Recent Patents on Mechanical Engineering - Volume 11, Issue 4, 2018

Background: Traditionally, robots perform desired tasks with the aid of end-users analytically decomposing and manually programming. Robots controlled the program can only follow program instructions to move, which bring great difficulty to non-professional users. So it is meaningful to study new robot control paradigm for robots to accomplish tasks actively without the professional program. Vision-based robot learning by demonstration (vision-based LbD) is an effective approach that a robot can autonomously accomplish a task with help of the combination of the learning by demonstration (LbD) and vision sensing technology. Vision-based LbD allows robots to learn skills through ‘seeing’ demonstrations of users with vision sensors. Vision-based LbD reduces the operation difficulty of robots and provides an intuitive manner for human interact with robot, especially for those users who have no professional program experience. Objective: Providing the references for researchers who work in related fields by reviewing recent advances of vision-based LbD. Methods: This paper reviews the latest patents and current representative articles related to visionbased LbD. The key methods of these references are introduced in the aspects of algorithms, innovations and principles. Results: The researches related to vision-based LbD in the last 5 years are classified, the advantages of different algorithms in these patents and articles are introduced and analyzed, the future developments and potential problems in this field are discussed. Conclusion: The main advantage of vision-based LbD is to allow users training robots for new tasks by the demonstration under the vision sensor without programming control. So, vision-based LbD provides an intuitive manner of robot learning by demonstration to solve the problem of human-robot interaction. Further improvement is required in the following aspects: Algorithm innovation, multiple demonstrations, many definitions of human action and so on. More patents on vision-based LbD should be invented.

Background: Malocclusion is one of the three major oral diseases which affect the quality of human life and mental health. The fixed appliance technology is most commonly used to treat malocclusion. Nowadays, the designs of orthodontic appliances mostly rely on doctors' experience. It is significant to study orthodontic forces to improve the effectiveness of orthodontic treatment and alleviate the sufferings of the patients. The orthodontic force measurement is the fundamental of the research on the orthodontic forces. Objective: This paper attempts to present a general summarization of recent studies about orthodontic force measuring devices and introduce their respective characteristics and development including their components and experimental steps. Methods: This paper reviews various representative studies related to the orthodontic force measuring devices. The research topics discussed the components of recent orthodontic force measuring devices, experimental steps, experimental materials, applications and the characteristic of the presented orthodontic force measuring devices. Results: The advantages and disadvantages of different types of the orthodontic force measuring devices are discussed, and the structural characteristics are concluded. In addition, the main problems in its development are analyzed, the solutions to the issues and the current and future research on orthodontic force measuring device are discussed. Conclusion: Orthodontic force measuring device plays an important role in the orthodontic measurement. The orthodontic force measurement result can help orthodontic doctors improve the effectiveness of the orthodontic treatment. And further improvements are needed in the aspects of experimental dentition model built by biomimetic materials, the rebuilt of the real biological environment of human mouth and portability of the orthodontic force measuring devices. More studies on the orthodontic force measuring device should be conducted.

Background: This paper intends to provide the elementary understanding about the development of thermal energy storage systems. Reviews of storage system performance are carried out from various characterization studies, experimental work, numerical investigations and patents. Several techniques employed to enhance the thermal performance have been reviewed and discussed. Composite phase change materials are the best alternative to achieve the cost feasibility in thermal energy storage systems without compromising the storage capacity. Objective: The purpose of this study is to give an outline and history of the thermal energy storage systems and enlighten the techniques used for storage density enhancement without significant modifications in the design. Methods: In this study, three methods such as, characterization studies, experimental work, numerical investigations and patents. It also addresses many research articles and recent patents on the thermal storage systems, various techniques adopted and applications of such systems. Results: Composite phase change materials are the best alternative to achieve the cost feasibility in thermal energy storage systems without compromising the storage capacity. Carbon based nanoparticles show excellent properties in the composite phase change materials. Conclusion: Composite phase change materials have greater potential for thermal energy storage applications and especially carbon-based nanoparticles like graphene, graphene oxide, carbon nanotubes, fullerene, graphite, graphite oxide, extracted graphite etc., are greatly enhancing the thermo-physical properties of composite phase change materials. Combination of paraffin-based phase change materials and carbon-based nanoparticles can be used for the future thermal energy storage applications.

Background: By conventional lubrication technologies, hydrodynamic thrust slider bearings can not be formed by two solid surfaces sliding against one another with divergent surface separations. The paper introduces the first mode of abnormal hydrodynamic thrust slider bearings with divergent surface separations registered in the patents by using the boundary slippage technology. Objective: To introduce the boundary slippage technology for developing a new type of hydrodynamic thrust slider bearings with divergent surface separations. Methods: The lubrication theories are developed for the mentioned bearings based on the boundary slippage effect. The carried loads and friction coefficients of the bearings are calculated. The performances of the bearings are shown. Results: The calculations show that by designing the boundary slippage on the stationary contact surface in the bearing inlet zones, significant load-carrying capacities of the bearings can be generated, but the friction coefficients of the bearings are quite low on the scales 10-3 or 10-4. There are the optimal geometrical shapes of the bearings for the maximum load-carrying capacity. Conclusion: By artificially designing the boundary slippage on the stationary contact surfaces in the bearing inlet zones, the abnormal hydrodynamic thrust slider bearings with divergent surface separations can be developed with significant load-carrying capacities and low friction coefficients. The design of the bearings can be optimized. The mentioned bearings are energy-conserved and can be applied in specific operating conditions.

