Abstract. A novel method is presented for efficiently analyzing the reliability of engineering components and systems with highly nonlinear complex limit state functions. The proposed method begins by transforming the integral of the limit state function into an integral of a highly correlated limit state function using the control variates method. The second-order reliability method is then employed within the control variates framework to approximate the highly correlated limit state function as a quadratic polynomial. Subsequently, the probability of failure is obtained through the estimation of the saddle-point approximation and a small number of samples generated by Latin hypercube sampling. To demonstrate the effectiveness of the proposed method, four examples involving mathematical functions and mechanical problems are solved. The results are compared with those obtained using the second-order reliability method (SORM), control variates based on Monte Carlo simulation (CVMCS) with second-order saddle-point approximation (SOSPA), importance sampling (IS) and Monte Carlo simulation (MCS). The findings demonstrate that, while maintaining high-precision reliability results, the proposed method significantly reduces the number of evaluations of the limit state function through a small number of initial samples. The method is capable of efficiently and accurately solving complex practical engineering reliability problems.
{"title":"Modified control variates method based on second-order saddle-point approximation for practical reliability analysis","authors":"Xinong En, Yimin Zhang, Xianzhen Huang","doi":"10.5194/ms-14-439-2023","DOIUrl":"https://doi.org/10.5194/ms-14-439-2023","url":null,"abstract":"Abstract. A novel method is presented for efficiently analyzing the reliability of engineering components and systems with highly nonlinear complex limit state functions. The proposed method begins by transforming the integral of the limit state function into an integral of a highly correlated limit state function using the control variates method. The second-order reliability method is then employed within the control variates framework to approximate the highly correlated limit state function as a quadratic polynomial. Subsequently, the probability of failure is obtained through the estimation of the saddle-point approximation and a small number of samples generated by Latin hypercube sampling. To demonstrate the effectiveness of the proposed method, four examples involving mathematical functions and mechanical problems are solved. The results are compared with those obtained using the second-order reliability method (SORM), control variates based on Monte Carlo simulation (CVMCS) with second-order saddle-point approximation (SOSPA), importance sampling (IS) and Monte Carlo simulation (MCS). The findings demonstrate that, while maintaining high-precision reliability results, the proposed method significantly reduces the number of evaluations of the limit state function through a small number of initial samples. The method is capable of efficiently and accurately solving complex practical engineering reliability problems.","PeriodicalId":18413,"journal":{"name":"Mechanical Sciences","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135729691","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. To reduce energy consumption while a human is walking with different loads, an active energy storage mechanism and a gait cycle prediction method are proposed, and then a wearable ankle assistance robot is developed. A motor, a clutch, and elastic rods are placed strategically in the active energy storage mechanism to achieve energy storage and release. During the period when the ankle does not generate torque, the clutch is closed, and the elastic rods are driven by the motor to produce deformation for energy storage. When the ankle generates torque, the motor is stopped and the clutch is opened, and then energy is released. Assisted force is transmitted to the human heel by a flexible transmission device to achieve walking assistance. The deformation length of the elastic rods can be changed to achieve assisted force adjustment for different loads. Based on the hip angular displacement and heel pressure, the gait cycle can be obtained with the proposed prediction method, and then assistance control can be achieved. Consequently, the development of a wearable ankle assistance robot is realized, a walking assistance experiment with different loads is completed, and the net metabolic cost is used to indicate the energy consumption. The experimental results show that the net metabolic cost of the participants is reduced by averages of 5.30 %, 5.67 %, and 4.84 % with 0, 4, and 8 kg loads respectively. The reduced net metabolic costs are compared with other research results; the reduced net metabolic costs are close to the others, but the motor power in this work is lower.
