What is - Torque Mode? Position Mode? Speed/Velocity Mode? - Page 2


Page 2 of 3 FirstFirst 123 LastLast
Results 21 to 40 of 49

Thread: What is - Torque Mode? Position Mode? Speed/Velocity Mode?

  1. #21
    Registered
    Join Date
    Aug 2005
    Location
    can't tell you XD
    Posts
    98
    Downloads
    0
    Uploads
    0

    Smile

    Quote Originally Posted by CarbideBob View Post
    You haven't mentioned what you are going to use for a controller or where you intend to get the +/-10 volts from.
    Bob

    since you have asked, I will be using GD's Pancake Direct Drives, and maybe a 300W BLDC Servo. I am considering VSD-E or Panasonic A4 Drives, or Mitsubishi Drives, or Gecko's G340.

    I'm convinced that I will switch to position mode once I'm familiar with servo tuning, so I better be prepared to have a servo driver equipped with all modes.



  2. #22
    Gold Member
    Join Date
    Mar 2003
    Location
    United States
    Posts
    2839
    Downloads
    0
    Uploads
    0

    Default

    Sunmix,

    I don't mean to belabor the analogy any further but here goes. Phase lag in a system results from the simple fact reaction always follows an action; there is a time delay between the two. Get back in your car for a description of the PID algorithm:

    This time your task is to stay even with a car in the freeway lane next to you. That car represents the servo command and and you will servo your car to it.

    We start off with both cars stopped side by side. The car next to you accelerates from 0 MPH to 80 MPH in an instant (it can do that, you can't). It takes you a second to realize it is rapidly pulling away, putting distance between itself and you.

    You gauge the size of this distance and decide to accelerate. This is the Proportional term in PID. It is the size of the distance between you and the target; the bigger it is the faster you accelerate.

    You also notice the distance is increasing and accelerate even harder. This is the Derivative term in PID. It is the rate of change in the distance between you and the target. It will be very important in a little bit.

    At some point during acceleration your speed will match the target's 80 MPH. That is the instant the distance between you and the target stops growing. You will have to go faster than 80 MPH to catch up so you keep accelerating but less quickly (there is still distance to be made up but it is now shrinking). The Derivative term goes strongly negative because the distance is rapidly shrinking and the P term, while still positive, is decreasing as well. You may actually start applying the brakes. The Derivative term will keep you from overshooting the target. If your judgment is good (P and D terms correct), you will be someplace near the target when your speeds match.

    "Someplace near" the target when "your speeds match" also means the P and D terms (separation distance and rate of distance change) become too small to be usable. They are coarse tools and you now need a precision tool to be exactly even with the target. It is the Integral term, the 'I' in PID. If you are behind the target, accelerate very gently, if you are ahead, decelerate very gently. Your position is now exactly even with the target. The Integral term does result in a continuous "pull an inch ahead, fall an inch behind" motion but it is too small to see.

    PID feedback gives the shortest time to target without overshoot. You are a PID servo-loop every time you drive your car even if you are unaware of it.

    Where phase lag comes into play is the reaction time to the events described above. Your eyes are the "encoder" and there is a delay while your mind processes what you see and sends commands to your foot on the pedal. Say that takes a second while all of the above took 1 minute. That is not a problem.

    Now imagine what would happen if it took 30 seconds to react. You would zag when you should have zigged, accelerated when you should have braked. That is what happens when phase lag is 180 degrees; your reaction is the opposite of what's needed because it's delayed by 1/2 a cycle.

    Mariss



  3. #23
    Registered
    Join Date
    Aug 2005
    Location
    can't tell you XD
    Posts
    98
    Downloads
    0
    Uploads
    0

    Default

    Hi Mariss, I really appreciate for the time used in writing this analogy, I saw you kept online for more than 1/2 hour, thank you very much!

    Like your explanation says, I am driving a car (PID Servo Loop), and I need to keep up with the target car. I need to accelerate until more than 80MPH so I can be in parallel position with the target car.

