Nested CAN Light Head Network for Simpler Vehicle Light Bar Wiring
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Solution Overview
Problem
Existing light bar wiring technologies are complex and prone to installation errors due to numerous wires and light heads, leading to increased assembly and production costs, and lack efficient methods for individual serial connections to each light head.
Innovation Solution
A serial light bar architecture utilizing a primary CAN serial data bus as a single node and a secondary nested CAN serial data bus to control multiple light heads, reducing wiring complications and enabling real-time diagnostic messaging and self-identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If discrete wire connections are used for each light head, then individual control capability is achieved, but wiring complexity and assembly time increase significantly
Solution Approach 1:
The patent replaces the mechanical wiring system (discrete wire connections) with an electrical communication system (CAN bus serial communication). Each light head is equipped with a microcontroller that communicates over the CAN bus, eliminating the need for complex discrete wire harnesses while maintaining individual control capability through digital messaging.
Solution Approach 2:
The CAN bus serves multiple functions simultaneously: it provides individual addressing for each light head, enables serial communication for control signals, and supports diagnostic capabilities. This single communication infrastructure replaces multiple dedicated wire connections, achieving wiring simplification without sacrificing control granularity.
2Adaptability or versatility
If more wires are added to each light head for different illumination-control signals, then control functionality is enhanced, but installation errors and assembly time increase
Solution Approach 1:
Multiple illumination control signals that would traditionally require separate wire connections are instead transmitted as digital messages over the single CAN bus. The microcontroller in each light head interprets these messages and activates the appropriate illumination patterns, reducing wiring while maintaining versatile control functionality.
Solution Approach 2:
The system performs preliminary configuration and self-identification during assembly, allowing for automatic verification of connections and functionality. This reduces manual testing time and enables quicker assembly since the system can automatically detect and configure light head arrangements without extensive manual intervention.
3Device complexity
If serial bus technology is used with external-facing interface only, then wiring is simplified, but individual serial connections to each light head are not achieved
Solution Approach 1:
The system segments the light bar into individually addressable light heads, each with its own microcontroller and CAN bus interface. This segmentation allows each light head to be independently controlled via serial communication while maintaining the wiring simplicity of a single bus structure. The external-facing serial interface communicates with each segmented unit individually through the shared bus.
Solution Approach 2:
The CAN bus acts as an intermediary between the external serial interface and individual light heads. The external interface communicates over the CAN bus, which then distributes messages to the appropriate light heads based on their addresses. This intermediary enables individual serial connections without requiring separate physical wires to each light head.
4Speed
If high baud rates are used for serial communication, then communication speed is improved, but signal integrity and node count limitations become concerns
Solution Approach 1:
The system uses excessive termination resistors (120 ohms) at both ends of the CAN bus to ensure signal integrity even at high baud rates. This over-termination provides a safety margin that compensates for variations in cable length, connector quality, and environmental factors, maintaining reliable communication throughout the light bar assembly.
Data Source
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AI summary
An array (166, 184, 194, 230, 256) of multiple light heads (170, 186, 194, 236) for a vehicle (100) has a primary Controller Area Network (CAN) serial data bus (108, 224) to carry first serial communications among spaced-apart CAN nodes (112, 118, 130, 136, 140, 154, 220, 260, 288) communicatively coupled thereto. The first serial communications initiate a flash sequence from the array via second serial communications provided to the multiple light heads communicatively coupled to a nested CAN serial data bus (180, 190, 200, 238). An array controller (130, 136, 140, 220, 260) segregates the nested CAN serial data bus from the primary CAN serial data bus while providing a communications bridge between nodes of the two buses. Accordingly, light heads on the nested bus provide self-identification and diagnostic information to other nodes such as a computer (288) configuration utility (290) featuring a graphical user interface (292).