Defining Cartesian Groups

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Introduction

Cartesian groups are enhancements of groups. Like groups, they are a collection of axes that can be moved together. In addition, they have a predefined Cartesian model for defining the roll of each axis in the Cartesian space.

Creating a Cartesian Group

Cartesian groups are defined similar to ordinary groups, either in configuration file or as a terminal input. The only difference is that at the end the type of the group is defined by: model=1 of <point type>, where <point type> is a string that defines the actual Cartesian model, which can be one of the following:

Mnemonic Constant
used in CASTPOINT
Numerical Value
used in CASTPOINT Function
<point type>
String
Explanation
NO_ROBOT 0 NONE List-of-coordinates, uninitialized generic points
TYPE_X 1 X X coordinate only
TYPE_XY 2 XY X Y table
TYPE_XYZ 3 XYZ X Y Z
TYPE_XYZU 4 XYZU
TYPE_XYZUV 5 XYZUV
TYPE_XYZUVW 6 XYZUVW
TYPE_XYR 7 XYR X Y Roll
TYPE_XYRZ 8 XYRZ
TYPE_XYRZU 9 XYRZU
TYPE_XYRZUV 10 XYRZUV
TYPE_XYZR 11 XYZR X Y Z Roll
TYPE_XYZRU 12 XYZRU
TYPE_XYZRUV 13 XYZRUV
TYPE_XYZURV 14 XYZURV
TYPE_XYZUR 15 XYZUR
TYPE_XYZRPU 16 XYZRPU
TYPE_XYZRP 17 XYZRP X Y Z Roll Pitch
TYPE_XYRURV 18 XYZRURV
TYPE_XYRUR 19 XYRUR
TYPE_XYRP 20 XYRP X Y Roll Pitch
TYPE_XYRPU 21 XYRPU
TYPE_XYRPUV 22 XYRPUV
TYPE_XYRPUQ 23 XYRPUQ
TYPE_XYZYPR 24 XYZYPR X Y Z Yaw Pitch Roll
TYPE_XYZPR 36 User defined point
TYPE_XYZA 37 XYZA X Y Z A-angle
TYPE_XYZAB 38 XYZAB X Y Z A-angle B-angle
TYPE_YPR 50 YPR Yaw Pitch Roll
TYPE_PR 51 PR Pitch Roll
TYPE_R 52 R Roll

For example, the following defines a Cartesian group called GXYZ:

common shared GXYZ   as group Axnm = a1 Axnm = a2 Axnm = a3 model=1  of xyz

Usage

Cartesian groups implement robot models with 1-1 Inverse and Direct kinematics functions. For example, an XY Cartesian group is defined by following mapping:

J1 ←→ X
J2 ←→ Y

This means that coordinates of <group.setpoint and <group>.pcmd will have equal values.

Translation vs. Rotation

The greatest difference between ordinary groups and Cartesian groups is the separation of translational and rotational movements. This further means that axis type must mach the Cartesian model:

For example, in XYR group (X, Y and Roll) axistype must be set as:

Common Shared GXYR as Group AxisName=A1 AxisName=A2 AxisName=A3 model = 1 of XYR
...
a1.axistype = 1
a2.axistype = 1
a3.axistype = 1
ConfigGroup GXYR

If axis type is not properly set, ConfigGroup command will return an error. When such a group is properly set it allows setting physical kinematics values of velocity, acceleration and jerk separated into translational and rotational parts in the same way it is done in robot models:

MoveS GXYR #{100,100,90} VelTran=100 VelRot=20

This will move the GXYR to the target point (X=100mm, Y=100mm, R = 90deg) with 100 mm/sec or 20 deg/sec, depending on which values dominates (takes more time).

Motion

The following motion interpolation types are defined in Cartesian groups:

  • Move - joint interpolations, used Vcruise, Vfinal in non-physical user units.
  • MoveS - "straight-line" interpolation with separated kinematics parameters (Vtra/Vrot, Atran/Arot, Jtran/Jrot) defined in physical units for rotation and translation.
  • Circle - circular/helycal interpolation in XYZ space with proportional change of additional rotation axes with separated kinematics parameters (Vtra/Vrot, Atran/Arot, Jtran/Jrot) defined in physical units for rotation and translation.


NOTE-Info.svgNOTE
There is no difference in the path of Move and Moves interpolation, except for how the time derivatives are determined.