    Let's say I am in the process of acceleration of going up to 80MPH or more, my accelerometer reads 82MPH. Out of sudden, the target stops. So, I (PID Servo Loop) will retract my car in order to be together with the same position?

    I have understand what the phase lag means. Whenever I tune a servo I must make sure the PID closes the loop at fast as possible, without many retries, to avoid a phase lag.



  4. #24
    Registered Xerxes's Avatar
    Join Date
    Sep 2004
    Location
    Finland
    Posts
    1207
    Downloads
    0
    Uploads
    0

    Default

    Since uncertainty about which mode is best for position control, I have implemented both modes in VSD-E drive:

    First is so called PIV controller where signal path looks like this:
    Position P controller -> Veloctiy PI controller -> Torque PI controller

    and PID controller which looks like this:
    Position PID controller -> Torque PI controller

    In my experience I have found PIV easier to tune in and also significantly stiffer in operation. Most of the expensive drives seem to use PIV even when there are arguments that PID would be theoretically better. Anyway, user has the choice

    Last edited by Xerxes; 10-26-2008 at 04:52 AM.


  5. #25
    Registered
    Join Date
    Aug 2005
    Location
    can't tell you XD
    Posts
    98
    Downloads
    0
    Uploads
    0

    Default

    Quote Originally Posted by Xerxes View Post
    Since uncertainty about which mode is best for position control, I have implemented both modes in VSD-E drive:

    First is so called PIV controller where signal path looks like this:
    Position P controller -> Veloctiy PI controller -> Torque PI controller

    and PID controller which looks like this:
    Position PID controller -> Torque PI controller

    In my experience I have found PIV easier to tune in and also significantly stiffer in operation. Most of the expensive drives seem to use PIV even when there are arguments that PID would be theoretically better. Anyway, user has the choice
    Hmm, is PIV a new method of closed-loop correction? How is it better than PID, in terms of smooth operation?



  6. #26
    Registered Xerxes's Avatar
    Join Date
    Sep 2004
    Location
    Finland
    Posts
    1207
    Downloads
    0
    Uploads
    0

    Default

    PIV is just a name for controller which contains velocity loop cascaded to position controller (the one discussed in this thread and compared to PID->torque controllers).



  7. #27
    Member
    Join Date
    Aug 2015
    Posts
    11
    Downloads
    2
    Uploads
    0

    Default Re: What is - Torque Mode? Position Mode? Speed/Velocity Mode?

    This is a very old thread, and a quite silly thread also. I couldn't see even one commenter who knew what was the proper choice, what were the aspects of selecting the proper servo control mode. And what those modes mean. I'm just telling this whoever read this thread: don't take this thread seriously, bunch of mistakes, misunderstandings, misconceptions.
    Im sorry for tha harsh words, I mean no offence.



  8. #28
    Member mactec54's Avatar
    Join Date
    Jan 2005
    Location
    USA
    Posts
    15362
    Downloads
    0
    Uploads
    0

    Default Re: What is - Torque Mode? Position Mode? Speed/Velocity Mode?

    Quote Originally Posted by Tele2 View Post
    This is a very old thread, and a quite silly thread also. I couldn't see even one commenter who knew what was the proper choice, what were the aspects of selecting the proper servo control mode. And what those modes mean. I'm just telling this whoever read this thread: don't take this thread seriously, bunch of mistakes, misunderstandings, misconceptions.
    Im sorry for tha harsh words, I mean no offence.
    Unless you can add to this thread my post #6 is mostly correct, as to what was being asked at the time, if you need more information I can enlighten you, be more specific in what you want to know

    Mactec54


  9. #29
    Member deadlykitten's Avatar
    Join Date
    Jun 2015
    Location
    Antarctica
    Posts
    4131
    Downloads
    0
    Uploads
    0

    Default Re: What is - Torque Mode? Position Mode? Speed/Velocity Mode?

    come on tele, is 2020, and you just found a ' wrong infos thread ' from 2008 ?

    in case you don't have other plans, you could rejoin it in 2030, you know, for a scheduled check

    just kidding, take it easy / kindly

    we are merely at the start of " Internet of Things / Industrial Revolution 4.0 " era : a mix of AI, plastics, human estrangement, powerful non-state actors ...


