SH-AWD
Rather clever transmission system unveiled by Honda
Honda are to introduce a bonkers clever transmission system into their new cars. This week they've announced the development of a new "Super Handling All-Wheel Drive" system.
SH-AWD uses electro magnetic clutches to control power delivery and the split of torque to all four wheels.
The new system will be available this fall in the Acura RL (North America) and the Legend (Japan).
By monitoring driver input and driving conditions, the SH-AWD system determines the optimum front-rear and lateral torque distribution. This information is then conveyed to the rear differential, where direct electromagnetic clutches continuously regulate and vary front-rear torque distribution between ratios of 30:70 and 70:30, and lateral torque distribution in the rear wheels between ratios of 100:0 and 0:100. Torque is used not only for propulsion, but for cornering as well, resulting in a significant enhancement in vehicle manoeuvrability.
The SH-AWD system is composed of sensors to detect steering angle, lateral g, and other vehicle information; an ECU; and the rear differential. The direct electromagnetic clutches inside the rear differential, another world’s first, employ electromagnets to obtain precise control over the multi-plate clutches. Built-in search coils monitor the gaps between the electromagnets and the magnetic body to achieve precise, continuously variable torque regulation.
Super clever Differential
The rear differential is also equipped with a built-in acceleration device, yet another world’s first. During cornering, the track of the outside rear wheel normally falls outside the average of the tracks of the front wheels. The outside rear wheel does not rotate fast enough to keep up with the front wheels, preventing efficient transmission of torque. To counteract this problem, the SH-AWD acceleration device alters the gearing to speed up the outside rear wheel’s rotation relative to the front wheels. This reduces torque transmission losses and significantly improves vehicle manoeuvrability.
Damn clever those Japs in white coats.
electronic brain using various sensors determines how power should flow, and implements it via electromagnetic clutches, alleviating the wet-clutch type differentials that require pumps and complicated fluid flow to do their work. In addition, there is a system incorporated (the "acceleration device") into the differential, that, based on a difference in LATERAL acceleration at the rear relative to the front, alters the torque split so that that wheel doesn't rotate out of line with the front wheels, meaning that the tire follows a line on which it can roll forwards as opposed to drag. So it kills oversteer electrically.
brilliant. but it was a dreadfully underspecific description. I can guarantee you that there are people reading this thinking "acceleration device? I wonder if I can bolt that onto my civic? wonder how many hp it's good for?" I'll say it again another way, as I believe it to be: It's a mechanical device that uses notice of rear end translation (sideways acceleration, nothing to do with wheel movement), to change the torque split. It's reactionary, so it isn't as a good as a torsen, something that would react based on what's going on at the axle level, so it'll allow some play, (it has to HAVE some "fishtailing" motion to be able to have something to fix), but it may be limiting. So the car won't be handling as if on rails, which is what an audi a6 v8 may feel like, but it'll accelerate the wheels by way of reproportioning torque mechanically through electrically engaged clutches.
I know it's different, but the more I say it out loud as a concept, it just keeps reminding me of the ATTS on the prelude. Only inversely, b/c this is about removing excess rotation at the outside wheel. ATTS uses the relative lack of rotation at the inside wheel to push the torque across to the outside wheel to whip the car around, almost creating pivoting on the inside wheel as an exponential effect......
ok... the blabbering (to myself with you, the gassing station typist as my audience) is starting to make this shit make sense. I really like it. I bet it'll work like crazy, and this'll probably filter down into lesser models as honda removes fwd as a standard expectation of models in the brand. hell, who knows, even the next NSX may have this, right? ok, maybe not.
article said:
During cornering, the track of the outside rear wheel normally falls outside the average of the tracks of the front wheels. The outside rear wheel does not rotate fast enough to keep up with the front wheels, preventing efficient transmission of torque.
Depending on your chosen reference point, all of the wheels are either too fast or too slow, and I can't work out what makes the outside rear special.
The Honda device actively controls the torque / wheelspeed across the back axle and between the front and rear axles so that no energy is lost.
I think this makes sense. Anyways, it's bloody clever either way.
Roop
article said:
During cornering, the track of the outside rear wheel normally falls outside the average of the tracks of the front wheels. The outside rear wheel does not rotate fast enough to keep up with the front wheels, preventing efficient transmission of torque.
danmangt40 said:
alters the torque split so that that wheel doesn't rotate out of line with the front wheels, meaning that the tire follows a line on which it can roll forwards as opposed to drag. So it kills oversteer electrically.
Don't think so. The way I read it is that the diff automatically ensures the outside rear wheel spins faster than the others to take account of the fact that its travelling on a bigger circle. So it kills understeer.
anoakes said:
alters the torque split so that that wheel doesn't rotate out of line with the front wheels, meaning that the tire follows a line on which it can roll forwards as opposed to drag. So it kills oversteer electrically.
Don't think so. The way I read it is that the diff automatically ensures the outside rear wheel spins faster than the others to take account of the fact that its travelling on a bigger circle. So it kills understeer.
And yet Lotus managed to solve the whole snap oversteer/understeer problem with their Raft Subframe system, without having to resort to debilitating electronics and keeping the driving experience pure.
Impressive setup, yes, but I can imagine you'll feel like you're being distanced from the car's limits.
Looks safety-adding value, maybe even sporty . . . I'll wait and read the review. Acura RL AWD sounds nice . . .
Also Consider:
Audi A6/allroad quattro
BMW 5-Series
Lexus LS 430
Mercedes-Benz E-Class
Mmmmmh . . .
dinkel said:
Ronnie Peterson . . . (who remembers him?)
www.pgan.com/andrew/downloads/RonniePeterson.pdf
Geoff
Mind you, manufacturers who ought to know better still can't make cars go round bumpy bends in a sensible fashion so heaven knows what they'll make of all that.
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