Abstract. Amphibious species of frogs are notable candidates to mimic for amphibious robotic design, as their swimming and sprawling locomotion is generated by the united propulsive mechanisms in which the hindlimbs play the dominant role. Although the propulsive system of frogs is not as complex as other amphibians, it is still difficult to employ the propulsive mechanism in robotic design due to the numerous degrees of freedom (DoF). This paper proposes a novel united propulsive mechanism to acquire the amphibious function inspired by the frog's hindlimb. The mechanism is a hybrid design combining a planar six-bar linkage, which is designed based on homotopy continuation and a spatial four-bar linkage. The DoF of the hindlimb-like mechanism are dramatically decreased to 2, with 1 each in the two sub-chains. Forward analysis is conducted to find the pose of the foot when two actuations are input. The improved analysis based on the geometrical features overcomes the multiplicity from the numerical computation. The inverse kinematic analysis is conducted to find the rotation of the input with a given pose of the foot. The aquatic function of the united propulsive mechanism is demonstrated based on the blade element theory, where the rotational speed and the projected area of the foot are fully active. The terrestrial function of the propulsive mechanism is validated with a specific gait.
{"title":"A 2 degrees of freedom united propulsive mechanism for amphibious function inspired by frog's hindlimb","authors":"Yucheng Tang, Xiaolong Yang, Xiaojin Zhu, Shichao Zhou, Wenbin Zha, Yuxin Sun, Yulin Wang","doi":"10.5194/ms-13-437-2022","DOIUrl":"https://doi.org/10.5194/ms-13-437-2022","url":null,"abstract":"Abstract. Amphibious species of frogs are notable candidates to\u0000mimic for amphibious robotic design, as their swimming and sprawling locomotion is generated by the united propulsive mechanisms in which the hindlimbs play the dominant role. Although the propulsive system of frogs is not as complex as other amphibians, it is still difficult to employ the\u0000propulsive mechanism in robotic design due to the numerous degrees of freedom (DoF). This paper proposes a novel united propulsive mechanism to acquire the amphibious function inspired by the frog's hindlimb. The mechanism is a hybrid design combining a planar six-bar linkage, which is designed based on homotopy continuation and a spatial four-bar linkage. The DoF of the hindlimb-like mechanism are dramatically decreased to 2, with 1 each in the two sub-chains. Forward analysis is conducted to find the pose of the foot when two actuations are input. The improved analysis based on the geometrical features overcomes the multiplicity from the\u0000numerical computation. The inverse kinematic analysis is conducted to find the rotation of the input with a given pose of the foot. The aquatic function of the united propulsive mechanism is demonstrated based on the blade element theory, where the rotational speed and the projected area of the foot are fully active. The terrestrial function of the propulsive mechanism is validated with a specific gait.\u0000","PeriodicalId":18413,"journal":{"name":"Mechanical Sciences","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47649244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. The main purpose of the iterative learning control (ILC) method is to reduce the trajectory tracking error caused by an inaccurate model of the robot's dynamics. It estimates the tracking error and applies a learning operator to the output control signals to correct them. Today's ILC researchers are suggesting strategies for increasing the ILC's overall performance and minimizing the number of iterations required. When a payload (or a different end effector) is attached to a robotic manipulator, the dynamics of the robot change. When a new payload is added, even the most accurately approximated model of the dynamics will be altered. This will necessitate changes to the dynamics estimates, which may be avoided if the ILC process is used to control the system. When robotic manipulators are considered, this study analyses how the payload affects the dynamics and proposes ways to improve the ILC process. The study looks at the dynamics of a SCARA-type robot. Its inertia matrix is determined by the payload attached to it. The results show that the ILC method can correct for the estimated inertia matrix inaccuracy caused by the changing payload but at the cost of more iterations. Without any additional data of the payload's properties, the suggested technique may adjust and fine-tune the learning operator. On a preset reference trajectory, the payload adaptation process is empirically tested. When the same payload is mounted, the acquired adaptation improvements are then utilized for another desired trajectory. A computer simulation is also used to validate the suggested method. The suggested method increases the overall performance of ILC for industrial robotic manipulators with a set of similar trajectories but different types of end effectors or payloads.
