Brainwords :
Memory Base (MB) = a database referring to a timestamp created with the same frequency of the raw data (minutes, second…)
Product Clone (PC) = a database referring to a physical thing (minutes lagged data aggregate to a product, one hour of energy consumption...)
You said Lag Time ?
What we call a Lag is the time spent between the beginning and the end of each step of the process.
It can be equal to zero if the operation is very quick (most of the time, less than 1 minute). If that is the case, the operation is then integrated in the next lag group.
Lag Time calculation can be done :
- with a fixed time, if we cannot compute it with process parameters
- with an algorithm, it will calculate the time difference between the output and the input
- with any parametric computation, defined regarding the specific process
How ?
A 𝚫t is calculated every line, with process parameters :
Current volume
- Tank Dimensions
- Current Level : sensor % or weight
Flowrate out
- Sensor reading
𝚫t :
Simplified Mathematical calculation : division
More accurate: Iterative summation
=> MX built-in operation
Example
At any time, all of the process values are known.
All values share a time on one line, Time is the index. This is the Time Domain
Issues in the Digester will not occur at the same time as issues in the Pulp or Paper Machine
Effects on an operation are staggered at different times depending on operation
Lag times allow us to shift lines based on operation to establish the Product Domain
=> Mapping operations from one index to another
Trouble shooting
Reasons that can lead to lag calculation dysfunction :
- one or more parameters are empty
Ex : For the output flow column, if there is no flow at time t, the operation will not run.
=> the column must contain "0" instead of empty - there is a data gap
Ex : There was a data extraction shutdown, and there is no data for a period of time, the operation will need x lines to return the first result after data gap
=> x number depends on lag duration, and how many lines the calculation has to "ride up" (See "How?" part on the top) - equipment has stopped, and produces a "freeze" of all the process steps ahead
Ex : a tank has its outflow to zero, the time spent in by the product is increasing, and the entry time is now constant
=> until the restart of the tank outflow, the values from the process above will be linked on this precise tank start time