Multi-Type Air Conditioner RS-485 Preamble Access Control
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Solution Overview
Problem
In multi-type air conditioning systems with RS-485 communication, as the number of slave units increases, they often wait excessively to occupy the communication line, leading to inefficiencies due to the polling method used.
Innovation Solution
Each unit sets its own communication priority by transmitting a preamble signal after a randomly selected priority set time, delaying data transmission if another unit's signal is sensed, thus avoiding collisions and rapidly occupying the line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the polling method is used in RS-485 communication environment, then collision on communication line is avoided, but when the number of slave units increases, the slave units stand by for a long time to occupy the communication line
Solution Approach 1:
The patent applies dynamics by making the communication method adaptive rather than static. Each slave unit dynamically selects a random backoff time before transmitting data, allowing the system to automatically adjust to varying numbers of slave units. This dynamic approach eliminates the need for manual polling configuration and reduces waiting time as slave units can independently access the communication line without being constrained by a fixed polling sequence.
2Stability of the object's composition
If the polling method is used, then communication order is controlled, but slave units must wait excessively to transmit data
Solution Approach 1:
The patent changes the parameter of communication access control from a fixed polling sequence to a randomized backoff mechanism. Each slave unit generates a random backoff time parameter before attempting transmission, which maintains communication stability through controlled randomness while significantly improving productivity by reducing idle waiting time. This parameter change allows multiple slave units to access the communication line more efficiently without causing collisions.
3Device complexity
If master unit authorizes all slave units to perform communication once, then communication is simplified, but slave units wait long time when number of slave units increases
Solution Approach 1:
The patent implements self-service by enabling each slave unit to independently determine its transmission timing without requiring continuous authorization from the master unit. Each slave unit autonomously selects a random backoff time and attempts transmission accordingly, eliminating the need for the master unit to manage communication scheduling. This self-service approach maintains simplicity while dramatically reducing standby time, as slave units no longer need to wait for master unit authorization cycles.
Data Source
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AI summary
A multi-type air conditioning system including a central control unit, an outdoor unit, indoor units, and a communication line, each of the central control unit, 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 system, 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.