I went to the three day TI Industrial Control Workshop in Santa Clara.Â Instead of repeating stuff (such as class outline) that you can read on the wiki link (above), I am going to give my impressions.
The bottom line: yes, the workshop is well worth attending if you like to (or just have to) control motors.Â 5/23/2013: I also want to add that I think this workshop is good for automation developers like myself.Â OK, I’m not sure it’s worth flying to another city to attend, but if there’s one close (next one is 17-19 September 2013 at Brookfield, WI) then it’s good to attend — you’ll learn a lot more about what goes on underneath the covers of your VFD or servo drive.Â I know I have a better understanding and appreciation of my drives.Â Also, you can just about do the course on your own by downloading the materials, but it’s not the same experience.
Disclaimer:Â I paid for this class myself (OK, at $79 it wasn’t a big deal – and the price includes snacks, lunch, and a F28069 controlStick); it was a very nice break from my typical workdays.
Update Feb 2014:I notice TI now has 4 videos from a more recent Control Theory Seminar, with the first episode here, and videos for the C2000 One Day Workshop, with the first module here (there’s also an older set of video modules).Â I couldn’t find videos for Day 2 (Motion Control Theory), although TI has a wide variety of other motor control videos.Â So download the materials, watch these videos, and you’re almost there!Â (But I still recommend attending in person if you can).
Considering TI must be subsidizing the workshop, it had amazingly little marketing content – less than a typical trade mag article.Â There was no mention of TI products at all on the first day (control theory) and very little on the second day (mostly pride in TI’s new instaSpin solutions).Â The third day was all about TI products (F28x DSP), but it was all about the product (architecture, peripherals, Code Composer Studio, etc), not marketing.
Overall, there were many good discussions, and lots of questions.Â I enjoyed learning about what other people are doing.
I think all three instructors did a good job; the biggest issue was time – each class easily could’ve been at least a week, so they had a real challenge trying to fit in as much material as possible, explaining it in an understandable manner, while still answering questions (and all three did a good job of answering the many questions).
Day 1 – Control Theory (Richard Poley)
On day 1 I felt like I was back in college; it was like a month (or more!) of college stuffed into one day — and the soft-spoken instructor, Richard Poley,Â reminded me of a college professor.
You do need to have a good math background to follow the theory.Â Fortunately I had a lot of math in college, and I did some reviewing via wikipedia before the workshop.Â I won’t claim I understood everything perfectly, but I felt I remembered enough to follow the basic concepts.
The theory got a little practical at the end of the day with sections on Digital Controller Design, Implementation Considerations, and a Suggested Design Checklist.
I’m pretty sure the vast majority of attendees don’t use control theory day to day.Â I know I don’t; for example, we rarely have problems tuning motion controller PID loops.Â So for me, the theory isn’t very useful for my day today tasks; in fact, trying to use it when it’s not necessary is a waste of time.
But it’s still good to know the theory for when the normal experienced-based approach doesn’t work.Â (The same applies to programming, say sorting: if you have a small set of data, all sorting methods will be reasonably quick.Â But if you have large data sets, knowing the theory of different sorting methods is critical).
I’m now interested in learning about state variable control theory, which is covered in the two day version of the Control Theory seminar, but it will be a while before I’ll be able to find time for project.
Day 2 – Motor Control Theory (Dave Wilson)
Dave Wilson is a motor geek and a primary contributor to TI’s Motor Control blog, which is a treasure trove of motor control information (even if you don’t use TI chips, since most of info isn’t TI-specific).
Dave Wilson emphasized AC induction motors and servo motors, because none of us were interested in stepper motors.Â He covered motor control theory and all the common algorithms (such as field oriented control).Â He discussed advantages and disadvantages of the different motor types and motor control algorithms.Â He did a good job of answering the many questions.Â And, yes, he is very excited by TI’s instaSPIN solutions (especially instaSPIN-FOC).
I really like Dave Wilson’s Power Point and VisSim animations that graphically showed what was going on to make the motors spin.
Day 3 – Intro to F28x (Ken Schachter)
This day was a rapid fire introduction to the F28x DSP series.Â The instructor, Ken Schachter, gave an overview of the peripherals, an overview of the available software such as controlSuite, and then we spent a lot of time doing labs that showed off some of the Code Composer Studio (CCS) goodness (like graphing memory).
