Arduino & ClearPath Servo: Moving 34 lbs FAST! WW131
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- Опубліковано 30 січ 2017
- These ClearPath Servo's are amazing. Using an Arduino and ClearPath's free diagnostic software, we get the motor lifting 34 lbs VERTICALLY at over 800 inches per minute!!
2-4-6 Blocks: amzn.to/2jMDo7p
Filmed With: amzn.to/2kkMBVH
and amzn.to/2kLE5Q7
MSP Software: bit.ly/2kahERs
ClearPath Servo: bit.ly/2kkVRGO
Our First ClearPath Video: bit.ly/2jCbJHV
Thanks to www.bell-everman.com/ for the Linear Stage!
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Music copyrighted by John Saunders 5 Reasons to Use a Fixture Plate on Your CNC Machine: bit.ly/3sNA4uH - Наука та технологія
hey John,this is by far the most amazing motor i have ever seen,nice videos bud keep it up,thanks for all the time you put into them 👍
Big, BIG ups on this video! I've wanted to do automation for a while in my shop, but it always seems so impossible and so far off into the future. It's great to see someone who is willing to take the time to mess around with these things and who cares about leading his and other small machine shops into the new age of manufacturing.
I'm unbelievably glad I clicked this video. I've been looking for weeks for a servo (not stepper) which runs ~5k rpm and makes a few lb-ft of torque. Fantastic!
looks like you and AvE are down the same rabbit hole... enjoy!
dude I loved that test to prove the overshot! brilliant!
this video make my purchase decision for me. i have been on the fence for clearpath for awhile but lack of creditable reviews made me hesitate. John your review and detailed video of these motors makes it a no brainer. thanks for the information!
Love that you are getting back to steppers, ardiuno and more automation. More please!!!!
Dang, that's really cool ;) I'm just starting to grasp why you're so excited, very fun stuff you're getting into there! Can't wait to see more!
Im really glad your planning more videos with Arduino etc. one of the very first videos (and what actually got me interested in your channel) was your earlier arduino videos :)
I bought three of the CPM-SDSK-2321S-ELN Clearpath for my project mill. I turned the motors using the software and absolutely love them. When the table is moving, you don't hear the motors at all. Very strange for someone who is used to the noise steppers make.They are worth the extra $$$ in my opinion! Great video John!
Great video. It has been 4 years science the video was produced but it is still a great example of the ClearPath Servo's products.
Power is given by this formula, P=F*v which resulted in, 55.6W (.0746HP), or the power to move 34 lbs vertically at a constant 867 IPM. This does not take into account mechanical loss such as the friction of the bearing surfaces and air resistance, or the electrical loss from the resistance of the windings in the motor. Mechanical energy is denoted by these formulas, Ke=.5mV^2 and Pe=mgh based on the kinetic energy given alone, it produces 1.04 J(0.767 fl-lbs) of energy. Potential energy is a little harder to determine due to the lack of height provided. Assuming a height of 4 inches, the potential energy is 15.3 J (11.3fl-lbs). With the assumption, the total energy of the 34 lb mass moving vertically at a constant rate of 867 IPM and a height of 4 inches is 16.3J (12.0 fl lbs).
A hundred thumbs up. I can't wait to see what's next. There is so much great free software out there. Thanks and keep it up.
Super video, what a fantastic product. Will be adding them to my CNC machine, your a brilliant salesman. Keep the great videos coming.
Awesome channel NYC CNC, been watching for years.
I can't wait for more video on clearpath. I have a cpm series motor and it's pretty incredible what it can do.
I LOVE these kinds of videos. I am currently overfilling a 3d printer with servos and like some good educational videos keep it up
Looks like these have a lot of capabilities. Thanks for sharing all the great info with us, the built in metering with the o-scope is awesome. This has me thinking about maybe building my own plasma table in the future as they clearly are a valuable tool to a job shop. I liked the chamfered lead in on the feeder too. :-)
Seriously cool! I was sitting here grinning from ear to ear watching that weight move up and down.
