Bicycle Motor Mounting Angle Compensation via Gyro Sensor Calibration

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Solution Overview

Problem

Existing electric power assist devices for bicycles face challenges in achieving proper power assist control due to variations in the angle at which the device is mounted, leading to errors in crank rotational angle detection and subsequent power assist control.

Innovation Solution

An electric power assist device with a tilt angle detector, such as a gyro sensor, and a calibrator that adjusts the absolute angle detected by the rotational angle sensor, allowing for proper power assist control regardless of the mounting angle, along with features like visible marks for alignment and a position sensor for automatic confirmation of the rotational position.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the electric power assist device is mounted at different angles on bicycles, then the device can be universally applied to various mounting configurations, but errors in crank rotational angle detection occur due to mounting angle variations

Engineering Contradiction:

Improvemounting angle adaptabilityVSAvoidcrank rotational angle detection accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

A tilt angle detector is introduced as an intermediary device to measure the mounting angle of the electric power assist device. The detected tilt angle is then used by the control unit to calculate a correction value that compensates for the mounting angle variation, thereby maintaining accurate crank rotational angle detection regardless of mounting orientation

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The control unit dynamically adjusts the absolute angle parameter of the crank rotational angle based on the detected tilt angle. By changing the angle parameter according to the mounting orientation, the system maintains measurement accuracy across different mounting configurations

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If a tilt angle detector and calibrator are added to compensate for mounting angle variations, then crank rotational angle detection accuracy is improved, but device complexity increases

Engineering Contradiction:

Improvecrank rotational angle detection accuracyVSAvoidsensor and control system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The tilt angle detector serves multiple functions: it detects mounting angle variations, provides data for calibration, and enables compensation for operational accuracy. This multi-functionality reduces the need for separate calibration devices, thereby limiting the increase in device complexity while achieving improved measurement precision

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Ease of manufacture

If calibration is performed manually by aligning marks, then manufacturing precision requirements are reduced, but operation time and user effort increase

Engineering Contradiction:

Improveassembly simplicityVSAvoidcalibration time

Core Design Contradiction:

Ease of manufactureVSLoss of time

Solution Approach 1:

The system performs automatic calibration by utilizing the tilt angle detector to self-determine the mounting angle and calculate the appropriate correction value. This self-calibration capability eliminates the need for manual mark alignment, thereby reducing both manufacturing precision requirements and calibration time

Inventive Principle:

Principle #25Self-service

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

Enables accurate power assist control by compensating for mounting angle variations, ensuring effective pedaling force estimation and preventing unnecessary power assist, even on inclined surfaces, while extending battery life by reducing rotational output during voltage drops.

Implementation Method 1

the tilt angle detector includes a gyro sensor (128)

Methodology Applied

Scientific EffectGyro sensor: Gyroscope

Implementation Method 2

a rotational angle sensor (124) provided in the housing and configured to detect a rotational angle of the electric motor or the rotating member

Methodology Applied

Scientific EffectRotational angle sensor detection:

Data Source

PatentUS12172731B2Electric power assist device for bicycles and bicycle

Publication Date: 2024.12.24 HONDA MOTOR CO LTD

AI summary

An electric power assist device includes a housing for attaching to a frame structure of a bicycle; an electric motor provided in the housing; a rotating member rotatably supported by the housing, rotationally driven by the electric motor, and connected to a crankshaft/crankarm of the bicycle in a torque transmitting relationship; a rotational angle sensor provided in the housing and configured to detect a rotational angle of the electric motor or the rotating member; and a control unit for controlling operation of the electric motor based on the rotational angle detected by the rotational angle sensor, wherein the electric power assist device has a tilt angle detector for detecting a tilt angle with respect to a direction of gravity, the control unit having a calibrator for determining an absolute angle of the rotational angle detected by the rotational angle sensor based on an output signal from the tilt angle detector.