Vehicle Control Unit Torque Distribution for Low Battery
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Solution Overview
Problem
Existing vehicle control systems struggle to maintain effective turn assist control when the state of charge of the high-voltage battery lowers, requiring drivers to perform complex steering operations at medium to high velocities, and fail to compensate for turning dynamics using driving force control.
Innovation Solution
A control unit that calculates a vehicle additional yaw moment based on yaw rate, adjusts assist torque and left-right wheel driving torque according to battery state of charge and slip angle change rate, and includes modules for steering torque instruction, slip angle calculation, and feedback yaw rate calculation to stabilize vehicle turning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If turning driving force control is performed using the difference between left and right driving forces, then turn assist control can be achieved, but when the state of charge of the high-voltage battery lowers, the turn assist control becomes impossible and the driver must perform complex steering operations
Solution Approach 1:
The control system dynamically switches between two control modes: driving force control (when battery SOC is sufficient) and steering torque control (when battery SOC is low). This dynamic adaptation ensures turn assist functionality is maintained across varying battery charge conditions, preventing the system from failing when battery charge decreases.
Solution Approach 2:
The system changes the control parameter from driving force differential (affecting vehicle dynamics) to steering torque (affecting steering assistance) based on battery state of charge. This parameter substitution allows the system to maintain turn assist capability while adapting to limited available energy from the battery.
2Reliability
If driving force control is used for turning, then turn assist can be provided, but when battery charge is low, the system cannot compensate for turn assist and requires driver intervention
Solution Approach 1:
The control system is designed to perform multiple functions: it can execute both driving force control (affecting vehicle motion) and steering torque control (affecting steering assistance) depending on battery conditions. This multi-functionality ensures reliable turn assist across varying battery charge states without requiring separate systems.
Solution Approach 2:
The system dynamically adapts its control strategy based on real-time battery state of charge monitoring. When SOC is sufficient, it uses driving force control; when SOC is low, it switches to steering torque control. This dynamic behavior maintains turn assist reliability while managing limited energy resources.
3Reliability
If the system switches to steering wheel control when battery charge is low, then turn assist control is maintained, but the driver is required to respond in shorter time and perform complicated steering operations
Solution Approach 1:
The steering torque control acts as an intermediary mechanism that provides assistive torque to the steering wheel, reducing the physical effort required by the driver. This intermediary support maintains ease of steering operation even when battery charge is low and driving force control cannot be used.
Data Source
AI summary
A control unit for a vehicle includes: a vehicle additional yaw moment calculator that calculates a vehicle additional yaw moment to be applied to a vehicle based on a yaw rate of the vehicle; a steering torque instructing module that instructs an assist torque of a steering operation of a steering system; a left-right driving force torque instructing module that instructs a left-right wheel driving torque which applies a moment to the vehicle independently of the steering system; a charging state acquisition module that acquires a state of charge of a battery which stores an electric power serving as a driving source for applying the vehicle additional yaw moment; and an adjuster that adjusts the assist torque and the left-right wheel driving torque based on the state of charge to apply the vehicle additional yaw moment.