Closed loop velocity control based on load cell force

Hello,
My application is for a drill, that drills into rocks of various densities for the purpose of collecting rock core samples.
My setup has 2 motors which get controlled, one spins the drill bit at a constant velocity, the other moves the drill mechanism along a Z axis.
For efficient cutting, it is desired to apply a constant force between the drill bit and the rock. I have a load cell which measures the force being exerted by the drill bit on the rock surface, and this force can be adjusted by changing the velocity of the Z axis. So I would like to employ closed loop control to adjust the Z axis velocity to maintain a constant force on the rock.
Platform: cRIO 9073, with NI 9505 & 9215 Modules, Labview 2010 Full with RT and FPGA modules.
The load cell is by Transducer Techniques, and I use their TMO-1 module to condition the signal, the output of which is attached to an input of the 9215 module, where 0-100 lbs equates to 0-8VDC.
The motors and encoders for the Drill and Z axis are connected directly to the 9505 modules.
Right now I am using a modified version the example found in ...\examples\CompactRIO\Module Specific\NI 9505\Velocity Control (closed loop)\Velocity Control (closed loop) - NI 9505.lvproj to accomplish velocity control of the motors.
My questions are:
1) Do I have the appropriate NI hardware/software for this task?
2) With my current hardware setup, what would be an appropriate way to control my Z axis velocity rate based on Analog feedback from the load cell?
3) Development time is a critical factor, so are there any toolkits etc that are easy to get started with that would drastically decrease my development time, or do I already have everything I need?
Thank you for your time
-MK Hokie

1. Your hardware and software look appropriate assuming the motors are compatible with the 9505s. You didn't mention the NI SoftMotion module in your software list which is something you will need.
2. There are a few ways of doing this. One method would be to have a force PID loop that would attempt to maintain a force setpoint by directly outputting values to your torque loop. In this case, the drill would essentially move as fast as it could while maintaining the force setpoint. Another option is to have the force loop output a velocity setpoint. You would then have a velocity PID loop that outputs torque values to the torque loop. By adding this additional velocity loop you could have control over your maximum and minimum velocities. There are likely other alternatives as well, but these are the first two that come to mind.
3. Unfortunately there are no shipping examples that close the loop on force feedback. My advice would be to start with the NI 9505 shipping example and adapt it to your needs. There are quite a few things you will want to change though. Do you know if you will need to use the trajectory generator to move the drill into position before starting the force control?
Assuming you don't need any trajectory generation, you can scrap the entire RT portion of the NI 9505 example and just create the necessary FPGA code. On the FPGA, you won't need the Spline or Synchronization code either because this information would no longer be coming from RT. You could take these out and replace the position loop with a force loop and possibly a velocity loop and your FPGA program would basically be finished. In fact the only real motion IP that you will need is for the encoders (assuming you want velocity control) and PID. Then you would need to create an RT VI that allows you to send down enable, disable, PID gains, and setpoints.
If you do need trajectory generation, you would want to keep most of the example code the way that it is, but then program in a 'Force Mode' that utilizes the force and velocity controly as described above. You could think of it as having two different routines programmed side by side.
Regards,
Burt S

Similar Messages

NI 9505 Closed Loop Position Control Example

Hello, I have a cRIO 9073 with a NI 9505 module that I'd like to use for simple position control of a unit along a lead screw.
I don't have the softmotion module, and am trying to write a program bassed off of the "Position Control (closed loop) - NI 9505" example to control the position the small motor attached to the lead screw (Faulhaber 2342S024CR with a 512 count/rev encoder that we had laying around)
I've reviewed the manual PID tuning example, and have not had much luck getting the response that I'd like when making large position moves simply by adjusting Kp,Ki,Kd gains of the position loop, as the overshoot remains too high for this application when making large moves. The system is also oscillating about the set point, and doesn't ever seem to dampen out unless I change things other parameters on the fly such as the current limit, or current loop parameters (osciallations get worse as current limit is increased).
Can someone advise me if the components of this example are up to this task? Or on the interactions between the current limit, current loop parameters, and position loop parameters from this example, and which parameters would have the most impact on achieving desirable system performance?
Is there a VI available that can autotune such a motor?

