Regenerative Brake Control for E-Mobility Using Dynamic Current
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Solution Overview
Problem
Existing regenerative brake systems for low-power electric mobility applications, such as e-scooters and e-bikes, face inefficiencies due to low power factor, high operating noise, and poor current regulation, particularly when using constant brake currents and duty cycles, which result in reduced battery life and uncomfortable riding experiences.
Innovation Solution
Implementing field-oriented control (FOC) for regenerative braking, which adjusts brake strength with motor and vehicle speed, uses sinusoidal phase currents to achieve unity power factor, reduces conduction losses, and minimizes noise, employing microcontrollers with interpolation tables to manage brake currents effectively, even with low-cost position encoders like Hall sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If constant brake currents and duty cycles are used, then the regenerative brake system is simple to implement, but the power factor is low and current regulation is poor
Solution Approach 1:
The patent implements dynamic current regulation by adjusting the brake current magnitude based on motor speed and ride demand, replacing fixed constant current control with a adaptive control strategy that optimizes performance across varying operating conditions
Solution Approach 2:
The patent changes the control parameters from constant duty cycle to variable duty cycle based on motor speed and desired deceleration, enabling optimal power factor and current regulation across the entire operating range by continuously adjusting control parameters
2Device complexity
If constant brake currents are used, then the control is simple, but operating noise is high
Solution Approach 1:
The patent dynamically adjusts brake current based on motor speed, reducing current at lower speeds where noise is more perceptible and optimizing current at higher speeds, thereby reducing operating noise while maintaining effective braking
Solution Approach 2:
The patent varies the brake current parameter as a function of motor speed, creating a speed-dependent control strategy that minimizes acoustic emissions across different operating conditions
3Device complexity
If constant brake currents are used, then the system is simple to control, but regeneration efficiency is poor
Solution Approach 1:
The patent implements feedback control by continuously monitoring motor speed and adjusting brake current accordingly, using speed feedback to optimize regenerative braking efficiency across varying ride conditions and speed ranges
Solution Approach 2:
The patent optimizes energy recovery by adjusting the brake current parameter based on motor speed and ride demand, maximizing regenerative braking efficiency at different operating points rather than using a fixed constant current
4Force
If high brake currents are used for strong braking, then braking performance is improved, but power factor decreases and noise increases
Solution Approach 1:
The patent implements speed-dependent current adjustment where high brake currents are applied only at higher speeds where they are needed for effective braking, while automatically reducing current at lower speeds where they would cause excessive noise and poor power factor
Solution Approach 2:
The patent changes the brake current parameter as a function of motor speed, creating an optimized current profile that delivers strong braking force when needed while minimizing harmful effects at different speed ranges
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
This approach enhances regeneration efficiency, extends battery life, reduces operating noise, and provides improved riding comfort by dynamically adjusting brake strength with speed, while maintaining performance across a wide speed range using cost-effective sensors.
Implementation Method 1
When the motor operates as a generator, a back-electromotive force (back-EMF) is generated that is proportional to a speed of the motor
Implementation Method 2
a controller to determine a braking current to be provided to the motor based on a relationship between the back-EMF, an armature resistance of the motor, and the speed of the motor
Data Source
AI summary
A controller for a motor system includes an input terminal to receive a signal indicating a speed of an electric motor and a regenerative brake current interpolator to indicate a brake current to be applied to the electric motor responsive to the speed of the electric motor. Values of the brake current vary with variation of the speed of the electric motor.