In this paper, inspired by the geometric inversion transformation, a novel transformation of the z-plane root locus to a pseudo s-plane is proposed. In the z-plane, the stability of a discrete closed-loop system (a sampled-data control system) requires that all the system poles lie within the unit circle. In root locus analysis, the unit circle region seems congested, compared to the stability region of a continuous system, which is the left half of the s-plane. In the case of fast sampling, the poles of a discrete system can really be in a small neighborhood, thus making the control implementation difficult. The geometric transformation developed in this work helps widen or enlarge the space for the system poles and preserves most of the features of z-plane root loci, including marginal stability and root loci branching off at vertical angles. The usefulness of the new transformation in design of discrete control systems is demonstrated in a numerical example.
{"title":"A Pseudo S-Plane Mapping of Z-Plane Root Locus","authors":"Keyvan Noury, Bin Yang","doi":"10.1115/IMECE2020-23096","DOIUrl":"https://doi.org/10.1115/IMECE2020-23096","url":null,"abstract":"\u0000 In this paper, inspired by the geometric inversion transformation, a novel transformation of the z-plane root locus to a pseudo s-plane is proposed. In the z-plane, the stability of a discrete closed-loop system (a sampled-data control system) requires that all the system poles lie within the unit circle. In root locus analysis, the unit circle region seems congested, compared to the stability region of a continuous system, which is the left half of the s-plane. In the case of fast sampling, the poles of a discrete system can really be in a small neighborhood, thus making the control implementation difficult. The geometric transformation developed in this work helps widen or enlarge the space for the system poles and preserves most of the features of z-plane root loci, including marginal stability and root loci branching off at vertical angles. The usefulness of the new transformation in design of discrete control systems is demonstrated in a numerical example.","PeriodicalId":23585,"journal":{"name":"Volume 7A: Dynamics, Vibration, and Control","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76486075","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 present study attempts to capture the fluid-structure interaction dynamics of a chord-wise flexible flapping wing system using a limited mode structural model coupled with a high-fidelity Navier-Stokes (N-S) solver. The wing is modeled as two elliptic rigid foils connected by a non-linear torsional spring that incorporates the chord-wise bending stiffness. The front link is subjected to an active pitching-plunging motion while the rear link undergoes flow-induced passive oscillation. The structural governing equation for the rear link takes the form of a Duffing equation subjected to base excitation and external aerodynamic forcing. The aerodynamic loads on the foil are computed using a discrete forcing Immersed Boundary Method based in-house N-S solver which is coupled with the structural solver by a staggered weak coupling strategy. A bifurcation study is performed considering the free-stream velocity as the control parameter, in the presence of both structural and aerodynamic non-linearities. A dynamical transition in the unsteady flow-field from a periodic reverse-Kármán wake to an aperiodic wake is observed as the flow parameters are varied. The same transition is also reflected in the passive oscillation of the rear foil when analyzed with tools from the dynamical systems theory.
