Using stepping motor with IONI

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Revision as of 11:39, 3 June 2015 by Tero K (Talk | contribs) (Setting up open loop mode)


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Using stepping motor with IONI drive is possible in three ways:

Open loop (no encoder)
This is the traditional stepping motor drive method. Will achieve highest speed and is easily configurable but there is no feedback, so if motor stalls/loses synchronism, the absolute position will be unknown before referencing/homing.
Closed loop (with encoder feedback)
This is open loop mode combined with encoder feedback. The advantages are that drive can detect loss of synchronism and restore to commanded position with clear faults command. May be used also with linear encoder to enhance system accuracy.
Servo (with encoder feedback)
In this mode, a stepping motor is used as high pole count brushless servo motor. In this mode, motor efficiency is high (no current if no load) and motor do not lose synchronism. However, motor speed is limited by back EMF of motor and typically can achieve lower top speed than the other modes.

Setting up open loop mode

In this mode, drive emulates encoder internally and some tuning parameters need to be set to allow operation:

MT Motor type
Stepping motor
FBD Feedback device
None
FBI Invert feedback direction
Unticked
FBR Feedback device resolution
6400 (this is the emulated encoder resolution, 6400 PPR = 25600 steps/rev)
MCC Motor continuous current
This is the resting current when motor stands still. Drive will switch to this after 0.5 seconds of standing still.
MMC Motor peak current limit
This is the motor rated current that is used when motor is rotating.
MR Motor coil resistance
See motor datasheet or if not known, start with low values such as 1 ohm
ML Motor coil inductance
See motor datasheet or if not known, start with low values such as 1 mH
CM Control mode
Set to Position control (typical) or Velocity control mode
KVP Velocity P gain
0
KVI Velocity I gain
180
AFF and VFF
0
KPP Position P gain
30
PFF Position feed-forward gain
100%
FEV Over speed fault
1000
FPT and FVT fault limits
1000

Other settings are not critical and can be configured as desired (such as acceleration and velocity limits).

Seting up closed loop mode (with encoder feedback)

In this mode, follow parameterization of closed loop mode except:

FBD Feedback device
Choose your feedback device (other than None)
FBI Invert feedback direction
Try both settings and choose the one with stability
FBR Feedback device resolution
Set your feedback device resolution
KVI and KPP
Tune KVI and KPP values (and possibly other gains if non-zero) to have nice response
FMO Motion fault limit
Set non-zero value (perhaps 100-1000) to cause a fault state when motor stalls

Setting up servo mode

To set-up stepper as servo motor, just follow the IONI & IONICUBE user guide and consider the stepper motor as servo motor. For a typical 1.8 degree/step two-phase stepping motor the correct motor type parameters are:

MT Motor type
2 Phase AC or BLDC
MPC Pole count
100

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