The consideration of potential energy stored in a system is paramount to carry on safe maintenance operations of mechanical system. In particular, this paper concentrates on the elastic energy accumulation occurring in a belt conveyor system ensuing a seizure of one of the pulleys owing to, for example, dirt and spilled bulk material accumulation in the belt inlet zone. The hazard of considering the system completely discharged just because the electrical supply cut off and the effect of such an energy storage are investigated by means of a lumped mass dynamic mathematical model. It allows time variable operating conditions to be considered, as well as starting and stopping phases transients. Standard maintenance operations are simulated, and the effect of stored energy sudden release investigated.

Ball screws have been investigated by several researchers from a theoretical point of view because the intrinsic complexity of experimental investigation of these mechanisms. Most of the models developed so far have been developed in quasi-static conditions ignoring inertia terms and time variability of operating conditions. A detailed multibody dynamic model of a double nut preloaded ball screw is presented in this paper, taking into account the full dynamic of each subcomponent as well as the mutual interactions. A 3D contact model is introduced, considering Hertzian normal contact and a simplified friction model based on grease lubrication. This model takes into account the time variability of the operating conditions and it is suitable to be used for prognostic and model-based design approaches. The results of dynamic simulations in presence of backlash are presented to highlight the model’s capabilities.

The Simscape Multibody software is a set of libraries and mechanical modeling and simulation tools for use with Simulink ® . For what concerns the contact library, currently it contains only the models to describe impacts between simple geometries, such as spheres, cylinders and planes. When this environment is intended to be used to simulate the 3D dynamics of a system with a complex geometry, such as a ball screw, the built-in blocks are not sufficient. This paper presents a new contact library, containing blocks specifically designed to handle the contacts between a sphere and the two gothic arc helical grooves of a ball screw, as well as the interaction between adjacent spheres. The developed blocks are exploited to create a first case study dynamic model of a single nut not preloaded ball screw in presence of internal backlash. The results highlight the superiority of this multibody approach with respect to the quasi-static or lumped parameters models in terms of extracted information and understanding of the internal mechanics.

Over the past years, a trend toward “more electric” equipment has arisen including flight control systems, leading to a tendency to replace the electro-hydraulic actuators (EHSAs) with electro-mechanical actuators (EMAs), which have however a too high jamming probability for a primary flight control system. An innovative jam tolerant approach is to make the EMA “jam-predictive” by monitoring its health state using effective prognostic algorithms. The need for a high-fidelity model is then paramount. In this study, basing on a typical architecture of an EMA, a detailed analysis of the developed dynamic non-linear ball screw model is presented. The backlash, friction parameters, a model of the rolling/sliding behaviour of a ball with rolling friction are taken into account, contact stiffness and preload are introduced. A discussion is presented on the results of a sensitivity analysis on the efficiency of the mechanism with respect to the above mentioned characteristic parameters under different operating conditions. The model and the results of the sensitivity analysis can be used to better understand the physics within the actuator and the ensuing fault-to-failure mechanisms which are needed for developing more efficient prognostic algorithms.

In this work, entropy generation analysis is used in the search for the optimal design of a mixer for sanitary water. An innovative design of the device is considered: hot water and cold water enter a manifold from five orifices, which opening is controlled by actuators, depending on the requested mass flow rate and average temperature. The design variables are the position of the various orifices, which are modified in order to minimize the mixing length and response time of the device, as well as the global pressure losses. Analysis is conducted using a thermofluid dynamic model which includes continuity, momentum and energy equations, that are solved using a commercial code. Results are then used to calculate the entropy generation distribution, in order to properly consider the various sources of irreversibilities, some of which are necessary (thermal mixing) and some undesired (pressure losses).

The paper describes a new kind of solar tracker intended to satisfy the precision requirements of high concentration photovoltaic systems. The tracker is designed according to a Delta type parallel kinematic schematics. The paper describes the kinematic schematics, the sensor chain and the control algorithm. Finally results obtained in functional tests are shown.

The paper describes a 2-DOF parallel kinematic machine designed to achieve precise solar tracking. The mechanism has been developed keeping in mind that solar concentration technology requires a precise alignment of photovoltaic modules and sun radiation, with error allowance much lower than those ensured by traditional sun trackers. The paper describes the kinematic structure and discusses its forward and inverse kinematic, providing the tools to design a system that satisfies the requirements for dexterity and workspace.

The paper describes the activities carried out for the modeling and identification of the pipe tensioning system used in the lay of off-shore piping lines. First, the interactions between the components of the tensioning system are discussed. Then, a model of the pipe stiffness based on the catenary formulation is presented. It is valid for S or J-lay, depending on the pipe parameters and on the lay conditions. The tensioner model follows. It is composed by a torque controlled electric servomotor that powers a tracks tensioning system. Finally results obtained in the simulation for different work and disturbance conditions are shown.