As for what the motor is developing, let's take the steady speed of 867 ipm. A horsepower (imperial - metric is a tiny bit less)) is defined as 33,000 ft-lb/min.
Your rig is developing 867 ipm x 34 lb = 29,478 (we're ignoring the weight of the carriage, friction, and maybe some other additions to the load) so let's round to 30,000 inch-pounds per minute.
Divide by 12 to get ft-lbs/min = 2,500
Divide by 33,000 to get hp = 0.076 hp (rounded) or roughly 1/13 hp which passes a reality check by looking at the size of the motor and thinking about other small fractional hp motors we have seen.
The answer should probably be a bit more since I'm sure the carriage and the bolts must weigh at least a pound or two, and there is the friction (efficiency) of the ball-screw, bearings, slides, etc. to be considered. Like hot-rodders, maybe we can consider "rear-wheel hp" and ignore all the drivetrain losses and consider the steady hp it takes to lift your 34 pound payload at that speed as 1/13 hp.
An interesting thing to consider: that trapezoidal speed profile requires some jerky changes of acceleration and deceleration. If the ramps were started and finished with hyperboloid curves rather than sharp corners there would be less tendency to overshoot (those errors on the green trace) and the instantaneous hp required would be smoothed out. It might be possible to actually shorten the time of those ramps with no increase in required hp or torque. (Now it just may be that ClearPath actually does exactly that "behind the scenes" and trying to outguess the software would be futile. You might ask the ClearPath engineers about that. If it's a stupid question, you can always blame one of your viewers.)
Nice Work the ClearPath servo's look awesome!
Big fan of the Arduino :)
Blows my mind :-) I love Servos... All of the Robots I have worked with have had servos... I really can't see myself using Steppers over Servos, for the reasons you stated. Enjoy!
Very cool stuff! Looking forward to more.
some seriously good content these days, thanks!
Our big plasma machines weigh thousands of pounds, travel 30' in X and 12' in Y, and the motors fit in a large shoebox. You are correct: it is amazing.
0.26 funny how the microphone hisses when you touch the motor
@Morgan Pablo yeah let me guess someone tried it for 20 minutes and it worked perfectly??
@Morgan Pablo ooh you changed it to 10 minutes lmao
Awesome. HUGE Thanks for sharing!
Great video! I think I see a ClearPath inspired SMW retrofit kit for the Tormach coming soon to your web site. Hahaha!
Clear Path has done an awesome job of incorporating a lot of engineering for us into their controller. When designing a servo control closed loop system, you have to take into account all potential errors, including lags in the system. Looks like their auto tune is detecting all of the errors in the system and then adjusting the system to compensate for them. And, (saying this with tongue in cheek) all those pesky gains are important to old control engineers like me! :)
Thanks mchiodox69. Tuning the "pesky gains" can be a double-edged sword to a user with limited experience. Used appropriately, they provide superior performance. There is a detailed response about the auto-tuner listed under the post for snikkeldak that you may find interesting.
I hope this is a prelude to a DIY CNC plasma table. Another great video John, even though most of it was over my head.
This is awesome!
Those look very nice. What do you think of adapting those to your Tormach machines. I love your channel!
I'm impressed !
I like the feedback when you touch the motor.
Awesome video!! I didn't know about the advanced page you showed when I set mine up. I just did the auto tune and they are truly awesome motors.
You are a true inspiration to a lot of guys wanting to get into machining and cnc work. I probably would have never converted mine over to cnc if it wasn't for all the videos and help that you get out to us with your videos. THANKS SO MUCH.
The Clearpath do seem like a good value. You're right, servo tuning can be a biotch to tune and is dependent on what it is pushing and pulling and like in your case the axis of gravity. Very good demo and I am really impressed with the diagnostic software. A servo and a gecko drive is going to cost in the same price point so getting rid of some wires and adding diagnostics makes Clearpath the better choice. I'll be using them on my next build for sure.
Thanks Colin MacKenzie. We look forward to working with you. Some details about the auto-tuner can be found under the post for snikkeldak.
