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Digital Halls with Vertical Axis


MattReid
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Hi,

 

I am trying to use digital halls with a vertical axis and use the digital halls to phase the motor without motion by issuing a #3$ upon power up. Most of the time this works well but the odd time it fails.

When it fails:

1. If I try to jog the axis up, it constantly gets an I2C error

2. If I re-issue a #3$, it rapidly moves a short distance, but seems to correctly phase and I have full torque of the axis.

3. I use amp enable signal to determine if my brake is on or off.

 

Any ideas why this would fail the odd time with a vertical axis?

Any way to verify if my UVW are correct. I set up Ix80, Ix81, Ix91 using the HallsUVW.exe application, it works correctly.

 

Matt

 

 

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Hi,

 

I am trying to use digital halls with a vertical axis and use the digital halls to phase the motor without motion by issuing a #3$ upon power up. Most of the time this works well but the odd time it fails.

When it fails:

1. If I try to jog the axis up, it constantly gets an I2C error

2. If I re-issue a #3$, it rapidly moves a short distance, but seems to correctly phase and I have full torque of the axis.

3. I use amp enable signal to determine if my brake is on or off.

 

Any ideas why this would fail the odd time with a vertical axis?

Any way to verify if my UVW are correct. I set up Ix80, Ix81, Ix91 using the HallsUVW.exe application, it works correctly.

 

Matt

 

If you can find it, Delta Tau once has a vary good applications note titled Hall Effect Phasing that covers determining the value for Ix91.

Halls are only a rough estimate that result in +/- 30 degrees of variation in phase angle, which translates to around a 13% loss of torque. This will be a random variation depending on where the axis powers-up. In these cases it is best limit speeds and accelerations until you have homed and to apply a fine phase offset (Ix75) as part of your homing procedure with the setphase command to apply the correct phase value at a known position instead of the initial estimate.

Assuming standard hall configuration, to determine the phase correction value at home, Home the axis to establish your reference position. Watch Mx71 and slow jog your motor until it wraps around. From that point watch Mx28 and slowly jog to either side of the wrap around position noting axis position where the hall change state. Move the axis to the point half way between these transitions and set Mx71=0. Move the axis back to the home position and set Ix75=Mx71.

Note that this same approach can be used to check for correct hall alignment if you start from a hand phased motor (ie: set Ix79 to some positive value if Ix72=683 or a negative value if Ix72=1365 and enabling the amplifier with #xo0. When the motor settles set Mx71=0, kill the axis and return Ix79 to zero) From the Mx71 rollover position the hall transitions should be a symmetrical distance either side.

 

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All the points which Jeff highlighted are in the Geo Brick Drive manual. Suggested M-Variable Mxx28 should show you the halls state when you move the motor.

 

Make sure that bus power is applied before you issue a #3$ on power up, even though halls do not require motion, it will need to apply torque to hold position, especially with a vertical axis.

 

The failure could be due to the inherent or marginal halls phasing error:

1. The I2T is due to incorrect phasing, which results in large current draw

2. The short distance jump is probably due to gravity or bad phasing

3. Using amp enable signal for the brake in a PLC is fine, but for phasing you might want to disable this logic And phase to halls with the brake on initially, then release it shortly after.

 

I would do the following:

1. Phase the motor manually as best as possible by forcing it hard to a phase. You might have to inject current with the brake on, then release it to allow the motor to cog to the phase.

2. Make sure you can jog along the entire travel once the manual phasing procedure is executed.

3. Use the halls.exe (uncheck the phase motor before test box, this will overwrite your good manual phasing) or use the manual procedure in the manual to implement halls phasing. Repeat test or plot a few times to see how consistent the Hall zero angle is.

4. Home the motor (with or without offset) as you would in normal power-on operation. Record Mxx71 at the home location.

 

Now you would, on power-up, phase to halls and home, then correct Mxx71 at home location (can be done on the fly with the motor servo-ing in position).

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