Pedelec Torque Control for Smooth Startup Transition
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Solution Overview
Problem
Existing electric bicycles lack a smooth and comfortable transition from a state without support to a state with support during startup, leading to potential accidents and reduced riding comfort due to abrupt torque changes.
Innovation Solution
A control device that adjusts the supporting torque based on the rider's input torque using different rules in distinct value ranges, including a first rule assigning zero output torque during startup, a second rule as a third-degree polynomial function for smooth transition, and a third rule as a linear function for regular support, ensuring seamless transitions and predictable control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If supporting torque is switched on immediately when a threshold value of rider's torque is reached, then the supporting torque is provided without delay, but abrupt torque changes occur causing reduced controllability and increased accident risk
Solution Approach 1:
The patent applies dynamics by making the supporting torque adjustable and time-dependent rather than fixed and instantaneous. The control device dynamically adapts the supporting torque based on the rider's input torque and time since startup, creating a smooth transition from zero to full supporting torque. This resolves the contradiction by allowing the system to respond quickly when needed while maintaining controllability through gradual adjustment.
Solution Approach 2:
The patent changes the parameter of supporting torque from a binary on/off state to a continuously variable parameter. By introducing a transition period where the supporting torque increases gradually from zero to the calculated value, the system achieves both quick response (when the threshold is reached) and smooth controllability (during the transition). This parameter change resolves the contradiction between immediate support and abrupt changes.
2Power
If supporting torque is provided immediately at startup, then the rider receives full support, but the transition from un supported to supported state is abrupt reducing riding comfort
Solution Approach 1:
The patent applies beforehand cushioning by introducing a transition period before full supporting torque is applied. During this transition period (e.g., first 2 seconds after startup), the supporting torque increases gradually from zero to the full calculated value. This cushions the transition and prevents abrupt changes, thereby maintaining riding comfort while still providing the necessary supporting torque.
Solution Approach 2:
The patent makes the supporting torque dynamic and time-dependent rather than static and immediate. The control device adjusts the supporting torque based on the elapsed time since startup and the rider's input torque, creating a smooth, progressive transition. This dynamic approach resolves the contradiction between providing full power support and maintaining comfort during the transition.
3Ease of operation
If multiple rules are used for different torque value ranges, then seamless transition between support states is achieved, but the control logic becomes more complex
Solution Approach 1:
The patent applies segmentation by dividing the rider's input torque into different value ranges, each with its own rule for determining supporting torque. This segmentation allows the system to apply different control strategies for different operating conditions (e.g., startup vs. normal operation), achieving smooth transitions while keeping each individual rule relatively simple. The segmentation resolves the contradiction by organizing complexity into manageable segments.
Solution Approach 2:
The patent applies local quality by assigning different control rules to different torque value ranges. Each range has optimized characteristics suitable for its specific operating condition (e.g., gradual transition at low torque, linear relationship at high torque). This local optimization achieves smooth overall transitions while keeping each local rule simple and targeted, resolving the contradiction between smoothness and complexity.
Data Source
AI summary
A control device of a drive of an electric bicycle is disclosed. The control device is designed to (i) receive and/or retrieve a rider's input torque applied by a rider of the electric bicycle, (ii) determine an output torque based on the rider's input torque in a first value range of the rider's input torque according to a first rule, in a second value range of the rider's input torque according to a second rule and in a third value range of the rider's input torque according to a third rule, (iii) determine a supporting torque based on the output torque, and (iv) control the drive in accordance with the supporting torque. The second value range directly adjoins the first value range and the third value range. The first rule and the second rule and the third rule are different from one another. And the second rule is a continuous function with the rider's input torque as input parameter.