Liquid Food PLC Control for Parallel Recipe Execution
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Solution Overview
Problem
Single-threaded Programmable Logic Controllers (PLCs) are limited in executing food processing steps in parallel, leading to longer production times and inefficiencies in liquid food production, while multi-threaded devices lack high-reliability and robust control suitable for industrial environments.
Innovation Solution
A system and method that enable a single-threaded computer device, such as a PLC, to control food processing steps in parallel by using predefined control commands like START, RUN, CHECK, and END, allowing the processor to manage multiple steps concurrently through a signal interface with processing devices like valves and sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-threaded PLC is used for control, then high-reliability and robust control are achieved, but food processing steps cannot be executed in parallel leading to longer production time
Solution Approach 1:
The control program is segmented into multiple independent instruction lists, where each instruction list controls a specific food processing step. This segmentation allows the PLC to execute different instruction lists in parallel by utilizing idle processor cycles, thereby enabling parallel execution of multiple food processing steps while maintaining the reliability of single-threaded control architecture.
Solution Approach 2:
The PLC utilizes periodic polling and cyclic execution of instruction lists at different priorities. High-priority instruction lists are executed more frequently and with higher precedence, while lower-priority lists are executed during available time slots. This periodic action pattern enables parallel processing of multiple food processing steps while maintaining deterministic control reliability.
2Productivity
If a PC with multithreading is used for control, then parallel execution of food processing steps is enabled, but high-reliability and robust control in industrial environment is reduced
Solution Approach 1:
The invention copies the parallel processing capability into a single-threaded PLC by implementing multiple instruction lists that can be executed independently. Instead of relying on hardware multithreading, the system creates software-based parallel execution paths within the constraints of single-threaded architecture, achieving parallel functionality without sacrificing industrial control robustness.
3Device complexity
If sequential execution of food processing steps is used, then control simplicity is maintained, but production time increases and efficiency decreases
Solution Approach 1:
The control system dynamically adjusts the execution order and timing of instruction lists based on process requirements. The PLC can switch between sequential and parallel execution modes dynamically, allocating processor resources to different instruction lists based on their urgency and interdependencies, thereby reducing overall execution time without significantly increasing control program complexity.
Data Source
Figure 1~2B
Figure 2C~2E
Figure 2F~3
AI summary
A system for production of liquid food (P) comprises a food processing arrangement (2) and a computer device (3), e.g. a PLC. The computer device (3) sequentially executes a control program (5A) to control the food processing arrangement (2) to perform processing steps for producing the liquid food (P) from one or more ingredients in accordance with a predefined recipe. The program comprises command instructions that each allocates a respective processing step to a predefined control command among a predefined set. To enable parallelism, despite the sequential execution by the computer device (3), the set of control commands comprises a start command which is associated, by the computer device (3), with an action of: starting the food processing step that is allocated to the start command and proceeding, without waiting for the food processing step to be completed, to a subsequent instruction in the list of instructions.