{"title":"Wearable ankle assistance robot for a human walking with different loads","authors":"Junqiang Li, Kuan Yang, Dong Yang","doi":"10.5194/ms-14-429-2023","DOIUrl":"https://doi.org/10.5194/ms-14-429-2023","url":null,"abstract":"Abstract. To reduce energy consumption while a human is walking with different loads, an active energy storage mechanism and a gait cycle prediction method are proposed, and then a wearable ankle assistance robot is developed. A motor, a clutch, and elastic rods are placed strategically in the active energy storage mechanism to achieve energy storage and release. During the period when the ankle does not generate torque, the clutch is closed, and the elastic rods are driven by the motor to produce deformation for energy storage. When the ankle generates torque, the motor is stopped and the clutch is opened, and then energy is released. Assisted force is transmitted to the human heel by a flexible transmission device to achieve walking assistance. The deformation length of the elastic rods can be changed to achieve assisted force adjustment for different loads. Based on the hip angular displacement and heel pressure, the gait cycle can be obtained with the proposed prediction method, and then assistance control can be achieved. Consequently, the development of a wearable ankle assistance robot is realized, a walking assistance experiment with different loads is completed, and the net metabolic cost is used to indicate the energy consumption. The experimental results show that the net metabolic cost of the participants is reduced by averages of 5.30 %, 5.67 %, and 4.84 % with 0, 4, and 8 kg loads respectively. The reduced net metabolic costs are compared with other research results; the reduced net metabolic costs are close to the others, but the motor power in this work is lower.","PeriodicalId":18413,"journal":{"name":"Mechanical Sciences","volume":"106 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136057473","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}
Tao Qin, Qianpeng Wang, Wei Su, Chao Wei, Yanduo Zhang, Jianwei Zhang
Abstract. In this paper, a cable-driven body weight support gait training robot (C-BWSGTR) that provides patients with partial body weight support as well as a kind of stable gait training driving force was designed; this device enabled those patients to walk again. Firstly, the overall configuration of the C-BWSGTR was determined, and the structural composition and working principle of the robot were established. Secondly, the vector algebra method was applied to carry out the kinematic analysis and establish the mathematical model of the C-BWSGTR. The displacement of each cable during the patient gait training was also calculated. Thirdly, the motion planning of the C-BWSGTR was carried out in stages, using the time–phase distribution relationship based on an S-shaped speed curve. Meanwhile, the displacement, speed, and acceleration of each cable during the patient gait training were calculated and corresponding change curves were generated. Finally, a position servo composite control strategy for the C-BWSGTR was designed by analyzing the robot's dynamic characteristics of the forward channel transfer function. The simulation analysis and prototype experiment in this paper verified that the designed composite position servo control strategy can meet the requirements of the system with respect to stability and a fast response of the system to the loading command.
{"title":"Motion planning and control strategy of a cable-driven body weight support gait training robot","authors":"Tao Qin, Qianpeng Wang, Wei Su, Chao Wei, Yanduo Zhang, Jianwei Zhang","doi":"10.5194/ms-14-413-2023","DOIUrl":"https://doi.org/10.5194/ms-14-413-2023","url":null,"abstract":"Abstract. In this paper, a cable-driven body weight support gait training robot (C-BWSGTR) that provides patients with partial body weight support as well as a kind of stable gait training driving force was designed; this device enabled those patients to walk again. Firstly, the overall configuration of the C-BWSGTR was determined, and the structural composition and working principle of the robot were established. Secondly, the vector algebra method was applied to carry out the kinematic analysis and establish the mathematical model of the C-BWSGTR. The displacement of each cable during the patient gait training was also calculated. Thirdly, the motion planning of the C-BWSGTR was carried out in stages, using the time–phase distribution relationship based on an S-shaped speed curve. Meanwhile, the displacement, speed, and acceleration of each cable during the patient gait training were calculated and corresponding change curves were generated. Finally, a position servo composite control strategy for the C-BWSGTR was designed by analyzing the robot's dynamic characteristics of the forward channel transfer function. The simulation analysis and prototype experiment in this paper verified that the designed composite position servo control strategy can meet the requirements of the system with respect to stability and a fast response of the system to the loading command.","PeriodicalId":18413,"journal":{"name":"Mechanical Sciences","volume":"162 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135142114","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. Resource coordination and allocation strategies are proposed to reduce the probability of failure by aiming at the problem that the robot cannot continue to work after joint failure. Firstly, the principal component analysis method under unsupervised branches in machine learning is used to analyze the reliability function and various indexes of the robot to obtain the comprehensive evaluation function. Then, based on the fault-tolerant-control inverse-kinematics optimal algorithm, each joint can be scheduled by weighted processing. Finally, the comprehensive evaluation function is used as an index to evaluate the probability of fault occurrence, and the weight is defined to realize the coordinated resource allocation of redundant robots. Taking the planar four revolute joints (4R) redundant robot as an example, the algorithm control is compared. Based on reasonable modeling and physical verification, the results show that the method of optimal resource coordination and allocation is effective.
