Power wheelchairs can be a great way for people with limited mobility to get around. The standard way to control a power wheelchair is via a joystick typically mounted on either side of the wheelchair.
However, if you have a limited range of motion or strength, then using the standard joystick may be difficult. There are a growing number of alternative options that are becoming available. These include light touch mini joysticks, switches, touchpads and sip and puff controls.
Mini Joystick are usually much smaller than the standard wheelchair joystick. They required less force to deflect or operate the joystick, which may be a low as 18g of pressure. Like a standard wheelchair joystick most of them are proportional, so the more they are deflected the faster the chair will move. However some joysticks are controlled by the pressure applied and do not deflect. To keep the joystick compact, buttons for the power, lights and actuators are not part of the joystick housing, as these controls are operated by alternative methods. Mini joysticks may activate a mode change on pushing directly down on the joystick from neutral position.
Touchpads feel similar to what you may find on a computer for controlling its mouse cursor. They are based on touch and no pressure is required. Touchpads can be configured for the user so that touching a specific part of the touchpad relative to the center will move in that direction. Alternatively it can be operated by dragging a finger along the touchpad in the desired direction. An earlier blogpost explains this in some more detail, http://www.atandme.com/?p=674
Switches by their nature do not have proportional control. So activating a switch will move in a particular direction and releasing the switch will stop. However as a power wheelchair’s acceleration and deceleration characteristics can be setup to be gradual, driving can still be smooth. Switches can be mechanical momentary switches or based on proximity where no physical contact is required. Multiple switches can be used, one for each direction, three switches as in a head array or a single switch that is used with some scanning display.
Sip and Puff Controls
These are operated by sucking and blowing on a mouthpiece. Sip and puff pressures are programmable and will also have a mode change feature in order to operate other chair controls such as lights or actuators. They require quite a bit of practice by the user to get good at driving. Not only does the wheelchair electronics distinguish between a sip and a puff, it can also recognize the strength of the sip and puff. Basic Sip and Puff pressure is interpretation as… HARD PUFF – Forward, SOFT PUFF – Right, SOFT SIP – Left and HARD SIP – Reverse.
In some cases, it may be necessary to also connect an emergency stop switch. The stop switch needs to be mounted in a position for easy activation by the user.
Further details can be found from the following supplier websites.
mo-Vis power wheelchair accessories
Dynamic Controls secondary controls