Lidar rotation speed reading = 0

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Lidar rotation speed reading = 0

Postby Delzur » July 6th, 2019, 6:02 am

Hi there,

New to the forum but I greatly appreciate all the resources I've found here!

My robot has been complaining about vision blocked for a year and I recently decided to try and repair it.
My Lidar was spinning but people suggested it might be spinning at an incorrect speed, so I replaced it.

Since it didn't fix the issue, I've now hooked the Robot to the computer and started using NeatoControl.

The scan tab does not show anything for me, so I tried manual commands:
  1. TestMode On
  2. SetLDSRotation ON
  3. GetLDSScan

Here are the results:

GetLDSScan
AngleInDegrees,DistInMM,Intensity,ErrorCodeHEX
0,0,0,0
1,0,0,0
2,0,0,0
[...]
358,0,0,0
359,0,0,0
ROTATION_SPEED,0.00


However, I do see the Lidar spinning! (Although at an inconsistent speed).
  • How is this possible?
  • Could it be because the Lidar spins in the wrong direction due to a mistake with the polarity, which would be giving a negative rotation speed interpreted as 0? My Lidar spins clockwise
  • Someone in the forum talked about the rubber "slipping". Would that be the issue I'm facing, and the Neato outputs 0 because the speed isn't consistent?
Delzur
 
Posts: 3
Joined: July 6th, 2019, 5:48 am

Re: Lidar rotation speed reading = 0

Postby glnc222 » July 6th, 2019, 9:04 pm

Normally with replacement motors the wires must be reversed from the original color coding on the factory motor. It is easy enough to test it both ways and see if that makes any difference in the result. Also, you can see the USB data in the Neato Control program with a graphical interface besides using the text interface through a terminal emulator program.
There are two sensors of the rotation I think, a tachometer on the motor and an optical position sensor for registering the start position of each rotation. Timing can then determine the direction of the laser.
glnc222
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Re: Lidar rotation speed reading = 0

Postby Delzur » July 7th, 2019, 2:17 pm

Hi and thanks for the answer.

I just changed the wires and while I was going to answer that it changed nothing except the rotation direction, it finally worked. Looks like now the polarity is good (counter-clockwise! At least for my botvac 85), but it had some trouble starting up at the good speed. I'm not sure if it was due to something that was rubbing or the rubber itself being loose. I'll try to use the robot and see if I can determine what's the cause for this (or if it happens at all).

I'm quite surprised about the polarity stuff as my replacement part already contained an extension chord that reversed the wires. I thought it was specifically to correct the polarity, it seems it was actually messing it up!

Thank you again for the answer, I'll keep the post updated :)
Delzur
 
Posts: 3
Joined: July 6th, 2019, 5:48 am

Re: Lidar rotation speed reading = 0

Postby glnc222 » July 7th, 2019, 6:20 pm

Counter-clockwise is the correct spin direction for the Neato lidar. There is some puzzle how the system can tell which direction it is moving, why it should make any difference to the software as opposed to simply erroneous travel guidance. Perhaps it is from triangulation from different positions on the floor, which relate lidar observations with data from the wheels for travel, messed up if the lidar aim direction is wrong, inconsistent motion sensed.
glnc222
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Re: Lidar rotation speed reading = 0

Postby Delzur » July 14th, 2019, 4:29 am

Alright, after reassembling it and trying to make it clean a room, it worked, then blocked himself on something, and I couldn't get it running after, it complained about vision blocked, again.

I'm now thinking about changing the o-ring for my Neato 85 to see if it helps. Any good place where I can order that for a delivery to Europe?
Delzur
 
Posts: 3
Joined: July 6th, 2019, 5:48 am

Re: Lidar rotation speed reading = 0

Postby glnc222 » Today, 9:37 am

The Mods & Repairs list top of forum lists lidar O-rings at thread
http://www.robotreviews.com/chat/viewtopic.php?f=20&t=19453
Ebay has many listings for specific Neato O-ring belts, and might have some from China for European delivery; check the international shipping in most listings there as well. AliExpress has many O-rings but hard to find the size.
glnc222
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Posts: 4963
Joined: January 23rd, 2012, 9:19 pm
Location: North Carolina, U.S.


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