Head array power wheelchair drive controls are common chosen methods of controlling a power wheelchair when a joystick is not an option. This is due to several different reasons. First, the head and neck are areas of the body where consistent movement often remains intact after traumatic injuries or onset of progressive conditions. For example, due to the nerve innervations of cervical spine musculature being from cranial nerves or higher cervical spinal roots, even an individual suffering a higher cervical spinal cord injury has residual movement of the neck. Second, the use of a head array tends to be a simple device that is easy to learn for many individuals, regardless of their age or condition. Third, the head array system has variable configurations and is highly adaptable, allowing the system to be configured based on the individual’s needs.
A head array system typically consists of a head support system (foam pads and adjustable hardware) and proximity switches imbedded in the head support pads. A proximity switch is a capacitive switch that does not require any force to activate the switch. The proximity switch activates when an object that conducts electricity comes in close proximity to the switch. The switch then remains activated if the person remains in close enough proximity to the switch.
There are several ways to configure a head array system, but the most common is a three-switch setup. This setup consists of three proximity switches with one mounted into each of the three individual headrest pads. Some manufacturers of head array systems allow the changing or re-assigning of the actions performed when a particular switch activates. Typical setup consists of activating the rear pad switch to drive forward, the left pad switch to drive left, and activating the right pad to drive right.
There are multiple options (depending on the manufacturer) for driving in reverse. One way to accomplish driving in reverse is to add an additional switch to the system, which when activated the system toggles from forward to reverse. After toggle completed, an activation of the rear pad moves the chair in the reverse direction. Another option for toggling the system into reverse is for the individual to perform a quick activation of the rear switch. This method allows for driving in all four directions while only requiring three total switches to operate the system.
As mentioned, the three-switch head array system is the most common setup, however there are other options to consider. Some manufacturers offer four and five switch options in addition to the standard three. In these options, an additional switch can be added to the lateral pads of the head array system. This does require the end user to have a certain level of motor control and accuracy with movements to access the multiple switches in the lateral pads separately. Another alternative is to utilize other access locations (body parts) and/or switch types (pneumatic/mechanical/fiber optic) in combination with the head array system. One common example of this is a head array/sip-n-puff combination system. Using the head array/sip-n-puff combo typically involves the use of a pneumatic switch (activated by sipping or puffing through a specially mounted straw) for activating forward and reverse directions then utilizing the lateral pads of the head array proximity switches for turning. This setup can be a good option if the end user is able to activate the lateral pads of the head array for turning but has limited control of their head/neck when attempting to drive forward and stop the chair by ringing their head off the back pad.
Stealth Products® offer this option through their iDrive Alternative Control System. iDrive is a specialized processing unit that manages the input from various devices and sends outputs to the power chair. This processing unit allows the use of different switch types all within one system, thus the capability of using combination systems. Combination systems are not limited to just the head array/sip-n-puff combination. The iDrive system allows the use of any switch type in combination with one another to meet the end user’s motor control and functional movement needs. The iDrive system allows the use of proportional joysticks in combination with switches. For example, if the end user can manage a specialized joystick (specific to the iDrive system) in directions (forward/reverse or left/right) the other two directions can be accomplished with switches in the head array pads.
In addition to the mechanical and physical setup of the head array, the electronic or programming capabilities are an important consideration to review. Earlier, the use of a separate toggle switch was discussed as a way to flip or toggle the three-switch system between the forward and reverse directions. If a separate switch access point is not available for this, however, the proximity switch in the rear pad can be used as well with a quick tap while the wheelchair is not moving. The system can distinguish between a quick tap and an actual intended drive command by the how long the switch is held and activated. This timing can be adjusted within the programming to match the person’s motor control and movement capabilities. The timing required for this toggle or quick tap can be adjusted manually choosing the desired time or by having the system learn the end user’s timing of the command.
Another key programming feature is the use of double commands on the input device. Double commands can be used as an alternative to mounting a separate switch on the system to change modes of the power wheelchair. This is an extremely important feature as many head array end users do not have access to a separately mounted switch. This double command is set up on either the left or right head pad switch and the timing can be adjusted or programmed (just like the toggle command) to match the end user’s timing and abilities. This double command feature is available within Q-Logic 3 for reducing the number of switches required for the client to be as independent and safe as possible.
As you can see, Quantum’s Q-Logic 3 Drive Control System and the iDrive Alternative Drive Control System exhibit a vast amount of modification and configurability to maximize the end user’s function and abilities. While these systems offer tremendous options for our end users, the combination of the two systems make a formidable and highly adaptable pair!!