Clinically Speaking

Drive Controls & Programming a Power Chair

• By Jay Doherty
• Nov 01, 2012

One of the most time-consuming parts of an evaluation or fitting of a power wheelchair can be the custom programming required to meet the consumer’s individual needs. Programming can be one of the most intimidating parts of a fitting if you are not comfortable with programming the power wheelchair’s electronics.

There are many different parameters to program, from driving parameters to special features that allow a consumer independent access to the electronics. The trick to making this easier is to understand how the consumer wants and expects the power wheelchair to drive or handle. This can only be understood through programming the power base, then having the consumer control it, then perhaps programming it some more.

Driving Parameters

There are so many different parameters available to fine-tune how a power wheelchair drives and responds to the client’s input commands. The first thing you need to keep in mind is how and where the consumer has used a power wheelchair in the past and what sorts of electronics are needed to drive his or her power wheelchair. Answering these questions can allow you to have a better understanding of exactly what the consumer’s expectations of the wheelchair are going to be and how the wheelchair needs to be programmed to respond and drive in different environments.

When programming driving parameters, it is important to consider whether the input device is proportional or non-proportional. If it is a proportional controller, then the consumer can make fine adjustments to speeds and the way the power wheelchair handles by adjusting how far the joystick is deflected in a certain direction. This type of drive input device typically requires less up-front programming, since the consumer has the ability to adjust the responsiveness of the electronics through the amount of joystick deflection provided, as well as adjust the speed pot knob to make changes to the speed the wheelchair will travel.

A few of the parameters that are extremely important to consider are all the speeds, accelerations and decelerations for all directions of control. All of these parameters need to be adjusted specifically to how the consumer wants the wheelchair to react. They may even need to be different in each profile the consumer may use: for instance, an indoor profile with slower speeds and an outdoor profile with faster, more aggressive speeds. Keep in mind that there is a misconception from time to time that a wheelchair should drive perfectly right out of the box. It is our job as equipment providers and therapists to adjust a wheelchair to the consumer’s individual needs. We should always expect to make some changes to the programming for every power wheelchair fitting we take part in. If we don’t make changes to the programming, then the outcome for that wheelchair will be less than favorable.

A good example of why this programming is necessary for every fitting is an equipment provider or therapist who may work with two different individuals with cerebral palsy. One individual may be able to release the joystick quickly when stopping the power wheelchair, while the second may release the joystick more slowly. The individual who can release the joystick quickly to stop can have the wheelchair programmed so the wheelchair comes to a more gradual stop. The individual with a slower reaction time needs the deceleration turned up higher in order to stop within a safe distance. Every person is unique, and therefore every wheelchair will be programmed differently.

Proportional Control Considerations

As an equipment provider or therapist, our goal should always be to keep an individual driving with a proportional control for as long as possible, as proportional controls provide the consumer with greater control over the power wheelchair. The team should explore every proportional control programming feature a manufacturer offers before they change the input method to a non-proportional input device. To do this, the team must be very familiar with the proportional programming features offered.

A few of the features to be explored by the team may include allowing changes to increase the size of the neutral zone of a joystick, dampening or suppressing tremors to the joystick, reassigning each direction the deflection of a joystick represents, or decreasing the throw of a joystick required to reach maximum speed. Each of these features has a place and can benefit a multitude of individuals who drive power wheelchairs. We need to ensure that we are familiar with each of these parameters and how they change the way in which the joystick input device controls the power wheelchair.

Non-Proportional Control Considerations

When it comes to non-proportional input devices, the programming for these devices will need to be set up very differently from a proportional input device. A non-proportional device is on or off , and it does not offer much speed control. Therefore, this type of input device does not offer the fine adjustment that can be performed with a proportional input device. People who use non-proportional input devices typically have less control with their bodies and therefore fewer access sites on their bodies.

When setting up programming for a non-proportional device, we should consider offering a greater number of profiles for different driving situations. A typical profile layout for a non-proportional input device may appear as follows:

• Profile 1: Indoor driving and driving in tighter spaces
• Profile 2: Driving in hallways and larger spaces
• Profile 3: Driving outdoors, in very large open spaces
• Profile 4: Auxiliary functions (e.g., environmental controls, computer access, or access through the input device for a communication device)
• Profile 5: Power seat functions

Once the decision has been made about how many profiles the consumer would like, you can proceed with the setup of the driving parameters.

Programming of how the power wheelchair handles with a nonproportional input device can significantly influence how much a person uses and likes the power wheelchair. We need to look very closely at all the environments that the person drives within and do a good amount of fine-tuning with all driving parameters. Every driving parameter should be adjusted or at least looked at while considering how it will influence the wheelchair’s maneuverability in each environment.

Unlike a proportional input device, a non-proportional input device will require a significant amount of time spent programming each drive profile for the individual’s comfort level.

Beyond the drive parameters, there are many options to consider with each non-proportional input device. You may need to program multiple functions to be performed with one switch (e.g., on/off , mode changes, and emergency stop). It may be necessary to program a specific way for a head array to control the power seat functions, or the individual pressures needed for a sip-and-puff system. Setting up the programming for a non-proportional input device can take a great deal of time and investment by everyone on the team, so a big commitment will be necessary.

Keep in mind you may need multiple appointments in order to maximize the individual’s independence with the input method. Multiple appointments does not mean the team is not good at programming, but rather that the team is thorough and making sure the consumer is getting the maximum independence out of the power wheelchair.

We need to remember that, in the end, the time we put in at the beginning stages of a fitting provides a better outcome and a greater level of independence for the consumer. And isn’t that why we all joined this industry in the first place?

This article originally appeared in the November 2012 issue of Mobility Management.