I’d call the class an orientation – I wouldn’t even say I become comfortable, but I do feel like I got my feet wet with the tools, and have a better idea of how to start.Â CCS is pretty intimidating at first, and TI does provide a lot of libraries and examples.
May 21, 2013 No Comments
I just took a look at the specifications for some recent integrated motors; integrated motors combine the motor, drive, and controller in one package.Â I’ve used motors from all three companies, but not these particular models.
Faulhaber BX4 Series
The Faulhaber BX4 series are attractive,Â compact (22, 32, or 35mm diameter) brushless DC motors with integrated encoders, servo drives, and servo controllers.
- Versions are available with CANOpen or RS-232 interfaces (I’d use CANOpen, of course).
- They can be paired with a 22F series gearhead, but unfortunately, no zero backlash gearheads are available, and it doesn’t sound like this will change (which means I won’t be using them any time soon).
- Versions with separate controller power are available.Â This extremely useful feature allows you to turn off motor power (e.g. because of an E-Stop) while still maintaining motor position.
Schneider Electric Motion
Schneider Electric Motion USA (formerly IMS) now has a Ethernet option for their all-in-one MDrives.
- The MDrives combine a stepper motor and driver, and, on the Motion Control versions, a controller.Â Encoders are optional; adding an encoder does not increase the motor length (nice job!).
- Some models feature their Hybrid Motion technology, which detects stalls, enlarges the stepper’s torque curve, and more.
- The Ethernet interface supports Modbus/TCP and MCode/TCP (MCode/TCP basically extends the MDrive Motion Control programming model from serial to Ethernet).
- MDrives are also available with RS-485 and CANOpen interfaces.
Animatics has a new interface option for their integrated SmartMotors, the Combitronic network with a maximum speed of 1M bit/sec.
- The Combitronic network uses the CAN bus as its physical layer.
- It extends the Animatics programming language to the entire Combitronic network; for example, any SmartMotor can easily access any variables on other SmartMotors on the network.
- So Animatics claims Combitronic allows true distributed processing; you can treat the whole network of SmartMotors as one large multi-axis controller.
- You should be to do similar things with other networks; for example, use programmable CANOpen nodes (such as Wago 750-838’s) and share variables via PDOs.Â However, I am not aware of another implementation that looks as easy to use.
- On the other hand, I’m not a fan of the Animatics programming language; it quickly becomes very limiting for complex tasks.
- Another nice feature is that the Combitronic network “plays nicely” with other CAN based network; since it will not interfere with CANOpen or DeviceNet traffic, you can mix Combitronic devices on the same CAN network with CANOpen or DeviceNet devices.
- SmartMotors are also available with RS-232, CANOpen, DeviceNet, Profibus, and Ethernet TCP/IP interfaces.
- Now you can get SmartMotors with separate controller power.Â As I noted above, this is a great feature.Â I have a SmartMotor application using older models without separate power, and it sucks (the SmartMotor has to be re-homed after every Light Curtain interruption or E-Stop).
I do think Animatics overstates their advantages; however, they are a good fit for the right application.Â For example, I once did a X-Y table with two SmartMotors, controlled by a sweet CH Products analog joystick.Â The joystick’s analog output was fed directly to the SmartMotors, so there was no controller (PC or PLC) required.
Although integrated motors are cool, in many applications a regular motor is a better fit.Â The combination of a standard motor and a network drive (amplifier + controller) is almost as easy to wire, often less expensive, and much more flexible.
If I have a choice, I will use an integrated motor with a standard fieldbus (such as CANOpen) over a programmable model — motor manufacturers simply do not know how to create decent programming languages.Â I have programmed both MDrives and SmartMotors; the experience is like a trip back to 1977 and TRS-80’s.
I find it interesting that neither manufacturer supporting Ethernet uses a real time protocol such as Powerlink, EtherCAT, or Profinet-IRT.
January 20, 2011 No Comments
I think it’s interesting that there are so few switch mode power supplies (SMPS) designed for powering motors.Â Motor power requirements are different from electronics; voltage regulation isn’t critical.Â Servo motors benefit from a large current peak (overload) capability and sometimes need a shunt.Â Steppers are best with a power supply designed to handle a rapidly changing inductive load.
A typical switch mode power supply, however, is designed for tight voltage regulation, does not have a shunt and handles over current by limiting current to its maximum rating.
Some switching power supplies are better because they have 20% to 50% peak capacity for a brief time.Â I’ve seen this capability in models from Cabur (sold by ASI in the US), Puls, and Delta; I’m sure there are other examples.
