May 29, 2011

Mint MT Motion Language Programming Tutorial - Part 7

Till now we have learned a lot from our previous tutorials in Mint. In our previous tutorial we saw the useful MINT Motion Keywords and also their syntax and examples. Today in this tutorial we will see the procedure for position control and Homing.

Positional Control in Mint Motion Controllers:-

The controller is an incremental based system capable of using either relative or absolute co-ordinates.The POS keyword monitors the axis position
----- positionHere = POS.3
POS is scaled into user units by the SCALE keyword. The controller maintains a parallel ENCODER position value for servo axes
-----myencoder = ENCODER.0
ENCODER can be scaled by the ENCODERSCALE keyword. POS and ENCODER operate independently (if one is zeroed the other is unaffected). ENCODER still operates for axes configured as _cfOFF

MOVEA keyword performs a move to an absolute position

----- MOVEA.0 = 200 : GO.0 ’Move to user unit position 200

MOVER keyword performs a relative move from the current position

----- MOVER.2 = 100 : GO.2 ‘Move forward 100 user units

No motion occurs until the GO keyword is executed.

Reading the POSTARGET keyword during a positional move will return the absolute end point of the move in progress. Reading the POSREMAINING keyword will return the distance left to travel
The move is executed using a trapezoidal move profile defined with ACCEL, DECEL and SPEEDACCELJERK/DECELJERK provides true “S” curve (Nextmove only). MintDriveII uses SRAMP.

ACCEL, DECEL and SPEED can be changed on the fly (while a move is taking place)
The INCA and INCR keywords perform incremental moves…..the target position of the move in progress is overwritten and the axis will respond immediately using the defined accel / speed / decel profile. See below example.
IF INKEY THEN ‘ Modify target position by 100
INCR=100:GO ‘ every time a key is pressed

Homing Keyword in Mint MT :-

The HOME keyword begins a datum sequence on an axis
The home switch input is user definable with HOMEINPUT, the speed is definable with HOMESPEED
The HOMEBACKOFF keyword specifies a dividing ratio for the backing off speed
HOMESPEED.0=10: HOMEBACKOFF=5 ‘Backoff at 2. Modes added to detect correct edge of sensor after overshoots.

There are now 12 modes of homing, each represented by pre-defined Mint constants
There are Mint constants for each phase of the homing sequence

Reading the HOMEPHASE keyword returns the current phase of the homing sequence
homing_state = HOMEPHASE.1

Complete Step By Step Tutorial on Baldor Servo and Motion Products Programming Tutorial.
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