Galil Motion Control DMC-42 0 Series, User Manual

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Homing
The Find Edge (FE) and Home (HM) instructions may be used to home the motor to a mechanical reference. This
reference is connected to the Home input line. The HM command initializes the motor to the encoder index pulse
in addition to the Home input. The configure command (CN) is used to define the polarity of the home input.
The Find Edge (FE) instruction is useful for initializing the motor to a home switch. The home switch is connected
to the Homing Input. When the Find Edge command and Begin is used, the motor will accelerate up to the slew
speed and slew until a transition is detected on the Homing line. The motor will then decelerate to a stop. A high
deceleration value must be input before the find edge command is issued for the motor to decelerate rapidly after
sensing the home switch. The Home (HM) command can be used to position the motor on the index pulse after
the home switch is detected. This allows for finer positioning on initialization. The HM command and BG
command causes the following sequence of events to occur.
Stage 1:
Upon begin, the motor accelerates to the slew speed specified by the JG or SP commands. The direction of its
motion is determined by the state of the homing input. If _HMX reads 1 initially, the motor will go in the reverse
direction first (direction of decreasing encoder counts). If _HMX reads 0 initially, the motor will go in the forward
direction first. CN is the command used to define the polarity of the home input. With CN,-1 (the default value) a
normally open switch will make _HMX read 1 initially, and a normally closed switch will make _HMX read zero.
Furthermore, with CN,1 a normally open switch will make _HMX read 0 initially, and a normally closed switch will
make _HMX read 1. Therefore, the CN command will need to be configured properly to ensure the correct
direction of motion in the home sequence.
Upon detecting the home switch changing state, the motor begins decelerating to a stop.
Note: The direction of motion for the FE command also follows these rules for the state of the home input.
Stage 2:
The motor then traverses at HV counts/sec in the opposite direction of Stage 1 until the home switch toggles again.
If Stage 3 is in the opposite direction of Stage 2, the motor will stop immediately at this point and change direction.
If Stage 2 is in the same direction as Stage 3, the motor will never stop, but will smoothly continue into Stage 3.
Stage 3:
The motor traverses forward at HV counts/sec until the encoder index pulse is detected. The motor then
decelerates to a stop and goes back to the index.
The DMC-42x0 defines the home position as the position at which the index was detected and sets the encoder
reading at this point to zero.
The 4 different motion possibilities for the home sequence are shown in the following table.
Direction of Motion
Switch Type CN Setting Initial _HMX state Stage 1 Stage 2 Stage 3
Normally Open CN,-1 1 Reverse Forward Forward
Normally Open CN,1 0 Forward Reverse Forward
Normally Closed CN,-1 0 Forward Reverse Forward
Normally Closed CN,1 1 Reverse Forward Forward
Chapter 6 Programming Motion ▫ 99 DMC-42x0 User Manual