Overview

Overview

The Sign block will output a value that depends on the sign of the input. The block will output a 1 if the sign of the input is greater than 0, 0 if the input is 0, and -1 if the input is less than 0.

The Sign block is often used to generate a Friction Feed Forward.

Example

In the following example the Sign block is added after Command Velocity (generate a -1 or 1 when moving) and sent into a Gain block. This Gain block is often called Kfff – the Friction Feed Forward Gain. This gain helps account for static friction in a machine, caused by seals, bearings, and surfaces.

The configuration values for this block are as follows:

 
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) or background. 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 Sign block will output a value that depends on the sign of the input. The block will output a 1 if the sign of the input is greater than 0, 0 if the input is 0, and -1 if the input is less than 0.

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

SIGNBlock

Declaration

Public Method

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

Description

The Sign block will output a value that depends on the sign of the input. The block will output a 1 if the sign of the input is greater than 0, 0 if the input is 0, and -1 if the input is less than 0.

Methods

Block Methods