scholarly journals Effect of End-Effector Compliance on Collisions in Robotic Teleoperation

2020 ◽  
Vol 10 (24) ◽  
pp. 9077
Author(s):  
Domenico Tommasino ◽  
Giulio Cipriani ◽  
Alberto Doria ◽  
Giulio Rosati
Keyword(s):  
Mathematical Model ◽  
Elastic System ◽  
Contact Stiffness ◽  
End Effector ◽  
Stable Mechanism ◽  
Stiffness And Damping ◽  
And Control ◽  
The Impact ◽  
Robotic Teleoperation ◽  
Mechanical Decoupling

In robotic teleoperation, hard impacts between a tool and the manipulated object may impair the success of a task. In order to develop a robotic system that is able to minimize the final velocity of an object after impact, a comprehensive approach is adopted in this work, and the effect on the impact of the parameters of the tool and of the robot is studied. Mass, contact stiffness and damping, robot compliance and control and tool compliance are taken into account. A mathematical model including the tool and the robot moving along the approach direction shows that, in most conditions, robot compliance is not enough to mitigate the impact. A mechanical decoupling between the inertia of the tool and the inertia of the robot is needed. An elastic system based on a bi-stable mechanism is developed and its validity is shown by means of numerical simulations.

Development of an End-Effector for Mitigation of Collisions

2021 ◽  
Author(s):  
Domenico Tommasino ◽  
Matteo Bottin ◽  
Giulio Cipriani ◽  
Alberto Doria ◽  
Giulio Rosati
Keyword(s):  
Numerical Simulations ◽  
Industrial Applications ◽  
Operating Conditions ◽  
Contact Forces ◽  
Design Parameters ◽  
End Effector ◽  
Linear Behavior ◽  
Stable Mechanism ◽  
Robot Tasks ◽  
The Impact

Abstract In robotics the risk of collisions is present both in industrial applications and in remote handling. If a collision occurs, the impact may damage both the robot and external equipment, which may result in successive imprecise robot tasks or line stops, reducing robot efficiency. As a result, appropriate collision avoidance algorithms should be used or, if it is not possible, the robot must be able to react to impacts reducing the contact forces. For this purpose, this paper focuses on the development of a special end-effector that can withstand impacts and is able to protect the robot from impulsive forces. The novel end-effector is based on a bi-stable mechanism that decouples the dynamics of the end-effector from the dynamics of the robot. The intrinsically non-linear behavior of the end-effector is investigated with the aid of numerical simulations. The effect of design parameters and the operating conditions are analyzed and the interaction between the functioning of the bi-stable mechanism and the control system is studied. In particular, the effect of the mechanism in different scenarios characterized by different robot velocities is shown. Results of numerical simulations assess the validity of the proposed end-effector, which can lead to large reductions in impact forces.

scholarly journals Predicting the evolution and control of the COVID-19 pandemic in Portugal

F1000Research ◽  
2020 ◽  
Vol 9 ◽  
pp. 283 ◽  
Author(s):  
Ricardo J. Pais ◽  
Nuno Taveira
Keyword(s):  
Mathematical Model ◽  
Exponential Growth ◽  
Hospital Care ◽  
Effective Control ◽  
Social Distancing ◽  
And Control ◽  
The Impact

Coronavirus disease 2019 (COVID-19) is a worldwide pandemic that has been affecting Portugal since 2 March 2020. The Portuguese government has been making efforts to contradict the exponential growth through lockdown, social distancing and the usage of masks. However, these measures have been implemented without controlling the compliance degree and how much is necessary to achieve an effective control. To address this issue, we developed a mathematical model to estimate the strength of Government-Imposed Measures (GIM) and predict the impact of the degree of compliance on the number of infected cases and peak of infection. We estimate the peak to be around 650 thousand infected cases with 53 thousand requiring hospital care by the beginning of May if no measures were taken. The model shows that the population compliance of the GIM was gradual between   30% to 75%, contributing to a significant reduction on the infection peak and mortality. Importantly, our simulations show that the infection burden could have been further reduced if the population followed the GIM immediately after their release on 18 March.

Modeling and Control of a Cable-Driven Robot for Inspection of Wide-Area Horizontal Workspaces

2016 ◽  
Author(s):  
Forrest Montgomery ◽  
Joshua Vaughan
Keyword(s):  
Parallel Manipulator ◽  
Large Scale ◽  
Parallel Manipulators ◽  
End Effector ◽  
Modeling And Control ◽  
Oscillatory Dynamics ◽  
Flexible Wire ◽  
Length Changes ◽  
Stiffness And Damping ◽  
And Control

Cable Driven Parallel Manipulators (CDPMs) utilize flexible wire to actuate an end-effector, allowing rapid accelerations across large workspaces. CDPMs are predominantly modeled with rigid cables, greatly simplifying the analysis. This model is satisfactory for small, fixed masses traveling short distances. However, as cable length increases, the flexibility of the cables, including the variation in stiffness and damping as length changes, cannot be ignored. In addition, the end-effector, which may be modeled as a pendulum, will rotate and contribute to the motion. This paper presents the modeling and control of a large-scale, cable-driven parallel manipulator, with application to inspection of large workspaces. The multi-degree-of-freedom model developed takes into account flexibility of cables and the oscillatory dynamics of the end effector. The dominant dynamics are identified and used to design a control system to limit vibration.