I first tried out the Clearpath SD-series motors within 6 months of their initial release onto the market. Very shortly into that first application I vowed to NEVER use a stepper motor again. I've also incorporated their MC-series motors for a couple of builds, and in a simple, single-actuator PLC-type application these are KILLER!
My only fear is that demand for these could possibility exceed Teknic's ability to produce, and I might end up waiting longer for delivery....
now the here is, are these motors the next level performance for the Tormach? They also say you can replace spindle motors with there larger ones?
Hi John, when my mach 3 system finally gave out or I got sick of fighting with it I went to WinCNC and got a proper controler from them have a look. A system that does not glitch out on you when you plug in a usb. They make systems for a lot of very big company's that build cnc routers in the US. Have had no problems in over a year.
Love your Vizsla ... oh, and the videos ...
Great video! Just switching on some CP's on my own CNC project. Just curious, what is the max rated rpm for the motor you're using (or its model number)?
Did anyone else notice that it looked like he had Abom's "Do you even indicate bro?" shirt on? Very cool haha
I can't wait! I already am picturing an awesome CNC machine to be built. Currently, I've built a shapeoko 1 and a shapeoko 3, but an no machinist. This looks like it would be a huge upgrade. Would this work with grbl 1.1?
Have you heard of closed-loop steppers?
might be worth to take a look at
Hey John ! your test is crazy ! for such a small motor! i'm impressed
I'm designing a cnc and it coud be a great choice. Does this closed loop motor could work with a granit ioni ? or mesa card ?
Hi John I need a small suggestion for my b-tech project based on machining
and at last I am great fan of your videos
Power = Force * Distance / Time so 34 lb * 70 ft / 1 min = 2380 lbft/min which is a hair over 50 watts. With losses in friction and high performance braking to hold a position and dampen the motion, with additional understandings of acceleration requirements (much more power necessary) AND the fact that motors have an approximate parabola power curve vs speed. This is why steppers are so frequently undersized by amateurs. Peak torque is usually at zero velocity but peak power doesn't happen until about half no-load speed! Keeping this in mind, the inertial loads (heavy weight or very fast accelerations) are what tax the servo drives more than the constant velocity. It's all in the accelerations, hence that peak torque beeping you were hearing just after an acceleration from near zero velocity.
Fun indeed. :) Keep up the great content.
I want a pair of these for my lathe. So quiet!
JMC servos are pretty awesome too. At first glance you might think they are a stepper and they do have a model near identical looking that is a stepper (plus clones exist) but it’s an AC servo powered by DC step/direct that uses a internal vector drive to convert to AC. They are fast as heck and ultra quiet. JMC also has programming software for the servos so you can set them up much like you do with clearpath and they’re half the cost. JMC has all sorts of products from steppers to servos and I’ve seen up to 3kw 19nm beasts. The Nema 23 model number for their servo is IHSV57 and for the stepper it is IHSS57. Keep in mind everyone is copying them and the clones cannot be debugged or programmed like clear path. You will find some sellers overseas that will fool you to get a sale. They even sell the clones for more money.
Real impressive!! Can you tell me where i can buy the cnc slide rail like you use in the video? or the brand that you used?
is it the strong (CPM-SDSK-2310S-RLN) or the normal version (CPM-SDSK-2310P-RLN)?
I finished watching video and saw the part number. Answered my question.
Very nice video,
CNC milling machine leaves a marks on part surface when the tool travels from a high to low point and start machining immediately , you can see kind of ripples on surface and they disappear as the tool moves further because of the tool vibration is damped, so tool bouncing is more likely to occur when moving down. I think it would be more convenient if you perform the test on the down side because the weight of blocks will contribute in the overshoot, and will prevent it while moving up . What do you think ?
Thanks
I think you'd probably get the same result. It would simply come to a stop more slowly as it accounted for the load. These are very smart drives. They do the calculations for ramp up and ramp down before they even move, and are able to determine when they have to start slowing down in order to prevent overshoot.
Nice video! Can you recommend an alternative for these motors for under $100?
