IPC분류정보
국가/구분 |
United States(US) Patent
등록
|
국제특허분류(IPC7판) |
|
출원번호 |
UP-0192619
(2008-08-15)
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등록번호 |
US-7784334
(2010-09-20)
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발명자
/ 주소 |
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출원인 / 주소 |
- Ford Global Technologies, LLC
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대리인 / 주소 |
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인용정보 |
피인용 횟수 :
1 인용 특허 :
8 |
초록
A method for controlling a biaxial wheel test machine used for simulating loads experienced by a test wheel under actual driving conditions and for obtaining an accurate determination of wheel camber angle.
대표청구항
▼
What is claimed: 1. A method for determining camber angle on a biaxial wheel test machine that simulates loads experienced by a wheel under driving conditions comprising: determining a dynamic roll radius value with an axial load and a camber angle held constant and determining a change of radial p
What is claimed: 1. A method for determining camber angle on a biaxial wheel test machine that simulates loads experienced by a wheel under driving conditions comprising: determining a dynamic roll radius value with an axial load and a camber angle held constant and determining a change of radial position in response to unit changes of a radial load; determining a radial stiffness value by determining a ratio of the radial position change in response to unit changes of the radial load; and developing a new dynamic roll radius value as a function the radial load and the radial stiffness value. 2. A method for controlling a biaxial wheel test machine used for simulating loads experienced by a wheel under actual driving conditions, the test machine comprising a circular drum, having vertical and horizontal axes, in which to receive a wheel, which has a central radial plane and which has a bowl, a rim and a tire, to be tested; a drive unit to rotate the drum, the drum internally having at least one circumferentially disposed biaxial curb; the test machine further comprising a vertical force actuator for controllably exerting a vertical force; a horizontal force actuator for controllably exerting a horizontal force; a pivot head; and a camber actuator to position the wheel about the pivot head to control wheel camber, or tilt, angle, the vertical and horizontal forces being applied to the wheel to force the tire against a biaxial curb and the drum to rotate the wheel with the curb and the drum, wherein the method comprises steps: a. adjusting the vertical force, the horizontal force, and the camber angle based on wheel vertical and horizontal forces previously determined during a road test; b. using the position of a point of application on the tire of a resultant force of a component wheel radial force and a component wheel axial force as a control magnitude for adjusting the camber angle; c. measuring the force of the camber actuator and using the measured camber actuator force as a control magnitude for determining the point of the application of the resultant force upon the tire; d. calculating the minimum displacement between the application point of the resultant force and the central radial plane of the wheel by means of the formula Rs = [ M F S + ( Fa × R dyn ) Fr ] - a 1 where: Rs=the minimum displacement between the application point of the resultant force and the central radial plane of the wheel; Mfs=the moment of force around the pivot head; Fa=the wheel axial component of reactive force; Rdyn=the dynamic roll radius of the tire; Fr=the wheel radial component of reactive force; a1=the minimum displacement between the pivot head and the tire center point, and e. reducing inaccuracies in camber angle determinations by calculating more accurate values of Rdyn with axial load and camber angle held constant and measuring the change of radial position in response to unit changes of radial load; (f) calculating radial stiffness by determining the ratio of radial position change in response to unit changes of radial load; and (g) calculating a new Rdyn value by multiplying radial load by the radial stiffness value. 3. The method of claim 2, further comprising steps: (h) with the camber angle held constant at zero degrees, measuring the changes of axial position in response to unit changes of axial load; (i) calculating zero degree axial stiffness by determining the ratio of axial position change in response to unit changes of axial load; (j) with the radial position held constant and the camber angle held at negative fifteen degrees, measuring the change of axial position in response to unit changes in axial load; (k) with the camber angle held constant at negative fifteen degrees, calculating the axial stiffness by determining the ratio of axial position change in response to unit changes of axial load; (l) averaging the values of the ratios that are based on both camber angles; and (m) multiplying the axial load by the average slope value and adding the new value to the original value of RS, thereby further reducing inaccuracies in the minimum displacement between the application point of the resultant force and the central radial plane of the wheel by calculating more accurate values of RS. 4. The method of claim 3, further comprising steps: (n) subtracting the mathematical and the strain-gauged, wheel-based solutions from the camber angle calculated for each load pair, Fa and Fr, to determine empirical correction factors; (o) grouping the correction factors into families based on vehicle class and tire sidewall height; and (p) averaging the correction factors within each family to provide a generic test machine correction factor, thereby offsetting any remaining inaccuracies. 