Electric Wheel Slip Control for Regenerative Braking Stability
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Solution Overview
Problem
Existing systems for electrically driven vehicles struggle with complex and energetically suboptimal slip control, particularly during regenerative braking, which can lead to wheel locking and instability, and often require additional sensors or complex procedures that are not universally available.
Innovation Solution
A method and device for slip control that uses torque control via an electric drive to adjust drive torques for accelerating or braking, determining wheel slip instability, and regulating it to a target slip value, allowing for energy recuperation without relying on friction brakes, and prioritizing lateral force transmission for stable vehicle control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If regenerative braking torque is applied to recover kinetic energy, then energy recuperation efficiency is improved, but wheel locking tendency increases leading to vehicle instability
Solution Approach 1:
The control system continuously monitors wheel slip values and compares them against threshold criteria. When instability is detected (wheel slip exceeds threshold), the system provides feedback to reduce regenerative braking torque and activate friction brakes. This closed-loop feedback mechanism maintains energy recuperation efficiency while preventing wheel locking and vehicle instability.
Solution Approach 2:
The braking system dynamically adjusts the distribution between regenerative braking and friction braking based on real-time wheel slip conditions. The control method enables smooth transitions between braking modes, optimizing energy recovery during stable conditions while automatically engaging friction brakes when instability is detected, thus maintaining both energy efficiency and vehicle stability.
2Reliability
If ABS control mechanism is activated to prevent wheel locking, then vehicle stability is improved, but energy recuperation is lost and system complexity increases
Solution Approach 1:
The system dynamically determines whether to activate friction brakes based on real-time wheel slip assessment. Instead of continuously engaging friction brakes as in traditional ABS, the method selectively activates them only when wheel slip exceeds stability thresholds, thereby maintaining vehicle stability while maximizing energy recuperation during normal braking operations.
Solution Approach 2:
The control method changes the operational parameters of the braking system by introducing wheel slip-based activation criteria for friction brakes. This parameter change allows the system to operate in regenerative braking mode under most conditions, improving energy efficiency, while switching to friction brake assistance only when stability requirements demand it.
3Reliability
If friction brakes are used for slip control, then wheel lock prevention is achieved, but energy efficiency deteriorates due to reliance on mechanical braking
Solution Approach 1:
The system dynamically selects the optimal braking mode by continuously assessing wheel slip conditions. Friction brakes are used selectively only when wheel slip indicates impending lock-up, while regenerative braking handles the majority of braking energy recovery. This dynamic mode selection achieves reliable wheel lock prevention while minimizing energy loss to mechanical friction.
Solution Approach 2:
The invention replaces traditional mechanical ABS systems with an electric drive-based slip control mechanism. Instead of relying solely on friction brakes with complex ABS control, the system uses the electric drive motor to provide regenerative braking torque and actively control wheel slip, thereby reducing dependence on mechanical braking and improving overall energy efficiency.
4Measurement precision
If additional sensors are added to improve slip control accuracy, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The system utilizes existing wheel speed sensors and vehicle dynamics data already present in electric vehicles to calculate wheel slip values. By self-generating the necessary control information from available data sources and applying slip-based control logic, the invention achieves accurate slip control without requiring additional specialized sensors, thereby maintaining measurement precision while avoiding increased device complexity.
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
This approach ensures reliable detection and stabilization of vehicle instability during braking, enabling efficient energy recovery and maintaining steerability and lateral guidance without additional sensors, prioritizing transverse force transmission over longitudinal control.
Implementation Method 1
torque control via an electric drive acting on the respective vehicle wheel, with actual drive torques or forces having both an accelerating and a braking effect
Implementation Method 2
The regenerative braking torque of the electric drive, i.e. recuperation, can lead to a tendency for the wheel to lock up
Data Source
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AI summary
The invention relates to a method for slip loop control of a vehicle wheel driven via an electrical drive, comprising at least the following steps: - controlling the electrical drive of the vehicle wheel with an actual drive torque (M2) in a torque control mode in a torque control step (St1), - determining a wheel speed (n) and a wheel slip (s) of the vehicle wheel and evaluating the wheel slip (s) by means of an instability criterion (K1) as to whether there is any instability (St3), - if any instability is identified, directly or indirectly transitioning into a slip loop control mode to control the wheel slip (s) to a specified slip (s-soll) by controlling the electrical drive (St4, superimposed slip loop control step), - determining whether an end criterion (K3) for ending the slip loop control mode is met (St5), - if the end criterion (K3) is met, returning to the torque control mode in the torque control step (St1).