Re: [Emc-users] Variable axes acceleration
Il giorno lun, 19/09/2011 alle 23.02 +0300, Andrew ha scritto: Thinking about decreasing stepper (and servo, to some extent) torque at higher speeds, I just thought that having variable axis acceleration would be perfect. I.e., the highest at lower speeds and lower at higher speeds. Is that ever possible with EMC2? If no, is it hard to implement? Andrew I agree in some way, because EMC2 can be more flexible for every kind of use. One thing that i really find usefull can be, when programming g-codes, to have a letter (i know they are all used..) to control acceleration ratio. so that for every single movement i could set acceleration. and is at the programmer's knowledge to decide where it can be useful a rapid acceleration ratio, or a slow one. for example a pick and place flexible machine, if it picks heavy things, maybe will be good to slow down the accelerations. Personally i use EMC2 for 'artistic' purpose, i'll find very useful this possibility! again, you can imagine an exapod used for something similar to a car simulation, and you'll need variable accelerations. i think it will simply make EMC2 'more comlete'. thanks, dab. -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Variable axes acceleration
I thought I remembered a name for that from college physics. Velocity is meters/sec Acceleration is meters/sec^2 Jerk is meters/sec^3 Jerk is the rate of change of acceleration. http://en.wikipedia.org/wiki/Jerk_(physics) On Mon, Sep 19, 2011 at 3:02 PM, Andrew parallel.kinemat...@gmail.com wrote: Thinking about decreasing stepper (and servo, to some extent) torque at higher speeds, I just thought that having variable axis acceleration would be perfect. I.e., the highest at lower speeds and lower at higher speeds. Is that ever possible with EMC2? If no, is it hard to implement? Andrew -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Variable axes acceleration
On 19 September 2011 21:02, Andrew parallel.kinemat...@gmail.com wrote: Thinking about decreasing stepper (and servo, to some extent) torque at higher speeds, I just thought that having variable axis acceleration would be perfect. I.e., the highest at lower speeds and lower at higher speeds. Is that ever possible with EMC2? If no, is it hard to implement? Currently stepgen maxaccel is a parameter, not a pin, so it would need to be changed to a pin to make it possible to change it in real-time from HAL. However, that is only part of the story. I think that the max accell for the Trajectory Planner is read in once at load-time from the INI file. That would have to be turned into a HAL pin too (again, possible, but work) -- atp Torque wrenches are for the obedience of fools and the guidance of wise men -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Variable axes acceleration
I would think that this would be very hard to implement successfully. You are talking about optimizing the acceleration settings to a particular motor/drive/load setup. I can only see this being of a benefit if you were running a fixed part with the same cutter over and over again with a undersized or poorly sized drive system. If you changed materials or cutters or the carriage mass you might have to retune everything. The norm is to make sure that you are not operating your motors that close to the edge of their torque curve. A machine with accels tightly fitted to the motor/drive/load would be very unforgiving. Servos can operate beyond their ratings for short periods of time which sometimes makes them more forgiving, especially if you increase the the max following error allowed. Dave On 9/19/2011 4:02 PM, Andrew wrote: Thinking about decreasing stepper (and servo, to some extent) torque at higher speeds, I just thought that having variable axis acceleration would be perfect. I.e., the highest at lower speeds and lower at higher speeds. Is that ever possible with EMC2? If no, is it hard to implement? Andrew -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Variable axes acceleration
Although my education, long ago, was in physics, I do not really understand the physics of electric motors. Are there reasons to limit the rate of change of acceleration? for example: Are there reasons that one would not want to go from max acceleration in one direction to max acceleration is the opposite direction? If so under what circumstances? What kind of motors? Craig On 9/20/2011 6:56 AM, Dave wrote: I would think that this would be very hard to implement successfully. You are talking about optimizing the acceleration settings to a particular motor/drive/load setup. I can only see this being of a benefit if you were running a fixed part with the same cutter over and over again with a undersized or poorly sized drive system. If you changed materials or cutters or the carriage mass you might have to retune everything. The norm is to make sure that you are not operating your motors that close to the edge of their torque curve. A machine with accels tightly fitted to the motor/drive/load would be very unforgiving. Servos can operate beyond their ratings for short periods of time which sometimes makes them more forgiving, especially if you increase the the max following error allowed. Dave On 9/19/2011 4:02 PM, Andrew wrote: Thinking about decreasing stepper (and servo, to some extent) torque at higher speeds, I just thought that having variable axis acceleration would be perfect. I.e., the highest at lower speeds and lower at higher speeds. Is that ever possible with EMC2? If no, is it hard to implement? Andrew -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Variable axes acceleration
