AMIS-30623 LIN Microstepping Motordriver
Data Sheet
15.4 Motion Detection
Motion detection is based on the back emf generated internally in the running motor. When the motor is blocked , e.g. when it hits the
end-position, the velocity and as a result also the generated back emf, is disturbed. The AMIS-30623 senses the back emf, calculates a
moving average and compares the value with two independent threshold levels: Absolute threshold (AbsThr[3:0] ) and Delta threshold
(DelThr[3:0]). Instructions for correct use of these two levels in combination with three additional parameters (MinSamples, FS2StallEn
and DC100SDis) are outside the scope of this datasheet. Detailed information is available in a dedicated white paper “Robust Motion
Control with AMIS-3062x Stepper Motor Drivers”, available on http://www.amis.com/.
If the motor is accelerated by a pulling or propelling force and the resulting back emf increases above the Delta threshold (+ ∆THR),
then <DelStallHi> is set. When the motor is slowing down and the resulting back emf decreases below the Delta threshold
(- ∆THR), then <DelStallLo>is set. When the motor is blocked and the velocity is zero after the acceleration phase, the back emf is
low or zero. When this value is below the Absolute threshold, <AbsStall> is set. The <Stall> flag is the OR function of
<DelStallLo> OR <DelStallHi> OR <AbsStall>.
Velocity
Vbemf
+ ∆THR
Vmax
Motor speed
- ∆THR
Vbemf
Vbemf
Vmin
Vbemf
t
t
DeltaStallHi
DeltaStallLo
VABSTH
Back emf
t
t
t
AbsStall
t
Figure 24:Triggering of the Stall Flags in Function of Measured Back emf and the set Threshold Levels
Table 25: Truth Table
Condition
<DelStallLo>
<DelStallHi>
<AbsStall>
<Stall>
Vbemf < Average - DelThr
Vbemf > Average + DelThr
Vbemf < AbsThr
1
0
0
0
1
0
0
0
1
1
1
1
The motion will only be detected when the motor is running at the maximum velocity, not during acceleration or deceleration.
If the motor is positioning when Stall is detected, an (internal) hardstop of the motor is generated and the <StepLoss> and <Stall> flags
are set. These flags can only be reset by sending a GetFullStatuscommand.
If Stall appears during DualPosition then the first phase is cancelled (via internal Hardstop) and after timeout (26.6 ms) the second
phase at vmin starts.
When the <Stall>flag is set the position controller will generate an internal HardStop. As a consequence also the Steploss flag will be
set. The position in the internal counter will be copied to the ActPos register. All flags can be read out with the GetStatus or
GetFullStatus command.
Important remark:
Using GetFullStatus will read AND clear the following flags: <Steploss>, <Stall>, <AbsStall>, <DelStallLo>, and
<DelStallHi>. New positioning is possible and the ActPos register will be further updated.
Using GetStatus will read AND clear ONLY the <Steploss> flag. The <Stall>, <AbsStall>, <DelStallLo>, and
<DelStallHi>flags Are NOT cleared. New positioning is possible and the ActPos register will be further updated.
AMI Semiconductor – June 2006, Rev 3.0
39
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