Reduction of Induced Vibration Using Motion-Doubling Linkage Mechanisms

2006 ◽  
Author(s):  
J. Rastegar ◽  
J. Zhang
Keyword(s):  
High Speed ◽  
High Harmonic ◽  
Full Rotation ◽  
Rocking Motion ◽  
Points Of View ◽  
Harmonic Components ◽  
Input Motion ◽  
And Control ◽  
Special Case ◽  
Input Torque

In recent studies, the authors presented a special class of planar and spatial linkage mechanisms in which for a continuous full rotation or continuous rocking motion of the input link, the output link undergoes two continuous rocking motions. Such linkage mechanisms were referred to as the “motion-doubling” linkage mechanisms. It was also shown that in a special case of such mechanisms, the fundamental frequency of the input motion is doubled. This class of mechanisms generally has dynamics advantage over regular mechanisms designed to achieve similar gross output motions. In the present study, it is shown that in general and for the same gross output motion, motion-doubling mechanisms require lower input torques, and that the high harmonics of the input torque have smaller amplitudes. The high harmonic components present in the input torque are the main source of vibration and control problems in the system or device that the mechanism operates and its own structure. It is therefore concluded that when vibration and motion precision is of concern, such as in high-speed and precision machinery, motion-doubling mechanisms are generally more suitable from the potential vibration excitation and control points of view and actuating torque requirements.

Special Cases of Input Speed Doubling Linkage Mechanisms and Their Dynamics Advantage

2004 ◽  
Author(s):  
J. Rastegar ◽  
J. Zhang
Keyword(s):  
Fundamental Frequency ◽  
Linkage Mechanism ◽  
Practical Applications ◽  
Special Cases ◽  
Lower Amplitude ◽  
Full Rotation ◽  
Rocking Motion ◽  
Frequency Components ◽  
Special Case ◽  
Input Torque

In a recent study, Rastegar, et al. (2003), presented a special class of planar and spatial linkage mechanisms in which for a continuous full rotation or continuous rocking motion of the input link, the output link undergoes two continuous rocking motions. In a special case of such mechanisms, for periodic motions of the input link, the output motion is periodic with a doubled fundamental frequency. The above class of linkage mechanisms were referred to as “speed-doubling” linkage mechanisms. Such mechanisms can be cascaded to further double the fundamental frequency (rocking motion) of the output motion. They can also be cascaded with other linkage mechanisms to obtain crank-rocker or crank-crank type of mechanisms. The conditions for the existence of “speed-doubling” linkage mechanisms were also provided. In this paper, a study of the dynamics of a “speed-doubling” linkage mechanism is presented. It is shown that such mechanisms have dynamic advantage over regular mechanisms designed to achieve similar output motions. The main advantage of such mechanisms is shown to be their lower peak input torque requirement, and that the required torque generally has lower amplitude high-frequency components. The speed-doubling mechanisms have practical applications, particularly when higher output speeds are desired, since higher output motions can be achieved with lower input speeds and smaller motors.

Integration of Smart Actuators in the Structure of Robots for High-Speed and Precision Object Manipulation

2001 ◽  
Author(s):  
Jahangir S. Rastegar ◽  
Lifang Yuan
Keyword(s):  
High Speed ◽  
Robot Manipulator ◽  
Robot Manipulators ◽  
High Harmonic ◽  
Object Manipulation ◽  
Smart Actuators ◽  
Computer Controlled ◽  
Harmonic Components ◽  
Joint Motions ◽  
And Control

Abstract A systematic method is presented for optimal integration of smart actuators into the structure of robot manipulators for the purpose of enabling them to perform smooth object manipulation with smooth actuated joint motions. Here, the motions are considered to be smooth if they do not contain high harmonic components. For optimal positioning of smart actuators in the structure of robot manipulators, a method is developed based on the evaluation of the transmissibility of displacement (velocity and/or force) from the smart actuators to the robot manipulator joint motions and the end-effector displacements (velocity and/or force). A method is then presented for synthesizing actuated joint and object motions to achieve trajectories that do not contain high harmonic components. By minimizing the high harmonic components of the required joint and object motions with properly sized and placed smart actuators, such computer-controlled machines can operate at relatively higher speeds and achieve greater tracking precision with minimal vibration and control problems. A number of numerical examples are provided.

Optimal Smart Actuator Integration to Reduce Vibration in High Speed Mechanical Systems

2001 ◽  
Author(s):  
J. Rastegar ◽  
L. Yuan ◽  
L. Hua
Keyword(s):  
High Speed ◽  
Robot Manipulator ◽  
Robot Manipulators ◽  
High Harmonic ◽  
Smart Actuators ◽  
Computer Controlled ◽  
Harmonic Components ◽  
Smart Actuator ◽  
Joint Motions ◽  
And Control

Abstract A systematic method is presented for optimal integration of smart actuators into the structure of robot manipulators for the purpose of enabling them to perform smooth object manipulation with smooth actuated joint motions. Here, the motions are considered to be smooth if they do not contain high harmonic components. For optimal positioning of smart actuators in the structure of robot manipulators, a method is developed based on the evaluation of the transmissibility of displacement (velocity and/or force) from the smart actuators to the robot manipulator joint motions and the end-effector displacements (velocity and/or force). A method is then presented for synthesizing actuated joint and object motions to achieve trajectories that do not contain high harmonic components. By minimizing the high harmonic components of the required joint and object motions with properly sized and placed smart actuators, such computer-controlled machines can operate at relatively higher speeds and achieve greater tracking precision with minimal vibration and control problems. A number of numerical examples are provided.