2011/9/20 Dave e...@dc9.tzo.com I would think that this would be very hard to implement successfully. You are talking about optimizing the acceleration settings to a particular motor/drive/load setup. I can only see this being of a benefit if you were running a fixed part with the same cutter over and over again with a undersized or poorly sized drive system. If you changed materials or cutters or the carriage mass you might have to retune everything. The main idea it to use motors at full capacity. Now maxaccel is limited by torque value at max speed, but it sometimes could be 2-3 times larger at low speeds, resulting in 1.5-2 times shorter acceleration distance. That would be especially noticeable at short moves. The norm is to make sure that you are not operating your motors that close to the edge of their torque curve. A machine with accels tightly fitted to the motor/drive/load would be very unforgiving. But at least we might balance the torque reserves at high and low speed. That is, use more capacity of motors, again. Servos can operate beyond their ratings for short periods of time which sometimes makes them more forgiving, especially if you increase the the max following error allowed. When I tune my servos with pncconf, I have stable alternate motion with 10 m/s2 up to 7 m/min speed, with 5 m/s2 up to 9-10 m/min etc. With higher values there's an overload and stop. It looks like lack of capacity at higher speed. Thus, if I want faster acceleration I should limit max speed, if want more speed I should completely suppress the acceleration. But with variable acceleration I could use almost all I have! 2011/9/20 andy pugh bodge...@gmail.com Currently stepgen maxaccel is a parameter, not a pin, so it would need to be changed to a pin to make it possible to change it in real-time from HAL. However, that is only part of the story. I think that the max accell for the Trajectory Planner is read in once at load-time from the INI file. That would have to be turned into a HAL pin too (again, possible, but work) Wouldn't it be easier to change main motion equation to take into account jerk (thanks Bryce), and add some new parameter to stepgen? Andrew -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Variable axes acceleration
On 20 September 2011 16:01, craig cr...@facework.com wrote: Although my education, long ago, was in physics, I do not really understand the physics of electric motors. Are there reasons to limit the rate of change of acceleration? Two different idea have been conflated here. Andrew was suggesting altering the motor max-acceleration as a function of motor speed to allow for the fact that steppers have less torque available to acceleration with the faster they are spinning. Bryce then brought in the subject of Jerk control, which is a different subject. To answer your question: as the acelleration changes sign, the reaction force on the machine frame changes direction. So the whole frame goes from being loaded to the left, to being loaded to the right, and will swing back-through the neutral position, and out the other side, then wobble back and forth for a while before settling to a new position. You can feel the same effect if you try standing on the Tube (or on a bus) as it comes to a halt. The acceleration as the train brakes to a halt instantaneously goes to zero as the speed hits zero. And all the passengers who are braced against the force stumble. You will find that when driving a car you unconciously feather off the braking as you come to a halt. That is manual (well, podial, I suppose) jerk control. -- atp Torque wrenches are for the obedience of fools and the guidance of wise men -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Variable axes acceleration
The rate of change of acceleration is Jerk.Limiting Jerk literally make the machine less Jerky which is much more noticeable when running at high speeds. Andy hinted at it with car braking..Have you ever been in a car with a new driver? Oftentimes everyone suffers from a bit of whiplash due to the new drivers lousy braking and lack of control of the accelerator pedal. That is jerk. A while back, someone on this list mentioned that they had tweaked EMC2 to include jerk limiting and I believe they included a URL to their modified source code, if that is of interest to anyone. That was probably 6 months ago or so. But like Andy said, Jerk limiting is much different than dynamically adjusting acceleration rates based on motor speed. Dave On 9/20/2011 11:01 AM, craig wrote: Although my education, long ago, was in physics, I do not really understand the physics of electric motors. Are there reasons to limit the rate of change of acceleration? for example: Are there reasons that one would not want to go from max acceleration in one direction to max acceleration is the opposite direction? If so under what circumstances? What kind of motors? Craig On 9/20/2011 6:56 AM, Dave wrote: I would think that this would be very hard to implement successfully. You are talking about optimizing the acceleration settings to a particular motor/drive/load setup. I can only see this being of a benefit if you were running a fixed part with the same cutter over