{"title":"Optimal resource allocation method and fault-tolerant control for redundant robots","authors":"Yu Rong, Tianci Dou, Xingchao Zhang","doi":"10.5194/ms-14-399-2023","DOIUrl":"https://doi.org/10.5194/ms-14-399-2023","url":null,"abstract":"Abstract. Resource coordination and allocation strategies are proposed to reduce the probability of failure by aiming at the problem that the robot cannot continue to work after joint failure. Firstly, the principal component analysis method under unsupervised branches in machine learning is used to analyze the reliability function and various indexes of the robot to obtain the comprehensive evaluation function. Then, based on the fault-tolerant-control inverse-kinematics optimal algorithm, each joint can be scheduled by weighted processing. Finally, the comprehensive evaluation function is used as an index to evaluate the probability of fault occurrence, and the weight is defined to realize the coordinated resource allocation of redundant robots. Taking the planar four revolute joints (4R) redundant robot as an example, the algorithm control is compared. Based on reasonable modeling and physical verification, the results show that the method of optimal resource coordination and allocation is effective.","PeriodicalId":18413,"journal":{"name":"Mechanical Sciences","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135350754","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}
Ruiming Li, Xianhong Zhang, Shuo Zhang, Ran Liu, Yan-an Yao
Abstract. This paper deals with the construction of a novel family of multimode deployable mechanisms based on reconfigurable Bricard-like mechanisms. By connecting a number of identical threefold-symmetric (TFS) Bricard-like mechanisms, a multimode deployable arch is proposed for the first time, which can switch between the scissor-like deployable mode and the arch deformable mode through the transition configuration. Then new multimode center-driven deployable mechanisms can be obtained by connecting three and six multimode deployable arches. The obtained mechanism can switch between the scissor-like deployable mode and spherical deformable mode, and it can be reassembled by adjusting the number of TFS Bricard-like mechanisms to change its size. Finally, physical prototypes of the multimode deployable arch and multimode center-driven deployable mechanisms are fabricated and tested to validate the feasibility of the proposed approach and analysis.
{"title":"Assembly of reconfigurable Bricard-like mechanisms to form a multimode deployable arch","authors":"Ruiming Li, Xianhong Zhang, Shuo Zhang, Ran Liu, Yan-an Yao","doi":"10.5194/ms-14-387-2023","DOIUrl":"https://doi.org/10.5194/ms-14-387-2023","url":null,"abstract":"Abstract. This paper deals with the construction of a novel family of multimode deployable mechanisms based on reconfigurable Bricard-like mechanisms. By connecting a number of identical threefold-symmetric (TFS) Bricard-like mechanisms, a multimode deployable arch is proposed for the first time, which can switch between the scissor-like deployable mode and the arch deformable mode through the transition configuration. Then new multimode center-driven deployable mechanisms can be obtained by connecting three and six multimode deployable arches. The obtained mechanism can switch between the scissor-like deployable mode and spherical deformable mode, and it can be reassembled by adjusting the number of TFS Bricard-like mechanisms to change its size. Finally, physical prototypes of the multimode deployable arch and multimode center-driven deployable mechanisms are fabricated and tested to validate the feasibility of the proposed approach and analysis.","PeriodicalId":18413,"journal":{"name":"Mechanical Sciences","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135200229","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}
Sen Qian, Xiao Jiang, Yong Liu, Shuaikang Wang, Xiantao Sun, Huihui Sun
Abstract. In large-scale 3D additive manufacturing (AM), rigid printing mechanisms exhibit high inertia and inadequate load capacity. In this paper, a fully constrained 3-degrees-of-freedom (DOFs) cable-driven hybrid mechanism (CDHR) is developed. A vector analysis method considering error compensation in the pulley system is proposed for analysing the kinematics and dynamics. To address the cable-driven mechanism's strict cable force range requirement, a prescribed-performance controller (PPC) with an adaptive auxiliary system is designed for the nonlinear cable system to enhance the stability and motion accuracy of the end-effector. The stability of the control system is proven using the Lyapunov function. A physical simulation environment using Simscape is developed to verify the vector analysis method and the PPC. Subsequently, an experimental prototype of a 3-DOF CDHR is developed. The results of the error compensation experiment and the prescribed-performance controller experiment demonstrate a 93.321 % reduction in maximum plane error and a 95.376 % reduction in maximum height error for the PPC considering error compensation compared to the non-compensation trajectory. Finally, a double-layer clay-printing experiment is conducted to validate the feasibility of the mechanism.
