On Position/Force Control of Robot Interacting With Dynamic Environment in Cartesian Space

1996 ◽  
Vol 118 (1) ◽  
pp. 187-192 ◽  
Author(s):  
Miomir Vukobratovic´ ◽  
Radoslav Stojic´
Keyword(s):  
Dynamic Environment ◽  
Interaction Force ◽  
System Stability ◽  
Control Law ◽  
Unified Approach ◽  
Control Task ◽  
Simultaneous Stabilization ◽  
Cartesian Space ◽  
The One ◽  
Loop Motion

In this paper, the problem of simultaneous stabilization of both the robot motion and interaction force in Cartesian space, based on the unified approach to contact task problem in robotics [1], is considered. This control task is solved under the conditions set on environment dynamics which are less restrictive than those in [1] where some particular environment properties are required to ensure overall system stability. Furthermore, the one-to-one correspondence between closed-loop motion and force dynamic equations is obtained and unique control law ensuring system stability and preset either motion or force transient response is proposed.

Motion Coordination of Two Robots in Cartesian Space Based on Mechanical Impedance

2014 ◽  
Vol 613 ◽  
pp. 53-59 ◽  
Author(s):  
Adam Slota
Keyword(s):  
Mechanical Impedance ◽  
Interaction Force ◽  
Linear Increase ◽  
Dimensional Case ◽  
Motion Coordination ◽  
Coordinated Motion ◽  
Simulation Experiments ◽  
Cartesian Space ◽  
Motion Speed ◽  
In Series

Coordinated motion of two robots in Cartesian space is considered in the paper. Coordinated trajectory is generated as the sum of two motions: programmed and corrective. The corrective motion aims at limitation of the interaction force between robots. For calculation of the corrective motion speed the idea of mechanical impedance is used. As a measure of force interactions between robots change of distance between robots TCPs is used. Simulation experiments carried out for one dimensional case show that application of impedance based correctors results in the linear growth of change of distance between robots TCPs for constant difference between robots programmed speeds. Thus a modification of impedance based correctors is proposed. The modification consists in introduction of an integrating element in series with impedance corrector. Simulation tests for the modified correctors provide improved results – magnitude of change of distance is decreased. Linear increase of change of distance for impedance corrector is changed into a constant non zero value, whereas constant non zero value is changed into zero value. Simulation results for two dimensional case of coordinated motion are also presented.

DETERMINATION OF MODEL PARAMETERS OF ROCKET STABILIZATION SYSTEM IN FLIGHT

2021 ◽  
Vol 6 ◽  
pp. 78-92
Author(s):  
Volt Avdejev ◽  
Keyword(s):  
Relative Weight ◽  
Stability Margin ◽  
Current Data ◽  
System Stability ◽  
System Of Nonlinear Equations ◽  
Model Parameters ◽  
Control Law ◽  
Stabilization System ◽  
Measuring Devices ◽  
Perturbation Compensation

The dynamic characteristics of the system that includes the controlled object and the regulator largely depend on the choice of the control law, which is determined based on the nominal values of the parameters of the mathematical model of the stabilization process and its priority indicator. Due to the deviation of the missile parameters and, accordingly, the model from the nominal values, the designers set the safety factors based on the most unfavorable conditions, which negatively affects the overall performance, in particular, the relative weight of the payload. Therefore, there is a need to develop algorithms for adjustment that is identification model parameters during the flight using the signals of measuring devices and the capabilities of on-board computers. This will increase the efficiency of methods of choosing the control law based on such indicators as stabilization accuracy, stability margin and power requirements of the actuator. The aim of the article is to develop methods for refining the parameters of the rocket stabilization system in the yawing plane, which are based on the use of current data of measuring devices of the part of coordinates of the state vector, and verify the effectiveness of refinement in terms of the above indicators. A linear stationary model of a system for stabilizing the perturbed motion of a rocket taking into account the inertia of the actuator in the form of ordinary fifth-order differential equations is adopted. Two approaches are proposed to approximate the model parameters to their actual values. In the first in the model parameter space there is a minimum of the integral of the distance between the points of the trajectory according to the signals of the measuring devices and the trajectory obtained by modeling the perturbation compensation process. In the second, the actual values of the parameters are the result of solving a system of nonlinear equations, which includes data from measuring devices and the corresponding data obtained by simulation. On the example of space rocket parameters it is shown that the choice of the control law based on the actual coefficients of the model leads to a significant reduction of deviations from the set value of the system stability margin, stabilization error and power of the actuator.

