Smoothing Output Torque - Sevcon Gen4 Applications Reference Manual

Torques in driveability profiles are in 0.1%/bit resolution. These are converted to Nm using the
motor rated torque value at object 6076
Ramp rates in driveability profiles are in either RPM/s for speed mode, or %/s for torque mode.
In speed mode, RPM/s becomes "User Defined Units" / s if the gear ratio is used to rescale the
driveability profile speeds.
Speed limit ramp rates are only used in torque mode and are in RPM/s (or user defined units /
s).
WARNING: In addition to the speed limit ramp rates in the profiles, 291E
configure safety limits on speed limit ramping. The installer should set these ramp rates
to suitable levels to ensure speed limits cannot ramp faster than could actually happen
on a vehicle. This can protect against harsh braking if traction wheels are momentarily
locked.

Smoothing Output Torque

Demand
from throttle
Figure 31 - Illustration of s-curve on torque demand
The controller provides an option to insert an s-curve to the torque demand as it approaches the
value requested by the throttle. This curve feature can serve two purposes:
The amount of curve applied can be configured in the object dictionary at index 2933
Generally, applying a greater curve range will result in smoother drive, but too much can lower
vehicle response. S-curve is applied according to this table:
Value in 2933 S-curve behavior
h
0 None applied
1 Curve applied within 0.2% of target
6-28
.
h
Applied torque demand,
limited by ramp rate from
driveability profile
can be used to
h
Curve applied to torque
demand in this range.
Size of this range defined
by s-curve parameter.
.
h