{"title":"Design and error compensation of a 3-degrees-of-freedom cable-driven hybrid 3D-printing mechanism","authors":"Sen Qian, Xiao Jiang, Yong Liu, Shuaikang Wang, Xiantao Sun, Huihui Sun","doi":"10.5194/ms-14-371-2023","DOIUrl":"https://doi.org/10.5194/ms-14-371-2023","url":null,"abstract":"Abstract. In large-scale 3D additive manufacturing (AM), rigid printing mechanisms exhibit high inertia and inadequate load capacity. In this paper, a fully constrained 3-degrees-of-freedom (DOFs) cable-driven hybrid mechanism (CDHR) is developed. A vector analysis method considering error compensation in the pulley system is proposed for analysing the kinematics and dynamics. To address the cable-driven mechanism's strict cable force range requirement, a prescribed-performance controller (PPC) with an adaptive auxiliary system is designed for the nonlinear cable system to enhance the stability and motion accuracy of the end-effector. The stability of the control system is proven using the Lyapunov function. A physical simulation environment using Simscape is developed to verify the vector analysis method and the PPC. Subsequently, an experimental prototype of a 3-DOF CDHR is developed. The results of the error compensation experiment and the prescribed-performance controller experiment demonstrate a 93.321 % reduction in maximum plane error and a 95.376 % reduction in maximum height error for the PPC considering error compensation compared to the non-compensation trajectory. Finally, a double-layer clay-printing experiment is conducted to validate the feasibility of the mechanism.\u0000","PeriodicalId":18413,"journal":{"name":"Mechanical Sciences","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47524476","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}
Chao Yang, Peijiao Li, Yang Wang, Wei Ye, Tianze Sun, Fengli Huang, Hui Zhang
Abstract. In this work, a multi-objective optimization design method is proposed based on principal component analysis (PCA) and a neural network to obtain a mechanism's optimal comprehensive performance. First, multi-objective optimization mathematical modeling, including design parameters, objective functions, and constraint functions, is established. Second, the sample data are obtained through the design of the experiment (DOE) and are then standardized to eliminate the adverse effects of a non-uniform dimension of objective functions. Third, the first k principal components are established for p performance indices (k
{"title":"Multi-objective optimization design of parallel manipulators using a neural network and principal component analysis","authors":"Chao Yang, Peijiao Li, Yang Wang, Wei Ye, Tianze Sun, Fengli Huang, Hui Zhang","doi":"10.5194/ms-14-361-2023","DOIUrl":"https://doi.org/10.5194/ms-14-361-2023","url":null,"abstract":"Abstract. In this work, a multi-objective optimization design method is proposed based on principal component analysis (PCA) and a neural network to obtain a mechanism's optimal comprehensive performance. First,\u0000multi-objective optimization mathematical modeling, including design\u0000parameters, objective functions, and constraint functions, is established.\u0000Second, the sample data are obtained through the design of the experiment\u0000(DOE) and are then standardized to eliminate the adverse effects of a\u0000non-uniform dimension of objective functions. Third, the first k principal components are established for p performance indices (k<p) using the\u0000variance-based PCA method, and then the factor analysis method is employed\u0000to define its physical meaning. Fourth, the overall comprehensive\u0000performance evaluation index is established by objectively determining\u0000weight factors. Finally, the computational cost of the modeling is improved\u0000by combining the neural network and a particle swarm optimization (PSO)\u0000algorithm. Dimensional synthesis of a Sprint (3RPS) parallel manipulator (PM) is taken as a case study to implement the proposed method, and the\u0000optimization results are verified by a comprehensive performance comparison of robots before and after optimization.\u0000","PeriodicalId":18413,"journal":{"name":"Mechanical Sciences","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46701069","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}
