Research on a Type of Program-Controlled Three-Dimensional Vibration Platform

2016 ◽  
Vol 693 ◽  
pp. 1604-1610
Author(s):  
Ying Tian ◽  
Qing Jian Liu ◽  
Lei Zhang ◽  
Song Ling Tian ◽  
Peng Lin Li
Keyword(s):  
High Speed ◽  
Mechanical Vibration ◽  
Three Dimensional ◽  
Servo Motor ◽  
Linkage Mechanism ◽  
Nc System ◽  
Light Load ◽  
Left And Right ◽  
Parametric Adjustment ◽  
Four Bar Linkage

Conventional mechanical vibration platform vibrates not only in the direction of back and forth but also in the direction of up and down. Vibrations in both directions are achieved by two mechanisms, respectively. Three-dimensional vibration cannot be realized. In this paper, the servo motor, the gear drive mechanism, and the parallel four-bar linkage mechanism are combined with the NC system. And a type of program-controlled three-dimensional vibration platform is designed. The platform can vibrate in three directions, such as the directions of up and down, left and right, back and forth. The parametric adjustment of amplitude and frequency in three directions can be realized. The vibration platform is suitable for high-speed and light-load three-dimensional vibration. Compared with the existing mechanical vibration platform, the designed vibration platform overcomes some deficiencies to realize three-dimensional vibration with variable frequency and amplitude.

Optimal Control of a Flexible Mechanism Using a Combined Feedforward-Feedback Strategy: Simulation and Experiment

1999 ◽  
Author(s):  
Hubertus v. Stein ◽  
Heinz Ulbrich
Keyword(s):  
Optimal Control ◽  
Control Strategy ◽  
System Performance ◽  
High Speed ◽  
Time Varying ◽  
Linkage Mechanism ◽  
Additional Degree ◽  
Control Approach ◽  
Feedback Optimal Control ◽  
Four Bar Linkage

Abstract Due to the elasticity of the links in modern high speed mechanisms, increasing operating speeds often lead to undesirable vibrations, which may render a required accuracy unattainable or, even worse, lead to a failure of the whole process. The dynamic effects e.g. may lead to intolerable deviations from the reference path or even to the instability of the system. Instead of suppressing the vibration by a stiffer design, active control methods may greatly improve the system performance and lead the way to a reduction of the mechanism’s weight. We investigate a four-bar-linkage mechanism and show that by introducing an additional degree of freedom for a controlled actuator and providing a suitable control strategy, the dynamically induced inaccuracies can be substantially reduced. The modelling of the four-bar-linkage mechanism as a hybrid multi body system and the modelling of the complete system (including the actuator) is briefly explained. From the combined feedforward-feedback optimal control approach presented in (v. Stein, Ulbrich, 1998) a time-varying output control law is derived that leads to a very good system performance for this linear discrete time-varying system. The experimental results show the effectiveness of the applied control strategy.

scholarly journals Feeding mechanics and bite force modelling of the skull of Dunkleosteus terrelli , an ancient apex predator

2006 ◽  
Vol 3 (1) ◽  
pp. 77-80 ◽  
Author(s):  
Philip S.L Anderson ◽  
Mark W Westneat
Keyword(s):  
High Speed ◽  
Prey Capture ◽  
Mouth Opening ◽  
Biomechanical Model ◽  
Bite Force ◽  
Rapid Expansion ◽  
Large Individual ◽  
Linkage Mechanism ◽  
Feeding Mechanics ◽  
Four Bar Linkage

Placoderms are a diverse group of armoured fishes that dominated the aquatic ecosystems of the Devonian Period, 415–360 million years ago. The bladed jaws of predators such as Dunkleosteus suggest that these animals were the first vertebrates to use rapid mouth opening and a powerful bite to capture and fragment evasive prey items prior to ingestion. Here, we develop a biomechanical model of force and motion during feeding in Dunkleosteus terrelli that reveals a highly kinetic skull driven by a unique four-bar linkage mechanism. The linkage system has a high-speed transmission for jaw opening, producing a rapid expansion phase similar to modern fishes that use suction during prey capture. Jaw closing muscles power an extraordinarily strong bite, with an estimated maximal bite force of over 4400 N at the jaw tip and more than 5300 N at the rear dental plates, for a large individual (6 m in total length). This bite force capability is the greatest of all living or fossil fishes and is among the most powerful bites in animals.

