Re: [Emc-users] HOME Sensors
I'm impressed with your answer. I recognize that I didn't have idea about cable pairing in order to improve noise immunity. I will take care of this, and put a section on the web to comment on this. I wonder if you have also a Eurotherm 631 driver, because you seem to be very familiar with our setup. I've reviewed the information regarding resolvers, and yes, you are right again. The motor has a resolver and the signal it produces is translated to quadrature encoder signals by the driver. I tried to figure out what kind of resolver it uses, but I found only that it is a 2 pole Eurotherm transmitter resolver, no references in Eurotherm web page. So I don't know if the signal is transmitted analogically or digitally from the resolver to the drive (just curiosity). I have configured the quadrature signal in the drive to be 4096 steps per revolution (the maximum possible at the drive). So I don't know how confident can I be about the accuracy of the quadrature steps given by the drive. In a quadrature encoder of the type based on printed disk, with the same amount of steps per rev, I think you can be confident about the accuracy being +-360/4096 degrees, provided that the disk has been printed OK, it is well attached to the shaft and that no meaningful vibrations affect the sensors (I think). But I'm not sure the induced currents in a 2 pole resolver can be that accurate when related to the angle. I mean you can generate 4096 per rev quadrature steps based on an imprecise periodical and continuous analog signal, if you have a decent 12 bit A/D converter, but this does not necessarily implies that the quadrature signal generated is accurate at all. The only advantage I see to a resolver against a quadrature encoder, is the former being able to give a continuous signal, so a good A/D (say 16 bits) will allow you to implement a more precise PID when the motor is at zero velocity. But this advantage will only noticed if we can read directly the analog signal given by the resolver, something that I judge difficult to do in our setup. I'm thinking (in a future arrangement) about placing linear encoders along the guide, avoiding the possible imprecise measurements given by the resolver, and the imprecision associated to the backlash between rotary and linear motor. Feel free to comment on any of the above. I'm just speaking (loud) about my lack of knowledge regarding the fine details needed to tune or design a good machine for CNC. Thanks very much indeed Javier I agree that the pins on the x40 connector are connected to the corresponding pins on the motenc-100 terminal board. You can, however, improve the noise immunity by rearranging the wires on *both* ends of the cable. http://www.imac.unavarra.es/parallel/images/argazkiak/DSCN1697.JPG In this image, B+ and B- are connected to the blue/blue-white pair, so the B channel signal has added immunity from noise and crosstalk. On the other hand, the A channel and X channel signals are each split between two pairs, so neither receives the benefit of running over a twisted pair. If you can remake the RJ-45 end of the cable, you can put each channel on its own pair and get additional noise immunity. That was what I was trying to say earlier. There's a writeup on balanced signals and twisted pair here: http://www.duxcw.com/digest/Howto/network/cable/cable4.htm Regards, Jim - Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnkkid=120709bid=263057dat=121642 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users - Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnkkid=120709bid=263057dat=121642 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] HOME Sensors
On Mon, 2007-02-05 at 12:28 -0500, Jim Register wrote: On Mon, 2007-02-05 at 14:24 +0100, Javier Ros Ganuza wrote: On Mon, 2007-02-05 at 07:53 -0500, Jim Register wrote: On Mon, 2007-02-05 at 11:11 +0100, Javier Ros Ganuza wrote: Returning to my previous thread about HOMING. I did read the information pointed out here (section 5.4 of the manual), and there is some thing I can understand: What is index pulse?. I have brushless servos with quadrature encoders. Is the index pulse signal the one from the quadrature encoder, or is it a different signal (the one coming for hal sensors, something entirely different, or something that can be arbitrarily assigned within EMC, or..)