Hybrid Control Torque Blending for Electrically Continuous Variable Transmissions
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Solution Overview
Problem
Hybrid electric vehicles experience significant vehicle jerks when switching from electric vehicle mode to hybrid mode due to engine start oscillations, which negatively affect fuel economy and ride comfort.
Innovation Solution
A hybrid control system that includes a torque control module to adjust the output torque of electric motor generators based on a torque override request signal during engine startup, allowing the system to manage engine cranking and reduce jerks by modifying the transmission output torque request signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the engine is started during mode transition from EV mode to hybrid mode, then the vehicle can provide propulsion torque through engine-MGU combination, but large vehicle jerks occur due to engine start oscillations
Solution Approach 1:
The control system applies preliminary anti-action by detecting engine start oscillations and generating a counteracting torque command from the second MGU before the oscillations fully develop. The system predicts the oscillatory torque pattern based on engine speed and rotational direction, then applies an opposing torque to cancel out the harmful vibrations, thereby preventing vehicle jerks while maintaining propulsion capability.
Solution Approach 2:
The second MGU acts as an intermediary element between the engine and the drivetrain during mode transition. Instead of allowing engine oscillations to directly transmit to the wheels, the second MGU absorbs and smooths these oscillations by providing compensating torque, thus mediating the interaction between the engine's irregular torque output and the vehicle's motion requirements.
2Reliability
If the control system switches from EV mode to hybrid mode, then the battery SOC is maintained above threshold, but fuel economy deteriorates due to increased vehicle jerks and inefficient engine operation
Solution Approach 1:
The control system dynamically adjusts the torque distribution between the engine and MGUs based on real-time operating conditions. During mode transition, the system continuously modifies the torque commands to the first and second MGUs according to engine speed, acceleration requests, and detected oscillations, enabling adaptive optimization of fuel economy while maintaining battery SOC reliability.
Solution Approach 2:
The system changes operational parameters by adjusting the torque output levels of the MGUs and the engine speed during mode transition. By modifying these parameters dynamically - particularly by using the second MGU to counteract oscillations and by optimizing the engine's operating point - the system achieves smoother operation that improves fuel economy while maintaining the necessary battery charge level.
Data Source
AI summary
A hybrid control system for a hybrid electric vehicle (HEV) includes a hybrid control module. The hybrid control module includes a first motor control module that controls output torque of a first motor. A second motor control module controls output torque of a second motor based on a second motor torque request signal. The second motor torque request signal is generated based on a transmission output torque request signal prior to startup of an engine of the HEV. An override module generates a torque override request signal during the startup. The first motor control module controls output torque of the first motor to crank the engine during the startup. The second motor control module adjusts output torque of the second motor based on the torque override request signal and not the transmission output torque request signal during the startup to minimize vehicle jerk during the engine start.