QPPS units vs Encoder Speed vs Events vs Cycles
Posted: Sun Feb 03, 2019 2:13 pm
Hi
I hope someone can help as I am rather confused over terminology.
I have 2 servocity motors whose encoder specs are as follows:
Encoder Cycles Per Revolution (Encoder Shaft) 7 (Rises of Ch A)
Encoder Cycles Per Revolution (Output Shaft) 374.325 (Rises of Ch A)
Encoder Countable Events Per Revolution (Encoder Shaft) 28 (Rises & Falls of Ch A & B)
Encoder Countable Events Per Revolution (Output Shaft) 1,497.325 (Rises & Falls of Ch A & B)
https://www.gobilda.com/5201-series-53- ... w-encoder/
I am also using roboclaw_ros, which wants the following information:
Should the QPPS figure from the motion control program be divided by 4 in the above calculation? I note that when rotating a motor by hand, I get about +1497 on the position, so I assume that uses "countable events". Is this true for the QPPS / speed too or does it use Cycles Per Revolution?
Secondly, what does the author of roboclaw_ros mean when s/he says "ticks"?
The use of three sets of terms terms between servocity, roboclaw and the ros node author has me quite stumped. Please can someone explain?
I hope someone can help as I am rather confused over terminology.
I have 2 servocity motors whose encoder specs are as follows:
Encoder Cycles Per Revolution (Encoder Shaft) 7 (Rises of Ch A)
Encoder Cycles Per Revolution (Output Shaft) 374.325 (Rises of Ch A)
Encoder Countable Events Per Revolution (Encoder Shaft) 28 (Rises & Falls of Ch A & B)
Encoder Countable Events Per Revolution (Output Shaft) 1,497.325 (Rises & Falls of Ch A & B)
https://www.gobilda.com/5201-series-53- ... w-encoder/
I am also using roboclaw_ros, which wants the following information:
Countable Events per Revolution is 4 times Encoder cycles per revolution, which is fine. However I am not able to find information explaining if the encoder speed in QPPS is the countable events, or the cycles per revolution. I need this to find the maximum speed in meters per second, and assumed I need to use the 374.325 figure (cycles), then use that to find degrees per pulse, then use v = omega * r to find tangential speed having found the pulses per second. Of course this will be wrong by a factor of 4 if I am using the wrong item - countable events or cycles per revolution. Other internet sources tell me that cycles are the same as pulses.max_speed Max speed allowed for motors in meters per second
ticks_per_meter The number of encoder ticks per meter of movement
Should the QPPS figure from the motion control program be divided by 4 in the above calculation? I note that when rotating a motor by hand, I get about +1497 on the position, so I assume that uses "countable events". Is this true for the QPPS / speed too or does it use Cycles Per Revolution?
Secondly, what does the author of roboclaw_ros mean when s/he says "ticks"?
The use of three sets of terms terms between servocity, roboclaw and the ros node author has me quite stumped. Please can someone explain?