1. Field of the Invention
The invention relates to sled buck testing systems.
2. Background Discussion
A vehicle experiencing an impact barrier test, where the barrier is at an angle relative to the direction of motion, e.g., longitudinal motion, of the vehicle, may experience longitudinal deceleration, lateral movement, and yaw movement.
Some sled buck testing systems used to simulate vehicle impact barrier tests may only permit longitudinal movement.
A sled buck testing system is desired that permits lateral movement and yaw movement.
Embodiments of the invention may take the form of a system for sled buck testing. The system includes a sled carriage configured to move in a direction of an axis, a guide attached with the sled carriage, and a pivot member configured to move along the guide. The system also includes first and second tracks attached with the sled carriage, a circular bearing member having a center of rotation attached with the first and second tracks, and a platform attached with the circular bearing member. The system further includes a sled buck attached with the platform. Upon acceleration of the sled carriage, the sled buck and platform move relative to the sled carriage in a predetermined fashion.
Embodiments of the invention may take the form of a system for sled buck testing. The system includes a sled carriage configured to move in a direction of an axis and a track attached with the sled carriage. The system also includes a platform attached with the track and a sled buck attached with the platform. Upon acceleration of the sled carriage, the sled buck and platform move relative to the sled carriage in a predetermined fashion.
a and 1b show the movement of a vehicle before and after an impact barrier test.
a shows an exploded perspective view of a track and guide rail sled back testing system in accordance with an embodiment of the invention.
b shows an assembled perspective view of the track and guide rail sled buck testing system of
a through 8e show models of the movement and the forces acting on the track and guide rail sled buck testing system of
a shows an exploded perspective view of a track sled buck testing system in accordance with an embodiment of the invention.
b shows an assembled perspective view of the track sled buck testing system of
a through 10d show models of the movement and the forces acting on the track sled buck testing system of
a shows vehicle 10 experiencing longitudinal acceleration, ax, in an X-Y plane prior to a 30 degree impact.
The equation of angular motion is given by
Fnh1−Fth2=I{umlaut over (θ)}. (5)
Substituting (2) and (4) into (5) yields
Rearranging (6) yields
or
Thus, r is a vehicle 10 dependent constant.
Applying a double integration to (8) yields
Equilibrium in the Y direction is given by
Fy=Fn sin 30°−Ft cos 30°. (10)
Substituting (2) and (4) into (10) yields
Because
Fy=may, (12)
Applying a double integration to both sides of (13) yields
Dy=∫∫aydtdt=C∫∫axdtdt (14)
where
Thus,
and
Dy=C∫∫axdtdt. (17)
(16) and (17) describe the motion of vehicle 10 in the X-Y plane, e.g., longitudinal deceleration, lateral motion, and yaw, in terms of one independent degree of freedom, e.g., ax.
At the C.G., the lateral velocity and angular velocity can be obtained by
Vy=C∫axdt (18)
and
At the instantaneous center of rotation, o,
Vy=s{dot over (θ)}. (20)
Thus,
s=rC. (21)
Substituting C and r into (21) leads to
The validity of (16) and (17), as well as the values for r and C, can be determined experimentally by, for example, analyzing barrier vehicle response or structural CAE data.
a shows an exploded view of a portion of track and guide rail sled buck testing system 11. System 11 includes platform 14, sled carriage 16, and base plate 18. Tracks 20 are mounted to track mounting structure 22. Track mounting structure 22 is attached with base plate 18 via mounting holes 24. Mounting holes 24 are configured such that track mounting structure 22 and thus tracks 20 are adjustable relative to base plate 18 through a range of angles as will be described in detail below. Tracks 20 include track sliders 26 that move along tracks 20. Circular bearing plate 28, having a center of rotation 29, is attached to track sliders 26 via bearing plate mounting holes 30 and track slider mounting holes 32.
Guide rail 34 is attached to base plate 18 via guide rail mounting holes 36. Guide rail mounting holes 36 are configured such that guide rail 34 is adjustable relative to base plate 18 through a range of angles as will be explained in detail below. Guide rail 34 includes guide rail slider 38, which moves along guide rail 34, and pivot 40. Pivot 40 is connected with platform 14 at pivot mount 42. Pivot mount 42 allows platform 14 to pivot about pivot 40.
Guide rail 34 need not be straight. Guide rail 34 may be curved or bent, e.g., tuned, such that movement of platform 14 about pivot 40 simulates a desired vehicle behavior.
