Hybrid Vehicle Travel Control for Engine Delay and Regenerative Recovery
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Solution Overview
Problem
Existing travel control apparatuses for hybrid vehicles face challenges in efficiently accelerating to specified speeds without fuel consumption and optimizing regenerative energy recovery, with issues related to engine starting, torque management, and deceleration timing, which affect fuel efficiency and brake actuator durability.
Innovation Solution
A vehicle travel control apparatus that includes a target vehicle speed computing unit, acceleration command value calculation unit, acceleration limit processing unit, torque command value computing unit, and speed-change command value computing unit to manage acceleration and deceleration, allowing for engine delay during acceleration and increased regenerative energy recovery during deceleration, while optimizing torque usage and down-shifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the engine is started to increase torque during acceleration, then the acceleration performance is improved, but fuel consumption increases
Solution Approach 1:
The system performs preliminary assessment of acceleration requirements by comparing commanded acceleration with motor-capable acceleration. When the motor alone can satisfy the acceleration demand, the engine remains off, avoiding unnecessary fuel consumption. This preliminary check prevents premature engine startup while ensuring acceleration performance requirements are met.
Solution Approach 2:
The system dynamically adjusts the acceleration command value based on motor torque capabilities and vehicle state. By modifying the acceleration parameter to match what the motor can deliver, the system achieves acceptable acceleration performance without requiring engine intervention, thus reducing fuel consumption.
2Ease of operation
If regenerative coordinated braking is performed to adjust deceleration, then the driver comfort is improved, but the regenerative energy recovery amount is reduced
Solution Approach 1:
The system extracts regenerative coordinated braking from the overall braking control when travel control is active. By removing this comfort-oriented but energy-wasting control mode during travel control, the system maximizes regenerative energy recovery while maintaining adequate deceleration performance through motor torque control alone.
Solution Approach 2:
The travel control system independently manages deceleration using motor torque control without relying on regenerative coordinated braking. This self-sufficient approach allows the system to recover maximum regenerative energy while still achieving the required deceleration, making the system self-reliant rather than depending on additional braking coordination.
3Loss of energy
If the minimum motor torque is used for deceleration, then the regenerative energy recovery is maximized, but the deceleration timing is delayed
Solution Approach 1:
The system dynamically adjusts motor torque during deceleration based on real-time requirements. Rather than fixed minimum torque, the torque is continuously optimized to achieve both timely deceleration and maximum regenerative energy recovery, adapting to changing vehicle conditions and deceleration demands.
Solution Approach 2:
The system performs preliminary calculation of required deceleration torque and compares it with motor capabilities before executing deceleration. This advance planning ensures that the motor can deliver sufficient torque for timely deceleration while operating in the optimal range for regenerative energy recovery.
4Speed
If the brake actuator is used for deceleration during travel control, then the deceleration performance is improved, but the brake actuator durability and cost are negatively affected
Solution Approach 1:
The system replaces mechanical friction braking with electric motor torque control for deceleration during travel control. By substituting the mechanical brake actuator with the electric motor, the system achieves equivalent or superior deceleration performance while eliminating wear and durability concerns associated with friction brakes, and reducing overall system cost.
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
The solution reduces fuel consumption by delaying engine start during acceleration and enhances regenerative energy recovery during deceleration, improving fuel efficiency and reducing the need for brake actuator durability and cost.
Implementation Method 1
a hybrid vehicle utilizing both an engine and an electric motor as a power source, generate a braking force by operating an electric motor from the motive force of the drive wheel during vehicle e deceleration, and on the other hand perform regenerative braking utilizing the power generated by the electric motor
Data Source
AI summary
A vehicle travel control apparatus is provided that is capable of improving fuel economy by exerting control so as to attain a specified speed without starting the engine during acceleration, and by increasing the regenerative energy recovery amount during deceleration, during the travel control. A vehicle travel control apparatus (100) to control the vehicle speed is mounted in a hybrid vehicle containing an engine (107) and a motor (112) as power sources, and includes: a target vehicle computing unit (200) that calculates a target vehicle speed; an acceleration command value calculation unit (201) that calculates an acceleration command value (211) based on a target vehicle speed; an acceleration limit processing unit (203) that calculates a post-limit acceleration command value (214) that limits the acceleration command value (211) by utilizing a specified upper-limit value and a specified lower-limit value; a torque command value computing unit (205) that calculates a torque command value from the post-limit acceleration command value (214); and a speed-change command value computing unit (206) that determines whether a down-shift is required or not based on the acceleration command value (211) and an upper-limit torque or a lower-limit torque of the motor, and calculates a speed-change command value (215).