Modeling and Experimental Evaluation of Asymmetric Pantograph Dynamics

1988 ◽  
Vol 110 (2) ◽  
pp. 168-174 ◽  
Author(s):  
S. D. Eppinger ◽  
D. N. O’Connor ◽  
W. P. Seering ◽  
D. N. Wormley
Keyword(s):  
High Performance ◽  
Degrees Of Freedom ◽  
Dynamic Models ◽  
Dynamic Testing ◽  
Dynamic Performance ◽  
Performance Model ◽  
Degree Of Freedom ◽  
Additional Degree ◽  
Three Degree Of Freedom ◽  
Two Degree Of Freedom

High-performance pantograph design requires control of pantograph dynamic performance. Many pantograph dynamic models developed to aid in the design process have employed two degrees of freedom, one for the head mass and one for the frame. In this paper, the applicability of these models to symmetric and asymmetric pantograph designs is reviewed. Two degree-of-freedom models have been shown to be appropriate to represent a number of symmetric pantograph designs. To represent the asymmetric designs considered in this paper, an additional degree of freedom representing frame dynamics has been introduced to yield a three degree-of-freedom nonlinear dynamic performance model. The model has been evaluated with experimental data obtained from laboratory dynamic testing of an asymmetric pantograph.

Robust Two-degree-of-freedom Control Based on H∞ Method for PMSM Drive System

2020 ◽  
Vol 13 (4) ◽  
pp. 496-506
Author(s):  
Qixin Zhu ◽  
Lei Xiong ◽  
Hongli Liu ◽  
Yonghong Zhu ◽  
Guoping Zhang
Keyword(s):  
Control System ◽  
Control Theory ◽  
Position Control ◽  
Dynamic Performance ◽  
Servo System ◽  
Degree Of Freedom ◽  
Trade Off ◽  
Standard Design ◽  
Position Controller ◽  
Two Degree Of Freedom

Background: The conventional method using one-degree-of-freedom (1DOF) controller for Permanent Magnet Synchronous Motor (PMSM) servo system has the trade-off problem between the dynamic performance and the robustness. Methods: In this paper, by using H∞ control theory, a novel robust two-degree-of-freedom (2DOF) controller has been proposed to improve the position control performance of PMSM servo system. Using robust control theory and 2DOF control theory, a H∞ robust position controller has been designed and discussed in detail. Results: The trade-off problem between the dynamic performance and robustness which exists in one-degree-of-freedom (1DOF) control can be dealt with by the application of 2DOF control theory. Then, through H∞ control theory, the design of robust position controller can be translated to H∞ robust standard design problem. Moreover, the control system with robust controller has been proved to be stable. Conclusion: Further simulation results demonstrate that compared with the conventional PID control, the designed control system has better robustness and attenuation to the disturbance of load impact.

Three degree of freedom description of movement of the human chest wall

1986 ◽  
Vol 60 (3) ◽  
pp. 928-934 ◽  
Author(s):  
J. C. Smith ◽  
J. Mead
Keyword(s):  
Chest Wall ◽  
Lung Volume ◽  
Pubic Symphysis ◽  
Degree Of Freedom ◽  
Rib Cage ◽  
Additional Degree ◽  
Wall Movement ◽  
Surface Displacements ◽  
Flexion Extension ◽  
Three Degree Of Freedom

A three degree of freedom description of movement of the human chest wall is presented. In addition to the standard variables representing surface displacements of the rib cage and abdominal wall in transverse planes, the description includes a variable representing axial displacements of the chest wall associated with postural movements of the spine and pelvis. A simple technique was developed for quantifying the axial displacements using a single measurement by magnetometry of changes in the distance between a point on the anterior surface of the rib cage near the xiphisternum and a point on the abdominal surface near the pubic symphysis. It was found that axial displacements produced by either flexion-extension of the spine or rotation of the pelvis in the standing postures can be treated as a single degree of freedom. The chest wall displacements induced over the range of axial displacement examined were as large as those normally accompanying a change in lung volume on the order of 30–50% of the vital capacity. It is concluded, however, that although this additional degree of freedom can cause large chest wall displacements, it probably cannot independently change lung volume. This implies that the system is constrained so that there are only a limited number of independent modes of chest wall movement that are capable of producing significant changes in lung volume. It also suggests that the system is constructed so that lung volume can be relatively independent of certain postural distortions of the chest wall.

Design of a Teaching Robot with Three Degrees of Freedom

2012 ◽  
Vol 619 ◽  
pp. 325-328
Author(s):  
You Jun Huang ◽  
Ze Lun Li ◽  
Zhi Cheng Huang
Keyword(s):  
Degrees Of Freedom ◽  
Low Cost ◽  
Degree Of Freedom ◽  
Good Repeatability ◽  
Main Components ◽  
Opening And Closing ◽  
Three Degree Of Freedom ◽  
Three Degrees Of Freedom ◽  
Application Prospects

A teaching robot with three degree of freedom is designed. The three degrees of freedom are: waist rotation, lifting and stretching of the arm and opening and closing of the gripper. The designs of the main components are: a mobile chassis, parallel rails, horizontal rails and manipulator. The teaching robot designed has the features of low cost, easy to regulation, good repeatability and it has good promotion and application prospects in the field of teaching.

