what happens if a servo tries to get to position but cant
Almost Common Servo Drive Installation Mistakes According to 200 Engineers
We all make mistakes. Even people who've been working with servo drives for over a decade brand mistakes. I've fifty-fifty seen it happen endless times in our own labs. Heck, I'll admit I've made mistakes while setting up servo drives on a not-zero number of occasions. So it shouldn't come equally a surprise that our customers also encounter trouble in one case in a while and ask for assistance.
To make your next servo drive installation easier we asked over 200 motion command engineers what are the virtually common issues users accept when installing servo drives. Hither are the top four areas where things tin become wrong.
- Not Reading the Datasheets and Hardware Manuals
- Wiring
- Configuration
- Arrangement Troubles
Each datasheet contains vital information, such as pin functions.
Not Reading the Datasheets and Hardware Manuals
This seems obvious, but 30% of our respondents stated their most common issue was customers simply non reading through the datasheets and hardware manuals. Not skillful.
In that location are many specific wiring and configuration errors that can result from not reading the instructional materials, and nosotros'll explore those in more item later, only permit this be a general piece of advice:
PLEASE READ THE MATERIALS WE Give YOU.
You lot can notice each product's datasheet and advisable hardware manuals on its product particular folio.
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Wiring
55% of respondents cited problems that fall nether the broad umbrella of wiring. Wiring mistakes are incredibly common and often result in the system malfunctioning or not running at all. A simple wiring error can exist the catalyst that pushes an engineer to the edge of their sanity.
Missed Connections
Some instances of wiring fault are procedural. A customer might not see that they need to hook up a separate power supply for drives that require divide logic power, or they might not pull inhibit pins to ground on drives with inverted inhibit logic.
Situations like these can exist avoided by, again, reviewing the datasheet and hardware transmission.
"Sanity check the basics. Logic power (if needed) and wiring. Check that power is being applied. You lot may feel dizzy, but you volition feel even more airheaded if you spend an hour banging your head against the wall then come dorsum to check the basics, and it was in fact a bones upshot."
- Nash Dingman, Advanced Motility Controls
But sometimes you follow all the steps and something still isn't working. It'southward possible y'all mixed up two wires or miscounted on the pin lath. These types of wiring mistakes can exist especially frustrating because finding where you went wrong can be difficult. If you've double-checked the hardware manual, triple-checked the datasheet, and banged your head on your desk for at least 7 minutes, it might be time to bring in another gear up of eyes to look at your setup.
"Take somebody else checking wiring for you, sometimes it is hard to catch our own wiring mistakes."
- Nicolas Cantin, Electromate
Bad Connections
Nosotros discussed missed connections, simply what well-nigh connections that just aren't done well? This tin be something as simple equally a poorly crimped pivot, untightened connector screw, or anything else that results in a poor or failed electrical connection. About 20% of our respondents said that loose connections were amidst the almost common sources of error they've encountered with customers.
I ran into this trouble with one of our brawl toss units. We have a really cool middle-catching demo where we toss a 1 inch ball bearing through a spinning ring so catch it (you can check it out in the video). At a merchandise show ane of the linear motors started to overshoot its position and slam against the frame. The problem was intermittent and totally unpredictable, it would piece of work for a few minutes then SLAM! It would crash. Not but frustrating for the states, but totally embarrassing.
We couldn't figure out what was going on and so we shut downward the demo and took it back to the function.
We concluded up trigger-happy the affair apart trying to find out why this was happening. We tried adjusting the encoder resolution, nosotros tried adjusting the electric current limits, nosotros tried for weeks to fix the trouble. It turned out the motor stage cables were just connected too loosely. A few screw turns on a Phoenix connector would have saved the states weeks of stress.
"I'll be right back; I demand to go scream and cry in my office for a few minutes."
- me
The moral of this story, fifty-fifty if everything looks expert at a glance, give all your cable connections a lite tug to make sure they're all secure. If your system is working sometimes just not all the time, there's a good take chances you have a loose wire.
Wrong Motor Phasing
Be sure to check all 6 combinations for the motor phases (wite, brown, and blue cables in this case).
Speaking of motor phases, make sure y'all have your motor phase cables plugged in in the correct order when using a three-phase servo motor, because yes, that's really important. Using the wrong motor stage combination tin issue in the motor performing with low torque or even not running at all.