{"title":"Nonlinear Fluid-Elastic Behavior of a Flapping Wing With Low-Order Chord-Wise Flexibility","authors":"Dipanjan Majumdar, Chandan Bose, Sunetra Sarkar","doi":"10.1115/IMECE2020-23890","DOIUrl":"https://doi.org/10.1115/IMECE2020-23890","url":null,"abstract":"\u0000 The present study attempts to capture the fluid-structure interaction dynamics of a chord-wise flexible flapping wing system using a limited mode structural model coupled with a high-fidelity Navier-Stokes (N-S) solver. The wing is modeled as two elliptic rigid foils connected by a non-linear torsional spring that incorporates the chord-wise bending stiffness. The front link is subjected to an active pitching-plunging motion while the rear link undergoes flow-induced passive oscillation. The structural governing equation for the rear link takes the form of a Duffing equation subjected to base excitation and external aerodynamic forcing. The aerodynamic loads on the foil are computed using a discrete forcing Immersed Boundary Method based in-house N-S solver which is coupled with the structural solver by a staggered weak coupling strategy. A bifurcation study is performed considering the free-stream velocity as the control parameter, in the presence of both structural and aerodynamic non-linearities. A dynamical transition in the unsteady flow-field from a periodic reverse-Kármán wake to an aperiodic wake is observed as the flow parameters are varied. The same transition is also reflected in the passive oscillation of the rear foil when analyzed with tools from the dynamical systems theory.","PeriodicalId":23585,"journal":{"name":"Volume 7A: Dynamics, Vibration, and Control","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77811486","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}
Specific satellites with ultra-long wings play a crucial role in many fields. However, external disturbance and self-rotation could result in undesired vibrations of flexible wings, which affects the normal operation of the satellites. In severe cases, the satellites will be damaged. Therefore, it is imperative to conduct vibration suppression for these flexible structures. Utilizing deep reinforcement learning (DRL), an active control scheme is presented in this paper to rapidly suppress the vibration of flexible structures with quite small controllable force based on a cable-driven parallel robot (CDPR). To verify the controller’s effectiveness, three groups of simulation with different initial disturbance are implemented. Besides, to enhance the contrast, a passive pre-tightening scheme is also tested. First, the dynamic model of the CDPR that is comprised of four cables and a flexible structure is established using the finite element method. Then, the dynamic behavior of the model under the controllable cable force is analyzed by Newmark-ß method. Furthermore, the agent of DRL is trained by the deep deterministic policy gradient algorithm (DDPG). Finally, the control scheme is conducted on Simulink environment to evaluate its performance, and the results are satisfactory, which validates the controller’s ability to suppress vibrations.
{"title":"Vibration Suppression for Large-Scale Flexible Structures Using Deep Reinforcement Learning Based on Cable-Driven Parallel Robots","authors":"Haining Sun, Xiaoqiang Tang, Wei Jinhao","doi":"10.1115/IMECE2020-23259","DOIUrl":"https://doi.org/10.1115/IMECE2020-23259","url":null,"abstract":"\u0000 Specific satellites with ultra-long wings play a crucial role in many fields. However, external disturbance and self-rotation could result in undesired vibrations of flexible wings, which affects the normal operation of the satellites. In severe cases, the satellites will be damaged. Therefore, it is imperative to conduct vibration suppression for these flexible structures. Utilizing deep reinforcement learning (DRL), an active control scheme is presented in this paper to rapidly suppress the vibration of flexible structures with quite small controllable force based on a cable-driven parallel robot (CDPR). To verify the controller’s effectiveness, three groups of simulation with different initial disturbance are implemented. Besides, to enhance the contrast, a passive pre-tightening scheme is also tested. First, the dynamic model of the CDPR that is comprised of four cables and a flexible structure is established using the finite element method. Then, the dynamic behavior of the model under the controllable cable force is analyzed by Newmark-ß method. Furthermore, the agent of DRL is trained by the deep deterministic policy gradient algorithm (DDPG). Finally, the control scheme is conducted on Simulink environment to evaluate its performance, and the results are satisfactory, which validates the controller’s ability to suppress vibrations.","PeriodicalId":23585,"journal":{"name":"Volume 7A: Dynamics, Vibration, and Control","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74147829","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}
A. Porter, J. Alhamid, C. Mo, John H. Miller, J. Iannelli, M. Honegger, L. Lichtensteiger
The newly designed 3-dimensional catching robot consists of three revolute joints where the forward linkage is a parallelogram mechanism for keeping the catching end-effector parallel to the picking manipulator’s base. A virtual apple field of 505 apples, designed to test the picking abilities of 7 DOF arm, was used to determine the capabilities of this new catching arm design. The target catching efficiency was 90% for the provided virtual apple field with a maximum drop height of 30 cm. The target coordinates for each virtual apple were found by computer simulation in MATLAB. Geometric parameters were selected such that the catching manipulator could reach every possible drop position in the picking manipulator’s workspace. The design was completed, fabricated, and validated, utilizing the elegant mechanical linkage design. The workspace analysis showed that it had an acceptable 93% catching efficiency, and as the drop height increased, the efficiency approaches 100%. Definitive inverse-kinematics provided exact joint angles required to catch all catchable apples inside of the workspace. Using these angles, the general equation of motion, using Lagrangian mechanics, yielded the required torque outputs of each of the three motors on the arm. Validation of these torques through laboratory experimentation was considered adequate.
