Method for measuring vehicle motion resistances using short distance coast-down test based on the distance-time data

• US 5,686,651 A
• Filed: 02/06/1996
• Issued: 11/11/1997
• Est. Priority Date: 02/10/1995
• Status: Expired due to Fees

• Current Assignee: Korea Advanced Institute of Science and Technology
• Original Assignee: Korea Advanced Institute of Science and Technology
• Inventors: Patrushov, Vladimir A., Hur, Nahmkeon, Ahn, Ieeki
• Primary Examiner(s): RAEVIS, ROBERT R
• Application Number:
  US08/597,173
• Time in Patent Office: 644 Days
• Field of Search: 73/9, 73/147, 73/117, 73/117.1, 364/425, 364/506
• US Class Current: 73/9
• CPC Class Codes: B60W 2530/16 Driving resistance
• CPC Class Codes: G01M 17/007 Wheeled or endless-tracked vehicles G01M17/08 takes precedence
• CPC Class Codes: G01M 9/00 Aerodynamic testing; Arrangements in or on wind tunnels
• CPC Class Codes: G01P 3/68 using optical means, i.e. using infrared, visible, or ultraviolet light G01P3/80 takes precedence ; by reflection of waves G01S17/58
• CPC Class Codes: Y02T 10/60 Other road transportation technologies with climate change mitigation effect

Abstract

The present invention is related to a method for measuring vehicle motion resistances using the vehicle coast-down testing method. More specifically, the initial coast-down speed of the vehicle is divided into a low speed range and a high speed range. Each range is tested to obtain physically meaningful test variables for each range. By combining the obtained variables, the length of the test road required for previous coast-down test methods can be significantly reduced. Additionally, vehicle motion resistances may be more accurately measured and analyzed.

Claims

1. A method for measuring total motion resistances of a motor vehicle, wherein the resistances are comprised of transmission loss, rolling loss and aerodynamic loss, comprising:

(a) raising the vehicle from the ground;

(b) applying power from a vehicle engine to cause a driving wheel of the vehicle to rotate;

(c) stopping the power applied to the driving wheel thereby allowing the driving wheel to freely rotate;

(d) acquiring a first set of distance-time data from the rotation intervals of the driving wheel;

(e) determining at least three measuring points on a vehicle coast-down test road, wherein the measuring points are determined prior to a point at which the vehicle comes to a rest;

(f) allowing the vehicle to coast-down the test road with an initial vehicle velocity V_i ;

(g) acquiring a second set of distance-time data as the vehicle passes the measuring points during coast-down;

(h) determining the total resistances of the vehicle in accordance with

space="preserve" listing-type="equation">(ρ

/g)(dV/dt)=a+bV+cV.sup.2

where ρ

is air density, V is vehicle velocity, g is gravitational acceleration, a is a coefficient relating to rolling and transmission loss, b is a coefficient relating to transmission loss, and c is a coefficient relating to aerodynamic and rolling loss; and

coefficient b is determined from the first set of distance-time data in accordance with;

##EQU16## and coefficients a and c are determined from the second set of distance-time data in accordance with;

##EQU17## where T_i is the time taken for said vehicle to travel between an i-th measuring point to a final measuring point among the predetermined points on a test road and T₁ is the time taken for the vehicle to come to a complete stop from the final measuring point; and

space="preserve" listing-type="equation">h=(gb)/(2δ

), h.sub.o =gb/δ

.sub.0, B=(gA/2δ

), ##EQU18## δ

=+ f=1+{(nI.sub.W +I.sub.d)g/WR.sup.2 }, δ

.sub.0 =(MI.sub.W +I.sub.d)g/(WR.sup.2),

a=τ

₀ +f₀

c=k=(ρ

C_d F)/(2gW); and

where τ

₀ is a constant term of transmission loss, f₀ is a constant term of rolling resistance, k is a coefficient of rolling resistance proportional to the square of the vehicle velocity, n is total number of the wheels, m is number of the driving wheels, I_W is moment of inertia of one wheel, I_d is moment of inertia of transmission excluding the wheels, R is dynamic radius of the wheels, W is vehicle weight, F is frontal area of the vehicle, and C_d is drag coefficient.

2. The method for measuring total motion resistances of a vehicle according to claim 1, wherein the V_i of step (f) comprises a low initial velocity V_iL and a high initial velocity V_iH ;

the second set of distance-time data of step (g) is acquired for V_iL and V_iH as the vehicle passes the measuring points during coast-down; and

the total resistances of the vehicle are determined in step (h) in accordance with;

space="preserve" listing-type="equation">(ρ

/g)(dV/dt)=a.sub.iL +bV+C.sub.iH V.sup.2,

where a_iL is a coefficient calculated from the second set of distance-time data of step (g) when the initial velocity is V_iL, and C_iH is a coefficient calculated from the second set of distance-time data of step (g) when the initial vehicle velocity is V_iH.

3. The method for measuring total motion resistance of a vehicle according to claim 1, wherein step (a) further comprises affixing first reflection means on the driving wheel of the vehicle and mounting first sensing means at a position near the driving wheel;

and step (e) further comprises affixing second reflection means onto the determined points and mounting second sensing means on the vehicle.

4. The method for measuring total motion resistance of a vehicle according to claim 2, wherein step (a) further comprises affixing first reflection means on the driving wheel of the vehicle and mounting first sensing means at a position near the driving wheel;

and step (e) further comprises affixing second reflection means onto the determined points and mounting second sensing means on the vehicle.