Pfixread6 - Fixed Precision (6 dps) Parameter Read

This function block reads a fixed precision number from a specified parameter.

Note that if there is an error reading a parameter, e.g. the parameter does not exist, the drive will not be tripped. Instead an error code will be returned in Stat%.

Arguments

Parameter%

The parameter to be read in the form MMPP, e.g. 0511 = #05.11.

Return Values

Value%

The fixed precision parameter value. The precision is set at 6 decimal places, i.e. if a parameter has a value 1.23 then Value% will be 1230000. Likewise if a parameter is a round 87, then Value will be 87000000.

DPos%

The number of decimal places in the parameter. If the parameter is in the format #.## (as shown on the drive keypad) then DPOS will be 2 since there are two decimal places. Integer parameters will clearly have a DPOS of 0.

Stat%

Returns the status of the read. Unlike normal parameter reads using # or #INT, there will be no drive trip if something goes wrong. Instead, the field will indicate if there was a problem..

Example

Target/ Language Restrictions

None.

See Also

• PFIXREAD

• PFIXWRITE

• PFIXWRITE6

• CONDPARW

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Pfixwrite - Fixed Precision (3 dps) Parameter Write

This function block writes a fixed precision number to a specified parameter.

Note that if there is an error writing a parameter, e.g. the parameter does not exist, the drive will not be tripped. Instead an error code will be returned in Stat%.

Arguments

Param%

The parameter to be written in the form MMPP, e.g. 0511 = #05.11.

Value%

The fixed precision parameter value. The precision is set at 3 decimal places, i.e. if the desired parameter value is 1.23 then Value% should be passed as 1230.

Return Values

Stat%

Returns the status of the write. Unlike normal parameter writes using # or #INT, there will be no drive trip if something goes wrong. Instead, the field will indicate if there was a problem.

Example

Target/ Language Restrictions

None.

See Also

• PFIXWRITE6

• PFIXREAD

• PFIXREAD6

• CONDPARW

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Pfixwrite6 - Fixed Precision (6 dps) Parameter Write

This function block writes a fixed precision number to a specified parameter.

Note that if there is an error writing a parameter, e.g. the parameter does not exist, the drive will not be tripped. Instead an error code will be returned in Stat%.

Arguments

Param%

The parameter to be written in the form MMPP, e.g. 0511 = #05.11.

Value%

The fixed precision parameter value. The precision is set at 6 decimal places, i.e. if the desired parameter value is 1.23 then Value% should be passed as 1230000.

Return Values

Stat%

Returns the status of the write. Unlike normal parameter writes using # or #INT, there will be no drive trip if something goes wrong. Instead, the field will indicate if there was a problem.

Example

Target/ Language Restrictions

None.

See Also

• PFIXWRITE

• PFIXREAD

• PFIXREAD6

• CONDPARW

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Pid - pid Block

This function block provides the classic control used in closed-loop regulation, subject to external disturbances. Example uses are for temperature, flow, pressure, level, tension, etc.

Arguments

Ref%

Reference. Target to reach.

Feedback%

System feedback.

PGain%

Proportional gain.

IGain%

Integral gain.

DGain%

Derivative gain.

FiltT%

Time constant derivative filter.

LLim%

PID lower limit.

HLim%

PID upper limit.

Ctrl%

Integrator control.

Return Values

Q%

PID Output.

Error%

Error. Ref% - Feedback%.

LimHit%

Flag to signal if limit is hit.

PID Description

The reference represents the value to be reached (demand) and the feedback is the current value of this parameter (process variable). The difference between these values is known as the error. The output goes to a process to be regulated and its feedback is re-injected in the PID. The speed of execution would be defined with a external slew rate on the reference input added by the user if necessary (equivalent to a sample rate of the error).

A PID needs three coefficients to be set up: Kp (proportional gain), Ki (integral gain) and Kd (derivative gain). To change these coefficients would change the behaviour of the PID in terms of speed response and variability. Two limits (low and high) will be set up to define a working area within the PID is operational. If the output crosses one of the limits, the PID will clamp it till the output is again between the limits. These limits will stop the integrator being increased until the integrated error is back in the permit area.

The PID block is an integer PID only (working with integer inputs/outputs). It has asymmetrical limits and two separate inputs for the feedback and the reference (error is accessible as an output). The three gains (Pgain, Dgain and Igain) are defined as fixed point inputs (a value of 1000 represents a gain value of 1.000). The two limits are entered as integer values (negative values including the negative sign, not absolute values).

The derivative term has got a first order filter. The time constant of this filter, FilterTC, will be greater than 1 to the filter to be active (<1, filter non active).

The Ctrl (Integrator Control) input selects the current mode of the integrator. It works with a bit field checking:

• all bits = 0,Normal mode, continuous integration.

• bit 0=1: Hold mode, the current integrator value is hold as long as this mode is active.

• bit 1=1: Reset Mode, reset the integrator.

For example, to produce a reset Ctrl signal, enter 2 (binary 10).

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