Drive Axle Predictive Speed Synchronization for Fast Recoupling
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Solution Overview
Problem
Conventional decoupling units in electrically driveable motor vehicles recouple electric machines into the drivetrain slowly, leading to delays in power delivery and potentially unsettling drivers, as they require time for speed synchronization and torque matching, which increases wear and frictional losses.
Innovation Solution
A method that predictsively aligns the speed of the gear output element and wheel drive shaft based on driving conditions to quickly and efficiently couple the electric traction machine into the drivetrain, using a coupling probability value and variance analysis to determine the need for coupling, thereby reducing the overall time requirement for recoupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If speed synchronization is performed before coupling to ensure proper engagement and reduce wear, then coupling reliability is improved, but coupling time increases significantly
Solution Approach 1:
The control unit predicts the need for coupling in advance and initiates speed synchronization before the actual coupling event is required. By performing the speed matching operation preliminarily based on predicted driving conditions, the system ensures that when coupling becomes necessary, the speed synchronization is already complete or nearly complete, thereby reducing the actual coupling time while maintaining reliability
Solution Approach 2:
The system dynamically adjusts the speed synchronization process based on real-time driving conditions and predicted coupling probability. The control unit continuously monitors driving parameters and adapts the synchronization timing and rate, allowing the system to optimize the balance between coupling reliability and coupling time according to the specific operational context
2Loss of energy
If the electric machine is decoupled to minimize frictional losses during low-power operation, then energy efficiency is improved, but power delivery response time deteriorates
Solution Approach 1:
The control unit predicts upcoming high-power demand based on driving conditions and initiates speed synchronization and coupling preparation in advance. This preliminary action ensures that when power delivery is required, the electric machine is already positioned and synchronized for immediate engagement, eliminating the delay between power demand and actual power delivery while maintaining energy efficiency during low-demand periods
Solution Approach 2:
The system uses feedback from driving condition sensors and power demand signals to continuously adjust the coupling state. The control unit monitors various parameters including vehicle speed, acceleration demand, and battery state, and uses this feedback to determine the optimal coupling probability and timing, thereby balancing energy efficiency during coasting with rapid response capability when power is needed
Data Source
AI summary
A method for operating a drive axle, a control unit for carrying out the method, a drive axle, and a motor vehicle. In the method, a driving state variable is detected which characterizes the current driving situation. A coupling probability value K is ascertained on the basis of the driving state variable, and if the coupling probability value K is greater than a threshold G, the rotational speed of the transmission output element is adapted to a wheel driveshaft rotational speed via an electric traction machine. The process of adapting the rotational speed is carried out in a predictive manner, i.e. regardless of whether a coupling process is subsequently initiated in which the transmission output element and the wheel driveshaft are rotationally fixed to each other.