Incredible! I wonder how the X2 minimill would perform with those servos.
Are you still wondering moron?
Remove one or two of the blocks and have them suspended in the path of the attached blocks. Then monitor the position error as motor picks up and releases the free blocks as it moves up/down.
The test you're doing is almost set up for it to do well, you're tuning it for a fixed set of conditions - then only using it in those conditions.
Thank you for your suggestion. Maybe John will do another video showing such a test. What you would see in such a test is a blip in the tracking accuracy whenever the weight was instantaneously changed (i.e. when a block was picked up and when a block was released). The magnitude of the blip would depend on how extreme the test was (i.e. how fast and how much difference in weight), but in any case, the motor would quickly compensate for this error and be able to adapt for the change in weight. (Comment continues)
In real-world applications, many axes do not have well-balanced, non-variable loads. Most CNC applications do not have a consistent load weight and/or cutting forces throughout operation. This is why ClearPath has Variable Load and Inertia Matching Technology. This technology allows for high inertial mismatch and also allows for variable load weights and forces (within reason) with virtually no change in performance. In order for this technology to work optimally, we recommend that the motors are tuned for worst case scenarios (heaviest load weights and forces, and highest inertia mismatches).
As the reply from @Teknic Inc was not made public here it is:
Thank you for your suggestion. Maybe John will do another video showing such a test. What you would see in such a test is a blip in the tracking accuracy whenever the weight was instantaneously changed (i.e. when a block was picked up and when a block was released). The magnitude of the blip would depend on how extreme the test was (i.e. how fast and how much difference in weight), but in any case, the motor would quickly compensate for this error and be able to adapt for the change in weight.
John, I really think you would dig taking a high level Mechanical Engineering course in Control Systems. It would make you appreciate that Auto Tune feature real quick haha. You have a very natural understanding of all the fundamentals and It's great to learn from you. Like you said, not getting overwhelmed is key. Very cool video, I'm working on a project at work and I may go a similar route for the automation of a fairly heavy arm assembly.
John, how did you do in Calculus and Diff EQ's in school? If it wasn't for you I'd avoid a high level controls class (I have a BSME and the math was killer)
Ted Saylor hahaha so true, that was the most math I think I've ever used in my life. Brutal honestly, but when you finally get to the end and have the "aha moment" it's all worth it.
Well it does get quite messy.
One of the things that I realized much too late is that mathematics is a special language to describe abstract concepts. Like any other language, it takes a long time to learn to think in that language; and then to move onto the different dialects. There isn't enough time to acquire a language as part of a 4-year course that deals with a thousand other things, if one isn't gifted/cursed.
Believe it or not; I found a use for second order, partial differential equations in the real world. (I was dong static footing design because the senior Civil Engineer's brain had exploded.) Well; I reduced the solution space down to exactly one; which was solved for particular cases by numerical methods.
30 years later; not sure that I could replicate the work from scratch without half a year to "warm up".
Bernd Felsche yeah, even though I've been through all the math of PID and could probably still get it done with a little brushing up, I'm thankful for companies like clearpath that make it easy to get the job done. That's what sets a company apart.
It appears that it self calibrates all the parameters of the PID feedback loop. awsome
Thanks dirkblanston. The ClearPath actually uses PIV control and not PID. Details can be found under the post for snikkeldak.
Could you show us how you check a machine for tram/squareness and how you would correct it if it's not within spec?
Closed loop stepper. They have a 2000 line encoder and are super easy to set up. Just adjust your speeds until you miss steps and back it off a bit and your done. They are about 130-150 for stepper and driver for a 1600 ozin nema 34 system. Much cheaper then the clear path.
Kinetic energy = 1/2 times mass times velocity squared.
I am working on a piece of art that needs to move 2 things. The first load is tiny and speed mostly slow. The second load needs a fair amount of torque and slow speed. Now I am constantly considering weather I should go for servos or steppers. Any thoughts? So far I only worked with steppers on my CNC and printer and servos on RC planes.
NYC CNC Yeah that looks like a nice motor but I need something for a tenth of the price.
