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Sine sweep frequency response measurement


meindert.norg
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LS, I noticed a "Sine Sweep" function in the TuningPro software to measure frequency responses. However, it seems that the sine can only be 'injected' into the setpoint. In most applications, a servo can follow a (e.g.) 1 Hz sine-setpoint of (e.g.) 1000 increments, but not at 100 Hz. The result is that I can only measure very small frequency ranges in one measurement. One could solve this (I guess) by selecting several frequency ranges with decreasing amplitudes values, and 'merge' the measured results manually, but I have not tried this. Does Delta Tau have a tool available to measure frequency responses by injecting a sine or even noise into the controller output signal? Or even a tool that scales the injected signal based on the size of (e.g.) the following error or control effort? Thanks for your input. regards, Meindert
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If you are using pure DAC, you can easily inject adjustments to the servo loop output by modifying the DAC Bias (Ixx29). You can scale the adjustment based on control effort (Mxx68) or following error (Mxx61-Mxx62). You only must first obtain the initial DAC offset and store it in a P- or Q-Variable and then add it to whatever adjustment term you set in the DAC bias. It is recommended to use the PMAC Tuning Pro 2 software DAC Calibration tool to obtain this value (it will be placed in Ixx29). Here is an example of injecting bias scaled by the control effort: [code] I5 = 3 ; Foreground and Background PLCs on I8 = 0 ; Foreground PLCs at Servo Rate I15 = 0 ; Trig calcs in degrees #define DAC_Bias I129 // DAC Bias Term [18-bit DAC bits] #define Filter_Output M168 // Output of PID loop (control effort) [18-bit DAC bits] #define ServoCtr M100 // Servo clock counter of PMAC [servo cycles] #define FreqHz P8000 // Frequency of added sin bias [Hz] #define Initial_DAC_Bias P8001 // Offset to correct DAC output bias initially [18-bit DAC bits] #define Scale_Factor1 P8002 // Scale factor to add additional injection [18-bit DAC bits] #define Scale_Factor2 P8003 // Multiplies Filter Output Magnitude [18-bit DAC bits] #define Offset P8004 // Additional offset term (optional) [18-bit DAC bits] #define ServoCyclesPermsec P8005 // Servo cycles per millisecond conversion factor #define Phase P8006 // Phase offset in degrees Scale_Factor1 = 0 ; [18-bit DAC bits] Scale_Factor2 = 1 ; [18-bit DAC bits] Initial_DAC_Bias = -1674 ; From DAC Calibration tool ServoCyclesPermsec = 8388608/I10 ; servo cycles/ms FreqHz = 1 ; Hz Phase = 0 ; deg Offset = 0 ; Additional offset if needed Open PLCC 0 Clear DAC_Bias = (Filter_Output*Scale_Factor2+Scale_Factor1)*Sin(FreqHz*ServoCtr/ServoCyclesPermsec/1000*360 + Phase) + Offset + Initial_DAC_Bias Close [/code] This will inject a 1 Hz sine wave at the amplitude of the filter output. If you do #1J+ you should see a sine wave centered around the normal jog set point. You can play with the scale factors as desired. If you want to measure frequency response, you will have to dynamically change the FreqHz multiplier. You can gather and plot the motor position thereafter for your plots. Edited: Scaling within sine argument was previously incorrect. Should be correctly scaled to produce units of degrees now.
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Charles, Thanks for your answer. I appreciate the code examples very much, because for me that is an excellent way learn about the possibilities of the code. Do I understand correctly that there are currently no tools (like the trace and tuning tools) available to perform a frequency response measurement? Are there any plans in the making for making such a tool available? regards. Meindert
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There are many tools available for frequency response measurement in the PMAC Tuning Pro2 tool, which is a part of the Executive Pro2 Suite. In this tool, you can give a sinusoidal or sine sweep input to any of your motors, gather data on the response, and then perform a FFT to observe the characteristics of the response in the frequency domain. However, it does not allow you to inject a signal [i]over the top of[/i] whatever your motor is doing, like my example showed you. If you would like to add very strange, custom input signals to your motor, you will have to use the technique I described, or the technique using the compensation table bias register that Sina described in [url=http://forums.deltatau.com/showthread.php?tid=355]this post[/url]. Please refer to the manual for our Tuning software for additional details on the software: http://www.deltatau.com/manuals/pdfs/PMAC%20TUNING%20PRO.pdf?id=634272298135581611 If you still need help figuring out how to use the Tuning tool to perform your tests, please email us at support@deltatau.com your [b]specific[/b] questions, or call Technical Support at 818-717-5656.