  10. #30
    Community Moderator Al_The_Man's Avatar
    Join Date
    Dec 2003
    Location
    Canada
    Posts
    24216
    Downloads
    0
    Uploads
    0

    Default Re: What is - Torque Mode? Position Mode? Speed/Velocity Mode?

    Quote Originally Posted by Tele2 View Post
    This is a very old thread, and a quite silly thread also. I couldn't see even one commenter who knew what was the proper choice, what were the aspects of selecting the proper servo control mode. And what those modes mean. I'm just telling this whoever read this thread: don't take this thread seriously, bunch of mistakes, misunderstandings, misconceptions.
    Im sorry for tha harsh words, I mean no offence.
    You are obviously someone with far greater experience than those of us here that have had several decades of experience, in the case of mine, designing custom motion control using Sophisticated Galil motion controllers,.
    Including one leading manufacturers of drives Quote.
    Maybe in light of what appears to be superior knowledge, maybe you can enlighten us.
    BTW at least one commentor out of "Not even one" here, also runs a successful company in manufacturing drives etc.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


  11. #31
    Member
    Join Date
    Aug 2015
    Posts
    11
    Downloads
    2
    Uploads
    0

    Default Re: What is - Torque Mode? Position Mode? Speed/Velocity Mode?

    Quote Originally Posted by mactec54 View Post
    Unless you can add to this thread my post #6 is mostly correct, as to what was being asked at the time, if you need more information I can enlighten you, be more specific in what you want to know
    Hi Mac,

    I could add to this thread, just the precise answer it's not so short, and have no time to start from the basics. But here is my short answer:

    You could figure out lot of things, just ask the proper questions.
    1.) What does it mean Position, Speed, Torque control exactly. What are the primary parameters you want to take under control in these modes ? The answer is not complicated and you know it precisely.
    2.) What's the purpose of the servo in your machine? Usually it can be used for driving x,y,z axes or it can be used as spindle motor. You said exactly the same.

    3.) What is your primary goal when you move the chipping/milling tool on x,y,z axis.
    A) Do you want to control the force / torque on the acme thread, ballscrew, or pulley what moves the axis ? Do you know at all what are those forces, have you ever calculated them ? Do they have to be persistent and stable, is that the goal ? You'd be surprised if you knew how little torque is able to create HUGE linear force with a ballscrew.
    B) Do you wanna control the speed of that axis ? Faster moving axis or the slower one is the better one ? When you start to turn on your lathe is that your first thought, how fast you will spin the wheels with your hands, because that the most important parameter of turning ?
    C) Do you wanna control the position of the tool, most accurately ? Do you want the tool in the right place to get the most precise diameter of the workpiece ?

    Of course, if you use the servo on your mill/lathe to move the axes, then it must be set POSITION mode !!! Especially and most frequently external positioning mode, when the servo controller sets the position by an external signal, so called "position command pulse input" which can be PUL/DIR, CW/CCW, or Quadrature. Best servos could be set to internal positional mode also, when the position is caclulated by the drive’s Internal Indexer for position control. Which can set about about 16 discrete positions. But this is a special and rarely used mode. You just use your servo with the usual PUL/DIR pulses, just like a closed loop stepper motor. This is what your MACH3/4 or LinuxCNC produces to drive x,y,x