{"title":"Analysis and Design of an Auxiliary Catching Arm for an Apple Picking Robot","authors":"A. Porter, J. Alhamid, C. Mo, John H. Miller, J. Iannelli, M. Honegger, L. Lichtensteiger","doi":"10.1115/IMECE2020-23570","DOIUrl":"https://doi.org/10.1115/IMECE2020-23570","url":null,"abstract":"\u0000 The newly designed 3-dimensional catching robot consists of three revolute joints where the forward linkage is a parallelogram mechanism for keeping the catching end-effector parallel to the picking manipulator’s base. A virtual apple field of 505 apples, designed to test the picking abilities of 7 DOF arm, was used to determine the capabilities of this new catching arm design. The target catching efficiency was 90% for the provided virtual apple field with a maximum drop height of 30 cm. The target coordinates for each virtual apple were found by computer simulation in MATLAB. Geometric parameters were selected such that the catching manipulator could reach every possible drop position in the picking manipulator’s workspace. The design was completed, fabricated, and validated, utilizing the elegant mechanical linkage design. The workspace analysis showed that it had an acceptable 93% catching efficiency, and as the drop height increased, the efficiency approaches 100%. Definitive inverse-kinematics provided exact joint angles required to catch all catchable apples inside of the workspace. Using these angles, the general equation of motion, using Lagrangian mechanics, yielded the required torque outputs of each of the three motors on the arm. Validation of these torques through laboratory experimentation was considered adequate.","PeriodicalId":23585,"journal":{"name":"Volume 7A: Dynamics, Vibration, and Control","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82576016","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 study examines implementation of a Model Predictive Controller (MPC) to a new concept in active suspension design. Active and passive components are placed in series to mitigate both high and low frequency disturbance inputs at the tire-road interface. This is modelled using an additional mass spring damper tuned to regulate high frequency inputs, leaving the active components to respond to low frequency inputs. A generic half car model for such a system is developed and subjected to various disturbance inputs at constant velocity and output to verify the system dynamics. Inputs include step, multimodal, and random disturbances as well as a step input that returns to zero. These trials serve as a baseline to evaluate the performance of the passive suspension as well as a Model Predictive Controller. Current research that uses MPC in active suspension design focuses heavily on the traditional half car model with 4 DOF[4]. MPC is applied to this new 6 DOF model and incorporates preview information into the controller response for each of the test cases. The cost function for the MPC places penalties on the translational and rotational position and velocity of the chassis relative to a reference state that is based on each disturbance profile. Parameters of interest are driver absorbed power due to both linear and rotational movement of the chassis. The results for each test case demonstrate the utility of MPC. For every response, there is a decrease in the absorbed power due to rotational and linear sources on the magnitude of 98–100%. The incorporation of preview information also removed the rotation of the chassis for each test case by placing a heavy weight upon its movement. For the step input, the controller reduced the peak rate of change of the chassis by 71.4%. For the multi-mode input, the low frequency sinusoidal inputs showed a dramatic reduction in vertical displacement in the steady state behavior as the MPC will produce an output that is tuned to cancel the disturbance. The high frequency effects are also effectively removed by the passive components of the suspension. This ability to mitigate both sources of disturbance is a marked advantage of the double-stacked suspension design. MPC allowed for the overall reduction of chassis movement by 54.0% with preview information. This improvement is due to the ability of the double stacked suspension with MPC to use the additional degrees of freedom to attenuate disturbances at more than one frequency. The random input demonstrates the ability of the controller to maintain a smooth chassis trajectory even with a chaotic road profile. Finally, the step up-down input demonstrates the ability of the controller to use other components of the suspension system to mitigate a disturbance in order to keep the chassis stable. These results demonstrate that preview information can be used to take full advantage of double stacked, active suspensions and further enhance mobility over different k
