Electric AWD Axle Control for Drag Loss and Connection Time
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Solution Overview
Problem
Hybrid drive systems face a conflict between minimizing drag losses and ensuring rapid connection times of the electric machine, particularly at high speeds, which affects the efficiency and driving experience.
Innovation Solution
A method and controller that divide the vehicle speed range into three segments, actuating the electric machine and switchable elements to minimize drag losses and ensure defined connection times, using a clutch or multiplate clutch to optimize the electric all-wheel drive system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the electric machine is continuously connected to the vehicle axle, then rapid connection time is achieved, but drag losses increase significantly
Solution Approach 1:
The patent applies dynamics by making the connection state of the electric machine variable rather than fixed. The controller dynamically switches between connected and disconnected states based on real-time operating conditions (speed range, torque requirements, driving mode), allowing the system to adapt optimally between minimizing drag losses and ensuring rapid connection capability
Solution Approach 2:
The patent implements preliminary action by pre-defining multiple speed ranges and associated control strategies. The controller is programmed with predetermined connection/disconnection thresholds and operating modes, enabling the electric machine to be in the optimal state (connected or disconnected) before specific operating conditions are encountered, thus minimizing drag losses while ensuring rapid response when needed
2Loss of energy
If the electric machine is disconnected to minimize drag losses, then energy efficiency improves, but connection response time deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the vehicle speed range into multiple distinct segments (first speed range, second speed range, third speed range). Each segment has specific connection/disconnection control strategies, allowing the system to optimize for drag loss reduction in certain segments while ensuring rapid connection capability in others where performance is prioritized
3Loss of time
If the electric machine rotates at preset speed while disconnected, then connection time is reduced, but drag losses increase
Solution Approach 1:
The patent applies partial action by implementing an intermediate operating mode where the electric machine rotates at a preset speed while disconnected from the vehicle axle. This partial engagement allows the machine to maintain readiness for rapid connection without the full drag losses of continuous connection, representing a compromise between the two extreme states
Data Source
AI summary
A method is provided for operating a drive train comprising an internal combustion engine or an electric machine as a primary drive and an electric machine as a secondary drive, wherein the electric machine is detachably coupled, together with an inverter and controller, on one of the vehicle axles. The electric machine and at least one switchable element is actuated in order to minimize drag losses of the electric machine and to provide a defined connection time for the electric machine. The electric machine is stationary and decoupled during a first speed range. The electric machine is actuated at a preset speed during a second speed range, where a defined connection time is not possible if the electric machine were stationary. The electric machine is coupled to the axle and rotates at the vehicle speed in the third range, when losses while coupled are lower than if uncoupled.