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IDCON Example - Car Velocity Model
Info: Please click on the pictures to enlarge them.
Lets consider we want to determine a car velocity model based upon Input throttle, (or "Gas Pedal") position. We have measured both the input and output data from a small test, and now we want to determine a transfer function model for this system.
1. Collect the Data
In this example, the input and output data is being generated via a Simulink model. We have developed a system for the "Gas Pedal" input and also one for the vehicle's speed. To make it a little more "interesting" and "real-life", we have added noise to the Gas Pedal input , (not just to the measured input), and also to the measured output speed The output from the MATRIXx/SystemBuild model is shown below:
As you can see, the data we have obtained, ( 90 seconds of data @ sample rate of 10 Hz), is modestly noisy, and is not just a simple "step" test. The other thing you notice, is this data is not from a model of a F1 car, more like a small city car, ( 0-60 MPH in 25 seconds, pretty slow!)
2. Identify the system
Now lets use the IDCON Classic for LabVIEW Tool, to take our input and output data and identify a transfer function model of the system.
Once the data is loaded we can go and define the parameters of the desired system we are trying to identify and also options used in the identification process. The following Menu appears and we can specify information about the order of the numerator and denominator, whether the system has pure integrating components, or contains pure time delays, and if any of the states initial conditions were non-zero.
In this system, we choose the order of the numerator or denominator to be 0 and 2 respectively. The system has no pure integrating part that we know of, and the data was collected from zero initial conditions (stationary at t=0). Also, we know that there is no pure time delay in the system (Check Time Delay remains unchecked).
Now we can run the identification process by pushing the "Init" and the "Improve" pushbuttons. After few iterations, the result is available and shown in the menu.
As we can see we have a very good fit with the noisy data. We can also look at the step response or Bode Plot of the identified system at this point.
The model transfer function coefficents are shown as well, along with quality of fit information.
From the system response and fit with the original data, you must say we have a very good fit, and with a very low order system.
Oh by the way, the transfer function used in the "Car Model" in the MATRIXx/SystemBuild model, is as shown below:
As you can see, IDCON Classic for LabVIEW Tool did very well, even with all that noise!
3. Controller Design
We can transfer this model into a state space system, or use the transfer function directly in a MATRIXx/SystemBuild model for further simulation studies. Alternatively we could continue on the process and design say a cruise controller for this vehicle. We can do this very easily with another LabVIEW based Tool that is part of the ExpertControl range, the Automatic Controller Design Tool for LabVIEW, ACD Tool.
Let's now go to the Automatic Controller Design Example, to continue the process of defining a cruise control.
Back to IDCON Classic Tool Page
Lets consider we want to determine a car velocity model based upon Input throttle, (or "Gas Pedal") position. We have measured both the input and output data from a small test, and now we want to determine a transfer function model for this system.
1. Collect the Data
In this example, the input and output data is being generated via a Simulink model. We have developed a system for the "Gas Pedal" input and also one for the vehicle's speed. To make it a little more "interesting" and "real-life", we have added noise to the Gas Pedal input , (not just to the measured input), and also to the measured output speed The output from the MATRIXx/SystemBuild model is shown below:
As you can see, the data we have obtained, ( 90 seconds of data @ sample rate of 10 Hz), is modestly noisy, and is not just a simple "step" test. The other thing you notice, is this data is not from a model of a F1 car, more like a small city car, ( 0-60 MPH in 25 seconds, pretty slow!)
2. Identify the system
Now lets use the IDCON Classic for LabVIEW Tool, to take our input and output data and identify a transfer function model of the system.
Once the data is loaded we can go and define the parameters of the desired system we are trying to identify and also options used in the identification process. The following Menu appears and we can specify information about the order of the numerator and denominator, whether the system has pure integrating components, or contains pure time delays, and if any of the states initial conditions were non-zero.
In this system, we choose the order of the numerator or denominator to be 0 and 2 respectively. The system has no pure integrating part that we know of, and the data was collected from zero initial conditions (stationary at t=0). Also, we know that there is no pure time delay in the system (Check Time Delay remains unchecked).
Now we can run the identification process by pushing the "Init" and the "Improve" pushbuttons. After few iterations, the result is available and shown in the menu.
As we can see we have a very good fit with the noisy data. We can also look at the step response or Bode Plot of the identified system at this point.
The model transfer function coefficents are shown as well, along with quality of fit information.
From the system response and fit with the original data, you must say we have a very good fit, and with a very low order system.
Oh by the way, the transfer function used in the "Car Model" in the MATRIXx/SystemBuild model, is as shown below:
As you can see, IDCON Classic for LabVIEW Tool did very well, even with all that noise!
3. Controller Design
We can transfer this model into a state space system, or use the transfer function directly in a MATRIXx/SystemBuild model for further simulation studies. Alternatively we could continue on the process and design say a cruise controller for this vehicle. We can do this very easily with another LabVIEW based Tool that is part of the ExpertControl range, the Automatic Controller Design Tool for LabVIEW, ACD Tool.
Let's now go to the Automatic Controller Design Example, to continue the process of defining a cruise control.
Back to IDCON Classic Tool Page
