Tunable stiffness in fish robotics: mechanisms and advantages

One of the emerging themes of fish-inspired robotics is flexibility. Adding flexibility to the body, joints, or fins of fish-inspired robots can significantly improve thrust and/or efficiency during locomotion. However, the optimal stiffness depends on variables such as swimming speed, so there is no one “best” stiffness that maximizes efficiency in all conditions. Fish are thought to solve this problem by using muscular activity to tune their body and fin stiffness in real-time. Inspired by fish, some recent robots sport polymer actuators, adjustable leaf springs, or artificial tendons that tune stiffness mechanically. Models and water channel tests are providing a theoretical framework for stiffness-tuning strategies that devices can implement. The strategies can be thought of as analogous to car transmissions, which allow users to improve efficiency by tuning gear ratio with driving speed. We provide an overview of the latest discoveries about 1) the propulsive benefits of flexibility, particularly tunable flexibility, and 2) the mechanisms and strategies that fish and fish-inspired robots use to tune stiffness while swimming.

A flexure-based linear guide with torsion reinforcement structures

In this work, a flexure-based (compliant) linear guide with a motion range comparable to its footprint is presented. The design consists of two folded leaf springs on which torsion reinforcement structures are added. Due to these structures, only two folded leaf springs are needed instead of a minimum of five as in pre-existing designs. The new design is compared to such a pre-existing design, after optimizing both on a support stiffness metric. The new design scores over twice as high on the support stiffness metric, while occupying a smaller (−33%) and a less obstructive build volume. Stress, build volume and manufacturing limitations are taken into account. Additionally, a variation on the new design using three torsion reinforced folded leaf springs is presented and optimized. This design occupies a build volume similar to the pre-existing design, but scores four times higher on the support stiffness metric. A prototype of the new design is built and its parasitic eigenfrequencies are measured, validating the theoretical models (Normalized Mean Absolute Error of 4.3%).

Research On Dynamic Stability Of Vibrating Disk Worktable

This paper studies the influence of the material quality in the vibrating plate and the relative height difference of the leaf springs on the stability of the worktable, i n order to obtain the disturbance law; firstly, the control variable method is adopted an d the Ansys workbench software is used to determine the quality of different materials on the worktable under static force. Secondly, the deformation of the beam and the cr ossbeam was compared by a simulation test. The results showed that the heavier the m aterial, the greater the deformation of the upper beam and the smaller the deformation of the crossbeam. Finally, the harmonic response method was used to study the effect of the height difference of the leaf spring on the deformation of the beam and the cro ssbeam of the worktable. The results show that the greater the height difference, the s maller the impact on the stability of the workbench.

Implementation of Product Sales Forecast Using Artificial Neural Network Method

Product sales forecasting is used by companies to estimate or predict future sales levels using sales data in the previous year. The Artificial Neural Network Backpropagation Algorithm can forecast the sales of goods for the next period for each item in the company. The forecasting process begins by determining the variables needed in the network pattern, and then the established network pattern continued in the network training process using the backpropagation algorithm. After carrying out the network training process, the researcher comparisons with several network patterns formed. This research was conducted to discuss the forecasting analysis of PT XYZ products on spiral and leaf springs. Forecasting carried out on Toyota 48210-25290 R3 type leaf springs using the Artificial Neural Network Backpropagation method with a learning rate weight value of 0.1 hidden layers four and an error of 0.01. From the data processing analysis that has been carried out based on the weight parameters selected, the prediction of sales in April.

Stress-Shot-Peened Leaf Springs Material Analysis through Nano- and Micro-Indentations

Heat-treated and shot-peened lightweight steels with demanding requirements for durability are applied in high-performance automotive leaf springs. Due to their heat-treatment they exhibit degraded properties in the surface-near area compared to the core. This area, which may extend until 300 μm from the surface to the core, experiences the highest bending stresses at operation. The microstructure in the surface and sub-surface layers determines the mechanical performance as well as the wear resistance. The present study refers to the material properties of a stress shot-peened 51CrV4 steel at various depths from the surface. The effect of the manufacturing process has been captured both by Vickers micro-hardness measurements and nanoindentation. The latter combined with a Fine Element Method (FEM)-based algorithm enables the determination of variations in the material’s stress–strain curves over the affected layers, which translate to internal stress changes. The nanoindentation technique has been applied here successfully for the first time ever on leaf springs. The combination of microstructural analysis, microhardness and nanoindentation captures the changes of the treated material, offering insights on the material characteristics, and yielding accurate elastoplastic material properties for local, layered-based analysis of the components’ mechanical performance at operational loading scenarios, i.e. in the framework of stress shot-peening simulation models.

