Sensor Failure Detection in Battery-Assisted Bicycle Driving Units
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Solution Overview
Problem
Conventional battery-assisted bicycles face challenges in accurately detecting failures in assist control sensors, such as torque and rotation speed sensors, leading to reduced accuracy in determining sensor failures and subsequent assist control effectiveness.
Innovation Solution
A driving unit with an electric motor that includes a crankshaft, motor rotation detector, torque detector, crank rotation detector, and a sensor failure detector, which compares detection results from these sensors to accurately detect failures and improve assist control accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a torque detector is used to detect pedal effort, then assist control can be achieved, but failure detection accuracy is reduced when comparing torque sensor signals with rotation speed sensor signals
Solution Approach 1:
The patent introduces a pedal effort detector as an intermediary device that directly detects pedal effort applied to the crankshaft, independent of the torque detector and rotation speed sensor. This intermediary detection method provides a reference signal for comparing against the torque detector output, enabling accurate failure detection without being affected by the limitations of indirect measurement methods.
Solution Approach 2:
The system implements feedback by continuously comparing the pedal effort detected by the pedal effort detector with the torque detected by the torque detector. When inconsistencies are detected between these two independent measurement channels, the system can identify sensor failures and provide feedback to the control unit for appropriate error handling.
2Measurement precision
If multiple sensors are used for assist control, then control accuracy is improved, but device complexity increases
Solution Approach 1:
The pedal effort detector serves multiple functions: it directly detects pedal effort for assist control, provides a reference signal for failure detection, and enables comparison with torque detector readings. This multi-functionality reduces the need for separate dedicated components for each function, thereby managing system complexity while maintaining high measurement precision.
3Ease of operation
If torque detector and rotation speed sensor are used together, then pedal driving state can be determined, but failure determination accuracy is reduced due to inconsistent pedal driving states
Solution Approach 1:
The patent segments the pedal driving state detection into two independent channels: one based on torque detector signals and another based on rotation speed sensor signals. By processing these channels separately and then comparing their results, the system can identify inconsistencies that indicate sensor failures, thereby improving failure determination accuracy while maintaining ease of operation.
Data Source
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AI summary
A driving unit and a battery-assisted bicycle capable of accurately detecting a failure in each of a torque detector, a crank rotation detector, and a motor rotation detector is provided. The driving unit 40 includes a crankshaft 41 to which pedals 33 and 34 are to be connected, a motor rotation detector 68 that detects rotation of an electric motor 61, a torque detector 57 that detects a torque generated at the crankshaft 41, a crank rotation detector 58 that detects rotation of the crankshaft 41, and a sensor failure detector 106 that detects a failure in at least one of the motor rotation detector 68, the torque detector 57, and the crank rotation detector 58 based on detection results from the motor rotation detector 68, the torque detector 57, and the crank rotation detector 58.