Page 139 - Handbook of Electronic Assistive Technology

Chapter 5 • Alternative Access Technologies 127

Joysticks

Joysticks can be used to access a range of assistive technologies and are the most common
type of control interface for powered wheelchairs. Joysticks can offer a good option for
users who have impaired motor control due to, for example, cerebral palsy, because they
require less accurate fine motor control compared to mice or trackballs.
Joysticks are available in a wide range of shapes and sizes and can be operated using
different parts of the body (Fig. 5-16). They can be controlled using hand, finger, chin
or mouth. Some users find a ‘T-bar’ or round handle easier to grasp than the standard
‘stick’ handle. Joysticks to control the mouse pointer are available with USB or wireless
connections.
The joystick controls motion and speed of the mouse pointer: move the joystick left
and the pointer starts to move left; move the joystick back to the centre and the pointer
stops. Joysticks are generally slower to use when navigating the screen display than mice,
trackballs or trackpads.
Most joysticks are analogue or proportional – the further the joystick is moved, the
faster the pointer or the wheelchair moves.
‘Switched’ joysticks are also available, usually with four switches that move the wheel-
chair forward, back, left and right or the mouse pointer up, down, left and right. Switched
joysticks are usually terminated with a nine-way D-type socket wired to the industry stan-
dard TRACE protocol. They require a corresponding interface for connection to a wheel-
chair, communication aid, computer or other assistive technology device.
Analogue joysticks can provide more accurate control than switched joysticks, but only
if the user can control the position of the stick accurately: some people use gross move-
ments to operate a joystick and actually achieve better control with a switched joystick
where the speed and acceleration of the movement can be programmed and optimised.

FIGURE 5-16 SimplyWorks wireless joystick with alternative handles, PointIt! Mini USB joystick and mini joystick
with push switched joystick