A Study of Control Strategies for the Reduction of Structural Vibration Transmission

1999 ◽  
Vol 121 (4) ◽  
pp. 482-487 ◽  
Author(s):  
P. Gardonio ◽  
S. J. Elliott
Keyword(s):  
Kinetic Energy ◽  
Degrees Of Freedom ◽  
Control Strategies ◽  
Structural Vibration ◽  
Total Power ◽  
Vibration Transmission ◽  
Active Isolation ◽  
Axial Forces ◽  
Common Framework ◽  
Base Structure

A theoretical study of the active control of structural vibration transmission in a multiple isolator system comprising a piece of equipment mounted on a base structure via active mounts is presented. Two types of problem have been studied with a common framework: first, the active isolation of vibration transmission from the equipment to the base structure and, second, the active isolation of vibration transmission from the base structure to the equipment. Four different control strategies using the measured axial velocity or/and axial force underneath or at the top of the mounts have been investigated and compared with the effectiveness of the reference control approaches of minimizing the total power transmitted from the equipment to the flexible base structure or minimizing the total kinetic energy of the suspended rigid equipment when driven by the base structure. For the first type of isolation problem the best control is achieved when a cost function which minimizes the weighted mm of the square values of the axial velocities and axial forces is implemented. For the second isolation problem the best control performance is given by the minimization of an estimate of the kinetic energy of the suspended equipment related to the translational degrees of freedom.

scholarly journals Motion Planning for a Mobile Humanoid Manipulator Working in an Industrial Environment

2021 ◽  
Vol 11 (13) ◽  
pp. 6209
Author(s):  
Iwona Pajak ◽  
Grzegorz Pajak
Keyword(s):  
Kinetic Energy ◽  
Collision Avoidance ◽  
Industry 4.0 ◽  
Degrees Of Freedom ◽  
Industrial Environment ◽  
Acceleration Level ◽  
Different Types ◽  
Manipulability Measure ◽  
Robotic Tasks ◽  
Primary Problem

This paper presents the usage of holonomic mobile humanoid manipulators to carry out autonomous tasks in industrial environments, according to the smart factory concept and the Industry 4.0 philosophy. The problem of transporting lengthy objects, taking into account mechanical limitations, the conditions for avoiding collisions, as well as the dexterity of the manipulator arms was considered. The primary problem was divided into three phases, leading to three different types of robotic tasks. In the proposed approach, the pseudoinverse Jacobian method at the acceleration level to solve each of the tasks was used. The redundant degrees of freedom were used to satisfy secondary objectives such as robot kinetic energy, the maximization of the manipulability measure, and the fulfillment mechanical and collision-avoidance limitations. A computer example involving a mobile humanoid manipulator, operating in an industrial environment, illustrated the effectiveness of the proposed method.

scholarly journals Finite-Horizon Kinetic Energy Optimization of a Redundant Space Manipulator

2021 ◽  
Vol 11 (5) ◽  
pp. 2346
Author(s):  
Alessandro Tringali ◽  
Silvio Cocuzza
Keyword(s):  
Kinetic Energy ◽  
Real Time ◽  
Inverse Kinematics ◽  
Degrees Of Freedom ◽  
Computational Time ◽  
Redundant Manipulators ◽  
Space Robotics ◽  
Optimal Method ◽  
End Effector ◽  
Global Optimal

The minimization of energy consumption is of the utmost importance in space robotics. For redundant manipulators tracking a desired end-effector trajectory, most of the proposed solutions are based on locally optimal inverse kinematics methods. On the one hand, these methods are suitable for real-time implementation; nevertheless, on the other hand, they often provide solutions quite far from the globally optimal one and, moreover, are prone to singularities. In this paper, a novel inverse kinematics method for redundant manipulators is presented, which overcomes the above mentioned issues and is suitable for real-time implementation. The proposed method is based on the optimization of the kinetic energy integral on a limited subset of future end-effector path points, making the manipulator joints to move in the direction of minimum kinetic energy. The proposed method is tested by simulation of a three degrees of freedom (DOF) planar manipulator in a number of test cases, and its performance is compared to the classical pseudoinverse solution and to a global optimal method. The proposed method outperforms the pseudoinverse-based one and proves to be able to avoid singularities. Furthermore, it provides a solution very close to the global optimal one with a much lower computational time, which is compatible for real-time implementation.

