Regenerative Braking Slip Control via Reference Wheel Speed
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Solution Overview
Problem
Existing regenerative braking systems in vehicles face challenges in accurately controlling wheel slip, particularly in precarious grip conditions, as they rely on estimated reference speeds that may not account for tire deformation and microslips, leading to potential wheel locking or excessive slipping.
Innovation Solution
A method for controlling regenerative braking that estimates a partial slip parameter based on speed measurements from wheels experiencing only hydraulic braking, allowing for more accurate control by comparing speeds between wheels with and without regenerative braking, and adjusting the regenerative braking setpoint to maintain slip within a safe range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If regenerative braking is applied only to driving wheels, then energy recovery efficiency is improved, but wheel slip control accuracy deteriorates
Solution Approach 1:
The patent uses a reference wheel (non-driven wheel) as an intermediary to measure actual vehicle speed and calculate slip ratio. This reference wheel provides an accurate baseline for comparing driven wheel speed, enabling precise slip control during regenerative braking without requiring direct measurement on the driven wheels themselves.
Solution Approach 2:
The system continuously monitors the speed difference between driven wheels and reference wheels, calculates slip ratio in real-time, and adjusts regenerative braking torque accordingly. This closed-loop feedback mechanism ensures accurate wheel slip control while maximizing energy recovery from the driven wheels.
2Loss of energy
If regenerative braking setpoint is increased, then energy recovery is improved, but risk of wheel locking increases
Solution Approach 1:
The regenerative braking setpoint is dynamically adjusted based on real-time slip ratio calculations. The system continuously adapts the braking torque to maintain optimal slip conditions, increasing energy recovery when grip is sufficient and reducing torque when slip approaches dangerous levels, thereby preventing wheel locking.
Solution Approach 2:
The system changes the braking torque parameter dynamically based on calculated slip ratio. By monitoring the speed differential between driven and reference wheels, the control system adjusts the regenerative braking setpoint to keep slip within safe boundaries, balancing energy recovery with wheel locking prevention.
3Device complexity
If reference speed is taken from preloaded tables, then system complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
Instead of using complex calculations or preloaded tables, the patent employs a simple reference wheel as an intermediary to directly measure vehicle speed. This mechanical approach provides accurate real-time reference speed data without requiring complex algorithms, lookup tables, or GPS systems, thereby maintaining low system complexity while achieving high measurement precision.
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 enables more precise control of regenerative braking, reducing the risk of wheel locking and slipping by accurately accounting for slip conditions, thereby enhancing vehicle stability and safety.
Implementation Method 1
it is possible under certain conditions to use the electric motor as a generator and thus to obtain an electrical braking means
Data Source
AI summary
A method controls regenerative braking for a vehicle equipped with regenerative brakes and with a separate braking apparatus. The vehicle includes at least one first wheel and at least one second wheel. The separate braking apparatus is applied to the at least one first wheel and to the at least one second wheel. The regenerative brakes are applied to the at least one first wheel only. The method includes receiving a speed value of the first wheel and a speed value of the second wheel, estimating a value of a parameter representing a slip associated with the regenerative braking as a function of the speed value of the first wheel and as a function of the speed value of the second wheel, and forming a regenerative braking setpoint value as a function of the estimated value of the parameter representing slip associated with the regenerative braking.