{"title":"Payload-adaptive iterative learning control for robotic manipulators","authors":"Kaloyan Yovchev, Lyubomira Miteva","doi":"10.5194/ms-13-427-2022","DOIUrl":"https://doi.org/10.5194/ms-13-427-2022","url":null,"abstract":"Abstract. The main purpose of the iterative learning control (ILC) method is to reduce the trajectory tracking error caused by an inaccurate model of the\u0000robot's dynamics. It estimates the tracking error and applies a learning operator to the output control signals to correct them. Today's ILC\u0000researchers are suggesting strategies for increasing the ILC's overall performance and minimizing the number of iterations required. When a payload\u0000(or a different end effector) is attached to a robotic manipulator, the dynamics of the robot change. When a new payload is added, even the most\u0000accurately approximated model of the dynamics will be altered. This will necessitate changes to the dynamics estimates, which may be avoided if the ILC\u0000process is used to control the system. When robotic manipulators are considered, this study analyses how the payload affects the dynamics and\u0000proposes ways to improve the ILC process. The study looks at the dynamics of a SCARA-type robot. Its inertia matrix is determined by the payload\u0000attached to it. The results show that the ILC method can correct for the estimated inertia matrix inaccuracy caused by the changing payload but at\u0000the cost of more iterations. Without any additional data of the payload's properties, the suggested technique may adjust and fine-tune the learning\u0000operator. On a preset reference trajectory, the payload adaptation process is empirically tested. When the same payload is mounted, the acquired\u0000adaptation improvements are then utilized for another desired trajectory. A computer simulation is also used to validate the suggested method. The\u0000suggested method increases the overall performance of ILC for industrial robotic manipulators with a set of similar trajectories but different types\u0000of end effectors or payloads.\u0000","PeriodicalId":18413,"journal":{"name":"Mechanical Sciences","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47536873","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dongsheng Cong, Haowen Jing, Ruijun Zhang, Zhongyue Lu, J. Shang, Zirong Luo
Abstract. Due to the defects of the internal structure and energy supply carrier, conventional deep sea unoccupied marine equipment cannot meet the requirements of low power consumption. In this paper, the whole structure of a multi-body heave wave energy conversion system was designed to capture and convert wave energy. The conversion system consists of a floating body, an underwater absorber and a power takeoff system (PTO). The dynamic model of the energy conversion system and the mathematical model of energy efficiency evaluation were established according to the dynamic analysis. Based on the real service environment in the South China Sea, the energy efficiency characteristics of floating bodies with different shapes were simulated, and the amplitude response operator (RAO), radiation damping, added mass and Froude–Krylov force of floating bodies with different shapes were compared. Then, the optimal energy efficiency parameters of surface floating body were explored. Finally, the correctness of the conclusion was verified by the energy efficiency test. The results show that, under the limitation of low power consumption and space scale, the energy conversion system of an axisymmetric rotary body with the same sea conditions, same material and the largest scale can significantly improve the conversion efficiency, and the spherical rotary body performs the best, which makes the unoccupied marine equipment have a broad prospect for development.
