Hybrid Vehicle Cruise Control Engine Speed Management
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Solution Overview
Problem
Hybrid vehicles face challenges in maintaining constant speed during downhill travel due to limited chargeable electric power, leading to rapid engine speed increases and discomfort for users, as regenerative torque charging limits battery capacity and necessitates engine motoring to generate braking torque.
Innovation Solution
Implementing an electronic control unit that executes simulated stepped gear shift control before motoring control to increase engine rotation speed gradually, adjusting the output of the first rotating electric machine to minimize regenerative electric power and ensure sufficient braking torque, while compensating for engine brake torque deficiencies with regenerative torque from the second rotating electric machine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If regenerative torque is continuously generated by the second rotating electric machine to maintain constant vehicle speed during downhill travel, then braking torque is secured, but the battery SOC approaches full charge state and chargeable electric power is limited
Solution Approach 1:
The electronic control unit performs simulated stepped gear shift control before motoring control is needed. By preliminarily increasing the engine rotation speed through gear ratio adjustment, the system prepares the engine to provide brake torque when the battery approaches full charge, preventing the need for rapid engine speed increases later
Solution Approach 2:
The first rotating electric machine acts as an intermediary to transfer mechanical energy from the engine to the drive wheels. By controlling the first rotating electric machine to operate as a motor generator, the system can apply engine brake torque to the drive wheels without directly charging the battery, thus resolving the conflict between needing braking torque and maintaining battery chargeability
2Quantity of substance
If motoring control is executed to quickly decrease chargeable electric power by increasing engine rotation speed, then engine brake torque is applied to reduce regenerative torque, but the engine rotation speed increases rapidly causing user discomfort
Solution Approach 1:
The system executes simulated stepped gear shift control before motoring control is required. This preliminary action gradually increases engine rotation speed by adjusting gear ratios, so when motoring control eventually occurs, the engine speed increase is less abrupt and does not cause user discomfort
Solution Approach 2:
The system dynamically adjusts the gear ratio of the planetary gear mechanism to control engine rotation speed. By simulating stepped gear shifts, the system creates a dynamic transmission ratio change that allows controlled, gradual engine speed increases rather than sudden jumps, maintaining user comfort while managing battery chargeable power
3Speed
If the gear ratio is adjusted to increase engine rotation speed before motoring control, then rapid engine speed increase is suppressed, but the control system complexity increases
Solution Approach 1:
The electronic control unit integrates multiple functions into a single control system. It simultaneously manages cruise control, monitors battery SOC, determines chargeable electric power limits, executes simulated stepped gear shift control, and controls motoring control. This multi-functionality reduces the need for separate dedicated control systems for each function
Solution Approach 2:
The system changes the gear ratio parameter of the planetary gear mechanism to control engine rotation speed. By adjusting this single parameter through simulated stepped gear shifts, the system achieves smooth engine speed transitions without requiring complex mechanical modifications or additional control components
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 effectively suppresses rapid engine speed increases, maintains energy efficiency, and reduces vibrations and noise, ensuring comfortable cruise travel by managing chargeable electric power and torque distribution.
Implementation Method 1
The planetary gear mechanism is configured to mechanically couple the engine, the first rotating electric machine, and the second rotating electric machine
Implementation Method 2
increase a rotation speed of the engine with the first rotating electric machine such that engine brake torque is applied to the drive wheels
Implementation Method 3
regeneration control by the second rotating electric machine is executed, and regenerative electric power is charged in the battery
Implementation Method 4
The battery performs charging and discharging with the first rotating electric machine and second rotating electric machine
Data Source
AI summary
A hybrid vehicle includes an engine, a first rotating electric machine, a second rotating electric machine coupled to drive wheels of the hybrid vehicle, a planetary gear mechanism configured to mechanically couple the engine, the first rotating electric machine, and the second rotating electric machine, an electric power storage device configured to perform charging and discharging with the first rotating electric machine and second rotating electric machine, and an electronic control unit configured to, in a case where cruise control is requested or in a case where deceleration torque is requested by the cruise control, execute motoring control and simulated stepped gear shift control.