There may be times when the max capabilities of an actuator may cause problems, such as a system that isn't particularly stiff. In these situations reducing the max accel to reduce jerk can improve performance. Also be sure to allow for headroom for maximum anticipated load.
----- Original Message ----- From: "Jerry Scharf" <[email protected]> To: "Enhanced Machine Controller (EMC)" <[email protected]> Sent: Thursday, August 27, 2015 2:35:04 PM Subject: Re: [Emc-users] computing max acceleration for an actuator Hi, One last question about this. Is there any harm in reducing the max acceleration below what the actuator is capable of? I wouldn't seem like it, but I want to be sure. I know it will slow things down a bit, but this is by far the fastest part of my system and only moving a short distance. jerry On Tue, Aug 25, 2015 at 5:04 PM, TJoseph Powderly <[email protected]> wrote: > Jerry I didnt answer your question. > to measure acceleration there's an industry standard 'step' test. > The 'step' is to apply the voltage required to achieve max velocity. > This voltage **instantly** rises from 0 to the value needed for max > velocity. > Thats where the name 'step' comes from, > Its a square edge on a scope. > > A second measurement is now needed, > Some way to determine _when_ the > maximum velocity is actually achieved. > > Old school dc motors gave us Tachos so this was easy. > I dont know what you can put together. > You could attach a voice coil to the end, I suppose. > Measure when the output voltage goes constant ( at max vel ) > A scope should show a 'knee' starting at 0Volts. > > But if you measure time from the 'step' until the max vel, > you have the precise acceleration _time_. > > The acceleration time divide by time is the acceleration > > ( example .240 Sec accel time to achieve 800mm/minute velocity > is .24 sec to achieve 13.333mm/sec > is 55.555 mm/s/s > > 3.15"/sec / 0.02ec = 157.5in/s/s ) > > HTH > TomP > tjtr33 > On 08/25/2015 04:09 PM, Jerry Scharf wrote: > > Hi, > > > > My quick scan of the docs didn't find an explanation for how to calculate > > this from manufacturer specs rather than experimentation. I want to make > > sure I am doing this right. > > > > The actuator is rated a 3.15 inches per second and it can reach full > speed > > in under .02s for the load I will be putting on it. If I use a = v/t, > this > > comes out to about 150 inches per second square. Does this look right? > > > > The actuator is a SMC LXPB2BD-50S that I picked up used. > > > > jerry > > > > > > ------------------------------------------------------------------------------ > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Jerry Scharf FINsix IT 650.285.6361 w 650.279.7017 m ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
