Analytical and experimental investigation of a parallel leaf spring guidance |
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Authors: | J P Meijaard D M Brouwer J B Jonker |
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Affiliation: | 1.Laboratory of Mechanical Automation and Mechatronics, Faculty of Engineering Technology,University of Twente,Enschede,The Netherlands;2.Laboratory of Mechanical Automation and Mechatronics, Faculty of Engineering Technology,University of Twente,Enschede,The Netherlands;3.Demcon,Oldenzaal,The Netherlands |
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Abstract: | The consequences for the static and dynamic system behaviour of misalignment in an overconstrained direction are analysed.
Therefore, a relatively simple parallel leaf spring guidance, which is overdetermined only once, serves as a case to gain
insight. A multibody program using flexible beam theory is used to determine the change in vibration mode frequencies and
stiffnesses due to misalignment. A previously developed beam element for modelling the leaf springs is shown to be able to
describe these phenomena with a limited number of elements. Buckling loads and associated buckling modes are also determined
analytically. An instrument has been fabricated to measure the change of vibration mode frequencies due to a rotational misalignment
in the overconstrained direction. Experiments using wire spark eroded leaf springs are in good agreement with the calculations.
Differences between the experimental and calculated results are attributed to the imperfections in the hardware model, in
particular residual stresses, and the assumptions used for the beam element in the numerical model. A small misalignment,
in this case 0.8–5.8 mrad, causes strong change of static and dynamic system behaviour. The decreased stiffnesses perpendicular
to the compliant direction are disturbing, because these are designed to be large to enhance precision manipulation. The negative
effects of overconstrained design are largest if relatively thin and wide leaf springs are used. If the misalignment is kept
below 50% of the angle of which a bifurcation occurs, the overconstrained design of the parallel leaf spring mechanism does
not significantly influence the system natural frequencies and stiffness. |
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