ABSROT – Processing data from absolute position sensor

Block SymbolLicensing group: ADVANCED
PIC

Function Description
The ABSROT function block is intended for processing the data from absolute position sensor on rotary equipment, e.g. a shaft. The absolute sensor has a typical range of 5 to 355 (or -175 to +175) but in some cases it is necessary to control the rotation over a range of more than one revolution. The function block assumes a continuous position signal, therefore the transition from 355 to 5 in the input signal means that one revolution has been completed and the angle is in fact 365.

In the case of long-term unidirectional operation the precision of the estimated position y deteriorates due to the precision of the double data type. For that case the R1 input is available to reset the position y to the base range of the sensor. If the RESR flag is set to RESR = on, the irev revolutions counter is also reset by the R1 input. In all cases it is necessary to reset all accompanying signals (e.g. the sp input of the corresponding controller).

The MPI output indicates that the absolute sensor reading is near to the middle of the range, which may be the appropriate time to reset the block. On the other hand, the OLI output indicates that the sensor reached the so-called dead-angle where it cannot report valid data.

Inputs

u

Signal from the absolute position sensor

double

R1

Block reset

bool

Outputs

y

Position output

double

irev

Number of finished revolutions

long

MPI

Mid-point indicator

bool

OLI

Off-limits indicator

bool

Parameters

lolim

Lower limit of the sensor reading  -3.141592654

double

hilim

Upper limit of the sensor reading  3.141592654

double

tol

Tolerance for the mid-point indicator  0.5

double

hys

Hysteresis for the mid-point indicator

double

RESR

Flag for resetting the revolutions counter

bool

off ..

Reset only the estimated position y

on ...

Reset also the irev revolutions counter

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