In this study, we developed an offline, hierarchical intent recognition system for inferring the timing and direction of motion intent of a human operator when operating in an unstructured environment. There has been an increasing demand for robot agents to assist in these dynamic, rapid motions that are constantly evolving and require quick, accurate estimation of a user’s direction of travel. An experiment was conducted in a motion capture space with six subjects performing threat evasion in eight directions, and their mechanical and neuromuscular signals were recorded for use in our intent recognition system (XGBoost). Investigated against current, analytical methods, our system demonstrated superior performance with quicker direction of travel estimation occurring 140 ms earlier in the movement and a 11.6 deg reduction of error. The results showed that we could also predict the start of the movement 100 ms prior to the actual, thus allowing any physical systems to start up. Our direction estimation had an optimal performance of 8.8 deg, or 2.4% of the 360 deg range of travel, using three-axis kinetic data. The performance of other sensors and their combinations indicate that there are additional possibilities to obtain low estimation error. These findings are promising as they can be used to inform the design of a wearable robot aimed at assisting users in dynamic motions, while in environments with oncoming threats.
{"title":"Design of an Intent Recognition System for Dynamic, Rapid Motions in Unstructured Environments","authors":"Pooja Moolchandani, A. Mazumdar, Aaron J. Young","doi":"10.1115/1.4051140","DOIUrl":"https://doi.org/10.1115/1.4051140","url":null,"abstract":"\u0000 In this study, we developed an offline, hierarchical intent recognition system for inferring the timing and direction of motion intent of a human operator when operating in an unstructured environment. There has been an increasing demand for robot agents to assist in these dynamic, rapid motions that are constantly evolving and require quick, accurate estimation of a user’s direction of travel. An experiment was conducted in a motion capture space with six subjects performing threat evasion in eight directions, and their mechanical and neuromuscular signals were recorded for use in our intent recognition system (XGBoost). Investigated against current, analytical methods, our system demonstrated superior performance with quicker direction of travel estimation occurring 140 ms earlier in the movement and a 11.6 deg reduction of error. The results showed that we could also predict the start of the movement 100 ms prior to the actual, thus allowing any physical systems to start up. Our direction estimation had an optimal performance of 8.8 deg, or 2.4% of the 360 deg range of travel, using three-axis kinetic data. The performance of other sensors and their combinations indicate that there are additional possibilities to obtain low estimation error. These findings are promising as they can be used to inform the design of a wearable robot aimed at assisting users in dynamic motions, while in environments with oncoming threats.","PeriodicalId":327130,"journal":{"name":"ASME Letters in Dynamic Systems and Control","volume":"78 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132431238","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}
Many modern-day applications involve transport of objects suspended through cables such as in overhead cranes or landing of rovers on the Martian surface. Any undesired oscillation of the payload has the potential risk of instability, and the problem of damping such oscillation and stabilizing the payload at the desired length is the control objective of this article. The system is modeled as a variable length pendulum (VLP), which comprises a payload suspended via a string wrapped around a pulley. The length of the pendulum is varied using clockwise/counterclockwise rotation of the pulley through torque applied by a motor. For a known payload mass, a nonlinear control design is first presented that guarantees asymptotic stability of the desired equilibrium with limited state measurements. The design is then modified for it to handle significant uncertainty in payload mass. The effectiveness of both designs is validated in simulations.
{"title":"Damping Oscillation of Suspended Payload by Varying String Length","authors":"N. Kant","doi":"10.1115/1.4051096","DOIUrl":"https://doi.org/10.1115/1.4051096","url":null,"abstract":"\u0000 Many modern-day applications involve transport of objects suspended through cables such as in overhead cranes or landing of rovers on the Martian surface. Any undesired oscillation of the payload has the potential risk of instability, and the problem of damping such oscillation and stabilizing the payload at the desired length is the control objective of this article. The system is modeled as a variable length pendulum (VLP), which comprises a payload suspended via a string wrapped around a pulley. The length of the pendulum is varied using clockwise/counterclockwise rotation of the pulley through torque applied by a motor. For a known payload mass, a nonlinear control design is first presented that guarantees asymptotic stability of the desired equilibrium with limited state measurements. The design is then modified for it to handle significant uncertainty in payload mass. The effectiveness of both designs is validated in simulations.","PeriodicalId":327130,"journal":{"name":"ASME Letters in Dynamic Systems and Control","volume":"89 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125459143","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}
The classical phenomenon of a sphere transitioning from sliding to rolling during its motion on a horizontal plane is investigated from a novel system theoretic perspective. Specifically, the transition is studied as a problem in stabilization, an approach not reported in the literature. The main contribution of this paper is in proving that pure rolling is an asymptotically stable equilibrium within the state-space of a sliding sphere. It is shown that the stabilization of this equilibrium from arbitrary initial conditions occurs through the natural interplay between the friction force and moment that result from sliding. Simulation results confirm the theoretical development. The stability analysis is extended to motion on an inclined plane.