and over again with a undersized or poorly sized drive system. If you changed materials or cutters or the carriage mass you might have to retune everything. The norm is to make sure that you are not operating your motors that close to the edge of their torque curve. A machine with accels tightly fitted to the motor/drive/load would be very unforgiving. Servos can operate beyond their ratings for short periods of time which sometimes makes them more forgiving, especially if you increase the the max following error allowed. Dave On 9/19/2011 4:02 PM, Andrew wrote: Thinking about decreasing stepper (and servo, to some extent) torque at higher speeds, I just thought that having variable axis acceleration would be perfect. I.e., the highest at lower speeds and lower at higher speeds. Is that ever possible with EMC2? If no, is it hard to implement? Andrew -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Variable axes acceleration
On 9/20/2011 11:34 AM, Andrew wrote: It looks like lack of capacity at higher speed. You may be simply running out of servo power. Servos oftentimes have some reserve power that you can use for a short period of time, but that is limited. If your drive power supply is undersized, that will also limit max servo power. I don't know what kind of overload your drive is indicating but sometimes you can adjust the current limits on servo drives and get more peak power out of them. The default settings are oftentimes quite conservative. Dave -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Variable axes acceleration
2011/9/20 Dave e...@dc9.tzo.com On 9/20/2011 11:34 AM, Andrew wrote: It looks like lack of capacity at higher speed. You may be simply running out of servo power I've thought about it already, thanks. That's what I intend to try - increase supply power. Servos oftentimes have some reserve power that you can use for a short period of time, but that is limited. If your drive power supply is undersized, that will also limit max servo power. I don't know what kind of overload your drive is indicating It just stops and shows something like Overvoltage when connected to PC. sometimes you can adjust the current limits on servo drives and get more peak power out of them. The default settings are oftentimes quite conservative. If I only knew how few settings those DMM servos have... Though, even now I think that at the moment it was the only option to purchase 6 identical cheap motors. Andrew -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Variable axes acceleration
On Tue, 20 Sep 2011, Andrew wrote: Date: Tue, 20 Sep 2011 19:38:08 +0300 From: Andrew parallel.kinemat...@gmail.com Reply-To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net Subject: Re: [Emc-users] Variable axes acceleration 2011/9/20 Dave e...@dc9.tzo.com On 9/20/2011 11:34 AM, Andrew wrote: It looks like lack of capacity at higher speed. You may be simply running out of servo power I've thought about it already, thanks. That's what I intend to try - increase supply power. Servos oftentimes have some reserve power that you can use for a short period of time, but that is limited. If your drive power supply is undersized, that will also limit max servo power. I don't know what kind of overload your drive is indicating It just stops and shows something like Overvoltage when connected to PC. Hmm, Overvoltage sounds like you have a problem during decelleration. Do your drives have a brake circuit? If so is it enabled (brake resistor installed and brake voltage set?) If this is due to regeneration during decceleration, any of these will help: 1. Get a brake circuit working (best) 2. Put a (much) larger output capacitor on your power supply 3. Lower your power supply voltage so you have more margin for voltage rise when deccelerating (this will limit your maximum velocity however) sometimes you can adjust the current limits on servo drives and get more peak power out of them. The default settings are oftentimes quite conservative. If I only knew how few settings those DMM servos have... Though, even now I think that at the moment it was the only option to purchase 6 identical cheap motors. Andrew -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your ()_() signature to help him gain world domination. -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Variable axes acceleration
- Original Message - From: Steve Stallings steve...@newsguy.com Accomodating a variable acceleration limit would seem to be fairly complex. Perhaps there is a solution that would offer some of the benefit without as much pain. Since rapid moves are done without cutting loads, perhaps we could have a separate set of acceleration and velocity limits that are used only for rapid moves. This would offer some improvement without a major rewrite of the trajectory planner. Regards, Steve Stallings On a related topic I have wondered if it would be possible to have a second set of following error settings for rapids. I feel in my tuning that I sacrifice rapid performance to avoid errors that really only need to be tight during cutting. John Prentice -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Variable axes acceleration