Hello - there are many reasons why a closed loop controller can oscillate - from correct settings of controller (kp,ki,kd) to making sure signals act in the appropriate direction to deadband/friction in the actuator to badly sized signals/actuators.
Firstly, have a look at the signal your controller is outputing (ideally in LabVIEW so you can graph it). Does it oscillate - perhaps as a sawtooth, a sinewave or simply switching between maximum and minmum values. I presume the electrical motor driving the screw which is driven from some AO signal from the cRIO (could also be a PWM signal driving the motor).
I expect (from what you say about current limit) the control signal will be oscillating by switching between maximum and minimum (e.g. +10V to -10V) or oscillating like a sinewave. What values of kp, ki, kd are you using ? If kd is non-zero, set it to zero (you only need worry about this if you want to get maximum performance). Is ki non-zero ? Try setting it to zero - any better ? If you are still getting big oscillations in your control signal, keep reducing kp (e.g. half each time?) until oscillations disappear (as you reduce kp, control signal *should* get smaller - maybe not straight way though).
If this does not make oscillations go away, then it may be that you have a sign wrong in your loop - i.e. a positive control signal makes lead screw move in opposite direction controller expects. This should be a fundamental thing sorted out when setting up the loop - you could do an open test to check which way +ve voltage moves lead screw. If you find it moves in opposite direction - you can either re-wire, or put a "-1" gain on controller output.
If there is any more subtle oscillations / obersvations, then try to show some plots of the lead screw motion and control signal, as that always helps when trying to diagnose what is going wrong.
Good luck.
Consultant Control Engineer
www-isc-ltd.com

Applying 5 kN external force on a load cell - Force readings to start from 0 kN

I am recording readings from an Omega Load Cell using DAQmx (Continuous bridge example) . A pre-tension force of 5 KN is applied on the load cell. Is there any way of forcing the applied pre-load force to drop to zero so the readings to start from zero?
Thanks!

The way you worded your question in somewhat ambiguous.
You really do not want to remove the physical preload force, do you?
I think what you want to do is to change the readings to account for the preload. That can be done fairly easily if you have complete control over the applied loads and know when there is no additonal load on the cell. In the weighing (scale and balance measurements of force or mass) this process is called taring. The tare is the weight or force without the external load. At the grocery store they adjust for the weight of the container before they add your food.
Add a Tare state to your state machine. When the user presses the Tare button on the front panel, the program takes a reading from the load cell (or several readings to be averaged). That reading is the tare force. Place it on a shift register. Then subtract the tare force from the readings taken while the desired measurements are happening.
If the maximum load is close to the load cell limit, the termperature of the load cell varies, or there are impact loads involved, then this simple taring approach may not be good enough. That is not because of any inherent problem with the method, but due to the things that can cause a load cell to drift or change baseline outputs.
Lynn

Understanding velocity control on 9505 FPGA VI

I was able to quickly use the 9505 Servo Drive example to do closed loop position control on the FPGA but I'm having trouble with figuring out how to modify the code to support velocity control (which I need for a different axis). I'm trying to make my modifications on the FPGA VI itself rather than on the RT Softmotion side.
Here are the issues I'm having:
If I use the PI Velocity Loop with my Velocity and an arbitrary control setpoint velocity, I can see the velocity stabilizes (motor output looks uniform) but I can't correlate it with the velocity setpoint other than a bigger number is faster. Velocity (from the Encoder loop) seems to readback in values of just 0-2 on my FPGA VI (I don't fully understand the units but I see my position change on my encoder readback in thousands of counts per second). Why are they so different/how do I scale my encoder velocity correctly?
Using just the shipping 9505 Servo Drive example (position control), how do I set the velocity of a move from within the FPGA code (in interactive mode)?
Solved!
Go to Solution.

