Theta 1-2 Robot Device Module
The Theta 1-2 Robot device module file contains a special 2-axis device module for controlling a robot with two rotational axes.
Copying the Device Module File to a Boot Disk
In order to control a mechanism, the device module file must be transferred to the system boot disk. Refer to the “Software Configuration” chapter in the Adept SmartMotion Developer’s Guide for details on using CONFIG_C and SPEC utilities to install and configure this device module file on your system boot disk.
The CONFIG_C utility will prompt you for the disk containing the device modules. Next, you will be prompted to enter the name of the device module you want to transfer to your system disk; enter the answer "T12" to the prompt. Optionally, you can enter a "?" to the name prompt and the available device module names will be displayed.
Theta 1-2 Parallelogram Robot Device Module Description
This robot module controls a mechanism with two degrees of freedom, which consists of two revolute joints that drive a parallelogram mechanism. As a result of the parallelogram structure, the orientation of the tool mounting flange remains fixed as the two joints move.
Module Specifications
Minimum V+ compatibility:
10.2
V+ License Requirements:
Kinematics Modules license
Device module name:
T12
Device module ID number:
10
(The ID 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:
The following startup message is displayed just after the system boots up.
'Theta 1-2 Robot Control Module'
Default Joint Configuration:
Joint
Axis
Board/Channel
1
1 (inner link)
4/1
2
2 (outer link)
4/2
If your system has multiple robots, you need to correct the joint configuration from 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 8 (option word mask value 256) is set, 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 the SPEC utility.
Axis Configuration
Joint 1
This is a revolute axis that rotates about an axis that is parallel to the world Y axis. A positive change in joint angle corresponds to a negative rotation about an axis parallel to the world Y axis. When joint 1 is positioned at zero degrees, the inner link (the link between joint 1 and joint 2) will point in the direction of the world X axis. If joint 1 were positioned at +90 degrees, the inner link would point up along the world Z axis.
Joint 2
This is a revolute axis whose axis of rotation is parallel to the first joint. A positive change in joint angle corresponds to a negative rotation about an axis parallel to the world Y axis. When joints 1 and 2 are positioned at zero, both the inner and the outer links will point along the world X axis. If joint 2 were subsequently rotated to the angle +90 degrees, the outer link would point up in the world Z direction.
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.
Variations in Axis Configuration
This module must always have both joints configured.
Geometric Dimensional Constants
This device module uses five dimensional constants (see the table and figure below):
The “Tool Z-offset”, which defines the offset from the end of the second link to the center of the tool flange along the tool Z-direction.
The “Tool X-offset”, which defines the offset from the end of the second link to the center of the tool flange along the tool X-direction.
The length of the inner link (the distance from the first to the second joint axes),
The length of the outer link (the distance from the second joint axis to the tool mounting flange),
The height of the joint-1 axis of rotation above the X-Y world plane.
Link Dimension Parameters for Theta 1-2 Parallelogram Robot
Label
Parameter
Units
Default Value
Tool Z Offset
Tool Z-offset distance
mm
0
Tool X Offset
Tool X-offset distance
mm
0
a1
Length of inner link
mm
300
a2
Length of outer link
mm
250
s0
Height from base to tool flange or
joint 1mm
336
Link Definitions and Dimensions for Theta 1-2 Robot
Cartesian Motion
Because the orientation is fixed, the program control Cartesian rotation parameters are not used, and their speeds should be set to zero.
Coupling Between Robot Joints and Motors
The motors couple into the motion of the two joints as follows:
J1 = M1 J2 = M2 – M1
Where J1 and J2 are the joint-1 and joint-2 angles, and M1 and M2 are the motor angles. Because no motor-to-joint coupling is taken into account during calibration (the robot calibrates the MOTOR, not the JOINT), the user must keep these equations in mind when setting calibration parameters. Motor 1 should be calibrated first, and joint 1 put at a known position. Then motor 2 can be calibrated, keeping in mind that the joint-2 position is the difference between the motor-2 and motor-1 positions.
Robot Configuration-Control Instructions
The following robot configuration-control program instructions are used to specify the range of motion for joint 2:
ABOVE, BELOW
(See the V+ Language 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:
LEFTY, RIGHTY, FLIP, NOFLIP
Additional Restrictions
None
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Last modified on:
05/02/2007
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