    4.) What is the primary goal when you use the servo as the spindle ?
    A) Do you wanna set a specific torque to keep it stable ? For example 1Nm ? Or 2Nm is better ? Or how many Nm needed for your milling task ? Have you ever calculated the chipping forces, are you sure you have to keep them inalterable but constant during the work ? In torque mode the motor is allowed to change the rpm to keep the torque that you set. In torque mode you must set a max rpm, because at 0 Nm (free spinning spindle) to revolution would be boundless, running towards infinite. Would be loud So in torque mode your revolution will change, can be varied or pulsating. Sounds bad for a lathe or mill.
    B) Do you wanna set the position of the spindle, so you know that it has to stop after 1232.45 revolution ? Thats position is the goal ? Do you have to know and keep under control the number of revolutions ? Nonsense.
    C) But there is a technological parameter, its named cuttin speed, and its calculated by spindle revolution multiplied radius of cutting edge. If you wanna control the cutting speed you have to control the rpm = SPEED of the servo spindle. You want to set it to 3000rpm for example, and you want to keep it stable. The Best CNC macines know what is the diameter of the workpiece momentarily (it's changing as they work) and they are able to change the spindle rpm to keep the cutting speed constant. So the primary parameter is SPEED at spindles. Now if you think that they need to control the torque also to keep the constant speed, you are perfectly right. The servo will solve that, its not your problem, it will change the torque to keep the rpm (SPEED) stable (assuming that the motor power is enough).

    Now check this thread please, is there anyone who recommended POSITION mode and PUL/DIR to the guy for his x,y axes?

    You recommended TORQUE mode for spindle and SPEED for the axes. Meh.
    Sorry I don't have time for more details, you believe me or not it's up to you, I don't wanna start argumentation either offend anyone. And I didn't mention dual modes at all. It's long.



  12. #32
    Member
    Join Date
    Aug 2015
    Posts
    11
    Downloads
    2
    Uploads
    0

    Default Re: What is - Torque Mode? Position Mode? Speed/Velocity Mode?

    Quote Originally Posted by Al_The_Man View Post
    You are obviously someone with far greater experience than those of us here that have had several decades of experience, in the case of mine, designing custom motion control using Sophisticated Galil motion controllers,.
    Including one leading manufacturers of drives Quote.
    Maybe in light of what appears to be superior knowledge, maybe you can enlighten us.
    BTW at least one commentor out of "Not even one" here, also runs a successful company in manufacturing drives etc.
    Al.
    I'm sorry Man, I told you I meant no offence. I don't undertsand your argument about the Company.
    Trump ran a huge country for years. Does it mean that he knows how to set a servo better than anyone else ?



  13. #33
    Member
    Join Date
    Aug 2015
    Posts
    11
    Downloads
    2
    Uploads
    0

    Default Re: What is - Torque Mode? Position Mode? Speed/Velocity Mode?

    Quote Originally Posted by deadlykitten View Post
    come on tele, is 2020, and you just found a ' wrong infos thread ' from 2008 ?

    in case you don't have other plans, you could rejoin it in 2030, you know, for a scheduled check

    just kidding, take it easy / kindly
    It was not intentional Kitten I swear You know youtube, it always brings up funny recommendations. Sometimes Google too.
    I'll be back in 2030 !



  14. #34
    Community Moderator Al_The_Man's Avatar
    Join Date
    Dec 2003
    Location
    Canada
    Posts
    24216
    Downloads
    0
    Uploads
    0

    Default Re: What is - Torque Mode? Position Mode? Speed/Velocity Mode?

    Quote Originally Posted by Tele2 View Post
    I'm sorry Man, I told you I meant no offence. I don't undertsand your argument about the Company.
    Trump ran a huge country for years. Does it mean that he knows how to set a servo better than anyone else ?
    No, But when you do something SUCCESSFULLY on the recommendation of companies that have been providing successful products in the motion control/CNC area since the advent of numerical control, then there is every chance that if you heed their advice and this results in your labours bearing fruit. You somehow conclude that the knowledge you have gained from accredited technical documentation and personal experience is somehow correct .
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


  15. #35
    Community Moderator Jim Dawson's Avatar
    Join Date
    Dec 2013
    Posts
    5717
    Downloads
    0
    Uploads
    0

    Default Re: What is - Torque Mode? Position Mode? Speed/Velocity Mode?

