Dual-Drive Vehicle Torque Control Under Low-Friction Slip Limits
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Solution Overview
Problem
Existing motor vehicles with both an internal combustion engine and an electric machine face destabilization risks due to improper torque detection or implementation, particularly during low friction conditions, necessitating costly and weight-increasing redundancy measures to meet safety integrity levels like ASIL B to D, limiting load point increases to avoid destabilization.
Innovation Solution
Implementing a motor slip control with ASIL-B or ASIL-C integrity levels by choosing a first limit value for load point increase, allowing larger increases without destabilization, and activating a motor slip control only in low friction conditions, with a secondary limit value for fault scenarios to prevent destabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the load point of the first drive machine is increased by the electric machine operating as a generator, then the efficiency of the internal combustion engine is improved, but the risk of vehicle destabilization increases due to potential torque detection or implementation faults
Solution Approach 1:
The patent implements dynamic adjustment of the load point increase limit based on detected driving conditions. The control device adapts the maximum permissible negative torque of the electric machine according to the current operating state, including friction conditions detected by the motor slip control. This allows efficient operation under normal conditions while automatically reducing risk under low-friction or unstable conditions.
Solution Approach 2:
The patent employs feedback mechanisms through the motor slip control system that continuously monitors wheel slip conditions and provides information to the control device. This feedback loop enables the system to detect low-friction conditions and adjust the load point increase limit accordingly, creating a closed-loop control system that balances efficiency and stability.
2Reliability
If redundancy measures and sensors are added to meet ASIL B to D safety integrity levels, then the vehicle stability and safety are improved, but the vehicle weight, cost, and complexity increase considerably
Solution Approach 1:
The patent changes the operational parameters of the electric machine based on detected conditions rather than adding redundant hardware. By dynamically adjusting the load point increase limit as a control parameter, the system achieves adaptive safety without requiring additional sensors or redundant drive train components.
Solution Approach 2:
The control device uses information from existing sensors and the motor slip control system to automatically adjust operating parameters. The system serves its own safety function by utilizing already-present detection capabilities rather than requiring separate redundant safety systems.
3Reliability
If the load point increase is limited to low maximum negative torques, then the risk of vehicle destabilization is reduced, but the efficiency improvement of the internal combustion engine is restricted
Solution Approach 1:
The patent implements dynamic adjustment of the load point increase limit based on detected driving conditions. The control device adapts the maximum permissible negative torque of the electric machine according to the current operating state, including friction conditions detected by the motor slip control. This allows efficient operation under normal conditions while automatically reducing risk under low-friction or unstable conditions.
Solution Approach 2:
The patent changes the operational parameters of the electric machine based on detected conditions rather than adding redundant hardware. By dynamically adjusting the load point increase limit as a control parameter, the system achieves adaptive safety without requiring additional sensors or redundant drive train components.
Data Source
AI summary
A motor vehicle includes a control device that controls such that a first drive machine propels, while a second drive machine operates as a generator, and a load point of the first drive machine is increased by an amount that is bounded by a first limit value chosen such that, when a driving torque of the first drive machine is reduced to zero, while the amount is set at the first limit value and at a same time a motor slip control of the motor vehicle is not active, a destabilization of the motor vehicle occurs in a first test driving situation and no destabilization of the motor vehicle occurs in a second test driving situation, wherein a coefficient of friction of a static friction between tires of the motor vehicle and a roadway is between 0.4 and 0.9, or and the coefficient of friction is between 0.9 and 1.1.