Feedback Control Buffering for Variable Dead Time Loops
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Solution Overview
Problem
Existing control systems in factory automation face instability due to varying dead time in feedback control loops, particularly when using low-speed communication or sensors on conveyance devices, which requires a clock function to manage delay variations effectively.
Innovation Solution
A control system that includes a sensor, a sensor driver, and a control device with a buffer unit to store physical quantities based on transmission and reception sequence numbers, allowing for stable feedback control without relying on a clock function, by determining the number of elements in the buffer array based on the maximum delay period and incrementing sequence numbers for each control cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a clock function is used to manage delay variations in feedback control loops, then control stability can be maintained, but device complexity increases
Solution Approach 1:
The patent extracts the timing management function from a clock-based system and implements it using sequence numbers. The transmission sequence number added by the sensor driver and reception sequence number generated by the control device replace the need for clock synchronization, thereby maintaining control stability while eliminating the clock function requirement and reducing device complexity
Solution Approach 2:
The patent replaces the mechanical/time-based clock synchronization system with a data-based sequence number system. Instead of using time stamps and clock functions to track delays, the system uses incremental sequence numbers that are processed through buffer units, substituting a complex time-management mechanism with a simpler sequence-based approach
2Adaptability or versatility
If wired or wireless communication is used to connect control devices, then flexibility in system layout is improved, but dead time increases due to communication delay
Solution Approach 1:
The patent applies preliminary action by pre-allocating buffer units based on the maximum expected delay period before control cycles begin. The buffer unit size is determined in advance as (maximum delay period - minimum delay period + 1), allowing the system to accommodate communication delays without real-time clock adjustments, thus maintaining flexibility while managing dead time
Solution Approach 2:
The patent introduces dynamic indexing into the buffer unit using the formula: index = reception sequence number - transmission sequence number - minimum delay period + buffer start position. This dynamic indexing allows the system to adapt to varying communication delays in real-time without requiring clock synchronization, effectively managing dead time while preserving communication flexibility
3Device complexity
If sequence numbers and buffer units are used to manage delay variations, then device complexity is reduced, but memory requirements increase
Solution Approach 1:
The patent implements partial action by allocating buffer units only for the necessary range of delay variations. The buffer size is precisely calculated as (maximum delay period - minimum delay period + 1), which is the minimum required to handle delay variations. This avoids excessive memory allocation while still providing complete coverage for all possible delay scenarios, achieving a balance between memory efficiency and delay management capability
Data Source
AI summary
A control device configured to perform feedback control by transmitting a control signal to a target device based on a physical quantity of the target device measured by a sensor and a command value includes: a receiver configured to receive the physical quantity to which a transmission sequence number incremented for each control cycle is added in a sensor driver; a buffer unit configured to hold an array of a number of elements determined based on a maximum value of a number of delay periods; a control unit configured to generate the control signal based on the physical quantity and the command value; and a transmitter configured to transmit the control signal to the target device. The control unit increments a reception sequence number for each control cycle, stores the physical quantity at a storage position of an array determined based on the transmission sequence number and the reception sequence number, and generates the control signal based on the physical quantity stored in a storage position for control, and the command value.