Hybrid Vehicle Braking Torque Compensation via Hydraulic-Electric Coordination
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Solution Overview
Problem
Hybrid vehicles face challenges in maintaining consistent braking torque due to intrinsic variations in electric regenerative braking torque, which can disrupt driving comfort and safety, especially during gear shifts and thermal limitations, requiring seamless compensation between electric and hydraulic braking systems to comply with regulations.
Innovation Solution
A method where the drive system computer and hydraulic system computer engage in dialogue to automatically adjust hydraulic braking torque in response to changes in electric regenerative braking capacity, anticipating and offsetting reductions in electric torque during gear shifts, thermal limitations, and component failures to maintain consistent braking as requested by the driver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If regenerative braking torque is applied by the electric machine to recharge the battery, then energy recovery and fuel consumption reduction are improved, but braking torque continuity and driving comfort deteriorate during gear shifts and thermal limitations
Solution Approach 1:
The system anticipates gear shifts by receiving advance information from the gearbox control unit about upcoming ratio changes. Before the shift occurs, the hydraulic braking system is pre-adjusted to compensate for the upcoming loss of electric braking torque, ensuring continuous braking force without interruption or discomfort to the driver.
Solution Approach 2:
The brake control unit continuously monitors the actual braking torque by comparing the sum of electric and hydraulic braking torques against the driver's requested braking torque. When deviations are detected due to thermal limitations, peak capacity restrictions, or gear shifts, the system automatically adjusts the hydraulic braking torque to compensate, maintaining consistent overall braking performance.
2Loss of energy
If the electric machine operates at peak capacity to maximize regenerative braking, then energy recovery is improved, but braking torque stability deteriorates when thermal limitations or capacity restrictions are reached
Solution Approach 1:
The system continuously monitors the electric braking torque contribution and detects when thermal limitations or peak capacity restrictions cause deviations. The brake control unit receives information about these limitations from the drive system control unit and automatically compensates by adjusting hydraulic braking torque to maintain the requested overall braking torque, ensuring stability throughout the braking process.
Solution Approach 2:
The hydraulic braking system acts as an intermediary that compensates for variations in electric braking torque. When the electric machine cannot maintain its braking torque due to thermal or capacity limitations, the hydraulic system smoothly takes up the difference, ensuring the driver experiences consistent braking force without abrupt changes or instability.
3Reliability
If hydraulic braking torque is increased to compensate for electric braking torque loss during gear shifts, then braking torque continuity is improved, but system complexity increases due to coordination between control units
Solution Approach 1:
The control systems of the electric drive and hydraulic braking are merged into a coordinated unified system. The drive system control unit and brake control unit exchange information through standardized communication protocols, allowing them to function as an integrated braking management system that automatically balances electric and hydraulic contributions without requiring complex manual coordination.
Solution Approach 2:
The braking system is designed to be self-regulating through automated control algorithms. The brake control unit independently calculates the required hydraulic braking torque based on the driver's request and the actual electric braking contribution, automatically adjusting parameters without external intervention. This self-service capability reduces the need for complex inter-control-unit coordination while maintaining braking torque continuity.
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
Ensures transparent and seamless torque compensation, maintaining driving comfort and safety by ensuring consistent braking torque levels, even during gear shifts and power variations, thus adhering to regulatory standards.
Implementation Method 1
The regenerative braking torque, also known as electric braking torque, is applied to the wheels by the action of an electric machine acting as a generator to recharge a battery to which it is connected
Implementation Method 2
The hydraulic braking torque is applied to the wheels by means of a hydraulic system that transforms the pressure on the brake pedal into a force capable of actuating pads (or a drum) against elements that rotate with the wheels
Data Source
AI summary
The invention relates to a braking method for a hybrid vehicle (1) comprising a drivetrain (3) controlled by a drivetrain computer (12), and a hydraulic braking system (15) controlled by a braking computer (21). In this method, as soon as the drivetrain computer (12) detects that the electrical braking torque is decreasing, this drivetrain computer (12) informs the hydraulic braking computer (21) of the value of the reduction in electric braking torque. The braking computer (21) then operates the hydraulic braking system (15) in such a way that the hydraulic braking torque applied to the wheels (2) by the brakes (17) compensates for this reduction in electric braking torque.