Subscriber Station Deterministic Bus Access Without Master Node
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Solution Overview
Problem
Current bus systems, particularly in vehicles, face challenges in achieving deterministic communication while allowing for different communication standards and bit rates, especially at maximum bus utilization.
Innovation Solution
A subscriber station with a communication control device and a pause module that evaluates status information to generate a transmission delay signal, enabling deterministic bus access without a master node and allowing for 100% CAN bus utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PLCA method with master node is used for deterministic bus access, then determinism is achieved, but device complexity and functional safety risk increase due to master node requirement
Solution Approach 1:
The patent extracts the master node function from the system by implementing distributed deterministic bus access where each subscriber station independently calculates its transmission timing based on received frame timestamps, eliminating the need for a centralized master node while maintaining determinism
Solution Approach 2:
Each subscriber station serves itself by autonomously determining transmission slots based on timestamps from received frames, without requiring configuration by a master node or complex centralized control, thereby simplifying the system while achieving deterministic access
2Speed
If higher bit rate is selected on CAN bus, then data transmission speed improves, but bus utilization decreases and net data rate is limited
Solution Approach 1:
The patent implements dynamic bit rate switching between arbitration phase and data phase (CAN FD/CAN XL), where the bit rate is higher during data transmission and lower during arbitration, allowing maximum bus utilization while achieving high net data rates through adaptive rate adjustment
Solution Approach 2:
The system uses periodic arbitration phases interspersed with high-speed data phases, creating a rhythmic pattern of rate adjustment that maintains determinism during arbitration while maximizing throughput during data transmission cycles
3Adaptability or versatility
If CAN arbitration with CSMA/CR is used, then compatibility with existing systems is maintained, but deterministic bus access is not achieved
Solution Approach 1:
The patent segments the communication frame into arbitration phase and data phase with different characteristics, where arbitration uses traditional CAN methods for compatibility and data phase uses timestamp-based deterministic access for reliability, combining both requirements in a single system
Solution Approach 2:
The subscriber station implements multiple communication modes (Classical CAN, CAN FD, CAN XL) and deterministic access methods within a single device, allowing it to function as both a traditional CAN node for compatibility and a deterministic node for real-time requirements simultaneously
Data Source
AI summary
A subscriber station and method for deterministic communication in a serial bus system. The subscriber station has a communication control device for controlling a communication of the subscriber station by generating messages based on a frame and by transmitting the messages to a bus of the bus system and by evaluating at least one signal received from a bus of the bus system based on the frame, with which frame the bit time in a first communication phase can differ from a bit time in a second communication phase, and a pause module for evaluating at least one item of status information output by the communication control device, wherein the pause module is designed to generate and output a transmission delay signal based on a result of its evaluation, to delay or not to delay the provision of a transmission message to the communication control device.