A two-degree-of-freedom ambulance stretcher suspension,Part 2: Simulation of system performance with capillary and orifice pneumatic damping

Abstract

Part 1 of this paper gave an overview of the design and dynamics of a two-degree-of-freedom pneumatic stretcher suspension. Part 2 reviews pneumatic damping methods and then investigates system isolation performance using capillary and orifice damping restrictions. These restrictors are compared by numerical simulation of the suspension response when subjected to vertical transient inputs from the ambulance floor. Very good isolation of the stretcher patient is shown to be possible when a suitable damping restriction is used. Brief observations are also made regarding expected suspension performance in pitch and the potential improvement from introducing semi-active pneumatic damping. Part 3 will report results of suspension tests on a laboratory shaking table and in an ambulance.

Keywords

pneumatic suspension ambulance stretcher pneumatic damping capillary restriction orifice restriction floor vibration

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References

Raine

J. K.

Henderson

R. J.

A two-degree-of-freedom ambulance stretcher suspension. Part 1: System overview. Proc. Instn Mech. Engrs, Part D, Journal of Automobile Engineering, 1998, 212(D2), 93–102.

Godden

W. G.

Aslam

Scalise

Seismic isolation of an electron microscope. In Seventh World Conference on Earthquake Engineering, Turkey, 1980, Vol. 8, pp. 69–76.

Waller

R. A.

Benham

P. P.

Fatigue machine mounted on air springs. Engineering, March 1963, 8, 338–339.

Anon. Air-tight products for seating systems. Int. J. Appl. Pneum., December 1993, 5, 26.

Cellucci

T. A.

Houghton

Vibration control without sticker shock. Mach. Des., 12 November 1993, 38–42.

Hundal

M. S.

Literature review—pneumatic shock absorbers and isolators. Shock and Vibr. Dig., 1980, 12(9), 17–21.

Hundal

M. S.

Analysis of performance of pneumatic impact absorbers. Trans. ASME, J. Mech. Des., April 1978, 100, 236–241.

Sainsbury

J. H.

Air suspension for road vehicles. Proc. Instn Mech. Engrs, Auto. Div., 1957-8, No. 3, 75–101.

Anon. Airide springs. Auto. Engr, June 1958, 208–221.

10.

Anon. Dunlop air suspension. Auto. Engr, May 1958, 168–174.

11.

Berry

W. S.

The air coil spring—a new factor in Rambler suspension. SAE Trans., 1958, 66, 471–474.

12.

Hansen

K. H.

Bertsch

J. F.

Denzer

R. E.

Chevrolet level air suspension. SAE Trans., 1958, 66, 483–490.

13.

McFarland

F. R.

Peckham

E. G.

Dietrich

The Buick air poise suspension. SAE Trans., 1958, 66, 466–470.

14.

O'Shea

C. F.

The Ford approach to air suspension. SAE Trans., 1958, 66, 475–482.

15.

Perkins

R. W.

Oldsmobile New-Matic ride. SAE Trans., 1958, 66, 491–495.

16.

Polemics

V. D.

Kehoe

L. J.

Jr Cowin

F. H.

Milliken

S. L.

Cadillac's air suspension for the Eldorado Brougham. SAE Trans., 1958, 66, 346–356.

17.

Anon. Air suspension damping. Auto. Engr, May 1958, 167.

18.

Chance

B. K.

Continental Mark VII/Lincoln Continental electronically controlled air suspension (EAS) system. SAE technical paper 840342, 1984.

19.

Anon. Range Rover: Limousine-refinement with all-terrain capability. Automot. Engr, October-November 1992, 17(5), 20–21.

20.

Anon. Land Rover Range Rover. Automot. Engr, December 1992, 51–52.

21.

Schonfeld

Geiger

Hesse

Electronically controlled air suspension (ECAS) for commercial vehicles. SAE technical paper 912671, 1991.

22.

Anon. Trends in CV suspension and vibration diagnostics. Automot. Engr, June-July 1992, 15–16.

23.

Shearer

J. L.

Study of pneumatic processes in the continuous control of motion with compressed air—II. Trans. ASME, February 1956, 78, 243–249.

24.