{"title":"Structural design of multi-body heave wave energy conversion system and analysis of energy efficiency of floating body on water surface","authors":"Dongsheng Cong, Haowen Jing, Ruijun Zhang, Zhongyue Lu, J. Shang, Zirong Luo","doi":"10.5194/ms-13-411-2022","DOIUrl":"https://doi.org/10.5194/ms-13-411-2022","url":null,"abstract":"Abstract. Due to the defects of the internal structure and energy supply carrier, conventional deep sea unoccupied marine equipment cannot meet the requirements of low power consumption. In this paper, the whole structure of a multi-body heave wave energy conversion system was designed to capture and convert wave energy. The conversion system consists of a floating body, an underwater absorber and a power takeoff system (PTO). The dynamic\u0000model of the energy conversion system and the mathematical model of energy efficiency evaluation were established according to the dynamic analysis. Based on the real service environment in the South China Sea, the energy efficiency characteristics of floating bodies with different shapes were\u0000simulated, and the amplitude response operator (RAO), radiation damping, added mass and Froude–Krylov force of floating bodies with different shapes were compared. Then, the optimal energy efficiency parameters of surface floating body were explored. Finally, the correctness of the conclusion was verified by the energy efficiency test. The results show that, under the limitation of low power consumption and space scale, the energy conversion system of an axisymmetric rotary body with the same sea conditions, same material and the largest scale can significantly improve the conversion efficiency, and the spherical rotary body performs the best, which makes the\u0000unoccupied marine equipment have a broad prospect for development.\u0000","PeriodicalId":18413,"journal":{"name":"Mechanical Sciences","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44940948","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Transrectal prostate brachytherapy (BT) can effectively treat prostate cancer. During the operation, doctors need to hold the ultrasound probe for repeated adjustments, which makes it difficult to ensure the efficiency, accuracy, and safety of the operation. We designed an 11 DOF (degrees of freedom) active and passive transrectal BT robot, based on the analysis of the transrectal prostate BT process. The posture adjustment module designed, based on the double parallelogram mechanism, realizes the centering function of the ultrasound probe and performs the kinematic analysis. Based on Simscape Multibody, the working posture and centering effect of the ultrasound probe's different feed distances are simulated. A physical prototype of the transrectal BT robot was developed and measured in experiments. The experimental results indicate that the angle rotation error of the joint is controlled to within 1∘. The rotation range of each joint meets the design requirements. The maximum error of the yaw angle's remote center point motion and pitch angle's remote center point motion are 0.5 and 0.4 mm, respectively, which are less than the deformation that can be endured in the anus by 6 mm. The simulation and experimental results and the analysis of measurement errors have verified the effectiveness and stability of the transrectal BT robot.
{"title":"Design of a transrectal ultrasonic guided prostate low dose rate brachytherapy robot","authors":"Xuesong Dai, Yongde Zhang, Jingang Jiang, Bing Li, Sihao Zuo","doi":"10.5194/ms-13-399-2022","DOIUrl":"https://doi.org/10.5194/ms-13-399-2022","url":null,"abstract":"Abstract. Transrectal prostate brachytherapy (BT) can effectively treat prostate cancer. During the operation, doctors need to hold the ultrasound probe for repeated adjustments, which makes it difficult to ensure the efficiency, accuracy, and safety of the operation. We designed an 11 DOF (degrees of freedom) active and passive transrectal BT robot, based on the analysis of the transrectal prostate BT process. The posture adjustment module designed,\u0000based on the double parallelogram mechanism, realizes the centering function of the ultrasound probe and performs the kinematic analysis. Based on Simscape Multibody, the working posture and centering effect of the ultrasound probe's different feed distances are simulated. A physical prototype of the transrectal BT robot was developed and measured in experiments. The experimental results indicate that the angle rotation error of the joint is controlled to within 1∘. The rotation range of each joint meets the design requirements. The maximum error of the yaw angle's remote center point motion and pitch angle's remote center point motion are 0.5 and 0.4 mm, respectively, which are less than the deformation that can be\u0000endured in the anus by 6 mm. The simulation and experimental results and the analysis of measurement errors have verified the effectiveness and stability of the transrectal BT robot.\u0000","PeriodicalId":18413,"journal":{"name":"Mechanical Sciences","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49425088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lei Wang, Liang Sun, Rongjiang Cui, Yadan Xu, Gaohong Yu, C. Wu
Abstract. The similarity recognition of kinematic chains (KCs) is helpful for improving the efficiency of configuration synthesis, which has been paid more and more attention in recent years. The existing recognition methods are divided into the definition method and feature constant method. Among them, the definition method is difficult to adopt in practice because of its long operation time, especially when the number of similar vertices in KCs is large. In this paper, the new concepts of a loop tree (LT) and a loop tree matrix (LTM) have been proposed, which improve the efficiency of similarity recognition. This method is applied on the complete structure of the following: 8-link with 1 DOF (degree of freedom), 9-link with 2 DOF, 10-link with 1 DOF, 12-link with 1 DOF, 13-link with 2 DOF, 14-link with 3 DOF, 15-link with 4 DOF planar single-joint KCs, and contracted graphs with up to six independent loops. All results are verified by the definition method to prove the good applicability, reliability, and efficiency of the proposed method. Simultaneously, the application case of the similarity recognition in a mechanism creation is given to provide a reference for an innovative design.
