Emerson unidrive m200 - S Ramp Enable; Max Rate of Change of Acceleration

Parameter 02.006 S Ramp Enable
Short description Set to 1 to enable the use of S ramps
Mode Open‑loop
Minimum 0 Maximum 1
Default 0 Units
Type 1 Bit User Save Update Rate 16ms
Display Format Standard Decimal Places 0
Coding RW
If SRampEnable (02.006) = 0 linear ramps are used, but if SRampEnable (02.006) = 1 a limit is applied to the rate of change of acceleration to give S
ramps. The S ramp function is disabled during deceleration when the standard ramp voltage controller is active. When the motor is accelerated again
the acceleration rate used by the S ramp function is reset to zero and has to rise to the programmed acceleration level at the programmed rate of
change (see MaxRateOfChangeOfAcceleration (02.007) and SRampSet-upMode (02.041) ).
Parameter 02.007 Max Rate Of Change Of Acceleration
Short description Defines the maximum rate of change of acceleration used by the ramp system
Mode Open‑loop
Minimum 0.0 Maximum 300.0
Default 3.1 Units s²/100Hz
Type 32 Bit User Save Update Rate Background read
Display Format Standard Decimal Places 1
Coding RW
A rate of change of acceleration can be applied such that the acceleration rate changes linearly between 0 and the value
in MaxRateOfChangeOfAcceleration (02.007) during acceleration, and between MaxRateOfChangeOfAcceleration (02.007) and 0 during
deceleration. If SRampSet-upMode (02.041) = 0 then the maximum rate of change of acceleration in both directions, accelerating away from or
towards zero, is defined by MaxRateOfChangeOfAcceleration (02.007).
The general equations are given below for a linear ramp and S ramp where
Δw is the required change of frequency or speed
a
Max
is the maximum allowed acceleration in units of frequency/s or speed/s
J
Max
is the maximum rate of change of acceleration (i.e. jerk) in units of frequency/s
2
or speed/s
2
The time for a linear ramp to give a change of frequency or speed Δw is
T
Linear
= Δw / a
Max
If an S ramp is used w
B
is the change of frequency or speed as the acceleration changes from zero to aMax, i.e. the S shaped part of the frequency or
speed change.
w
B
= a
Max
2
/ 2J
Max
If the required frequency or speed change is less than 2wB, i.e. Δw < 2wB, then the acceleration never reaches its limit and the ramp does not contain a
linear ramp section and the time for the ramp is given by
T
SRamp1
= 2 √(Δw / J
Max
)
Otherwise
T
SRamp2
= (Δw / a
Max
) + (a
Max
/ J
Max
)
The following is an example based on the default parameter values for Open-loop mode. The diagram below shows a change of frequency from 0Hz to
50Hz with the ramp rate set to 5.0s/100Hz and MaxRateOfChangeOfAcceleration (02.007) set to its default value of 3.1s
2
/100Hz.
Unidrive M200 Parameter Reference Guide
Issue: 01.05.00.10
33