Pidog V1 / RPi 3B+ - dog's head vibrates from side to side

Robotic kit for Raspberry Pi
1

I’ve noticed that after I’ve run any of the Python programs in the “examples” folder, my pidog’s head starts vibrating rapidly from side to side by a small amount, and this continues even after the Python program is ended with Ctrl-C. I’ve run 0_calibration.py and centralised all the motors (eg 90 degree angle at “knees”, lower legs horizontal, head centralised for yaw/pitch/roll), and saved those config values.

I’ve checked that all the plugs on the motor wires are properly connected - correct polarity and pushed fully onto header pins on HAT.

If I push on the dog’s head slightly, the vibration stops. One thing I have noticed is that if I yaw the head using 2_function_demonstration.py, the movement seems to judder slightly as the head passes through the straight-ahead position, although it moves smoothly when it is turned away from pointing forwards.

With the power off, I can turn the head manually through the full range of movement (about +/- 60 degrees) without any feeling of mechanical resistance at any point in the rotation.

Any suggestions?

2

I have the same issue. Did you ever ‘cure’ your dogs fuzzy head?

3

The servo might be broken. Please record a video and send it to our after-sales service email at service@sunfounder.com. If the file size is large, you can upload it to Google Drive and share the link.

4

I have taken a couple of videos and photos which I will send to service @ sunfounder . com. I’m posting them here as well in case anyone else has the same symptoms, because I have discovered something which may help in diagnosing the problem.

This video https://drive.google.com/file/d/16IcWMrC_OYEXSqLUlgXlXNOJA1Tq3B4e/view?usp=sharing shows the PiDog, immediately after booting, running examples/1_wake_up.py. The head is seen to start vibrating (the P4-connector Yaw axis). I lightly gripped the sides of the head and the vibration stopped, but as soon as I touched the bundle of cables, vibration started again.

The vibration loosened one of the screws which was holding the yaw servo in place, so I had to disassemble the head to refit and re-tighten the screw. While the head was disassembled, I discovered a situation which reliably causes vibration and one which reliably cures it. This may be important diagnostic information!

I disassembled the head by removing the four rivets and two screws from the “cheek” plate on the right, and the four rivets (but not the screws) from the left “cheek”. This allows the “head” to be removed: the plate containing the camera, ultrasound detector and the touch plate.

With the head plate removed, there is no vibration. As soon as I attach it by even a single rivet to the cheek plate which is attached to the yaw servo, vibration begins. Does this suggest that the added mass of the head plate is causing the total mass connected to the servo to reach some resonant conditiion?

https://drive.google.com/file/d/18kt9xhxa-QMeylKV87cj5kj9am2QcwdO/view?usp=sharing is the view of the head and the left cheek, with the front of the head hooked over to hold it roughly in the correct orientation but with no rivets to the cheek. The cheek is fastened to the yaw servo by two screws.

The other (right) cheek plate is completely removed (four rivets and two screws removed) - I’d attach a photo but I’ve reached the limit of two links to this positing.

Even with the head hooked over the left cheek, as in the photos, there is no vibration, but as soon as I connect the head to the left cheek even by one rivet, vibration begins. Is that significant?

5

MrSteve, does my video show the same vibration that you have seen?

6

Regarding the issue of the head servo shaking, it is likely caused by play in the servo. We can send you three new version servos to replace the head servo and see if this resolves the shaking issue.Please contact our after-sales service at service@sunfounder.com to provide your detailed address.