E-Bike Push Assist Control Using Shaft Angle Gear Estimation
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Solution Overview
Problem
Existing e-bike push assist systems inaccurately determine initial speed due to gear ratio uncertainties, leading to insufficient assistance or exceeding preset speeds.
Innovation Solution
A method for controlling push assist by presuming gears based on shaft angle measurements, adjusting drive speed and torque accordingly, and iteratively refining gear assumptions to provide optimal assistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the system assumes the highest gear to prevent exceeding preset speed, then speed control reliability is improved, but push assist effectiveness deteriorates
Solution Approach 1:
The system dynamically adjusts the presumed gear based on shaft angle measurements rather than statically assuming the highest gear. The control unit iteratively updates gear assumptions as the vehicle operates, transitioning from a conservative initial assumption to more accurate real-time gear identification, thereby optimizing push assist effectiveness while maintaining speed control reliability.
Solution Approach 2:
The system uses feedback from shaft angle measurements to continuously refine gear assumptions. By measuring the angle traveled by the drive shaft and comparing it against expected angles for different gears, the system identifies the actual gear and adjusts push assist parameters accordingly, resolving the contradiction between conservative speed control and optimal assistance.
2Measurement precision
If the system waits for definitive speed determination before activating push assist, then measurement accuracy is improved, but response time deteriorates
Solution Approach 1:
The system performs preliminary push assist activation based on initial gear assumptions before definitive speed measurement is available. Rather than waiting for complete wheel rotations and reed sensor signals, the system starts providing assistance immediately with conservative parameters, then refines them as measurements become available, eliminating activation delay while maintaining measurement integrity.
Solution Approach 2:
The system changes operational parameters dynamically by adjusting presumed gear values based on shaft angle measurements. As the vehicle operates and angle data accumulates, the system transitions from initial conservative parameter assumptions to refined parameters based on actual gear identification, achieving both timely response and measurement accuracy.
3Reliability
If the system uses reed sensor for speed measurement, then measurement reliability is improved, but initial speed detection capability deteriorates
Solution Approach 1:
The system introduces shaft angle measurement as an intermediary parameter to infer initial speed information. Rather than relying solely on reed sensor signals that require complete wheel rotations, the system measures shaft angle directly and uses this intermediate data to estimate initial speed and gear, enabling earlier detection while maintaining the reliability of reed sensor-based measurement for confirmation.
Data Source
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AI summary
The present invention relates to a method for controlling the push assist of a vehicle, in particular a single-track vehicle such as an e-bike, with a drive unit comprising a transmission with at least two gears and a speed measuring device comprising the steps of: - providing the push assist with a first drive speed and/or a first torque based on a first presumed gear, - determining an angle traveled by a shaft of the vehicle's drive unit since a last signal from the speed measuring device and/or since the start of the push assist, - presuming a second gear based on the angle traveled, and - providing the push assist with a second drive speed and/or a second torque based on the second presumed gear.