Actuator Angle Monitoring
In V3.410+ of the motion software
the facility to monitor actuator angles has been added. When
monitoring is enabled the actuator angles are monitored
continuously. When the angle between an actuator and the platform
base, or between an actuator and the moving plane of the platform
becomes too acute the motion software will limit the cues.
The cue output is resumed once new
cue conditions arise that no longer cause the acute angle limits to
Angle monitoring can be used to
prevent some conditions in which a platform/actuator
allows contact between the actuators and each other or the platform
structure when the actuators are moved within their normal working
ranges. The feature should be used cautiously - the best way to ensure
a safe operating envelope for a motion platform is to ensure the
actuator placement and strokes are such that their mechanical stops
effectively limit movement to within safe ranges.
Angle monitoring is enabled in the .bff configuration
file. The following parameters should be added to the .bff file
before the End of File indicator:
;Actuator angle monitoring - enable
;Monitor_Acts is an 8 bit binary number to switch angle monitoring
on or off for individual actuators
;Bits are in order b7 b6 b5 b4 b3 b2 b1 b0
;b0 = switch monitoring for ALL actuators on=1 or off=0
;b1 = actuator 1 on=1 or off=0, b2 = actuator 2 on/off etc
;00000001 = switch
angle monitoring for all actuators ON
;00001100 = switch
angle monitoring for actuators 2 & 3 ON
;Actuator minimum permitted angle relative to base of platform -
;Actuator minimum permitted angle relative to the plane of the
moving platform - degrees
In the above example angle monitoring is switched ON
for ALL actuators. In this illustration the angle between an actuator and the base of the
platform (bottom) should not be less than 10 deg, nor less than 5
deg between an actuator and moving plane of the platform (top).
If monitoring is required only for some actuators
then individual bits in parameter Monitor_Acts can be set. Limiting
angles can be set for individual actuators
Once enabled the actuator angle monitoring is
automatic and is calculated for each cue output set.
The actuator angle data can be displayed using the
Angles button. The display window will also indicate when an
actuator has breached its angle limits.
Once an angle limit breach recovers and the actuator
cues concerned move back into permitted working range the software
will attempt to smoothly restore normal cue movement by limiting the
speed of movement for a period of 2 seconds following breach
The motion cues can change rapidly in a simulation
and the particular combination of cues that caused an angle limit
breach may not be the same as the combination that exists when the
angle breach recovers. This can lead to a slight kick in the cue
output as the software attempts to reintroduce the live cues
following an angle breach.
Determining Angle Settings:
Appropriate angle limit settings can be determined
using the Angles display window and the Manual_Override
sliders. For this to work the By DOF checkbox MUST be ticked
- the angle monitoring does not work when the actuator positions are
overridden using the By Act setting.
Using the Manual_Override sliders in By DOF
mode the platform can be moved in each DOF, or with combinations of
DOF's to carefully force the actuators towards clash conditions. The
actuator top and bottom angles can be observed and appropriate
limits can then be set in the .bff file to limit movement.
NOTE: the actuator angles are calculated on the
underlying motion cues BEFORE Hold/Drive positions are enforced - so
you will not see the angles change as the platform moves into or out
of Hold position. You may also see the angles change whilst limiting
is active and is being applied to the output cues.