El mié, 19-09-2007 a las 09:23 -0500, Ray Henry escribió: > Are there more than one possible solution to the kinematics equations > you are using here. I remember years ago when K&T showed a Hexapod at > IMTS. Every so often the control would pick the wrong solution and rip > the ballscrew out of a nut. > > I know that the NIST Hexapod software picked the solution closest to > current position. > > Rayh
Yes you are right, kinematics has 2 solutions, the one shown in the photograph http://www.imac.unavarra.es/parallel/images/argazkiak/pimg_4416.jpg and another one that will put the head and arms facing upwards. For us inverse kinematics is analitical, and we can choose the downwards facing solution without problem. In the case of forward kinematics it can be the case that the system reaches such a meaningless solution. Nevertheless I think i not our case: When into to the emc interface, joints and pos gets initializated to 0,0,0,0,0,0, and we have ajusted our kinematics for it to be a solution, so as newton raphson iteration converges to the closest solution, and provides that while the systems moves previous solution is close to the next one, is almost imposible to have such a problem. We have not see right now. Nevertheless, your comments have made me to think that for security reasons it would be interestin to put a couple of "if" cluses that check twice that the computed position is a downward facing one. This will put another layer of security, over the security provided by the limit switches. Yesterday afternoon we moved the real machine, using the new kinematics, it moved almost right, despite rotations where made in the oposite direction. I think there is a litle problem joint numbering and conections. More on this, and I expect a video also in our next mail. Thanks to all for your incredible help :)) Javier and Aitor ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
