Robot Device Modules

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3-Link SCARA DEVICE MODULE (SC6)

This robot module controls a 3-link SCARA mechanism with 6 axes.  A standard 2-link SCARA mechanism consists of 3 axes, for controlling position, followed by a single wrist axis (vertical roll).  This 3-link SCARA mechanism consists of the same 3 inner axes for positioning, but is followed by a 3 axis wrist (roll-roll-bend).

Refer to the AdeptMotion VME Developer’s Guide or the SmartMotion Developer's Guide for installation instructions.

Module Specifications

Minimum V+ compatibility:  10.4 and higher

V+ License Requirements:  “Kinematics License”

If you install this module but do not have the above license, an “*Option not installed*” message will be displayed when you restart your system.

Device module name:  SC6

Device module identification number:  20

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

Default startup message: "6-Axis SCARA Robot"

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 (Z)

1/1

 2

2 (“shoulder”)

1/2

 3

3 (“elbow”)

1/3

 4

4  (Vertical Roll)

1/4

 5

5 (Horizontal Roll)

2/1

 6

6 (Bend)

2/2

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

Robot Option Word

The robot option word determines whether software limits on motor motion (in addition to the standard limits on joint motion) are to be used. If bit 9 (option word value 256) is set, then software limits on motor motion are used. See the AdeptMotion Servo User's Guide for details on setting the robot option word. Motor motion limits are in units of encoder counts and can be set from the “Motor Motion Parameters” menu in SPEC.)

Axis Configuration

  1. Joint 1 is a linear axis that moves in the world-Z direction.  A positive displacement of this joint moves the robot tool in a positive world-Z direction.  When joint 1 is at its zero position, the Z height of the tool mounting point is equal to the joint-1 offset described below.

  2. Joint 2 is a revolute axis that rotates about the world-Z axis.  A positive change in joint angle corresponds to a positive rotation about the world-Z axis.  When joint 2 is positioned at zero degrees, the inner link (the link between joint 2 and joint 3) points along the world-X axis.  When joint 2 is positioned at 90 degrees, the inner link points along the world-Y axis.

  3. Joint 3 is a revolute axis whose axis of rotation is parallel to the second joint.  A positive change in joint angle corresponds to a positive rotation about an axis parallel to the world-Z axis.  When joints 2 and 3 are positioned at zero, both the inner and the middle links point along the world-X axis.  If joint 3 is subsequently rotated to 90 degrees, the middle link points in the positive world-Y direction.

  4. Joint 4 is a revolute axis whose axis of rotation is parallel to the second and third joints.  A positive change in its joint angle corresponds to a positive rotation about an axis that is parallel to the world-Z axis.  When joints 2, 3, and 4 are at their zero positions, the inner, middle, and outer links point along the world-X axis.  If joint 4 is subsequently rotated by 90 degrees, the outer link points in the positive world-Y direction.

  5. Joint 5 is a revolute axis that rotates about the principal axis of the outer link.  That is, when joints 2, 3, and 4 are at their zero positions, joint 5 rotates about an axis that is parallel to the world-X axis.  In this configuration, a positive change of the joint-5 angle corresponds to a positive rotation about an axis parallel to the world-X axis.  Also, in this configuration, when joint 5 is at its zero position, joint 6 rotates about a horizontal axis parallel to the world-Y axis.

  6. Joint 6 is a revolute wrist bend axis that is perpendicular to joint 5.  When joints 2, 3, 4, and 5 are at their zero positions, joint 6 rotates about an axis that is parallel to the world-Y axis.  In this configuration, a positive change of the joint-6 angle corresponds to a positive rotation about an axis parallel to the world-Y axis.  When joint 6 is in its zero position, the Z axis for the tool mounting plate is collinear with the axis of joint 5 and points away from joint 4.  When joints 2, 3, 4, 5, and 6 are at their zero positions, the Z axis of the tool mounting plate is parallel to the world-X axis and the Y axis of the tool mounting plate is parallel to the world-Y axis.

Maximum operating range of rotational joints

WARNING
The travel of joint 5 must always be restricted to be within -89 to +89 degrees. Travel beyond this range will encounter a degeneracy and will cause unpredictable behavior.

This module has five rotary joints. Their maximum operating range is as follows. See also sections 12.2 and 12.10.

Joints 2, 3, 4, 6:           -179.9° to +179.9°
Joint 5:                         -89° to +89°

WARNING
Be sure to set the software joint limits properly 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

All six axes must be configured for this robot module.

Link Dimensions (Geometric Dimensional Constants)

Tool Z-offset distance

The Tool Z-offset distance defines the distance from the center of the wrist to the tool mounting flange. For this module, the Tool Z-offset distance is the distance from the intersection of axes 5 and 6 to the center of the joint 6 mounting flange. In other words, it is the radius of the arc that the tool flange moves through when joint 6 is rotated.

Other Dimensional Constants

In addition to the Tool Z-offset distance, there are eight other dimensional constants that are utilized by this module. The constants are a function of four primary parameters:

The SPEC program will prompt for all eight constants. The user should calculate and enter these values to eight significant figures (seven decimal places). See the table below and Figure 1 for more information.

Link Dimension Parameters for 3-Link SCARA Robot

Parameter

Units

Value

Length of inner link

mm

a2

Length of middle link

mm

a3

Height of tool flange

mm

s1 off

 

 

a22 + a32

 

 

a22  a3

 

 

a2  a3)2

 

 

a2  a3  SIN(10°)

Length of outer link

mm

a4

 

Figure 1.  Link Definitions and Dimensions for 3-link SCARA Robot

Interpretations of Cartesian Rotation

This module employs a general 6 degree-of-freedom Cartesian rotation interpolator to control the change in orientation of the tool during straight-line motions.  This interpolator utilizes two angles to characterize the rotational change:  a first angle that controls the direction of the tool-Z axis, and a second angle that controls the orientation of the tool about its Z axis.  During a motion, the first angle moves the Z axis of the tool along a great circle from its initial to its final orientation, while the second axis rotates the tool about its primary axis.

Coupling Between Robot Joints and Motors

This module does not allow multiple motors to couple into the motion of any single axis of rotation.

Robot Configuration Control Program Instructions

The following robot configuration-control program instructions are utilized to specify the range of motion for joint 3:

            LEFTY, RIGHTY

(see the V+ Reference Guide for more information on these 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

Additional Restrictions

None.

 

Last modified on: 02/13/2007
Copyright © 2007 by Adept Technology, Inc.
All rights reserved.