Development and validation of an end-effector for mitigation of collisions

2021 ◽  
pp. 1-33
Author(s):  
Domenico Tommasino ◽  
Matteo Bottin ◽  
Giulio Cipriani ◽  
Alberto Doria ◽  
Giulio Rosati
Keyword(s):  
Numerical Simulations ◽  
Industrial Applications ◽  
Operating Conditions ◽  
Contact Forces ◽  
Design Parameters ◽  
End Effector ◽  
Linear Behavior ◽  
Stable Mechanism ◽  
Robot Tasks ◽  
The Impact

Abstract In robotics the risk of collisions is present both in industrial applications and in remote handling. If a collision occurs, the impact may damage both the robot and external equipment, which may result in successive imprecise robot tasks or line stops, reducing robot efficiency. As a result, appropriate collision avoidance algorithms should be used or, if it is not possible, the robot must be able to react to impacts reducing the contact forces. For this purpose, this paper focuses on the development of a special end-effector that can withstand impacts. It is able to protect the robot from impulsive forces caused by collisions of the end-effector, but it has no effect on possible collisions between the links and obstacles. The novel end-effector is based on a bi-stable mechanism that decouples the dynamics of the end-effector from the dynamics of the robot. The intrinsically non-linear behavior of the endeffector is investigated with the aid of numerical simulations. The effect of design parameters and operating conditions are analyzed and the interaction between the functioning of the bi-stable mechanism and the control system is studied. In particular, the effect of the mechanism in different scenarios characterized by different robot velocities is shown. Results of numerical simulations assess the validity of the proposed end-effector, which can lead to large reductions in impact forces. Numerical results are validated by means of specific laboratory tests.

scholarly journals Predicting the evolution and control of the COVID-19 pandemic in Portugal

F1000Research ◽  
2020 ◽  
Vol 9 ◽  
pp. 283 ◽  
Author(s):  
Ricardo J. Pais ◽  
Nuno Taveira
Keyword(s):  
Mathematical Model ◽  
Social Isolation ◽  
Exponential Growth ◽  
And Control ◽  
The Impact

Coronavirus disease 2019 (COVID-19) is a worldwide pandemic that has been affecting Portugal since 2 March 2020. The Portuguese government has been making efforts to contradict the exponential growth through social isolation measures. We have developed a mathematical model to predict the impact of such measures in the number of infected cases and peak of infection. We estimate the peak to be around 2 million infected cases by the beginning of May if no additional measures are taken. The model shows that current measures effectively isolated 25-30% of the population, contributing to some reduction on the infection peak. Importantly, our simulations show that the infection burden can be further reduced with higher isolation degree, providing information for a second intervention.

scholarly journals Mathematical Modelling and Control of COVID-19 Transmission in the Presence of Exposed Immigrants

2021 ◽  
Vol 4 (2) ◽  
pp. 93-105
Author(s):  
Reuben Iortyer Gweryina ◽  
Chinwendu Emilian Madubueze ◽  
Martins Afam Nwaokolo
Keyword(s):  
Mathematical Model ◽  
Reproduction Number ◽  
Equilibrium Points ◽  
Horizontal Transmission ◽  
Endemic Equilibrium ◽  
Asymptotically Stable ◽  
Susceptible Population ◽  
Continuous Mixing ◽  
And Control ◽  
The Impact

In this paper, a mathematical model for COVID-19 pandemic that spreads through horizontal transmission in the presence of exposed immigrants is studied. The model has equilibrium points, notably, COVID-19-free equilibrium and COVID-19-endemic equilibrium points. The model exhibits a basic reproduction number, R0 which determines the elimination and persistence of the disease. It was found that when R0 < 1, then the equilibrium becomes locally asymptotically stable and endemic equilibrium does not exists. However, when R0 > 1, the equilibrium is found to be stable globally. This implies that continuous mixing of exposed immigrants with the susceptible population will make the eradication of COVID-19 difficult and endemic in the community. The system is also proved qualitatively to experience transcritical bifurcation close to the COVID-19-free equilibrium at the point R0 = 1. Numerically, the model is used to investigate the impact of certain other relevant parameters on the spread of COVID-19 and how to curtail their effect.