I was able to get my velocity readings to match my velocity setpoints when using velocity control mode by increasing my Timer Config.Target Period and Encoder 'calls per sample encoder' from 2000 to 40,000. Now my velocity readback is +/- 1 of my velocity setpoint for my drive range. This makes sense to me now - if you read the encoder to quickly it hasn't accumulated enough points to accurately calculate the velocity. It was in the documentation but I didn't fully understand it.
So now I'm down to one question - (from last post):
I still don't understand how to set the velocity of a move if I'm using position control (out of the box example) from within the FPGA code (on the 9505 example). Is the best way to do this just to limit the 'Current Output Range' depending on the max velocity requested? The NI Softmotion RT VIs and Express VIs are able to set 'Velocity' but I'm really unclear what that the SoftMotion RT VIs are actually doing in terms of interacting with the FPGA code. Can you explain how that works?

Dynamic force control using linear servo actuator + load cell

Hello,
I am designing a test fixture which will allow us to test the performance of actuators we install in our products. I need to apply a constant load to the actuator while it is extending/retracting. I would like to be able to use a linear servo actuator and a load cell on the same axis as the UUT to provide and monitor the load. The actuator under test does not travel at high speeds, its max speed is approximately 1in./sec.
I need to be able to maintain a constant load while the actuator is moving. Therefore I'll need some kind of closed loop system to maintain a velocity such that the load being reported from the load cell is equal to the expected load as the actuator is moving.
I am trying to figure out how to best implement this in a cost effective and time-saving way. I have not purchased any hardware at the moment so am open to suggestions. We do have LabView 2009 with all the toolkits. Would it be best to implement this using a motion controller card or would I be able to get good results using a standard DAQ?
Message Edited by fnaeem on 02-05-2010 05:58 PM

As you have stated correctly, you will need a deterministic closed loop system to accomplish this task. The most cost efficient while reliable solution for this purpose is a motion control board like the PCI-7352. This board provides quadrature encoder inputs for positioning tasks and analog inputs for any other type of control. Torque/force control is a very typical task for this board and it provides a simple API and useful configuration tools.
If cost savings are a primary goal, you could also use a PCI-7342, but for your application I would recommend the PCI-7352, as the PCI-7342 provides only 12-bit ADCs, while the PCI-7352 provides 16-bit ADCs, resulting in a much better resolution of your force feedback signal.
I hope that helps,
Jochen Klier
National Instruments

RT multi-motor motion control in a closed loop system

Hello NI Community,
We have 12 stepper motors with load cells attached in line on each motor that are connected to a RT PXI chassis. We use an optical system to gather 3D data on the host computer which is used to calculate relative angles between 2 connected objects. This data is passed to the RT target as one of several feedback based control strategies that are used (relative angles, force on each load cell, motor position, etc.). Our Labview code is setup to utilize any of these control strategies for any motor, often using multiple strategies for different motors at the same time. The code deployed to our RT target is currently a single timed loop that incorporates the load cell reads, PID control calculations, motor command writes and position reads. In determining the timing of this loop we find it to be ~18Hz. We would like to integrate a new control strategy that is inefficient below 30Hz and are trying to determine how we can achieve this. It seems that our limiting factor is the constant writing/reading of each motor at ~4.6ms/motor, although this doesn't seem correct with the posted 62us speeds shown in the specs for the motion controllers. I'm not sure if this there is a setting that I am missing somewhere that is preventing me from achieving these speeds or if this is a function limitation of our hardware setup. We would like to achieve this with all 12 motors, although not all motors are always in use. The PXI components we are using are listed below.
PXI-1050 Chassis
PXI-8105 RT Controller
PXI-7344 Motion Controllers
UMI-7774 Motion Interface
Would any of the following be more advantageous than the others or is there another method someone has found useful in speeding up their systems.
Split motor read/write into another timed loop with a higher priority over the PID loop. (deterministic approach)
Create a unique read/write loop for each of the 3 Motion Controllers
Create boolean activation to ensure only the motors that are being used are incorporated in the control scheme
Sorry for the long post but I wanted to make sure I included as many details as possible. Thank you in advance for your help with this.
Brian

Hey,
Have you tried diagnosing where the problem is by seperating the processes and timing them to see what is causing the delay of the motor control to ~5ms?
Regards,
A. Zaatari
National Instruments
Applications Engineer

Closed loop control of step motors possible with 7344?

