It's been over 25 years since the introduction of the VCR - and even today they remain difficult
for many to program. As if VCRs aren't difficult enough, imagine if the set-up screens had seemingly
overlapping terms like "Clock" and "Time," or "Volume" and "Sound Level," leading to even more ambiguity
and confusion. Beyond hypothetical technology talk, powerchair electronics of recent years have lead
many users down such a seemingly ambiguous path, where programming parameters leave consumers and providers
alike befuddled by the differences and functions of "Acceleration," "Power," and "Torque" settings.
After all, aren't power, torque, and acceleration all but synonymous?|
The answer is, no. While
they all relate to how much gusto a powerchair has under given conditions - wheelie-popping acceleration,
furniture-pushing power, and curb-climbing torque - they function in very different ways, with different
effects. And, the key to programming the power into a powerchair is achieved by understanding how the
dynamic parameters of Acceleration, Power, and Torque affect performance.
Acceleration parameter dictates how quickly a powerchair travels toward its maximum speed. In the obvious,
the higher the Acceleration value, the faster the powerchair takes off from a stop. However, higher
Acceleration values also aide in overcoming obstacles, as a sudden burst of acceleration can bring a
powerchair to higher amperage quickly, effectively apply a boost of power. On the downside, a high Acceleration
rate can make a powerchair feel twitchy to its user, as the powerchair wants to go from a stand still
to full throttle in an instant - tap the joystick, and the powerchair may leap into action.
The Power parameter limits a powerchair's power output to the motors, specifically to minimize damage
potential from a powerchair that's accidentally driven into a fixed object (as with walls or furniture).
The way the Power parameter works is by limiting the current output of the controller. For example,
if a controller's current limit is 80A, and the Power parameter is set at 25% in a particular Mode, the
powerchair's current limit in that Mode will be 20A (a low power setting that may protect against an
accident like pressing footplates against a door jam and creating damage). Fully proficient users do
not typically lower the Power parameter below 100%, as it reduces performance when full power is needed,
such as outdoors.
The Torque parameter increases current to the motors in stall
conditions, as with climbing an obstacle. As a powerchair approaches an obstacle at slow speeds, it
may not have enough torque to climb it, so in the event that the motors stall against the obstacle, the
controller boosts power to the motors incrementally, until the powerchair climbs the obstacle or the
powerchair's maximum current is achieved (an ultimate stall condition where the obstacle is too large
for the powerchair to surmount). Whereas a high Acceleration setting calls for an all-out response,
Torque steps up current incrementally, increasing climbing control at low speeds, without encouraging
the powerchair to notably increase speed.
(Note: Power and Torque are used as terms and descriptions
to serve a similar result - controlling how much "force" a powerchair puts out - and most electronics
only feaure one of the terms and descriptions.)
Power, and Torque overlap in everyday use and definitions, all relating to the felt "power" of a powerchair.
Yet, the parameters are distinct toward how quickly a powerchair takes off, how much its ultimate power
is restricted, or how much current the controller steps up to the motors under stall conditions. In
this way, within the maximum limits of each powerchair, consumers can tailor performance to their demands.
Published 1/06, Copyright 2006, WheelchairJunkie.com