scholarly journals Design of Bionic Buffering and Vibration Reduction Foot for Legged Robots

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Qian Cong ◽  
Xiaojie Shi ◽  
Ju Wang ◽  
Yu Xiong ◽  
Bo Su ◽  
...  

When legged robots walk on rugged roads, they would suffer from strong impact from the ground. The impact would cause the legged robots to vibrate, which would affect their normal operation. Therefore, it is necessary to take measures to absorb impact energy and reduce vibration. As an important part of a goat’s foot, the hoof capsule can effectively buffer the impact from the ground in the goat’s running and jumping. The structure of the hoof capsules and its principle of buffering and vibration reduction were studied. Inspired by the unique shape and internal structure of the hoof capsules, a bionic foot was designed. Experimental results displayed that the bionic foot could effectively use friction to consume impact energy and ensured the stability of legged robot walking. In addition, the bionic foot had a lower natural vibration frequency, which was beneficial to a wide range of vibration reduction. This work brings a new solution to the legged robot to deal with the ground impact, which helps it adapt to a variety of complex terrain.

Author(s):  
Sean C. Anderson ◽  
Andrew M. Edwards ◽  
Madi Yerlanov ◽  
Nicola Mulberry ◽  
Jessica E. Stockdale ◽  
...  

AbstractExtensive physical distancing measures are currently the primary intervention against coronavirus disease 2019 (COVID-19) worldwide. It is therefore urgent to estimate the impact such measures are having. We introduce a Bayesian epidemiological model in which a proportion of individuals are willing and able to participate in distancing measures, with the timing of these measures informed by survey data on attitudes to distancing and COVID-19. We fit our model to reported COVID-19 cases in British Columbia, Canada, using an observation model that accounts for both underestimation and the delay between symptom onset and reporting. We estimate the impact that physical distancing (also known as social distancing) has had on the contact rate and examine the projected impact of relaxing distancing measures. We find that distancing has had a strong impact, consistent with declines in reported cases and in hospitalization and intensive care unit numbers. We estimate that approximately 0.78 (0.66–0.89 90% CI) of contacts have been removed for individuals in British Columbia practising physical distancing and that this fraction is above the threshold of 0.45 at which prevalence is expected to grow. However, relaxing distancing measures beyond this threshold re-starts rapid exponential growth. Because the extent of underestimation is unknown, the data are consistent with a wide range in the prevalence of COVID-19 in the population; changes to testing criteria over time introduce additional uncertainty. Our projections indicate that intermittent distancing measures—if sufficiently strong and robustly followed— could control COVID-19 transmission, but that if distancing measures are relaxed too much, the epidemic curve would grow to high prevalence.


Fibers ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 64
Author(s):  
Roman Fediuk ◽  
Mugahed Amran ◽  
Sergey Klyuev ◽  
Aleksandr Klyuev

The use of fiber in cement materials is a promising and effective replacement for bar reinforcement. A wide range of fiber-reinforced concretes based on composite binders with increased impact strength characteristics have been developed. The synthesized composites included the composite binder made of Portland cement, silica, and carbonate additives. Basalt and steel were used as fibers. The nature of the influence of the composition and manufacturing technology of cement composites on the dynamic hardening coefficient has been established, while the growth of these indicators is achieved by creating a denser interfacial transition zone between the cement paste, aggregate, and fiber as a result of improving the homogeneity of the concrete mixture and controlling the consistency. Workability indicators (slump flow up to 730 mm; spreading time up to a diameter of 50 cm is up to 3 s) allow them to be classified as self-compacting concrete mixtures. An increase in the values of the impact strength coefficient by a factor of 5.5, the dynamic hardening coefficient by almost 70% as a result of interfacial interaction between fibers and binder matrix in the concrete composite, as well as absorption of impact energy by fiber, was revealed. The formula describing the effect of the loading rate on the coefficient of dynamic hardening of fiber-reinforced concrete has been refined. The fracture processes of the obtained materials have been established: after the initiation of primary cracks, the structure of the composite absorbs impact energy for a long time, while in the inelastic range (the onset of cracking and peak loads), a large number of secondary cracks appear.


2018 ◽  
Vol 24 (4) ◽  
pp. 529-543 ◽  
Author(s):  
Jim Townsend ◽  
M. Affan Badar

Purpose Reciprocating compressors offer an efficient method of compressing almost any gas composition in a wide range of pressures and have numerous applications. Condition monitoring of critical rotating machinery is widely accepted by operators of centrifugal compressors. However, condition monitoring of reciprocating machinery has not received the same degree of acceptance. An earlier study (Townsend et al., 2016) was conducted on temperature monitoring. The purpose of this paper is to examine the impact of continuous pressure monitoring on electric-driven compressors. Design/methodology/approach This research analyzes the impact of continuous pressure monitoring on a fleet of 14 compressors transporting CO2 for enhanced oil recovery. The reliability and efficiency data on 14 reciprocating compressors over a three-year period were analyzed for failures detectable by the condition monitoring technology. The engineering economic analysis is presented to determine the impact this technology will have on the productivity of the compressors. Findings The study considers utilizing condition monitoring technology to analyze the pressure of the swept volume of the compressor cylinders. The results of the study indicate that continuous pressure monitoring technology has a strong impact on the productivity of the compressor fleet. The internal rate of return not only exceeds the operators hurdle rate, but the payback period is also dramatic. Pressure monitoring was found to be economically better than temperature monitoring. Originality/value The study reveals the economic benefits of implementing condition monitoring in the form of continuous pressure monitoring on reciprocating compressors.