{"title":"Novel loop tree for the similarity recognition of kinematic chains","authors":"Lei Wang, Liang Sun, Rongjiang Cui, Yadan Xu, Gaohong Yu, C. Wu","doi":"10.5194/ms-13-371-2022","DOIUrl":"https://doi.org/10.5194/ms-13-371-2022","url":null,"abstract":"Abstract. The similarity recognition of kinematic chains (KCs) is\u0000helpful for improving the efficiency of configuration synthesis, which has been paid more and more attention in recent years. The existing recognition methods are divided into the definition method and feature constant method. Among them, the definition method is difficult to adopt in practice because of its long operation time, especially when the number of similar vertices in KCs is large. In this paper, the new concepts of a loop tree (LT) and a loop tree matrix (LTM) have been proposed, which improve the efficiency of similarity recognition. This method is applied on the complete structure\u0000of the following: 8-link with 1 DOF (degree of freedom), 9-link with 2 DOF, 10-link with 1 DOF, 12-link with 1 DOF, 13-link with 2 DOF, 14-link with 3 DOF, 15-link with 4 DOF planar single-joint KCs, and contracted graphs with up to six independent loops. All results are verified by the definition method to prove the good applicability, reliability, and\u0000efficiency of the proposed method. Simultaneously, the application case of the similarity recognition in a mechanism creation is given to provide a reference for an innovative design.\u0000","PeriodicalId":18413,"journal":{"name":"Mechanical Sciences","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48405375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Robotic surface treatment is already broadly used in the manufacturing industry because it guarantees repeatable high-quality surfaces at short production time. Such a robotic solution, with an accurate control of the applied force on a surface, requires a robot that is either equipped with a force/torque sensor or, alternatively, with a force compliance device. However, without a direct performance comparison, it is hard to know which is the best option for a specific surface treatment operation. Compared to the evaluation of the robot positioning accuracy, using the ISO 9283 test, no standardized test for the quality assessment of robot force control exists yet. In trying to fill this gap, this paper introduces different test scenarios and a test set-up for such a force control quality assessment. As a start, the force control of a Universal Robots UR10e model and a FerRobotics ACF-K 109/04 model are experimentally evaluated. The latter is an external device with controlled force/compliance characteristics, which is referred to as an active contact flange (ACF). For the performance comparison, an ATI force/torque sensor, which is mounted below a work piece, measures the applied force either by the UR or by the ACF. The measured forces are further transformed to the UR tool centre point (TCP) frame. Then, only the z component of the force, or rather the normal force, is relevant for surface treatment and hence important for the evaluation. For each test case, the average value of five test runs with the same parameters is used for the assessment. Results for both the UR and ACF force control are presented for varying desired contact velocities and desired forces. These results indicate the advantage of the ACF-K 109/04 over the UR10e force control for highly dynamic force control scenarios.