Liming Zhang, Xiaohua Wang, Haoyi Wang, Pengfei Li
Abstract. In human–robot collaborative sewing, the robot follows the sewing action of a worker to complete the corresponding sewing action, which can enhance production efficiency. When the robot follows the sewing action of the worker through interactive information, it still faces the problem of low accuracy. In order to improve the accuracy of the robot following the sewing action, a human upper-limb sewing-action-following system based on visual information is designed in this paper. The system is composed of an improved OpenPose model, Gaussian mixture model (GMM), and Gaussian mixture regression (GMR). In the system, an improved OpenPose model is used to identify the sewing action of the human upper limb, and the label fusion method is used to correct the joint point labels when the upper limb is covered by fabric. Then the GMM is used to encode each motion element and time to obtain the regression work of the Gaussian component. GMR is adopted to predict connections between moving elements and generate sewing motion trajectories. Finally, the experimental verification and simulation are carried out in the experimental platform and simulation environment of the collaborative robot. The experimental results show that the tracking error angle can be controlled within 0.04 rad in the first 2 s of robot movement. Therefore, it can be considered that the sewing-action-following system can realize higher precision and promote the development of human–robot collaboration technology to a certain extent.
{"title":"A vision-based robotic system following the human upper-limb sewing action","authors":"Liming Zhang, Xiaohua Wang, Haoyi Wang, Pengfei Li","doi":"10.5194/ms-14-347-2023","DOIUrl":"https://doi.org/10.5194/ms-14-347-2023","url":null,"abstract":"Abstract. In human–robot collaborative sewing, the robot follows the sewing action of a worker to complete the corresponding sewing action, which can enhance production efficiency. When the robot follows the sewing action of the worker through interactive information, it still faces the problem of low accuracy. In order to improve the accuracy of the robot following the sewing action, a human upper-limb sewing-action-following system based on visual information is designed in this paper. The system is composed of an improved OpenPose model, Gaussian mixture model (GMM), and Gaussian mixture regression (GMR). In the system, an improved OpenPose model is used to identify the sewing action of the human upper limb, and the label fusion method is used to correct the joint point labels when the upper limb is covered by fabric. Then the GMM is used to encode each motion element and time to obtain the regression work of the Gaussian component. GMR is adopted to predict connections between moving elements and generate sewing motion trajectories. Finally, the experimental verification and simulation are carried out in the experimental platform and simulation environment of the collaborative robot. The experimental results show that the tracking error angle can be controlled within 0.04 rad in the first 2 s of robot movement. Therefore, it can be considered that the sewing-action-following system can realize higher precision and promote the development of human–robot collaboration technology to a certain extent.\u0000","PeriodicalId":18413,"journal":{"name":"Mechanical Sciences","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48983794","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 study, the noise of the gear transmission system for two-speed automatic transmission (2EAT) of pure electric vehicles was analyzed and optimized. Firstly, through vehicle noise tests, poor working conditions and noise contribution of each gear pair were determined with the order analysis method. Secondly, a dynamics calculation model and a simulation model of the gear transmission system were established and the poor meshing state of the main reducer gear pair under specific conditions was determined as the main cause of noise. Finally, a genetic algorithm combined the weight method was used for gear modification. After gear modifications, the fluctuation range of transmission error was reduced and the contact condition of the tooth surface was significantly improved.