scholarly journals Study on Vibration Transmission among Units in Underground Powerhouse of a Hydropower Station

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3015 ◽  
Author(s):  
Jijian Lian ◽  
Hongzhen Wang ◽  
Haijun Wang
Keyword(s):  
Low Frequency ◽  
Field Tests ◽  
Vertical Vibration ◽  
Transmission Mechanism ◽  
Structural Vibration ◽  
Hydropower Station ◽  
Fe Model ◽  
Vibration Transmission ◽  
Underground Powerhouse ◽  
Mechanical Models

Research on the safety of powerhouse in a hydropower station is mostly concentrated on the vibration of machinery structure and concrete structure within a single unit. However, few studies have been focused on the vibration transmission among units. Due to the integrity of the powerhouse and the interaction, it is necessary to study the vibration transmission mechanism of powerhouse structure among units. In this paper, field structural vibration tests are conducted in an underground powerhouse of a hydropower station on Yalong River. Additionally, the simplified mechanical models are established to explain the transmission mechanism theoretically. Moreover, a complementary finite element (FE) model is built to replicate the testing conditions for comprehensive analysis. The field tests results show that: (1) the transmission of lateral-river vibration is greater than those of longitude-river vibration and vertical vibration; (2) the vibration transmission of the vibrations that is caused by the low frequency tail fluctuation is basically equal to that of the vibrations caused by rotation of hydraulic generator. The transmission mechanism is demonstrated by the simplified mechanical models and is verified by the FE results. This study can provide guidance for further research on the vibration of underground powerhouse structure.

scholarly journals Control Strategies for Gait Tele-Rehabilitation System Based on Parallel Robotics

2021 ◽  
Vol 11 (23) ◽  
pp. 11095
Author(s):  
Antonio P. L. Bo ◽  
Leslie Casas ◽  
Gonzalo Cucho-Padin ◽  
Mitsuhiro Hayashibe ◽  
Dante Elias
Keyword(s):  
Degrees Of Freedom ◽  
Control Strategies ◽  
Subjective Evaluation ◽  
Wearable Sensors ◽  
Movement Data ◽  
Trunk Inclination ◽  
Limited Degree ◽  
Parallel Robotics ◽  
Limb Rehabilitation ◽  
Technical Capacity

Among end-effector robots for lower limb rehabilitation, systems based on Stewart–Gough platforms enable independent movement of each foot in six degrees of freedom. Nevertheless, control strategies described in recent literature have not been able to fully explore the potential of such a mechatronic system. In this work, we propose two novel approaches for controlling a gait simulator based on Stewart–Gough platforms. The first strategy provides the therapist direct control of each platform using movement data measured by wearable sensors. The following scheme is designed to improve the level of engagement of the patient by enabling a limited degree of control based on trunk inclination. Both strategies are designed to facilitate future studies in tele-rehabilitation settings. Experimental results have illustrated the feasibility of both control interfaces, either in terms of system performance or user subjective evaluation. Technical capacity to deploy in tele-rehabilitation was also verified in this work.

scholarly journals Characteristic Constraint Modes for Component Mode Synthesis

1999 ◽  
Author(s):  
Matthew P. Castanier ◽  
Yung-Chang Tan ◽  
Christophe Pierre
Keyword(s):  
Degrees Of Freedom ◽  
Natural Frequencies ◽  
Component Mode Synthesis ◽  
Complex Structures ◽  
Cantilever Plate ◽  
Vibration Transmission ◽  
Stiffness Matrices ◽  
Physical Insight ◽  
Insight Into

Abstract In this paper, a technique is presented for improving the efficiency of the Craig-Bampton method of Component Mode Synthesis (CMS). An eigenanalysis is performed on the partitions of the CMS mass and stiffness matrices that correspond to the so-called constraint modes. The resultant eigenvectors are referred to as “characteristic constraint modes,” since they represent the characteristic motion of the interface between the component structures. By truncating the characteristic constraint modes, a CMS model with a highly-reduced number of degrees of freedom may be obtained. An example of a cantilever plate is considered. It is shown that relatively few characteristic constraint modes are needed to yield accurate approximations of the lower natural frequencies. This method also provides physical insight into the mechanisms of vibration transmission in complex structures.

