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= Regenerative Braking Strategy = From Wikipedia, the free encyclopedia

Also see, Regenerative brake

A regenerative braking strategy (RBS) is any logic based system implemented to advance the effectiveness of energy savings of an energy recovery mechanism. A regenerative braking strategy can take on many forms whether it be purely software based, purely hardware based, or a hybrid of the two. RBS’s primary objective are to achieve better fuel economy, but also to lower exhaust emissions as well.

General
The primary function of a regenerative braking strategy is to maximize the efficiency of a regenerative braking system. This translates to increased driving distance given the same amount of starting power as an identical vehicle without an applied RBS. This idea of maximizing driving distance and consequently vehicle power is a primary industry driving force for innovation. In general there are two fundamental schools of thought when applying a logic controller to a regenerative braking system, those are Boolean (binary) logic and Fuzzy (variable) logic. As Fuzzy logic gives a more accurate/realistic approach to the changing real world conditions, it is the most promising RBS in use and study.

Boolean logic based RBS
Boolean logic is a controller style that deals in absolute binary truths. In this case a condition is either met or is not met and the RBS behaves accordingly. For example, once the brakes of an electric vehicle are engaged the Regenerative braking system is activated at a constant rate until the brake pedal is no longer depressed.

https://fahmizaleeits.files.wordpress.com/2010/04/boolean_vs_fuzzy.jpg

Fuzzy logic based RBS
Fuzzy logic controllers are particularly well suited for regenerative braking systems as shown through research at Oakland University. A fuzzy logic controller operates under “degrees of truth” between 0 and 1. Unlike Boolean logic this accommodates component variability and imprecise measurements. Referencing the example from Boolean logic, fuzzy logic contrasts by allowing different intensities of regenerative braking to occur giving a much more structured and precise methodology for an RBS.

Hybrid Systems
Hybrid vehicles are becoming increasingly commonly used in the automotive industry in the last decade. Hybrid systems are a combination between an internal combustion engine and an electric motor. There are three configurations for hybrid systems:

·        Series Configuration: an Internal Combustion Engine generator combination is utilized to provide electric power to the Electric motor and battery.

·        Parallel Configuration: uses the Internal Combustion Engine to directly connect to the wheels mechanically to provide increased torque.

·        Series-Parallel Configuration: uses a combination of both systems to operate.

LF620 Prototype
The LF620 Prototype is an electric vehicle used in a Chinese study on the effects of Fuzzy Logic control on an electric vehicle. In their study, the researchers classify two approaches to coordinate the "regenerative torque" of the electric motor and "friction torque" of the hydraulic unit: parallel and series. In a parallel braking style, the regenerative braking is used directly in addition to the normal hydraulic brakes on the axle. Series acts differently in that it allows for independent modulation of the hydraulic brakes to each axle based upon the amount of regenerative braking force. Series style arrangement fundamentally allows for greater recovery of kinetic energy since the hydraulic brakes are adjusted intensity based on what the regenerative brakes cannot provide instead of using maximum hydraulic (non-recoverable) braking force.