    Quote Originally Posted by Tele2 View Post

    Snip...

    Of course, if you use the servo on your mill/lathe to move the axes, then it must be set POSITION mode !!!

    /snip...

    Ummm, No. Positioning would be the controller's job, via digital, analog, or step and direction control signals sent to the drive. The servo drive just does what it's told. In modern drives, many times in the case of digital or step & direction control, the loop is closed at the drive, and this is sometimes labeled as position control. In all cases with analog control the loop is closed at the controller, and the drive is just a dumb amplifier.

    Jim Dawson
    Sandy, Oregon, USA


  16. #36
    Member
    Join Date
    Aug 2015
    Posts
    11
    Downloads
    2
    Uploads
    0

    Default Re: What is - Torque Mode? Position Mode? Speed/Velocity Mode?

    Quote Originally Posted by Al_The_Man View Post
    No, But when you do something SUCCESSFULLY on the recommendation of companies that have been providing successful products in the motion control/CNC area since the advent of numerical control, then there is every chance that if you heed their advice and this results in your labours bearing fruit. You somehow conclude that the knowledge you have gained from accredited technical documentation and personal experience is somehow correct .
    Al.
    Dear Man, leading a Company being CEO or being electrical engineer and designing controllers and embedded computers, these are two very different things. You start to be a little annoying. I did not attack you personally not at all. Why do you do that ? If you don't like my comment about this thread just delete it, that is a solution don't you think ? I see you are Community Moderator. Stop attacking people's personally, OK. You can say arguments against my arguments that's fine. But I don't care you company or your experience, neither you, personally. Understood ?

    I had to warn readers because this thread is very silly, not mentioning that every people have different opinions and thats funny too.

    "You somehow conclude that the knowledge you have gained from accredited technical documentation and personal experience is somehow correct" - you forgot the University, but mentioned the "experience" and "Company". I don't read accredited technical documentations, I write them.

    You said on this thread - "Torque mode is now the preferred method for CNC control.", and you mentioned also "....you have gained from accredited technical documentation..."

    Summing those two up, please open your servo's accredited documentation and flip to the page titled "Wiring for Torque Control Mode" - or something like that.

    Now please check the diagram. How will you tell to your motor driver what is the x,y,z position you want go with your milling tool ? Which signal is that ? What is the name of the wire ? How will you wire your LinuxCNC MESA controller x,y,z PUL/DIR output, to this motor driver based on this page ? How will you set the tool's position, you have to do that I hope we agree.

    You can see "PUL/DIR" or "Differential Pulse" signals (whatever they name it) on the page "Wiring for Position (Pr & Pt) Control Modes" but NOT on the pages "Wiring for Velocity and Torque Control Modes".
    Can you explain that ? Without attacking my person.

    Laci



  17. #37
    Member
    Join Date
    Aug 2015
    Posts
    11
    Downloads
    2
    Uploads
    0

    Default Re: What is - Torque Mode? Position Mode? Speed/Velocity Mode?

    Quote Originally Posted by Jim Dawson View Post
    Ummm, No. Positioning would be the controller's job, via digital, analog, or step and direction control signals sent to the drive. The servo drive just does what it's told. In modern drives, many times in the case of digital or step & direction control, the loop is closed at the drive, and this is sometimes labeled as position control. In all cases with analog control the loop is closed at the controller, and the drive is just a dumb amplifier.
    Exactly, so I'm asking you too. Open your driver manual at the page "Wiring for Torque Control Mode" (or speed mode if you want so) and seek for the pins named : "step and direction control signal" - just go and check it please !
    - digital ??? What kind of digital input will set the x,y,z position on that drive. Please be specific. What is the name of the pin, or signal ? Today's modern drivers can be controlled via etherned or a special CAN bus, but this thread is from 2008
    - analog ??? Position controlled by analog signal ? What ? Did you know that analog control is not accurate? How will you set 5 mil (thal) position accuracy with that ? You can set speed and torque with analog +-10V and thats it.
    Meh.



