Galil DMC-1800, DMC-1700 user manual Tune the Servo System

for an external connection. If an encoder is used for position feedback, connect the encoder to the main encoder input corresponding to that axis. The commanded position of the stepper can be interrogated with RP or DE. The encoder position can be interrogated with TP.

The frequency of the step motor pulses can be smoothed with the filter parameter, KS. The KS parameter has a range between 0.5 and 8, where 8 implies the largest amount of smoothing. See Command Reference regarding KS.

The DMC-1700/1800 profiler commands the step motor amplifier. All DMC-1700/1800 motion commands apply such as PR, PA, VP, CR and JG. The acceleration, deceleration, slew speed and smoothing are also used. Since step motors run open-loop, the PID filter does not function and the position error is not generated.

To connect step motors with the DMC-1700/1800 you must follow this procedure: Step A. Install SM jumpers

Each axis of the DMC-1700/1800 that will operate a stepper motor must have the corresponding stepper motor jumper installed. For a discussion of SM jumpers, see Chapter Two: Step 2. Install Jumpers on the DMC-1700/1800.

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Step B. Connect step and direction signals from controller to motor amplifier

from the controller to respective signals on your step motor amplifier. (These signals are labeled PULSX and DIRX for the x-axis on the ICM-1900). Consult the documentation for your step motor amplifier.

Step C. Configure DMC-1700/1800 for motor type using MT command. You can configure the DMC-1700/1800 for active high or active low pulses. Use the command MT 2 for active high step motor pulses and MT -2 for active low step motor pulses. See description of the MT command in the Command Reference.

Step 9. Tune the Servo System

Adjusting the tuning parameter is required when using servo motors (standard or sinusoidal commutation). The system compensation provides fast and accurate response and the following presentation suggests a simple and easy way for compensation. More advanced design methods are available with software design tools from Galil, such as the Servo Design Kit (SDK software )

The filter has three parameters: the damping, KD; the proportional gain, KP; and the integrator, KI. The parameters should be selected in this order.

To start, set the integrator to zero with the instruction KI 0 (CR) Integrator gain

and set the proportional gain to a low value, such as

KP 1 (CR)	Proportional gain
KD 100 (CR)	Derivative gain

For more damping, you can increase KD (maximum is 4095). Increase gradually and stop after the motor vibrates. A vibration is noticed by audible sound or by interrogation. If you send the command

TE X (CR) Tell error

a few times, and get varying responses, especially with reversing polarity, it indicates system vibration. When this happens, simply reduce KD.

Next you need to increase the value of KP gradually (maximum allowed is 1023). You can monitor the improvement in the response with the Tell Error instruction

KP 10 (CR)	Proportion gain
TE X (CR)	Tell error

As the proportional gain is increased, the error decreases.

34 • Chapter 2 Getting Started DMC-1700/1800