Synchronous Sensor Timing Adaptation for PWM Frequency Variation
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Solution Overview
Problem
Sensor systems operating in synchronous mode face performance degradation due to non-deterministic trigger behavior caused by pulse width modulation (PWM) frequency variation, leading to delays and data loss, particularly at frequencies of 20 kHz or higher.
Innovation Solution
Sensors in synchronous mode adapt to PWM frequency variation by adjusting sampling points and transmitting latency compensation information, enabling synchronization maintenance and data transmission without additional jitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sensor operates in synchronous mode with fixed sampling points, then the data transmission timing is deterministic, but the system performance degrades when PWM frequency varies
Solution Approach 1:
The sensor dynamically adjusts its sampling points and internal timing based on detected PWM trigger intervals. The trigger level calculator continuously updates the internal trigger level value according to measured time intervals between consecutive PWM triggers, allowing the sensor to adapt its operation to varying PWM frequencies while maintaining synchronous mode benefits
Solution Approach 2:
The sensor implements a feedback mechanism where the actual trigger reception times are measured and used to recalculate expected trigger times for future cycles. The delay latency value and its deviation from target are calculated and transmitted back to the ECU, enabling the system to compensate for timing variations and maintain synchronization reliability
2Loss of time
If the sensor predicts trigger times based on fixed intervals, then the sensor tasks can be initiated in advance, but data loss occurs when PWM frequency changes
Solution Approach 1:
The sensor continues to initiate sensor tasks in advance based on predicted trigger times, maintaining the low-latency benefit of synchronous operation. However, the prediction is continuously updated using actual measured intervals from detected triggers, ensuring that the preliminary actions remain accurate even when PWM frequency changes occur
Solution Approach 2:
The feedback loop measures actual trigger intervals and recalculates expected trigger times, allowing the sensor to detect when PWM frequency changes have occurred. This feedback mechanism prevents data loss by adjusting predictions to match actual PWM timing, while still enabling advance task initiation to maintain low latency
3Device complexity
If the sensor uses fixed internal trigger levels, then the operation is simple and deterministic, but synchronization is lost when PWM frequency varies
Solution Approach 1:
The sensor changes the internal trigger level parameter dynamically based on detected PWM intervals. The trigger level calculator adjusts the internal trigger level value according to measured time intervals, allowing the system to maintain synchronization accuracy across varying PWM frequencies without requiring complex control logic
Solution Approach 2:
The feedback mechanism uses actual trigger detection to inform adjustments of the internal trigger level. This keeps the trigger control relatively simple while ensuring synchronization accuracy is maintained, as the adjustments are driven automatically by measured intervals rather than complex control algorithms
Data Source
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AI summary
In some implementations, a sensor may determine a delay latency value associated with an amount of time from completion of a set of sensor tasks to an actual time of reception of a trigger to selectively transmit or sample sensor data. The sensor may calculate a deviation of the delay latency value from a target delay latency. The sensor may transmit a data frame including an indication associated with the deviation of the delay latency value from the target delay latency.