PID control to maintain constant heater electrical power?

Hi!
I am looking for a good solution for the following:
I have a heater wire (approx. 220 Ohms). I drive this wire with DC voltage. I measure the voltage drop on the wire, and the current running through it. I want to control not the temperature, but the calculated electrical power (P=U*I) in the range of 1mW to 1W.
Of course the resistivity is slightly different at different temperatures, so that is why I think I need active control.
Maybe someone could give me a good advice?
Thanks very much!

Hi,
Everything is set up for the hardware. I generate the DC voltage with a NI Static waveform card (DAQmx). I measure the voltage drop and the current (via voltage drop measurement on a calibrated resistor connected in serial with the heater wire) with a Keithley DVM via GPIB card. The SetPoint is the required electrical power, the ProcessVariable is the calculated power from the measured U and I. The output is the driving voltage between 0-3 DC Volts, what I amplify with a factor 5.8 with an amplifier connected to the heater wire.
I try to use the PID.vi from the PID toolkit (I already use PI(D) controls from LabView for other heater wires, where I have to control temperature, and they work very efficiently and perfectly) for this purpose.
So far I try to find the proper gain values. My sampling rate is low, approx. 8 seconds. First I tried only the P control (zeroing the I and D gains of the PID.vi), to find a stable oscillation range, so I could go on with the PID Autotune vi. But no luck so far. I think it is also a problem, that this system is not linear: the P is not a linear function of U. Can you suggest how to go on from here?
Thanks very much!

Similar Messages

I need to maintain a temperature profile for my process.Can i use PID control for this application?

Hi all,
I need to maintain a temperature for my process.Can i use PID control vi's for this application?
I have NI-PCI 6023E DAQ board.Should I need any other hardware components???
Any help in this regard is highly appreciated.
Thanks,
radhika

Hi,
Thanks for your reply.
I do have a temperature sensor and it is read by the DAQ (NI 6023E) .
Also i have a voltage input to the program which has to be controlled in order to control the temperature.
So , I am using a PID , the output of the PID should control the Voltage input so that the temperature is controlled.
Can I give the voltage input and the temperature to the PID through the DAQ and just use one more channel in the DAQ to get the output from the PID.Will that work???
I am not sure why you have mentioned SC2345,SCB68.
Thanks,
radhika

Maintain constant current

HI I would like to use NI Daq to produce current output that corresponds to desire magnetic field strength, then I would like to maintain the desired magnetic field strength constant in either magnitude, phase or frequency in a closed loop system.
Could you please let me know if I need to implement a PID control algorithm or any specific control design toolkit in NI LabVIEW for this project?
Thanks

The first half of your first sentence sounds like you want to use LV and DAQ AO to generate a setpoint. The second half sounds like a description of a power source which can generate the necessary current for a magnet to maintain the field at the desired setpoint. It also appears that you wish to be able to select one parameter (magnitude, phase, or frequency) to regulate. Is this an accurate assessment of your statement?
1. It should be relatively easy to generate a signal to use as a setpoint.
2. Unless your magnet is very small, the magnet power source may need to be very specialized. It is unlikely that standard DAQ devices will be adequate.
3. Until you specify the range of the field parameters, the electrical chracteristics of the magnet, and the equipment you will be using to measure the magnetic field strength, no one can give you meaningful advice about the control or feedback system.
Lynn

