4 Replies Latest reply on Feb 12, 2018 5:00 AM by Intel Corporation

    Optical flow thermal issue

    DanMadill

      Hello,

       

      I am observing distortion in the optical flow camera when running the Poky Aero 1.6.1 O/S (BIOS 01.00.13). I had shown pictures of the distortion in a previous post.Optical flow camera distortion. At the time, we drew the conclusion that it was due to connector fatigue. However, we have done further research and the problem is definitely not connector fatigue. We plugged in a brand new camera and saw the same distortion even though the camera had only been plugged in once. That rules out connector fatigue.

       

      We also used proper ESD mats and ESD wrist straps at all times. However, to test the effect of ESD, we took a working camera and zapped the camera directly with ESD (the jolt was strong enough to jump 1 cm and was visible). After multiple zaps the camera was still working with no distortion. Hence, the camera does not appear to be very ESD sensitive, which makes us inclined to think that ESD is not the issue.

       

      Then we took the camera with distortion and tried to cool it with a fan. The distortion reduced a little, but did not disappear. If we heat the camera, the distortion definitely gets worse. When we put our entire drone in the freezer with a flashlight and stream the video to our PC, the distortion decreases until it disappears entirely. Hence, the distortion is definitely thermal related, even though the camera is never hot to the touch.

       

      All of these tests were done with the Poky Aero 1.6.1 O/S. Not all cameras show distortion but we have seen the issue with multiple cameras now.

       

      We then took the drone with the brand new camera that had distortion and downgraded the O/S to the Poky Aero 1.3.1 O/S. We did not change the hardware or camera connections at all. Running with the 1.3.1 O/S there was no distortion in the image, even over time.

       

      It seems to me that the internal frame rate set by the Poky Aero 1.6.1 O/S (which I believe is 75 Hz) is too high and some, but not all, cameras are overheating and produce distorted output due to thermal issues. The Poky Aero 1.3.1 O/S, I understand, uses a lower internal frame rate of 30 Hz for the optical flow camera and that does not appear to cause thermal problems.

       

      Is it possible to make this setting configurable or reduce the rate used in Poky Aero 1.6.1? We do not want to downgrade to the earlier O/S because of the improvements to 1.6.1, but we need the optical flow to work reliably, even if we have to work with a reduced frame rate.

       

      Best regards,

      Dan

        • 1. Re: Optical flow thermal issue
          Jeffrey95

          DanMadill I am also running the Poky Aero 1.6.1 and observing the same distortion when streaming the downward facing camera to QGroundControl. Additionally when running "aero-optical-flow", there are many errors "FPS below minimum" – are you also getting this error?

          • 2. Re: Optical flow thermal issue
            DanMadill

            The output I get from aero-optical-flow does not show those errors. I get:

             

            root@dan-aero1:~# aero-optical-flow

            Parameters:

                    camera_device=/dev/v4l/by-path/pci-0000:00:03.0-video-index2

                    camera_id=1

                    camera_width=320

                    camera_height=240

                    crop_width=128

                    crop_height=128

                    flow_output_rate=15

                    mavlink_tcp_ip=127.0.0.1

                    mavlink_tcp_port=5760

                    focal_length_x=216.667694

                    focal_length_y=216.245697

            [Debug] Initial exposure 850

            [Debug] Initial gain 0

            [Debug] Mavlink TCP initialized 127.0.0.1:5760

            [Debug] Mavlink stream HIGHRES_IMU set to 250.0 Hz

            Number of good matches: 20, desired: 20

            Number of good matches: 11, desired: 1

            Number of good matches: 14, desired: 11

            Number of good matches: 6, desired: 2

            Number of good matches: 5, desired: 1

            [Debug] No new gyroscope data available

            Number of good matches: 5, desired: 1

            ...

             

            Regards,

            Dan

            • 3. Re: Optical flow thermal issue
              Jeffrey95

              Interesting. My output shows that the "number of good matches" is less than the "desired." Perhaps this is being caused by my the low frame rate...

              • 4. Re: Optical flow thermal issue
                Intel Corporation
                This message was posted on behalf of Intel Corporation

                Hello Dan,

                Thank you for your interest in our Intel products.
                Your request has been received and is currently being investigated. 
                We will get back to you as soon as possible.

                Regards,
                Octavian