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| Control System Overview: |
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| The
Profile Group System |
| The three profiles, force
positive damping and negative damping, are grouped together along with
a load of other widgets into what I have called a profile group.
This is a configuration or software object that captures a whole suite
of properties that describe the behaviour of the actuator, including
things like how it communicates with the outside world. The actuator can then be given several of these profile groups at once, each of which can then become active depending on certain conditions. In this way it is possible to give an actuator several completly different spring damping systems to emulate and control how and when it switches from one to the other. Exactly how and when this happens can be determined by a number of factors, all user configurable. |
| Thresholds |
| Each profile group has a set of
threshold checking modules. These can be assigned a particular
system variable, for example the actuators output angle, and they then
check this against a user defined positive and negative value. If
the variable goes over the positive value (threshold) then an internal
variable is activated (a flag is set to 1) and if it goes below the
negative value the negative flag is set to 1. There are (currently) four of these threshold checkers and they can measure ANY variable in the control system, for example the angular velocity, a serial control value, an analogue input. You can also specify a fixed value for the positive and negative thresholds OR you can source them from ANY other system variable, again this can be the angle or angular velocity or an analogue input. The image below shows the configuration utility being used to set a negative threshold on the angle. When you do this the thresholds appear on the profile editing image as shown. |
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| Setting
thresholds: The threshold checker has been set to check the
angle. Only the negative (less than) part is being used. If
the angle drops below this value (indicated by the green line) the flag
will be set to true. |
| Profile Switching |
| In order to get the actuator to
switch between different profile groups each group has its own
switching module. This has a series of inputs that are worked
through in order. Each input can be configured to evaluate a
flag, for example a threshold activated flag, and if the flag is true
it will jump to whatever profile group you have selected (or pick one
at random if you want). This image illustrates the configuration utility setting the profile checker to evaluate the negative threshold flag and switch to profile group 2 if it is true. |
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| Profile
Group Switcher: Each condition is evaluated in turn, if condition 1 is
true then it switches to the profile you have selected, otherwise it
will go on to the next condition. If no conditions are true then
it will discard it and continue with the current profile group. |
| What can this do? |
| You can use this to create a
latch or anything else with hysteresis. The image below shows how
two profile groups have been configured to work together as a
latch. The first has a spring and threshold set up so the output
will move away from the threshold. The second is identical but a
mirror image. When the threshold in each is passed (by forcing
the output in that direction) the actuator will jump to the other
profile. The result is a latch, a video of which is below the
image. |
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| Simple
Latch: The actuator swaps between the profiles when their
thresholds are passed and the force profile in each will try and push
the output away from the threshold. The black arrows show how the
actuator will jump from one profile group to the other when the
threshold is passed. |
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