???. Javier, The index pulse would come from the simulated encoder on the 631 servo drive, on the X40 pins labeled Z and /Z. In our case, the Z or /Z are not simulated (I think :) ), the brushless have a quadrature encoder, and we are driving all to the motenc-100 terminal board. According to the 631 docs, your motor actually has a resolver instead of an encoder; the 631 driver simulates the encoder signals. That's just a minor detail at the moment, but it may be important when you are troubleshooting. It sounds like a very nice arrangement. Sorry if it sounds too trivial, but I'm lost, what is the diferencie between encoder and resolver. Well, I know what is a encoder, but I was thinking that a resolver was in fact a encoder. So what is a resolver (a potentiometer?)? http://imac/parallel/images/argazkiak/DSCN1697.JPG shows the conection of the RJ45 standard ethernet cable to the board (left-up) Sorry for the mistake, the server was in my internal network. The fully qualified name is: http://www.imac.unavarra.es/parallel/images/argazkiak/DSCN1697.JPG Oh, the X40 connector does not have the pairs on the same pins as an RJ45 Ethernet connection. If you used a stock Ethernet cable, GND and /Z will be on one pair, Z and /A on another, and A and 5VI on a third. Only B and /B will be on a pair. You need to wire the RJ45 end so that each signal has its own pair, or the twisted pairs in the cable will actually work against you. We've linked the individual cables following the diferent colors of the cables that can be seen thought the plastic connector and the conection diagram provided for x40 in the 631 manual, the RJ45 cable has been open in the opposite end, and corresponding connections has been made following motenc-100 terminal board specifications. EMC wonderfully drives the assembly so I think we've made proper connections in this side. And in http://imac/parallel/images/argazkiak/DSCN1691.JPG you can see the Oposite end of the same RJ45 cable, conected to the X40 input. should be http://www.imac.unavarra.es/parallel/images/argazkiak/DSCN1691.JPG Unfortunately, those links take me to the Apple(tm) website, but I did find the images on your website. (The cabinet looks nice, by the way.) We have configured the 631 servo to output quadrature signals from X40. So if I got the idea: We can use index pulse, and the index pulse is taken from the Z and/or /Z signals that is being fed to the card. So activating index pulse in the HOMING configuration will work (in fact it works but we didn't known if index pulse was actually being used) using index pulse.??? Yes, the Motenc driver supports the index pulse in EMC2.1 So in general (just for curiosity), index pulse is always taken from Z and/or /Z signal from quadrature encoder??? Correct. It has been very clarifying for me. So, it can be said that: index pulse is a concept internally defined by EMC and depending on hardware the driver can implement this index pulse in different ways. It happens that with the motenc-100 driver, or with other divers using quadrature encoders, the index pulse is defined using available Z and/or /Z quadrature signals. Do you agree? Thanks a lot Javier Many thanks Javier Ros You are welcome. Jim - Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnkkid=120709bid=263057dat=121642 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users - Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
Re: [Emc-users] HOME Sensors
Javier Ros Ganuza wrote: [most of the thread snipped] Sorry if it sounds too trivial, but I'm lost, what is the diferencie between encoder and resolver. Well, I know what is a encoder, but I was thinking that a resolver was in fact a encoder. So what is a resolver (a potentiometer?)? A resolver is a different kind of sensor, which detects the rotation of a magnetic/electric field. These are AC excited analog sensors which will give you absolute rotation information from 0-360 degrees. See this wikipedia page: http://en.wikipedia.org/wiki/Resolver_%28electrical%29 An encoder is a digital device, which outputs a code based on position. This will either be a binary code giving the absolute position or (more common for CNC) an incremental quadrature code based on movement. See this wikipedia page: http://en.wikipedia.org/wiki/Rotary_encoder So in general (just for curiosity), index pulse is always taken from Z and/or /Z signal from quadrature encoder??? Most incremental encoders with index outputs label the index channel Z. I think I is also used sometimes. Correct. It has been very clarifying for me. So, it can be said that: index pulse is a concept internally defined by EMC and depending on hardware the driver can implement this index pulse in different ways. It happens that with the motenc-100 driver, or with other divers using quadrature encoders, the index pulse is defined using available Z and/or /Z quadrature signals. No. Index pulses are not an EMC-specific thing. Index is a separate channel that is used for detecting the orientation of the motor shaft. A normal incremental quadrature encoder can only tell you that the shaft has moved and in which direction. The index tells you that the shaft is at a certain angle, which people usually define as 0 degrees rotation. Do you agree? Thanks a lot Javier Good luck - Steve - Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnkkid=120709bid=263057dat=121642 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] HOME Sensors
