BEV Torque Split Control Under Axle Traction Limits
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Solution Overview
Problem
Existing battery electric vehicles (BEVs) face challenges in efficiently controlling torque distribution between propulsion units to ensure optimal performance, stability, and traction while avoiding wheel slip, which can lead to loss of control.
Innovation Solution
A controller that determines maximum and minimum torques for each axle based on vehicle operating conditions, ensuring torque distribution within safe limits to prevent wheel slip, and optimizes torque split for efficiency and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the hybrid vehicle uses both an internal combustion engine and an electric motor, then the vehicle can operate in multiple power modes (engine-only, motor-only, or combined), but the complexity of controlling power distribution and determining optimal operating modes increases
Solution Approach 1:
The system changes operational parameters by dynamically adjusting the split between engine and motor torque based on real-time vehicle conditions. The controller monitors speed, acceleration, battery state, and other parameters to determine optimal power distribution, transforming fixed power delivery into adaptive parameter-based control.
Solution Approach 2:
The control system implements feedback mechanisms by continuously monitoring vehicle operating conditions (speed, acceleration, battery charge state) and using this information to adjust power distribution in real-time. This closed-loop control enables the system to adapt to changing conditions while maintaining optimal performance.
2Loss of energy
If the vehicle operates in engine-only mode during low-speed conditions, then the electric motor can be used to charge the battery, but the engine operates in a less efficient operating range and overall system efficiency decreases
Solution Approach 1:
The system dynamically adjusts power distribution based on real-time conditions rather than operating in fixed modes. The controller continuously optimizes the balance between engine-generated power and motor-assisted power, allowing the engine to operate in more efficient ranges while still providing necessary vehicle propulsion and battery charging.
Solution Approach 2:
The control system changes operational parameters by adjusting torque split ratios and power distribution based on engine efficiency maps and battery charge state. This enables the engine to operate in optimal efficiency ranges while dynamically allocating excess power to charge the battery, rather than operating in suboptimal low-speed conditions.
3Loss of energy
If the vehicle operates in motor-only mode during high-power demands, then the engine can be used to charge the battery, but the motor operates in a less efficient operating range and overall system efficiency decreases
Solution Approach 1:
The system dynamically adjusts power distribution based on real-time conditions rather than operating in fixed modes. The controller continuously optimizes the balance between engine-generated power and motor-assisted power, allowing the motor to operate in more efficient ranges while still providing necessary high-power assistance and battery charging.
Solution Approach 2:
The control system changes operational parameters by adjusting torque split ratios and power distribution based on motor efficiency maps and battery charge state. This enables the motor to operate in optimal efficiency ranges while dynamically allocating excess power to charge the battery, rather than operating in suboptimal high-power conditions.
4Device complexity
If the vehicle uses a fixed power split between engine and motor, then the control system is simpler, but the vehicle cannot adapt to changing driving conditions and overall efficiency decreases
Solution Approach 1:
The system transitions from static fixed power split to dynamic adaptive power distribution. The controller continuously adjusts torque split ratios based on real-time vehicle conditions, enabling the powertrain to adapt to changing driving conditions while maintaining manageable control complexity through rule-based algorithms.
Data Source
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Figure 2A
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AI summary
A controller (2) for a vehicle (1) with a front and rear axle (3,4) each axle being provided with at least two wheels (W1-4) and at least first and second propulsion units (5,6), the controller for controlling the at least first and second propulsion units to generate a combined torque with reference to a total requested torque TQ, the controller comprising: means (21) to receive a torque request signal; means to receive one or more traction signals indicating available traction at least one wheel (TA1-4); means (51) to determine a traction torque range defined by a maximum and minimum torque for at least one of the at least first or second propulsion units in dependence on one or more of the traction signals; means (23) to determine a proposed distribution of torque between each of the at least first and second propulsion units with reference to the total requested torque; means (23) to determine a proposed torque to be generated by each of the at least first and second propulsion units in dependence on the proposed distribution of torque; means (24) to compare the traction torque range determined for each propulsion unit for which a traction torque range has been determined and the proposed torque for that propulsion unit; means to generate at least one torque control signal (DSF1, DSF2) for controlling at least one of the at least first and second propulsion units; wherein the torque control signal is a signal to the propulsion unit to generate the proposed torque for that propulsion unit if the proposed torque for that propulsion unit is within the traction torque range for that propulsion unit.