Hi All
I have been looking around here for a while for an answer to this question.
For me, a closed loop control system is correcting for following errors all the time, also when the move is complete.
If the load on a system changes, there will often be a need for compensation in order to keep the position right. Then you need a closed loop control system.
I have made a system using DC motors with a 7342 controller. We are in the process og getting a new similar system, where the manufacturer chosed stepmotors in the believe that it can be used in closed loop.
Is it really true that the NI version of closed loop is only performing a what you call a "pull-in" at the end of the move in order to correct for lost steps or flexibility of the connection between motor and object/encoder?
I would call this "backlash compensation" or something like that.
Why dont you make a real closed loop option. The control voltage from your servo motor control, could be fed into a voltage-frequency converter with a matchin sign signal.
This shouldn't be too complicated to accomplish.
/b

You are right. NI motion control boards don't apply a control algorithm
during moves when configured in closed loop stepper mode. In this mode
the board monitors the following error during the move and generates an
error when the following error limit is exceeded and they start the
pull-in moves at the end of the move if necessary.
If you really want to do PID control with stepper motors you still
could connect an external V/f converter to the DAC outputs of the board
and control the axes like DC motor axes. Some vendors implement this
feature on their board but NI has decided not to do that as we don't
think that this approach provides a good solution. Here are some reasons:
The most important issue is the fact that you could easily exceed
the maximum rate of change of the motor frequency in the case that the
following error increases during the move. For a DC motor this would mean that the
voltage of the controller increases to compensate for this error and
the motor will follow - probably with some delay, but it will follow. For
the stepper this could mean that the acceleration becomes so high
that the motor stops immediately as it can't follow with a delay like a DC motor. What
should the controller do then? Restart the move automatically? Generate
an error? There is a big chance that you end up with a system moving in a stop and go mode.
The second issue is related to the control algorithm itself. The transfer function of a stepper motor is not really linear so it will be quite hard to find good tuning parameters. A DC motor can be tuned by analyzing the step response and the Bode plot. For the reasons that I have described in 1.) this won't work for a stepper so how should you tune it?
I have talked to some motion control engineers who have tried to control steppers with a PID algorithm and they all agree that this is a real pain and it's not recommended.
So if your system requirements involve online following error compensation I strongly recommend using a DC motor.
Best regards,
Jochen Klier
National Instruments Germany

Creating a simple closed loop control

Hi everyone,
I need a bit of help creating a (very) simple closed loop control.
Note: I am using 3 Measurement Computing boards: one USB-2416, and two USB-TC's. Since Measurement Computing has their own driver (called ULx), it might be a bit more difficult to understand than the NI drivers, but keep in mind ULx is the equivalent to DAQmx.
I need to be able output a 0 or 1 binary value based on measurements from 4 voltage input channels compared to constants. Ie. if voltage measurement < 3.5 (constant), send a boolean value (see a, b, c, d in attached photo) which in turn gets sent to the ULx Write VI, and that outputs the binary value of 0 or 1. The problem I've run into is that I need to "compare" single chanels from different boards, which gives me single boolean values for each channel. The ULx Write VI only accepts boolean arrays. Is there a way (and there probably is, I just haven't been able to find it) of arranging these lone boolean values into a boolean array?
(see attached file for what I have so far)
PS. I am a COMPLETE rookie, only been using LV for a week or so, so please explain everything as if I have no clue what's going on.
Thanks in advance!
Solved!
Go to Solution.