Best design idea for parallel DAQ (via GPIB), PID control and watchdog system

Hello!
I am a starter programmer in LabView, I already understand the basic ideas, and design patterns, like producer/consumer, events state machine, functional global variables, and so on, so the basics...
I started a project a few weeks ago, and first I wrote and tested all of the necessary subvi-s for my project, like the ones initializing my GPIB devices (a Keithley mux and a dvm), controlling/reading out the measured voltage/resistancy values from them, subvi for my Static Analog Output card (I have to drive 7 analog output channels, 4 has to be PID controlled regarding to some of the measured values from the GPIB devices), and another subvi for the analogue card, sending TTL watchdog signals out to my experiment in every 2 seconds.
Any idea is welcomed about suggesting the best design pattern for my project.
The main features of my program would be:
After starting the user interface the program starts with a start-up state, initializes the DAQmx channels and the GPIB devices. The program starts to read out different values from the GPIB devices, including 4 temperature values in every 3 seconds.
In the same loop (?), using PID control, the program sets the DC voltage values of 4 channels (3 to heating wires, 1 to a Peltier-heat pump) on the Static Waveform Analogue output card, the remaining 3 values are constants.
I have to send digital TTL watchdog signal to some relays from the same output card, changing its state in every 2 seconds (not the same rate as the GPIB values are read out).
When the 4 temperatures and the power values regarding to the heating wires are equilibrated after a few hours, the program goes into another state, and signals to the user, that the measurement can be started. During a measurement, I write out all of the measured values to a TDMS file, and there is also some basic calculations "on the fly", like a moving average.
After the measurement done, the user can swap samples, and the program goes into the above state, waiting for equilibration . and so on...
Do you think I should use a Producer/Consumer pattern with events? Or someone would recommend me a better design idea?
Thanks very much!
ps.: I read out lots of values from the Keithleys, so I put them in a cluster. I made a small test vi (attached without the GPIB comm subvi-s), just to test the GPIB comm. So this is the recent state of my project. (all other subvi-s tested and ready to use as I wrote above, like the DAQmx output part)
Attachments:
GUI_Calorimeter_control_image_v2.vi ‏284 KB

Okey
I think it is a better approach if I work first, and after I ask
I go with small steps. For first, now I just want to make a DAQ analog output loop, and parallel a watchdog loop sending out TTL in every 2 seconds.
The main loop in my project will iterate with approx. 10-15 seconds.
I want to check in my watchdog loop, if my main loop hangs up (in that case the PID control stops, but the danger is if the output voltages stay on).
After some readings, I have decided to use a functional global variable.
I have attached the vi, can someone give me advice, what would be the good solution for this purpose?
(I know it is a bit silly what I messed up with the shift registers in the bottom loop, it was some experimenting).
Thanks in advance!
Attachments:
watchdog_funcglobvariable.vi ‏12 KB
Global 1_stop.vi ‏4 KB
analog_output+Watchdog.vi ‏57 KB

NI Robotic starter Kit DANI PID control

Hello
I have this great kit and interested to do a kind of research of PID control on the two DC motors.
I already saw links that can do this job but I noticed that I can not find any technical datasheet having the motor paramters ( Mechanical or electrical)
I plan to bulid a tranfser function usig these paramters and then design a PID controller to make a speed control.
I searched the internet for the datasheet for these motors and could not find.
I think I should use a system identification for these parameters...so the question is
Is it possible to do any experimental system identification for identification of the DC motor parameters without deassebling them from the kit???
and how to do this job using labview??
if any has the datasheets for these motors (TETRIX DC Drive motor, part number 39083) it will be helpful ...
Thanks
A.Hakim

Hello ShishKeBobby
Thanks for your reply, but realy these information I knew, I need more information like a datasheet for this DC motors concerning the electrical and mechanical parameters.
I searched for the tetrix DC drive motor, part no. 39083 on pitisco web site but I could not download the datasheet.
these are the information I need
Motor constants (KT, KE)
Motor internal resistance (Rm) and inductance (La)
Motor friction (viscous friction)
Interia (J)
, thanks
or I am thinking to get these parameters by system identification but I dont know how without disasseblying of the dc motor from DANI and having a benifet from Labview and the assembled Morors in DANI.....
what you think?
Thanks for help
A.Hakim

Toolkit for feedback system? Motion; PID; Control/Simulation???

Hi, I have to develop/program an organ bath system - a feedback system mimicking real sinusoidal breathing oscillations (shown in attached images). I have NI Labview 8.5, NI-Motion 7.6, a linear motor (M-235 DC-Mike actuator), an MID-7654 Servo Power Motor Drive and a pressure transducer. I believe I will need to control the PID controller and am aware of the PID Control Toolkit as well as the Control Design and Simulation Toolkit for NI Labview. However, is it possible to control the system using the NI-Motion software I have at the moment? If not, do I have to purchase both the PID and Control/Simulation Toolkit or just one? Thanks in advance...
Attachments:
feedback design1.JPG ‏25 KB
feedback system1.JPG ‏42 KB

