Bicycle Sensor Signal Phase Analysis for Motor Assist Control
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Solution Overview
Problem
Bicycle control apparatuses face challenges in accurately determining the rotational speed of a rotating body, leading to inappropriate motor assist control when sensors detect different rotational speeds for the wheel and crank, potentially causing inefficient or inappropriate motor operation.
Innovation Solution
A controller is implemented to determine whether the detection targets of two sensors are the same rotating body by analyzing phase and period differences in their signals, as well as speed changes, to accurately control the assist motor based on the rotational speed detected by each sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a bicycle speed sensor is used to detect the rotational speed of the wheel, then the control apparatus can control the assist motor based on wheel speed, but the control apparatus cannot execute appropriate control when the sensor detects crank rotational speed instead
Solution Approach 1:
The system continuously monitors the output signals from the bicycle speed sensor and compares them against expected wheel speed characteristics. When the sensor signal indicates crank rotational speed instead of wheel speed, the controller detects this discrepancy and adjusts or disables motor assist accordingly, ensuring reliable control execution based on accurate sensor interpretation
Solution Approach 2:
The controller acts as an intermediary between the bicycle speed sensor and the assist motor control. It processes the sensor output, determines whether the signal reflects wheel or crank rotation, and accordingly controls the motor assist function, preventing inappropriate motor operation when the sensor detects the wrong rotating body
2Ease of operation
If the assist motor is controlled based on wheel rotational speed, then motor assist can be provided appropriately, but the system becomes complex when multiple sensors are introduced to determine detection targets
Solution Approach 1:
The bicycle speed sensor is designed to detect rotational speed of rotating bodies in general, not just wheels. The controller is configured to interpret the sensor output to determine whether it reflects wheel or crank rotation, allowing the same sensor to serve multiple detection purposes without requiring separate sensors for each function
Solution Approach 2:
The system uses the sensor's own output characteristics to self-identify what it is detecting. By analyzing the frequency and pattern of the sensor signal, the controller automatically determines whether the sensor is detecting wheel or crank rotation, eliminating the need for additional identification sensors or complex external determination systems
Data Source
AI summary
A bicycle control apparatus is provided that permits a determination of a rotating body to be detected of a sensor that outputs a signal that reflects the rotational speed of a rotating body, and a bicycle assist device equipped with this control apparatus. The bicycle control apparatus includes a controller that, based on an output of a first sensor for outputting a signal that reflects a rotational speed of a rotating body provided to a bicycle, and an output of a second sensor for outputting a signal that reflects a rotational speed of a rotating body provided to the bicycle, determines whether or not the detection target of the first sensor and the detection target of the second sensor are the same rotating body.