Galil DMC-2X00 user manual Connect Step Motors, Tune the Servo System

Step 9c. Connect Step Motors

In Stepper Motor operation, the pulse output signal has a 50% duty cycle. Step motors operate open loop and do not require encoder feedback. When a stepper is used, the auxiliary encoder for the corresponding axis is unavailable 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 TD. 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-2x00 profiler commands the step motor amplifier. All DMC-2x00 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-2x00 you must follow this procedure: Step A. Install SM jumpers

Each axis of the DMC-2x00 that will operate a stepper motor must have the corresponding stepper motor jumper installed. For a discussion of SM jumpers, see section Step 2. Install Jumpers on the DMC-2x00.

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 A-axis on the ICM-2900). Consult the documentation for your step motor amplifier.

Step C. Configure DMC-2x00 for motor type using MT command. You can configure the DMC- 2x00 for active high or active low pulses. Use the command MT 2 for active low step motor pulses and MT -2 for active high step motor pulses. See description of the MT command in the Command Reference.

Step 10. Tune the Servo System

Adjusting the tuning parameters 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 <return> Integrator gain

and set the proportional gain to a low value, such as KP 1 <return> Proportional gain

KD 100 <return> Derivative gain

30 • Chapter 2 Getting Started DMC-2X00