scholarly journals A new graphical technique for acceleration analysis of four bar mechanisms using the instantaneous center of zero acceleration

2021 ◽  
Vol 3 (3) ◽  
Author(s):  
Nadim Diab
Keyword(s):  
Angular Acceleration ◽  
Graphical Technique ◽  
Acceleration Analysis ◽  
Instantaneous Center

AbstractIn this work, a new graphical technique is furnished for acceleration analysis of four bar mechanisms through locating the instantaneous center of zero acceleration $$IC_{a}$$ I C a of the coupler link. First, the paper observes the coupler’s $$IC_{a}$$ I C a locus and then proceeds with a series of graphical constructions that eventually lead into locating the $$IC_{a}$$ I C a and obtaining the linear/angular accelerations of the coupler and follower (or slider) links. Based on the proposed graphical technique, the ease of acceleration analysis for four-bar mechanisms with varying driver’s angular acceleration is demonstrated. Simultaneously, the inflection circle of the coupler curve is constructed without the need to apply Euler-Savary equations. With fewer constructions than classical graphical techniques, the robustness and simplicity of the proposed method are demonstrated by performing acceleration analysis of a slider-crank (RRRP) and a planar quadrilateral linkage (RRRR).

A New Approach for Locating the Instantaneous Centers of Zero Velocity for 1-DOF Planar Linkages

2018 ◽  
Author(s):  
Nadim Diab
Keyword(s):  
Degree Of Freedom ◽  
Planar Mechanisms ◽  
New Approach ◽  
Zero Velocity ◽  
Graphical Technique ◽  
Instantaneous Center ◽  
Planar Linkages ◽  
Consistent Approach

This paper presents a new graphical technique to locate the secondary instantaneous centers of zero velocity (ICs) for one-degree-of-freedom (1-DOF) kinematically indeterminate planar mechanisms. The proposed approach is based on transforming the 1-DOF mechanism into a 2-DOF counterpart by converting any ground-pivoted ternary link into two ground-pivoted binary links. Fixing each of these two new binary links, one at a time, results in two different 1-DOF mechanisms where the intersection of the loci of their instantaneous centers will determine the location of the desired instantaneous center for the original 1-DOF mechanism. This single and consistent approach proved to be successful in locating the ICs of various mechanisms reported in the literature that required different techniques to reach the same results obtained herein.

Interjoint dynamic interaction during constrained human quiet standing examined by induced acceleration analysis

2014 ◽  
Vol 111 (2) ◽  
pp. 313-322 ◽  
Author(s):  
Shun Sasagawa ◽  
Masahiro Shinya ◽  
Kimitaka Nakazawa
Keyword(s):  
Motor Performance ◽  
Angular Acceleration ◽  
Quiet Standing ◽  
Hip Joints ◽  
Dynamic Interactions ◽  
Temporal Relationships ◽  
The Central Nervous System ◽  
Acceleration Analysis ◽  
The Individual ◽  
The Relationship

Recent studies have demonstrated that human quiet standing is a multijoint movement, whereby the central nervous system (CNS) is required to deal with dynamic interactions among the joints to achieve optimal motor performance. The purpose of this study was to investigate how the CNS deals with such interjoint interaction during quiet standing by examining the relationship between the kinetics (torque) and kinematics (angular acceleration) within the multi-degree of freedom system. We modeled quiet standing as a double-link inverted pendulum involving both ankle and hip joints and conducted an “induced acceleration analysis.” We found that the net ankle and hip torques induced angular accelerations of comparable magnitudes to the ankle (3.8 ± 1.4°/s2 and 3.3 ± 1.2°/s2) and hip (9.1 ± 3.2°/s2 and 10.5 ± 3.5°/s2) joints, respectively. Angular accelerations induced by the net ankle and hip torques were modulated in a temporally antiphase pattern to one another in each of the two joints. These quantitative and temporal relationships allowed the angular accelerations induced by the two net torques to countercompensate one another, thereby substantially (∼70%) reducing the resultant angular accelerations of the individual joints. These results suggest that, by taking advantage of the interjoint interaction, the CNS prevents the net torques from producing large amplitudes of the resultant angular accelerations when combined with the kinematic effects of all other torques in the chain.

Method for Determining the Instantaneous Center of Acceleration for a Given Link

1965 ◽  
Vol 32 (1) ◽  
pp. 217-218
Author(s):  
R. W. Schiller
Keyword(s):  
Acceleration Analysis ◽  
Instantaneous Center ◽  
The Given

A method using the inflection circle is presented which extends the use of the Joukowski theorem and permits the determination of the instantaneous center of acceleration of a link without a complete acceleration analysis of the given mechanism.

