Robot Device Modules

Show the Device Modules Menu

 

Enhanced XYZ/Theta Device Module

The Enhanced X/Y/Z/Theta (EXY) device module can control up to a four degree-of-freedom mechanism that consists of three orthogonal linear axes followed by a revolute axis.  Typical examples of such mechanisms are linear axes, rotational axes, X/Y tables, and gantry robots.  The kinematic model is the same as the standard X/Y/Z/Theta (XYZ) Device Module, but includes axis linearity compensation and backlash compensation, split axis drive capability, and split axis skew error compensation. For V+ versions 11.0 and higher, the module also supports the two-stage (telescopic) Z axis option. (The feature is implemented in 10.4, but not supported by SPEC until 11.0.)

For a description of the standard X/Y/Z/Theta (XYZ) Device Module, see the X/Y/Z/Theta Device Module documentation.

Module Specifications

Minimum V+ compatibility:  10.1 (10.4 or higher recommended)

V+ License Requirements:  “Kinematics License”

If you install a module for which you do not have a license, an “*Option not installed*” message will be displayed when you restart your system.

Device module name:  EXY

Device Module Identification Number: 18  (8  in V+ 10.X)

18  (V+ 11.0 and higher)
8  (V+ 10.X)

This number is displayed with the robot serial and model number after the system boots up, and whenever the ID monitor command is issued.

Default Startup Message: “Enhanced X/Y/Z/Theta Robot Control Module”

The startup message is displayed just after the system boots up.

Default Joint Configuration (for V+ 11.0 and higher):

Joint	Axis	Board/Channel
1	1 (X)	1/1
2	2 (Y)	1/2
3	3 (Z)	1/3
4	4 (Theta)	1/4

With multiple robots, it will be necessary to correct the joint configuration from the SPEC program to avoid conflicts.

Robot Option Word

Bit 1: Split X-axis option

Turning on bit 1 (least significant bit; option word value 1) of the robot option word enables the split-axis option. See the document Split-Axis Device Module Feature for more information on this feature.

Bit 2: Backlash and linear compensation option

Turning on bit 2 (counting from 1; option word value 2) of the robot option word enables the backlash and linear compensation option. On this module, Linear Compensation may be applied to Joint 1, 2, and 3 (X, Y, and Z) only. See the document Backlash and Linear Compensation for more information on configuring backlash and linear compensation.

Bit 3: Two-stage Z-axis option

Turning on bit 3 (counting from 1; option word value 4) of the robot option word enables the two-stage Z-axis option.

The robot option word can be changed from the “Robot Initialization Specifications” menu of the SPEC utility program. The default value for the option word is zero (all option bits off).

Axis Configuration

Although the system is designed to support up to four axes, any combination of these axes can be selectively disabled to provide control for a lesser degree-of-freedom device. (This is a special feature of the Adept XYZ and EXY modules. Other device modules do not offer this degree of flexibility.)

The directions of motion of the axes as described below will determine the setting of the encoder sign specified in the SPEC utility program (see Figure 1).  The four axes of motion are defined as follows:

1. Joint 1 is a linear axis that moves in the world X direction.  A POSITIVE displacement of the joint moves the robot in the POSITIVE world X direction.

2. Joint 2 is a linear axis that moves in the world Y direction.  A POSITIVE displacement of the joint moves the robot in the POSITIVE world Y direction.

3. Joint 3 is a linear axis that moves in the world Z direction.  A POSITIVE displacement of the joint moves the robot in the NEGATIVE world Z direction.

4. Joint 4 is a revolute axis (theta) about the world Z direction.  A POSITIVE rotation of the joint turns the robot's end effector in a direction opposite to positive rotation around the world Z axis.  The axis of rotation of joint 4 defines the nominal Z axis of the robot's tool frame of reference.  That is, if a NULL tool is defined, the Z axis of the tool frame will be collinear with the axis of rotation of joint 4 and will be pointed in the direction of the negative world Z axis.

As with all other robot modules, the standard V+ BASE and TOOL transformations can be used in combination with the geometric model to specify and compute the end point of the robot relative to the world coordinate frame.

Maximum operating range of rotational joints

This module has one rotary joint. Its maximum operating range is as follows.

Joint 4:            -359.9° to +359.9°

Warning
Be sure to set the software joint limits properly, and verify the settings, before attempting to move the robot in a V+ program. It is especially important for revolute axes to have correct software limits set before attempting any motion instruction. If the limits are improperly set, a revolute axis can rotate unexpectedly in order to stay in range.

Variations in Axis Configuration

This module can be configured to control any combination of the four axes ranging from any single joint on up to all four axes. See Appendix A for information on configuring a split X-axis. See Appendix C for information on configuring a two-stage Z-axis.

Figure 1.  Link Definitions and Dimensions for an X/Y/Z/Theta Device

Geometric Dimensional Constants

There are no dimensional constants that can be specified for this device other than the tool offset distance.  By default, the world Z height is 0 when the Z-axis joint position is 0, and as the Z-axis extends in the positive direction, the world Z-height becomes negative.  The tool offset distance can be used to change the default world Z height of the robot.

The only geometric constraints of importance are that the base linear axes must be mutually perpendicular.  It is not important whether the mechanical drive axes that implement the mechanism are intersecting or offset from one another.  In fact, the origin of the world coordinate system can be arbitrarily defined to be any point relative to the axes drives so long as it is consistently defined from one working session to the next.

Cartesian Motion

During program generated straight line motions, the first Cartesian rotation speed controls the rate at which joint 4 rotates and should be set to be consistent with the joint interpolated speed for joint 4.  If the Theta axis is not configured, the first Cartesian rotation speed should be set to zero.  The second and third Cartesian rotation angles are not utilized and their speeds should likewise be set to zero.

Because the joint axes align with the Cartesian axes, the specification parameters for joint speeds and accelerations should be consistent with those for Cartesian speeds and accelerations for both pendant and program control.  For example, the Cartesian translation speed and acceleration will normally be close to the average of the linear axes’ speeds and accelerations.

Coupling Between Robot Joints and Motors

See Appendix A for information on the split axis option which allows two motors to couple into the motion of joint 1 (the X axis).

See Appendix C for information on configuring a two-stage Z-axis.

Robot Configuration Control Instructions

The following robot configuration-control program instructions do not have any effect upon the operation of mechanisms controlled by this module:

ABOVE, BELOW, FLIP, NOFLIP, LEFTY, RIGHTY

Additional Restrictions

None.