With an analog drive, y'all will have to manually check each of the six combinations to brand sure you notice the one that works all-time.
And yeah, check all 6. I don't care if y'all think you found it on the 3rd try, check all 6. There's often a combination that appears to piece of work decently but isn't the best. Bank check. All. Vi.
For digital drives, the task is a bit easier. You can just apply DriveWare or ACE's stage detect for the first time setup.
Poor EMC Practices
Some other type of wiring problem that is often overlooked is poor EMC (electromagnetic compatibility) practices. Poor EMC practices aren't probable to forbid a system from running, just they tin result in EMI (electromagnetic interference), as well known as electric noise, that hinders performance.
There are lots of steps to exist taken to reduce EMI, but our respondents cited these as ones that customers often forget.
- Positive and negative leads of the same circuit should be run wrapped in twisted pairs and so that they reduce electromagnetic fields by canceling each other out.
- Your drive and unabridged electric system should be properly grounded.
- Your communication cables should be shielded for most of their length.
You can find additional practices for reducing EMI that you tin follow in the video below.
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Configuration
Installing a servo drive isn't similar adding RAM or a new graphics card in a PC. Servo drives need to be configured to your system in order to work correctly, and many people don't realize this.
"They expect to pull them out of the box, plug them in, and take them work in their application. We all know that this isn't applied or possible"
- Jim Meek, Automation Support Group
1/3 of respondents cited problems that autumn nether the category of configuration.
Bad Tuning
Velocity loop tuning in DriveWare using digital scope.
At least 99% of the time, the default gains of a digital servo drive aren't going to be what your organisation needs because every arrangement has different inertial properties and torque/velocity/position requirements.
At the very minimum, a servo drive needs to be current loop tuned in society to get move in your organization. For digital drive current loop tuning is a necessary step before performing Motorcar-Commutation in DriveWare or ACE. Don't just assign random gains either; employ a scope as outlined in the quick start guide (once over again, read the instructional materials delight), and piece of work methodically.
On the flip-side, you also don't want to over-tune your drive. Tuning the current loop too aggressively tin overwork your arrangement and cause excess audible dissonance.
Don't try to tune the loops out of order either. Always melody the electric current loop start, and so the velocity loop, and so the position loop.
Not Running AutoComm
I just mentioned that many users attempt to run AutoComm (Motorcar-Exchange) before they tune the electric current loop, but what's arguably worse is not running AutoComm at all. If your drive is poorly commutated, you're going to take a bad fourth dimension, and you're rarely going to do a meliorate job manually commutating than y'all would with AutoComm.
If yous're using a digital bulldoze, please use AutoComm in ACE or DriveWare afterwards you lot've tuned the current loop. Information technology will make your life a lot easier, I promise.
Wrong Motor Parameters
Make sure your motor parameters are correct in DriveWare or ACE
For digital drives, don't forget to enter the correct motor parameters into the configuration file in DriveWare or ACE.
Some motors volition be recognized by the bulldoze and the parameters will be filled in automatically, only it'southward yet of import to double check and brand everything is right.
This includes making sure you're using the correct encoder resolution, especially if the motor is not using the encoder information technology came with.
Motor manufacturers typically brand the datasheets for their motors available online. These datasheets should contain all the correct motor parameters. Large surprise, we suggest reading them.
Organization Troubles
A servo bulldoze can merely piece of work besides as the system it's in. The bulldoze might be connected and powered up properly, but it'southward non going to you lot much skillful if your system isn't ready for it.
Motor and Drive Mismatch
You lot don't use an RC auto to tow a bus and you don't utilise a jet engine to blow out birthday candles. Servo drives should be sized (in terms of power) appropriately with the motor they are driving.
"As the boundaries of motility control take shifted from a centralized approach (smart controller and dumb amplifiers) to a more than decentralized approach where motion planning and tuning is taking place on the drive, more attention is needed on the sizing. Good knowledge of the load, inertia, and planned trajectories is necessary to make certain that the bulldoze has the bandwidth to control and settle the load as needed. "
- Brian Prescott, Motion Control Products
This 1 should be obvious, only nosotros see instances of customers trying to purchase or run drives that are significantly underpowered for their applications. If your drive isn't rated to output enough power, you're not going to achieve the desired torque or speed requirements.