On Tue, 2011-09-20 at 19:38 +0300, Andrew wrote: ... snip It just stops and shows something like Overvoltage when connected to PC. ... snip I've seen this message from my VFD's while setting up dynamic braking where the motor back EMF from motor deceleration (motor becomes more like a generator) back drives the VFD's DC bus beyond the bus maximum voltage. Fitting an appropriate braking resistor or limiting the motor's deceleration usually fixes this. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Variable axes acceleration
On Sep 20, 2011, at 11:09 , John Prentice wrote: On a related topic I have wondered if it would be possible to have a second set of following error settings for rapids. I feel in my tuning that I sacrifice rapid performance to avoid errors that really only need to be tight during cutting. We have that already. Check out FERROR (following error allowed at high speeds) and MIN_FERROR (following error allowed at low speeds). These are described in section 2.10 of the Integrator Manual: http://www.linuxcnc.org/docs/2.5/html/config/ini_config.html -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Variable axes acceleration
craig wrote: Although my education, long ago, was in physics, I do not really understand the physics of electric motors. Are there reasons to limit the rate of change of acceleration? for example: Are there reasons that one would not want to go from max acceleration in one direction to max acceleration is the opposite direction? If so under what circumstances? What kind of motors? Really, the motor doesn't care all that much. It may be possible, however, to get somewhat more acceleration during most of the period of acceleration if the ends of the accel ramp are tapered. This might be more beneficial with stepper motors. That is the goal of schemes to reduce jerk, as well as to try to avoid exciting dynamic responses of the machine structure. There was an attempt to put S-curve acceleration into EMC, but it was apparently not successful. The methods of trajectory planning and smooth transitions from one arbitrary linear or arc move to the next linear or arc move get complicated if the acceleration is not constant. Jon -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Variable axes acceleration
On Tue, 2011-09-20 at 18:09 +0100, John Prentice wrote: ... snip On a related topic I have wondered if it would be possible to have a second set of following error settings for rapids. ... snip I think there is, in the .ini file: FERROR = 0.001 -- Normal error MIN_FERROR = 0.005 -- Low speed error From: http://www.linuxcnc.org/docview/html/config_ini_config.html ... MIN_FERROR = 0.010 This is the value in machine units by which the axis is permitted to deviate from commanded position at very low speeds. If MIN_FERROR is smaller than FERROR, the two produce a ramp of error trip points. You could think of this as a graph where one dimension is speed and the other is permitted following error. As speed increases the amount of following error also increases toward the FERROR value. FERROR = 1.0 FERROR is the maximum allowable following error, in machine units. If the difference between commanded and sensed position exceeds this amount, the controller disables servo calculations, sets all the outputs to 0.0, and disables the amplifiers. If MIN_FERROR is present in the .ini file, velocity-proportional following errors are used. Here, the maximum allowable following error is proportional to the speed, with FERROR applying to the rapid rate set by [TRAJ]MAX_VELOCITY, and proportionally smaller following errors for slower speeds. The maximum allowable following error will always be greater than MIN_FERROR. This prevents small following errors for stationary axes from inadvertently aborting motion. Small following errors will always be present due to vibration, etc. The following polarity values determine how inputs are interpreted and how outputs are applied. They can usually be set via trial-and-error since there are only two possibilities. The EMC2 Servo Axis Calibration utility program (in the AXIS interface menu Machine/Calibration and in TkEMC it is under Setting/Calibration) can be used to set these and more interactively and verify their results so that the proper values can be put in the INI file with a minimum of trouble. ... I don't really understand the above. I just play with the numbers until the machine seems to work -- not ideal on my part. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Variable axes acceleration
On Tuesday, September 20, 2011 03:45:13 PM craig did opine: Although my education, long ago, was in physics, I do not really understand the physics of electric motors. Are there reasons to limit the rate of change of acceleration? Every hear of E=MV2? The machine has a mass that must have its velocity changed when you accel or decel it, and the biggest (usually) piece of that mass, because of the 'gear' ratios involved, is the mass in the iron or steel in the motors armature + the mass of the (usually) direct driven screw and the couplings between them. for example: Are there reasons that one would not want to go from max acceleration in one direction to max acceleration is the opposite direction? If so under what circumstances? What kind of motors? A secondary effect when using steppers is that the base_period controls the percentage of the speed that changing the pulse speed by a multiple of the base_period, sounds infinitely variable at low speeds, but as you approach the high end of the range, that difference in the number of base_periods is a lot bigger speed step when the motor is doing 400 rpm than it is when it is doing 10 