Regenerative Speed Control for Hybrid CVT
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Solution Overview
Problem
Conventional vehicle regenerative speed control devices cause discomfort to drivers due to inertia shock and overshooting during regenerative braking transitions, especially when switching from regenerative to mechanical braking, due to rapid changes in transmission input rotational speed.
Innovation Solution
A controller is implemented to limit the rotational speed change rate of the transmission input shaft in a vehicle with a continuously variable transmission and electric motor, performing downshifting to increase rotational speed and gradually lowering it to prevent overshooting and inertia shock during regenerative braking transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If downshifting is carried out to rapidly increase the transmission input rotational speed toward the target rotational speed of regenerative braking, then the regenerative efficiency is improved, but the actual transmission input rotational speed rapidly increases and then turns back and rapidly decreases, causing overshooting and inertia shock that imparts discomfort to the driver
Solution Approach 1:
The patent applies dynamics by making the transmission input rotational speed command value changeable over time. Specifically, the system dynamically adjusts the command value based on the operational region: in the brake switching region, the command value increases at a limited rate to prevent overshooting, while in the regenerative braking region, it can be rapidly adjusted. This dynamic adaptation resolves the contradiction between achieving high regenerative efficiency and preventing inertia shock.
Solution Approach 2:
The patent changes the parameter of transmission input rotational speed command value based on the operational region. By detecting whether the vehicle is in the brake switching region or regenerative braking region, the system applies different command value strategies: limiting the increase rate in the brake switching region to prevent discomfort, and allowing rapid adjustment in the regenerative braking region to maximize efficiency. This parameter change approach resolves the technical contradiction.
2Measurement precision
If the regenerative speed control is set to a feedback transmission control, then the control precision is improved, but the follow-up response of the actual transmission input rotational speed with respect to the command value is delayed, causing the actual speed to exceed the target speed
Solution Approach 1:
The patent applies preliminary action by pre-limiting the transmission input rotational speed command value increase rate before the feedback control loop can respond. In the brake switching region, the system proactively restricts how fast the command value can increase, which prevents the delayed feedback response from causing overshooting. This preliminary constraint resolves the contradiction between control precision and response speed.
3Productivity
If downshifting is carried out to increase the transmission input rotational speed, then the regenerative braking efficiency is improved, but the transmission input rotational speed must be rapidly lowered after reaching the target, causing additional inertia shock
Solution Approach 1:
The patent applies dynamics by making the transmission input rotational speed command value changeable over time. Specifically, the system dynamically adjusts the command value based on the operational region: in the brake switching region, the command value increases at a limited rate to prevent overshooting, while in the regenerative braking region, it can be rapidly adjusted. This dynamic adaptation resolves the contradiction between achieving high regenerative efficiency and preventing inertia shock.
Solution Approach 2:
The patent changes the parameter of transmission input rotational speed command value based on the operational region. By detecting whether the vehicle is in the brake switching region or regenerative braking region, the system applies different command value strategies: limiting the increase rate in the brake switching region to prevent discomfort, and allowing rapid adjustment in the regenerative braking region to maximize efficiency. This parameter change approach resolves the technical contradiction.
Data Source
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AI summary
Provided is a vehicle regenerative speed control device that prevents discomfort from being imparted to a driver who maintains a constant request operation after requesting an increase, when performing a regenerative speed control based on a request for an increase in the regeneration amount in a brake switching region due to a decrease in vehicle speed during deceleration. The present invention is equipped with a motor-generator (4) and a belt-type continuously variable transmission (6). This FF hybrid vehicle is provided with a hybrid control module (81) which, when there is a request for an increase in the regeneration amount while decelerating, performs a regenerative speed control for downshifting the belt-type continuously variable transmission (6) to the low gear ratio side, and increasing the rotational speed of a transmission input shaft to which the motor generator (4) is connected. The hybrid control module (81) also imposes the limitation of staying within a Pri end command rotational speed change rate for the Pri end command rotational speed when performing a regenerative speed control for increasing the Pri end command rotational speed based on a braking operation in a brake switching region for switching from regenerative braking to hydraulic braking due to a decrease in vehicle speed.