2014 ◽  
Vol 783-786 ◽  
pp. 1033-1038
Author(s):  
Shigeto Takebayashi ◽  
Kohsaku Ushioda ◽  
Naoki Yoshinaga ◽  
Shigenobu Ogata

The effect of tempering temperature on the impact toughness of 0.3 mass% carbon martensitic steels with prior austenite grain (PAG) size of about 6 μm and 30 μm were investigated. Instrumented Charpy impact test (ICIT) method was used to evaluate the impact toughness. The tempering temperature of 723K gives the largest difference in the Charpy impact energy at room temperature (RT) between the specimens with two different PAG sizes. Investigation of the test temperature dependence of Charpy impact energy in the 723K tempered steels shows a steep transition at around 200 K for the 6 μm PAG specimen, while it shows a continuous slow transition in a wide range of temperature for the 60 μm PAG specimen. ICIT waveform analysis shows that the fracture propagation energy in stead of the fracture initiation energy mainly controls the temperature dependence of the impact energy. The carbide size distribution in these two specimens was investigated by SEM and TEM. The 60 μm PAG specimen shows the distribution of coarser carbides than does the 6 μm PAG specimen, which seems to be the main reason for the observed difference between them in the Charpy impact energy and the other properties of impact fracture.


Author(s):  
Laura Arce-Chaves ◽  
Ramsés Alfaro-Mora

This study seeks to investigate the impact, responses and demands for support, in the face of the crisis caused by Covid 19, by entrepreneurs and organizations in the economic sectors, as well as the strategies considered to have the greatest impact on their business and that could consider necessary. The study took information from a survey that obtained a total of 138 responses, mainly located in the province of San José (50%), more than half (84.7%) include micro and small businesses and a (9, 3%) medium and large companies mostly located in a development stage in which the company achieves a degree of positioning in the market that guarantees its sustainability over time, the rest are located in the beginning and maturity stages mostly, they cover a wide range of sectors of activity. The largest number of participating entrepreneurs was found in the age range of 30 to 40 years (38%). Thus, it is found that the direct and indirect effects of covid 19 in the entrepreneurial sector of various sectors of the Costa Rican economy caused (55.7%) cuts in working hours as a practice in their businesses to face the crisis and a decrease in (67%) in the price of their products or services, experiencing a transformation in the management of business models that until before this date were usual. It is evident that the effects of the pandemic caused by COVID-19 had a strong impact on the Costa Rican productive sector, and the need for support from the businesspersons who have been affected is evident. Furthermore, for a country of 5.5 million inhabitants, the pandemic leaves more than 400 thousand people unemployed (16.4% + 11.1% underemployed), that is, 92 thousand more than before COVID 19. The worst hit groups are those of women and youth, leading them and the other unemployed to migrate to informality. 1,455 micro (1-5 employees), small (6-30 employees) and medium (31-100) closed. These companies have little chance of reopening, having to increase the figures of informality and in many cases, 2% of GDP in smuggling and illicit trade. The Costa Rican government must work to support new ventures that allow the insertion of new businesses in the formal sector, leading innovation, and competitive proposals to face new challenges. Access to soft loans, improvements in social security rates and differentiated fees for taxation should be part of the solutions. In addition, ensure that the minimum contributory rate of social security is modified for the payment for part-time work, so that the same companies hire personnel based on the hours worked and not for a single rate. It should be considered that Costa Rica is already part of the OCDE and that is going through a historic electoral process (26 presidential candidates), to put this problem in the sights of the candidates. The joint work between private sector, government, financial and educational institutions is a must. Costa Rica is walking at the edge of falling into an economic default and helping these initiatives could be a magic recipe for the economy.


Author(s):  
James C. Conwell ◽  
Glen E. Johnson ◽  
S. W. Peterson

Abstract In this article, a brief history of chain drives is presented, and the design and construction of a machine to investigate chain drive force phenomena is discussed. The new test machine allows the measurement of the impact force between a roller and the sprocket during “seating” and it can also be used to measure the forces that exist in the link sides plates during normal operation (including start-up and shut down conditions). Data can be obtained for a wide range of chain loads and speeds. Two companion papers (“Experimental Investigation of the Impact Force that Occurs When a Roller Seats on the Sprocket During Normal Operation of a Roller Chain Drive” and “Experimental Investigation of the Forces in a Link Side Plate During Normal Operation of a Roller Chain Drive”, both presented at this conference) describe experiments that have been completed with this test machine.


