System and method for measuring the grip performance of a vehicl

Details System and method for measuring the grip performance of a vehicl System and method for measuring the grip performance of a vehicl

1996-09-27

1998-10-13

Dombroske, George M.

Measuring and testing

Dynamometers

Responsive to force

280688, G01M 1704

Patent

active

058214348

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to a system and method for measuring the grip performance of a vehicle, such as a passenger car, a racing car, a motorcycle, or the like, through relation to a lumped-sum parameter derived from force and linear and/or angular displacement measurements taken from selected elements forming the suspension of the vehicle. In deriving this parameter as representative of the time dependent grip forces developed between the tire of the car and the surface of the road, the present invention establishes a criteria for comparing and optimizing the ultimate effects of mechanical and aerodynamic changes or adjustments made in the car or to its components, and additionally allows for the determination of the absolute values of the forces acting upon each wheel of the car and for the comparison of road surface grip.
The measurement of what may be termed as the "performance" of a car is a problem which has long perplexed both the car engineer and the tire designer alike. Broadly, the overall performance of a car may be based on any or all of its front and rear braking, acceleration, and cornering response. Improvements in performance may be effected by improving the fixed mechanical and aerodynamic design parameters of the car, and/or by dynamically compensating for inadequacies in such design by using computationally controlled corrective systems such as anti-locking brakes, traction control, and active ride height systems. Thus far, however, the performance analysis of the design or corrective system has lagged behind the design itself for want of analytical data and criteria upon which an improvement in performance might be determined. Complicating the matter is that the individual responses which combine to give a car its overall performance each depend not on one parameter, but ultimately upon a complex, three-dimensional interaction between innumerable variables such as: the design and construction of the tires; the design of the mechanical systems, chassis, suspension, and frame including mass distribution and aerodynamic effects; and the road and driving conditions including the road surface and ambient temperature. The interactive effects of each of these variables must be considered by any system which would be capable of measuring car performance.
Heretofore, attempts at measuring and managing car performance have focused either on subjective "seat of the pants" and trial-and-error techniques, or more recently on complex computational modeling directed to simulate at least some of the interactive variables affecting the braking, acceleration, and cornering responses of the car. The complexities of the interactions between those variables, however, have proved unmanageable at best to even approximate car performance. For example, even with the mechanical systems and aerodynamic components of a given car left unchanged, such transient phenomena as variations in road or track and ambient conditions appreciably affect car performance to a degree, at least in auto racing, which can be the measure between winning and losing. As illustrative of the complexities involved in computationally modeling car performance, Table 1 lists only a few of the elements which must be considered as affecting the grip, balance, or drag of the car.


TABLE 1 ______________________________________ System or Condition Variable or Measurement ______________________________________ Tires Instantaneous camber as affected by camber change characteristics, static settings, car roll, car structural integrity, Ackerman steering geometry, steering angle, and tire load Instantaneous toe in or out as affected by dynamic toe change, static toe selling, car structural integrity, and tire load Instantaneous tire pressure Tire mileage or wear as affecting acceleration, lateral cornering, and steady-state running. Tire temperature and temperature distribution Mechanical Weight distribution and front and rear sprung and unsprung weight as affected by fuel load

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