{"title":"Model Predictive Control of Double Stacked Suspension System","authors":"Nathan Batta, D. Doscher","doi":"10.1115/IMECE2020-23569","DOIUrl":"https://doi.org/10.1115/IMECE2020-23569","url":null,"abstract":"\u0000 This study examines implementation of a Model Predictive Controller (MPC) to a new concept in active suspension design. Active and passive components are placed in series to mitigate both high and low frequency disturbance inputs at the tire-road interface. This is modelled using an additional mass spring damper tuned to regulate high frequency inputs, leaving the active components to respond to low frequency inputs. A generic half car model for such a system is developed and subjected to various disturbance inputs at constant velocity and output to verify the system dynamics. Inputs include step, multimodal, and random disturbances as well as a step input that returns to zero. These trials serve as a baseline to evaluate the performance of the passive suspension as well as a Model Predictive Controller. Current research that uses MPC in active suspension design focuses heavily on the traditional half car model with 4 DOF[4]. MPC is applied to this new 6 DOF model and incorporates preview information into the controller response for each of the test cases. The cost function for the MPC places penalties on the translational and rotational position and velocity of the chassis relative to a reference state that is based on each disturbance profile. Parameters of interest are driver absorbed power due to both linear and rotational movement of the chassis. The results for each test case demonstrate the utility of MPC. For every response, there is a decrease in the absorbed power due to rotational and linear sources on the magnitude of 98–100%. The incorporation of preview information also removed the rotation of the chassis for each test case by placing a heavy weight upon its movement. For the step input, the controller reduced the peak rate of change of the chassis by 71.4%. For the multi-mode input, the low frequency sinusoidal inputs showed a dramatic reduction in vertical displacement in the steady state behavior as the MPC will produce an output that is tuned to cancel the disturbance. The high frequency effects are also effectively removed by the passive components of the suspension. This ability to mitigate both sources of disturbance is a marked advantage of the double-stacked suspension design. MPC allowed for the overall reduction of chassis movement by 54.0% with preview information. This improvement is due to the ability of the double stacked suspension with MPC to use the additional degrees of freedom to attenuate disturbances at more than one frequency. The random input demonstrates the ability of the controller to maintain a smooth chassis trajectory even with a chaotic road profile. Finally, the step up-down input demonstrates the ability of the controller to use other components of the suspension system to mitigate a disturbance in order to keep the chassis stable. These results demonstrate that preview information can be used to take full advantage of double stacked, active suspensions and further enhance mobility over different k","PeriodicalId":23585,"journal":{"name":"Volume 7A: Dynamics, Vibration, and Control","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81790261","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}
Linear infinite dimensional systems are described by a closed, densely defined linear operator that generates a continuous semigroup of bounded operators on a general Hilbert space of states and are controlled via a finite number of actuators and sensors. Many distributed applications are included in this formulation, such as large flexible aerospace structures, adaptive optics, diffusion reactions, smart electric power grids, and quantum information systems. In this paper, we focus on infinite dimensional linear systems for which a fixed gain linear infinite or finite dimensional controller is already in place. We augment this controller with a direct adaptive controller that will maintain stability of the full closed loop system even when the fixed gain controller fails to do so. We prove that the transmission zeros of the combined system are the original open loop transmission zeros, and the point spectrum of the controller alone. Therefore, the combined plant plus controller is Almost Strictly Dissipative (ASD) if and only if the original open loop system is minimum phase, and the fixed gain controller alone is exponentially stable. This result is true whether the fixed gain controller is finite or infinite dimensional. In particular this guarantees that a controller for an infinite dimensional plant based on a reduced -order approximation can be stabilized by augmentation with direct adaptive control to mitigate risks. These results are illustrated by application to direct adaptive control of general linear diffusion systems on a Hilbert space that are described by self-adjoint operators with compact resolvent.