Base plate 18 is connected with carriage 16, e.g., bolted, via carriage mounting holes 44. Platform 14 is mechanically connected with circular bearing 31. Circular bearing 31 is mechanically connected with circular bearing plate 28.
b shows an assembled view of system 11. Buck mounting structure 46 may be used to facilitate the connection of buck 12 with platform 14 as shown. Buck 12 and platform 14 have a center of gravity, C.G. A is assembled, center of gravity C.G. is aligned with center of rotation 29.
a through 8e show models of the movement and the forces acting on system 11 where
Referring to
mpac cos α=mpat. (23)
Decomposing at into two components yields
axp=at cos α=ac cos2 α (24)
and
ayp=at sin α=ac sin α cos α (25)
Referring to
ax=ac−axp=ac sin2α (26)
and
ay=ac sin α cos α (27)
Solving (26) and (27) for ac, ax, and ay yields
Because
ay=Cax, (30)
Referring to
Vo cos γ−VA cos η=0 (32)
where
Vo=d1{dot over (θ)} (33)
and
VA=d2{dot over (θ)}. (34)
Rotation of the line OA yields
Vo sin γ−VA sin η=h{dot over (θ)}. (35)
Also,
and
γ=α−β+η. (37)
(32)-(37) yield
β=α−γ+Δ (38)
where
If γ=α (by selecting location A),
In summary,
Example values for the above variables are
Upon acceleration of carriage 16 by acceleration pulse, ap, sled buck 12 and platform 14 will move relative to carriage 16. In particular, sled buck 12 and platform 14 will translate relative to carriage 16 as governed by (17) and sled buck 12 and platform 14 will rotate about center of rotation 29 and pivot 40 as governed by (16).
a shows an exploded view of track sled buck testing system 13. System 13 includes platform 14, sled carriage 16, and base plate 18. Tracks 20 are mounted to track mounting structure 22. Track mounting structure 22 is attached with base plate 18 via mounting holes 24. Mounting holes 24 are configured such that track mounting structure 22, and thus tracks 20, are adjustable relative to base plate 18 through a range of angles as will be described in detail below. Tracks 20 include track sliders 26 that move along tracks 20. Circular bearing plate 28, having a center of rotation 29, is attached to track sliders 26 via bearing plate mounting holes 30 and track slider mounting holes 32.
Base plate 18 is connected with carriage 16, e.g., bolted, via carriage mounting holes 44. Platform 14 is mechanically connected with circular bearing 31. Circular bearing 31 is mechanically connected with circular bearing plate 28.
b shows an assembled view of system 13. Buck mounting structure 46 may be used to facilitate the connection of buck 12 with platform 14 as shown. Buck 12 and platform 14 have a center of gravity, C.G. As assembled, the center of gravity, C.G., is not aligned with center of rotation 29 as will be explained in detail below.
a through 10d show models of the movement of and the forces acting on system 13, where:
Referring to
mpac cos α≈=mpat (43)
Decomposing at into two components yields
axp=at cos α=ac cos2 α (44)
and
ayp=at sin α=ac sin α cos α. (45)
Referring to
axo=ac−axp=ac sin2 α. (46)
The equation of motion about the center of rotation 29 is given by
msace sin2 α=(msR2+mse2){umlaut over (θ)}. (47)
The longitudinal acceleration at the C.G. is given by
ax=axo−e{umlaut over (θ)}=ac sin2 α−e{umlaut over (θ)}. (48)
Solving (47) and (48) for ac and ax yields
From above
ax=r{umlaut over (θ)}. (51)
Thus,
Also,
ay=ayo=ayp=ac sin α cos α. (53)
Because
ay=Cax, (54)
thus,
Rearranging (55) yields
Referring to
Example values for the above variables are
Upon acceleration of carriage 16 by acceleration pulse, ap, sled buck 12 and platform 14 will move relative to carriage 16. In particular, sled buck 12 and platform 14 will translate relative to carriage 16 as governed by (17) and sled buck 12 and platform 14 will rotate about center of rotation 29 as governed by (16).
While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.
This application claims the benefit of U.S. provisional application Ser. No. 60/821,859 filed Aug. 9, 2006, and U.S. provisional application 60/821,862 filed Aug. 9, 2006. This application is related to an application filed concurrently also entitled “Sled Buck Testing System,” application Ser. No. 11/565,855, the contents of which are incorporated in their entirety by reference herein.
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Number | Date | Country | |
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60821859 | Aug 2006 | US | |
60821862 | Aug 2006 | US |