HAM) radios. Note: Other types of hand-held devices, such as cordless phones, laptop computers, AM/FM radios, TV sets, CD players and small appliances (such as hair dryers) are not likely to cause EMI problems to your powered wheelchair.

Therefore, we recommend that you use the precautions listed below to prevent possible interference with the control system of an electric wheelchair / powered scooter:

1. Do not operate hand-held transceivers (transmitters-receivers), such as citizens band radios or turn ON personal communication devices such as cellphones, while the powered scooter is turned ON.

2. Be aware of nearby transmitters, such as radio or TV stations, and try to avoid coming close to them; If unintended movement or brake release occurs, turn the powered scooter OFF as soon as it is safe.

3. Be aware that adding accessories or components, or modifying the powered scooter, may make it more susceptible to EMI (Note: There is no easy way to evaluate their effect on the overall immunity of the powered scooter.)

4. Report all incidents of unintended movement or brake release to the powered scooter manufacturer, and note whether there is a source of EMI nearby.

5. Check to see if your electric scooter complies with the relevant EMC standards. To make it to the market, an electronic wheelchair has to pass EMC testing and a variety of other requirements according to the RESNA standards for electric wheelchairs, as well as scooters and accessories:

Dynamic stability
Brake effectiveness
Energy consumption
Maximum speed, acceleration and deceleration
Climatic tests
Obstacle climbing
Power and control system tests

If a new wheelchair model can pass all these tests, as well as the EMC testing, it can be made available for purchase.

We are a professional manufacturer of EMI/RFI filters and can provide EMC solutions related to electric wheelchairs. Find out more.

Data source: moose mobility scooter, www.nts.com