5. A method for controlling a biaxial wheel test machine used for simulating loads experienced by a wheel under actual driving conditions, the test machine comprising a circular drum, having vertical and horizontal axes, in which to receive a wheel, which has a central radial plane and which has a bowl, a rim and a tire, to be tested; a drive unit to rotate the drum, the drum internally having at least one circumferentially disposed biaxial curb; the test machine further comprising a vertical force actuator for controllably exerting a vertical force; a horizontal force actuator for controllably exerting a horizontal force; a pivot head; and a camber actuator to position the wheel about the pivot head to control wheel camber, or tilt, angle, the vertical and horizontal forces being applied to the wheel to force the tire against a biaxial curb and the drum to rotate the wheel with the curb and the drum, wherein the method comprises steps: a. adjusting the vertical force, the horizontal force, and the camber angle based on wheel vertical and horizontal forces previously determined during a road test; b. using the position of a point of application on the tire of a resultant force of a component wheel radial force and a component wheel axial force as a control magnitude for adjusting the camber angle; c. measuring the force of the camber actuator and using the measured camber actuator force as a control magnitude for determining the point of the application of the resultant force upon the tire; d. adjusting the vertical force, the horizontal force and the camber angle until an unambiguous solution for the following formulas is reached: Rs = [ M F S + ( Fa × R dyn ) Fr ] - a 1 Fv = - Fr - cos ( γ ) + Fa × sin ( γ ) and Fh = - Fr × sin ( γ ) - Fa × cos ( γ ) where: Rs=the minimum displacement between the application point of the resultant force and the central radial plane of the wheel; Fv=the vertical force; Fh=the horizontal force; MFs=the moment of force around the pivot head; Fa=the wheel axial component of reactive force; Rdyn=the dynamic roll radius of the tire; Fr=the wheel radial component of reactive force; a1=the minimum displacement between the pivot head and the tire center point, and γ=Tilt Angle×(π/180°) e. reducing inaccuracies in camber angle determinations by calculating more accurate values of Rdyn with axial load and camber angle held constant; measuring the change of radial position in response to unit changes of radial load; (f) calculating radial stiffness by determining the ratio of radial position change in response to unit changes of radial load; and (g) calculating a new Rdyn value by multiplying radial load by the radial stiffness value. 6. The method of claim 5, further comprising steps: (h) with the camber angle held constant at zero degrees, measuring the changes of axial position in response to unit changes of axial load; (i) calculating zero degree axial stiffness by determining the ratio of axial position change in response to unit changes of axial load; (j) with the radial position held constant and the camber angle held at negative fifteen degrees, measuring the change of axial position in response to unit changes in axial load; (k) with the camber angle held constant at negative fifteen degrees, calculating the axial stiffness by determining the ratio of axial position change in response to unit changes of axial load; (l) averaging the values of the ratios that are based on both camber angles; and (m) multiplying the axial load by the average slope value and adding the new value to the original value of RS, thereby further reducing inaccuracies in the minimum displacement between the application point of the resultant force and the central radial plane of the wheel by calculating more accurate values of RS. 7. The method of claim 6, further comprising steps: (n) subtracting the mathematical and the strain-gauged, wheel-based solutions from the camber angle calculated for each load pair, Fa and Fr, to determine empirical correction factors; (o) grouping the correction factors into families based on vehicle class and tire sidewall height; and (p) averaging the correction factors within each family to provide a generic test machine correction factor, thereby offsetting any remaining inaccuracies.
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