Max Maker look into mechaduino. its a board that you put on the back of a stepper that turns it into a servo. They are not very expensive.
Steppers have high low speed torque but it is very jerky. Microstepping helps, but there are a lot of factors. you might look into getting a stepper with a gearbox.
Look for motors with a high rated voltage, like 24v. They will take more power(with a higher supply voltage) than a low voltage motor at the same current. I have also found the TI DRV8825 based driver modules to be the smoothest, in 32x mode.
The reality with motion control is you pay for torque and power, unfortunately. Even a big NEMA 34 stepper and appropriate driver will cost as much as a small clearpath.
Max Maker the other question to ask yourself is do you NEED computerized motion control? You might just be able to use a DC gear motor and a cheap speed controller. If it needs to move between multiple positions you could use micro switches and an Arduino to sense when the mechanism is in position and turn the motor on and off.
shop dog is super cute. We love our Teknic motors for our simulator motion system. :-)
What is the part number for the servo? It is really great showing us lifting at the weight you did. My spindle motor alone is 12 lbs and I am figuring another 10lbs+ for fixturing and other gizmos. awesome video.
heh heh heh, that high frequency ground loop
Can a servo like this be used to control windows (occasional use) and wipers (constant use) with proper venting and weather-proofing?
Is there a smaller model of ClearPath servos that you can recommend similar to the one used in the video?
Nice video. Which ClearPath servo did you use? Is it SCSK series?
I don't get it, but why is this test done with rubber coupling? doesn't rubber contribute to the movement error?
Clearpath is the best thing that has happened to my laser cutting business. Now that said the auto tuning does not take them to their fullest potential, I got 3x better settling times by manually tuning.
NYC CNC indeed, a laser cutter needs extremely high performance as I primarily cut paper with fast speeds and acceleration, minor errors are easily reflected in your final product, I need my servos to be with in an error of 5 counts or less. the auto tuning gave me something like 25 error counts on the initial overshoot and the move settled in around 100 ms, manually tuning them I was able to keep my initial overshoot with in 5 counts and have the rest of the motion oscillating within 1 or 2 counts with accelerations of 4600 mm/s^2 which to me is just fantastic
Abraham Saenz, I am glad to hear that the ClearPath is working well for you. There is a more detailed response about the auto-tuner (and your situation) under the post for snikkeldak that you may find informative.
Teknic Inc Thank you, your product is truly remarkable, this product really blows yaskawa, Panasonic and others out of the water for CNC applications, they may have a lot of advanced features but most are useless for CNC, on top of that your product is much sliker, smaller, lighter, easier to use and on top of all that cheaper. The more I learn about servos the more I realize how great the Clearpath's are.
Could you please mention the brand of slide? I did not recognise it when you said it.
0:25 John picks up a ton of electrical interference just touching the powered servo motor, can be heard on the microphone.
That's the kind of video I like.
What does the inertia ratio look like between the load and servo and will that cause any problems? Does not seem to, but I'm just wondering.
How do you determine proper motor needed?
You are going to win with the servo. Steppers lose lots of torque the higher the step resolution, you don't lose a thing until rpm breaks the torque curve downwards with the servo. Awesome tests! How did you calibrate the travel distance to the ClearPath before you started? What voltage to the servo?
the motor use the normal endstop connected to the board?
There is a fundamental difference between servos and steppers, a mechaduino is just a closed loop stepper and will never be a servo. Also, clearpaths have been showing up a ton! They look awsome. Look into jerk control for the energy transfer onto the gage? Keep us posted on your automation projects, thanks.
These look great although as far as I can tell the servol loop is closed at each drive..if the drive starts acting up the cnc control wouldn't know..but still fine for hobby use..