  18. #38
    Community Moderator Jim Dawson's Avatar
    Join Date
    Dec 2013
    Posts
    5717
    Downloads
    0
    Uploads
    0

    Default Re: What is - Torque Mode? Position Mode? Speed/Velocity Mode?

    Quote Originally Posted by Tele2 View Post
    Exactly, so I'm asking you too. Open your driver manual at the page "Wiring for Torque Control Mode" (or speed mode if you want so) and seek for the pins named : "step and direction control signal" - just go and check it please !
    - digital ??? What kind of digital input will set the x,y,z position on that drive. Please be specific. What is the name of the pin, or signal ? Today's modern drivers can be controlled via etherned or a special CAN bus, but this thread is from 2008
    - analog ??? Position controlled by analog signal ? What ? Did you know that analog control is not accurate? How will you set 5 mil (thal) position accuracy with that ? You can set speed and torque with analog +-10V and thats it.
    Meh.
    Why would I try to use S&D inputs for torque or velocity control? I think that would not work.

    As far as digital control, yes I am talking about modern drives using EtherCAT or CAN Bus.

    Well, my milling machine uses analog velocity control servos and has a resolution of 1 micron, with repeatability of +/- 4 microns. My lathe uses analog torque control servos, also with 1 micron resolution, with repeatability of +/- 5 microns in normal production.

    I would say that analog control can be pretty accurate.

    Jim Dawson
    Sandy, Oregon, USA


  19. #39
    Member
    Join Date
    Aug 2015
    Posts
    11
    Downloads
    2
    Uploads
    0

    Default Re: What is - Torque Mode? Position Mode? Speed/Velocity Mode?

    Quote Originally Posted by Jim Dawson View Post
    Why would I try to use S&D inputs for torque or velocity control? I think that would not work.

    As far as digital control, yes I am talking about modern drives using EtherCAT or CAN Bus.

    Well, my milling machine uses analog velocity control servos and has a resolution of 1 micron, with repeatability of +/- 4 microns. My lathe uses analog torque control servos, also with 1 micron resolution, with repeatability of +/- 5 microns in normal production.

    I would say that analog control can be pretty accurate.
    Exactly !!! It would not work because you could not do that because R&D pins are not valid in that mode, they don't exist on the diagram. But you just said that: how can we control the driver:
    1 - R&D
    2 - digital signal
    3 - analog signal

    This is what you said. You can't use R&D and you dont't, so why did you mention it.
    You can't use analog signal for that, either that would be nonsense, (you turn a potentionmeter and you set your mill's gantry position with 5 thal accuracy with that, total nonsense, you were not serious)
    The remaining is only "digital"

    CANopen is a new technology and still rare and a little expensive.
    Many motor drivers are not CANopen compatible. Actually most of them.
    But they have Position,Speed,Torque control modes long ago. How will you control the position WITHOUT CANopen and EtherCat ?

    "...my milling machine uses analog velocity control servos ... I would say that analog control can be pretty accurate." - jeez, it's not !
    And in speed control mode your analog +-10V signal controls the speed (rpm) of the motor not the position.
    You drive it faster with 8V and slower with 3V and 10V will be the max. revolution/min !!! That is the speed control !
    It has nothing to do with the steps the motor advanced ahead ?

    Would you please name the brand and the type of your servo driver and motor and we can check if you can set any position with any kind of analog signal.
    I hope I'll get response to this very simple asking. Then I'll link the page of the driver here OK ?
    At the "Wiring for Torque Control Mode" or at the "Wiring for Speed Control Mode", as you like it.

    And what kind of motion controller SW and HW you use ? LinuxCNC with a MESA card ? Or Windows with Mach4 ans Smoothstepper ?
    People could check how can they set an analog signal with those motion controllers for x,y,z axes.

    Anyway I think I give it up, this is totally pointless and waste of time. You guys WON, you have company and experience, servo engineers are idiots.

