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User Manual Appendix D

GFK-1742F Jan 2020

Tuning Digital and Analog Servo Systems 432

negative axis directions. If the motor moves in the POSITIVE direction but the

DSM314 reports that Actual Velocity is NEGATIVE, then the encoder channel A and

channel B inputs must be swapped.

Record the actual motor velocity reported by the Motion Mate DSM314 with a 1.0

volt velocity command. Multiply this velocity by 10 and update the Velocity at Max

Cmd entry in the DSM314 configuration, if necessary. Initially set the Pos Loop Time

Constant (0.1 ms) configuration parameter to a high value (typically 100 ms or a

value of 1000 in the configuration).

Turn on the %Q Jog Plus bit. Confirm that the servo moves in the proper direction

and that the Actual Velocity reported by the Motion Mate DSM314 in the %AI table

matches the configured Jog Velocity. If Motion Programs will use an acceleration

higher than the Jog Acceleration, it may be necessary to increase Jog Acceleration so

that Abort All Moves and Normal Stop actions will operate as expected.

With the Drive Enabled %Q bit ON and no servo motion commanded, adjust the

servo drive command offset adjustment for zero Position Error. The integrator

should be OFF during this process.

10.

Check for proper operation of the Find Home cycle by momentarily turning on the

%Q Find Home bit (the Drive Enabled %Q bit must also be maintained ON). The axis

should move towards the Home Switch at the configured Find Home Velocity, then

seek the Encoder Marker at the configured Final Home Velocity. If necessary, adjust

the configured velocities and the location of the Home Switch for consistent

operation. The final Home Switch transition MUST occur at least 10 ms before the

Encoder Marker Pulse is encountered. The physical location of Home Position can

then be adjusted by changing the Home Offset value in the Configuration Software.

11.

Monitor servo performance and use the %Q Jog Plus and Jog Minus bits to move the

analog servo motor in each direction. The Position Loop Time Constant can be

temporarily modified by placing the correct command code in the %AQ table. For

most systems the Position Loop Time Constant can be reduced until some servo

instability is noted, then increased to a value approximately 50% higher. Once the

correct time constant is determined, the DSM314 configuration should be updated

using the Configuration Software. Velocity Feedforward can also be set to a non-

zero value (typically 90-100 %) for optimum servo response.

Note: For proper servo operation, the Configuration entry for Velocity at Max Cmd MUST be set

to the actual servo velocity (in User Units/sec) caused by a 10 Volt Velocity command to

the amplifier.

Emerson DSM314 User Manual

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