Difference between revisions of "Using stepping motor with IONI"

Revision as of 12:11, 7 May 2015

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).

Use Granity's Measure resistance & inductance button to automatically set MR and ML

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