On Mon, 2007-02-05 at 11:11 +0100, Javier Ros Ganuza wrote: Returning to my previous thread about HOMING. I did read the information pointed out here (section 5.4 of the manual), and there is some thing I can understand: What is index pulse?. I have brushless servos with quadrature encoders. Is the index pulse signal the one from the quadrature encoder, or is it a different signal (the one coming for hal sensors, something entirely different, or something that can be arbitrarily assigned within EMC, or..)???. Javier, The index pulse would come from the simulated encoder on the 631 servo drive, on the X40 pins labeled Z and /Z. Jim - Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnkkid=120709bid=263057dat=121642 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] HOME Sensors
On Mon, 2007-02-05 at 07:53 -0500, Jim Register wrote: On Mon, 2007-02-05 at 11:11 +0100, Javier Ros Ganuza wrote: Returning to my previous thread about HOMING. I did read the information pointed out here (section 5.4 of the manual), and there is some thing I can understand: What is index pulse?. I have brushless servos with quadrature encoders. Is the index pulse signal the one from the quadrature encoder, or is it a different signal (the one coming for hal sensors, something entirely different, or something that can be arbitrarily assigned within EMC, or..)???. Javier, The index pulse would come from the simulated encoder on the 631 servo drive, on the X40 pins labeled Z and /Z. In our case, the Z or /Z are not simulated (I think :) ), the brushless have a quadrature encoder, and we are driving all to the motenc-100 terminal board. http://imac/parallel/images/argazkiak/DSCN1697.JPG shows the conection of the RJ45 standard ethernet cable to the board (left-up) And in http://imac/parallel/images/argazkiak/DSCN1691.JPG you can see the Oposite end of the same RJ45 cable, conected to the X40 input. We have configured the 631 servo to output quadrature signals from X40. So if I got the idea: We can use index pulse, and the index pulse is taken from the Z and/or /Z signals that is being fed to the card. So activating index pulse in the HOMING configuration will work (in fact it works but we didn't known if index pulse was actually being used) using index pulse.??? So in general (just for curiosity), index pulse is always taken from Z and/or /Z signal from quadrature encoder??? Many thanks Javier Ros Jim - Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnkkid=120709bid=263057dat=121642 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users - Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnkkid=120709bid=263057dat=121642 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] HOME Sensors
The home switches I'm using are from Automation Direct (www.automationdirect.com) and they're cheap too, at $13.75 ea. Just go to their site and search for P/N AAP2T14Z11. They offer them with different actuators (plunger, roller, lever, etc.), and claim a repeat accuracy of 0.01mm at 1 million operations. RogerN wrote: McMaster Carr has some ultra precision limit switches with 1 micron actuation. http://www.mcmaster.com/ Go to their online catalog page 861 at the bottom of the page. Or search for ultra precision limit switch. They're expensive but it's nice to know they exist if you can justify the price. - Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnkkid=120709bid=263057dat=121642 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] HOME Sensors
McMaster Carr has some ultra precision limit switches with 1 micron actuation. http://www.mcmaster.com/ Go to their online catalog page 861 at the bottom of the page. Or search for ultra precision limit switch. They're expensive but it's nice to know they exist if you can justify the price. - Original Message - From: Javier Ros Ganuza [EMAIL PROTECTED] To: emc-users@lists.sourceforge.net Sent: Wednesday, December 20, 2006 12:54 PM Subject: [Emc-users] HOME Sensors I'm not sure if this is the correct place to ask about this :( I have no idea of the type of sensors that are used for HOMING, snip - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.phpp=sourceforgeCID=DEVDEV ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] HOME Sensors