The Radius of Curvature of a Coupler Curve of the Single Flier Eight-Bar Linkage

2003 ◽  
Author(s):  
Gordon R. Pennock ◽  
Edward C. Kinzel
Keyword(s):  
Radius Of Curvature ◽  
Operating Speed ◽  
Velocity Analysis ◽  
Zero Velocity ◽  
Original Contribution ◽  
Graphical Technique ◽  
Curvature Theory ◽  
Instantaneous Center ◽  
Insight Into ◽  
Geometric Effects

The paper begins with a graphical technique to locate the pole; i.e., the point in the plane of motion which is coincident with the instantaneous center of zero velocity of the coupler link. Since the single flier linkage is indeterminate, the Aronhold-Kennedy theorem cannot locate this instantaneous center of zero velocity. The technique that is presented here is believed to be an original contribution to the kinematics literature and will provide geometric insight into the velocity analysis of an indeterminate linkage. The paper then presents an analytical method, referred to as the method of kinematic coefficients, to determine the radius of curvature and the center of curvature of the path traced by an arbitrary coupler point of the single flier eight-bar linkage. This method has proved useful in curvature theory since it separates the geometric effects of the linkage from the operating speed of the linkage.

scholarly journals Is Acceleration a Valid Proxy for Injury Risk in Minimal Damage Traffic Crashes? A Comparative Review of Volunteer, ADL and Real-World Studies

2021 ◽  
Vol 18 (6) ◽  
pp. 2901
Author(s):  
Paul S. Nolet ◽  
Larry Nordhoff ◽  
Vicki L. Kristman ◽  
Arthur C. Croft ◽  
Maurice P. Zeegers ◽  
...  
Keyword(s):  
Real World ◽  
Injury Risk ◽  
Angular Acceleration ◽  
Traffic Crashes ◽  
Rear Impact ◽  
Comparative Review ◽  
Minimal Damage ◽  
Injury Causation ◽  
Crash Tests ◽  
Biomechanical Approach

Injury claims associated with minimal damage rear impact traffic crashes are often defended using a “biomechanical approach,” in which the occupant forces of the crash are compared to the forces of activities of daily living (ADLs), resulting in the conclusion that the risk of injury from the crash is the same as for ADLs. The purpose of the present investigation is to evaluate the scientific validity of the central operating premise of the biomechanical approach to injury causation; that occupant acceleration is a scientifically valid proxy for injury risk. Data were abstracted, pooled, and compared from three categories of published literature: (1) volunteer rear impact crash testing studies, (2) ADL studies, and (3) observational studies of real-world rear impacts. We compared the occupant accelerations of minimal or no damage (i.e., 3 to 11 kph speed change or “delta V”) rear impact crash tests to the accelerations described in 6 of the most commonly reported ADLs in the reviewed studies. As a final step, the injury risk observed in real world crashes was compared to the results of the pooled crash test and ADL analyses, controlling for delta V. The results of the analyses indicated that average peak linear and angular acceleration forces observed at the head during rear impact crash tests were typically at least several times greater than average forces observed during ADLs. In contrast, the injury risk of real-world minimal damage rear impact crashes was estimated to be at least 2000 times greater than for any ADL. The results of our analysis indicate that the principle underlying the biomechanical injury causation approach, that occupant acceleration is a proxy for injury risk, is scientifically invalid. The biomechanical approach to injury causation in minimal damage crashes invariably results in the vast underestimation of the actual risk of such crashes, and should be discontinued as it is a scientifically invalid practice.

Irreversible deformation of a rotating disk having angular acceleration

2021 ◽  
Author(s):  
A. S. Begun ◽  
A. A. Burenin ◽  
L. V. Kovtanyuk ◽  
A. N. Prokudin
Keyword(s):  
Angular Acceleration ◽  
Rotating Disk ◽  
Irreversible Deformation

Assist Timing Decision Method for Wire Type Walking Assist Suit by Hip Joint Angular Acceleration

2020 ◽  
Author(s):  
Junyuan Zhang ◽  
Hiroumi Murai ◽  
Akihito Ito ◽  
Nobutaka Tsujiuchi ◽  
Tsuyoshi Inoue ◽  
...  
Keyword(s):  
Hip Joint ◽  
Angular Acceleration ◽  
Decision Method ◽  
Timing Decision

scholarly journals Aerodynamic characteristics of a free-flight scramjet vehicle in shock tunnel

2021 ◽  
Vol 62 (7) ◽  
Author(s):  
Marie Tanno ◽  
Hideyuki Tanno
Keyword(s):  
System Analysis ◽  
Force Measurement ◽  
Prediction Interval ◽  
Angular Acceleration ◽  
Aerodynamic Characteristics ◽  
Measurement Precision ◽  
Shock Tunnel ◽  
Free Flight ◽  
Vehicle Model ◽  
Aerodynamic Test

Abstract A multi-component aerodynamic test for an airframe-engine integrated scramjet vehicle model was conducted in the free-piston shock tunnel HIEST. A free-flight force measurement technique was applied to the scramjet vehicle model named MoDKI. A new method using multiple piezoelectric accelerometers was developed based on overdetermined system analysis. Its unique features are the following: (1) The accelerometer’s mounting location can be more flexible. (2) The measurement precision is predicted to be improved by increasing the number of accelerometers. (3) The angular acceleration can be obtained with single-axis translational accelerometers instead of gyroscopes. (4) Through the averaging process of the multiple accelerometers, model natural vibration is expected to be mitigated. With eight model-onboard single-axis accelerometers, the three-component aerodynamic coefficients (Drag, Lift, and Pitching moment) of MoDKI were successfully measured at the angle of attack from 0.7 to 3.4 degrees under a Mach 8 free-stream test flow condition. A linear regression fitting revealed a 95% prediction interval as the measurement precision of each aerodynamic coefficient. Graphical abstract

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