Hi,
the attached example I've made should demonstrate what you need to do.
Some things to think about:
1. It seems that the ULx vis return arrays of signals. If so you can select signals with "index array" as done in my example. That consumes less space and does not change the type of the signals to variant.
2. If you compare the signals to your constants you will receive boolean arrays because every element of the measured signal is compared to the constant (see my example). You may then decide how to process that info - another hooray for signals :-)
Regards
Florian
Attachments:
Example01.vi ‏24 KB

Controlling Linear Actuator via Load Cell

Hello,
I need to control the position of a linear actuator based on the force feedback from a load cell (rated up to 100 ft/lbs) connected to the tip of the linear actuator. What I want to be able to do is to set a force and have the linear actuator (driven by a stepper motor) move until it is within 0.1 ft/lb of the force setpoint. Once within 0.1 ft/lb of the setpoint, I would like to hold and control to the setpoint based on a user configured hold time.
I have the following hardware:
PXI-1033 chassis
PXI-7340 Motion controller card
UMI-7764 Terminal Block
P7000 Drive
Omega Engineering Load Cell model number LC201-100
Omega CCT-80 Load Cell Signal Conditioner
Omega FAR-1 Power Supply
I have the + output of the CCT-80 connected to the Analog Input (AIN1) and the - output connected to the Analog Input Ground (AIGND). This output signal is -10V to +10V (verified by DMM)
I have the ADC range set to -10 to +10
I'm reading the ADC as fast as possible (get about 700 samples/second) and this just isn't fast enough to control to the precision that I need. Also, it seems like there is a substantial amount of noise on this line.
Does anyone have any recommendations on improving the speed of the ADC read, or how to reduce the noise on the line?
If my requirement of holding to 0.1ft/lb is too strict for this hardware (7340 motion card) is there something else that I should try?
If I'm missing any other info that is needed to help me out, let me know and I'll update this post.
Thanks!

Hello AMac,
I have a setup similar to yours with a load cell attached to a linear stage. I want to use position control of the stage to apply a set load on the load cell (position-based explicit force control). Do you have a example VI I could look at if yours was successful?
Thanks,
Kyle

A/C three Phase motor control using 1/4 bridge Load Cell output and a USB 9172 Daq

NI Assistant,
I am tasked with setting up a Motion Control using two each OMEGA LC712-100K, -50K and -10K load cells to monitor the cable tension on six A/C motor driven winches. I also need to Monitor and calculate a Moment as well as the load slope for Load verses Time.
I have zero time to develop and I have searched your databases for existing Motor Controls to modify.
Should I use Case Structures and then place them in a while loop?
I setup a drawing in Word to visually define the task.
Signed,
Patrick Murphy
Attachments:
Layout for Testing Spars.docx ‏15 KB

Hi Patrick,
The reason why the Motion Control examples will not work for you is beacuse they are meant to be used with the NI Motion boards. Since you are using DAQ boards, the examples are probably not going to be able to help you too much. However, there is one example on the community that might be a place for you to start.
pmurphy wrote: Should I use Case Structures and then place them in a while loop?
What exactly do you mean by this? What do you want in the case structure or while loop?

Stepper motor closed loop control using 7344

I have some question about the closed loop control of stepper motor using 7344. From the NI website I got that closed loop steppers work differently from closed loop servos. Instead of adjusting the output on each PID iteration like a servo system, closed loop steppers will do a pull-in move at the end of a move to adjust for any difference between the target position and the encoder feedback. By default, it will attempt the pull-in move three times.
Now for example I got five points: (0,0) (10,20) (30 40) ( 31 60) (50 65). The request time interval I set as 10ms. This mean that in the first 10ms, the machine should move from (0 0) to (10 20). But for some reasons the machine can not move to (10, 20), it moves to (8,16) and the first 10ms passed. In the second 10ms, how it move? Move from (8 16) to (30 40), If like this, the following error will accumulated. In practise, it is not accumulated. Is there anyone can explain something about the closed loop control of stepp motor? Thanks a lot!