{"title":"Augmentation of Fixed Gain Controlled Infinite Dimensional Systems With Direct Adaptive Control","authors":"M. Balas","doi":"10.1115/IMECE2020-23179","DOIUrl":"https://doi.org/10.1115/IMECE2020-23179","url":null,"abstract":"\u0000 Linear infinite dimensional systems are described by a closed, densely defined linear operator that generates a continuous semigroup of bounded operators on a general Hilbert space of states and are controlled via a finite number of actuators and sensors. Many distributed applications are included in this formulation, such as large flexible aerospace structures, adaptive optics, diffusion reactions, smart electric power grids, and quantum information systems.\u0000 In this paper, we focus on infinite dimensional linear systems for which a fixed gain linear infinite or finite dimensional controller is already in place. We augment this controller with a direct adaptive controller that will maintain stability of the full closed loop system even when the fixed gain controller fails to do so. We prove that the transmission zeros of the combined system are the original open loop transmission zeros, and the point spectrum of the controller alone. Therefore, the combined plant plus controller is Almost Strictly Dissipative (ASD) if and only if the original open loop system is minimum phase, and the fixed gain controller alone is exponentially stable. This result is true whether the fixed gain controller is finite or infinite dimensional. In particular this guarantees that a controller for an infinite dimensional plant based on a reduced -order approximation can be stabilized by augmentation with direct adaptive control to mitigate risks.\u0000 These results are illustrated by application to direct adaptive control of general linear diffusion systems on a Hilbert space that are described by self-adjoint operators with compact resolvent.","PeriodicalId":23585,"journal":{"name":"Volume 7A: Dynamics, Vibration, and Control","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73529003","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}
Kyle Norvell, M. Mcclelland, Ethan Ratajczak, Janet Dong
The work in this paper is a part of the T-shirt cannon automation project. The objective of the project is to develop an autonomous robot carrying cannons to automatically shoot T-shirts during the sports events at the University of Cincinnati (UC). More specifically, the T-shirt cannon will be used and driven by the UC cheerleading team and be able to automatically shoot T-shirts at the audience in the Nippert Stadium and the 5/3 Arena for football and basketball games, respectively. The design and automation of the T-shirt cannon require a significant effort and a multi-disciplinary team to complete. This paper will focus on the process of designing, building, and testing the firing mechanism for the cannon, including the determination of cannon’s firing method, barrel design and assembly, base design and barrel mounting method, pneumatic analysis, and automation and control of the firing of T-shirts. The goal of the firing mechanism is that the cannon would fire off as many T-shirts as possible with the window of a single timeout at the game. The project starts with the preliminary research and the initial testing. During the preliminary research, the relevant safety standards/codes and previous T-shirt cannon designs were reviewed and studied. Especially the possible working with pressurized air, the material used in the design must be rated above the target firing pressure to ensure the cannon itself not explode and the air supply tank and fittings must be in good condition. During the initial testing, the site visits were conducted, the cheerleaders were interviewed, the dimensions of the stadium and the 5/3 arena were measured, and therefore the shooting distance and shooting angles were estimated. After the initial testing and preliminary research, a set of engineering characteristics were established, following by the concept design, in which the barrel assembly, the pneumatics, the firing mechanism, and the mounting method were discussed, analyzed, and determined. The barrels had two major designs, one is using a railing support system with an external tank of air to power and fire the cannon, and another one is using a chamber of air to power and fire the cannon with the barrels surrounding the air chamber itself. Two methods are analyzed and compared. The optimum one, therefore, was determined and developed. For the firing mechanism, two main designs are a spring-loaded firing mechanism that could increase the sealing capabilities of the barrels, and a tight tolerance fit that has less weight. Two designs were tested and analyzed, the optimum one was determined and built, followed by the firing mechanism testing. This paper will describe the process of design, building, and testing the firing mechanisms of this T-shirt cannon at UC. The paper will also discuss the testing results on shooting performance.
