Abstract The paper deals with bristled in-pipe machine simulation. Simulation model is developed and experimentally identified properties are added into the model to achieve high coincidence of the model with real machine. Simulation gives the answers to some selected problems.
{"title":"Simulation of Worm-Like Machine","authors":"M. Kelemen, A. Gmiterko, D. Hroncová","doi":"10.2478/scjme-2018-0015","DOIUrl":"https://doi.org/10.2478/scjme-2018-0015","url":null,"abstract":"Abstract The paper deals with bristled in-pipe machine simulation. Simulation model is developed and experimentally identified properties are added into the model to achieve high coincidence of the model with real machine. Simulation gives the answers to some selected problems.","PeriodicalId":35968,"journal":{"name":"Strojnicky Casopis","volume":"68 1","pages":"25 - 34"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2478/scjme-2018-0015","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48532384","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract This paper focuses on the walking improvement of a biped robot. The zero-moment point (ZMP) method is used to stabilise the walking process of robot. The kinematic model of the humanoid robot is based on Denavit- Hartenberg’s (D-H) method, as presented in this paper. This work deals with the stability analysis of a two-legged robot during double and single foot walking. It seems more difficult to analyse the dynamic behaviour of a walking robot due to its mathematical complexity. In this context most humanoid robots are based on the control model. This method needs to design not only a model of the robot itself but also the surrounding environment. In this paper, a kinematic simulation of the robotic system is performed in MATLAB. Driving torque of the left and right ankle is calculated based on the trajectory of joint angle, the same as angular velocity and angular acceleration. During this process an elmo motion controller is used for all joints. The validity of the dynamic model is tested by comparing obtained results with the simulation results.
{"title":"Dynamic Modelling and Analyzing of a Walking of Humanoid Robot","authors":"Bajrami Xhevahir, Shala Ahmet, Hoxha Gezim, Likaj Rame","doi":"10.2478/scjme-2018-0027","DOIUrl":"https://doi.org/10.2478/scjme-2018-0027","url":null,"abstract":"Abstract This paper focuses on the walking improvement of a biped robot. The zero-moment point (ZMP) method is used to stabilise the walking process of robot. The kinematic model of the humanoid robot is based on Denavit- Hartenberg’s (D-H) method, as presented in this paper. This work deals with the stability analysis of a two-legged robot during double and single foot walking. It seems more difficult to analyse the dynamic behaviour of a walking robot due to its mathematical complexity. In this context most humanoid robots are based on the control model. This method needs to design not only a model of the robot itself but also the surrounding environment. In this paper, a kinematic simulation of the robotic system is performed in MATLAB. Driving torque of the left and right ankle is calculated based on the trajectory of joint angle, the same as angular velocity and angular acceleration. During this process an elmo motion controller is used for all joints. The validity of the dynamic model is tested by comparing obtained results with the simulation results.","PeriodicalId":35968,"journal":{"name":"Strojnicky Casopis","volume":"68 1","pages":"59 - 76"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49326336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The paper deals with static balancing of various kinds of mechanisms and manipulation devices using spring balancing mechanisms. In case of parallelogram robots and manipulation mechanisms a spring balancing mechanism exerting a constant force is used. Problems of static balancing of variable payloads are also presented and investigated in the paper. Static balancing is formulated as an optimization problem with the objective function expressing minimization of the forces acting in the driving joints. As design variables geometrical variables and spring stiffnesses and their unloaded lengths are used. Optimization Toolbox for Use with Matlab and GOOD (Generator Of Optimal Designs) are used to solve the static balancing problems. The optimized mechanisms are evaluated by using multibody dynamics programs taking into account friction effects in mechanism joints. The results of static balancing optimization show essential reduction of the gravity load in drive joints and consequently driving forces with important energy savings.
