Delta Tau GEO BRICK LV User Manual
Turbo PMAC User Manual
Setting Up a Coordinate System
259
The PMATCH function assumes that the position referencing – either a homing search move or an absolute
position-sensor read – has been done for each motor in the coordinate system. Each motor has a home
complete status bit that is set true if either has been done, and to check for this, do it at the application
level.
Some users will want to read instantaneous motor position registers (particularly motor actual position) –
Turbo PMAC does not compute instantaneous axes positions automatically – and convert them to axis
positions for position-reporting purposes. These forward-kinematic calculations must be done at the
application level, either in Turbo PMAC (usually in a PLC program) or in the host computer.
position-sensor read – has been done for each motor in the coordinate system. Each motor has a home
complete status bit that is set true if either has been done, and to check for this, do it at the application
level.
Some users will want to read instantaneous motor position registers (particularly motor actual position) –
Turbo PMAC does not compute instantaneous axes positions automatically – and convert them to axis
positions for position-reporting purposes. These forward-kinematic calculations must be done at the
application level, either in Turbo PMAC (usually in a PLC program) or in the host computer.
Coordinate-System Kinematic Calculations
Turbo PMAC provides structures that enable easy implementation and execution of complex kinematic
calculations. Kinematic calculations are required when there is a non-linear mathematical relationship
between the tool-tip coordinates and the matching positions of the actuators (joints) of the mechanism,
typical in non-Cartesian geometries. They are used most commonly in robotic applications, but can be
used with other types of actuators that are not considered robotic. For example, in 4-axis or 5-axis
machine tools with one or two rotary axes, it is desirable to program the cutter-tip path and let the
controller compute the necessary motor positions.
This capability permits the motion for the machine to be programmed in the natural coordinates of the
tool-tip – usually Cartesian coordinates, whatever the underlying geometry of the machine. The kinematic
routines are embedded in the controller by the integrator, and operate invisibly to the people programming
paths and the machine operators. These routines can be unchanging for the machines, but with
parameterization and/or logic, they can adapt to normal changes such as tool lengths and different end-
effectors.
In Turbo PMAC terminology, the tool-tip coordinates are for axes, which are specified by letter, and have
user-specified engineering units. The joint coordinates are for motors, which are specified by numbers,
and have the raw units of “counts”.
calculations. Kinematic calculations are required when there is a non-linear mathematical relationship
between the tool-tip coordinates and the matching positions of the actuators (joints) of the mechanism,
typical in non-Cartesian geometries. They are used most commonly in robotic applications, but can be
used with other types of actuators that are not considered robotic. For example, in 4-axis or 5-axis
machine tools with one or two rotary axes, it is desirable to program the cutter-tip path and let the
controller compute the necessary motor positions.
This capability permits the motion for the machine to be programmed in the natural coordinates of the
tool-tip – usually Cartesian coordinates, whatever the underlying geometry of the machine. The kinematic
routines are embedded in the controller by the integrator, and operate invisibly to the people programming
paths and the machine operators. These routines can be unchanging for the machines, but with
parameterization and/or logic, they can adapt to normal changes such as tool lengths and different end-
effectors.
In Turbo PMAC terminology, the tool-tip coordinates are for axes, which are specified by letter, and have
user-specified engineering units. The joint coordinates are for motors, which are specified by numbers,
and have the raw units of “counts”.
Note:
PMAC’s standard axis-definition statements handle linear mathematical
relationships between joint motors and tool-tip axes. This section pertains to the
more difficult case of the non-linear relationships.
relationships between joint motors and tool-tip axes. This section pertains to the
more difficult case of the non-linear relationships.
The forward-kinematic calculations use the joint positions as input, and convert them to tool-tip
coordinates. These calculations are required at the beginning of a sequence of moves programmed in tool-
tip coordinates to establish the starting coordinates for the first programmed move. The same type of
calculations can also be used to report the actual position of the actuator in tool-tip coordinates, converting
from the sensor positions on the joints. (The Turbo PMAC forward-kinematic program buffer does not
support this position-reporting functionality, but functionally identical calculations can be used in a PLC
program for this purpose.)
The inverse-kinematic calculations use the tool-tip positions as input, and convert them to joint
coordinates. These calculations are required for the end-point of every move that is programmed in tool-
tip coordinates, and if the path to the end-point is important, they must be done at periodic intervals during
the move as well.
coordinates. These calculations are required at the beginning of a sequence of moves programmed in tool-
tip coordinates to establish the starting coordinates for the first programmed move. The same type of
calculations can also be used to report the actual position of the actuator in tool-tip coordinates, converting
from the sensor positions on the joints. (The Turbo PMAC forward-kinematic program buffer does not
support this position-reporting functionality, but functionally identical calculations can be used in a PLC
program for this purpose.)
The inverse-kinematic calculations use the tool-tip positions as input, and convert them to joint
coordinates. These calculations are required for the end-point of every move that is programmed in tool-
tip coordinates, and if the path to the end-point is important, they must be done at periodic intervals during
the move as well.