In continuing our series on de-mystifying power wheelchairs, this month let’s look more closely at electronics. Electronics for power wheelchairs can be categorized into expandable and non-expandable options. What this refers to is the degree to which the electronics allow different input devices, power options, drive profiles and functionality with assistive technology.
Electronics and Input Devices
Non-expandable electronics are basic electronics that allow for the operation of the power wheelchair through the use of a joystick only. Expandable electronics allow for the operation of the power wheelchair through the use of a joystick or specialty controls, such as a sip and puff control, a head array, or a switch. Expandable electronics are required if specialty controls will be used. Expandable electronics also permit the use of more than one input device to be used, if needed.
Electronics and Power Options
Non-expandable electronics have limited ability to add power seating features, such as tilt and recline seating. Power seating requires the addition of an actuator, which is a separate motor that operates the power seating through the driver input (e.g. one actuator will move the seating into a tilt position and return it to a neutral position). Only one seating actuator can be operated through the controller of non-expandable electronics. This means that only one power seating option, such as tilt, can be operated through non-expandable electronics.
Note that non-expandable electronics can allow for up to two actuators to be accessed through the input device; however, it is limited in that only centre-mounted elevating leg rests can be selected with one power seating option.
Expandable electronics can allow for multiple actuators to be controlled through the driver input. Power tilt, recline and elevating leg rests each require their own actuator to function. Therefore if more than one of these power seating options is required, or if individually elevating leg rests are required in addition to one power seating option, expandable electronics must be chosen.
Electronics and Drive Profiles
A drive profile is a set of parameters that can be modified through programming. These parameters include setting the minimum and maximum speeds, accelerations and decelerations available in forwards, in turns, and in reverse and setting the maximum amount of torque and power available for use. Drive profiles allow for different sets of parameters to be saved for different client needs, such as driving in different environments or to account for fatigue at the end of the day.
Non-expandable electronics will have fewer drive profiles available than expandable electronics will have. (The actual number of drive profiles available varies by manufacturer.) Expandable electronics will have a greater number of parameters available for programming, such as Deadband and Lock Function Enable.
Recall from the Power Programming Basics article here that Deadband refers to the neutral zone around the centre of the gimble through which the joystick must pass before the motors are engaged. The size of the Deadband can be programmed to suit the needs of the individual. Lock Function Enable is a programming parameter that allows the wheelchair to be locked from driving and is activated by a series of joystick movements.
Electronics and Functionality with Assistive Technology
Only expandable electronics can be interfaced with assistive technology, such as an environmental control unit, or ECU. Similarly, only expandable electronics are Bluetooth and Infra-Red (IR) compatible. Expandable electronics allow for the integration of IR devices, such as a television, DVD player, or door opener, and the integration of Bluetooth devices, such as a computer mouse, which lets the user operate these devices through the input device on the power wheelchair. Non-expandable electronics do not have the capacity to integrate such assistive technology and environmental access.
When trying to determine whether a client requires expandable or non-expandable electronics, it is important to consider both current and future needs. Consider the stability of the client’s condition and whether or not deterioration of the client’s function is anticipated. Consider the ability of the client to operate a joystick, both now and in the future. Consider the need for seating functions. How many power seating and positioning functions are required at this time? What will the need be in the near future? Is there a need for integration of the electronics with environmental access?
In summary, non-expandable electronics are appropriate for clients who will operate a power wheelchair with a joystick, who require only one power seating option, and whose functional status is expected to remain stable throughout the life of the power wheelchair. Expandable electronics are required for clients who will use a specialty control device for access, must have environmental access through the input device, and/or require multiple actuators for seating/positioning. Expandable electronics should be considered for a client whose condition is anticipated to deteriorate and who may require these features in the foreseeable future.