Background: The heat transfer condition at the interface of two fluids is an important factor that affects the stability characteristics of a half floating zone with temperature driven Marangoni convection. Various relevant papers and patents report that under microgravity conditions the critical temperature difference beyond which the onset of oscillatory behavior occurs gets drastically affected by the volume ratio of the half-floating zone. Hence, the actual mechanism and influence of parameters that affect flow structure for different volume ratios is still an area of research interest. Objective: To investigate the effect of viscous stresses exerted by the counter-directed ambient air flow on flow and thermal characteristics of a liquid bridge of a high Pr fluid with convex interface under microgravity conditions. Methods: In the present study, thermo-capillary convection in half floating zone is simulated using an axisymmetric model. Computations are carried out using commercial software ANSYS Fluent 17.2 with dimensional variables in both liquid and air domains. As thermo-capillary flow is laminar and incompressible in nature, pressure based solver with SIMPLE algorithm has been used in present analysis. Results: The study indicates that ambient air velocity has a significant influence on the variation of local surface velocity, local surface temperature and local Biot number at the convex interface. Flow and thermal fields inside liquid bridges are presented using isolines of stream function and temperature. Conclusion: With the increase in ambient air velocity, the recirculating regions formed around the halffloating- zone are found to shrink in their size affecting the heat transfer conditions at the interface.

Background: Wavy channels are considered to be an effective passive method for heat transfer enhancement and are widely used in different heat exchanger devices. Various relevant papers and patents report significant increase in convective mixing of the fluid in the wavy channel when it is operated in unsteady flow regime. Consequently, a significant amount of research has been devoted to unsteady flow regimes of wavy channels to better understand the physical mechanism behind the enhancement in heat transfer. Objective: To find the role of monitoring point in predicting flow regimes for periodically fully developed flow conditions in a biconvex module of sinusoidal wavy channel. Methods: In the present study, two-dimensional numerical investigations are carried out to identify the flow regimes for periodically fully developed flow in sinusoidal wavy channels. Computations are carried out using commercial software ANSYS Fluent 17.2. Time signal analysis is carried out for four different points in the flow domain to understand the flow regimes indicated by the points. Results: Detailed temporal variation of x-velocity, its power spectral density and phase space trajectories are presented to understand the flow regimes indicated by the four different points. Even though power spectral density shows difference in nature of velocity signals at the four locations considered, for the three different Re values, phase trajectories illustrate near similar flow regimes. Conclusion: Phase space trajectories of four different points indicate that monitoring velocity at any point in the domain is enough to predict the flow regimes in periodically fully developed flow.

Background: Water pump is the core of engine cooling system, the irrational design will make the engine too warm or too cold, both will influence the efficiency of the engine. Therefore, it is significant for an engine to design one good water pump. Various patents have been discussed in this article. Objective: In this study, we designed a good water pump to match its engine cooling system to reduce the cost of R by design and simulation. Methods: According to the actual working characteristics of an automotive centrifugal pump, we built its computational fluid model. At 80°C and different speeds, using freshwater as cooling liquid, Computational Fluid Dynamics (CFD) technique was used to analyze the 3D turbulent flow inside the pump. Following this, the static pressure, speed and the turbulent kinetic energy distribution of the internal flow field of the pump were discussed. The pump head and efficiency were stimulated by using the CFD technique and compared with the results obtained from the experiments. Results: The experimental results showed that the obtained pump head and efficiency were in good agreement and the accuracy of the performance prediction can be guaranteed within 10%. When the speed was constant, in the case of small flow, the measured pump flow and head were different from CFD numerical simulation, while the consistency of efficiency was better. When the pump exceeded the maximum performance point under the constant speed, the flow continued to increase, the head difference in the centrifugal pump between CFD simulation and test became larger, and the measured test efficiency declined continuously from the maximum. Conclusion: The results showed that the complex condition of running water inside the pump can be exactly stimulated by the CFD technique, especially about the pump head and its efficiency, which provided the theoretical foundation for the later structural designs and optimization of the pump conduit.

Background: Over all efficiency of a turbofan engine can be improved by increasing turbine inlet temperature. To withstand the high turbine inlet temperatures advanced cooling techniques and robust materials are required. Air supplied from compressor can be used to purge turbine components and disk cavities from the incoming hot gas. Objective: In the present study, an attempt is made to understand the aerodynamic and thermal effects caused by the purge flow in the presence of stationary upstream wakes. Methods: Reynolds Averaged Navier Stokes Equation coupled with SST turbulence model is used for computational study. Base case experimental data conducted on a 5 blade linear cascade is used for numerical validation. The coolant to mainstream blowing ratio is varied from 0.2 to 1.2 with a step size of 0.2. Results: It is observed that with an increase in the blowing ratio, the mass averaged total pressure losses also increase. Purge flow shifts the passage vortex away from the endwall and causes significant overturning up to a span of 30-40mm, before they exhibit underturning up to midspan. In an effort to reduce the losses, purge ejection angle is reduced to 45° from 90°. Significant loss reduction and improved endwall protection are observed at 45° ejection angle. This ejection angle provides enough acceleration and momentum to the fluid inside the endwall boundary layer. But the upstream secondary wakes and secondary flows enhanced the mixing losses within the blade passage. Conclusion: The turbulent mixing generated by upstream wakes reduced the film cooling effectiveness over the endwall. The numerical results show that film cooling effectiveness can be improved by reducing the purge ejection angle. Various patents have been discussed in this article.