Measuring and testing – Orthopedic pressure distribution
Reexamination Certificate
1999-03-01
2001-04-24
Williams, Hezron (Department: 2856)
Measuring and testing
Orthopedic pressure distribution
C073S866400
Reexamination Certificate
active
06220089
ABSTRACT:
TECHNICAL FIELD
This invention relates to vibration dummy apparatus and, in particular, to vibration dummy apparatus which are capable of simulating human vibration response.
BACKGROUND ART
Human vibration comfort has attracted more attention in recent development effort by OEM's and suppliers. This is due to the new phase of NVH improvement and competition in vehicle design. Improving human ride comfort has always been an issue for vehicle component designers and manufacturers. For seating and interior integrators, a great deal of effort has been focused on improving the ride comfort.
Vibration transmissibility has been used as an indicator to measure the comfort of ride by researchers for many years. The ratio of acceleration of the seat cushion or seat back to that of the floorpan is used to measure the transmission of vibration from vehicle to the human occupant. A difficulty arises when a large number of human occupants are needed for a valid test or a component quality evaluation. Component suppliers usually cannot afford such expensive tests during prototype development stage. The number of tests involved to improve the quality of seating systems requires a quicker and more repeatable way to measure the seat vibration performance.
A rigid mass dummy has been used to set a “benchmark” for the seat vibration performance measurement. The rigid mass dummy, however, cannot provide a similar transmissibility measurement to that of a human so its application is largely limited.
In Gu, Y., “A Comparison Test Of Transmissibility Response From Human Occupant And Anthropodynamic Dummy”, SAE paper 980655 dated Feb. 23-26, 1998, a spring-mass dummy is described which was designed to match the human response in low frequency in a vertical direction. A six-axis hydraulic shaker table was employed as the excitation source to the occupied seat. Two seat samples, both measured with human occupants before, were used. For simplicity and comparison, a sweep sine signal in the vertical direction was used as the excitation signal. The transmissibility results measured for the dummy-loaded seat were compared to those of human occupants. The vibration response from a dummy-occupied seat was correlated to that from a human-occupied seat. A consistent relation was shown between the two measurements. However, there are problems of accuracy and stability of transmissibility measurement when utilizing such a spring-mass dummy.
U.S. Pat. No. 3,501,777 discloses a urethane foam disposed over a simulated skeleton.
U.S. Pat. No. 5,376,127 discloses polyethylene sheet material surrounding a endoskeleton.
U.S. Pat. No. 5,166,381 discloses a lower leg cast of thermoplastic material.
U.S. Pat. No. 5,526,707 discloses a simulated pregnant crash test dummy.
U.S. Pat. No. 5,336,270 discloses a plastic material formed over inner components.
U.S. Pat. No. 5,703,303 discloses a simulated torso for testing seats, with the torso being mounted on a boom.
U.S. Pat. No. 5,465,605 discloses a carpet wear testing machine that rolls a simulated heel over the carpet.
U.S. Pat. No. 3,592,041 discloses chair/seat testing by hydraulically controlled back and seat simulators.
U.S. Pat. No. 5,379,646 discloses a test dummy with “back-specific” pressure units for testing vehicle seat backs.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a vibration dummy apparatus which closely matches human vibration response when random excitation signals are applied to a vehicle/seat occupied by the apparatus, thereby providing an improved tool in seat prototype development.
In carrying out the above object and other objects of the present invention, a vibration dummy apparatus is provided. The vibration dummy apparatus is adapted to sit on and be supported by a vehicle seat to accurately simulate human vibration response at an interface between the apparatus and seat cushions of the vehicle seat. The apparatus includes a relatively hard and stiff skeletal frame structure. The skeletal frame structure, in turn, includes a pelvic girdle, a pair of femurs, and a pair of ball-and-socket joints for connecting their respective femurs to the pelvic girdle. The apparatus also includes elastomeric plastic formed over the skeletal frame structure. The elastomeric plastic has a substantially anatomically-correct, surface geometry. The elastomeric plastic formed over the pelvic girdle and the pair of femurs has mechanical properties including human-like, soft tissue spring and damping characteristics. The apparatus further includes a mass-spring system connected to the pelvic girdle for at least partially simulating vibration response of an upper section of a human.
Preferably, the pelvic girdle and femurs are substantially geometrically correct.
The mass-spring system includes a mass weight which is adjustable and a spring having an adjustable spring rate.
The pelvic girdle includes a pair of coxae wherein the first pair of ball-and-socket joints connect their respective femurs to their respective coxae.
The plastic formed over the pelvic girdle and the pair of femurs has an effective stiffness in a range of 6 to 140 kPa.
The elastomeric plastic may be a castable urethane elastomer molded over the skeletal frame structure.
Preferably, the mechanical properties are substantially the same as mechanical properties of bulk muscular tissue in a state of moderate contraction.
The new vibration dummy apparatus utilizes a compressive lower torso and combines it with a metal spring-mass upper torso to reproduce human vibration response at the interface between the dummy apparatus and seat cushions. This combination differs from a pure metal spring-mass system of the prior art in the following areas: (1) it utilizes the spring and damping in both the rubber lower torso and the metal mechanical part to reproduce a human vibration response so it is structurally unique; (2) it produces a system response without damper friction problems so as to greatly improve vibration coherence; (3) it produces a body pressure distribution similar to a human on the seat cushions because of its lower torso structural compliance and greatly improves the posture stability during vibration; and (4) the weight of the moving mass can be adjusted to match different percentiles of humans.
Differences between this new vibration dummy apparatus and other mechanical dummies is that (1) it uses a soft human tissue-like lower torso so it matches compliance better than the previous ones; and (2) it utilizes the spring and damping characteristics of the compliant lower torso. The lower torso is integrated with the spring-mass load simulating the top body of human so that the integrated dummy consists of two parts. This unique design greatly improves the accuracy and stability of transmissibility measurement and provides a direct application tool in seat prototype development.
The above objects and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.
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Yi Gu, “A Comparison Test of Transmissibility Response From Human Occupant and Anthropodynamic Dummy”, SAE International, Feb. 23-26, 1998, No. 980655.
Gu Yi
O'Bannon Terry R.
Williams Christopher A.
Brooks & Kushman P.C.
Lear Corporation
Miller Rose M.
Williams Hezron
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