{"title":"Design and Build a T-Shirt Cannon Firing Mechanism","authors":"Kyle Norvell, M. Mcclelland, Ethan Ratajczak, Janet Dong","doi":"10.1115/IMECE2020-24112","DOIUrl":"https://doi.org/10.1115/IMECE2020-24112","url":null,"abstract":"\u0000 The work in this paper is a part of the T-shirt cannon automation project. The objective of the project is to develop an autonomous robot carrying cannons to automatically shoot T-shirts during the sports events at the University of Cincinnati (UC). More specifically, the T-shirt cannon will be used and driven by the UC cheerleading team and be able to automatically shoot T-shirts at the audience in the Nippert Stadium and the 5/3 Arena for football and basketball games, respectively. The design and automation of the T-shirt cannon require a significant effort and a multi-disciplinary team to complete. This paper will focus on the process of designing, building, and testing the firing mechanism for the cannon, including the determination of cannon’s firing method, barrel design and assembly, base design and barrel mounting method, pneumatic analysis, and automation and control of the firing of T-shirts. The goal of the firing mechanism is that the cannon would fire off as many T-shirts as possible with the window of a single timeout at the game.\u0000 The project starts with the preliminary research and the initial testing. During the preliminary research, the relevant safety standards/codes and previous T-shirt cannon designs were reviewed and studied. Especially the possible working with pressurized air, the material used in the design must be rated above the target firing pressure to ensure the cannon itself not explode and the air supply tank and fittings must be in good condition. During the initial testing, the site visits were conducted, the cheerleaders were interviewed, the dimensions of the stadium and the 5/3 arena were measured, and therefore the shooting distance and shooting angles were estimated. After the initial testing and preliminary research, a set of engineering characteristics were established, following by the concept design, in which the barrel assembly, the pneumatics, the firing mechanism, and the mounting method were discussed, analyzed, and determined. The barrels had two major designs, one is using a railing support system with an external tank of air to power and fire the cannon, and another one is using a chamber of air to power and fire the cannon with the barrels surrounding the air chamber itself. Two methods are analyzed and compared. The optimum one, therefore, was determined and developed. For the firing mechanism, two main designs are a spring-loaded firing mechanism that could increase the sealing capabilities of the barrels, and a tight tolerance fit that has less weight. Two designs were tested and analyzed, the optimum one was determined and built, followed by the firing mechanism testing.\u0000 This paper will describe the process of design, building, and testing the firing mechanisms of this T-shirt cannon at UC. The paper will also discuss the testing results on shooting performance.","PeriodicalId":23585,"journal":{"name":"Volume 7A: Dynamics, Vibration, and Control","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86142461","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}
Fourat Zribi, L. Sidhom, Mohamed Gharib, S. Refaat, A. Mami
Drill strings are complex dynamical systems with many uncertain parameters. The drill string interaction with the borehole produces a variety of undesired oscillations. The stickslip phenomenon is the extreme state of torsional vibrations, which causes the drill string to stop rotating and then spin free periodically. This non-uniform rotation may cause the wear of expensive equipment or even catastrophic failures in drill strings. Therefore, it is essential to study the drilling parameters in order to develop appropriate control approach for the suppression of the stick-slip vibration. However, the complexity of the drill string system poses several modeling and control challenges. The drill string model challenges include thermal, physical, electrical, and environmental influences on the stick-slip, simple enough to perform the analysis and control purposes. The control challenges include dealing with the complex dynamics of nonlinear friction, minimize nonlinear torque on the bit, and perform more robust during operating conditions. The control techniques are divided into two major approaches: passive and active control approaches. The passive control approaches include design sophisticated bits (with depth of cut control technology) to limit the reactive torque that might lead to the stick-slip, optimizing the drilling parameters, and using antivibration down hole tools. The active control approaches are on active anti-vibration control methods due to the improvements in the real-time measurement and control systems. Two of the most common active control techniques used in drill string system are proportional-derivative and sliding mode control methods. This paper presents an overview and a comparative study of the common control methods belonging to the common active control methods to mitigate the stick-slip phenomenon in drill string systems. The main objective is to assess the impact of the active control approaches to mitigate the stick-slip phenomenon. First, the common model for drillstring system is presented. Then, the study presents analyses