Rudder/Fin Roll Stabilization of the USCG WMEC 901 Class Vessel

1999 ◽  
Vol 36 (03) ◽  
pp. 157-170
Author(s):  
Jerrold N. Sgobbo ◽  
Michael G. Parsons
Keyword(s):  
Degrees Of Freedom ◽  
Multiple Input Multiple Output ◽  
Cross Coupling ◽  
Degree Of Freedom ◽  
Rolling Motion ◽  
Rolling Moment ◽  
Multiple Input ◽  
Input Multiple Output ◽  
Three Degree Of Freedom ◽  
The U.S

The U.S. Coast Guard's 270-ft Medium Endurance Cutter (WMEC) operates with an active fin stabilization system. This system was designed using a one-degree-of-freedom (1-DOF) model in the roll direction. The controller was designed separate from the heading autopilot. The effects of the rudders and their ability to produce a significant rolling moment were also neglected as well as the cross coupling of roll motions into other degrees of freedom. This paper studies the effects of the rudders on the rolling motion of the ship using a three-degree-of-freedom (3-DOF) model. A simple optimal heading autopilot is designed and combined with the existing fin roll controller to investigate the effects of the rudders on the roll motions of this class of vessel. A rudder roll controller and a multiple input-multiple output (MIMO) rudder/fin controller are designed as well. Significant roll reduction can be achieved using the MIMO rudder/fin controller.

Two-Degree-of-Freedom Control of an Ionic Polymer-Metal Composite Actuator

2010 ◽  
Vol 670 ◽  
pp. 369-378 ◽  
Author(s):  
Minoru Sasaki ◽  
Yusuke Onouchi ◽  
Hirohisa Tamagawa ◽  
Satoshi Ito
Keyword(s):  
Transfer Function ◽  
Mathematical Models ◽  
High Performance ◽  
Input Voltage ◽  
Degree Of Freedom ◽  
Metal Composite ◽  
Ionic Polymer Metal Composites ◽  
Ionic Polymer ◽  
Polymer Metal ◽  
Two Degree Of Freedom

Mathematical models predicting the behaviour of IMPCs (Ionic Polymer-Metal Composites ) were built and their validity was verified computationally as well as experimentally. A transfer function associating the applied input voltage with the IPMC tip displacement was derived based on results obtained by vibration analysis. Employing the derived transfer function, three mathematical models, based on feed forward, feedback and two-degree-of-freedom models, were formulated. Computational and experimental verification of these models revealed that the feedback and two-degree-of-freedom models were capable of high performance in controlling the bending of an IPMC.

Hybrid Position/Force Control for a RRR 3-DoF Manipulator

2011 ◽  
Vol 48-49 ◽  
pp. 589-592 ◽  
Author(s):  
Shi Xiang Tian ◽  
Sheng Ze Wang
Keyword(s):  
Force Control ◽  
Free Space ◽  
High Performance ◽  
Degree Of Freedom ◽  
End Effector ◽  
Robot Trajectory ◽  
Simulation Results ◽  
Trajectory Following ◽  
Three Degree Of Freedom

In this paper, a novel hybrid position/force controller has been proposed for a three degree of freedom (3-DOF) of robot trajectory following that is required to switch between position and force control. The whole controller consists of two components: a positional controller and a force controller. Depending on whether the end-effector is in free space or in contact with the environments during work, the two subcontrollers run simultaneously to guide the manipulator tracking in free space and constraint environments. After the principle and stability of the controller are briefly analyzed, simulation results verify that the proposed controller attains a high performance.

scholarly journals Feedback Linearisation for Nonlinear Vibration Problems

2014 ◽  
Vol 2014 ◽  
pp. 1-16 ◽  
Author(s):  
S. Jiffri ◽  
P. Paoletti ◽  
J. E. Cooper ◽  
J. E. Mottershead
Keyword(s):  
Degrees Of Freedom ◽  
Nonlinear Problems ◽  
Second Order ◽  
Degree Of Freedom ◽  
Sensors And Actuators ◽  
Order Matrix ◽  
Problem Class ◽  
Aeroelastic Model ◽  
Matrix Differential ◽  
Three Degree Of Freedom

Feedback linearisation is a well-known technique in the controls community but has not been widely taken up in the vibrations community. It has the advantage of linearising nonlinear system models, thereby enabling the avoidance of the complicated mathematics associated with nonlinear problems. A particular and common class of problems is considered, where the nonlinearity is present in a system parameter and a formulation in terms of the usual second-order matrix differential equation is presented. The classical texts all cast the feedback linearisation problem in first-order form, requiring repeated differentiation of the output, usually presented in the Lie algebra notation. This becomes unnecessary when using second-order matrix equations of the problem class considered herein. Analysis is presented for the general multidegree of freedom system for those cases when a full set of sensors and actuators is available at every degree of freedom and when the number of sensors and actuators is fewer than the number of degrees of freedom. Adaptive feedback linearisation is used to address the problem of nonlinearity that is not known precisely. The theory is illustrated by means of a three-degree-of-freedom nonlinear aeroelastic model, with results demonstrating the effectiveness of the method in suppressing flutter.