scholarly journals Model Updating and Global Eigenvalue Analysis of a Tie-Bolt Rotor Using Zero-Length Contact Elements under Different Preloads

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Pu Li ◽  
Qi Yuan
Keyword(s):  
Model Updating ◽  
Contact Stiffness ◽  
Great Influence ◽  
Modal Testing ◽  
Linear Spring ◽  
Modal Behavior ◽  
Stiffness And Damping ◽  
The Impact ◽  
Contact Parameters ◽  
Rotor Model

Tie-bolt rotors are composed of several disks fastened by tie bolts where contact properties have a great influence on the modal behavior. In this work, a linear spring-damper element is used to consider the contact stiffness and damping in a tie-bolt rotor. A tie-bolt rotor model is developed using the beam element and the zero-length contact element. Experimental modal testing is performed under different preloads of tie bolts. Model updating is carried out to tune the contact parameters using the Particle Swarm Optimization algorithm. Furthermore, a global eigenvalue evaluation is carried out to demonstrate the impact of the lumped spring-damper element on the modal results. Results show that a larger pretension reduces the influence of contact damping on modal parameters. Compared to antisymmetric modes, symmetric modes are more sensitive to the change of contact damping.

A Mathematical Model for the Study of Effectiveness in Therapy in Tuberculosis Taking into Account Associated Diseases

2021 ◽  
Author(s):  
Erick Delgado Moya ◽  
Alain Pietrus ◽  
Sergio Muniz Oliva
Keyword(s):  
Mathematical Model ◽  
Negative Impact ◽  
Population Based ◽  
The Other ◽  
Model Parameters ◽  
Tb Treatment ◽  
Mdr Tb ◽  
And Control ◽  
The Impact ◽  
Hiv Aids

Tuberculosis (TB) remains a major global health problem. We present a deterministic mathematical model for the study of the effectiveness of therapy in TB to determine the impact of HIV/AIDS and diabetes in the spread of the disease and drug resistance. Our model takes into account the relationships between TB, HIV/AIDS, and diabetes and we also study the behavior of multidrug-resistance (MDR-TB) and extensively drug-resistant (XDR-TB). The main mathematical and epidemiology features of the model are investigated. The basic reproduction number (R0) in the different sub-populations (diabetics, HIV/AIDS, and those who do not suffer from these diseases) was studied. Conditions were obtained on the model parameters to know when the growth of the parameters associated with resistance to TB treatment has a negative impact on the transmission of TB in the population based on the R0 study. It is concluded that MDR-TB and XDR-TB have a negative impact on TB control. Computational simulations show that a greater number of drug-sensitive TB cases with respect to MDR-TB and XDR-TB cases are reported in the infected compartments, and MDR-TB cases surpass XDR-TB cases, except in the diabetes sub-population, which has a growth of XDR-TB cases that surpasses the other compartments of infected of all the sub-populations. It was shown when comparing the sub-populations of diabetes and HIV/AIDS, that although the diabetes sub-population reports a higher number of XDR-TB cases, a lower number of drug-sensitive TB and MDR-TB cases, have a greater number of recovered cases with respect to HIV/AIDS sub-population at the end of the study period. Also, when the XDR-TB cases in the diabetes sub-population exceed the other infected compartments, there is a growth of recovered TB in this subpopulation. The results suggest that it is necessary to increase the attention to the diabetic population, which include improved glucose control, increase the number of specialized medical consultations to achieve permanence in TB treatment and control the entry of individuals to the diabetic compartments by tests of diabetes.

Dynamic Response of Two-Disk Systems With Friction and Misalignment

1998 ◽  
Author(s):  
Ahmed Anabtawi ◽  
Kambiz Farhang
Keyword(s):  
Mathematical Model ◽  
Dynamic Response ◽  
Contact Stiffness ◽  
Stick Slip ◽  
Torsional Response ◽  
Damping Characteristics ◽  
Disk Friction ◽  
Stiffness And Damping ◽  
The Mathematical Model ◽  
Friction Induced Vibration

Abstract Friction induced vibration and noise pose one of the most challenging problems. The complexity of the friction system arises due to the nonlinear nature of friction phenomena and that of contact stiffness and damping. This paper presents a mathematical model for studying the dynamic response of two-disk friction system in the presence of misalignment. The contact stiffness and damping characteristics of the system are represented in the axial as well as the torsional directions. In addition, the axial and torsional responses of the system are coupled by assuming dependency between the torsional response and the normal force between the two disks. Using the mathematical model, various scenarios are examined to study the effect of misalignment. These include cases of symmetric and asymmetric actuation forces as well as forces applied at unequal actuation times. The results suggest that asymmetry in actuation forces has negligible effect on stick-slip behavior of the system.

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