of different drilling parameters, such as the weight on bit (WOB) and associated torque on bit (TOB) that define the bit aggressiveness, which are key in mitigating stick-slip vibration. These parameters have been considered as the comparison factors. Furthermore, this study details the design process of these controllers, and evaluates the performances of the different control systems to track the reference signal of bit velocity taking into account parametric uncertainties. Discussion and recommendation about the drilling parameters optimization are presented. This paper provides the necessary information needed for modeling and control of drillstring systems with minimum stick-slip vibrations. The results show that the adaptive sliding mode controller succeeded to eliminate the stick-slip phenomenon with better robustness to parametric uncertainties and weight on bit variations compared to
{"title":"A Comparative Study of Active Control Methods for Mitigation of Torsional Stick-Slip Vibrations in Drillstring Systems","authors":"Fourat Zribi, L. Sidhom, Mohamed Gharib, S. Refaat, A. Mami","doi":"10.1115/IMECE2020-23551","DOIUrl":"https://doi.org/10.1115/IMECE2020-23551","url":null,"abstract":"\u0000 Drill strings are complex dynamical systems with many uncertain parameters. The drill string interaction with the borehole produces a variety of undesired oscillations. The stickslip phenomenon is the extreme state of torsional vibrations, which causes the drill string to stop rotating and then spin free periodically. This non-uniform rotation may cause the wear of expensive equipment or even catastrophic failures in drill strings. Therefore, it is essential to study the drilling parameters in order to develop appropriate control approach for the suppression of the stick-slip vibration. However, the complexity of the drill string system poses several modeling and control challenges. The drill string model challenges include thermal, physical, electrical, and environmental influences on the stick-slip, simple enough to perform the analysis and control purposes. The control challenges include dealing with the complex dynamics of nonlinear friction, minimize nonlinear torque on the bit, and perform more robust during operating conditions. The control techniques are divided into two major approaches: passive and active control approaches. The passive control approaches include design sophisticated bits (with depth of cut control technology) to limit the reactive torque that might lead to the stick-slip, optimizing the drilling parameters, and using antivibration down hole tools. The active control approaches are on active anti-vibration control methods due to the improvements in the real-time measurement and control systems. Two of the most common active control techniques used in drill string system are proportional-derivative and sliding mode control methods.\u0000 This paper presents an overview and a comparative study of the common control methods belonging to the common active control methods to mitigate the stick-slip phenomenon in drill string systems. The main objective is to assess the impact of the active control approaches to mitigate the stick-slip phenomenon. First, the common model for drillstring system is presented. Then, the study presents analyses of different drilling parameters, such as the weight on bit (WOB) and associated torque on bit (TOB) that define the bit aggressiveness, which are key in mitigating stick-slip vibration. These parameters have been considered as the comparison factors. Furthermore, this study details the design process of these controllers, and evaluates the performances of the different control systems to track the reference signal of bit velocity taking into account parametric uncertainties. Discussion and recommendation about the drilling parameters optimization are presented. This paper provides the necessary information needed for modeling and control of drillstring systems with minimum stick-slip vibrations. The results show that the adaptive sliding mode controller succeeded to eliminate the stick-slip phenomenon with better robustness to parametric uncertainties and weight on bit variations compared to","PeriodicalId":23585,"journal":{"name":"Volume 7A: Dynamics, Vibration, and Control","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84856395","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}
High speed rotating machineries usually operate under severe conditions and enormous loadings and thus, are susceptible to several problems. One such problem that has caught the attention in recent decades is known as High Cycle Fatigue. More than 60 percent of rotating machinery failures has been attributed to this High cycle Fatigue. Along with High Cycle Fatigue, Vibration, an inherent phenomenon in machineries, also share its part in failure of rotating machineries. Rotating machinery components suffer from high amplitude vibrations when they pass through resonance. Stresses are developed as a result of these vibrations and fatigue in mechanical structures, providing a conducive environment for the development of cracks at Surface. When these surface cracks reach critical size, crack nucleation starts, which ultimately leads to catastrophic failures. So, in order to avoid the disastrous consequences, damping is needed. Damping keeps material’s integrity in case of impact forces, stresses due to thermal shocks in turbo machinery