introduction

The Skipper is a very sensitive wheelchair controller that is based on a force sensor. Other controllers are based on a joystick that needs a force and some movement to operate. The Skipper can be operated by force alone without any perceptible movement. For some wheelchair users this can be a game-changing property.

The control stick of the Skipper is removable. It can be rigid or flexible. With the rigid version the Skipper operates like a true force stick. With the flexible version it operates like a normal joystick. The amount of movement for a particular operating force depends on the stiffness of the spring in the flexible stick. Shannon can provide sticks with different spring stiffnesses.

The force necessary to obtain full output is adjustable from 10 grams to 700 grams. The adjustment can be made by the wheelchair dealer with a wireless programmer while the user is free to drive around. In this way the optimal setting for a particular user can be found quickly and easily.

Another unique feature of the Skipper is an adjustable non-linear relationship between input force and wheelchair speed. Usually this relationship is linear: a 10% increase of the input gives a 10% increase of the speed. However, the users’ perception of a 10% speed increase depends on the current wheelchair speed. A speed increase from 0% to 10% is highly noticeable but an increase from 90% to 100% hardly is.

The Force/Speed relationship of the Skipper is adjustable in such a way that, for the same force increase, the speed increase gets larger as the speed gets higher. The user may experience this as more precise control at low speed and a more responsive stick at high speed. The optimal individual adjustment can be made by the dealer in the same way as the operating force.

Finally, the Skipper has an adjustable low-pass filter that may be useful for people who have to deal with a tremor. This filter does not affect slow input changes but suppresses fast changes. The optimal adjustment can be made by the dealer. All adjustments made by the dealer are stored in the Skipper and remain unchanged until readjustment.

removable sticks

The removable sticks can be screwed on the skipper body, which has a fixed m4 stub. A rigid stick comprises two halves that are firmly held together with strong magnets. If the applied force gets strong enough to potentially damage the sensor (or the user), the magnets give way and the stick breaks. A broken stick will automatically repair itself because of the magnetic attraction. Some users temporarily remove the upper half or the whole stick because it gives them a flat surface to work on.

The two halves of a flexible stick are connected by a spring. It is operated by both force and movement, similar to a regular joystick. The standard option is a flexible stick that moves 5 mm with a force of 150 grams. In special cases, Shannon can provide sticks with different spring stiffness.