The Cycle Analyst behaves similarly. When it senses that any one of
the limiting quantities has been exceeded, then the throttle over-ride
signal starts to decrease from its default resting value (usually
between 4 to 5V, determined by ITermMax). A simple circuit is required
so that the controller only sees the lower value of the throttle signal or
the Cycle Analyst signal. This is generally achieved with a diode as
follows:
There are various setup options which control the speed at which the
Cycle Analyst responds to these signals. If the settings are too fast,
then the control can be twitchy or oscillate around the desired value,
while gain settings that are too low will cause a long lag time before the
limiting kicks in.
7.2
PI Controller
Each of the three limiting features is implemented as a digital
Proportional/Integral (PI) controller. The actual output for speed
regulation is computed as follows:
ITerm = Previous ITerm + IntSGain*(Set Speed - Actual Speed)
Clamp: ITermMin < ITerm < ITermMax
Override = ITerm + PSGain*(Set Speed - Actual Speed)
Similar values are calculated with the current limit, and low voltage
limit, and the smallest of the three over-ride terms is output as a
voltage. If this output is less than the user’s throttle voltage, then it is
the Cycle Analyst which is ultimately controlling the vehicle.
7.3
Tuning the feedback
The ability of the Cycle Analyst to limit the speed, current, or low
voltage in a fast yet smooth manner depends on setting the
appropriate Gain terms for the feedback loop. The default values work
well for ebike setups in the 300-600 watt power range. For more
powerful systems, they will usually lead to the vehicle oscillating
around the programmed set point rather than holding steady. In this
case, it is necessary to tone down the appropriate feedback gains in
the advanced setup menu.
5V
G
Throt Signal
Throttle
2 - 10 k
Resistor
Diode
Throttle Over-ride
to Cycle Analyst
Throttle Signal
inside Controller
13