Dear Garry,
Do you have a motion controller to interface the MID-7654 to your
computer and LabVIEW? This would be the PCI-734x or PCI-735x. If you
do, I believe that you could implement your application with LabVIEW
and NI-Motion. You could do so by using the analog feedback feature for
the control loops for each axis. Then, you could specify the optimal
sinusoidal moves/pressure patterns that mimic real breathing patterns.
The analog feedback from your pressure transducer will be used during
the move(s) to maintain the pressure that you want.
Please see Chapter 13 here for more details:
NI-Motion User Manual
http://www.ni.com/pdf/manuals/371242c.pdf
Here is also a good discussion forum post on Analog feedback:
Can i use NI-7358 to implement a hybrid position force/torque control system?
http://forums.ni.com/ni/board/message?board.id=240&thread.id=2976&view=by_date_ascending&page=1
I believe that the above option would work for you, and you would not
have to use the Control Design and Simulation Module or the PID
Toolkit. Please let me know if you have any additional questions. I
haven't actually set up a system with analog feedback from a pressure
transducer before, but I believe that the above would be a very viable
option.
Best Regards,
~Nate

PID control with an H bridge

Hi everyone,
I have been working on a project with labview for the last few months now and I have reached a point where I am in need of some assistance.
Basically, this next part of my project requires me to drive a linear actuator to apply a force to the end of a shaft, with a load cell in between the actuator and shaft, providing me with the actual force applied.
I need to use a PID controller to maintain a constant specified weight onto the end of the shaft, this in itself should be simple but I have an issue with the way the actuator is driven.
The actuator is being driven via an H bridge that has 3 seperate inputs to drive the actuator:
direction = logic high/low 5v high 0v low
break= logic high/low 5v high 0v low
Speed= Pulse width modulation
My plan was to use a basic PID controller to adjust the PWM going into the H-bridge by adjusting its duty cycle between 0.10 (fast) 0.90(slow) and then using basic comparison functions between the set point and process variable to control the logic to direction and break. So for example.....
I want it to apply 5kg onto the end of the shaft
my set point is 5 and the variable is 0 so labview applies a logic high to direction (to go forward) and logic low to break (to let it move) and the PWM is adjusted to zero in on the set point.
I cannot get this to work however and was wondering if there was a better way to do this?
I appreciate that this may seem unclear, so i hope I have explained it well enough!
Many thanks
HCook
Solved!
Go to Solution.

Hello,
Thank you for very much for your reply.
I really should have explained this better, but I only had a few minutes to post my code. I should also mention that Im teaching myself labview, so Im sure I could do this a lot better.
OK, so here is whats happening...
This is just a secttion of my code, as Im not allowed to upload the whole programme.
This section is meant to control the weight being applied onto the end of a shaft that is defined by the user.
By flicking between auto and manual the user can choose between the PID and comparison moving the actuator or themselves manually.
The two express vis that are outputting an analog voltage are to provide the logic to the h bridge.
To give me Proportional control, I have simply used a comparison function to look at the weight on bit i have requested (elsewhere in the programme and hence the local variable) and the actual weight signal from a loadcell being brought into labview from an anolog input. So for example, If i request 2kg then the comparison between the two signals then tells the h bridge to move the actuator to apply more or less wait depending on the signal.
I have got this bit working fine.
Now, the speed with which the actuator needs to move, must be continuosly adjusted to provide a precise adjustment to the weight and I wanted to do this by continuosly adjusting the duty cycle of the PWM through the PID. Thank you for pointing out the loop issue, preventing the PID from passing on the adjustment, I had not spotted this!
I will re build the code and condense it down into a smaller number of loops.
The WOB speed task, which is outputting the PWM to the h bridge keeps telling me that the specified resource is reserved and will not function after my inital run. Does this have anything to do with the PID not working ?
Also, when I run the programme in manual mode, where by I move the actuator manually and adjust the weight based on the load cell signal, I get an error when I adjust the duty cycle. It informs me that the PWM must complete a full cycle before the duty cycle can be adjusted. Now the rate at which im changing the duty cycle manually is no where near the same speed a PID may adjust it and therefore I can see myself having the same problem in auto mode.
Thank you for your help!
Hcook