A New Method for Determining the Effects of Structural Flexibility on the Dynamic Behavior of High Speed Mechanisms

1999 ◽  
Author(s):  
L. Yuan ◽  
J. Rastegar
Keyword(s):  
Dynamic Behavior ◽  
High Speed ◽  
New Method ◽  
Structural Flexibility ◽  
Structural Elements ◽  
Dynamics Modeling ◽  
Linkage Mechanism ◽  
Active Materials ◽  
Response Characteristics ◽  
Four Bar Linkage

Abstract A new method for the analysis of the effects of structural flexibility on the dynamic behavior of mechanical systems is presented. The developed method is in most part based on “tracing” the “propagation” of the effects of the high frequency motion requirements on the dynamic response characteristics of machines with structural flexibilities, particularly those with closed-loop kinematic structures. The method considers the “filtering” action of structural elements with flexibility. Such filtering of higher frequency motions is shown to have a predictable effect on the steady state motion of such mechanical system. The main advantage of the developed method is that the effects of such flexibilities can be determined without the need to perform the usual dynamics modeling and computer simulations. The method is shown to be very simple and readily implementable. The method is applied to a four-bar linkage mechanism with a longitudinally flexible coupler link. The obtained results are shown to be highly accurate as compared to those obtained by computer simulation. The application of the method to systematic design of machines with structural flexibility for high speed and precision operation, optimal integration of smart (active) materials into the structure of such machines, and some related issues are discussed.

A New Approach for the Reduction of Vibrational Excitation in Kinematics Synthesis of High Speed Linkages

2000 ◽  
Author(s):  
L. Yuan ◽  
J. Rastegar
Keyword(s):  
High Speed ◽  
Closed Loop ◽  
Vibrational Excitation ◽  
High Harmonic ◽  
Harmonic Component ◽  
Primary Source ◽  
Linkage Mechanism ◽  
New Approach ◽  
Function Generation ◽  
Four Bar Linkage

Abstract A new method is presented for the modification of the output motion of linkage mechanisms with closed-loop chains using cams positioned at one or more of its joints. In particular, the method is applied to a four-bar linkage mechanism that is synthesized for function generation for the purpose of eliminating the high harmonic component of the output link motion. By eliminating the high harmonic component of the output motion of a mechanism, the potential vibrational excitation that the mechanism can impart on the overall system, including its own structure, is greatly reduced. The resulting system should therefore be capable of operating at higher speeds with increased precision. For mechanisms with rigid links, the primary source of high harmonic motions is the nonlinearity of the kinematics of closed-loop chains. With the present method, the higher harmonic motions generated due to such nonlinearities are eliminated by the integration of appropriately designed cams that are used to vary the effective link lengths. A numerical example is provided together with a discussion of the related topics of interest.

Measuring the angle of attack of beating insect wings: robust three-dimensional reconstruction from two-dimensional images

1997 ◽  
Vol 200 (21) ◽  
pp. 2693-2704 ◽  
Author(s):  
A Willmott ◽  
C Ellington
Keyword(s):  
High Speed ◽  
Angle Of Attack ◽  
Three Dimensional ◽  
Numerical Algorithms ◽  
Longitudinal Axis ◽  
Wing Motion ◽  
Insect Wings ◽  
High Speed Film ◽  
Dimensional Reconstruction ◽  
Left And Right

A robust technique for determining the angle of attack of insect wings from film of free flight has to date proved elusive. This report describes the development of two new methods ­ the Strips and Planes techniques ­ which were designed to overcome some of the limitations experienced in previous studies. The accuracy and robustness of these novel methods were tested extensively using simulated hawkmoth wing outlines generated for a realistic range of wing positions and torsion. The results were compared with those from two existing methods ­ the Symmetry and Landmarks procedures. The performance of the latter technique will be strongly species-dependent; it could not be successfully applied to hawkmoth flight because of practical difficulties in obtaining suitable landmarks. The Planes method was the least successful of the remaining techniques, especially during those phases of the wingbeat when the orientations of the two wings relative to the camera viewpoint were similar. The Symmetry and Strips methods were tested further to investigate the effects on their performance of introducing additional camber or wing motion asymmetry. The results showed clearly that the Strips method should be the technique of choice wherever the axis of wing torsion is close to the longitudinal axis of the wing. The procedure involves the experimenter matching a model wing divided into chordwise strips to the true wing outline digitized from high-speed film. The use of strips rather than the points digitized in previous studies meant that the analysis required only one wing outline to be digitized. Symmetry of motion between the left and right wings is not assumed. The implications of requiring human input to the Strips method, as opposed to the strictly numerical algorithms of the alternative techniques, are discussed. It is argued that the added flexibility that this provides in dealing with images which have typically been recorded in suboptimal conditions outweighs the introduction of an element of subjectivity. Additional observations arising from the use of the Strips analysis with high-speed video sequences of hawkmoth flight are given.

A Systematic Method for Kinematics Synthesis of High-Speed Mechanisms With Optimally Integrated Smart Materials

2000 ◽  
Author(s):  
J. Rastegar ◽  
L. Yuan
Keyword(s):  
Smart Materials ◽  
High Speed ◽  
Vibrational Excitation ◽  
High Harmonic ◽  
Harmonic Component ◽  
Linkage Mechanism ◽  
Output Link ◽  
Mechanism Synthesis ◽  
Systematic Method ◽  
Four Bar Linkage

Abstract A systematic method is presented for kinematics synthesis of high-speed mechanisms with optimally integrated smart materials based actuators for the purpose of modifying the output link motion. As an example, the method is applied to a four-bar linkage mechanism that is synthesized for function generation to eliminate the high harmonic component of the output link motion. For mechanisms with rigid links, the high harmonic motions are generated due to the nonlinearity of the kinematics of their closed-loop chains. By eliminating the high harmonic component of the output motion, the potential vibrational excitation that the mechanism can impart on the overall system and its own structure is greatly reduced. The resulting system should therefore be capable of operating at higher speeds with increased precision. A numerical example is provided together with a discussion of the application of the method to other mechanism synthesis problems and some related topics of interest.