Articulated Models of Cantilevers Conveying Fluid: The Study of a Paradox

1970 ◽  
Vol 12 (4) ◽  
pp. 288-300 ◽  
Author(s):  
M. P. Paidoussis ◽  
E. B. Deksnis
Keyword(s):  
Degrees Of Freedom ◽  
Continuous System ◽  
Dynamical Behaviour ◽  
Degree Of Freedom ◽  
Complex Frequency ◽  
Good Convergence ◽  
Articulated Models ◽  
Two Degree Of Freedom ◽  
Conveying Fluid ◽  
Oscillatory Instabilities

A general theory is presented for the dynamics of nth-degree-of-freedom articulated (lumped flexibility) models of cantilevers conveying fluid, of which the two-degree-of-freedom model of a column subjected to follower forces (first investigated by Ziegler) is a particular case. The ability of the articulated system to predict the dynamical behaviour of the continuous system modelled is investigated, and in particular the paradox that, whereas the continuous system is subject to only oscillatory instability (at sufficiently high flow), the model is generally subject to both oscillatory and buckling instabilities, and sometimes only to the latter. Complex frequency calculations show that buckling is associated with the higher modes of the articulated system, which, irrespective of the number of degrees of freedom, do not model well the corresponding modes of the continuous system. The critical flow velocities for buckling and oscillatory instabilities are calculated extensively, the latter showing good convergence to the corresponding values of the continuous system. The theory is supported by a set of experiments. Agreement between theory and experiment is satisfactorily good.

Discrete modular serpentine robotic tail: design, analysis and experimentation

Robotica ◽  
2018 ◽  
Vol 36 (7) ◽  
pp. 994-1018 ◽  
Author(s):  
Wael Saab ◽  
William S. Rone ◽  
Pinhas Ben-Tzvi
Keyword(s):  
Dynamic Models ◽  
Design Analysis ◽  
Degree Of Freedom ◽  
Legged Robots ◽  
Design Parameters ◽  
Inertial Loading ◽  
Forward Kinematic ◽  
The Impact ◽  
Accuracy And Repeatability ◽  
Two Degree Of Freedom

SUMMARYThis paper presents the design, analysis and experimentation of a Discrete Modular Serpentine Tail (DMST). The mechanism is envisioned for use as a robotic tail integrated onto mobile legged robots to provide a means, separate from the legs, to aid stabilization and maneuvering for both static and dynamic applications. The DMST is a modular two-degree-of-freedom (DOF) articulated, under-actuated mechanism, inspired by continuum and serpentine robotic structures. It is constructed from rigid links with cylindrical contoured grooves that act as pulleys to route and maintain equal displacements in antagonistic cable pairs that are connected to a multi-diameter pulley. Spatial tail curvatures are produced by adding a roll-DOF to rotate the bending plane of the planar tail curvatures. Kinematic and dynamic models of the cable-driven mechanism are developed to analyze the impact of trajectory and design parameters on the loading profiles transferred through the tail base. Experiments using a prototype are performed to validate the forward kinematic and dynamic models, determine the mechanism's accuracy and repeatability, and measure the mechanism's ability to generate inertial loading.

Inertial Vibration Damping Control for a Flexible Base Manipulator

2002 ◽  
Author(s):  
Lynnane E. George ◽  
Wayne J. Book
Keyword(s):  
Performance Index ◽  
Degrees Of Freedom ◽  
Position Control ◽  
Joint Space ◽  
Vibration Damping ◽  
Degree Of Freedom ◽  
Inertia Effects ◽  
Inertial Interaction ◽  
Flexible Base ◽  
Three Degree Of Freedom

A rigid (micro) robot mounted serially to the tip of a long, flexible (macro) manipulator is often used to increase reach capability, but flexibility in the macromanipulator can interfere with positioning accuracy. A rigid manipulator attached to a flexible but unactuated base was used to study a scheme to achieve positioning of the micromanipulator combined with enhanced vibration damping of the base. Inertial interaction forces and torques acting between the robot and its base were modeled and studied to determine how to use them to damp the vibration. One issue is that there are locations in the workspace where the rigid robot loses its ability to create interactions in one or more degrees of freedom. These “inertial singularities” are functions of the rigid robot’s joint variables. A performance index was developed to predict the ability of the rigid robot to damp vibration and will help ensure the robot is operating in joint space configurations favorable for inertial damping. When the performance index is used along with the appropriate choice of feedback gains, the inertia effects, or those directly due to accelerating the robot’s links, have the greatest influence on the interactions. By commanding the robot link’s accelerations out of phase with the base velocity, vibration energy will be removed from the system. This signal is then added to the rigid robot’s position control signal. Simulations of a rigid three degree of freedom anthropomorphic robot mounted on a flexible base were developed and show the effectiveness of the control scheme. In addition, experimental results demonstrating two degree of freedom vibration damping are included.

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