PLC Multicast Addressing for Response Timing
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Solution Overview
Problem
Existing communication protocols in PLC systems require time synchronization and address information for multicast communication, which complicates the process and increases the time needed for master devices to transmit requests to multiple slave devices, especially when devices have different processing speeds or malfunction.
Innovation Solution
A communication system that allows multicast communication without the need for time synchronization, where controlled devices detect and respond based on consecutive address ordering and response times, enabling efficient command transmission and response handling without prior knowledge of other devices' addresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If unicast communication is used to transmit requests to multiple slave devices, then each device can be addressed individually, but the time required for the master device to transmit requests to all slave devices becomes very long
Solution Approach 1:
The patent combines multiple unicast communication operations into a single multicast communication operation. The master device transmits a single request frame that is received by multiple slave devices simultaneously, eliminating the need for sequential unicast transmissions to each device. This merging of communication operations dramatically reduces the total request transmission time while maintaining accurate device identification through the response frame mechanism.
Solution Approach 2:
The patent segments the communication process into two distinct phases: a multicast request phase where the master device sends a single request to multiple slaves, and a segmented response phase where each slave device responds individually based on its address matching the request. This segmentation allows the master device to avoid waiting for responses from all devices before sending the next request, thereby reducing transmission time while maintaining address precision.
2Adaptability or versatility
If time synchronization mechanism is incorporated in slave devices to enable multicast communication, then multicast communication becomes possible, but the device complexity increases
Solution Approach 1:
The patent extracts the time synchronization mechanism from the slave devices and relocates it to the master device. The master device incorporates the time synchronization functionality to generate properly formatted request frames with timing information, while slave devices simply receive and process these frames based on their address matching the request. This extraction eliminates the need for complex time synchronization hardware or software in each slave device, reducing overall system complexity while maintaining multicast capability.
3Productivity
If each slave device needs to know address information about other slave devices in advance, then response timing can be coordinated, but the ease of operation deteriorates
Solution Approach 1:
The patent implements a self-service mechanism where slave devices automatically determine their response timing based on their own address and the request frame content, without needing to know or be configured with information about other devices. Each slave device independently compares its address with the target address in the request frame and responds accordingly. This self-service approach eliminates the need for complex pre-configuration of inter-device address information while maintaining efficient response coordination.
Data Source
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AI summary
A communication system comprising a programmable logic controller and a plurality of controlled devices connected to the programmable logic controller, wherein respective addresses have been assigned to the plurality of controlled devices in accordance with a predetermined rule and wherein when the programmable logic controller multicasts a request directed to the controlled devices, the plurality of controlled devices having received the request multicast respective responses to the request in an order determined on the basis of a predetermined rule.