Electronic Differential for Wheel Hub Motor Synchronization
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Solution Overview
Problem
Electric vehicles with multiple wheel hub motors face synchronization challenges and safety issues due to mechanical power losses and the need for separate controllers, leading to potential swerving and unsafe driving conditions.
Innovation Solution
A method involving a central interface module that determines correction factors from sensor signals to control BLDC motors, forming an electronic differential and ensuring safe operation by synchronizing power and speed adjustments across wheels, with the ability to switch to emergency operation in case of defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If separate control units are used for each wheel hub motor, then each motor can be controlled independently, but synchronization problems occur leading to unstable handling and safety issues
Solution Approach 1:
The patent merges multiple separate control units into a single centralized control unit that manages all wheel hub motors. This control unit includes a differential model that calculates target rotation speeds for each wheel based on vehicle dynamics, ensuring synchronized operation while maintaining independent control capability for each motor. The merging approach eliminates synchronization problems between separate controllers while preserving the ability to independently adjust each wheel's power output.
2Device complexity
If mechanical differential and rear axle are used to drive rear wheels, then power transmission is simplified, but mechanical power losses increase reducing overall efficiency
Solution Approach 1:
The patent replaces the mechanical differential and rear axle system with an electronic differential implemented in a centralized control unit. Instead of mechanically transmitting power through a differential gear system, the electronic differential calculates target rotation speeds for each wheel and communicates these targets to individual motor controllers. This substitution eliminates mechanical power losses in the differential and axle while maintaining the ability to distribute power differentially between wheels.
3Loss of energy
If wheel hub motors are integrated into drive wheels, then mechanical power losses are reduced, but synchronization and control complexity increase
Solution Approach 1:
The patent combines multiple control functions into a single centralized control unit, merging the differential control, motor management, and synchronization functions. This unified approach reduces control complexity compared to having separate control units for each motor, as the centralized unit handles all synchronization and coordination tasks through its differential model, eliminating the need for complex inter-controller communication protocols.
4Device complexity
If block control with abrupt switching is used for BLDC motors, then control simplicity is maintained, but noise levels increase and energy losses occur
Solution Approach 1:
The patent implements sinusoidal PWM control for the BLDC motors, replacing abrupt block control with periodic sinusoidal switching patterns. The control unit generates sinusoidal reference signals for each motor phase and uses PWM to modulate the actual switching, creating smooth periodic action that eliminates abrupt transitions. This approach significantly reduces electromagnetic noise and motor vibrations while maintaining precise control capability, and the periodic nature of the sinusoidal control optimizes commutation timing.
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 solution enables safe and efficient operation of electric vehicles with multiple wheel hub motors by reducing mechanical losses, improving traction, and ensuring directional stability, even on slippery surfaces, while allowing regenerative braking and fault tolerance.
Implementation Method 1
The motor can be set in motion by applying voltage to suitable coils, and the resulting magnetic field pulls the rotor a short distance
Implementation Method 2
a stationary, ring-shaped arrangement of coils (the stator), and a similarly ring-shaped arrangement of permanent magnets (the rotor)
Implementation Method 3
This is usually provided by three Hall effect sensors. Their signals are evaluated by the controller and used to determine the switching points of the motor terminals
Implementation Method 4
The voltage is pulsed, meaning it is switched on and off in very rapid succession. This minimizes power loss in the semiconductors, as they are either completely off or completely on. This pulse-width modulation (PWM) allows for precise control of the motor power
Data Source
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AI summary
A method for operating a vehicle which has at least one steered axle and at least one driven axle, wherein at least the driven axle has at least two wheel-hub electric motors that are integrated in the respective drive wheel. In addition, an electronic control unit (BLDC controller module 1, BLDC controller module 2) is provided for the wheel-hub motors (wheel-hub motor 1, wheel hub motor 2) forming an electronic differential. Sensors detect signals (Hall signals) that correspond to the driving defaults. Correction factors for default values for controlling the wheel-hub motors are determined from the sensor signals (speed), the position of the accelerator pedal (gas pedal) or accelerator throttle and the steering angle (steering angle generator) by an interface module and the factors are forwarded to the relevant motor control units (BLDC controller module 1, BLDC controller module 2).