A New Mobile Robot With a Passive Mechanism and a Stereo Vision System for Hazardous Terrain Exploration

2004 ◽  
Author(s):  
Sukjune Yoon ◽  
Chun-Kyu Woo ◽  
Hyun Do Choi ◽  
Sung-Kee Park ◽  
Sung-Chul Kang ◽  
...  
Keyword(s):  
Remote Control ◽  
Mobile Robot ◽  
Obstacle Avoidance ◽  
Stereo Vision ◽  
High Speed ◽  
Vision System ◽  
Three Dimensional ◽  
Linkage Mechanism ◽  
Passive Mechanism ◽  
Stereo Vision System

The purpose of this project is to develop a mobile robot for hazardous terrain exploration. The exploration of hazardous terrain requires the development of a passive mechanism adaptable to such terrain and a sensing system for obstacle avoidance, as well as a remote control. We designed a new mobile robot, the Ronahz 6-wheel robot, which uses a passive mechanism that can adapt to hazardous terrains and building stairways without any active control. The suggested passive linkage mechanism consists of a simple four-bar linkage mechanism. In addition, we install a stereo vision system for obstacle avoidance, as well as a remote control. Wide dynamic range CCD cameras are used for outdoor navigation. A stereo vision system commonly requires high computational power. Therefore, we use a new high-speed stereo correspondence algorithm, triangulation, and iterative closest point (ICP) registration to reduce computation time. Disparity maps computed by a newly proposed, high-speed method are sent to the operator by a wireless LAN equipment. At the remote control site, a three-dimensional digital map around a mobile robot is built by ICP registration and reconstruction process, and this three-dimensional map is displayed for the operator. This process allows the operator to sense the environment around the robot and to give commands to the mobile robot when the robot is in a remote site.

A Systematic Method for Kinematics Synthesis of High-Speed Mechanisms With Optimally Integrated Smart Materials

2000 ◽  
Vol 124 (1) ◽  
pp. 14-20 ◽  
Author(s):  
J. Rastegar ◽  
L. Yuan
Keyword(s):  
Smart Materials ◽  
High Speed ◽  
Vibrational Excitation ◽  
High Harmonic ◽  
Harmonic Component ◽  
Linkage Mechanism ◽  
Output Link ◽  
Mechanism Synthesis ◽  
Systematic Method ◽  
Four Bar Linkage

A systematic method is presented for kinematics synthesis of high-speed mechanisms with optimally integrated smart materials based actuators for the purpose of modifying the output link motion. As an example, the method is applied to a four-bar linkage mechanism that is synthesized for function generation to eliminate the high harmonic component of the output link motion. For mechanisms with rigid links, the high harmonic motions are generated due to the nonlinearity of the kinematics of their closed-loop chains. By eliminating the high harmonic component of the output motion, the potential vibrational excitation that the mechanism can impart on the overall system and its own structure is greatly reduced. The resulting system should therefore be capable of operating at higher speeds and with greater precision. A numerical example is provided together with a discussion of the application of the method to other mechanism synthesis problems and some related topics of interest.

Automatic Selection of Mechanism Designs from a Three-Dimensional Design Map

1992 ◽  
Vol 114 (3) ◽  
pp. 359-367 ◽  
Author(s):  
S. Kota
Keyword(s):  
Selection Process ◽  
Three Dimensional ◽  
Quantitative Comparison ◽  
Linkage Mechanism ◽  
Computer Aided ◽  
Definite Pattern ◽  
Design Selection ◽  
Four Bar Linkage ◽  
Synthesis Approach ◽  
Selection Of

Often a simple (four-bar linkage) mechanism to trace a desired path is sought. Dimensions of linkages to trace a specified coupler curve exactly are difficult to determine. Precision point techniques do not guarantee that the desired path will be generated. The methodology presented in this paper is based on indirect synthesis approach to select four-bar linkages that trace a given desired path. A practical, computer-aided three-dimensional design chart for the selection of four-bar linkage candidate designs that trace symmetrical paths is presented. It is based on hypothesis that any arbitrary path can be approximated by a symmetrical path at least for the purpose of choosing an initial design. Four-bar linkages that generate symmetrical paths are easier to design and exhibit a definite pattern of changes in their shape as the linkage parameters are varied. General design categories and the corresponding solution subspaces in the 3-D design map are identified to aid in the selection of candidate designs. The automation of the design-selection process requires a satisfactory means to quantitatively compare the “desired” and the “known” coupler curves. This paper addresses the issues involved in quantitative comparison of two arbitrary curves using parameterization and shape evaluation. A design example of automated selection of mechanism designs is also presented.

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