    Regards,
    Laci



  20. #40
    Community Moderator Jim Dawson's Avatar
    Join Date
    Dec 2013
    Posts
    5717
    Downloads
    0
    Uploads
    0

    Default Re: What is - Torque Mode? Position Mode? Speed/Velocity Mode?

    Quote Originally Posted by Tele2 View Post
    Exactly !!! It would not work because you could not do that because R&D pins are not valid in that mode, they don't exist on the diagram. But you just said that: how can we control the driver:
    1 - R&D
    2 - digital signal
    3 - analog signal

    This is what you said. You can't use R&D and you dont't, so why did you mention it.
    You can't use analog signal for that, either that would be nonsense, (you turn a potentionmeter and you set your mill's gantry position with 5 thal accuracy with that, total nonsense, you were not serious)
    The remaining is only "digital"

    CANopen is a new technology and still rare and a little expensive.
    Many motor drivers are not CANopen compatible. Actually most of them.
    But they have Position,Speed,Torque control modes long ago. How will you control the position WITHOUT CANopen and EtherCat ?

    "...my milling machine uses analog velocity control servos ... I would say that analog control can be pretty accurate." - jeez, it's not !
    And in speed control mode your analog +-10V signal controls the speed (rpm) of the motor not the position.
    You drive it faster with 8V and slower with 3V and 10V will be the max. revolution/min !!! That is the speed control !
    It has nothing to do with the steps the motor advanced ahead ?

    Would you please name the brand and the type of your servo driver and motor and we can check if you can set any position with any kind of analog signal.
    I hope I'll get response to this very simple asking. Then I'll link the page of the driver here OK ?
    At the "Wiring for Torque Control Mode" or at the "Wiring for Speed Control Mode", as you like it.

    And what kind of motion controller SW and HW you use ? LinuxCNC with a MESA card ? Or Windows with Mach4 ans Smoothstepper ?
    People could check how can they set an analog signal with those motion controllers for x,y,z axes.

    Anyway I think I give it up, this is totally pointless and waste of time. You guys WON, you have company and experience, servo engineers are idiots.

    Regards,
    Laci
    You clearly have no idea what you are talking about.

    Step & Direction (S&D) position control is a somewhat recent development, maybe 30 years old. Analog servo position control goes back goes back at least 50 years and is still in use today on higher end systems. It is not normally used on hobby class machines do to the complexity and expense.

    Analog control is not done with a pot but rather is done with an analog output motion controller. With a proper controller and feedback device, analog position control works very well and is highly accurate.

    For controllers, I personally use Galil Motion Control products in my equipment. All of the Galil products (except their EtherCAT units) can be programmed to output either analog or S&D. The Galil products are industrial class devices and are used in many industries where motion control is required.

    On my mill X and Y axis I have Servo Dynamics brushed DC analog velocity drives and Baldor brushed DC servo motors. These are about 35 years old and are still working fine. The Z axis is a NEMA 34 stepper, driven by a rather expensive analog input stepper drive. The position feedback on all axes is from Renishaw 1 micron magnetic linear scales which are connected to the Galil controller, and thus the loop is closed at the controller. I wrote my own CNC operating software.

    My lathe uses DMM Technologies 1.8KW AC drives and motors on the X and Z axis. These are operated in analog torque mode and are controlled by a Galil controller. The position feedback is taken from the drive encoder output, which is derived from the motor encoder feedback to the drive. Again the loop is closed at the controller and the drive just acts as a dumb transconductance amplifier. Again I wrote my own CNC operating software.

    The DMM Technologies servos can be operated in S&D, analog velocity mode, or analog torque mode.

    Jim Dawson
    Sandy, Oregon, USA


Page 2 of 3 FirstFirst 123 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


About CNCzone.com

    We are the largest and most active discussion forum for manufacturing industry. The site is 100% free to join and use, so join today!

Follow us on


Our Brands

What is - Torque Mode? Position Mode? Speed/Velocity Mode?

What is - Torque Mode? Position Mode? Speed/Velocity Mode?