Hybrid Powertrain Speed Control for Smooth Gear Shifts
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing powertrain systems for hybrid electric vehicles face challenges in smooth closed-pedal gear shifting due to reliance on conventional engine speed control, which can result in noticeable driveline disturbances and require complex calibration of pressure and clutch coordination.
Innovation Solution
A control strategy that uses a high voltage electric motor to match transmission input speed with synchronous speed during gear shifts, determining initial and current target speeds to minimize acceleration and deceleration discontinuities, allowing independent operation from shift pressure control and reducing torque disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional engine speed control is used during gear shifts, then the control system is simpler to implement, but driveline disturbances become noticeable and shift smoothness deteriorates
Solution Approach 1:
The electric motor serves as an intermediary device between the engine and transmission, actively controlling transmission input speed during gear shifts. This mediator compensates for speed mismatches and minimizes driveline disturbances, achieving smooth shifts without requiring complex coordination of pressure and clutch systems.
Solution Approach 2:
The patent replaces conventional mechanical engine speed control with electric motor control. The electric motor provides precise speed regulation through electrical control, substituting the mechanical feedback and adjustment mechanisms of traditional engine speed control, thereby reducing driveline disturbances during shifts.
2Device complexity
If conventional engine speed control is used during gear shifts, then the control strategy is simpler, but calibration effort for pressure and clutch coordination increases
Solution Approach 1:
The patent extracts the speed control function from the engine and assigns it to the electric motor. This separation allows the control strategy to focus solely on motor speed regulation, eliminating the need for complex calibration of pressure and clutch coordination that would otherwise be required when using engine speed control.
3Object-affected harmful factors
If electric motor is used for transmission input speed control during gear shifts, then shift smoothness is improved, but the control system becomes more complex
Solution Approach 1:
The control system continuously monitors transmission input speed and compares it with the target synchronous speed for the upcoming gear. The electric motor control adjusts based on this feedback to minimize speed deviation, ensuring smooth shifts. This feedback mechanism is simpler than coordinating multiple mechanical systems.
4Loss of time
If faster gear shifts are achieved through engine speed control, then shift time is reduced, but driveline disturbance increases
Solution Approach 1:
The electric motor dynamically adjusts transmission input speed during the gear shift process, continuously adapting to match the synchronous speed profile. This dynamic control allows for faster shifts while maintaining smooth operation, as the motor can rapidly respond to speed changes without causing mechanical disturbances.
Data Source
AI summary
A method for controlling a power-off shift from a current gear to a target gear in a hybrid electric powertrain including an engine, electric motor and automatic transmission includes the steps of determining an initial target speed for the current gear, operating the motor at the initial target speed, repetitively determining a current gear ratio, a output shaft speed during the gear ratio change, a time rate of change of output shaft speed, using the current gear ratio, the current speed of the output shaft and the time rate of change of output shaft speed repetitively to determine a current target speed, and operating the motor at the current target speed until a gear change to the next gear is completed.