Cavanaugh

R. D.

Air suspension and servo-controlled isolation systems. In Shock and Vibration Handbook, Vol. 2 (Eds Harris

C. M.

Crede

C. E.

), 1961, Ch. 33, McGraw-Hill, New York).

25.

Gee-Clough

Waller

R. A.

An improved self-damped pneumatic isolator. J. Sound Vibr., 1968, 8(3), 364–376.

26.

Crede

C. E.

Ruzicka

J. E.

Theory of vibration isolation. In Shock and Vibration Handbook, 3rd edition (Ed. Harris

C. M.

), 1988, Ch. 30 (McGraw-Hill, New York).

27.

Soliman

J. I.

Tajer-Ardabili

Self-damped pneumatic isolator for variable frequency excitation. J. Mech. Engng Sci., 1966, 8(3), 284–293.

28.

Esmailzadeh

Optimisation of pneumatic vibration isolation system for vehicle suspension. Trans. ASME, J. Mech. Des., July 1978, 100, 500–506.

29.

Esmailzadeh

Compact self-damped pneumatic isolators for road vehicles. Trans. ASME, J. Mech. Engng Des., April 1980, 102, 270–277.

30.

Bhave

S. Y.

Effect of connecting the front and rear air suspensions of a vehicle on the transmissibility of road undulation inputs. Veh. System Dynamics, 1992, 21, 225–245.

31.

Bachrach

B. I.

Riven

Analysis of a damped pneumatic spring. J. Sound Vibr., 1983, 86(2), 191–197.

32.

Bachrach

B. I.

Riven

Pneumatic damping of vehicle tyres to improve ride quality. SAE Trans., No. 840746, 1984.

33.

Baker

J. K.

Vibration Isolation, 1975, Engineering Design Guides 13 (Oxford University Press for the Design Council).

34.

Hedrick

J. K.

Railway vehicle active suspensions. Veh. System Dynamics, 1981, 10, 267–283.

35.

Koyanagi

The development of the air spring with variable nozzle. Q. Rep. RTRI, August 1990, 31 (3), 122–127.

36.

Koyanagi

A design method for the vibration isolation system of an air spring suspended vehicle. Q. Rep. RTRI, March 1991, 32(1), 2–7.

37.

Chalmers

W. G.

Chalmers series 1200 air/rubber truck tandem. SAE technical paper 852345, 1985.

38.

Gvineriya

K. I.

Dzhokhadze

G. D.

Kiselev

B. A.

Kozlova

I. V.

Fomchenko

V. M.

Calculation of the constructional parameters of a pneumatic damper for suspension units of the type used in automobiles. Vest. Mashinos-troeniya, 1989, 69(3), 16–19.

39.

Vogel

J. M.

Claar

P. W.

Development of a slow-acting active control pneumatic suspension system for heavy vehicle applications. SAE technical paper 912675, 1991.

40.

Sharp

R. S.

Crolla

D. A.

Road vehicle suspension system design—a review. Veh. System Dynamics, 1987, 16, 167–192.

41.

Andersen

B. W.

The Analysis and Design of Pneumatic Systems, 1967 (John Wiley, New York).

42.

Henderson

R. J.

A low frequency pneumatic suspension for an ambulance stretcher. PhD thesis, University of Canterbury, Christchurch, New Zealand, 1997.

43.

Grace

H. P.

Lapple

C. E.

Discharge coefficients for small-diameter orifices and flow nozzles. Trans. ASME, July 1951, 73, 639–647.

44.

Geary

Ambulances, 1984 (Ian Henry Publications).

45.

Sharp

R. S.

Hassan

S. A.

An evaluation of passive automobile suspension systems with variable stiffness and damping parameters. Veh. System Dynamics, 1986, 15, 335–350.

46.

Robson

J. D.

Road surface description and vehicle response. Int. J. Veh. Des., 1979, 1, 25–35.

47.

Karnopp

Crosby

M. J.

Harwood

R. A.

Vibration control using semi-active force generators. Trans. ASME, J. Engng for Industry, May 1974, 619–626.

48.

Stammers

C. W.

The role of a relaxation damper in a semi-active suspension. In IMechE Autotech 1993, Birmingham, 1993, paper C462/32/014 (Mechanical Engineering Publications, London).