{"title":"Assessment of force control for surface finishing – an experimental comparison between Universal Robots UR10e and FerRobotics active contact flange","authors":"Stefan Gadringer, H. Gattringer, A. Mueller","doi":"10.5194/ms-13-361-2022","DOIUrl":"https://doi.org/10.5194/ms-13-361-2022","url":null,"abstract":"Abstract. Robotic surface treatment is already broadly used in the manufacturing industry because it guarantees repeatable high-quality surfaces at short production time. Such a robotic solution, with an accurate control of the applied force on a surface, requires a robot that is either equipped with a force/torque sensor or, alternatively, with a force compliance device. However, without a direct performance comparison, it is hard to know which is the best option for a specific surface treatment operation. Compared to the evaluation of the robot positioning accuracy, using the ISO 9283 test, no standardized test for the quality assessment of robot force control exists yet. In trying to fill this gap, this paper introduces different test scenarios and a test set-up for such a force control quality assessment. As a start, the force control of a Universal Robots UR10e model and a FerRobotics ACF-K 109/04 model are experimentally evaluated. The latter is an external device with controlled force/compliance characteristics, which is referred to as an active contact flange (ACF). For the performance comparison, an ATI force/torque sensor, which is mounted below a work piece, measures the applied force either by the UR or by the ACF. The measured forces are further transformed to the UR tool centre point (TCP) frame. Then, only the z component of the force, or rather the normal force, is relevant for surface treatment and hence important for the evaluation. For each test case, the average value of five test runs with the same parameters is used for the assessment. Results for both the UR and ACF force control are presented for varying desired contact velocities and desired forces. These results indicate the advantage of the ACF-K 109/04 over the UR10e force control for highly dynamic force control scenarios.\u0000","PeriodicalId":18413,"journal":{"name":"Mechanical Sciences","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41429172","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Weiwei Hong, Jinxin Chen, Bingliang Ye, Rongjiang Cui
Abstract. Obtaining new models of mechanical equipment to conduct mechanical innovative design through kinematic chain configuration synthesis is an effective method. However, in practice, due to the existence of similar components, existing innovative design methods easily produce redundant design schemes, which require extensive isomorphic discrimination operations, and the design process is complex. In view of existing problems, this study analyzes a method for discriminating between similar components of mechanisms from the perspective of graph theory and then applies it to the specialization of topological graphs to solve the problem of redundant design schemes. Finally, using the innovation of a drilling rig drilling arm mechanism as an example, 52 feasible schemes without redundancy are obtained. This paper provides a reference for the innovation of the configuration of planar mechanisms without design redundancy.
{"title":"Innovative design method for planar mechanism configuration based on component similarity discrimination","authors":"Weiwei Hong, Jinxin Chen, Bingliang Ye, Rongjiang Cui","doi":"10.5194/ms-13-353-2022","DOIUrl":"https://doi.org/10.5194/ms-13-353-2022","url":null,"abstract":"Abstract. Obtaining new models of mechanical equipment to conduct mechanical\u0000innovative design through kinematic chain configuration synthesis is an\u0000effective method. However, in practice, due to the existence of similar\u0000components, existing innovative design methods easily produce redundant\u0000design schemes, which require extensive isomorphic discrimination\u0000operations, and the design process is complex. In view of existing problems,\u0000this study analyzes a method for discriminating between similar components of\u0000mechanisms from the perspective of graph theory and then applies it to the\u0000specialization of topological graphs to solve the problem of redundant design\u0000schemes. Finally, using the innovation of a drilling rig drilling arm mechanism\u0000as an example, 52 feasible schemes without redundancy are\u0000obtained. This paper provides a reference for the innovation of the configuration of\u0000planar mechanisms without design redundancy.\u0000","PeriodicalId":18413,"journal":{"name":"Mechanical Sciences","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45391656","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Test planning is a crucial step in the operational modal analysis (OMA) of wind turbines (WT), and it is an essential part of choosing the best positions for installing the sensors of the structures. On the other hand, updating the finite element model (FEM) with the OMA results implies a better prediction of the real structure's dynamic and vibrational behavior. This paper aims to show how the OMA of a nonuniform and two-section wind turbine tower can be performed more effectively, using the required test planning and optimal sensor placement. Then, accordingly, the OMA is used in operating and parked conditions to find the objective bending mode characteristics. Moreover, the updating of the applicable FEM of the multi-sectional wind turbine tower will be described. The tailor-made genetic algorithm (GA) is used to find the MEMS (micro electro-mechanical system) sensors' optimal positions of the WT under study. The OMA was performed and the acquired data analyzed using the stochastic subspace identification (SSI) method. Based on the OMA results, the FEM is updated by applying the sensitivity method. The results show that a tailor-made GA is a practical and quick approach to finding the optimal position of the sensors to obtain the best results for the objective modes of the WT. The OMA results, under operating and parked conditions, prove some modal characteristics of WTs. Based on the sensitivity analysis and engineering judgment, the modulus of elasticity was selected as a parameter for updating. Finally, we found that the updated FEM had less than 1 % error compared to the obtained frequencies from the test.
