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TECHNICAL PAPERS

Improved Vibration Isolating Seat Suspension Designs Based on Position-Dependent Nonlinear Stiffness and Damping Characteristics

[+] Author and Article Information
Yi Wan

Milsco Manufacturing Company, 9009 North 51st Street, Milwaukee, WI 53223-2403

Joseph M. Schimmels

Department of Mechanical and Industrial Engineering, Marquette University, Milwaukee, WI 53201-1881

J. Dyn. Sys., Meas., Control 125(3), 330-338 (Sep 18, 2003) (9 pages) doi:10.1115/1.1592189 History: Received July 26, 2001; Revised January 24, 2003; Online September 18, 2003
Copyright © 2003 by ASME
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References

Pradko, F., Orr, T. R., and Lee, R. A., 1967, “Human Vibration Analysis,” SAE Paper No. 650426.
Kelsey,  J. L., and Hardy,  R. J., 1975, “Driving of Motor Vehicles as a Risk Factor for Acute Herniated Intervertebral Disks,” Am. J. Epidemiol., 102, pp. 63–73.
Rosegger,  R., and Rosegger,  S., 1960, “Health Effects of Tractor Driving,” J. Agric. Eng. Res., 5(3), pp. 241–242.
Fishbien,  W. I., and Salter,  L. C., 1950, “The Relationship between Truck and Tractor Driving and Disorders of the Spine and Supporting Structures,” Ind. Med. Surg., 19, pp. 444–445.
Gouw,  G. J., Rakheja,  S., Sankar,  S., and Afework,  Y., 1990, “Increased Comfort and Safety of Drivers of Off-highway Vehicles Using Optimal Seat Suspension,” SAE Trans., 99, pp. 541–548.
Amirouche,  F. M. L., Xie,  M., and Patwardhan,  A., 1994, “Optimization of the Contact Damping and Stiffness Coefficients to Minimize Human Body Vibration,” J. Biomech. Eng., 116, pp. 413–420.
Amirouche,  F., Palkovics,  L., and Woodrooffe,  J., 1995, “Optimal Driver Seat Suspension Design for Heavy Trucks,” Heavy Vehicle Sys., Int. J. Vehicle Des., 2, pp. 18–45.
Wan,  Y., and Schimmels,  J. M., 1997, “Optimal Seat Suspension Design Based on Minimum ‘Simulated Subjective Response,’ ” J. Biomech. Eng., 119, pp. 409–416.
Wu, X., Rakheja, S., and Boileau, P., 1999, “Dynamic Performance of Suspension Seats under Vehicular Vibration and Shock Excitations,” SAE Paper No. 1999-01-1304.
Wu,  X., and Griffin,  M. J., 1998, “The Influence of End-stop Buffer Characteristics on the Severity of Suspension Seat End-stop Impacts,” J. Sound Vib., 215, pp. 989–996.
ISO 7096, 2000, “Earth-Moving Machinery—Laboratory Evaluation of Operator Seat Vibration,” International Organization for Standardization.
ISO 2631-1, 1997, “Mechanical Vibration and Shock—Evaluation of Human Exposure to Whole-body Vibration—Part 1: General Requirement,” International Organization for Standardization.
ISO 5007, 1990, “Agricultural Wheeled Tractors—Operator’s Seat—Laboratory Measurement of Transmitted Vibration,” International Organization for Standardization.
78/764/EEC, 1997, “Driver’s Seat on Wheeled Agricultural or Forestry Tractors,” European Economic Community.
PrEN 13490, 1999, “Mechanical Vibration—Industrial Trucks—Laboratory Evaluation of Operator Seat Vibration,” British Standard Institution.
Wan, Y., 1998, “An Investigation onto Linear and Nonlinear Optimal Seat Suspension Designs,” Ph.D. dissertation, Marquette University.

Figures

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Linear spring/linkage mechanism and Its force-deflection relation. (a) shows a compliant mechanism consisting of one linkage and two linear springs. The vertical force-deflection relation of the mechanism is determined by the geometric parameters (u0,v0,u1,v1,u2, and v2) and the spring stiffnesses (k1 and k2). (b) illustrates the vertical force-deflection relations of this mechanism (dash line) and the optimal nonlinear spring (solid line).
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Lumped parameter model of the system. The uppermost four degrees-of-freedom (DOF) constitute the linear model of the operator. The lowermost DOF models a nonlinear seat suspension.
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Comparison of linear, cubic and fifth-order force-deflection equations. At the coordinate frame origin which is located at the static equilibrium position, the instantaneous stiffness of curves 3 and 5 is equal to 0, whereas the stiffness of curve 1 is 5000 N/m.
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Nonlinear force-deflection characteristics of the seat spring including weight offset. The coordinate frame origin is located at the spring free-length position and the equilibrium position is offset by the weight of the seat suspension and operator.
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Relation between the stiffness and damping of the optimal linear seat. The circles identify the optimal damping values corresponding to the optimal stiffness values obtained in Ref. 7. The dashed line is a straight line fit of the data.
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PSD curve for ISO 7096 Class EM1. The solid line is the target PSD; the dash lines are the tolerances on the target PSD; and the dotted line is the PSD used as the input in this analysis.
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Acceleration input from cab floor and acceleration outputs from the optimal nonlinear and optimal linear seats. (a) illustrates the acceleration history of the cab-floor that was used as vibration input to our model. (b) illustrates the acceleration history of the seat mass for the optimal nonlinear seat suspension. (c) illustrates the acceleration history of the seat mass for the optimal linear seat suspension for the same acceleration input.
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Transmissibility from cab floor to seat for the optimal nonlinear and optimal linear seats. (a) illustrates the variation of acceleration transmissibility with input frequency for the optimal nonlinear seat suspension. (b) illustrates the acceleration transmissibility of the optimal linear seat suspension.
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Relative displacements for the optimal nonlinear and optimal linear seats. (a) illustrates the relative displacement of the seat with respect to the cab floor input (ys=xs−x0) for the optimal nonlinear seat suspension. (b) illustrates the relative displacement of the optimal linear seat suspension.

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