scholarly journals Modified Space Vector Modulated Z Source Inverter with Effective DC Boost and Lowest Switching Stress

2010 ◽  
Vol 7 (1) ◽  
pp. 70 ◽  
Author(s):  
S. Thangaprakash ◽  
A. Krishnan
Keyword(s):  
Control Algorithm ◽  
Degrees Of Freedom ◽  
Control Strategies ◽  
Input Voltage ◽  
Duty Ratio ◽  
Space Vector ◽  
Voltage Vector ◽  
Voltage Stress ◽  
Capacitor Voltage ◽  
Full Utilization

 This paper presents a modified control algorithm for Space Vector Modulated (SVM) Z-Source inverters. In traditional control strategies, the Z-Source capacitor voltage is controlled by the shoot through duty ratio and the output voltage is controlled by the modulation index respectively. Proposed algorithm provides a modified voltage vector with single stage controller having one degree of freedom wherein traditional controllers have two degrees of freedom. Through this method of control, the full utilization of the dc link input voltage and keeping the lowest voltage stress across the switches with variable input voltage could be achieved. Further it offers ability of buck-boost operation, low distorted output waveforms, sustainability during voltage sags and reduced line harmonics. The SVM control algorithm presented in this paper is implemented through Matlab/Simulink tool and experimentally verified with Z-source inverter prototype in the laboratory. 

Method for Selecting Master Degrees of Freedom for Rotating Substructure

2014 ◽  
Author(s):  
Yanfei Zuo ◽  
Jianjun Wang ◽  
Weimeng Ma ◽  
Xue Zhai ◽  
Xinyu Yao
Keyword(s):  
High Pressure ◽  
Kinetic Energy ◽  
Degrees Of Freedom ◽  
Original Model ◽  
Dynamic Coupling ◽  
Stationary Reference Frame ◽  
Model Size ◽  
Gyroscopic Effects ◽  
Localized Damping ◽  
Frame Frequency

A method of selecting master degrees of freedom (DOFs) for rotating substructure is presented in this paper to obtain reduced 3D rotor models. Fixed modes of the substructure below thrice the operating frequency are analyzed. According to each mode shape, the DOFs at where main kinetic energy locates are selected as master DOFs to decrease missing of dynamic coupling. Additional DOFs may be selected based on traditional substructure method. In the stationary reference frame, frequency-dependent gyroscopic effects can be included as damping matrices changing with spin speed. Besides, by selecting appropriate substructure, localized damping and key parts of the rotor for analysis can be kept the same as the original model. A reduced model of a high pressure rotor amply demonstrated the capability of the method in reducing the model size and increasing the computational efficiency with less than two percent error.

Active Control of Elastodynamic Vibrations of a Flexible Mechanism With Piezoelectric Actuator

1999 ◽  
Author(s):  
Ching-I Chen
Keyword(s):  
Control Theory ◽  
Active Control ◽  
Piezoelectric Actuator ◽  
Control Strategies ◽  
Piezoelectric Actuators ◽  
Structural Vibration ◽  
Control Technique ◽  
Vibration Modes ◽  
Time Sharing ◽  
Transient Dynamic

Abstract This study focused on the application of active vibration control strategies for flexible moving structures which degrade into transient dynamic vibration problem. These control strategies are based primarily on modal control methods in which the flexible moving structures are controlled by reducing their dominant vibration modes. This work numerically investigated active control of the elastodynamic response of a four-bar mechanical system, using a piezoelectric actuator. A controller based on the modified independent modal space control theory was also utilized. This control theory produced overall excellent performance in terms of achieving the desired closed-loop structural damping. The merits of this technique include its ability to manage the spill-over effect, i.e. eliminate the magnitude of vibrations associated with uncontrolled modes, using only a few selected modes for control. This control was accomplished using a time sharing technique, which reduces the number of piezoelectric actuators required to control a large number of vibration modes. Furthermore, this algorithm implements a procedure for determining the optimal locations for the piezoelectric actuators. The dynamics of a steel four-bar linkage was selected with a flexible coupler separated by six elements and one piezoelectric actuator was used in the numerical simulation. The optimal actuator position was located at the third element from the right to the left. Results in this study demonstrated that a highly desired the structural vibration damping could be achieved. This control technique can be applied to transient dynamic systems.

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