Thanks to all for your quick response. Let's introduce myself. 2 year ago I appeared in this list saying that I wanted to make a hexaglide type parallel manipulator. Then I got a lot of support from this list, bibliography references,... We had six old brussless motors with drives (eurotherm), and 4086 per revolution encoders, and 6 TKM Linear guides (aproximately 1 meter long and 10mm per rev) has been bought, and motenc-100 8 axis card. 3 months ago, trough public financiation, I have now an engineer working with me (Aitor Plaza), and we have started building the whole thing. Mechanical connexions between motors and linear guides has been mechanized, and we have asembler our first guide with 3 identical magnetic Omrom contacts (lower and up limits and home). EMC2 was able to move the subsystem wonderfully two days ago ( :)) !!). I'm impressed. We have made the drawings of the supporting structure, and a local machinist is making it right know. The next stem is to mount the guides motors and sensor in the structure and to get a deeper knowledge of EMC2, in order to implement the parallel kinematic structure. (we will com back with questions regarding to this) In parallel we'll finish the design of the head, and will try to get financial support to that end. The objective is to make a kinematical calibration of the whole thing, in order to correct the assemblies imperfections as much as possible. To that end a reference position for any of the guides has to be know precisely (things are absolute due to the nonlinearity of the system kinematics and we need an absolute reference), we want to home the robot to a given position, an we need this position to be very repeatable between different runs. We'll revise the referenced manual in detail the emc handbook esplains how to enable the use index for homing. (and other neat homing stuff) but I'm thinking that we have to do some measurements about the repeatability in homing that EMC2 achieves using the mentioned Omrom relay before going any further. We will try to figure how to do this using EMC. We will also investigate the ability of the system to maintain a given position when forces are applied to the system. I have no previous experience about the whole subject so I'm planing to come back with some questions, I hope this not to be a problem for this list, although some the questions can be not directly related to EMC2. I would like to build a web page in order to document the different steps of the construction design and EMC related issues. If it is done I'll publicize it in this list. Thanks again Javier Ros and Aitor Plaza - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.phpp=sourceforgeCID=DEVDEV ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] HOME Sensors
Javier, Welcome to EMC2 my machine uses proximity switches as home and limit switches. However during homing i also use my encoder index pulse to nail down my home position. the emc handbook esplains how to enable the use index for homing. (and other neat homing stuff) If you are using steppers, you probably do not have shaft encoders. but you could always just hook up an encoder per axis and just use the index pulse output to find home.. i agree that the switch only homing probably does not always get back to home as accurately as the home swtch then find index pulse setup, or at the least it should be much closer, consistantly. Linux rocksdoze blows... Registered Linux User #348337 --- On Wed 12/20, Javier Ros Ganuza [EMAIL PROTECTED] wrote: From: Javier Ros Ganuza [mailto: [EMAIL PROTECTED] To: emc-users@lists.sourceforge.net Date: Wed, 20 Dec 2006 19:54:05 +0100 Subject: [Emc-users] HOME Sensors I'm not sure if this is the correct place to ask about this :(I have no idea of the type of sensors that are used for HOMING,I'm using magnetic presence relays from Omrom, that came with thelinear guide I'm using, but I think that precision is a must for a home sensor(at least it is for my application), so:Can you point me to specific HOME sensors/relay with precision /machining in mind? (brands, or type)Thanks in advanceJavier -Take Surveys. Earn Cash. Influence the Future of ITJoin SourceForge.net's Techsay panel and you'll get the chance to share youropinions on IT business topics through brief surveys - and earn cashhttp://www.techsay.com/default.php?page=join.phpp=sourceforgeCID=DEVDEV___Emc-users mailing [EMAIL PROTECTED]://lists.sourceforge.net/lists/listinfo/emc-users ___ Join Excite! - http://www.excite.com The most personalized portal on the Web! - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.phpp=sourceforgeCID=DEVDEV ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