{"title":"Noise analysis and optimization of the gear transmission system for two-speed automatic transmission of pure electric vehicles","authors":"Z.-Y.ab Shi, Shikai Liu, H. Yue, Xiaoxiao Wu","doi":"10.5194/ms-14-333-2023","DOIUrl":"https://doi.org/10.5194/ms-14-333-2023","url":null,"abstract":"Abstract. In this study, the noise of the gear transmission system for two-speed automatic transmission (2EAT) of pure electric vehicles was analyzed and optimized. Firstly, through vehicle noise tests, poor working conditions and noise contribution of each gear pair were determined with the order analysis method. Secondly, a dynamics calculation model and a simulation model of the gear transmission system were established and the poor meshing state of the main reducer gear pair under specific conditions was determined as the main cause of noise. Finally, a genetic algorithm combined the weight method was used for gear modification. After gear\u0000modifications, the fluctuation range of transmission error was reduced and\u0000the contact condition of the tooth surface was significantly improved.\u0000","PeriodicalId":18413,"journal":{"name":"Mechanical Sciences","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42222720","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. When patients with lower limb dyskinesia use robots for rehabilitation training, gait parameters are of great significance for disease diagnosis and rehabilitation evaluation. Gait measurement is usually carried out by using optical motion capture systems, pressure plates and so on. However, it is difficult to apply these systems to lower limb rehabilitation robots due to their high price, limited scope and wearing requirements. At the same time, most of the current applications in robots focus on the basic gait parameters (such as step length and step speed) for robot control or user intention recognition. Therefore, this paper proposes an online gait analysis algorithm for lower limb rehabilitation robots, which uses a lidar sensor as the gait data acquisition sensor. The device is installed on the lower limb rehabilitation robot, which not only avoids the problems of decline in the detection accuracy and failure of leg tracking caused by lidar placement on the ground, but it also calculates seven gait parameters, such as step length, stride length, gait cycle and stance time, with high precision in real time. At the same time, the walking track of the patient may not be straight, and the lidar coordinate system is also changed due to the movement of the lower limb rehabilitation robot when the patient moves forward. In order to overcome this situation, a spatial parameter-splicing algorithm based on a time series is proposed to effectively reduce the error impact on gait spatiotemporal parameters. The experimental results show that the gait analysis algorithm proposed in this paper can measure the gait parameters effectively and accurately. Except for the swing time and double support time, which are calculated with large relative errors due to their small values, the relative errors of the remaining gait parameters are kept below 8 %, meeting the requirements of clinical applications.
{"title":"Gait analysis algorithm for lower limb rehabilitation robot applications","authors":"Li Zheng, Tao Song","doi":"10.5194/ms-14-315-2023","DOIUrl":"https://doi.org/10.5194/ms-14-315-2023","url":null,"abstract":"Abstract. When patients with lower limb dyskinesia use robots for\u0000rehabilitation training, gait parameters are of great significance for\u0000disease diagnosis and rehabilitation evaluation. Gait measurement is usually\u0000carried out by using optical motion capture systems, pressure plates and so\u0000on. However, it is difficult to apply these systems to lower limb\u0000rehabilitation robots due to their high price, limited scope and wearing\u0000requirements. At the same time, most of the current applications in robots\u0000focus on the basic gait parameters (such as step length and step speed) for\u0000robot control or user intention recognition. Therefore, this paper proposes\u0000an online gait analysis algorithm for lower limb rehabilitation robots,\u0000which uses a lidar sensor as the gait data\u0000acquisition sensor. The device is installed on the lower limb rehabilitation robot, which not only avoids the problems of decline in the detection\u0000accuracy and failure of leg tracking caused by lidar placement on the\u0000ground, but it also calculates seven gait parameters, such as step length, stride length, gait cycle and stance time, with high precision in real time. At the\u0000same time, the walking track of the patient may not be straight, and the\u0000lidar coordinate system is also changed due to the movement of the lower\u0000limb rehabilitation robot when the patient moves forward. In order to\u0000overcome this situation, a spatial parameter-splicing algorithm based on\u0000a time series is proposed to effectively reduce the error impact on gait\u0000spatiotemporal parameters. The experimental results show that the gait\u0000analysis algorithm proposed in this paper can measure the gait parameters\u0000effectively and accurately. Except for the swing time and double support\u0000time, which are calculated with large relative errors due to their small\u0000values, the relative errors of the remaining gait parameters are kept below\u00008 %, meeting the requirements of clinical applications.\u0000","PeriodicalId":18413,"journal":{"name":"Mechanical Sciences","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46135317","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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