Electric Assist Vehicle Speed Detection Using Sensor Fusion
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Solution Overview
Problem
Electric assist bicycles face challenges in continuously and stably detecting vehicle speed, particularly when starting or stopping, due to limitations in rotation and acceleration sensor data.
Innovation Solution
An electric assist system that combines a rotation sensor and an acceleration sensor to calculate speed, switching between sensors based on rotation data and adjusting coefficients to ensure accurate speed detection under various conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If only rotation sensor is used to detect speed, then measurement precision is improved during normal operation, but reliability deteriorates during starting and stopping phases
Solution Approach 1:
The patent combines rotation sensor and acceleration sensor to detect vehicle speed. The rotation sensor provides precise speed measurement during normal operation, while the acceleration sensor ensures continuous detection during starting and stopping phases. The controller integrates data from both sensors to calculate comprehensive speed information, resolving the contradiction between precision and reliability.
Solution Approach 2:
The acceleration sensor acts as an intermediary to bridge the detection gap during starting and stopping phases. When the rotation sensor cannot provide reliable data (at very low speeds or during transient phases), the acceleration sensor provides alternative speed information through integration of acceleration data, ensuring continuous and reliable speed detection.
2Reliability
If only acceleration sensor is used to detect speed, then reliability is improved during starting and stopping, but measurement precision deteriorates during normal operation
Solution Approach 1:
The system dynamically switches between using rotation sensor data and acceleration sensor data based on operating conditions. During normal operation, the rotation sensor is primarily used for precise speed measurement. During starting and stopping phases, the system transitions to using acceleration sensor data, creating a dynamic adaptation that optimizes both reliability and precision across different operational states.
3Reliability
If both rotation sensor and acceleration sensor are used together, then reliability is improved, but device complexity increases
Solution Approach 1:
The acceleration sensor serves multiple functions: it detects vehicle acceleration for speed calculation during starting and stopping phases, and also provides data for correcting rotation sensor measurements during normal operation. This multi-functionality justifies the added complexity by providing dual benefits of improved reliability and enhanced precision across all operating conditions.
Data Source
AI summary
An electric assist system usable for an electric assist bicycle includes an electric motor that generates assist power assisting human power of a rider of the electric assist bicycle, a rotation sensor that outputs a signal in accordance with a rotation of a rotatable component that rotates to operate the electric assist bicycle, an acceleration sensor that outputs a signal in accordance with an acceleration of the electric assist bicycle in a traveling direction thereof, and a controller that calculates a speed of the electric assist bicycle based on an output signal of the rotation sensor and an output signal of the acceleration sensor.