RS-485 Preamble Arbitration in Multi-Type Air Conditioner Networks
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Solution Overview
Problem
Conventional multi-type air conditioning systems using RS-485 communication face inefficiencies due to prolonged waiting times by slave units for communication line access, leading to reduced data transmission efficiency as the number of units increases.
Innovation Solution
Each unit in the air conditioning system independently sets communication priority by transmitting a preamble signal, randomly selecting a priority set time, and stopping transmission if another unit's signal is sensed, ensuring fair access to the communication line and preventing collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polling method is used where the master unit authorizes slave units to perform communication in order, then collision on the communication line is avoided, but the waiting time for slave units increases significantly as the number of slave units increases
Solution Approach 1:
The patent applies dynamics by allowing slave units to dynamically determine their transmission timing based on random backoff times rather than following a fixed polling sequence. Each slave unit calculates a random backoff time and transmits when its timer expires, creating a dynamic, adaptive communication schedule that responds to the actual number of slave units and their individual needs, thereby reducing waiting time while avoiding collisions.
Solution Approach 2:
The patent changes the parameter of transmission timing from a fixed sequential order to a randomized timing based on individual backoff calculations. By varying the transmission time parameter randomly for each slave unit, the system eliminates the prolonged waiting inherent in fixed polling while maintaining communication reliability through collision avoidance.
2Adaptability or versatility
If the master unit authorizes all slave units to perform communication once, then each slave unit can access the communication line, but the communication efficiency decreases as the number of slave units increases
Solution Approach 1:
The patent implements self-service by enabling each slave unit to independently determine its own transmission timing through random backoff calculation without requiring sequential authorization from the master unit. Each slave unit autonomously manages its communication access by calculating its backoff time and transmitting when appropriate, eliminating the inefficiency of centralized polling while ensuring all units can access the communication line.
3Reliability
If slave units stand by for a long time to occupy the communication line, then each unit can transmit data, but the overall data transmission speed decreases
Solution Approach 1:
The patent applies preliminary action by having each slave unit calculate and set its random backoff time in advance before attempting transmission. This preliminary timing determination allows each unit to know exactly when it will access the communication line, eliminating prolonged waiting while ensuring collision-free transmission. The backoff calculation is performed beforehand, and units simply execute the predetermined timing, thereby maintaining both reliability and speed.
Data Source
AI summary
A multi-type air conditioning apparatus including an outdoor unit, indoor units, and a communication line, each of the outdoor unit and the indoor units including a communicator transmitting/receiving data through the communication line and a controller transmitting at least one preamble signal, including priority information to transmit the data using the communication line, through the communication line, and transmitting the data through the communication line when transmission of the at least one preamble signal has been completed. In the multi-type air conditioning apparatus, each of the outdoor unit and the indoor units selects a priority set time, transmits a preamble signal after the selected priority set time has elapsed, and delays data transmission when a preamble signal transmitted by another constituent unit is sensed during the priority set time, thus avoiding collision on the communication line and rapidly occupying the communication line.