PID control temperature of oven

Hi! I should check the temperature of an oven through a PID control.
I wish that, after setting the reference temperature, the system acts on the power supply and change the current on the resistances of the oven, so that the temperature of the oven reaches the reference temperature.
Not knowing the programming language labview, I wanted to know if any of you have already saved the program in the PC and can post it, please.
Thank You!

aputman wrote:
That's why I used words like "think" and "may". I haven't been successful at it but I am definitely no expert.
What sort of incorrect response do you get from the heater system? If you're actively working on such a project I'd be happy to help.
For tuning a slow system, I highly recommend starting with the Cohen-Coon method (or the similar Ziegler-Nichols Open Loop approach). Take the PID out of the loop. Set the output at a fixed level and allow the system to stabilize. Change the output, and allow the system to stabilize again (make sure you wait until the system is actually stable). Record the output and process variable the entire time. Then you use that data to make a couple of quick measurements, plug the numbers into the tuning formula, and you get your gains. Unless the system is horribly non-linear, these gains will work well. Make sure you get all the units correct (for example, the LabVIEW PID block expects Integral Time in minutes, and not an integral gain).

Level Control with PID Control & Pulse-Width Modulation

Hi all,
I have attached my program which I'm having trouble wiring up in the block diagram.... I'm fairly new to labview, but basically I have a level control project with an analog input cistern arm turning a pot for my test tank (configured as DAQ assistant voltage analog i/p) and a pump working off a reservoir (configured as DAQ assistant voltage digital o/p). My electrical side of things is working correctly and I have tested both DAQ assistants I/O's successfully off a basic program, minus the PID & PWM... I found a simple PID control subvi which I think I have wired up correctly, apart from the output variable... I also found a bit of code for PWM using the square waveform vi (far right side of the program) which I have tried to include in the program, but I've been unsuccessful with that. The ideal operation i'm looking for with this project is to be able to enter different values for the setpoint, for the PID to kick in to find that setpoint each time using the PWM to drive the pump, which has a flow rate of 13L/min. I have a manual valve to release water from my test tank which I can set accordingly.
My questions are;
- How do I connect the 'output variable' of the PID subvi to my DAQ assistant digital output(both DAQ assistants are set at 1 sample on demand)?
I have a 'number to boolean array' function, but this gives an error saying that the number of tasks generated are not the same...
- How do I wire up the PWM bit of code? Do I need to include the 'error in & out' tabs?
-Am I on the right track with this program or am I way off the mark?!
Any feedback on this would be greatly appreciated. Thanks for your time,
Richie
Attachments:
PID-RichLevelControl.vi ‏91 KB

Rich-MechatronicsStudent wrote:My questions are;
- How do I connect the 'output variable' of the PID subvi to my DAQ assistant digital output(both DAQ assistants are set at 1 sample on demand)?
I have a 'number to boolean array' function, but this gives an error saying that the number of tasks generated are not the same...
- How do I wire up the PWM bit of code? Do I need to include the 'error in & out' tabs?
-Am I on the right track with this program or am I way off the mark?!
You're a bit off track. You need the output of the PID to go into the PWM generator, and the output of the PWM to be written to the digital output. Right now you have the output of the PID connected directly to the Digital Output in a way that won't work, and the PWM generator hanging off the side not really connected to anything. Also, the PWM generator isn't really going to work since you're generating it at the same frequency as your PID loop runs. Try a simpler algorithm such as on/off control first and see if that works for your system.

Plant Simulation for PID Control

Hi,
This is my first major project with LabVIEW.
I am designing a PID controller to control the speed of an electric motor. It is required to keep the speed at an input value when the mechanical load changes.
I would like to simulate the plant (i.e. the motor) with a first or second order transfer function, e.g. H(s)=b0/(s^2+a1*s+a0). I would like to do this before I try closing the loop with the physical system in the lab (as I haven't applied any control theory before).
I have LabVIEW 2013 here. In the "Control Design and Simulation" palette, I have "PID" and "Fuzzy Logic" (no others). The lab has LabVIEW 8.6 with the same "PID" and "Fuzzy Logic" toolkits. I don't think I need to run the simulation in the lab.
Is it possible for me to simulate a plant with an H(s)?
Thanks in advance!

