Synthesis of Four-bar Motion Generation Considering Worst Case Joint Tolerances
Abstract— Four-bar motion generation is used to synthesize a mechanism which passes through or approximate prescribed rigid-body positions. This work will discuss the motion generation of four-bar mechanism with position tolerance variations due to joint running clearance. The tolerance variations study will be based on the standards of American National Standard Institute (ANSI). The new design constraint introduced in this paper will consider the joint tolerances and incorporate it into the displacement position matrix of coupler points described in the conventional planar four-bar motion generation models. The synthesized planar four-bar mechanism will produce tolerance limits for moving pivots and link length from which any mechanism can be synthesized to satisfy the prescribed coupler points with their prescribed tolerances. The included example demonstrates the synthesis of a four-bar mechanism with joint tolerances. 1
The direct linearization method applied to position error in kinematic linkages
This paper demonstrates the direct linearization method (DLM) applied to position error in kinematic linkages due to link-length and angle variations. It combines the mathematical techniques used in assembly tolerance analysis and kinematic error analysis to demonstrate a method that is applicable to models that can be described using vector loops. A bivariate model using DLM is introduced and compared to other deterministic and probabilistic methods using a multiple-loop mechanism as an example. The bivariate model is shown to be an efficient and accurate means of estimating the position error in kinematic linkages.
Impacts of climate and land use changes on flood risk management for the Schijn River, Belgium
Abstract Flooding is the most common natural disaster in Europe. Modern flood risk management relies not only infrastructure development but also on governmental and non-governmental actors applying legal, economic and communicative water management instruments. Within the European Union (EU), flood management closely relies on policy set at the EU and national levels. It is now recognized that a sound understanding of climate change is required in addition to current management by taking into account land use change and socio-political context, as climate and land use changes have major impacts on hydrological responses. This paper investigates the hydrological behavior due to urbanization under current and future climate scenarios of high summer and high winter rainfall for 20 sub-catchments of the Schijn River, located in the Flanders region near Antwerp, Belgium. As urbanization increases and existing rainfall-runoff models neglecting the specific behavior of urban runoff, a hydrological model was developed based on a basic reservoir concept and applied to the existing rainfall-runoff model (PDM) flow to examine the specific urban contribution. Results revealed that peak flow for urban runoff and the total peak flow (i.e. rural and urban runoff) were significantly higher (i.e. ranges from 200% to 500%) than the existing rainfall-runoff model (PDM) flows, because of faster and more peaked urban runoff response. The impact of climate change on current and future conditions was also assessed by estimating peak flows with respect to return periods from the flood frequency curve. The predicted peak flow of high summer future climate scenario was significantly higher (i.e. ranges from 200% to 250%) than that of the current climatic condition for this region. Furthermore, hourly peak flow and daily volume ratios of 100-year return period for the highest, lowest and average impervious area were projected for the time horizon of the year 2100. It is concluded that climate change impacts contribute the most in producing peak flow in coming years, while increased urbanization takes the second place for both hourly and daily values. Results on urbanization effect and climate change impact assessment are useful to the water managers for spatial planning, emergency planning and insurance industry.