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Digital
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Analog
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Current Loop Tuning
Tuning with a PC and software makes current probes and oscilloscopes a thing of the past. A windows based PC and software slider bars makes for quick and optimal tuning.
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Current Loop Tuning
Factory current loop tuning is sufficient in about 90 percent of applications. However some applications require current loop tuning to get the absolute most from an analog drive.
Note: The digital velocity loop and digital position loop have surpassed analog performance. However, when it comes to raw bandwidth in the current loop, well tuned analog drives still hold a slight edge.
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Velocity and Position Loop Tuning
As with current loop tuning above, tuning the velocity is just as easy. Built in tools such as low pass filters and feedforward gains make tuning precise.
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Velocity Tuning
Analog drives can use an encoder or tachometer to achieve velocity loop performance on par with digital drives. For the most part, tuning is fairly simple using a potentiometer. Hall Velocity mode is a feature that is almost exclusively associated with analog drives. This mode is excellent for high speed velocity control.
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Position Loop Tuning
There is no question here. If you need the drive to close the position loop then a digital drive is in order.
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Position Loop Tuning
When using an analog drive, an external controller should be used to close the position loop. The highest bandwidth systems use an analog drive in current mode with a high end controller to close the velocity and position loops.
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Configuration
Digital drives are configured using interface software on a PC. A long list of configuration options make AMC drives universally compatible with different controllers, motors, I/O, and your application.
After configuration, just save the file. When you get a new drive just download the saved file into the new drive.
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Configuration
Analog drives are configured with Switches and Potentiometers. Some people may not be familiar with this, but our technical support department can help you configure a drive in a short amount of time. Once the proper switch and potentiometer settings are known then future assemblies will be easy to complete.
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Diagnostics
AMC digital drives have a built in oscilloscope which allows you to view signals not normally accessible on other drives. There is also a status screen that gives a simultaneous display of over 50 events.
The combination of the built in oscilloscope and status window have repeatedly proven themselves as invaluable diagnostic tools. These tools not only diagnose the drive but extend themselves to detect other system problems unrelated to the drive!
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Diagnostics
Analog drives can't indicate the exact reason for a fault. Fortunately, analog drives are fairly simple and are easy to troubleshoot. There is usually only a few reasons for a particular problem and a little deductive reasoning can quickly find the cause. Contact our technical support if you need help.
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I/O
The functionality of the Inputs and Outputs on digital drives is very configurable.
Inputs can be set for active high or active low and can be configured for many functions such as inhibit, limit switch, dynamic brake, etc.
Outputs can be set for active high or active low and can signal many events such as drive inhibited, over speed, over current, zero speed, position error, etc.
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I/O
The functionality of the Inputs and Outputs on an analog drives is fixed. Inhibit, fault, current monitor and velocity monitor pins are common.
If more functionality is desired then the I/O on the controller should be utilized.
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Commutation
Commutation applies to three phase brushless motors.
The two types of commutation are sinusoidal and trapezoidal. Digital drives are capable of both.
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Commutation
With a few exceptions, brushless analog drives commutate trapezoidally.
Sinusoidal commutation is smoother than trapezoidal, however trapezoidal is smooth enough for most applications.
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Conclusion
Deciding whether to use a digital drive or an analog drive really depends on what you need the drive to do. If you already have an intelligent controller that can handle events and it has enough I/O then either will work for your system. If your controller has limitations then a digital drive may be able to make up for them.
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