Very interesting subject, I think many of us are either building or planing to build CNC routers and plasma tables. Of course I'd like to be building a robot but I think I'll have to be satisfied with my router :-)
I miss this content
Thank you. I have a bore and insert machine that was ordered with a Z-axis drive. The x-axis drive is servo and very fast and decently accurate. This machine normally has a manual change of the Z-axis because it normally processes panels of a consistent thickness. I wanted to be able to drill & insert at two Z levels and therefor very quickly change elevations. The salesman knew this. But they cheap out, making the Z-axis automation useless. The stepper system always has to return to zero before moving to the new location. Very slow, useless! Watching this video, I'm thinking it may be possible to now convert the machine's Z-axis to the servo like I wanted. I'm not technically bright enough to know what would be required. Machine was made in Germany. The CAD we use is Top Solid. The g-codes are generated in CADCODE. Codes are looked up on the server by using a barcode scanner at the machine.
Has there been any word indicating that Tormach could come out with a series 4? Perhaps using clearpath? does clearpath offer a unit that could be used as a spindle drive? then we could have rigid tapping, no?
What torque and RPM does it make? I'm looking for high power/rpm motors for....various mech projects. (edit) nevermind, I looked at their site! Great torque and greater rpm!!! FINALLY!!! Found a servo that makes the RPM/torque I need. THANK YOU!
Can you provide any guidance on the Aurduino code?
hello what is the clearparth servo model you will use to make a 6feet x 3feet plasma cutter CNC table,or any other motor/controller thank you
have you had problems with over-torquing the motor? I currently have a gear coupled to my motor to drive a belt, but it keeps over torquing.. even if the belt isn't attached to the gear. Have you had similar problems?
You should mention that the servo has a built in encoder and micro processor. So the servo is a close loop system. Way better than a conventional stepper were you can loose step and not know, clearpath will alarm if you loose position.
steppers only loose steps when you specify something to weak for its purpose. You can also get encoded steppers so you r argument is biased and false.
wow, that's great to hear. I have not working knowledge of servos, but I do know I like the built-in feature of those parts.
Do you think this would turn a rotary table with a 200-300 pound load on top of it? Its not lifting the weight vertically, but it has to turn the weight to precise angles.
Great video mate, These clearpath servos look delightful. That calc will depend on the thread of your lead screw, dia, pitch per inch and a rough friction coefficient. Maybe there is a lead screw calc tool around .You could turn faster with more thread pitch and have less torque i'd assume. Obviously turning faster brings its own issues.
One correction: 25 microns (assuming that means micrometers) should be really close to 1 thou, since 25.4mm are an inch, divide both by 1000 and you have the numbers. So it's even more accurate than you think ;)
And another mistake: you shouldn't have divided your result by 10, but multiplied by 10/25.
I have also worked with servo drives and hand tuning them can really be a pain in the ass.
Klaufmann I noticed that little error too. 1 micron = 0.000 001 meter = 0.001 millimeter. 0.001 mm / 25.4 mm/in = 0.000 0393 7 in. x 25 = 0.000 984 25 in. Like you said, 25 microns is very close to 1 thousandth of an inch.
Hey can you write on belt input vs direct input? Here I see you use direct input but somewhere I read its recommended to use belt input. Whats your thought on this topic - belt vs direct? regards
Can anyone tell me if running the 10 lb-ft version of this servo on their site through a 10 to 1 gearset would provide enough torque to meaningfully turn a simple hydraulic pump? Really looking for a solution that can be carried by a person.
Hi John you think this motor will work on a Bridgeport Boss8?
good job im interesting to make my propetly cnc , Greetings from bogota colombia
Do you thing it is possible to mount Clearpath motor from the motor chassis itself?
I know that there are typical 4 screws form nema23 motors, but are there any other mounting possibility outside those?
Just to answer your question at the end (sorry if someone already got it and I missed their reply). The amount of energy for 34lbs at 830in/min is only 0.700ft/lbs..
To calculate energy in Joules, the formula is 1/2 mass * velocity² (which has to be in Metric... KG for mass and Meters per second for velocity).
weight in Lbs / 2.204 will give Kg, so 34lb/2.204=15.426kg
1in/min = .000423m/s, so 830in/min = 0.351m/s
Thus (15.426/2)*.351² = 0.950j of energy
1j (joule) is equal to .7375lb/ft of energy so 0.950j = 0.700lb/ft
I want to get ClearPath servos, but I don't think its possible to set up a closed loom PID dynamic position control algorithm to control it (am I wrong?). I need to set up a robotic system to follw a moving target.
