Hello,
In the referred thread, there was a reference to "Timestamp based velocity
estimation"
<quote>
Timestamp based velocity estimation improves this quite a bit (the software
encoder, Mesa and Pico systems encoders all have this feature) But the
timestamp velocity estimation signal/noise is limited by quadrature error
(inexact 90 degree quadrature) I see a very roughly 2x to 10x improvement
in
the velocity signal depending on encoder and speed using the timestamp. I'm
not sure where the crossover is where higher resolution is better than the
timestamp system but I suspect a 1 million count encoder is going to beat
the
timestamp system by a wide margin.
</quote>
I'm curious about the concept.
Could you please elaborate a bit or refer to some bibliography?.
I suppose that you are able to infer, within a realtime hal module, the
elapsed time between the actual invocation
and the previous one, and that that gives a real estimation of the thread
period, in comparison with the theoretical
value given in the ini file. Then you estimate the velocity as usual:
(new_pos - prev_pos) / (better_estimation_of_thread_period)
I supose that the parameters time and tmax of a function in a thread, for
example
pid.0.do-pid-calcs.time
pid.0.do-pid-calcs.tmax
are related to the implementation of such an algorithm.
But I can not find definitions for their meaning in the documentation.
How can I access these variables within a HAL module.
The only aparently related parameter I'm finding is period (and fperiod).
<quote>
6.4 Parameters
Comp’s are passed the "period" parameter which is the time in nanoseconds of
the last period to
execute the comp. This can be useful in comps that need the timing
information.
</quote>
<quote>
FUNCTION(name) Use this macro to begin the definition of a realtime function
which was previously
declared with "function NAME". The function includes a parameter "period"
which is
the integer number of nanoseconds between calls to the function.
</quote>
<quote>
fperiod The floating-point number of seconds between calls to this realtime
function
</quote>
What is the most appropriate way to find the elapsed time between calls of a
given function in a thread.
I'm presuming that the definitions are:
fperiod is a floating point representation of period so
fperiod=period * 1.0e-9
period = time - prev_call_time
tmax=max(time, prev_call_time, prev_prev_call_time,...)
Finally,
Can I access the intended period of a thread, that is the one that is
specified when creating it?.
Thank you,
Javier
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