{"title":"Asymptotic Stability of the Sphere’s Rolling Equilibrium","authors":"Tuhin Das","doi":"10.1115/1.4050980","DOIUrl":"https://doi.org/10.1115/1.4050980","url":null,"abstract":"\u0000 The classical phenomenon of a sphere transitioning from sliding to rolling during its motion on a horizontal plane is investigated from a novel system theoretic perspective. Specifically, the transition is studied as a problem in stabilization, an approach not reported in the literature. The main contribution of this paper is in proving that pure rolling is an asymptotically stable equilibrium within the state-space of a sliding sphere. It is shown that the stabilization of this equilibrium from arbitrary initial conditions occurs through the natural interplay between the friction force and moment that result from sliding. Simulation results confirm the theoretical development. The stability analysis is extended to motion on an inclined plane.","PeriodicalId":327130,"journal":{"name":"ASME Letters in Dynamic Systems and Control","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116250329","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}
This article addresses maximum-a-posteriori (MAP) estimation of linear time-invariant state-space (LTI-SS) models. The joint posterior distribution of the model matrices and the unknown state sequence is approximated by using Rao-Blackwellized Monte-Carlo sampling algorithms. Specifically, the conditional distribution of the state sequence given the model parameters is derived analytically, while only the marginal posterior distribution of the model matrices is approximated using a Metropolis-Hastings Markov Chain Monte-Carlo sampler. From the joint distribution, MAP estimates of the unknown model matrices as well as the state sequence are computed. The performance of the proposed algorithm is demonstrated on a numerical example and on a real laboratory benchmark dataset of a hair dryer process.
{"title":"Maximum—A Posteriori Estimation of Linear Time-Invariant State-Space Models via Efficient Monte-Carlo Sampling","authors":"Manas Mejari, D. Piga","doi":"10.1115/1.4051491","DOIUrl":"https://doi.org/10.1115/1.4051491","url":null,"abstract":"\u0000 This article addresses maximum-a-posteriori (MAP) estimation of linear time-invariant state-space (LTI-SS) models. The joint posterior distribution of the model matrices and the unknown state sequence is approximated by using Rao-Blackwellized Monte-Carlo sampling algorithms. Specifically, the conditional distribution of the state sequence given the model parameters is derived analytically, while only the marginal posterior distribution of the model matrices is approximated using a Metropolis-Hastings Markov Chain Monte-Carlo sampler. From the joint distribution, MAP estimates of the unknown model matrices as well as the state sequence are computed. The performance of the proposed algorithm is demonstrated on a numerical example and on a real laboratory benchmark dataset of a hair dryer process.","PeriodicalId":327130,"journal":{"name":"ASME Letters in Dynamic Systems and Control","volume":"129 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116486300","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}
It is possible to levitate a mass by vibrating a flat disk located under the mass. This near-field acoustic levitation is particularly useful for eliminating friction between moving objects. This paper presents an experimental and theoretical study of the dynamic behavior of a levitating mass for different magnitudes of oscillation of the flat disk. The magnitude of the vibration of the mass appears to be independent of the amplitude of the vibration of the disk over a range of two orders of magnitude. This unusual behavior is due to the simultaneous changes of the stiffness of the air film and the natural frequency of the system as the plate vibration is changed. As the plate oscillation is reduced, the distance to resonance decreases, allowing an increase of the ratio of the output to input signals in such a way that the output remains constant. This result can be useful for improving the energy efficiency of the levitation.
{"title":"Dynamic Invariance in Near-Field Acoustic Levitation","authors":"Nicolas Elie, A. Blouin, N. Brunetière","doi":"10.1115/1.4051141","DOIUrl":"https://doi.org/10.1115/1.4051141","url":null,"abstract":"\u0000 It is possible to levitate a mass by vibrating a flat disk located under the mass. This near-field acoustic levitation is particularly useful for eliminating friction between moving objects. This paper presents an experimental and theoretical study of the dynamic behavior of a levitating mass for different magnitudes of oscillation of the flat disk. The magnitude of the vibration of the mass appears to be independent of the amplitude of the vibration of the disk over a range of two orders of magnitude. This unusual behavior is due to the simultaneous changes of the stiffness of the air film and the natural frequency of the system as the plate vibration is changed. As the plate oscillation is reduced, the distance to resonance decreases, allowing an increase of the ratio of the output to input signals in such a way that the output remains constant. This result can be useful for improving the energy efficiency of the levitation.","PeriodicalId":327130,"journal":{"name":"ASME Letters in Dynamic Systems and Control","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134603806","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}
Sathish Vallachira, M. Norrlöf, M. Orkisz, S. Butail
In this paper, we cast the problem of fault isolation in industrial robots as that of causal analysis within coupled dynamical processes and evaluate the related efficacy of the information-theoretic approach of transfer entropy. To create a realistic and exhaustive dataset, we simulate wear-induced failure by increasing friction coefficient on select axes within an in-house robotic simulation tool that incorporates an elastic gearbox model. The source axis of failure is identified as one which has the highest net transfer entropy across all pairs of axes. In an exhaustive simulation study, we vary the friction successively in each axis across three common industrial tasks: pick and place, spot welding, and arc welding. Our results show that transfer entropy-based approach is able to detect the axis of failure more than 80% of the time when the friction coefficient is 5% above the nominal value and always when friction coefficient is 10% above the nominal value. The transfer entropy approach is more than twice as accurate as cross-correlation, a classical time series analysis used to identify directional dependence among processes.
