Using stepping motor with IONI

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

Mode1 - 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.

Mode 2 - 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.

Mode 3 - 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. In this mode stepper can be also safely driven over it's rated current to get higher peak torque than it's rated torque (like a servo motor).

In the modes 1 and 2 stepper is driven with constant current drive and the motion produced by adjusting phase angle (traditional stepper drive method). In the mode 1 phase angle is controlled directly by setpoint trajectory and in mode 2 it is controlled by encoder based feedback loop. In the mode 3 motor current is controlled by torque controller (from zero to peak current limit) while phase angle is synchronized to rotor angle by the help of encoder. Mode 3 is similar to servo motor control (more details).

Setting up open loop mode 1

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

Motor typeMT Motor type

Stepping motor

Feedback deviceFBD Feedback device

None

Invert feedback directionFBI Invert feedback direction

Unticked

Feedback device resolutionFBR Feedback device resolution

6400 (this is the emulated encoder resolution, 6400 PPR = 25600 steps/rev)

Continuous current limitMCC Motor continuous current

This is the resting current when motor stands still. Drive will switch to this after 0.5 seconds of standing still.

Peak current limitMMC Motor peak current limit

This is the motor rated current that is used when motor is rotating.

Coil resistanceMR Motor coil resistance

See motor datasheet or if not known, start with low values such as 1 ohm

Coil inductanceML Motor coil inductance

See motor datasheet or if not known, start with low values such as 1 mH

Control modeCM Control mode

Set to Position control (typical) or Velocity control mode

Velocity P gainKVP Velocity P gain

0

Velocity I gainKVI Velocity I gain

900

Acceleration feed-forward gainAFF and Velocity feed-forward gainVFF

0

Position P gainKPP Position P gain

150

Position feed-forward gainPFF Position feed-forward gain

100%

Over speed faultFEV Over speed fault

1000

Position tracking error thresholdFPT and Velocity tracking error thresholdFVT fault limits

1000

Other settings are not critical and can be configured as desired (such as acceleration and velocity limits). If setpoint scaling is 1:1 (Setpoint multiplierMUL=Setpoint dividerDIV), then this mode yields resolution of 25600 steps/revolution. If reduction of resolution is required, then adjust scaling accordingly (if scaling is set above 4:1, then try also Setpoint smoothing Setpoint smoothingCIS).

NOTE: these values and settings apply from firmware version 1.2.1 (1064). For older firmware version, check out earlier version of this page here.

Seting up closed loop mode 2

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

Feedback deviceFBD Feedback device

Choose your feedback device (other than None)

Invert feedback directionFBI Invert feedback direction

Try both settings and choose the one with stability

Feedback device resolutionFBR Feedback device resolution

Set your feedback device resolution

Velocity I gainKVI and Position P gainKPP

Tune KVI and KPP values (and possibly other gains if non-zero) to have nice response

Motion fault thresholdFMO Motion fault limit

Set non-zero value (perhaps 100-1000) to cause a fault state when motor stalls

Setting up servo mode 3

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:

Motor typeMT Motor type

2 Phase AC or BLDC

Pole countMPC Pole count

100

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