Filter Objects

Filter Objects

Filters provide linkage between motors and axes: motors are mapped to filters, and filters are mapped to axes. (It is not possible to map a motor directly to an axis without a filter.) Depending upon the algorithm employed, filters use such coefficients as gains, feed forward and torque limits.

Filter Configuration Attributes

The Filter Summary window lists Filter attributes in two tab pages: "Config" and "Coeffs."

Configuration Attributes: "Config" Tab Page

"Config" Filter attributes include configurations for standard and custom filter features.

User Label – User-defined label for the object.

View Sub-objects – Shows all sub-objects for Filter object. For more information, see Object Summary Windows.

Algorithm – Software filter algorithm. There are five types:

None – Filter is OFF. No algorithm is applied.
PID – Proportional Integral Differential algorithm.
PIV – Proportional Integral Velocity.
PIV1 – Proportional Integral Velocity.
User – User-defined algorithm defined in firmware. (For more information, please contact MEI.)

Gain Switch Type – Used to switch filter parameters from the gain tables.

None – Gain switching is disabled.
Motion Only – Switch gains based on controller's switching algorithm.
Window – Requires custom firmware. Switch gains based on position window.
User – Requires custom firmware. Switch gains based on user criteria.

Gain Table – It specifies which gain table coeffs should be applied to the filter. Make sure Gain Switch Type is set to None before selecting a gain table. If the Gain Switch type is a type other than None, the controller will automatically index the gain table.

Gain Delay – Specifies the time (seconds) between the controller's calculated gain switch and the applied gain switch.

Gain Window – Requires custom firmware. It specifies the position window (counts) to apply the gain switch.

P/PI Switch Type – Requires custom firmware.

P/PI Mode – Requires custom firmware.

P/PI Delay – Requires custom firmware.

P/PI Window – Requires custom firmware.

Reset Integrator – Requires custom firmware.

Reset Int. Delay – Requires custom firmware.

Configuration Attributes: "Coeffs" Tab Page

The display of filter coefficients changes according to the Algorithm chosen (selectable from the Filter / General panel). The algorithm combo box on the Coeffs tab merely changes how the coefficients are displayed. It changes the row headers and displays N/A for coefficients that are not used for the selected algorithm. If the algorithm of a filter object does not match the algorithm being displayed, then N/A is displayed for all coefficients.

Each set of coefficients is described in separate tables below.

PID Coefficients

PID coefficients are defined in the table below. See MPIFilterGainPID. See the Scaling PID Tuning Parameters for Different Controller Sample Rates application note.

Filter Coefficients (PID Algorithm)

Coefficient	Description
Kp	Proportional gain
Ki	Integral gain
Kd	Derivative gain
Kpff	Position feed forward gain
Kvff	Velocity feed forward gain
Kaff	Acceleration feed forward gain
Kfff	Friction feed forward gain
ImaxMoving	Position loop integration maximum (while moving)
IMaxRest	Position loop integration maximum (while resting)
DRate	Derivative sub-sampling rate. See The PID Algorithm and DRate.
Output Limit High	Maximum command output voltage limit.
Output Limit Low	Minimum command output voltage limit.
Output Offset	Offset added to output.
Test Signal Gain	Fast Fourier transform (FFT) testing gain.

PIV Coefficients

PIV coefficients are described in the table below. See MPIFilterGainPIV.

Filter Coefficients (PIV Algorithm)

Coefficient	Description
Kpp	Position loop proportional gain
Kip	Position loop integral gain
Kpv	Velocity loop proportional gain
Kiv	Velocity loop integral gain
Kpff	Position feed forward gain
Kvff	Velocity feed forward gain
Kaff	Acceleration feed forward gain
Kfff	Friction feed forward gain
Vel Smoothing	Velocity estimate feedback gain
ImaxMoving	Position loop integration maximum (while moving)
IMaxRest	Position loop integration maximum (while resting)
VintMax	Velocity loop integration maximum
Output Limit High	Upper voltage command output limit.
Output Limit Low	Lower voltage command output limit.
Output Offset	Offset added to output
Kiv	Velocity loop integral gain
VintMax	Fast Fourier transform (FFT) testing gain
Test Gain Signal	Fast Fourier transform (FFT) testing gain (0)

None Coefficients

Selecting the None option means that no filter parameters will be used. This is common for stepper motors.

User Coefficients

These coefficients are used with a custom algorithm developed using the Firmware Development Kit.

All Algorithm Coefficients

Displays all coefficients for the different filter objects. Because different filter objects may use different algorithms, Motion Console must display generic labels rather than algorithm specific labels.

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