Resolve EPOS "UnderFlow Error"

hmartiro / project-thesis

xJüs, the hexapodal robot with a passive-backbone to improve behavior over harsh terrain.

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Resolve EPOS "UnderFlow Error" #52

Closed PayneTrain closed 11 years ago

PayneTrain commented 11 years ago

Contacted Patel, no solution found yet.

PayneTrain commented 11 years ago

50 ms time sample with following error set at 30,000 causes no problems after two days of testing. Perhaps underflow error was caused by right leg always having a low (2000) default following error -> leg stops because of error -> no more pvt values are fed and thus the buffer 'starves' <-- this is just a theory, not sure if its the case
Still need to understand why having smaller time stamps reduces the rate at which the interpolation sends points as it seems the cubic interpolation should send every 1ms regardless and only quality of the function should be affected by the sampling

hmartiro commented 11 years ago

Just found these two parameters in the object dictionary:

0x60C2 0x01 - Interpolation Time Period Value 0x60C2 0x02 - Interpolation Time Index

According to the help, the time step of the interpolation is given by Time Period Value * 10^(Time Index). Currently, Time Period Value = 1 and Time Index = -3, which explains the 1ms time we are seeing. We can try to change this to something higher to see if if the error disappears for all PVT trajectories we give it.

Also there is an entry for 'Interpolation Sub Mode Selection' which is set to Cubic Spline, but there are no other options currently.

hmartiro commented 11 years ago

Btw i did get the error a couple of times while testing with 50ms and 30k following error, but it is very rare.

hmartiro commented 11 years ago

not a problem over the API, so solved