Vehicle Braking Torque Coordination and Energy Regeneration
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Solution Overview
Problem
Existing vehicle braking systems experience torque shock and inefficient energy regeneration due to rough coordination between motor regenerative torque and hydraulic braking force, especially at low vehicle speeds and strict battery charging limits.
Innovation Solution
A vehicle braking system that includes a lower limit regenerative torque setting unit and a braking control unit to limit regenerative torque based on the motor's rotation speed, input limit, and braking request, ensuring smooth coordination between motor and hydraulic braking forces and maximizing energy regeneration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the torque command of the motor is set by the charging limit value only of the battery, then the motor is controlled to output a large regenerative torque, but hydraulic driving takes a certain time, thereby preventing smooth coordination between the braking force by the motor and the braking force by the machine brake, which may cause torque shock
Solution Approach 1:
The patent applies preliminary action by predicting the future regenerative torque based on the current rotation speed and acceleration, and using this predicted value to set the torque command in advance. This allows the braking control to anticipate changes in motor torque and coordinate smoothly with the hydraulic brake, preventing torque shock while maintaining energy regeneration efficiency.
Solution Approach 2:
The patent implements dynamics by continuously adjusting the torque command based on real-time changes in rotation speed and acceleration. The braking control unit dynamically modifies the torque command to maintain optimal coordination between regenerative braking and hydraulic braking, ensuring smooth braking performance across varying operating conditions.
2Productivity
If the motor is controlled to output a large regenerative torque at low rotation speed, then energy regeneration is maximized, but the coordination with hydraulic brake becomes rough, causing torque shock
Solution Approach 1:
The patent uses preliminary action by calculating predicted regenerative torque based on current rotation speed and acceleration trends. This prediction allows the system to prepare appropriate torque commands in advance, ensuring smooth transitions and coordination with hydraulic braking, thereby eliminating torque shock while maintaining maximum energy regeneration.
Solution Approach 2:
The patent applies feedback by continuously monitoring rotation speed and acceleration, and using this information to adjust the torque command dynamically. The braking control unit uses feedback from the motor's actual performance to refine the torque command, ensuring optimal energy regeneration without causing torque shock.
3Reliability
If strict battery charging limit is applied, then battery protection is ensured, but the regenerative torque is limited, reducing energy regeneration efficiency
Solution Approach 1:
The patent implements dynamics by dynamically adjusting the torque command within the battery charging limit based on real-time operating conditions such as rotation speed and acceleration. This allows the system to maximize energy regeneration within safe battery charging boundaries, adapting to changing conditions while protecting the battery.
Solution Approach 2:
The patent applies parameter changes by modifying the torque command parameters based on the battery charging limit and current operating state. The system adjusts key parameters like torque magnitude and timing to optimize energy regeneration while respecting battery constraints, thereby balancing battery protection with energy recovery efficiency.
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
Prevents torque shock and enhances energy efficiency by ensuring smooth coordination between motor and hydraulic braking forces, effectively regenerating kinetic energy into electric power during braking.
Implementation Method 1
at least one motor MG2, MG3 that can output a regenerative torque
Implementation Method 2
a braking force application unit that applies a braking force by hydraulic actuation
Implementation Method 3
a braking force application unit that applies a braking force by hydraulic actuation
Data Source
AI summary
During braking, lower limits Tm2min and Tm3min are set based on an input limit Win of a battery and a brake pedal position BP (S190), and the set lower limits Tm2min and Tm3min limit regenerative torques output from motors MG2 and MG3 (S220). This prevents an output of an excessive braking force and torque shock caused by a hydraulic brake being not able to follow sudden changes in the regenerative torques output from the motors MG2 and MG3 when the vehicle speed is reduced.