HVAC Subnet Heartbeat Control for Controller Recovery

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Solution Overview

Problem

Conventional HVAC systems lack advanced control and data acquisition techniques, leading to inefficiencies in installation, operation, and maintenance, and require more sophisticated methods for system recovery and communication among components.

Innovation Solution

The implementation of a distributed-architecture HVAC network with subnet controllers that generate and detect heartbeat messages, allowing for active and inactive controllers to communicate and manage system states, enabling improved communication, self-diagnosis, and system recovery.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional HVAC systems use basic thermostat control, then the system structure remains simple, but system reliability and communication capability deteriorate

Engineering Contradiction:

Improvesystem reliabilityVSAvoidsystem structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The HVAC system is divided into multiple subnets with subnet controllers that independently manage communication and control functions. Each subnet controller operates autonomously within its subnet, improving system reliability by isolating failures to specific subnets while maintaining overall system functionality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Subnet controllers continuously send heartbeat messages before actual control actions are needed. This preliminary communication establishes baseline system status and enables faster detection of controller failures, improving reliability without requiring complex real-time monitoring infrastructure.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If subnet controllers continuously communicate heartbeat messages, then system communication and reliability improve, but energy consumption increases

Engineering Contradiction:

Improvesystem communication reliabilityVSAvoidcontroller energy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

Heartbeat messages are transmitted at periodic intervals rather than continuously. The heartbeat message timer generates messages at predetermined time intervals, reducing communication overhead and energy consumption while maintaining sufficient monitoring capability to detect controller failures.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The system uses feedback from received heartbeat messages to determine whether controllers are operational. When a controller fails to send a heartbeat message within the expected interval, other controllers detect the failure and initiate arbitration, enabling reliable operation with reduced communication frequency.

Inventive Principle:

Principle #23Feedback

3Adaptability or versatility

If multiple subnet controllers operate on the same subnet, then system flexibility and redundancy improve, but communication conflicts and control stability worsen

Engineering Contradiction:

Improvesystem flexibilityVSAvoidcontrol stability

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

Controllers perform preliminary arbitration to determine active status before executing control functions. The arbitration process establishes a single active controller per subnet in advance, preventing control conflicts while allowing multiple controllers to remain in standby, thus maintaining both flexibility and stability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Heartbeat messages serve as an intermediary mechanism that mediates controller interactions. By exchanging heartbeat messages, controllers indirectly communicate their operational status and trigger arbitration when needed, resolving potential conflicts without direct controller-to-controller negotiation.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Ease of repair

If heartbeat message detection is implemented, then system self-diagnosis capability improves, but detection precision requirements and system complexity increase

Engineering Contradiction:

Improvesystem self-diagnosis capabilityVSAvoiddetection mechanism complexity

Core Design Contradiction:

Ease of repairVSDevice complexity

Solution Approach 1:

The system performs self-diagnosis by monitoring the absence of heartbeat messages from controllers. When a controller fails to send expected heartbeat messages, other controllers automatically detect the failure and initiate arbitration, enabling self-healing without external intervention or complex diagnostic tools.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The system uses simple, lightweight heartbeat messages rather than complex diagnostic protocols. These minimal communication packets are sufficient to detect controller status and trigger recovery actions, keeping the detection mechanism simple while maintaining effective self-diagnosis capability.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Data Source

PatentUS8255086B2System recovery in a heating, ventilation and air conditioning network

Publication Date: 2012.08.28 LENNOX IND INC

AI summary

The disclosure provides various embodiments of systems and methods of generating a heartbeat in an HVAC system and networks. In an embodiment, a method includes a heartbeat message being sent by a first subnet controller upon the first subnet controller taking active control of a subnet of the HVAC network. The active heartbeat message timer is reset. Another heartbeat message is sent if a specified amount of time has elapsed since a previous heartbeat message was sent by said heartbeat generator.