5.3.7.19
Steering stability parameters
Parameter
Possible Values Default
Rev HHP Lite Std Adv
Turning @ Full Speed
5 – 100 %
100 %
C
-
Turning Accel @ Full Speed
100 – 300 %
100 %
C
-
If the powerchair travels at full speed, the chair can easily "snake". When the
powerchair snakes, it slightly changes direction from left to right.
The powerchair "snakes" at full speed
Two different events can cause snaking:
1.
When the chair travels straight forward at full speed, small unintentional joystick
movements (for example when the chair drives over a bump and the hand of the
user shifts) can cause the chair to veer off. The user then over-corrects the
direction which results in snaking of the powerchair. At full speed, a reduction of
joystick sensitivity can help the user to keep the chair straight.
Turning @ Full Speed
changes the value of the
Turning Speed @ Maximum
parameter (see 5.3.7.9) when the joystick is pushed full forward.
•
A value of 100% has no effect
•
A value of 50% reduces steering at full speed by 50%.
2.
If the user
does
want to change direction slightly when travelling at full speed, the
acceleration damping of the
Damping Point
(see 5.3.7.16) in combination with
the Chair Stability Parameters (5.3.7.18) can cause a steering delay. The user does
not feel the chair turning and deflects the joystick further, effectively
over-steering. When the chair catches up it turns too far and the user has to
correct again. This also results in snaking of the powerchair. A faster turning
response helps to prevent this kind of behaviour.
Turning Accel @ Full Speed
changes the value of the
Turning Acceleration
parameter (see 5.3.7.11) when the joystick is pushed full forward. A value above
100% achieves a more responsive turn characteristic at high speed. This
compensates the Damping Point effect for small sideways joystick deflections.
•
A value of 100% has no effect
•
A value of 200% doubles the turning acceleration at full speed.
Note:
A low value of the
Turn Damping
parameter (see 5.3.7.16) can also
prevent steering delays .
GBK60348
: Issue 1 – October 2007
78