First of all, I strongly recommend you to try to see if you can update LabVIEW to the educational version of 2013. This has not only an up to date library, but also have the LabVIEW Control Design and Simulation Module which has several examples on Motor Control. You can find them in here:
examples\Control and Simulation\Case Studies\Mechatronics\DC Motor
examples\Control and Simulation\Case Studies\Electrical Machines
In general, some universities/schools just need a student request to obtain the latest version of the software. Now, if you don't have access to it and you are stuck using LabVIEW 8.6, you can try to use the following in:
<LabVIEW 8.6>\vi.lib\addons\control\advanced\continuous linear.llb
There you will find the Transfer function.vi that allow you to simulate a second order model. Then you can use the PID VI to closed the loop using shift registers. Keep in mind that your model can only have the order of the numenator smaller than denominator, otherwise the simulation won't be correct (that is the reason we have the Control and Simulation Loop).
Hopefully this will help you...
Barp - Control and Simulation Group - LabVIEW R&D - National Instruments

PID Control motor DC 12v

Hi everyone,
I wanna control a 12v DC motor using PID control toolkit 8.2.
- a close loop control system
- using a DAQ model: NI USB-6008
- how do make a DC motor speed control 12v with PID control
Im stuck at getting pid.vi and i wanted to know what is the problem.
pls help me on my problem, if can pls make an example VI for me
Thanks !
Solved!
Go to Solution.

Well there are a lot of things you need to do this, LabVIEW software being only a part. Firstly, most DAQ cards will not source sufficient current to actually power a motor, particularly a USB6008, so you will need some form of amplifier/power driver. For closed loop you will need some feedback to tell you what the motor rotation is, usually a slotted wheel with a LED and sensor (if this is a project for school or hobby one source you might look at is an old wheeled mouse). So with these two you have a way to drive the motor and then detect its motion. Then you can get to the idea of doing PID, which is taking the feedback (from whatever sensor you end up using) scaling it to match whatever you are using, and apply it to one of the PID equations to get it to match the target value.
Putnam
Certified LabVIEW Developer
Senior Test Engineer
Currently using LV 6.1-LabVIEW 2012, RT8.5
LabVIEW Champion

PID control of Counters (PWM)

Hello everybody!!
I work on a closed loop PID controlled problem (Labview 8.5) and I have a couple of questions in order to make some progress!
Firstly, I have to declare that my loop is composed of 2 AI channels (2 accelerometers), 1 AO channel (excitation channel-shaker), and 2 CO (for pulse creation PWM-controllers). The idea is very simple. When the AI (channel 1) value surpass or underpass a predetermined threshold value, then the appropriate CO should be activated in order to apply the necessary control forces and simultaneously to copy my data values of both AI channels in binary style for CPU velocity reasons! BUT, with the PID controller I want to optimize the Duty Cycle value of the pulses!
My questions are :
1) Why when I put Kp=Ti=Td=0 ( = run WITHOUT control) I can copy ALL the AI samples and when I start to activate the PID controller (let’s say for only Kp=0.5) I CAN’T copy ALL the AI samples? Where is my fault?
2) About the PID vi which I use, is it correct or I should use the PID vi for ARRAYS?
3) And finally, about the Boolean statement just before the Case Structures and the Shift Register, is it ok/necessary?
I attach two vis, the ReadBinar .vi is used to read my binary files generated in the end of running of the Control.vi.
Best regards
Grigorio
Attachments:
Control.vi ‏277 KB
ReadBinar.vi ‏162 KB