and earth quakes in huge structures. Thin layer of magneto elastic coating can be applied on substrate surface that acts as first line of defense. Large number of coating Processes are available around the globe. The optimized combination of coating material, substrate material and coating technique according to specific application is necessary. These coatings have the capability to combat the phenomenon of oxidation, wear and fatigue acting as a barrier between substrate and hostile environments. Further, they enhance the damping characteristics, and thus allows the highspeed rotating machinery to reach its operational speed without any failure at resonance. In this way, they not only enhance the performance of components in aggressive environments, but also improve the life cycle, saving assets of millions of dollars’ worth. This research is an endeavor to experimentally investigate effect of magneto mechanical coating on damping of AISI 321 Stainless steel. AISI 321 was selected as base material because of its wide applications in engine components of gas turbines, heat exchangers and in different chemical industries. Two types of Air plasma sprayed magneto-mechanical powder (NiAl & CoNiCrAlY) were coated on base material and thickness was maintained up to 250μm in both the cases. Experiments were designed and performed on cantilever beam specimens for dynamic response measurement. Dynamic response of the system was measured to investigate the modal parameters of natural frequencies, damping ratio and time of vibration decay. For damping ratio, vibration analyzer mode was adjusted in time domain and beam was excited by using a hammer. Vibration analyzer showed the vibration decay as a function of time. Logarithmic decrement method was used to calculate the damping ratio in both cases. Dynamic response of all the three cases (NiAl coating, CoNiCrAlY and uncoated AISI321) were compared. Results were very reassuring
{"title":"Experimental Investigation of Vibration Damping Behavior of Magneto-Mechanical Coated AISI321 Stainless-Steel","authors":"H. M. Ashraf, Farhan Ali","doi":"10.1115/imece2019-11312","DOIUrl":"https://doi.org/10.1115/imece2019-11312","url":null,"abstract":"\u0000 High speed rotating machineries usually operate under severe conditions and enormous loadings and thus, are susceptible to several problems. One such problem that has caught the attention in recent decades is known as High Cycle Fatigue. More than 60 percent of rotating machinery failures has been attributed to this High cycle Fatigue. Along with High Cycle Fatigue, Vibration, an inherent phenomenon in machineries, also share its part in failure of rotating machineries. Rotating machinery components suffer from high amplitude vibrations when they pass through resonance. Stresses are developed as a result of these vibrations and fatigue in mechanical structures, providing a conducive environment for the development of cracks at Surface. When these surface cracks reach critical size, crack nucleation starts, which ultimately leads to catastrophic failures. So, in order to avoid the disastrous consequences, damping is needed. Damping keeps material’s integrity in case of impact forces, stresses due to thermal shocks in turbo machinery and earth quakes in huge structures. Thin layer of magneto elastic coating can be applied on substrate surface that acts as first line of defense. Large number of coating Processes are available around the globe. The optimized combination of coating material, substrate material and coating technique according to specific application is necessary. These coatings have the capability to combat the phenomenon of oxidation, wear and fatigue acting as a barrier between substrate and hostile environments. Further, they enhance the damping characteristics, and thus allows the highspeed rotating machinery to reach its operational speed without any failure at resonance. In this way, they not only enhance the performance of components in aggressive environments, but also improve the life cycle, saving assets of millions of dollars’ worth. This research is an endeavor to experimentally investigate effect of magneto mechanical coating on damping of AISI 321 Stainless steel. AISI 321 was selected as base material because of its wide applications in engine components of gas turbines, heat exchangers and in different chemical industries. Two types of Air plasma sprayed magneto-mechanical powder (NiAl & CoNiCrAlY) were coated on base material and thickness was maintained up to 250μm in both the cases. Experiments were designed and performed on cantilever beam specimens for dynamic response measurement. Dynamic response of the system was measured to investigate the modal parameters of natural frequencies, damping ratio and time of vibration decay. For damping ratio, vibration analyzer mode was adjusted in time domain and beam was excited by using a hammer. Vibration analyzer showed the vibration decay as a function of time. Logarithmic decrement method was used to calculate the damping ratio in both cases. Dynamic response of all the three cases (NiAl coating, CoNiCrAlY and uncoated AISI321) were compared. Results were very reassuring","PeriodicalId":23585,"journal":{"name":"Volume 7A: Dynamics, Vibration, and Control","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72850152","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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