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Filter Tool

Overview

The Functionality of the Filter Tool that was a separate program has been integrated into the Bode Tool. Having the Filter Tool integrated into the Bode Tool allows the user to learn a single program and see changes in the filters in the Bode Tool plots.

How to use the Filter Tool

Opening the Filter Tool

The filter Tool is opened from the Bode Plot menu under Filter -> Filter Tool.

Simple Motor Setup

The setup tab in the filter tool allows simple configuration and management of the motor under test. It can do simple things, such as turning the servo on, that are needed when testing. Without the setup tab, separate programs are needed to do these functions.

Axis State - Shows the state of the motor as would be seen in Motion Console. This is commonly used to see that the motor is in an error state or idle state.

Clear Fault - Click this button to attempt clear an axis state.

Amp Enable - Shows whether the motor is enabled or not. Click the check box to toggle the amp enable status.

Error Limit - Sets the error limit trigger. This is the maximum counts of following error that are allowed before the error limit action is taken.

Error Action - This action is taken when Error Limit counts of following error occurs.

Contorl Algorithm - This is the control algorithm type (PID, PIV, etc.)

Polling Mode - If this is checked, the Setup tab is continually checking the status of all the values on the Setup tab. If an error is returned from the controller or communication with the controller is broken, this box becomes unchecked and the values are no longer updated. You can recheck this box if you remove the cause of the problem.

Accessing the different coefficient groups

The Filter Tool appears as a separate window. It can be left open while using other features of the Bode Tool. The Filter Tool can access PID, PIV, and biquad post filter coefficients via its tabbed interface. Click on the appropriate Tab to show the appropriate coefficients. The PID coefficients are shown below:

The biquad post filters are shown below:

Loading and Reading Coefficients

The Filter Tool does not constantly poll the controller to determine if any coefficients have changed. If you change any filter coefficients in another program, click the Read button to make the Filter Tool read the current filter coefficients.

Coefficients changed in the Filter Tool will not take effect until the Load button is clicked.

When either the Load or Read buttons are clicked, the Bode Plot window will update it's simulation

The coefficients are always loaded to and read from the filter number specified in the First Motor Number on the main Bode Tool page. An example is show below where the First Motor Number is 0.

Loading and Reading PID coefficients

Using the Fitler Tool is an easy way to read and write PID coefficients to the controller.

To read the current PID parameters on the controller, click the Read button on the Filter Tool. When you click the Read button, the Fitler Tool will get the current filter coefficients from the controller. If the coefficients have changed since the Filter Tool last read them, the coefficients will be updated on the screen. The Bode Plot window will update its plots to reflect the new data.

To change the current PID coefficients on the controller, edit one of the coefficients in the PID tab of the Filter Tool. When you are done making your changes, click the Load button to load your changed filter coefficients to the controller. The coefficients will not be changed on the controller until you click the Load button. If the coefficients have changed since the Filter Tool last read them, the coefficients will be updated on the screen. The Bode Plot window will update its plots to reflect the new data.

Loading and Reading biquad post filter elements

Using the Fitler Tool is an easy way to read from and write biquad post filter elements to the controller.

To read the current biquad post filter elements from the controller, click the Load button on the Post Filter tab in the Filter Tool. The current biquad post filter elements will be displayed in the Filter Tool under the Post Filter tab and updated plots will be displayed in the Bode Plot window.

To change the current biquad post filter elements on the controller, edit one or more of the edit boxed in the Post Filter tab of the Filter Tool, then click the Load button.

Background on biquad post filters

Biquad post filters can be intimidating to the uninitiated. In this section, we will cover how to specify the post filter elements you want in the Filter Tool. This section is not intended to cover what each filter type is and what it does. For that sort of background, see the MEIPostfilterSection data type documentation page on the Motion Engineering support site. (http://support.motioneng.com/Software-MPI/docs/Filter/DataType/postftrsect2.htm)

There are six cascaded biquads for each filter object in the standard XMP and ZMP firmware. Each cascaded biquad is called a section and is specified by number (0-5). The biquad sections always start at number 0 and increment until all used sections are specified. All sections are specified in a continuous order (i.e. you can not have section 3 if you do not have section 2) If you not using biquad post filters, you do not to specify any sections.

In the Filter Tool, you navigate through your filter's biquad post filter sections by section number. Any Section Type can be assigned to any Section Number.

The Section Type specifies the general behavior of the biquad post filter element. At the time of writing, there are eight Section Types (Unity, Single Order, Low Pass, High Pass, Notch, Resonator, Lead/Lag, and None). You can use any Section Type for any Section Number.

The five edit boxes below the Section Number and Section Type are for specifying the specific filter parameters. Two example are shown below.

The Low Pass filter only has one parameter - Corner Frequency in Hertz. The other four edit boxes are grayed out because they are not used in this type of filter.

The Resonator filter has three parameters - Center Frequency in Hertz, Bandwidth in Hertz, and Gain in dB.

Gains in the biquad post filters are specified in dB. Frequencies are specified in Hz.

Changing the Section Number

Since the biquad post filter elements must be specified with no empty section numbers between used section, theh Filter Tool reflects this.

When there are no sections loaded, the Filter Tool shows the 0 section and will not let you change to another section.

When the zero section is specified (specified before you look at it, or you specify it), you can click the up spin arrow on the section type to look at the next section. The filter tool will never let you look at a filter past an unspecified section.

Measured Filter Tab

The Measured Filter tab shows the tuning parameters used when the bode plot measurement was taken. If it is so desired, you can press the "Load to Controller" button to load these parameters to the controller again. There are a few common uses for this tab

• If you make a test, change parameters, and don't like the changes. You can press the "Load to Controller" button to return to the original tuning parameters loaded during the test.
• You can copy the text of the tab and copy it to another program to track your tuning paramters.

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