ANALISIS PENGARUH TEBAL PLAT TERHADAP KARAKTERISTIK MEKANIK PEGAS DAUN PADA PROTOTIPE MOBIL FISH CAR UNEJ (FCU) MUDSKIP

Fish Car Unej (FCU) Mudskip is a car designed with a rural terrain system, especially for fishing transportation. FCU Mudskip uses leaf spring suspension at the rear to support the weight of the vehicle, that is leaning towards the rear. The load of the vehicle is inclined to the rear due to the car carrying system in the form of fish and water. This conveying system can cause leaf spring failure. Therefore, this study aims to determine the value of stress, strain and cycle on leaf springs. Ansys 18.1 software was used to obtain stress, strain, and leaf spring cycle values with a thickness of 7 mm, 10 mm, and 13 mm. The value of stress on leaf springs with thickness 7 is 124,31 x 106 N/m2; thickness 10 mm is 74,92 x 106 N/m2; thickness 13 mm is 48,08 x 106N/m2; the value of strain on leaf springs with a thickness of 7 mm is 0,00075; a thickness of 10 mm is 0,00045; a thickness of 13 mm is 0,00029; Acceptable cycles of leaf springs are 7 mm thick is 69206 cycles, 10 mm is 77833 cycles, and 13 mm thick is 93054 cycles. Leaf springs with a thickness of 13 mm are the most optimal leaf springs because they can receive the most cycles of 93054 cycles, according to the function of leaf springs as vibration dampers.

Failure Analysis of a Fractured Leaf Spring as the Suspension System Applied on the Dump Truck

A spring is a component which is designed to have relatively low stiffness compared to normal rigid rods, thereby making it possible to accept certain forces that are charged. A leaf spring is an important suspension component for heavy vehicles, as a failure of the leaf spring can cause severe if not fatal accidents. This study aims to investigate the factors that cause leaf spring failure in the form of a 125 PS dump truck vehicle suspension system. The method employed incorporated experimental and finite element analyses. The experimental work included visual observations, observation using a scanning electron microscope (SEM), hardness testing, and microstructure testing. Leaf spring modelling was conducted using Autodesk Inventor 2017 software, and the finite element analysis (FEA) was performed using Siemens ™ FEMAP V12.0.1 application software to calculate the maximum stress and strain that occurred near the crack tip of the leaf spring. The results from the analysis indicated that the cause of the fracture that occurred in leaf spring No. 3 was due to a defect discovered on the surface of the leaf spring. Based on the observations of the fracture surface, it is revealed that the cause of failure was due to the cyclic load experienced by the components during operation which caused crack propagation beginning from micro-cracks until reaching a significant dimension to cause a final fracture. In addition, the overload imposed on the leaf springs also caused maximum stress on the springs to increase, thus accelerating the failure of the leaf springs. Further results also showed that the value of the stress intensity factor, KI = 29.15 MPa.m1/2 was greater than the value of fracture toughness, KIC = 23 MPa.m1/2 of the spring material.

Early Treatment with a Slow Maxillary Ni–Ti Leaf Springs Expander

The aim of this brief report is to analyse the available literature on the clinical outcomes of a particular appliance for slow maxillary expansion that consists of one or more nickel–titanium springs. Materials and methods: The main medical databases (Scopus, Web of Sciences, Pubmed and Google Scholar) were scanned up to January 2020 using “slow maxillary expan*”, “slow palatal expan*”, “leaf expander” and “NiTi Palatal Expander” as keywords. Skeletal changes in the maxilla after expansion with the Leaf Expander (L.E.) or similar appliances were taken into consideration while reviewing relevant manuscripts. The review focuses on the comparison between the L.E. and conventional expanders (i.e., Haas and Hyrax) regarding the increase in both the distance between the palatal cusps of the upper first molars and the distance between the palatal cusps of the upper second deciduous molars, as well as the increment of nasal structures and pain connected to expansion procedures. Results: Bibliographic research retrieved 32 articles that were considered eligible for the present study. The limited number of articles currently available in international medical databases is allegedly partly due to the fact that these expanders are currently produced by only one patent holder company, which affects its diffusion. Conclusion: Despite the reduced number of published articles, due to the recent introduction of the L.E. device, most of the authors have found that the effects of the L.E. device are clinically and radiographically comparable to those achievable with the rapid palatal expander.