Crankshaft Protocol Pulse Timing for Direction-Safe Zero-Crossing Output
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Solution Overview
Problem
Existing crankshaft position detectors face challenges in accurately determining the direction of a rotating object prior to triggering protocol pulses, leading to potential misinterpretation of speed and direction by the Electronic Control Unit (ECU), especially when direction changes occur rapidly.
Innovation Solution
An apparatus comprising a zero-crossing circuit, delay circuit, direction detection circuit, and logic circuit that triggers protocol pulses asynchronously at speed signal zero-crossings and delays the pulses to allow for direction detection, ensuring synchronous output based on detected direction, thereby preventing overlapping pulses and ensuring accurate protocol pulse transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If protocol pulses are triggered synchronously with clock edges, then the output timing is precise and consistent, but the system cannot accurately determine direction information before triggering pulses, leading to potential misinterpretation by the ECU
Solution Approach 1:
The system performs preliminary direction detection by sampling the direction signal before the protocol pulse is triggered. The ECU receives and stores this preliminary direction information, so when the pulse is triggered asynchronously, the direction context is already available, eliminating the need to wait for direction information after pulse triggering.
Solution Approach 2:
A buffer or memory element acts as an intermediary between the direction detection circuit and the pulse triggering mechanism. This intermediary stores the direction information temporarily, allowing the pulse to be triggered at the optimal moment (on clock edges) while the direction data is preserved and made available to the ECU without delay.
2Reliability
If protocol pulses are triggered asynchronously at zero-crossings, then direction information can be determined before pulse triggering, but the output timing becomes inconsistent and may cause jitter
Solution Approach 1:
The direction information is determined in advance at the zero-crossing point before the protocol pulse is triggered. This preliminary determination ensures that the ECU receives accurate direction context, allowing reliable interpretation of the asynchronous pulse without requiring complex post-pulse analysis.
Solution Approach 2:
The system replaces complex mechanical timing synchronization mechanisms with a software-based approach. The ECU uses timestamp recording and software timing calculations to handle asynchronous pulses, substituting hardware synchronization complexity with flexible software processing that achieves the same timing accuracy.
3Measurement precision
If direction detection is performed before pulse triggering, then accurate direction information is available, but overlapping pulses may occur during rapid direction changes
Solution Approach 1:
The system implements feedback by monitoring direction changes and using this information to control pulse generation. When rapid direction changes are detected, the feedback mechanism prevents overlapping pulses by adjusting the triggering logic, ensuring that each pulse corresponds to a valid, non-conflicting direction state.
Solution Approach 2:
The system takes preliminary anti-action by detecting potential overlapping conditions before they occur. When rapid direction changes are anticipated, the system preemptively adjusts pulse generation to prevent overlapping, rather than attempting to resolve conflicts after they occur. This proactive approach maintains pulse transmission reliability.
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
This solution enables asynchronous low-jitter switching even with low-frequency clocks, ensuring accurate speed and direction information transmission to the ECU, preventing misinterpretation and maintaining correct pulse frequency and length, thus enhancing the reliability of crankshaft position detection.
Implementation Method 1
The disc has teeth distributed evenly around the circumference. When the shaft rotates, the teeth pass by magnetic sensors providing speed and direction information. The speed is represented by a sine wave
Implementation Method 2
The direction is represented by a cosine wave. If there is a zero-crossing of the sine wave (speed signal), the cosine wave (direction signal) is sampled to determine the object's direction
Data Source
AI summary
An apparatus and corresponding method for outputting a protocol pulse based on a speed signal representing speed of an object. The apparatus includes a zero-crossing circuit, and a delay circuit. The zero-crossing circuit is configured to output the protocol pulse at a zero-crossing of the speed signal. The delay circuit is coupled to the output of the zero-crossing circuit and configured to delay the protocol pulse. A first edge of the protocol pulse is asynchronous with a clock, and a second edge of the protocol pulse is synchronous with the clock.