BetegustafParticipantJune 6, 2019 at 11:14 amPost count: 16
Now that I’ve worked quite a lot on my Niryo pushing it to its limits in terms of precision, I’ve got some questions about Dynamixel motors:
-Why do they have a really great precision but a huge gap so that i can clearly move them by my hand, this could lead to big precision errors depending of the orientation of the eef tool and the inertia (when there is a highly negative or positive accelerations). By my hand i can move the eef more than 5mm away of its position just by touching it
-I observed that when lifting my tool (215gr) the arm is falling by 5mm between (x0.27 y0.0 z0.01) and (x0.36 y0.0 z0.01) Do you observed that already or can confirm the problem ?
-I observed that my axis 5 was heating a lot compared to other motors (>60°C) and I think this is because of my specific tool that weights 215gr (under 0.5kg that is maximum niryo payload) and its inertial center is situated 7cm away of the axis 5, I checked the documentation of XL430 and its looks OK (1.4Nm at 11.1V), I removed a part of my tool so it weights 119gr and the motor have found usual temperatures back.
Have you made some parameters about torque limit (percentage of Max Torque) ? (I’ve found some code in the catkin folder but I don’t understand what you made)Edouard RenardKeymasterJune 10, 2019 at 5:34 pmPost count: 239
Thanks for this feedback.
The issues you talk about are things that we also noticed. Those Dynamixel motors are great motors for their price, however they’re certainly not enough to achieve a very robust system.
There are also many other factors that can influence the robustness and precision of the robot: 3D printing elasticity, belts, motors, etc. If you add all the small stuff, the overall precision can become much lower. And that’s why we say this robot is only an educational robot, that can reproduce industrial use cases, but not actually do them. Note, however, that the repeatability is quite good on the robot.
The rise in temperature for your axis 5 (XL-430) is maybe not normal. Can you check your power adapter that we provided with the robot? For some early versions we provided a 12V power adapter, which was too much and sometimes can lead to burn the XL-430 motors. Now we ship 11.1V adapters. If you have the wrong one, please don’t use the robot too much and contact our technical support so we can ship you a new one asap!
We have not changed any parameter on the Dynamixel motors we use. However you can (at your own risks) change them using this script on the robot, and following the Dynamixel documentation for registers (available on the link above)BetegustafParticipantJune 11, 2019 at 2:12 pmPost count: 16
Thanks a lot for your reply, then I think I can’t do that much on that side to improve robot precision, I have to agree that I was impressed by the repeatability compared to the precision take a look at what I have printed with the Niryo, I had a problem with my extrusion but the walls are pretty good:
Concerning my axis 5 heat I have the 11.1V adapter and the voltage or motion both looks good so it might be something else that I didnt find yet.. I don’t have enough informations right now to determine what is the cause, I will update it later..
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