I got a question concerning the accuracy of the "angular measurement" of the Hokuyo UTM-30LX-EW. There are fixed angular steps of 0.25 degree, but how accurate does the sensor reproduce the angular position of the previous revolution? I'm trying to find out how accurate the coordinates are. An empirical accuracy for the distances can be ascertained by measuring serveral times, but how about the angles?
Thank you very much!
Sincerely
Erik Edmund
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It is a quite challenging task to measure the angular accuracy. We use a rotary encoder disk to keep the angular steps at 0.25 degree. There is 10% error margin due to manufacturing. If you want to get as precise as possible, It is preferable to use a high speed infrared camera and measure the distance between spots. However, it is a costly method. May be there are other methods I am not aware of.
Regards,
Kristou
Last edit: Mehrez Kristou 2014-08-26
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Anonymous
Anonymous
-
2014-08-26
Hello Kristou,
thanks for your swift reply! The Hokuyo doesn't have a rotary encoder disk as far as I know. You have to generate the angles or angular steps synthetic by defining a starting direction with angle 0 degree. So your rotary encoder disk must be an additional component linked to the Hokuyo in a specific way? Do you measure the angle when the Hokuyo sends a signal into the object space?
In addition to it you said "we use", may I ask for what company you are working for? Is it the HOKUYO AUTOMATIC CO.,LTD.?
Thank you very much!
Regards,
Erik
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All our laser range finders use a rotary encoder disk. We don't need to measure the angle as it is already predefined with the encoder disk.
I should have added my signature.
Regards,
Kristou
＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
Dr. Eng. Kristou Mehrez
Hokuyo Aut. Co.,Ltd.
System Development Team
＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
Last edit: Mehrez Kristou 2014-08-26
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Anonymous
Anonymous
-
2014-08-26
Hello Kristou,
in this case a further question arises. Do you trigger the distance acquisition with the rotating encoder disk or is the distance measurement time-oriented by the internal clock and the rotating encoder disk controls the speed of the motor/mirror?
How accurate is the time synchronisation between angle and distance because uncertainties of the time synchronisation can be interpreted as angle error which has to be added to the error of 10 % due to manufacturing as mentioned. Is there a jitter?
Besides, I want to ask if the metric accuracies in the data sheet refer to the accuracy of the distance measurement or final 2D object points?
Thank you very much!
Regards, Erik
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Anonymous
Anonymous
-
2014-09-06
Hi Kristou,
this article helped me a lot, thank you very much! Unfortunately I got another question. Can you tell me you big the angular widening is, meaning how big the elliptical laser spot will become in certain distances?
Regards,
Erik
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Good evening,
I got a question concerning the accuracy of the "angular measurement" of the Hokuyo UTM-30LX-EW. There are fixed angular steps of 0.25 degree, but how accurate does the sensor reproduce the angular position of the previous revolution? I'm trying to find out how accurate the coordinates are. An empirical accuracy for the distances can be ascertained by measuring serveral times, but how about the angles?
Thank you very much!
Sincerely
Erik Edmund
Hi Erik,
It is a quite challenging task to measure the angular accuracy. We use a rotary encoder disk to keep the angular steps at 0.25 degree. There is 10% error margin due to manufacturing. If you want to get as precise as possible, It is preferable to use a high speed infrared camera and measure the distance between spots. However, it is a costly method. May be there are other methods I am not aware of.
Regards,
Kristou
Last edit: Mehrez Kristou 2014-08-26
Hello Kristou,
thanks for your swift reply! The Hokuyo doesn't have a rotary encoder disk as far as I know. You have to generate the angles or angular steps synthetic by defining a starting direction with angle 0 degree. So your rotary encoder disk must be an additional component linked to the Hokuyo in a specific way? Do you measure the angle when the Hokuyo sends a signal into the object space?
In addition to it you said "we use", may I ask for what company you are working for? Is it the HOKUYO AUTOMATIC CO.,LTD.?
Thank you very much!
Regards,
Erik
Hi Erik,
All our laser range finders use a rotary encoder disk. We don't need to measure the angle as it is already predefined with the encoder disk.
I should have added my signature.
Regards,
Kristou
＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
Dr. Eng. Kristou Mehrez
Hokuyo Aut. Co.,Ltd.
System Development Team
＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
Last edit: Mehrez Kristou 2014-08-26
Hello Kristou,
in this case a further question arises. Do you trigger the distance acquisition with the rotating encoder disk or is the distance measurement time-oriented by the internal clock and the rotating encoder disk controls the speed of the motor/mirror?
How accurate is the time synchronisation between angle and distance because uncertainties of the time synchronisation can be interpreted as angle error which has to be added to the error of 10 % due to manufacturing as mentioned. Is there a jitter?
Besides, I want to ask if the metric accuracies in the data sheet refer to the accuracy of the distance measurement or final 2D object points?
Thank you very much!
Regards, Erik
Hi Erik,
The encoder pulse gives the tempo, therefore, no jitter is expected.
Regards,
Kristou
Last edit: Mehrez Kristou 2014-08-26
Hi Erik,
I guess this article[1] may gives you some insight on how the sensor works.
[1] http://www.researchgate.net/profile/S_Yuta/publication/224623456_Development_of_ultra-small_lightweight_optical_range_sensor_system/links/02e7e51ea8f95aceba000000
Regards,
Kristou
Last edit: Mehrez Kristou 2014-08-26
Hi Kristou,
this article helped me a lot, thank you very much! Unfortunately I got another question. Can you tell me you big the angular widening is, meaning how big the elliptical laser spot will become in certain distances?
Regards,
Erik
Hi Erik,
Please contact me by mail.
Email: kristou (at) hokuyo (dash) aut (dot) jp
Regards,
Kristou