Peter Nachtwey

http://www.holoborodko.com/pavel/numerical-methods/numerical-derivative/smooth-low-noise-differentiators/ It is critical that the sample intervals be constant. Timers are not very good for this. Interrupts are much better.

The statements above are correct. It depends on the process and it is a calculus problem BUT one doesn't need to know calculus if you know Laplace transforms. Laplace transforms are a way of doing calculus and differential equations using algebra. Basically there are two general type of processes. 1. Type 0 or non-integrating process. These are processes where the process value will return to steady state or ambient if control power is turned off. These are processes like temperature control or speed control. These are usually simpler to control and don't need a derivative gain. 2. Type 1 or integrating processes. These are processes that integrate the control output. Tank level control integrates flow and position control integrates velocity. In theory these processes don't require an integrator but do require a derivative gain. The reality is that these processes are never perfect so an integrator gain is required along with the derivative gain. There is a general rule. There should be one controller gain for every open loop pole in the process. The integrator gains doesn't count because it comes with its own pole. I know I just lost everyone with this statement but it is true and if you want know the truth before you die you should look into this. ( add it to your bucket list ). If you want to learn more you should look up topics such a pole placement or lambda tuning. I deal with calculus and differential equations just about every day so the math is no strain on my brain.

ST has a built in FB called F_TRIG and R_TRIG. You must instantiate an instances of F_TRIG or R_TRIG for every one shot.

This was my first motion control application back in 1983. I had to slow the upstream lug chain down for one lug to make space for a cut into. Doing two or more cut in two in a row should be a problem. See this. http://deltamotion.com/peter/Videos/Phasing.mp4 My back ground is the saw mill industry. I worked for Applied Theory which is now part of USNR.

We play table tennis. I have this just outside my office. http://deltamotion.com/peter/TableTennis/NewgyStorage.JPG That is a TT robot in the fore ground. We are good enough that we actually use all that space. I play about 10 hours a week. That keeps the lbs off.

This usually happens when you divide by zero. This error can also happen when one divides a 32 bit number by a 16 bit number but the result won't fit into a 16 bit number. Then these errors occur an interrupt occurs where the designer either puts in a good error handler or simply reports the problem.

I would use sliding mode control. Sliding Mode Control is good for those applications where the control mechanism is a simple on off device. You really shouldn't need a PID. Just turn on and off the valve depending whether you are above or below the target. The sliding mode control simply adds a rate control or prediction feature to the simple on off technique. This prediction technique would keep the rate from dropping too fast a the beginning.

The PLC can communicate with the motion controller fast enough to do most things. Usually the motion controller does all the motion control and the PLC simply issues commands or tells the motion controller when to execute user programs in the RMC motion controller. The motion controller has 64 MB of ram which is more than the PLC has. There are examples here: http://www.deltamotion.com/dloads/downloads.php?category=rmc100&subcategory=Examples

Our RMC100 has a stepper output module. It can generate sinusoidal motion profiles as well as point to point moves with s-curves. I think it would be better to stick with analog control. Then there are more options.

We have a motion controller that can generate sine waves and we have a stepper motor output. See the step and direction, QST, module. http://www.deltamotion.com/products/motion/rmc100/

From what Bob says it isn't that simple. The water must heat the surrounding metal too.

The designers should be fired. I see to many systems that are designed without a thought as to how they are going to be controlled. Sure they can be controlled but all the extra effort often cost more than simply designing the system right in the first place.

It looks like a few of us have come up with the same bias idea. I don't see why the temperature isn't exact almost immediately if there is no water in the vessel to start with.

I am always watching. I would bias the PID with an offset of 100*(120-70)/(140-70)% control output. It can be even more accurate if you know the exact hot and tepid temperatures. I chose 70 as the average tepid temperature and 140 as the average hot temperature. You should be able to get by with just a P gain but using the integrator will help make the time constant precise. If you want the to get with 1% of 120 degrees in 120 seconds the integrator time constant must be about 24 seconds. An exponential process will get with 1% in 5 time constants and 5 times 24 = 120 seconds. It would be good to know what you are using for your gains. Do you understand how I calculated the bias?

You really should get a M02AE and an encoder that provides MUCH higher resolution. What you have will not work unless your positioning requirements are very lax.

I think your opinion is right on. We use LabView for our automated test rigs that test all our boards. LabView works well for that but it I can't see it being used in controls.