本文研究了利用弹簧平衡机构实现各种机构和操纵装置的静平衡。对于平行四边形机器人和操纵机构，采用施加恒力的弹簧平衡机构。本文还提出并研究了变载荷的静态平衡问题。静态平衡是一个优化问题，其目标函数表示作用在驱动关节上的力的最小化。设计变量采用几何变量和弹簧刚度及其卸载长度。使用Matlab优化工具箱和GOOD (Generator Of Optimal Designs)来解决静平衡问题。利用多体动力学程序对优化后的机构进行了评价，并考虑了机构关节的摩擦效应。静平衡优化的结果表明，在驱动关节的重力载荷和驱动力的显著减少，从而节省了重要的能源。
{"title":"Static Balancing of Robot Mechanisms and Manipulation Devices","authors":"Š. Segľa","doi":"10.2478/scjme-2018-0019","DOIUrl":"https://doi.org/10.2478/scjme-2018-0019","url":null,"abstract":"Abstract The paper deals with static balancing of various kinds of mechanisms and manipulation devices using spring balancing mechanisms. In case of parallelogram robots and manipulation mechanisms a spring balancing mechanism exerting a constant force is used. Problems of static balancing of variable payloads are also presented and investigated in the paper. Static balancing is formulated as an optimization problem with the objective function expressing minimization of the forces acting in the driving joints. As design variables geometrical variables and spring stiffnesses and their unloaded lengths are used. Optimization Toolbox for Use with Matlab and GOOD (Generator Of Optimal Designs) are used to solve the static balancing problems. The optimized mechanisms are evaluated by using multibody dynamics programs taking into account friction effects in mechanism joints. The results of static balancing optimization show essential reduction of the gravity load in drive joints and consequently driving forces with important energy savings.","PeriodicalId":35968,"journal":{"name":"Strojnicky Casopis","volume":"68 1","pages":"77 - 90"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48321913","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The buckling analysis of carbon nanotubes without and with hetero-junctions is described in this paper. The buckling behaviour was investigated by the finite element method and the carbon nanotubes were modelled as space frame structures. The results showed that the critical buckling force depends on the dimensions of carbon nanotubes. The critical buckling forces of hetero-junction carbon nanotubes are in range between critical buckling forces of carbon nanotubes of both used diameters with the same chiralities without hetero-junction.
{"title":"Buckling Analysis of Hetero-Junction Carbon Nanotubes","authors":"J. Bocko, P. Lengvarský, Juraj Šarloši","doi":"10.2478/scjme-2018-0013","DOIUrl":"https://doi.org/10.2478/scjme-2018-0013","url":null,"abstract":"Abstract The buckling analysis of carbon nanotubes without and with hetero-junctions is described in this paper. The buckling behaviour was investigated by the finite element method and the carbon nanotubes were modelled as space frame structures. The results showed that the critical buckling force depends on the dimensions of carbon nanotubes. The critical buckling forces of hetero-junction carbon nanotubes are in range between critical buckling forces of carbon nanotubes of both used diameters with the same chiralities without hetero-junction.","PeriodicalId":35968,"journal":{"name":"Strojnicky Casopis","volume":"68 1","pages":"16 - 9"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44282286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The evaluation of disk brake squeal is nowadays performed using Finite Element Model. In this standard procedure the thermal effects are omitted. The omission is done because of long computing time of fully coupled brake system thermo-structural transient analysis. This paper is presenting an effective uncoupled thermo-structural FEM procedure. This method is applied on a pin-on-disc system and its time effectiveness is compared to standard full coupled transient analysis.
