Recuperative Brake Pressure Control for Smooth Blended Deceleration
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Solution Overview
Problem
Conventional recuperative brake systems experience undesirable pressure fluctuations and deviations in brake cylinders during transitions between electric motor and hydraulic braking, leading to uncomfortable driving experiences and inefficient energy consumption.
Innovation Solution
A control device and method that utilizes an electronic device to manage differential pressure control by defining target current strengths and differential pressures, smoothing the transition between electric motor and hydraulic braking modes, and compensating for component tolerances and aging effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If differential pressure control is executed by alternating between providing overcurrent and undercurrent to wheel inlet valves, then brake pressure can be regulated, but wavelike pressure increases occur in the brake cylinders
Solution Approach 1:
The patent applies periodic action by using alternating overcurrent and undercurrent pulses to the wheel inlet valves during differential pressure control. This periodic current application enables the valves to modulate brake fluid flow rhythmically, achieving precise brake pressure regulation while avoiding continuous high-current operation that would cause thermal effects and energy waste.
Solution Approach 2:
The patent changes the current parameter characteristics by switching between overcurrent and undercurrent states in a controlled periodic manner. This parameter variation allows the wheel inlet valves to dynamically adjust their opening degree, enabling precise control of brake pressure buildup and preventing unwanted wavelike pressure fluctuations through optimized current pulse timing and magnitude.
2Ease of operation
If the second wheel outlet valves are kept open during recuperative braking, then brake pressure buildup is prevented, but pressure drops in the first wheel brake cylinders occur when second axle braking is activated
Solution Approach 1:
The patent applies preliminary action by keeping the second wheel outlet valves in the open state during recuperative braking phases before the second axle braking is activated. This preliminary valve positioning prevents brake pressure buildup in advance, and the system is designed to smoothly transition valve states when braking demands change, thereby avoiding sudden pressure drops when second axle braking becomes necessary.
Solution Approach 2:
The patent implements dynamic control of the second wheel outlet valves by continuously adjusting their opening state based on real-time braking demands. The valves transition from open during recuperative braking to closed when second axle braking is activated, and this dynamic adaptation ensures smooth pressure management across different operating phases, preventing both pressure buildup and unwanted pressure drops.
3Force
If target brake pressures are defined for both axles during strong braking, then sufficient deceleration force is achieved, but pressure deviations between actual and target pressures increase
Solution Approach 1:
The patent applies segmentation by dividing the brake system into two independent axle systems with separate pressure control loops. Each axle has its own wheel inlet and outlet valves that can be controlled independently. This segmentation allows the system to define and maintain different target brake pressures for the first and second axles simultaneously, achieving sufficient total deceleration force while maintaining precise pressure control in each axle through independent differential pressure regulation.
Solution Approach 2:
The patent implements feedback control by continuously monitoring actual brake pressures in both axles and comparing them with target pressures. The control device adjusts the current signals to the wheel inlet and outlet valves based on the pressure deviations detected, enabling closed-loop control that maintains high pressure accuracy even when strong braking forces are required from both axles simultaneously.
Data Source
AI summary
A control device and method for a recuperative brake system of a vehicle. In the method, if a requested vehicle deceleration can only partially be produced using at least one electric motor, a differential pressure control is carried out in the wheel brake cylinders, including: defining a target differential pressure for first and second wheel brake cylinders, actuating at least one wheel inlet valve arranged upstream of the second wheel brake cylinders, using a current signal output to the wheel inlet valve taking into consideration the defined target differential pressure, and defining a target current strength of the current signal taking into consideration the defined target differential pressure. The target current strength of the current signal or the initial value of the target current strength is selected from a set of values including at least three current strength values, taking into consideration the defined target differential pressure.