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1

Optimisation of the Joint Geometry of a Rocker Pin Chain

Neumann L., Ulbrich H., Pfeiffer F.

Machine Dynamics Problems

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2005

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Vol. 29, No. 4

97-108

EN

Continuous variable chain drives have to satisfy high requirements to compete with common gears and therefore an improvement of certain properties of the CVT (Continuously Variable Transmission) is desired. In this contribution the important goal to reduce the noise emission of the gear is realised by optimising the geometry of the rocker pin chain. Applying numerical simulation techniques and an optimisation algorithm carries out this optimisation. For this purpose a detailed dynamical model of the CVT is introduced which includes an exact treatment of the rocker pin kinematics of the chain. The geometry of the rocker pin joints, which shall be optimised, is defined by the optimisation parameters. A good choice for a measure of the noise emission is the amplitudes of the forces in the bearings in a certain frequency domain. They are used to form the target function. A numerical simulation provides a connection between the optimisation parameters and the objective function, which is not given analytically and takes high simulation effort. Therefore the optimisation algorithm implicit filtering is applied to solve the optimisation problem. The presented approach is applied to minimise the gear vibrations of a CVT by finding optimal geometry parameters. A significant reduction of the noise emission is gained.

2

Reflectance models by pumping up the albedo function

Neumann L., Neumann A., Szirmay-Kalos L.

Machine Graphics and Vision

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1999

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Vol. 8, No. 1

3-17

EN

The paper introduces a method, called the albedo pumping-up, to derive new, physically plausible BRDFs from an axisting one or from any symmetric function. This operation can be applied recursively arbitrary number of times. An important application of this operation is the transformation of the Phong and Blinn models in order to make them produce metallic effects. The paper also examines the albedo function of reflectance models and comes to the conclusion that widely used models violate energy balance at grazing angles.

3

The constant radiance term

Neumann L., Neumann A., Prikryl J., Purgathofer W.

Machine Graphics and Vision

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1998

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Vol. 7, No. 3

535-549

EN

This paper describes a fundamential improvement for all rendering methods that evaluate the rendering equation in any complexity. The "constant Radiance Term" accelerates the computation of multiple interreflections in arbitrary non-diffuse environments. It is an extension of the constant radiosity step untroduced ealiner for solving radiosity problems and does not require geometrical nor visibility information. A constant radiance portion is extracted from the solution in every surface point and every direction. The residuum problem can be solved faster or with reduced variance by all known methods that consider non-diffuse light interreflections, like different versions of distribution ray tracing, deterministic and stochastic radiosity methods, and hybrid solutions. The constant radiance value is chosen in such a way that the total self-emitted power of the residuum problem is zero so that after the extraction of the constant part there are places with positive self-emittance and places with positive self-emittance and places with negative self emittance. The achieved acceleration can be significant for environments with many bright coloured surfaces. Using a decomposition into separate positive and negative problems it is possible to apply the technique even when using turnkey rendering software.