{"title":"A Transfer Entropy Based Approach for Fault Isolation in Industrial Robots","authors":"Sathish Vallachira, M. Norrlöf, M. Orkisz, S. Butail","doi":"10.1115/1.4051565","DOIUrl":"https://doi.org/10.1115/1.4051565","url":null,"abstract":"\u0000 In this paper, we cast the problem of fault isolation in industrial robots as that of causal analysis within coupled dynamical processes and evaluate the related efficacy of the information-theoretic approach of transfer entropy. To create a realistic and exhaustive dataset, we simulate wear-induced failure by increasing friction coefficient on select axes within an in-house robotic simulation tool that incorporates an elastic gearbox model. The source axis of failure is identified as one which has the highest net transfer entropy across all pairs of axes. In an exhaustive simulation study, we vary the friction successively in each axis across three common industrial tasks: pick and place, spot welding, and arc welding. Our results show that transfer entropy-based approach is able to detect the axis of failure more than 80% of the time when the friction coefficient is 5% above the nominal value and always when friction coefficient is 10% above the nominal value. The transfer entropy approach is more than twice as accurate as cross-correlation, a classical time series analysis used to identify directional dependence among processes.","PeriodicalId":327130,"journal":{"name":"ASME Letters in Dynamic Systems and Control","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130638936","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}
As power demand across communities increases, focus has been given to the maintenance of power lines against harsh environments such as wind-induced vibration (WIV). Inspections robots and fixed vibration absorbers (FVAs) are the current solutions. However, both solutions are currently facing many challenges. Inspection robots are limited by their size and considerable power demand, while FVAs are narrowband and unable to adapt to changing wind characteristics, and thus are unable to reposition themselves at the antinodes of the vibrating loop. In view of these shortcomings, we propose a mobile damping robot (MDR) that integrates inspection robots mobility and FVAs WIV vibration control to help maintain power lines. In this effort, we model the conductor and the MDR by using Hamilton's principle and we consider the two-way nonlinear interaction between the MDR and the cable. The MDR is driven by a PD controller to the optimal vibration location (antinodes) as the wind characteristics vary. The numerical simulations suggest that the MDR outperforms FVAs for vibration mitigation. Furthermore, the key parameters that influence the performance of the MDR are identified through a parametric study. The findings could set up a platform to design a prototype and experimentally evaluate the performance of the MDR.
{"title":"Towards a Mobile Robot for Vibration Control and Inspection of Power Lines","authors":"Paul Kakou, O. Barry","doi":"10.1115/1.4050957","DOIUrl":"https://doi.org/10.1115/1.4050957","url":null,"abstract":"\u0000 As power demand across communities increases, focus has been given to the maintenance of power lines against harsh environments such as wind-induced vibration (WIV). Inspections robots and fixed vibration absorbers (FVAs) are the current solutions. However, both solutions are currently facing many challenges. Inspection robots are limited by their size and considerable power demand, while FVAs are narrowband and unable to adapt to changing wind characteristics, and thus are unable to reposition themselves at the antinodes of the vibrating loop. In view of these shortcomings, we propose a mobile damping robot (MDR) that integrates inspection robots mobility and FVAs WIV vibration control to help maintain power lines. In this effort, we model the conductor and the MDR by using Hamilton's principle and we consider the two-way nonlinear interaction between the MDR and the cable. The MDR is driven by a PD controller to the optimal vibration location (antinodes) as the wind characteristics vary. The numerical simulations suggest that the MDR outperforms FVAs for vibration mitigation. Furthermore, the key parameters that influence the performance of the MDR are identified through a parametric study. The findings could set up a platform to design a prototype and experimentally evaluate the performance of the MDR.","PeriodicalId":327130,"journal":{"name":"ASME Letters in Dynamic Systems and Control","volume":"228 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133612316","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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