So what does this tuning actually do? Does it matter for low speed stuff?
NYC CNC thanks!
Autotuning is always a quite involved process which sets all parameters of a controller, in this case the motor controller. For such applications like servos you usually use a so called PID controller which is very effective when tuned properly. Every controller tries to eliminate (respectively minimize) the error of your system. The error is difference between your set point (value to reach) and the actual value of the controlled variable (plant output) and may or may not occur due to disturbances in the system (plant). To achieve zero error, you put a controller in front of your plant which manipulate the signal based on the set point and error and your system. Your controller knows the set point, can measure the actual value and therefore calculate the error (= negative feedback loop). Its task now is to control and adapt the actuating signal (plant input) in such a manner so that your plant exactly behaves like you want it to (plant output = set point). The beauvoir of your plant in most cases is described by a so called transfer function, basically mathematical description of reality, but that isn't the point of interest now, so let it be a black box.
Furthermore it is important that the measured value (plant output) is the same type as the set point (plant input).
Now the fun part begins... how does it work?
Well, in case of a PID controller, the controller "consists" of three parts (P, I and D). All parts eventually are added to the plant input u.
P (proportional) takes the value of the error (e) and multiplies it with a specific constant value cp. P is a first rough approach to get in the area of zero error. It's quite accurate if the system doesn't change frequently. e is getting smaller every cycle and finally is zero, or is it?
I (integral) sums up all errors in a certain period of time (lets call the sum i) and multiplies it with a specific constant value ci. The P part often can't handle very little errors sufficient enough because of several reasons. The I part though sums up all those little errors over time and is able to counteract those.
D (derivative) calculates how fast the error changes (lets call the speed of change d) and multiplies it with a specific constant value cd. The D part is crucial in frequently changing systems. By knowing how fast and in which direction the error changes the controller can adjust the plant input to avoid upcoming and growing errors! It can compensate big errors before the even occurred. Pretty cool, right?
As a result: u = e*cp + i*ci + d*cd
u now is fed into the system and the errors hopefully is almost zero. But how near to zero it is, is depending on the constant values (also called gains) in your controller and your system. That's the point where Autotuning kicks in. Every system is different. And there aren't universal values for your controller, you have to find the perfect ones for every single application. But since the change of one controller part effects the behavior of the other controller parts as well, you not only have to adapt those constant values to your system but also to themselves! Every change of any variable will effect the performance of the whole controller. You can imagine: trying to figure out the perfect values of a controller for a application is a very involved process and nearly impossible to do by hand. Well, there are certain approaches that help finding those values by hand, but to find the PERFECT ones for your application, not only good ones by hand.. it's almost impossible. The most efficient way is numerical iteration. But depending on how good your algorithm works, the performance of the whole system is good or bad. That's what Autotuning does. It optimizes the variables of the controller just to fit your application perfectly. Hope that helps!
So yes. It even matters for low speed applications. For instance during high accelerations with heavy loads there is a pretty good chance that your system is hunting (real value is hunting set value, your system reacts slower than it should) if the controller (in this particular case especially the D part) isn't properly tuned.
The controller has to take the signal from the arduino as well as the reading from the position encoder and send some amount of current to the servo motor for some amount of time in order to make the "stage" move to the position specified by the control signal (all the while slightly adjusting the current or time based on continuosly monitoring the encoder)
The "tuning" sets a bunch of parameters that let the controller know how much current and for how long. This will change depending on such factors as the load, the friction, the power of the motor, the pitch of the lead screw (if one is used), etc.
As others have suggested look up PID Control Theory and find an article that walks through P, then PI, then PID or just google for "Control Theory" for deeper explanations (-8
Max Maker, that is a great question. There is a detailed answer listed under the post for snikkeldak.
I'm guessing the scales are really heavy or bolted to the floor
Did you buy this servo for retail price?