> On Dec 5, 2024, at 2:48 AM, gene heskett <ghesk...@shentel.net> wrote: > > > They stand up to investigation. No ticklish servo tuning, they simply do as > they are told. The motor has its own encoder that's wired only to the driver. > The error determines the motor currant and that allows them to run lots > cooler. At the same time, if the error goes up, the driver will hit them with > every amp the psu has, skipped steps are history in that they don't happen. > Cost over regular steppers ranges between $40 and $80 per axis. They Just > Work.
This is how the motion control world is evolving — lower level control is migrating closer to the motors. I think one reason is to make the control loop faster. I don’t know about your motors but 10KHz PID loops are not uncommon. They might be running close to that. The link below shows some tiny 2-phase steppers being controlled as if they were analog BLDC motors. I think this is how you closed loop motors work and then they wrap a step/dir interface around it. I don’t know but I think the closed loop “steppers” are not even being stepped. Today we can drive the 4-wire stepper as if it were a BLCD motor and use FOC (field-oriented control) By using analog voltages (PWM) on the leads we have very fine control of the magnetic field orientation and se can smoothly rotate the field. I think this is what those closed-loop steppers are doing, they are not stepping but rather rotating to the next commanded step. You could find out if you could put an scope on the power leads and record a half second of waveform. Here is a demo video of an FOC interfaced NEMA stepper. These are the common $11 motors you see in 3D printers but it is not being stepped it shows what can be done for cheap today. The plastic wheels are pressure fit direct the motor shaft. The entire little machine cost about $50. I’ve linked the best part of the video but you can rewind and even see the C++ code on screen I know you might not care about little demo robots, but this shows that these cheap ’steppers” are capable of much better performance than we think. https://youtu.be/f9GJqqUpL2w?t=817 Arduino BLDC balancer robot - Tutorial youtu.be > > Stay warm and well. > > Cheers, Gene Heskett, CET. > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author, 1940) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