Requested Interval is additional data for the Position buffer type. The Position buffer type requires a Requested Interval parameter, and indicates the time between contouring data points in milliseconds. For all other buffer types, the Requested Interval parameter is ignored.
The controller will use the closest value it can that is greater than or equal to the interval value you requested. Your time interval must be an even multiple of the PID rate.
For example, given a PID rate of 250 ms, a time interval of 11.2 ms between points is physically impossible, so a call to configure buffer with an interval of 11.2 causes the buffer to actually be configured for 11.25 ms, since 11.25 is the nearest possible interval greater than 11.2. The following table shows valid intervals for each PID rate.
My question is like this. For example I got five points: (0,0) (10,20) (30 40) ( 31 60) (50 65). The request time interval I set as 10ms. This mean that in the first 10ms, the machine should move from (0 0) to (10 20). If it is impossible for the machine to move from (0 0) to (10 20), there are two ways to solve this problem. First is the time interval is 10ms and assume it move to (8 16) within 10ms and take (8 16) as the start point and (30 40) as the end point of the second move. Second is extend the time interval, assume it takes 14ms to move from (0 0) to (10 20). After 14ms, the (10 20) is the new start point for the second move. I think it works as the second ways.If not, the following error will accumulated. Is there anyone can explain something about the closed loop control of stepp motor in detail? Thanks a lot!

Closed loop control of DC motor drive using PCI 6251

Hi
i am using NI PCI 6251 for closed loop control of dc drive.(shunt motor,220v, 0.5HP, 2.5A rated, 1500RPM)
the dc motor is fed from a bidirectional dc-dc converter. this converter works in boost mode(forword motoring) and buck mode(braking mode/battery charging)
the converter is built using mitsubishi IGBT module. at low voltage side of the converter a battery bank of 48V is connected and high voltage side the motor is connected.
An IR sensor is developed to measure the speed of the motor and a hall current sensor is used to sense the converter current.
in the control part i have an inner current control loop(PWM controller) and a outer speed control loop.both controllers are PI controller. To measure the speed i have used counter of the DAQ assistant, then frequency. then this frequency is converted to RPM using labview.after giving the speed and current signals to the controllers , then i started tunning the PI gain, but at the starting the duty cycles was 100%, so the IGBT got damaged immediately. now how to tune the controllers during the closed loop operation. the switching frequency of the converter is 20KHz.
can any body suggest me how to run the dc drive in closed loop ?
thanking you.

Hi Premenanda
The freq data receiverd from the daq assistant has the units of Hz, or in terms of motor speed, rps (rotations per second). I can see that you are trying to convert that to rpm (rotation per minute). which can be done by dividing the rps speed by 60. Instead, you are multiplying it by 60 and also comparing with 2000. the resultant multiplied value is displayed in your program only if it is smaller than 2000.which is causing the problem here.( as seen in file 'original code.png)
I have attached a file named 'modified code.png' that shows how the conversion from rps to rpm is done. Please do the required changes in your code and let me know if it works.
Attachments:
modified code.png ‏18 KB
Original code.png ‏15 KB

Problem using PID toolkit and control design toolkit to design the closed loop system. (for DC motor closed loop)

Hi, i have facing some problem during i upgrade a project. This project is an opened loop system, it only achieved up to controlling the speed of motor, detecting the speed of motor, and switching the direction of motor while controlling the motor (This motor is a 12 VDC motor).
In order to improve the project, closed-loop dc motor control system will be implemented to correct the error of the motor's speed and maintaining the speed for the initial setting. I would like to use PID control method to do the closed loop system.
I already installed the PID toolkit V8.2 and control design toolkit V2.1.2, and i'm using DAQ usb 6221, LabVIEW 8.5
Below is my problem.
http://img177.imageshack.us/my.php?image=howtocreatethesetpointnx2.jpg
question: 1. How to generate a icon for set point? my setpoint is duty cycle...
2. How to feedback the output duty cycle to summing junction?
below this is my basic concept
http://img237.imageshack.us/my.php?image=closedloopbz5.jpg
Problem 2:
http://img357.imageshack.us/my.php?image=problem1yk2.jpg
question: Why PID toolkit icon cannot wire to cd series.vi?
Below is my original program...
http://rapidshare.com/files/140538836/pwm_generate-final_PSMII.vi.html

Hi Cyrus
Have you had the opportunity to see our
developer zone site on the PID toolkit? This article also has sample
code at the bottom that may help you in developing your application. I
have also linked below knowledge bases regarding setting a point
profile and generating a PWM from a digital output line.
PID toolkit
http://zone.ni.com/devzone/cda/tut/p/id/6440
How to generate a set point profile:
http://digital.ni.com/public.nsf/allkb/125F27AC143B6AFD86256C2B0004A4DC?OpenDocument
How to generate a PWM on a digital output line:
http://digital.ni.com/public.nsf/allkb/1561D31534F07D608625727900391114?OpenDocument
Thank You
Eric Reid
Thank You
Eric Reid
National Instruments
Motion R&D

Can the USB NI DAQs be used for process control,eg.closed loop? or is too fast

can the USB NI DAQs be used for process control,eg.closed loop? or is too fast.