<br>I will keep my Skype on.<div>Lets hear about your project.</div><div><br><br><br><br></div>

What you whan is impossible with what you have. You need to use a filter to compute a relatively accurate speed but it will not have an instant response. If you are controlling the cylinder there are more options and algorithms available. If you really want to know the speed you should get a hydraulic motion controller. A hydraulic motion controller can update the actual speed every millisecond or faster. Think about this. How, can one control the velocity if the velocity isn't known? The same thing goes for position. The motion controller must be able to control the speed between positions. A good hydraulic motion controller can control the position, velocity and acceleration. The problem is that a hydraulic motion controller will cost a lot more than a S7-1200 but you get what you pay for. A more direct question is .... What is the application and what are you really trying to do? Did you know there are forums dedicated to simply calculating the velocity from positions? Here is one. http://www.holoborodko.com/pavel/numerical-methods/numerical-derivative/lanczos-low-noise-differentiators/ and another http://www.holoborodko.com/pavel/numerical-methods/numerical-derivative/smooth-low-noise-differentiators/ The Savitsky-Golay filters are a good place to start but they will not stop instantly. Pavel was innovative and came up with his smooth robust differentiators. The smooth noise robust differentiators will not stop instantly.

I didn't know that I was being videoed when that happened but I though it was good and honest so I kept it and posted it. Yes, I will always be sore because we have wasted to much effort support Siemens S7 when the Siemens people should be doing it. Look at the number of S7 questions about simple stuff that should be a given. Look at this thread. http://www.plctalk.net/qanda/showthread.php?t=65652 One must know that the parameters are copied to the stack before the call and then AR1 is pointing to the variables on the stack. One can find the address of the parameters ON THE STACK but not where they actually are in memory. So why all the posts on this thread? Doesn't anybody know how a S7 works? Obviously not from the responses I see. The bigger question is why does AlecTek need to know the address of the word or integer? Look at plcs.net right now. See how many S7 related posts there are relative to the other PLCs. Look at how many posts are about how to do this or that with the S7 and not how to get the job done. I can understand if the questions were application question but no, they are question about how to make the PLC do something. The first time we got an S7 to talk to a RMC over Profibus it took 4 hours for a Siemens engineer to figure out how to do it and that is with help from Johnson City. There is nothing to configure in the RMC. Many of my S7 customers can't program very well in STL. I have had to write a fair amount of the communications code between the S7 and the our motion controller. If the code is on the S7 then Siemens should be helping the customers with writing the communication code and not us. If Siemens had a decent MSG block it would be so easy but NOOOOOO. I have spent way too much time supporting Siemens PLCs. This isn't an opinion. It is a fact. I monitor the main PLC forums. Have any of you seen long threads about our product? NO and why not? Because I think it is a major embarrassment to have a lot of questions about a product especially when it is the same questions over and over and over and over again. When the same questions get asked over and over and over and over again it is a sign of a poor product design or poor documentation. BTW, our motion controller can bridge between AB and Siemens. Oh did I mention Omron, Modbus/TCP and Mitsubishi too and I may have left out a few. What we have notice is that Omron and Modicon are/have embraced Etherenet/IP.

AB > Siemens With AB you spend more time trying to solve the problem. With Siemens you spend more time just learning how to use the S7 than solve the probelm Left over mental energy can then be use to solve the problem.

There are more issues than just sprockets. The sampling must be done a regular intervals to get accurate speeds to gear to. You should have turned the press roll with the encoder by hand without any wood under it to see how smooth and accurate the encoder is under ideal conditions. A low pass filter could smooth out the speed fluctuations. A similar application is done with our controller all the time in saw mills. It is called curve or shape sawing where the wood is scanned and the cam table/curve/spline is downloaded on-the-fly for each board after being scanned and the best cutting solution determined. http://www.deltamotion.com/peter/Videos/JAN-04%20VSS_0001.wmv I was out last week at a wood show in Atlanta.

What is the resolution of the encoder? Each count represents how much distance? The y scale on the left shows 1s up along the left side. I would plot the position too and get several plots so they can be compared side by side. If the encoder is slipping you should see spikes like that but rather dips when the encoder isn't moving. This should be easy.

If the cam profiles only need to be displayed then why not take a screen snap shot of the profile while in the editor and save the jpg file. Then display the jpg file. Hopefully the PV can display a jpg file.

I don't understand this. People will but 10 times more effort into working with an product that isn't suitable for the job. This is like saying you can only use a screw driver and a crescent wrench in your shop. This is a difficult project even with a G06. There are things going on that are hidden from the user in the Rockwell cam editor. The linear or constant speed sections and adjusting both the velocity and acceleration at the end point is an advanced feature where the cam editor inserts extra points to make the linear and constant speed sections happen. If you need these features then prepared to do a lot of math figuring it out. It isn't trivial. How much math can a PanelView do?

If the motion is the limiting factor then definitely yes. The motion I see in your video is slow. If your machine sells for 1,000,000 and we can make it 5% faster it is now worth 1,050,000. If it cost $20,000 to increase the value by $50,000 then that is a good deal. Also, many places will not have the room for two slower machines so one faster machine is the way to go. See this: 6 DOF motion platform with weights This platform was used in the making of the movie 2012. It is controlled with our controller. Our controller is also used in flight simulators.