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juerg posted an update 6 years, 3 months ago
Currently on vacation in Japan (they have some nice robots here too but InMoov is not popular here).
I can’t draw you a picture with my mobile but look at this – the servo has to travel 17 plus 27 mm for complete opening and closing. Depending on the servo you have installed (my mg995 can do about 210 degrees) this will be probably 60 percent of the 0 to 180 degrees the MRL will work with. Not Shure but assume finger open is 0 degrees and closed is 180 degrees. By using the map function you can make the 0-180 move travel the total distance of 17 plus 27 mm. Because your pulley is set a bit sideways in 90 degrees it will move 17 mm to the left and 27 mm to the right when requesting 0-180 degrees.
Hi Juerg. I appreciate that you want to help. But from your answer, it is obvious that you don’t understand the basic problem. It has nothing to do with centering the servo. The servo needs to pull 27mm on one side to close the finger, while releasing 17mm on the opposite side. That is a difference of 10mm. Not a sum of 27 and 17. To open it again it needs to pull 17mm on one side, while releasing 27mm on the other side. With a single track, that is not possible. A single track pulley will pull 27mm on one side while releasing 27mm on the other side. That is nothing that can be solved with setting the servo offset, centering the pulley or remapping in MRL. It took me long time to understand that problem. It is not obvious. But it exists. Gaël has solved the problem by using springs in the arm. When you get back home , please build, test and measure. I hope that you have a nice vacation in Japan. They have some really nice robots.
I think I got your point. When doing my first pulleys I had problems that they interfered with the cover, adding a second track would require lower built servos or a modified servo-bed? And the string-guiders will need to be adjusted?