dear Nicklas, a given DC bus voltage for the drives is indeed *one* reason why the jerk *must* be limited, otherwise excessive tracking error occurs. But another reason for jerk control is to avoid machine vibration.
best regards, Raoul -----Message d'origine----- De : N <[email protected]> Envoyé : vendredi 22 novembre 2019 23:55 À : EMC developers <[email protected]> Objet : Re: [Emc-developers] announcement OpenCN, a new fork of LinuxCNC --> Jerk control According electric motor equations commonly available jerk is controlled by voltage and could be changed instantly which in practice is within one switching period while acceleration --> velocity --> position is integrated in some way from jerk. Velocity will for example add a back-emf changing which voltage is needed to get the jerk and limit how much jerk is available. Then is of course the question what is fast enough considered a jump which may add further smoothnes requirements. Not sure what G^2 blending is but have seen a few smoother curves in the 402 CANopen standard. Hysteresis will usually produce fast acceleration jumps though theoretical limit is available voltage. > dear Stevenson, > > LinuxCNC lacks jerk control and "G^2 blending". > Without jerk control, the tangential acceleration jumps, without G^2 > blending, the normal acceleration jumps. > Both lead to an excitation of machine vibrational modes ... leading to bad > surface quality. > > No problem for hobbyist applications, but big problem for high end commercial > applications. _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