I’ve used the Delta CliQ series for servo motor power, and so far they’ve worked well.Â The CliQ can handle 50% over current for 3 seconds, the pricing is quite good (under $150 for 24V at 10A), but they’re only available for 12V and 24V.
The first designed for motors SMPS I discovered was the IMS ISP200/300 series, which are unregulated switching supplies specifically designed for handling the rapidly changing, inductive loads typical of stepper motors or DC motors.Â IMS is now Schneider Electric, and they have discontinued the ISP series.
I don’t really consider the Galil PSR series a SMPS for motors; it looks like an ordinary enclosed switcher with an added shunt resistor.Â The PSR costs $250, and is available in 24V at 12A or 48V at 6A.
I recently discovered a second SMPS for motors, the Cabur XC series (sold in the US by ASI).Â They have a 72-85V output at 3.1A, 6.6A, or 13.3A, have a 20% reserve capacity when <45C, can handle 50% over current for 5 seconds, and have output over-voltage protection (equivalent to a shunt).
It’s interesting to compare the XCSF500G (72V at 6.6A) to the Logosol LS-872.Â Logosol makes my favorite linear power supplies (I own a LS-1148 and use it extensively); they are relatively compact, are switch selectable between 115V and 230V input, have ESTOP inputs, front panel mount fuses, and are available in a variety of output voltages.Â (The only other 120V/240V switch selectable linear motor power supply I’ve been able to find is Copley’sÂ DP models in their PST series, but they cost much more).
|Cabur XCSF500G||Logosol LS-872|
|Input Voltage||90-132VAC or 187-264VAC||100-120VAC or 200-240VAC (switch selectable)|
|Voltage Regulation||<1%||-10%, +15%|
|Current, Max Cont||6.7A||8A (50% duty cycle)|
|Current, Peak||10A for 5 sec||20A for 5 sec|
|Weight||2.6 lbs||9 lbs|
|Dimensions||Not listed; appears to be smaller than the LS-872||8.55″ x 6.7″ x 2.8″|
|Other features||DIN Rail Mount
Output overvoltage protection
Short circuit, overload, and over temp protection
Separate, unregulated 24V 2.5A power supply
|Approx. Price||$550||$425 (no shunt)|
October 2, 2010 No Comments
Recently, I had to select a servo motor.Â We had already chosen to use a NEMA 23 mount with a 0.25″ shaft, and had other requirements such as maximum length, torque, speed, and voltage.
I was amazed at the different shaft diameters and lengths supposedly standard NEMA 23 motors have — I recall 0.25″, 8mm, and 0.375″ diameters, and can’t remember all the lengths.Â It was even worse when I had to select a NEMA 17 motor a while ago– at least one manufacturer’s supposedly NEMA 17 mount wasn’t the same as everyone else.
Then of course there are all the non-standard mount motors – but I only use those as a last resort, since I’ve already had motors go out of production twice; at least with a standard mount, there’s a possibility of finding a suitable replacement.
Maybe there are other standards: maybe the various European and Japanese 40mm, 60mm, and larger motors really do follow a standard, but I don’t have time to analyze them all.
Connectors are even worse.Â I can understand why manufacturers use different kinds of connectors, and I know there are no connector standards.Â A motor intended for harsh environments needs a tough but expensive connector, while a light duty motor is much better off with a cheap connector (such as Molex or Tyco/AMP crimp connectors) or flying leads.Â But, just like industrial Ethernet, it’s easy to think: do we really need all those choices?Â Couldn’t we have just three or four?
I personally like sub-D connectors a lot, since you can get high power (Combo-D), can use crimp pins or solder cups, and choose from a wide range of backshells (including straight, right angle, and 45 degree in metal, metalized plastic, and plastic) and manufacturers.
Of course, pin-outs are even more varied.Â For example, on the controller side, Galil (DMC-21×3/AMP205x0 combo), AMC (DX30, DX60, etc), and Copley (ADP series) all use HD15 connectors for feedback, but each one uses a different pin-out.
Oh, well, at least commutation and incremental encoder signals are pretty standard: three signals, either RS-422 differential or single ended (TTL or open collector) –Â except if you use some Japanese motors (e.g. Panasonic).Â And I’d better leave absolute encoders for another time…I’m not even sure how many “standards” there are for them.
October 8, 2009 3 Comments