Hybrid Vehicle Electric Machine Torque Control
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Solution Overview
Problem
Hybrid vehicles face increased accident risks due to unstable or stability-critical driving states caused by the electric machine's wheel drive torque, which existing safety measures may worsen upon shut-off, leading to uncontrolled loss of torque and potential instability.
Innovation Solution
The electric machine is operated in a total-wheel-drive-neutral mode by gradually reducing its active wheel drive torque to zero, ensuring it remains inactive during safety measures, preventing undesirable torque modifications and interference with the internal combustion engine's torque, thus stabilizing the vehicle dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric machine is shut off during unstable driving states to prevent worsening stability, then safety is improved, but sudden loss of wheel drive torque may cause even worse instability
Solution Approach 1:
The control device prepares the electric machine for shut-off by gradually reducing its wheel drive torque before complete discontinuation. This preliminary reduction of torque prevents sudden instability while maintaining safety, resolving the contradiction between preventing worsening stability and avoiding uncontrolled torque loss.
2Power
If the electric machine operates in generator mode to reduce total wheel drive torque during safety measures, then wheel drive torque control is improved, but vehicle stability may worsen in stability-critical states
Solution Approach 1:
The control device dynamically adjusts the electric machine's operating mode based on real-time stability assessment. When stability-critical states are detected, the control device transitions the electric machine from generator mode (which reduces torque) to motor mode or idle mode (which maintains or increases torque), thereby adapting the torque control to preserve vehicle stability while still enabling safety measures.
3Speed
If the electric machine operates in motor mode to increase total wheel drive torque during safety measures, then acceleration performance is improved, but vehicle stability may worsen in stability-critical states
Solution Approach 1:
The control device dynamically switches the electric machine's operating mode based on stability conditions. In stability-critical states, the control device prevents motor mode operation that would increase torque and worsen stability. Instead, it allows the electric machine to operate in generator mode or idle mode to maintain stability, while still enabling safety measures to function effectively.
4Stability of the object's composition
If safety measures intervene in vehicle dynamics to stabilize unstable states, then vehicle stability is improved, but the electric machine's wheel drive torque may counteract these stabilization efforts
Solution Approach 1:
The control device continuously monitors vehicle stability parameters and the electric machine's wheel drive torque contribution. When instability is detected and safety measures are activated, the control device provides feedback to adjust the electric machine's torque output, ensuring it does not counteract the stabilization efforts. This feedback loop coordinates the electric machine's operation with the safety measures, maintaining both stability and the effectiveness of safety interventions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach prevents worsening of unstable driving states, reduces accident risks, and ensures the safety of occupants and other road users by maintaining vehicle stability and adhering to safety standards like ISO 26262, while avoiding counteractive torque modifications.
Implementation Method 1
In a generator operating mode, the electric machine absorbs a drive torque and converts mechanical energy into electrical energy
Implementation Method 2
In a motor operating mode, the electric machine converts electrical energy back into mechanical energy and generates a drive torque
Data Source
AI summary
In a method for operating a hybrid vehicle, a total wheel drive torque is composed of a wheel drive torque of an internal combustion engine of the vehicle and a wheel drive torque of an electric machine of the vehicle, and the total wheel drive torque is selectively increased or decreased by the wheel drive torque of the electric machine in one of a motor mode or a generator mode of the electric machine. The electric machine is operated such that (i) the sum of the wheel drive torques of the electric machine and a wheel-drive-torque-reducing safety measure carried out remains constant in the generator mode, or (ii) the sum of the wheel drive torques of the electric machine and a wheel drive torque-increasing safety measure carried out remains constant in the motor mode.