CAN Bus High-Frequency Modulation for Large Data Blocks
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Solution Overview
Problem
Current CAN bus systems face limitations in transmitting large data blocks efficiently under real-time conditions due to low bit rates and the need for bitwise arbitration, which can lead to interference and degradation of real-time properties when using existing protocols.
Innovation Solution
Implementing a high-frequency communication method over a shared signal line using a second channel, where data is modulated onto the existing CAN channel, allowing for higher bit rates without additional arbitration, and utilizing the TTCAN time window structure to ensure exclusive access and prevent collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bitwise arbitration is used for data transmission over the CAN channel, then real-time properties are improved, but the bit rate remains low and large data blocks cannot be transmitted rapidly
Solution Approach 1:
The patent segments the communication function into two distinct channels: the first channel (CAN bus) handles real-time control messages with bitwise arbitration, while the second channel (high-frequency modulated channel) handles large data block transmissions. This segmentation allows each channel to be optimized for its specific purpose without compromising the other's performance characteristics.
Solution Approach 2:
The patent adds a frequency dimension to the communication system by modulating a high-frequency carrier signal onto the CAN bus channel. This creates a second communication layer (second channel) that operates simultaneously with the original CAN protocol, enabling parallel data transmission at different bit rates for different message types.
2Productivity
If the communication interface is switched to a different mode for transmitting large data blocks, then the bit rate is increased, but the real-time properties are degraded due to interruption of CAN protocol communication
Solution Approach 1:
The communication interface is segmented into two parallel transmission modes operating simultaneously: standard CAN protocol transmission for real-time messages and high-frequency modulated transmission for large data blocks. This allows the system to maintain real-time communication capabilities while enabling high-speed data transfer without interrupting either mode.
3Productivity
If a second channel is added for high-frequency communication, then large data blocks can be transmitted rapidly, but the device complexity increases
Solution Approach 1:
The patent merges the high-frequency modulated channel with the existing CAN bus physical infrastructure. By modulating the carrier signal onto the same differential pair wires used for CAN communication, the system utilizes the existing physical medium for both channels, thereby reducing the need for separate hardware and minimizing the increase in device complexity.
Solution Approach 2:
The CAN bus channel is designed to serve dual functions: carrying both standard CAN protocol messages and high-frequency modulated data signals. This multi-functionality allows a single physical channel to support multiple communication modes, reducing the need for dedicated separate infrastructure for high-speed data transfer.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables rapid transmission of large data blocks while maintaining real-time conditions, increasing the bit rate of the CAN domain, and ensuring interference-free communication without requiring a separate media access control method, thus enhancing the operational efficiency of the bus system.
Implementation Method 1
a data signal and a signal modulated by the second data be generated as a function of the first data, and that the modulated signal be superimposed on the data signal
Data Source
AI summary
A method for transmitting data among subscriber stations of a bus system over a first channel of the bus system that is jointly used by a plurality of subscriber stations. To provide a method for the access by a subscriber station of the bus channel to a second channel of the bus system in parallel to a first channel that is jointly used by a plurality of subscriber stations; besides over the first channel, data are also transmitted over a second channel that is used by a plurality of subscriber stations, the access to the second channel being controlled by any given access method, and first data to be transmitted over the first channel and second data to be transmitted over the second channel being transmitted over a shared signal line.