Hybrid Vehicle Torque Control for Stable Deceleration
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Solution Overview
Problem
In hybrid vehicles, the abrupt variation in maximum regeneration torque when the engine stops during braking leads to ineffective deceleration, as the hydraulic brake needs to compensate for the torque decrease, but its initial response is slower than the regeneration brake, resulting in inadequate vehicle deceleration.
Innovation Solution
A hybrid vehicle system that includes a control mechanism to calculate and manage the maximum regeneration torque based on vehicle speed, using a motor rotation speed calculating means, input limiting means, motor generator regeneration torque calculating means, and change value calculating means to set a maximum regeneration torque threshold, ensuring a stable torque output by comparing engine operation and engine stop regeneration torques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine stops during braking to improve fuel efficiency, then fuel consumption is reduced, but the maximum regeneration torque decreases abruptly causing ineffective deceleration
Solution Approach 1:
The control device predicts future engine stop events and proactively adjusts the regeneration torque command value before the engine actually stops. By calculating the difference between engine-operation and engine-stop maximum regeneration torques, the system prepares the regeneration brake in advance to maintain deceleration effectiveness, avoiding the harmful effect of abrupt torque changes.
Solution Approach 2:
The system dynamically adjusts the regeneration torque command value based on real-time engine operation state and predicted stop events. The control device continuously monitors engine parameters and modifies the regeneration torque output accordingly, transitioning smoothly between engine-operation and engine-stop states to maintain effective deceleration while improving fuel efficiency.
2Reliability
If the regeneration torque is limited based on battery input capacity, then battery degradation is prevented, but the maximum regeneration torque decreases causing insufficient braking force
Solution Approach 1:
The control device dynamically adjusts the regeneration torque command value within the battery input limit to maintain optimal braking force. By continuously monitoring battery state and engine operation conditions, the system optimizes the regeneration torque output to prevent battery degradation while ensuring sufficient braking force is available.
3Speed
If the hydraulic brake compensates for regeneration torque decrease, then deceleration effectiveness is maintained, but the overall braking system complexity increases
Solution Approach 1:
The control device uses feedback from engine state sensors and battery status to automatically adjust the regeneration torque command value. This closed-loop control system monitors the difference between engine-operation and engine-stop maximum regeneration torques and modifies the regeneration brake output accordingly, maintaining deceleration effectiveness without requiring additional braking 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
The system effectively suppresses variations in maximum regeneration torque when the engine stops, maintaining consistent deceleration and preventing abrupt changes, thereby enhancing braking effectiveness.
Implementation Method 1
a motor generator (motor) other than the engine as drive sources... a second motor generator (MG2)... power generated from the engine and the motor generator is output to a drive shaft
Implementation Method 2
a battery input limit value is calculated based on the state of the battery as an electricity storing means
Data Source
AI summary
A controller for a hybrid vehicle includes a maximum regeneration torque calculator which calculates a motor generator maximum regeneration torque necessary for supplying power to an electricity storer and calculates each of an engine operation maximum regeneration torque for operating an engine changing in accordance with a vehicle speed and an engine stop maximum regeneration torque and a change value calculator which sets an engine stop prohibition vehicle speed in which an engine is not stopped when a vehicle speed is equal to or faster than a predetermined vehicle speed and calculates a maximum regeneration torque when stopping the engine at the engine stop prohibition vehicle speed as a maximum regeneration torque change threshold value from the engine stop regeneration torque of the maximum regeneration torque calculator.