Hybrid Vehicle Control Method for Pseudo Multistage Shifting
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Solution Overview
Problem
Hybrid vehicles with continuously changing shift ratios, like those using a power-split-parallel system, often fail to provide driving comfort for users unfamiliar with Continuously Variable Transmission (CVT) characteristics, leading to a deteriorated perceived quality.
Innovation Solution
A control method that adjusts torque from first and second motor generators and engine speed based on driving situations to create pseudo gear ratios, allowing for multistage shifting and improved comfort by determining target engine speeds and torques through a shifting request check, engine speed control, and torque distribution across motor generators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If continuously changing shift ratios are used in a power-split system, then fuel efficiency and adaptability are improved, but driving comfort deteriorates for users unfamiliar with CVT characteristics
Solution Approach 1:
The continuously changing shift ratios are segmented into multiple pseudo gear stages (first through sixth gear stages) with specific ratio ranges. This segmentation creates distinct shifting sensations that improve driving comfort while maintaining the continuous variability benefits.
Solution Approach 2:
The control device acts as an intermediary that manages the transition between pseudo gear stages by controlling motor generator torques. It determines target engine speeds and control torques to facilitate smooth transitions that mimic traditional multistage transmission behavior.
2Ease of operation
If pseudo gear stages are implemented through control methods, then driving comfort is improved, but system complexity increases
Solution Approach 1:
The control device performs multiple functions including determining shifting requests, determining target engine speeds, determining control torques, and controlling motor generators. This multi-functionality manages complexity by consolidating control logic in a single device rather than requiring separate systems for each function.
Solution Approach 2:
The system changes operational parameters (engine speed, motor generator torques) to achieve pseudo gear stage transitions. By controlling these parameters dynamically, the system creates multistage shifting effects without requiring additional mechanical components.
3Speed
If target engine speed and torque are dynamically determined, then responsiveness to driving situations is improved, but energy management complexity increases
Solution Approach 1:
The control device continuously monitors driving situations and adjusts target engine speeds and control torques based on feedback from the vehicle's operational state. This feedback mechanism ensures responsive control while optimizing energy management through dynamic adjustment rather than fixed schedules.
Solution Approach 2:
The control device determines target engine speeds and control torques in advance of actual gear stage transitions. This preliminary determination allows the system to prepare for upcoming shifts, improving responsiveness while managing energy efficiently by pre-positioning the engine and motor generators in optimal states.
Data Source
AI summary
A control method for a vehicle may include shifting request check step of checking whether there is request for shifting in vehicle on the basis of acceleration pedal depression extent and vehicle speed by shifting control device; target engine speed determination step of determining engine target speed on basis of the vehicle speed and gear ratio of pseudo target gear stage by target engine speed determiner when request for shifting is found to have been received as the result of the shifting request check step; and engine speed control step of controlling the engine speed to follow the target engine speed by determining the engine speed control torque on the basis of the difference between the target engine speed and the current engine speed and by applying the determined engine speed control torque to the first motor generator, after the engine target speed determination step.