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There are many tools available for frequency response measurement in the PMAC Tuning Pro2 tool, which is a part of the Executive Pro2 Suite. In this tool, you can give a sinusoidal or sine sweep input to any of your motors, gather data on the response, and then perform a FFT to observe the characteristics of the response in the frequency domain. However, it does not allow you to inject a signal [i]over the top of[/i] whatever your motor is doing, like my example showed you. If you would like to add very strange, custom input signals to your motor, you will have to use the technique I described, or the technique using the compensation table bias register that Sina described in [url=http://forums.deltatau.com/showthread.php?tid=355]this post[/url]. Please refer to the manual for our Tuning software for additional details on the software: http://www.deltatau.com/manuals/pdfs/PMAC%20TUNING%20PRO.pdf?id=634272298135581611 If you still need help figuring out how to use the Tuning tool to perform your tests, please email us at support@deltatau.com your [b]specific[/b] questions, or call Technical Support at 818-717-5656.
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There are many tools available for frequency response measurement in the PMAC Tuning Pro2 tool, which is a part of the Executive Pro2 Suite. In this tool, you can give a sinusoidal or sine sweep input to any of your motors, gather data on the response, and then perform a FFT to observe the characteristics of the response in the frequency domain. However, it does not allow you to inject a signal [i]over the top of[/i] whatever your motor is doing, like my example showed you. If you would like to add very strange, custom input signals to your motor, you will have to use the technique I described, or the technique using the compensation table bias register that Sina described in [url=http://forums.deltatau.com/showthread.php?tid=355]this post[/url]. Please refer to the manual for our Tuning software for additional details on the software: http://www.deltatau.com/manuals/pdfs/PMAC%20TUNING%20PRO.pdf?id=634272298135581611 If you still need help figuring out how to use the Tuning tool to perform your tests, please email us at support@deltatau.com your [b]specific[/b] questions, or call Technical Support at 818-717-5656.
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There are many tools available for frequency response measurement in the PMAC Tuning Pro2 tool, which is a part of the Executive Pro2 Suite. In this tool, you can give a sinusoidal or sine sweep input to any of your motors, gather data on the response, and then perform a FFT to observe the characteristics of the response in the frequency domain. However, it does not allow you to inject a signal [i]over the top of[/i] whatever your motor is doing, like my example showed you. If you would like to add very strange, custom input signals to your motor, you will have to use the technique I described, or the technique using the compensation table bias register that Sina described in [url=http://forums.deltatau.com/showthread.php?tid=355]this post[/url]. Please refer to the manual for our Tuning software for additional details on the software: http://www.deltatau.com/manuals/pdfs/PMAC%20TUNING%20PRO.pdf?id=634272298135581611 If you still need help figuring out how to use the Tuning tool to perform your tests, please email us at support@deltatau.com your [b]specific[/b] questions, or call Technical Support at 818-717-5656.
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[quote='meindert.norg' pid='1035' dateline='1294685799'] Do I understand correctly that there are currently no tools (like the trace and tuning tools) available to perform a frequency response measurement? Are there any plans in the making for making such a tool available? regards. Meindert [/quote] Delta Tau has an optional software product, the PMAC Servo Analyzer that is pretty much a full function DSA that can inject a swept sine or a burst chirp disturbance. Closed loop to open loop Bode plots are provided along with plant modeling. My only issue with it is that the injection point cannot be at the set point input, so it cannot tune the feed forward terms.
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Hi, It is not available on our website. Yes, there is a charge for the software.  Please contact your nearest distributor for the product: http://www.deltatau.com/common/sales/distributorsandintegrators.asp?connectionStr=release
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