{"title":"Effective Thermo-Structural Analysis for Disc Brake System Simulation","authors":"P. Kraus, J. Úradníček, M. Musil, M. Bachratý","doi":"10.2478/scjme-2018-0022","DOIUrl":"https://doi.org/10.2478/scjme-2018-0022","url":null,"abstract":"Abstract The evaluation of disk brake squeal is nowadays performed using Finite Element Model. In this standard procedure the thermal effects are omitted. The omission is done because of long computing time of fully coupled brake system thermo-structural transient analysis. This paper is presenting an effective uncoupled thermo-structural FEM procedure. This method is applied on a pin-on-disc system and its time effectiveness is compared to standard full coupled transient analysis.","PeriodicalId":35968,"journal":{"name":"Strojnicky Casopis","volume":"68 1","pages":"125 - 130"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2478/scjme-2018-0022","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44220486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract There are the various types of heat exchangers. The selection of the heat exchanger right type is the first basic assumption for its optimal operation. The heat exchanger calculation itself is another prerequisite for its optimal operation. This article deals with the variables which are usually used to describe the stationary operation of any recuperative heat exchanger with two incoming and two outgoing streams. The knowledge of these variables, including the facts resulting from them, is necessary not only from the point of view of the calculation but also from the point of view of the evaluation of the experimental data of any heat exchanger. The variables values needed for the calculation of heat exchangers, so-called key variables, must always fall within the values range determined on the basis of generally valid knowledge about heat exchangers. The article also deals with the determination of the limit values defining the values range of these key variables.
{"title":"Some Facts Resulting from the Key Variables Used in the Description of the Recuperative Heat Exchangers","authors":"Štefan Gužela, František Dzianik","doi":"10.2478/scjme-2018-0038","DOIUrl":"https://doi.org/10.2478/scjme-2018-0038","url":null,"abstract":"Abstract There are the various types of heat exchangers. The selection of the heat exchanger right type is the first basic assumption for its optimal operation. The heat exchanger calculation itself is another prerequisite for its optimal operation. This article deals with the variables which are usually used to describe the stationary operation of any recuperative heat exchanger with two incoming and two outgoing streams. The knowledge of these variables, including the facts resulting from them, is necessary not only from the point of view of the calculation but also from the point of view of the evaluation of the experimental data of any heat exchanger. The variables values needed for the calculation of heat exchangers, so-called key variables, must always fall within the values range determined on the basis of generally valid knowledge about heat exchangers. The article also deals with the determination of the limit values defining the values range of these key variables.","PeriodicalId":35968,"journal":{"name":"Strojnicky Casopis","volume":"68 1","pages":"249 - 260"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45761257","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Comparing Euler-Bernoulli or Tismoshenko beam theory to higher order beam theories, an essential difference can be depicted: the additional degrees of freedom accounting for out-of plane (warping) and in-plane (distortional) phenomena leading to the appearance of respective higher order geometric constants. In this paper, after briefly overviewing literature of the major beam theories taking account warping and distortional deformation, the influence of distortion in the response of beams evaluated by higher order beam theories is examined via a numerical example of buckling drawn from the literature.
{"title":"Influence of in-Plane Deformation in Higher Order Beam Theories","authors":"E. Sapountzakis, A. Argyridi","doi":"10.2478/scjme-2018-0028","DOIUrl":"https://doi.org/10.2478/scjme-2018-0028","url":null,"abstract":"Abstract Comparing Euler-Bernoulli or Tismoshenko beam theory to higher order beam theories, an essential difference can be depicted: the additional degrees of freedom accounting for out-of plane (warping) and in-plane (distortional) phenomena leading to the appearance of respective higher order geometric constants. In this paper, after briefly overviewing literature of the major beam theories taking account warping and distortional deformation, the influence of distortion in the response of beams evaluated by higher order beam theories is examined via a numerical example of buckling drawn from the literature.","PeriodicalId":35968,"journal":{"name":"Strojnicky Casopis","volume":"68 1","pages":"77 - 94"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42464260","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The vehicle dynamics was a very lot developed in the last twenty years. There is a huge gap in the different vehicle models in this field. Researchers need accurate the car following models because of it. There are several mathematical model, which describe the dynamics and the motion of individual vehicles. This models based on a desired velocity, which is kept by the following vehicle and even small gaps will not induce braking reactions. So this behaviour is not realistic.
