E-Bike Drive Torque Control for Front Wheel Lift-Off Prevention
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Solution Overview
Problem
Existing vehicle dynamics control systems for electrically propelled two-wheeled vehicles, such as pedelecs and electric bicycles, struggle to reliably prevent front wheel lift-off due to the limitations of wheel-speed sensor systems and methods for estimating vehicle angle, leading to potential safety hazards.
Innovation Solution
A sensor system comprising a rate-of-rotation sensor, acceleration sensor, and evaluation unit that compares pitch rate to a predefined threshold, adjusting drive torque using an amplification factor to prevent front wheel lift-off, enhanced by sensor fusion algorithms and predictive control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a wheel-speed sensor system is used to detect front wheel lift-off, then the system can provide basic speed information, but the measurement precision is insufficient to reliably distinguish actual lift-off from normal vibrations
Solution Approach 1:
The patent replaces mechanical wheel-speed sensor systems with an inertial sensor-based measurement system. The inertial sensor directly measures pitch rate (angular velocity around the longitudinal axis) without requiring wheel rotation detection, thereby achieving higher measurement precision for lift-off detection while reducing dependency on complex mechanical sensor arrangements.
Solution Approach 2:
The patent introduces an intermediary computational layer that processes inertial sensor data to derive pitch rate information. Instead of directly using wheel-speed sensor outputs, the system uses the inertial sensor as an intermediary measurement device that captures vehicle attitude dynamics more accurately, then processes this data through evaluation algorithms to detect lift-off conditions.
2Reliability
If the drive torque is reduced immediately when pitch rate exceeds threshold, then front wheel lift-off can be prevented, but erroneous torque adjustments occur due to small pitching movements from pedaling or ground excitation
Solution Approach 1:
The patent applies preliminary action by using predictive control algorithms that analyze trends in pitch rate data before actual lift-off occurs. The system evaluates whether the pitch rate exceedance is part of a continuing upward trend (indicating actual lift-off) versus a transient fluctuation (normal pedaling or ground excitation), and only reduces torque when predictive analysis confirms genuine lift-off risk.
Solution Approach 2:
The patent implements feedback control by continuously monitoring pitch rate and comparing it against threshold values with hysteresis logic. The system provides feedback to the torque control system only when pitch rate sustained exceedance confirms actual lift-off, rather than reacting to every transient fluctuation. This feedback mechanism filters out erroneous signals while maintaining reliable lift-off prevention.
3Measurement precision
If a high-resolution wheel-speed sensor system is used to improve pitch rate estimation, then measurement precision improves, but the device complexity and cost increase significantly
Solution Approach 1:
The patent replaces complex mechanical wheel-speed sensor systems with a simpler inertial sensor-based approach. Instead of using multiple high-resolution encoders on wheels to calculate pitch rate through complex differentiation and filtering, the system uses a single inertial sensor that directly measures pitch rate, achieving comparable or superior precision with reduced complexity.
Solution Approach 2:
The patent introduces the inertial sensor as an intermediary device that directly measures pitch rate without requiring complex processing of wheel-speed data. This intermediary measurement approach simplifies the overall sensor system architecture while providing the high-resolution pitch rate information needed for reliable lift-off detection.
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
The system effectively reduces the risk of front wheel lift-off with high reliability, improving safety and ride comfort by minimizing erroneous torque adjustments and anticipating potential lift-off situations.
Implementation Method 1
a sensor, on the basis of which a pitch rate of the electrically propelled two-wheeled vehicle is ascertained; the sensor taking the form, for example, of a rate-of-rotation sensor
Implementation Method 2
A position information item, which corresponds, for example, to the roll angle and/or the pitch angle of the two-wheeled vehicle, is derived from specific sensor variables
Data Source
AI summary
An electrically propelled two-wheeled vehicle and a method for adjusting a drive torque of an electrically propelled two-wheeled vehicle. The electrically propelled two-wheeled vehicle includes: a sensor, based on which a pitch rate of the electrically propelled two-wheeled vehicle is ascertainable; a device for influencing a drive torque of the electrically propelled two-wheeled vehicle; and an evaluation unit configured to compare a pitch rate, which is ascertained on the basis of the sensor and represents a pitch rate of the electrically propelled two-wheeled vehicle relative to the surroundings of the two-wheeled vehicle, to a predefined, static pitch rate threshold value, and configured to reduce a drive torque acting upon a drive train of the electrically propelled two-wheeled vehicle using a predefined amplification factor, if a pitch rate generated by an upward movement of a front wheel of the electrically propelled two-wheeled vehicle exceeds the static pitch rate threshold value.