The issues with using an overpowered drive are less obvious, but still problematic. Trying to run a depression power motor with a high power drive is not only a big waste of money, simply information technology'south hard too.
Imagine you're running a 150 amp servo drive at 4 amps, you're going to accept difficulty getting precise control, especially if y'all're using an analog controller. The slightest modify of input control will stand for to a dramatic alter of output.
Motors have electric current and voltage ratings that should be compatible with those of the selected servo drives. Too footling power and you won't be able to go the motor moving. Too much power, and you'll burn down the motor out.
For more than advice on picking the correct servo drive for your motor, read our 5 Rules of Thumb When Selecting a Servo Bulldoze.
Your bulldoze needs to be powerful enough for the motor in your application
You also don't want a servo bulldoze that's incredibly overpowered for your motor.
Non Enough Inductance
If your motor does not meet the minimum inductance requirement, wiring inductors to the motor phases becomes necessary.
Contrary to common belief, inductance is not the enemy. Some people will brag to the states that they got their inductance down to almost zero and nosotros hiss through our teeth considering that'south not what the goal should be. In fact, most servo drives take a minimum inductance requirement.
If the motor inductance is too low, the current loop becomes unstable and difficult to control. The response will oscillate and cause the motor to overheat. If your motor or arrangement needs more than inductance, you may demand to add inductors to the motor stage cables.
Compare the motor inductance on the motor datasheet with the minimum load inductance on the servo drive datasheet and make sure they're uniform. If you take a selection between two motors try to favor the one that meets the minimum load inductance requirement, otherwise you may need to add together additional inductors to the low-inductance motor. This increases weight, takes up room and increases cost.
That all said, you lot don't desire to over-do the inductance either, as this can cause the current loop to be sluggish.
Attain out to our tech support if you have concerns then we tin evaluate your organization. Electric current loop stability and efficiency is determined by a number of factors including motor inductance, switching frequency and bus voltage.
Trying to do it all at once
Do your initial tuning with the motor disconnected from other linkages.
If you have a complex mechanical system, it's inadvisable to install a servo drive fresh out of the box and attempt to exercise the configuration and tuning with everything connected. Doing information technology this way is not only difficult, it can also be dangerous. You don't want a poorly tuned robot arm to first spinning around uncontrollably.
Instead, disconnect the motor from the rest of the system and run it on its own with the servo bulldoze. Yes you lot will likely accept to re-tune once you connect the motor to the mechanical system once more, but you volition be at a much ameliorate and safer starting indicate. Poor tuning is inconvenient, but information technology's far better than having your whole system in a runaway status or spinning the wrong direction.
Mistakes are going to happen during servo drive configuration, and those mistakes are going to exist much less consequential when your motor is disconnected from the balance of the mechanical organization.
Final Thoughts
Nosotros never want to discourage people from asking questions and seeking help. Here at Advanced Move Controls, we'll ever be here to support you. That's why we have our Support Portal and a technical back up squad available during all operating hours.
That said, we hope this guide will help yous avoid some of these common mistakes the next fourth dimension yous're setting up a servo drive, and perhaps you won't fifty-fifty our help.
If there are three main takeaways from this blog, they should exist the following:
- We're all homo, and fifty-fifty move command experts make mistakes.
- Seriously, for the love of all that is good and decent in this world, read the #$!&ing datasheets and hardware manuals!
Look, we get it. Manuals aren't exactly riveting to read, but come on, nosotros don't make them for our own enjoyment.
The hardware manuals give you installation instructions for different servo bulldoze groups, while the datasheets requite the pinouts, switch settings, and other cardinal information for individual drive models. Together, they should provide merely about everything y'all demand to know almost how to get your bulldoze wired into your system.
We make them available to you for a reason, and we've spent a lot of time working on them to make them as helpful equally possible. Information technology volition brand your setup and installation process much easier, I promise.
Just READ THEM. I Mean Information technology.
- Attain out to our technical support for assistance. They're always happy to help 🙂
by Jackson McKay, Marketing Engineer
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Motion Control Overview
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Programmable I/O
Source: https://www.a-m-c.com/most-common-servo-drive-installation-mistakes-according-to-200-engineers/
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