Compliant mechanisms gain at least part of their mobility from the deflection of flexible member. They are characterised by high precision, as well as no backlash and wear. Several analytical and numerical methods are used in this work to characterise the behaviour of compliant rotational mechanisms, known as cross-spring pivots, aimed at micropositioning applications. When ultra-high precision is required, the limits of applicability of approximated calculation algorithms have to be determined. The results obtained by employing these methods are thus compared with results obtained by using nonlinear finite element calculations tuned with experimental data reported in literature. The finite element model allows also considering the influence of lateral loads and of non-symmetrical pivot configurations where the angle or point of intersection of the leaf springs, or even the initial curvature of the springs, can be varied. The aim of this part of the work is to determine the influence of the cited design parameters on the minimisation of the parasitic shifts of the geometric centre of the pivot as well as on the minimisation of the variability of the rotational stiffness of the pivot so as to ensure its stability. The obtained results allow therefore determining design solutions applicable in ultra-high precision micropositioning applications, e.g. in the field of production or of handling and assembly of MEMS.
There is an evident need for monitoring pollutants and/or other conditions in river flows via wireless sensor networks. In a typical wireless sensor network topography, a series of sensor nodes is to be deployed in the environment, all wirelessly connected to each other and/or their gateways. Each sensor node is composed of active electronic devices that have to be constantly powered. In general, batteries can be used for this purpose, but problems may occur when they have to be replaced. In the case of large networks, when sensor nodes can be placed in hardly accessible locations, energy harvesting can thus be a viable powering solution. The possibility to use three different small-scale river flow energy harvesting principles is hence thoroughly studied in this work: a miniaturized underwater turbine, a so-called ‘piezoelectric eel’ and a hybrid turbine solution coupled with a rigid piezoelectric beam. The first two concepts are then validated experimentally in laboratory as well as in real river conditions. The concept of the miniaturised hydro-generator is finally embedded into the actual wireless sensor node system and its functionality is confirmed.