{"title":"Optimal sensor placement and model updating applied to the operational modal analysis of a nonuniform wind turbine tower","authors":"Mohammad Tamizifar, M. Mosayebi, S. Ziaei-Rad","doi":"10.5194/ms-13-331-2022","DOIUrl":"https://doi.org/10.5194/ms-13-331-2022","url":null,"abstract":"Abstract. Test planning is a crucial step in the operational modal analysis (OMA) of wind turbines (WT), and it is an essential part of choosing the best positions for installing the sensors of the structures. On the other hand, updating the finite element model (FEM) with the OMA results implies a better prediction of the real structure's dynamic and vibrational behavior. This paper aims to show how the OMA of a nonuniform and two-section wind turbine tower can be performed more effectively, using the required test planning and optimal sensor placement. Then, accordingly, the OMA is used in operating and parked conditions to find the objective bending mode characteristics. Moreover, the updating of the applicable FEM of the multi-sectional wind turbine tower will be described. The tailor-made genetic algorithm (GA) is used to find the MEMS (micro electro-mechanical system) sensors' optimal positions of the WT under study. The OMA was performed and the acquired data analyzed using the stochastic subspace identification (SSI) method. Based on the OMA results, the FEM is updated by applying the sensitivity method. The results show that a tailor-made GA is a practical and quick approach to finding the optimal position of the sensors to obtain the best results for the objective modes of the WT. The OMA results, under operating and parked conditions, prove some modal characteristics of WTs. Based on the sensitivity analysis and engineering judgment, the modulus of elasticity was selected as a parameter for updating. Finally, we found that the updated FEM had less than 1 % error compared to the obtained frequencies from the test.\u0000","PeriodicalId":18413,"journal":{"name":"Mechanical Sciences","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42702389","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
V. Verbitskii, V. Lobas, Yevgen Misko, A. Bondarenko
Abstract. This paper presents the bifurcation approach to analyze divergent loss of stability of the symmetric solution of a nonlinear dynamic model in Lyapunov's critical case of a single zero root. Under such a condition, material birth-annihilation bifurcations of multiple stationary states take place. Moreover, the equilibrium surface of stationary states in a small neighborhood of the symmetric solution is a generalized Whitney fold. In the simplest case of a fold peculiarity, the corresponding bifurcation manifold locally coincides with the discriminant manifold of a third-degree polynomial that determines the manifold of stationary states in a small neighborhood of the symmetric solution. An algorithm to construct the corresponding polynomial is introduced. Through the algorithm, the bifurcation manifold is determined, and the conditions for safe/unsafe loss of stability of the symmetric solution are derived analytically. The proposed approach to analyze divergent loss of stability is implemented for a nonlinear bicycle model of a two-axle wheeled vehicle. It represents a further development of Pevzner–Pacejka's well-known graph-analytical method. The paper determines the critical values of constructive parameters that are responsible for safe/unsafe loss of stability of the vehicle's straight-line motion, and it discusses strategies for the bifurcation approach to analyze divergent loss of stability.