Estimation of Critical Damping in Robot Joints and Identification of the Joint for Design With Most Effective Damping Enhancement

1994 ◽  
Author(s):  
Ahmad A. Smaili ◽  
Muhammad Sannah
Keyword(s):  
Natural Frequency ◽  
System Stability ◽  
Flexible Robot ◽  
Robot System ◽  
Joint Compliance ◽  
Dynamics And Control ◽  
Joint Identification ◽  
The One ◽  
And Control ◽  
Critical Damping

Abstract A major hindrance to dynamics and control of flexible robot manipulators is the deficiency of its inherent damping. Damping enhancement, therefore, should result in lower vibration amplitudes, shorter settling times, and improvement of system stability. Since the bulk of robot vibrations is attributed to joint compliance, it is a prudent strategy to design joints with sufficient inherent damping. In this article, a method is proposed to estimate critical damping at each joint and identify the joint that should be targeted for design with sufficient built-in damping. The target joint identification process requires that a n-joint robot system is divided into n-subsystems. Subsystem i includes the compliance of joint i and the inertia of the succeeding links, joint mechanisms, and payload. An equivalent single degree of freedom torsional model is devised and the natural frequency and critical damping is evaluated for each subsystem. The estimated critical damping at the joints are used to determine the elastodynamic response of the entire robot system from a model that includes joint compliance, shear deformation, rotary inertia, and geometric stiffness. The response revealed the following conclusion: The joint of the manipulator that would result in lower amplitudes of vibrations and shorter settling times when designed with sufficient built-in damping is the one that renders a subsystem whose natural frequency is the lowest of all subsystems comprising the robot.

Bifurcation Analysis of Ship Steering in Canals

2003 ◽  
Vol 46 (02) ◽  
pp. 92-100
Author(s):  
Fotis A. Papoulias ◽  
Panos E. Kapasakis
Keyword(s):  
Bifurcation Analysis ◽  
Complete System ◽  
Equations Of Motion ◽  
Open Loop ◽  
System Stability ◽  
Control Law ◽  
Time Lags ◽  
Essential Dynamics ◽  
Ship Steering ◽  
Loop Dynamics

The problem of ship steering in canals and confined waters is analyzed with emphasis on stability and bifurcation analysis. The classical maneuvering equations of motion augmented with a model for ship-canal interaction are used to model open-loop dynamics. Coupling of a control law and a guidance scheme with appropriate time lags is employed to model the essential dynamics of a helmsman. The complete system is analyzed using both linear and nonlinear techniques in order to assess its stability under finite disturbances. The results indicate that for certain regions of parameters, limit cycle oscillations may develop that could compromise system stability and safety of operations.

Genres and Motives

2015 ◽  
pp. 13-63
Author(s):  
Ram Ben-Shalom
Keyword(s):  
Middle Ages ◽  
The Other ◽  
Unified Approach ◽  
Historical Events ◽  
Southern France ◽  
Jewish Historiography ◽  
Religious Polemic ◽  
The Many ◽  
The One ◽  
Christian Discourse

This chapter examines the genres and motives behind Jewish chronology during the Middle Ages. Jewish historiography focused on correlating Jewish chronology, general chronology, and Christian chronology. This was a similar approach to Christian writers. The chapter shows that this correlation of Jewish chronology with Christian and general chronology was one of the many components of medieval Jewish–Christian discourse. On the one hand, this suggests that Jews had a unified approach to history, in which they saw themselves as full participants. On the other, the timing and meaning of historical events were part of the religious polemic with Christianity. Religious polemic and apocalypticism were important reasons why Jewish scholars in Spain and southern France engaged in historiography. Other motives included the moral lessons that could be found in history and intellectual curiosity.

scholarly journals Autopilot Design for a Compound Control Small-Scale Solid Rocket in the Initial Stage of Launch

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Tian Dong ◽  
Changjian Zhao ◽  
Zhiguo Song
Keyword(s):  
Sliding Mode Control ◽  
Sliding Mode ◽  
System Stability ◽  
Small Scale ◽  
Control Law ◽  
Rolling Moment ◽  
Mode Control ◽  
Compound Control ◽  
Initial Stage ◽  
Solid Rocket

