L9P_RAMP: Ramp to Set Point at a Constant Rate
(Original Document)
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Function Description
The L9P_RAMP DFB allows you to ramp up linearly to a target set point at a specified approach rate.
You need to specify:
The direction of the ramp depends on the relationship between the target set point and the input, i.e. if x < SP, the ramp is up; if x > SP, the ramp is down.
You may use a flag to initialize after an undetermined down-time. The DFB will store a new sample, then wait for one cycle to collect the second sample. Calculations will be skipped for one cycle and the output will be left as is, after which the ramp will resume.
L9P_RAMP terminates when the entire ramping operation is complete (over multiple scans).
Starting the Ramp
The following steps need to be done when starting the ramp (up/down) and each and every time you need to start or restart the ramp.
Step
Action
1
Set bit 1 of the standard input bits to "1".
2
Retoggle ENABLE. Ramp will now start to ramp up/down from the initial value previously configured up/down to the previously configured setpoint. Monitor output (word 13+14) for floating point value of the ramp value in progress.
Representation
Parameters
Input Pin
Name
Data Type
Address Range
Meaning
Top
ENABLE
BOOL
–
ON = enables process control function
Node
Node Type
Name
Data Type
Address Range
Meaning
Middle
IN/OUT
PAR
ARRAY[1...14] OF UINT
%MW
see Parameter PAR below
Bottom
IN
LEN
UINT
14
length of parameter block (can not be changed)
Outpin Pin
Name
Data Type
Address Range
Meaning
Top
OUT
BOOL
–
ON = operation successful
NOTE: The parameter OUT of L9P_RAMP goes active at each successive scan when performing the ramp calculations. Bit 6 of PAR.Output_Status provides the "Ramp done bit" state to indicate the RAMP operation is complete.
Bottom
ERR
BOOL
–
ON = operation not successful
Parameter PAR
The data type of the parameter block is ARRAY[1...14] OF UINT.
Word
Content
Format
1, 2
set point (input)
REAL (Floating Point)
3
output status
UINT
4
input status
UINT
5
time word
UINT
6
reserved
UINT
7, 8
time (in ms) since last solve
DINT
9, 10
solution interval (in ms)
DINT
11, 12
rate of change (per second) towards set point
REAL (Floating Point)
13, 14
output
REAL (Floating Point)
Output Status
Control Expert-IEC bits
Function
0...7
standard output bits (flags)
8
1 = ramping up
9
1 = ramping down
10
1 = ramp complete
0 = ramp in progress
11
1 = ramp rate is negative
12...15
not used
Input Status
Control Expert-IEC bits
Function
0...11
not used
12...15
standard input bits (flags)