Hello Zach!
First of all, I want to thank you for your kind interest on my problem!!
I must describe you the desired process with the Control.vi. There are two AI channels writing down the acceleration of a structure in two different points (for velocity reasons I use Binary Type storage for my data). One AO channel for structure sinusoid excitation (shaker) and two CO channels for controlling two solenoid valves with which I want to control my structure acceleration (minimize it as well and fast as possible)!!
In order to help the description, let’s ‘cut’ the block diagram of Control.vi into three pieces (Before While Loop – Inside While Loop – After While Loop).
In Before While Loop section, the main question is about simultaneousness. The DAQmx Start inside the Flat Sequence Structure, do you think that is necessary, ok? I want to run my experiment for 30s and to collect 6000 samples with 200 samples/s. In addition, in the CO DAQmx timing, I have set 200 samples/channel in order to be able to change the duty cycle value because of the conditions inside the While Loop. Do you think that everything in this section works well?
Inside the While Loop, firstly in the DAQmx Read, I have set 200 samples per Input Channel, which is also equal to the AI and AO Sampling rate! Before some days I have put there -1 and unfortunately the total written samples were less than 6000!! My main problem is how I can check all the read data without losing run velocity and simultaneous if one sample is >0 then it goes further to the first PID.vi (left solenoid valve) or if that sample is <0 then it goes further to the second PID.vi (right solenoid valve)!! When a sample has gone to a PID.vi, then I want to tune the duty cycle of the controller (PWM control) as well as possible in order to achieve the Setpoint value for the second AI channel. Are all these possible? If not, what do you suggest me?
In addition I compare the present duty cycle value with the previous one in order to be inside a tolerance value (let’s say 0.1). Moreover, is it correct the Case Structures where I want to share the positive and negative AI samples before going to the respective PID ?
Finally, After the While Loop, I believe that everything is OK. I just finish all the tasks.
I have to mention that I work on a PCI-6289 and Labview 8.5.
With best regards!
Grigorio
Attachments:
Control.vi ‏288 KB
equal within tolerance.vi ‏9 KB
ReadBinar.vi ‏163 KB

I was transferring data from my old iMac to my new iMac via Time Machine. After about 4 hours, the electrical power fluctuated and turned off my wi-fi. Now most of my necessary programs are useless. How do I erase and start over?

I was transferring data from my old iMac to my new iMac via Time Machine. After about 4 hours, the electrical power fluctuated and turned off my wi-fi. Now most of my necessary programs are useless. How do I erase that mess and start over?

Hello there, LynnS.
The following Knowledge Base article and it's referenced link should get you started with the Erase and Install of Mavericks:
OS X Mavericks: Erase and reinstall OS X
http://support.apple.com/kb/PH14243
Once you've gone through those 2 articles, this article should help you with restoring from your Time Machine Backup:
OS X Mavericks: Recover your entire system
http://support.apple.com/kb/PH14185
Thanks for reaching out to Apple Support Communities.
Cheers,
Pedro.

I am looking to control a 4-way hydraulic solenoid valve. Do I need a PID control toolset, or can i control the system through my 16E4 daq card and scxi chasis

I am looking to control a 4-way hydraulic solenoid valve. Do I need a PID control toolset, or can i control the system through my 16E4 daq card and scxi chasis

I think you're asking 2 different questions.
The PID control toolset is for using PID loops for control; it's just software.
The DAQ card and scxi chassis are hardware. If you have the appropriate signal conditioning cards in your chassis to control/monitor your solenoid valve, then you can run a PID loop.
I believe the simple answer is: the PID control toolset is the best way to do control, but there are simple PID VI's (even on this website) that you can download and use for simple control.
Mark

PID control in a windows CE Labview application

Hi there,
I want to build an application that will control the temperature in some ovens, using PID control. The application will be running in a controller (or a touch panel computer) with windows CE OS. I have Labview 8.6, PID control toolkit 8.6 and Touch panel module 8.6. The problem is that the PID vi's don't seem to work in touch panel module.
Is there any way to implement PID control in a windows CE Labview application?
Thanks in advance.
Solved!
Go to Solution.

I think with a timed loop you can run reasonable good timing down to 1 mSecond. I think 1 mSecond is the lower limit for non realtime systems like Windows/windows CE. And if you have the PID toolkit this will supply you with the functions you need. You do not need an extra CE PID toolkit. This because the touch panel module run under your standard Labview environment. But I do not know if all the functions in the PID tool like fuzzy logic are compatible with CE. Have you also considered Windows Embedded as OS for your module. With windows Embedded you can run standard Labview built exe files
Both Windows Embedded, and XP Embedded can be trailed
http://www.microsoft.com/windowsembedded/en-us/products/westandard/default.mspx
Besides which, my opinion is that Express VIs Carthage must be destroyed deleted
(Sorry no Labview "brag list" so far)

PID control to maintain constant heater electrical power?

Similar Messages

Maybe you are looking for