TRW introduces second generation brake system for hybrids/EVs
One of the key functions necessary to maximize the capability of hybrid and electric vehicles is regenerative braking. For those who haven't been paying attention, regenerative braking uses the property of electric motors where mechanically driving the motor causes it to act as a generator producing electric current. In order to facilitate this, a brake system that can monitor the driver's braking request and then seamlessly blend the maximum amount of regenerative braking with a corresponding amount of friction is needed. All of the major electronic braking system suppliers including Bosch, Continental Teves and TRW have developed such systems. TRW's system, dubbed Slip Control Boost (SCB) had its first production application on the General Motors two-mode hybrid SUVs and the fuel cell Equinox that is being used for Project Driveway. Because hybrids and EVs don't necessarily have a vacuum source available for brake boost, the SCB system incorporates a hydraulic brake booster and a high pressure accumulator to supply brake pressure on demand. SCB also provides full slip control functionality, including ABS, traction control and stability control. TRW has just announced a second-generation version SCB2 that is 25 percent smaller and lighter than the original. The SCB2 system can also be used on diesel vehicles to replace the vacuum pump or hydraulic assist systems for the brakes. This should also be a lower cost which will contribute to automakers reducing the costs of their hybrid and electric vehicles. Full disclosure: prior to becoming a full-time writer last year, I worked as a controls software engineer at TRW and worked on the original SCB system.
[Source: TRW]
Reader Comments (Page 1 of 1)
GoodCheer 10:44AM (10/23/2008)
Having driven an EV with very strong regen*, I can tell folks that
-yes, it feels pretty weird when you start driving, and
-yes, you get used to it pretty quickly, and driving with one pedal becomes just as intuitive as driving with two pedals after a block or two.
All of which is to say that a separate box to manage regen and tie it into the brakes does not make a whole lot of sense to me. Regen can be managed perfectly well by the existing power electronics and actuated through the throttle pedal.
*We have an ACPropulsion eBox. There is an on-dash slider to adjust the amount of regen from near zero to stronger than I almost ever use the brakes in my Civic.
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paulwesterberg 12:38PM (10/23/2008)
I think it makes sense to have some limited regen kick in when you let off of the "gas" pedal, but I also think that having a module to manage braking with max regen will help improve efficiency.
The way I understand it - your ebox does:
no gas -> user selectable regen is applied.
0 to hard brake -> seleced regen + min to max mechanical braking
what system could do:
no gas -> limited regen
0 to medium brake -> limited to max regen
medium to hard brake -> max regen + min to max mechanical braking.
The electronic control system is helpful to seamlessly blend regen with mechanical braking so applying the brake slows the car in a smooth and controlled fashion.
In addition the braking force needed by the front wheels(regen) and the rear wheels(mechanical) needs to be managed for maximum efficiency, stability & control.
ieee has a research paper on this(membership needed to login, I am not a ee).
http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel5/9338/29652/01348863.pdf?tp=&isnumber=&arnumber=1348863
Perry 5:13PM (10/24/2008)
I dont think the general public is smart enough for an adjustable regen switch.
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