In this paper, an autopilot design method for a compound control small-scale solid rocket is proposed. The rocket has multiple actuators, including a flexible nozzle for pitching and yawing channels, aerodynamic fins for rolling channel, and lateral thrusters which work in on-off mode for all three channels. In order to keep the aircraft steady in the initial stage of launch when the dynamic pressure is low, the autopilot is aimed at optimizing the cooperation among the actuators. Firstly, without considering the discontinuous lateral thrust, the control law for flexible nozzle and aerodynamic fins is achieved via the sliding mode control approach. On this basis, an object to be controlled with choiceness is obtained for the lateral thrusters controlled loop. Secondly, the operation logic of lateral thrusters is programmed, regarding rolling moment as priority. Thirdly, after a continuous controller is obtained, a discretization method for the lateral thrusters control law is designed combining the characteristics of sliding mode control and Lyapunov’s stableness theorem. Finally, the fundamental cause why compound control improves the system stability is given theoretically. Simulation results validate the improved response performance and robustness against uncertainties and disturbance of the autopilot.

scholarly journals Control law design of hypersonic vehicles using the elastic surrogate model

2019 ◽  
Vol 39 (1) ◽  
pp. 216-229
Author(s):  
Yanbin Liu ◽  
Yanhui Tong ◽  
Feiteng Jin
Keyword(s):  
Surrogate Model ◽  
Parametric Model ◽  
Hypersonic Vehicle ◽  
System Stability ◽  
Control Law ◽  
Analysis Method ◽  
Elastic Mode ◽  
Panel Methods ◽  
Sensitivity Analysis Method ◽  
Elastic Modes

This paper presents a novel control design strategy for the hypersonic vehicle using the elastic surrogate model. First, the parametric model is established for the rigid mode of the hypersonic vehicle based on the engineering estimation and panel methods. Then, the beam surrogate model is applied to identify the elastic mode of the hypersonic vehicle, and the complete parametric model including the rigid and elastic modes is obtained accordingly. Afterward, the control-relevant model is acquired based on the Morris sensitivity analysis method. Furthermore, the control system using the surrogate model is proposed for the hypersonic vehicle to suppress elastic disturbances and maintain system stability. Finally, an illustrative example of the hypersonic vehicle is provided to verify the effectiveness of the presented methods.

scholarly journals Design, Implementation and Testing of a Novel Prototype Orthotic Knee Joint with Two Degrees of Freedom in a Patient with Medial Knee Osteoarthritis

2019 ◽  
Vol 18 (4) ◽  
pp. 524
Author(s):  
Siamak Aghajani-Fesharaki ◽  
Farzam Farahmand ◽  
Hassan Saeedi ◽  
Ehsan Abdollahy
Keyword(s):  
Knee Joint ◽  
Knee Osteoarthritis ◽  
Degrees Of Freedom ◽  
Interaction Force ◽  
Transverse Plane ◽  
Materials Testing ◽  
Keywords Knee ◽  
Two Degrees Of Freedom ◽  
Keywords Knee Joint ◽  
The One

Knee braces are a conservative treatment option for patients with knee osteoarthritis (KOA). However, no commercially available orthotic knee joint currently reflects natural knee movements. A prototype orthotic knee joint with two degrees of freedom (DOF) in the sagittal and transverse planes was developed to more closely simulate the natural motion of the knee joint. The prototype was tested on a male subject with medial KOA during a sit-to-stand task. The efficacy of the transverse plane DOF was assessed by comparing the limb-orthosis interaction force when the transverse plane was locked to mimic a one-DOF setting versus when it was unlocked. Unlocking the transverse plane eliminated the 45-Newton shearing force produced with the one-DOF setting at wide angles of flexion. The two-DOF orthotic knee joint prototype demonstrated greater conformity to natural knee movements, allowing the wearer to better tolerate bracing-related difficulties. Keywords: Knee Joint; Knee Osteoarthritis; Orthotic Devices; Braces; Rotation; Movement; Materials Testing.

Controller Design of a Distributed Slewing Flexible Structure—A Frequency Domain Approach

1997 ◽  
Vol 119 (4) ◽  
pp. 809-814 ◽  
Author(s):  
S. M. Yang ◽  
J. A. Jeng ◽  
Y. C. Liu
Keyword(s):  
Frequency Domain ◽  
Transfer Functions ◽  
Controller Design ◽  
System Stability ◽  
Feedback Gain ◽  
Flexible Structure ◽  
Control Law ◽  
Discrete Parameter ◽  
Locus Method ◽  
Beam Experiment

The vibration control of a slewing flexible structure by collocated and noncollocated feedback is presented in this paper. A stability criterion derived from the root locus method in frequency domain is applied to predict the closed-loop system stability of the distributed parameter model whose analytical transfer functions are formulated. It is shown that the control law design requires neither distributed state sensing/estimation nor functional feedback gain; moreover, the spillover problem associated with discrete parameter model can be prevented. Implementation of the noncollocated feedback in a slewing beam experiment validates that the control law is effective in pointing accuracy while suppressing the tip vibration.

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