Geology ◽  
2021 ◽  
Author(s):  
Alexander R. Beer ◽  
Michael P. Lamb

River incision into bedrock drives landscape evolution and couples surface changes to climate and tectonics in uplands. Mechanistic bedrock erosion modeling has focused on plucking—the hydraulic removal of large loosened rock fragments—and on abrasion—the slower fracturing-driven removal of rock due to impacts of transported sediment—which produces sand- or silt-sized fragments at the mineral grain scale (i.e., wear). An abrasion subregime (macro-abrasion) has been hypothesized to exist under high impact energies typical of cobble or boulder transport in mountain rivers, in which larger bedrock fragments can be generated. We conducted dry impact abrasion experiments across a wide range of impact energies and found that gravel-sized fragments were generated when the impact energy divided by squared impactor diameter exceeded 1 kJ/m2. However, the total abraded volume followed the same kinetic-energy scaling regardless of fragment size, holding over 13 orders of magnitude in impact energy and supporting a general abrasion law. Application to natural bedrock rivers shows that many of them likely can generate large fragments, especially in steep mountain streams and during large floods, transporting boulders in excess of 0.6 m diameter. In this regime, even single impacts can cause changes in riverbed topography that may drive morphodynamic feedbacks.


Author(s):  
James C. Conwell ◽  
Glen E. Johnson ◽  
S. W. Peterson

Abstract The fluctuation in the tension of a chain link during normal operation is very likely the root cause of chain stretch and fatigue in roller chain drives. In this paper we present the results from a recent experimental investigation of this tension variation phenomenon. The experimental procedure is described, and data are presented for a wide range of initial tensions, transmitted loads, and chain speeds. At low speeds, the data give reasonable agreement with previously published theoretical models for quasi-static load distribution. However, at higher speeds (where inertia effects are more significant) the experimental results indicate that quasi-static models do not provide an adequate explanation. The differences are noted and discussed. An empirical equation for “tight side” chain tension is presented in terms of torque transmitted, sprocket pitch radius, mass per unit length of chain, and linear chain speed. This paper is accompanied by companion papers that describe the design and construction of the test machine and the measurement of the impact force as a roller seats on the sprocket.


2020 ◽  
Vol 54 (21) ◽  
pp. 2999-3007
Author(s):  
Hüseyin E Yalkın ◽  
Ramazan Karakuzu ◽  
Tuba Alpyıldız

The aim of the study is to investigate the behavior of laminated composites under low velocity impact both experimentally and numerically. With this aim, the effects of wide range impact energy values between 10 J and 60 J were evaluated experimentally and numerically for the laminate of [±45/(0/90)2]S oriented unidirectional E-glass as reinforcing material and epoxy resin for matrix material. Different impactor velocities were used to maintain the impact energy values and experimental impact tests were generated with drop weight impact testing machine at room temperature. Numerical simulations were performed using LS-DYNA finite element analysis software with a continuum damage mechanics-based material model MAT058. Contact force between impactor and laminate, and transverse deflection at the center of laminate results were obtained as a function of time and used to plot contact force–time curves, contact force–deflection curves and absorbed energy-impact energy curves. Also, delamination area was examined. Finally, numerical results were compared with experimental results and a good correlation between them was observed.


Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 499 ◽  
Author(s):  
Kerong Ren ◽  
Rong Chen ◽  
Yuliang Lin ◽  
Shun Li ◽  
Xianfeng Zhang ◽  
...  

Reactive metals (RMs) are a new class of material that can withstand mechanical loads and chemically react to release large amounts of heat under strong impact loading. They are gradually becoming widely used in defense and military fields, including for high-efficiency warheads and reactive armor. For the numerical simulation method considering the combined mechanical-thermo-chemical process for the impact energy release behavior of the RMs, the Al/Ni-based RMs were investigated in this work by combining experiments, theoretical calculations and a numerical simulation. Three kinds of Al/Ni-based RMs (Al-Ni, Al-Ni-CuO and Al-Ni-MoO3), were prepared using the hot-pressing forming process. Firstly, the compressive behavior and the parameters of the Johnson-Cook constitutive model were obtained using a mechanical testing machine and split Hopkinson pressure bars (SHPB). Secondly, the parameters of the equation of state (EOS) under the medium and low pressure conditions of the Al/Ni-based RMs, which were was seen as porous mixtures with high theoretical material density percentages (TMD%), were calculated based on the cold-energy superposition theory and the Wu-Jing method. Third, the impact energy release behaviors of the three RMs were studied with direct ballistic tests. The shock temperatures at different impact velocities were calculated based on the existing shock-induced chemical reaction thermo-chemical model while considering the chemical reaction efficiency, the relationship between the shock temperature and the extent of the chemical reaction was established, and the parameters of the relevant chemical kinetic equations were fitted. Finally, the user’s subroutines defining the material model were implemented to update the stresses in the solids elements in LS-DYNA. The model was based on the Johnson-Cook constitutive model with consideration of the mechanical-thermo-chemical coupling effect, which was verified by the experimental results. The results show that the constitutive model developed in this work can describe the impact energy release behavior of the Al/Ni-based RMs.


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