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.When the driver adds more lock in a corner, CyberCar "knows" that the driverjust wants more steering.Near the limits of adhesion, CyberCar knows that theappropriate physical reaction is, in fact, some weight transfer to the front, either bytrailing throttle or a little braking, and a little less steering wheel lock.When the frontshook up again, CyberCar can immediately get back into the throttle and add a littlemore steering lock, all the while tracking the driver's desires through the intentionalsteering wheel in the cockpit.Similarly, in an oversteer situation, when the driver givesopposite steering lock, CyberCar knows what to do.First, CyberCar determines whetherthe condition is trailing throttle oversteer (TTO) or power oversteer (PO).It can do thisby monitoring tyre loads through suspension deflection and engine torque output overtime.In TTO, CyberCar adds a little throttle and counter steers.When the drive wheelshook up again, it modulates the throttle and dials in a little forward lock.In PO,CyberCar gently trails off the throttle and counter steers.All the while, CyberCarmonitors driver's intentional inputs and the physical status of the car at the rate ofseveral kilohertz (thousands of times per second).The very terms "understeer" and "oversteer" carry cybernetic implication, for these areterms of intent.Understeer means the car is not steering as much as wanted, andoversteer means it is steering too much.50The above description is within current technology.What if we get really fantastic?How about doing away with the steering wheel altogether? CyberCar, version II, knowswhere the driver wants to go by watching his eyes, and it knows whether to accelerateor brake by watching brain waves.With Virtual Reality and teleoperation, the driverdoes not even have to be inside the car.The driver, wearing binocular video displaysthat control in-car cameras (or even synthetic computer graphics) via head position, sitsin a virtual cockpit in the pits.Now we must ask how much cybernetics is desirable? Autocrossing is, largely, a puredriver skill contest.Wheel-to-wheel racing adds race craft--drafting, passing, deception,etc.--to car control skills.Does it not seem that cybernetics eliminates driver skill as afactor by automating it? Is it not just another way for the "haves" to beat the "have-nots"by out-spending them? Drivers who do not have ABS have already complained that itgives their competition an unfair advantage.On the other hand, drivers who do have ithave complained that it reduces their feel of control and their options while braking.Ithink they doth protest too much.In the highest forms of racing, where money is literally no object, cybernetics is alreadyplaying a critical role.The clutch-less seven speed transmissions of theWilliams/Renault team dominated the latter half of the 1991 Formula 1 season.But forsome unattributable bad luck, they would have won the driver's championship and theconstructor's cup.Carrol Smith, noted racing engineer, has been predicting for years thatABS will show up in Formula 1 as soon as systems can be made small and light enough[2].It seems inevitable to me that cybernetic systems will give the unfair advantage tothose teams most awash in money.However, autocrossers, club racers, and other grassroots competitors will be spared the expense, and the experience of being relieved of theenjoyment of car control, for at least another decade or two.AcknowledgementsThanks to Phil Ethier for giving me a few tips on car control that I might be able toteach to CyberCar and to Ginger Clark for bringing slip angle sensors to my attention.Notes1And the word play on 'dream' was too much to resist.(back)2Everywhere, 'he' means 'he or she,' 'his' means 'his or her,' etc.(back)3Also known as grip angle; see Part 10 of this series.(back)References[1] Patrick Borthelow, "Sensing Tire Slip Angles At the Racetrack," Sensors, (back)September 1991.[2] Carrol Smith, Engineer to Win, Prepare to Win, Build to Win, from (back)Classic Motorbooks, P.O.Box 1/RT021, Osceola, WI, 54020.51The Physics of Racing,Part 13: TransientsBrian Beckmanphysicist and member ofNo Bucks Racing ClubP.O.Box 662Burbank, CA 91503©Copyright 1992Obviously, handling is extremely important in any racing car.In an autocross car, it iscritical.A poorly handling car with lots of power will not do well at all on the typicalautocross course.A Miata or CRX can usually beat a 60's muscle car like a PontiacGTO even though the Goat may have four or five times the power.Those cars, whilemagnificently powerful, were designed for straight-line acceleration at the expense ofcornering.This month, we examine one aspect of handling, that of handling transient or short-lived forces.Usually, in motor sports contexts, the word "transient" means short-livedcornering forces as opposed to braking and accelerating forces.In broader contexts, itmeans any short-lived forces.Transients figure prominently in autocross.Perhaps the epitome of a transient-producing autocross feature is slalom, which requires a car and driver to flick quicklyfrom left to right and back again.Many courses also feature esses, lane changes,chicanes (dual lane changes), alternating gates, and other variations on the theme.All ofthese require quick cornering response to transients.Some sports cars, like Elans, MR2'sand X1/9's, are designed specifically to have such quick response.The general rule isthat these kinds of cars get you into a corner more quickly than do other kinds.Theyachieve their response with low weight and low polar moment of inertia (PMI).A chiefgoal of this article is to explain PMI.Most engineering designs are trade-offs, and designing for quick transient response isno exception.Light weight means, generally, a small engine.Low PMI means,generally, placing the engine as close as possible to the centre of mass (CM) as possible.So, many quick response cars are mid-engined, further constraining engine size.Withengine size, we get into another trade-off area: cost versus power.Smaller engines are,generally, less powerful.The cheapest way to get engine power is with size.A big,sloppy, over-the-counter American V8 can cheaply give you 300-400 ft-lb of torque.Getting the same torque from a 1.6 litre four-banger can be very expensive and will putyou firmly in the Prepared or Modified ranks.But, a bigger engine is a heavier engine,and that means a beefier (heavier) frame and suspension to support it.Therefore, thecheap way to high torque requires sacrificing some transient response for power.Thisdesign approach is typified by Corvettes and Camaros.The general rule is that thesekinds of cars get you out of a corner more quickly because of engine torque [ Pobierz caÅ‚ość w formacie PDF ]