On the Relationship Between the Harmonic Amplitudes of the Output Motion of Closed-Loop Linkage Mechanisms

2008 ◽  
Author(s):  
Jahangir Rastegar ◽  
Dake Feng ◽  
Lin Hua
Keyword(s):  
Closed Loop ◽  
High Harmonic ◽  
Constant Input ◽  
Vibration Excitation ◽  
Basic Characteristics ◽  
Harmonic Components ◽  
Input Motion ◽  
Four Bar Linkage ◽  
The Relationship

It is well known that due to the nonlinearity of the kinematics of linkage mechanisms, their output motion contains harmonics of the input motion. In most mechanisms, the generated high harmonic components in the output motion are the main source of vibration excitation that the mechanism imparts on the overall system, including its own structure. For simple linkage mechanisms such as slider-cranks and four-bar linkage mechanisms, the amplitudes of the harmonics of the output motion for constant input rotation have been derived. In the present study, it is shown that certain relationships exist between the amplitudes of the harmonic of the output motions. In particular, odd and even harmonic amplitudes are shown to be related through an inequality relationship. These relationships are due to the basic characteristics of the linkage mechanisms motions, which are significantly simplified for certain linkage geometries. The relationships between the amplitudes of the output velocity harmonics are derived for slider-crank and four-bar linkage mechanisms.

On the Existence of Special Cases of Input Speed Doubling Linkage Mechanisms

2003 ◽  
Author(s):  
J. Rastegar ◽  
J. Zhang ◽  
L. Hua
Keyword(s):  
Fundamental Frequency ◽  
Force Transmission ◽  
Periodic Motions ◽  
Output Link ◽  
Practical Applications ◽  
Special Cases ◽  
Mode Of Operation ◽  
Full Rotation ◽  
Rocking Motion ◽  
Special Case

A special class of planar and spatial linkage mechanisms is presented in which for a continuous full rotation or continuous rocking motion of the input link, the output link undergoes two continuous rocking motions. In a special case of such mechanisms, for periodic motions of the input link with a fundamental frequency ω, the output motion is periodic but with a fundamental frequency of 2ω. In this paper, the above class of linkage mechanisms are referred to as speed-doubling linkage mechanisms. Such mechanisms can be cascaded to provide further doubling of the fundamental frequency (rocking motion) of the output motion. They can also be cascaded with other appropriate linkage mechanisms to obtain crank-rocker or crank-crank type of mechanisms. The conditions for the existence of speed-doubling linkage mechanisms are provided and their mode of operation is described in detail. Such speed-doubling mechanisms have practical applications, particularly when higher output speeds are desired, since higher output motions can be achieved with lower input speeds. Such mechanisms also appear to generally have force transmission and dynamics advantages over regular mechanisms designed to achieve similar output speeds.

Design and control of a high-speed direct-drive manipulator

1989 ◽  
Vol 27 (3) ◽  
pp. 375-394 ◽  
Author(s):  
K. YOUCEF-TOUMI ◽  
A. T. Y. KUO
Keyword(s):  
High Speed ◽  
Direct Drive ◽  
And Control

Effect of Slice Priority for admission control in 5G Wireless Networks: A comparison study for two Fuzzy-based systems considering Software-Defined-Networks

2020 ◽  
Vol 26 (3) ◽  
pp. 169-183
Author(s):  
Phudit Ampririt ◽  
Yi Liu ◽  
Makoto Ikeda ◽  
Keita Matsuo ◽  
Leonard Barolli ◽  
...  
Keyword(s):  
Wireless Networks ◽  
Admission Control ◽  
High Speed ◽  
Additional Parameter ◽  
Fifth Generation ◽  
Efficient Management ◽  
Grade Of Service ◽  
User Request ◽  
Control Decision ◽  
And Control

The Fifth Generation (5G) networks are expected to be flexible to satisfy demands of high-quality services such as high speed, low latencies and enhanced reliability from customers. Also, the rapidly increasing amount of user devices and high user’s requests becomes a problem. Thus, the Software-Defined Network (SDN) will be the key function for efficient management and control. To deal with these problems, we propose a Fuzzy-based SDN approach. This paper presents and compares two Fuzzy-based Systems for Admission Control (FBSAC) in 5G wireless networks: FBSAC1 and FBSAC2. The FBSAC1 considers for admission control decision three parameters: Grade of Service (GS), User Request Delay Time (URDT) and Network Slice Size (NSS). In FBSAC2, we consider as an additional parameter the Slice Priority (SP). So, FBSAC2 has four input parameters. The simulation results show that the FBSAC2 is more complex than FBSAC1, but it has a better performance for admission control.

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