{"title":"Analysis of divergent bifurcations in the dynamics of wheeled vehicles","authors":"V. Verbitskii, V. Lobas, Yevgen Misko, A. Bondarenko","doi":"10.5194/ms-13-321-2022","DOIUrl":"https://doi.org/10.5194/ms-13-321-2022","url":null,"abstract":"Abstract. This paper presents the bifurcation approach to analyze divergent\u0000loss of stability of the symmetric solution of a nonlinear dynamic model in\u0000Lyapunov's critical case of a single zero root. Under such a condition,\u0000material birth-annihilation bifurcations of multiple stationary states take\u0000place. Moreover, the equilibrium surface of stationary states in a small\u0000neighborhood of the symmetric solution is a generalized Whitney fold. In the\u0000simplest case of a fold peculiarity, the corresponding bifurcation manifold\u0000locally coincides with the discriminant manifold of a third-degree\u0000polynomial that determines the manifold of stationary states in a small\u0000neighborhood of the symmetric solution. An algorithm to construct the corresponding polynomial is introduced.\u0000Through the algorithm, the bifurcation manifold is determined, and the\u0000conditions for safe/unsafe loss of stability of the symmetric solution are\u0000derived analytically. The proposed approach to analyze divergent loss of stability is implemented\u0000for a nonlinear bicycle model of a two-axle wheeled vehicle. It represents\u0000a further development of Pevzner–Pacejka's well-known graph-analytical\u0000method. The paper determines the critical values of constructive parameters\u0000that are responsible for safe/unsafe loss of stability of the vehicle's\u0000straight-line motion, and it discusses strategies for the bifurcation\u0000approach to analyze divergent loss of stability.\u0000","PeriodicalId":18413,"journal":{"name":"Mechanical Sciences","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48418563","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. In this paper, a novel parallel leaf-spring carrying mechanism (PLCM) is investigated using a compliance-matrix-based approach. For the analytical modeling and attitude calculation, the geometric errors of the flexible arm, including the height and the top plane's direction, are considered, and the displacement method is used to calculate the equilibrium attitude. The influence of the equilibrium attitude at different heights and the initial tilts of the top planes are analyzed separately. The validity and effectiveness of the attitude calculation are illustrated by experimental verification. The laser triangulation coordinate method is used for attitude measurement. The deviations of the normal vector between the calculation results and measurement results are smaller than 2×10-4, which is small enough to satisfy practical requirements. This can be used to guarantee stable and accurate wafer transfer in a lithography machine. Therefore, it can be concluded that the methods employed for analytical model establishment and attitude calculation can be used as a reference for the analysis and design of a complex parallel compliant mechanism.
{"title":"Analytical model establishment and attitude calculation of a parallel leaf-spring carrying mechanism","authors":"P. Li, Z. Tong, Wei-hua Zhang","doi":"10.5194/ms-13-311-2022","DOIUrl":"https://doi.org/10.5194/ms-13-311-2022","url":null,"abstract":"Abstract. In this paper, a novel parallel leaf-spring carrying mechanism (PLCM)\u0000is investigated using a compliance-matrix-based approach.\u0000For the analytical modeling and attitude calculation, the geometric errors of the\u0000flexible arm, including the height and the top plane's direction, are considered, and the\u0000displacement method is used to calculate the equilibrium attitude. The\u0000influence of the equilibrium attitude at different heights and the initial tilts of the\u0000top planes are analyzed separately. The validity and effectiveness of the\u0000attitude calculation are illustrated by experimental verification. The laser\u0000triangulation coordinate method is used for attitude measurement. The\u0000deviations of the normal vector between the calculation results and measurement\u0000results are smaller than 2×10-4, which is small enough to satisfy\u0000practical requirements. This can be used to guarantee stable and accurate\u0000wafer transfer in a lithography machine. Therefore, it can be concluded\u0000that the methods employed for analytical model establishment and attitude\u0000calculation can be used as a reference for the analysis and design of a\u0000complex parallel compliant mechanism.\u0000","PeriodicalId":18413,"journal":{"name":"Mechanical Sciences","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43249889","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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