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72 • Chapter 6 Programming Motion DMC-2X00
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 velocity profile
generated is shown in Fig. 6.10.
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 command sequence HM and BG
causes the following sequence of events to occur.
1. Upon begin, motor accelerates to the slew speed. The direction of its motion is determined by
the state of the homing input. A zero (GND) will cause the motor to start in the forward
direction; +5V will cause it to start in the reverse direction. The CN command is used to
define the polarity of the home input.
2. Upon detecting the home switch changing state, the motor begins decelerating to a stop.
3. The motor then traverses very slowly back until the home switch toggles again.
4. The motor then traverses forward until the encoder index pulse is detected.
5. The DMC-2x00 defines the home position (0) as the position at which the index was detected.
Example
Instruction Inter
p
retation
#HOME Label
AC 1000000 Acceleration Rate
DC 1000000 Deceleration Rate
SP 5000 Speed for Home Search
HM A Home A
BG A Begin Motion
AM A After Complete
MG "AT HOME" Send Message
EN En
d
#EDGE Label
AC 2000000 Acceleration rate
DC 2000000 Deceleration rate
SP 8000 Spee
d
FE B Find edge comman
d
BG B Begin motion
AM B After complete
MG "FOUND HOME" Send message
DP,0 Define position as 0
EN En
d