How ABS works in regenerative braking

9394

I'm just wondering how ABS works in regenerative braking, especially in snowy/icy condition.

The fact that regenerative braking only slows down the driving wheels (front 2 wheels on FWD model), does it make it easier to lock up and slide on slippery surface ?

thecardoc3

If the ABS detects any wheel slippage, then regenerative braking is shut down and the ABS module commands a vehicle stop with only the service brakes. When the driver applies the brakes on a full hybrid he/she is really only telling a computer what they want, the computer then decides how to slow the vehicle. The normal strategy will be for the ABS controller to command the transaxle controller to go into "regen" (regenerative braking) mode with the drive wheels while the ABS module applies the rear brakes just enough to keep the vehicle balanced. That works up to a point because regen is only capable of just so much torque, so if the driver is braking hard enough then the service brakes can be applied as well as having some regenerative braking effort. Harder yet and then regen shuts down and only the service brakes would be utilized. Since the ABS module is the prime controller, any wheel slippage is reacted to just like any non hybrid car.

9394

@thecardoc3
thanks for the info.

i read a paper written by an engineering student in 2011 regarding ABS in regenerative braking system, apparently the EV system can detect and release wheel lockup much quicker than mechanical ABS, and still maintains regen, just wondering if this technology is already implemented in today's EVs?

thecardoc3

There is a difference between what the full EV's can do and what the hybrids typically do. An EV typically has a direct one to one drive ratio with the wheels. Combine that with the wheel speed sensors and the drive motor position sensor and it would be easy for the electronics to detect and control wheel slip. Going back to hybrids where you have two motor/generators and the IC (internal combustion engine) connected via a planet assembly there is too much shock loading that can take place in the planet assembly if a wheel gets into a condition where anti-lock operation is required so the normal routine is to shut down the regenerative braking. If engineering has gotten past the prior limitations we haven't heard about it yet.