Motion Run Axis Tuning (MRAT)

Use the Motion Run Axis Tuning (MRAT) to command the motion module to run a tuning motion profile for the specified axis. The tuning motion profile consists of one or more acceleration and deceleration ramps induced by applying fixed voltages to the servo’s drive output. Note that this instruction does not at any time close the servo loop. While this instruction takes no explicit input parameters, it does derive input from the Axis Tuning Configuration parameters. The result of executing the MRAT instruction is a set of measurement data that is stored in the Axis Object for subsequent use with the Motion Apply Axis Tuning (MAAT) instruction.

Available Languages

Ladder Diagram

Function Block

This instruction is not available in function block.

Structured Text

MRAT(Axis,MotionControl);

Operands

Ladder Diagram and Structured Text

See Structured Text Syntax for more information on the syntax of expressions within structured text.

Description - AXIS_SERVO, AXIS_SERVO_DRIVE

The MRAT instruction is used to execute a tuning motion profile on the specified axis. During this brief tuning motion profile, the motion module makes timing and velocity measurements that serve as input data for a subsequent Motion Apply Axis Tuning (MAAT) instruction. MRAT requires no explicit input parameters; simply enter or select the desired physical axis.

If the targeted axis does not appear in the list of available axes, the axis has not been configured for operation. Use the Tag Editor to create and configure a new axis.

The MRAT instruction uses axis configuration parameters as input and output. The input configuration parameters that MRAT uses are shown in this table.

Based on the above configuration parameters, MRAT execution generates a motion event on the specified axis that consists of a single triangular velocity profile or a series of three such profiles. Tune Velocity must be within the maximum speed capability of the drive and motor. The configured value for Tune Velocity should be set to the desired maximum operating speed of the axis so that the resulting tuning parameters are based on the dynamics of the system at that speed.

If the External Vel Servo Drive configuration bit parameter is TRUE, indicating interface to an external velocity servo drive, three pulses are applied to the axis. The tuning velocity profile for this case is shown in this diagram.

Tuning Velocity Profile when True

If the External Vel Servo Drive configuration bit parameter is FALSE, indicating interface to an external torque servo drive, only one pulse is applied to the axis. The tuning velocity profile is shown below.

Tuning Velocity Profile when False

The axis configuration parameters that MRAT generates as output depend on the External Drive configuration. If the External Vel Servo Drive configuration bit parameter is TRUE, indicating interface to an external velocity servo drive, these output parameters are generated.

If the External Vel Servo Drive configuration bit parameter is FALSE, indicating interface to an external torque servo drive, these output parameters are generated.

The above output parameters generated by the MRAT instruction serve as inputs to a subsequent MAAT instruction which performs further tuning calculations and applies the results to various axis’ servo and dynamic configuration parameters.

Description - AXIS_CIP_DRIVE

The MRAT instruction is used to execute a tuning motion profile on the specified CIP axis. MRAT requires no explicit input parameters; simply enter or select the desired physical axis.

If the targeted axis does not appear in the list of available axes, the axis has not been configured for operation. Use the Tag Editor to create and configure a new axis.

The MRAT instruction uses the CIP Axis configuration parameters as input and output. The input configuration parameters that MRAT uses are shown in this table.

The input configuration parameters can also be set using the

Axis Properties - Autotune

dialog box.

The Loop Response selection is used by the software to determine the value for the Damping Factor.

Based on the above configuration parameters, MRAT execution generates a motion event on the specified axis that consists of a triangular velocity profile. The tuning procedure will measure maximum acceleration and deceleration rates based on ramps to and from the Tuning Speed. Thus, the accuracy of the measured acceleration and deceleration capability is reduced by tuning at a speed other than the desired operating speed of the system.

The axis configuration parameters that MRAT generates as output for CIP axis are shown in this table:

The above output parameters generated by the MRAT instruction serve as inputs to compute the Position and Velocity loop gains, Position and Velocity Error Tolerances, Feed Forward Gains, Load Ratio, Maximum Acceleration, Maximum Deceleration, System Inertia, System Acceleration and Friction Compensation.

If the Gain Tuning Config Bits parameter bit zero is the Run Inertia Test Bit. This bit determines whether or not the MRAT tuning instruction will send a Test Inertia service to the drive to perform an inertia measurement. If this bit is set, the Inertia Test shall be performed. If the bit is clear, the MRAT will immediately complete without an inertia measurement. It will only calculate the Pos and Velocity Servo Loop Bandwidths based on the Loop response or the Damping factor.

Tune Status Parameter

Conditions may occur that make it impossible for the controller to properly perform the tuning operation. When this is the case, the tuning process is automatically aborted and a tuning fault reported that is stored in the Tune Status output parameter (GSVable). It is also possible to manually abort a tuning process using a Motion Axis Stop (MAS) instruction which results in a tuning fault reported by the Tune Status parameter. This table shows possible values for Tuning Status.

To successfully execute a MRAT instruction on an axis, the targeted axis must be configured as a Servo Axis Type, the axis must be in the Axis Ready state and Axis Test Mode must be disabled. If any of these conditions are not met then the instruction returns an error.

In this transitional instruction, the relay ladder, toggle the Rung-condition-in from cleared to set each time the instruction should execute.

Affects Math Status Flags

No

Major/Minor Faults

None specific to this instruction. A major fault can occur if an uninitialized reference or a reference of incorrect type is passed to the Axis operand. See Common Attributes for operand-related faults.

Execution

Ladder Diagram

Structured Text

Error Codes

See Error Codes (ERR) for Motion Instructions.

Extended Error Codes

Extended Error Codes provide additional instruction specific information for the Error Codes that are generic to many instructions. The following Extended Error Codes help to pinpoint the problem when the MRAT instruction receives an error message.

Status Bits

MRAT Changes to Status Bits

Example 1

When the input conditions are true, the controller commands the servo module to run a tuning motion profile for Axis1.

Ladder Diagram

Neutral Text for Ladder Diagram Normal Scan

MRAT (Axis1, MRAT_1);

Structured Text

MRAT(Axis1, MRAT_1);

Example 2

When the input conditions are true, the controller commands the servo module to run a tuning motion profile for Axis1 through a reference to it.

Ladder Diagram

Neutral Text Representation for RLL

MRAT(Ref_Axis1, MRAT_1);

Structured Text

MRAT(Ref_Axis1, MRAT_1);