{"title":"Adaptive Car Following Model","authors":"P. Mika","doi":"10.2478/scjme-2018-0041","DOIUrl":"https://doi.org/10.2478/scjme-2018-0041","url":null,"abstract":"Abstract The vehicle dynamics was a very lot developed in the last twenty years. There is a huge gap in the different vehicle models in this field. Researchers need accurate the car following models because of it. There are several mathematical model, which describe the dynamics and the motion of individual vehicles. This models based on a desired velocity, which is kept by the following vehicle and even small gaps will not induce braking reactions. So this behaviour is not realistic.","PeriodicalId":35968,"journal":{"name":"Strojnicky Casopis","volume":"68 1","pages":"281 - 288"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2478/scjme-2018-0041","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43223612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract In Turbo machines, there are many components which are provided with interference to transmit torque and to maintain contact between them. There are transient scenarios where impeller and shaft lose interference and limits the speed of the impeller. In this paper, a case study on centrifugal compressor has been presented to see the effect of taper pairing of shaft with impeller. When the centrifugal compressor starts then a transient condition is dominant wherein the impeller of the centrifugal compressor gains higher temperature quickly compared to shaft. Since the thermal expansion of the impeller will be much more than the shaft, interference between impeller and shaft is likely to reduce. With reduced interference, the impeller should retain minimum required contact pressure with the shaft and the torque transmitting capability. For conventional fitted impeller, stress built up is a major concern especially at higher speeds. This paper gives a proposal about the importance of tapered interference fit method compared to cylindrical fitted impeller assembly. An effective analysis between the conventional straight fitted impeller and impeller having tapered bore is presented for the same torque transfer capability. The analysis reveals that for the impeller with tapered bore, the stress for impeller reduces and a healthy contact pressure exists.
{"title":"Effect of Tapered Interference Fit between Impeller and Shaft in Turbo Machines","authors":"Nilesh S. Vishwakarma, Avinash Renuke, V. Phalle","doi":"10.2478/scjme-2018-0024","DOIUrl":"https://doi.org/10.2478/scjme-2018-0024","url":null,"abstract":"Abstract In Turbo machines, there are many components which are provided with interference to transmit torque and to maintain contact between them. There are transient scenarios where impeller and shaft lose interference and limits the speed of the impeller. In this paper, a case study on centrifugal compressor has been presented to see the effect of taper pairing of shaft with impeller. When the centrifugal compressor starts then a transient condition is dominant wherein the impeller of the centrifugal compressor gains higher temperature quickly compared to shaft. Since the thermal expansion of the impeller will be much more than the shaft, interference between impeller and shaft is likely to reduce. With reduced interference, the impeller should retain minimum required contact pressure with the shaft and the torque transmitting capability. For conventional fitted impeller, stress built up is a major concern especially at higher speeds. This paper gives a proposal about the importance of tapered interference fit method compared to cylindrical fitted impeller assembly. An effective analysis between the conventional straight fitted impeller and impeller having tapered bore is presented for the same torque transfer capability. The analysis reveals that for the impeller with tapered bore, the stress for impeller reduces and a healthy contact pressure exists.","PeriodicalId":35968,"journal":{"name":"Strojnicky Casopis","volume":" ","pages":"25 - 32"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44068320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Chausov, A. Pylypenko, P. Maruschak, S. Tkachuk, A. Menou
Abstract A new method for evaluating the bone status using the scattering parameter of hardness indexes (Weibull homogeneity coefficient m) is proposed. A comparative analysis of the condition of the bone tissue of birds, depending on age, breed and calcium content, is conducted. It is established that the scattering degree of mechanical properties, in particular, hardness, is a very structure-sensitive parameter.
{"title":"Express Method to Estimate Structural Imperfection and Bone Tissue Status","authors":"M. Chausov, A. Pylypenko, P. Maruschak, S. Tkachuk, A. Menou","doi":"10.2478/scjme-2018-0040","DOIUrl":"https://doi.org/10.2478/scjme-2018-0040","url":null,"abstract":"Abstract A new method for evaluating the bone status using the scattering parameter of hardness indexes (Weibull homogeneity coefficient m) is proposed. A comparative analysis of the condition of the bone tissue of birds, depending on age, breed and calcium content, is conducted. It is established that the scattering degree of mechanical properties, in particular, hardness, is a very structure-sensitive parameter.","PeriodicalId":35968,"journal":{"name":"Strojnicky Casopis","volume":"68 1","pages":"271 - 280"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45589750","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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