Hi mho,
1.usb is very high speed that is correct.Better you can choose PCI DAQ.But thats upto you.
2. see this:-
http://sine.ni.com/nips/cds/view/p/lang/en/nid/14136
3.If Matlab support TCP/IP, that could be an option.
see Another idea: http://digital.ni.com/public.nsf/allkb/244A37667BD7CBCE86257520007F937B
Another simplest way to do it (assuming you running Windows) is to use a Matlab script.
If both programs running on different systems:-
Most simple and slow - Create two VI's with shared variable on both machines, and use a matlab script to
share data. (this makes matlab some kind of "slave").
More advanced but still relatively slow (Create two VI's with shared variable, on the Matlab machine build the .NET
dll, and it can be used on Matlab too ( at least at 2010b version, earlier version support only COM).
Create TCP/IP connection between two comps.
There is "out of the box" NI products, that communicate with Simulink models.You please do a simple search on that...OK
I think this link is also helpful for you:-
Procedimiento para la interface entre LabView 2009 y Matlab 2009b.pdf 1128 KB
Anyway All the best.Try....do it.
Thanks as kudos only

Is it possible to condition a load cell signal with a 1520 SCXI and then use it as the primary analog feedback for a 735X motion control board?

My system
PXI 1052 chassis
PXI 8196 RT controller
Flexmotion 7356 motion controller
Flexmotion 7354 motion controller
6259 M series DAQ
1520 SCXI
1520 SCXI
1314 SCXI frount mounting terminal block
DSM strain gage load cells
Exlar SR Brushless PM motors
Kollmorgen servo star CD series 5 drives
My objective:
I want to measure the force on the load cells with the 1520 SCXI (i.e. excite the load cell then amplify and condition its output) then I want to use this analog (force) signal as the primary feedback for my motion control system (7356 and 7354 motion controller connected to my drives and motors).
The problem:
The motion controller boards (7356 and 7354) can be configured for force feedback control via analog feedback from a load cell. However the boards implicitly expect the load cell signal to be amplified and conditioned with and external signal conditioner rather then using an NI SCXI module. Currently I’m am reading the SCXI signals via the 6259 M seriers DAQ and consequentially have no way to route the signal into the 735X boards for force feedback control. I can use softmotion to control the motors but then I loose the fast PID update rates possible with the 735X boards.
The question:
Is it possible to condition a load cell signal with a 1520 SCXI and then use it as the primary analog feedback for a 735X motion control board?
Thanks
Patrick Aubin
Ph.D Candidate
University of Washington &
VA MedicalCenter of Excellence for
Limb Loss Prevention and Prosthetic Engineering

Hi GG,
Thank you for your feedback.
>create your own external circuitry to amplify the signal.>
True a few op-amps could amplify and filter the signal externally but the performance of such an amateur built system will never match the accuracy and functionality of the 1520 SCXI. That’s why we spent the $2500 for the professional version.
>One thing that you could do is to use a UMI with your motion controller and then wire your signal from your SCXI to the UMI.>
As I understand it the UMI is basically a break out connectivity interface for third party drives. After conditioning and amplifying the analog force signal with the SCXI module the analog signal isn’t available to wire into a UMI. To my knowledge the conditioned signal of the SCXI resides only in the PXI backplane (i.e. there is no physical access to the conditioned analog signal). Can you explain how the UMI could be help here.
Again thanks for your input GG.
Patrick

Closed loop velocity control based on load cell force

Similar Messages

Maybe you are looking for