rpm. There must be sufficient power available for the motor to maintain synch with the steps AFTER it has moved the rest of the machine else its likely stalled very quickly. Stalls = wrecked parts sometimes broken tooling. Don't ask me how I know. :-) So the accel/decel must take place at a rate the motor can stay within a degree or less of synchronized. This can be boosted by higher voltages from the motor psu, and I believe it is fairly common to use 20 to 40x the nameplate ratings, with the current controls in the drivers to control the actual maximum current, in this manner the inductance of the motor is overcome faster. One can only drive them as fast as the inductance of the motor coils vs the applied voltage allows the rated current to be achieved. Hopefully I haven't screwed this up too badly... Craig On 9/20/2011 6:56 AM, Dave wrote: I would think that this would be very hard to implement successfully. You are talking about optimizing the acceleration settings to a particular motor/drive/load setup. I can only see this being of a benefit if you were running a fixed part with the same cutter over and over again with a undersized or poorly sized drive system. If you changed materials or cutters or the carriage mass you might have to retune everything. The norm is to make sure that you are not operating your motors that close to the edge of their torque curve. A machine with accels tightly fitted to the motor/drive/load would be very unforgiving. Servos can operate beyond their ratings for short periods of time which sometimes makes them more forgiving, especially if you increase the the max following error allowed. Dave On 9/19/2011 4:02 PM, Andrew wrote: Thinking about decreasing stepper (and servo, to some extent) torque at higher speeds, I just thought that having variable axis acceleration would be perfect. I.e., the highest at lower speeds and lower at higher speeds. Is that ever possible with EMC2? If no, is it hard to implement? Andrew - - All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, gene -- There are four boxes to be used in defense of
Re: [Emc-users] Variable axes acceleration
Gene, just for the records: kinetic energy E = 1/2 times M times V square. We are not on relativistic terms here. But as far as this current discussion is concerned, this is not so important. Peter gene heskett schrieb: On Tuesday, September 20, 2011 03:45:13 PM craig did opine: Although my education, long ago, was in physics, I do not really understand the physics of electric motors. Are there reasons to limit the rate of change of acceleration? Every hear of E=MV2? -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Variable axes acceleration
On Mon, 19 Sep 2011 23:02:08 +0300, you wrote: Thinking about decreasing stepper (and servo, to some extent) torque at higher speeds, I just thought that having variable axis acceleration would be perfect. I.e., the highest at lower speeds and lower at higher speeds. Is that ever possible with EMC2? If no, is it hard to implement? Is that really desirable, or even needed? Surely the ideal is a constant linear acceleration and deceleration? Some rounding of the acceleration curve at the start/end to counteract jerk may be required, the jury's out on that one. Accelerating steppers very quickly through the resonant point is desirable, unfortunately there is no fixed resonant point, it depends on the installation, load and voltage. There's lots of work been done on stepper acceleration profiles, a google search will find dozens of examples, but the majority aim for as close to a linear profile as possible. The complication comes when more than one axis is involved and they are moving different distances ;) Steve Blackmore -- -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Variable axes acceleration
On Tuesday, September 20, 2011 06:10:14 PM Peter Blodow did opine: Gene, just for the records: kinetic energy E = 1/2 times M times V square. We are not on relativistic terms here. But as far as this current discussion is concerned, this is not so important. Peter And I have never seen it notated that way. Probably because I haven't been looking. gene heskett schrieb: On Tuesday, September 20, 2011 03:45:13 PM craig did opine: Although my education, long ago, was in physics, I do not really understand the physics of electric motors. Are there reasons to limit the rate of change of acceleration? Every hear of E=MV2? -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, gene -- There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order. -Ed Howdershelt (Author) You don't go out and kick a mad dog. If you have a mad dog with rabies, you take a gun and shoot him. -- Pat Robertson, TV Evangelist, about Muammar Kadhafy -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Variable axes acceleration
John Prentice wrote: On a related topic I have wondered if it would be possible to have a second set of following error settings for rapids. I feel in my tuning that I sacrifice rapid performance to avoid errors that really only need to be tight during cutting. EMC2 already has it! MIN_FERROR is a constant following error tolerance. FERROR adds an additional amount proportional to commanded velocity of that axis. So, if the axis is moving at 0.5 IPS (not the Seconds, here) and FERROR is set to .01, then MIN_FERROR will be increased by .005 user units. Jon -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
