104 Rockwell Automation Publication MOTION-UM002E-EN-P - June 2016
Chapter 7 Configure a Cartesian H-bot
• Motors A and B are both rotated clockwise at the same speed, then the
machine moves along a horizontal line
• Motors A and B are both rotated counterclockwise at the same speed
then the machine moves along a vertical line
Any X,Y position can be reached by properly programming the two motors.
For example, a move of (X1 = 10, X2 = 0) causes the X1X2 axes to move to a
position of (X1=7.0711, X2=7.0711). A move to (X1=10, X2 =10) causes the
robot to move to a position of (X1=0, X2=14.142).
While this configuration can be very confusing for a programmer, utilizing the
Logix Designer application Kinematics function configured with two
Cartesian coordinate systems and a -45 rotation easily performs the function.
To configure two Cartesian coordinate systems, Coordinate system 1 (CS1)
and Coordinate system 2 (CS2), each containing two linear axes, use the
following steps.
1. Configure CS1 to contain the virtual X1 and X2 axes.
2. Configure CS2 to contain the real X1 and X2 axes.
3. Configure the Orientation vector of the MCT instruction as (0,0, -45),
a negative degree rotation around the X3 axis.
4. Configure the Translation vector as (0, 0, 0).
5. Link the CS1 and CS2 by using a MCT instruction.
6. Home the H-bot and then program all moves in CS1.
The machine moves the tool center point (TCP) to the programmed coordinates in
CS2. The
-45 rotation introduced by the Kinematics, counteracts the 45
rotation introduced by the mechanics of the machine and the H-bot moves to the CS1
configured coordinates. As a result, a programmed move of X1virt=10, X2virt=5
moves to a real mechanical position of X1=10, X
2=5.
Establish the Reference
Frame for a Cartesian H-bot
For a Cartesian H-bot, the Base coordinate system is an orthogonal set of X1,
X2 axes postponed anywhere on the Cartesian H-bot. Do not rotate the
angular rotation of the reference frame for this robot because the angular
rotation vector is used to achieve the 45 rotation required for mechanical
operation.
Identify the Work Envelope
for a Cartesian H-bot
The work envelope for a Cartesian H-bot is a rectangle of length and width
equal to the axis soft travel limits.
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