Galil DMC-2X00 user manual Motion Complete Trip point, Using an Encoder with Stepper Motors

First, the controller generates a motion profile in accordance with the motion commands.

Second, the profiler generates pulses as prescribed by the motion profile. The pulses that are generated by the motion profiler can be monitored by the command, RP (Reference Position). RP gives the absolute value of the position as determined by the motion profiler. The command, DP, can be used to set the value of the reference position. For example, DP 0, defines the reference position of the A axis to be zero.

Third, the output of the motion profiler is filtered by the stepper smoothing filter. This filter adds a delay in the output of the stepper motor pulses. The amount of delay depends on the parameter which is specified by the command, KS. As mentioned earlier, there will always be some amount of stepper motor smoothing. The default value for KS is 1.313 which corresponds to a time constant of 3.939 sample periods.

Fourth, the output of the stepper smoothing filter is buffered and is available for input to the stepper motor driver. The pulses which are generated by the smoothing filter can be monitored by the command, TD (Tell Dual). TD gives the absolute value of the position as determined by actual output of the buffer. The command, DP sets the value of the step count register as well as the value of the reference position. For example, DP 0, defines the reference position of the A axis to be zero.

Motion Profiler

Reference Position (RP)

Stepper Smoothing Filter

(Adds a Delay)

Output Buffer

Step Count Register (TD)

Output

(To Stepper Driver)

Figure 6.8 - Velocity Profiles of ABC

Motion Complete Trip point

When used in stepper mode, the MC command will hold up execution of the proceeding commands until the controller has generated the same number of steps out of the step count register as specified in the commanded position. The MC trip point (Motion Complete) is generally more useful than AM trip point (After Motion) since the step pulses can be delayed from the commanded position due to stepper motor smoothing.

Using an Encoder with Stepper Motors

An encoder may be used on a stepper motor to check the actual motor position with the commanded position. If an encoder is used, it must be connected to the main encoder input.

NOTE: The auxiliary encoder is not available while operating with stepper motors. The position of the encoder can be interrogated by using the command, TP. The position value can be defined by using the command, DE.

NOTE: Closed loop operation with a stepper motor is not possible without special firmware. Contact Galil for more information.

Command Summary - Stepper Motor Operation

command

DE

DP

IT

KS

description

Define Encoder Position (When using an encoder) Define Reference Position and Step Count Register Motion Profile Smoothing - Independent Time Constant Stepper Motor Smoothing

62 • Chapter 6 Programming Motion DMC-2X00