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Feedback

Mechaware API Documentation > Input

Overview

Overview

Description

The Feedback block is an Input block that is a source for position data. The output from the Feedback block is the Raw Encoder Feedback value (32-bit). The update rate is determined by the Subsample Code.

Because the Feedback block returns the Raw data (no offsets), this makes the Feedback block ideal for absolute position reference.

Example

The following example shows how to implement a cyclic error compensation based on actual position.Consider a scenario where an un-balanced pulley is spinning horizontally on a motor shaft. Gravity causes the imbalance to require more force to rotate the heavy side up, then require less force as the heavy side makes its way down.

By taking the Raw encoder feedback and setting the Modulo equal to the encoder resolution, the output of the Modulo will always be between Zero and the encoder resolution. We can then create a lookup table based on absolute motor angle, and output an extra torque command based on what angle the motor is at.


The following parameters are used to configure this block at load time:

 

Motor Number

The number of the axis which is the source of the position data. This number may be absolute or linked to the Model Number.

Encoder Number

The number of the encoder on the motor which is the source of the position. A value of 0 specifies the primary encoder, while a value of 1 selects the secondary encoder.

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

The Output of the Feedback block is the Raw Encoder Feedback value (64-bit) . This block has no inputs.

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

The Encoder Number parameter specifies which of the motor’s feedback devices to use.

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:

C++ API

FEEDBACKBlock

Declaration

Public Method

  
class FEEDBACKBlock: public virtual Block
{
public:
	// User accessible coefficients
};
 

Required Header: mechaware.h

Description

The Feedback block is used to connect the inputs of a model.

Methods

Block Methods

See Also

Memory
 Torque Output
Noise Generator MemoryOut
Actual Position Memory Out User Buffer
Command Position Scope
Position Error Feedback
Memory User Buffer Reset Status
Command Acceleration Test In
Command Velocity Test Out

 
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