Overview

Description

The Position Error block output is equal to the Command Position - Actual Position of a specified axis. The update rate is updated as determined by the Evaluate Block.

Example

The most common use of the Position Error block is the primary input to a control loop. Here the Position Error is sent directly into the PID block.

The configuration values for this block are as follows:

Axis Number	The number of the axis which is the source of the position error data. This number may be absolute or linked to the Model Number.
Evaluate Block	This block allows you to specify whether the block executes Every Sample, Every Other Sample (Odd or Even), or Every Fourth Sample (and specify the First, Second, Third, or Fourth). This provides greater flexibility in controlling the execution of a model and to preserve performance for other areas of motion control.
User Defined Block Priority	When selected, allows you to enter a Priority Code to modify Execution Ordering of this block. For more information, see Block Execution Order and User Defined Block Priority.
Priority	For an explanation of how the Priority field is used by the MechaWare Model Downloader, see Block Execution Order and User Defined Block Priority.
User Data 0	Application-specific data. See User Data Storage.
User Data 1	Application-specific data. See User Data Storage.

Matlab/Simulink

Simulink Interface

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The sim (opt) input is an input which only relates to simulation.

Note: This input is only used when simulating within Simulink and is ignored when the model is downloaded to a controller.

By supplying a value from a Simulink source or a trajectory generator that passes the value through the model, will allow you to see how the system responds given a position error. Additionally, allows you to generate a torque command when using a PID or BiQuad block

The Output of the Position Error block is the Axis Position error value. The position error is the difference between the axis’s command position and actual position.

The Axis Number of the axis providing the position error data is determined by the Axis Number parameter. This number can be absolute or linked to the Model number.

The block has two user data fields (User Data 0, User Data 1) to store application-specific data for convenient storage and retrieval. See User Data Storage for details.

The block's update schedule is determined by the Evaluate Block. The following Parameter Dialog Box can be opened by double-clicking on the block in a Simulink Model:

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C++ API

POSITION_ERRORBlock

Declaration

Public Method

	class POSITION_ERRORBlock: public virtual Block { public: // User accessible coefficients };
	Required Header: mechaware.h

Description

The Position Error block is used to connect the inputs of a model

Methods

Block Methods