The use of accelerometry to evaluate the BMX cycling starting hill. Effect of the Q-Ring™ on the acceleration profile

2020 ◽  
pp. 1-15
Author(s):  
Jose L. L. Elvira ◽  
Manuel Mateo-March ◽  
Mikel Zabala ◽  
Cristina Blasco-Lafarga
Keyword(s):  
1994 ◽  
Author(s):  
Hironori Fujii ◽  
Masayuki Nakagawa ◽  
Hirofumi Hatakenaka

Author(s):  
Khaled A. Alghanim ◽  
Khaled A. Alhazza ◽  
Ziyad N. Masoud

An optimization strategy to reduce residual vibration of rest-to-rest maneuvers of overhead cranes is proposed. The proposed technique is based on generating shaped acceleration commands for a simple harmonic oscillator with damping included. Furthermore, the proposed technique solves the problem of discrete signal commands that result from using slow digital to analog convertors on real cranes. A discretized acceleration profile is derived analytically using finite step segments. These segments are integrated into a matrix, which is then coupled with a system response matrix through the system’s equations of motion. The resulting input acceleration matrix is then optimized to satisfy rest-to-rest maneuver conditions. The profile designer can control many parameters such as maneuver duration, discrete time step, hoisting speed, damping ratio, maximum velocity and acceleration. Unlike traditional command shapers, the proposed shaped profiles are independent of the natural period of the system, i.e., the acceleration profile duration is designer selectable. Through several examples, the performance of the proposed controller is validated numerically. Results show that the proposed shaping technique can effectively eliminate residual vibrations in rest-to-rest maneuvers of damped single-degree-of-freedom systems.


2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Hongtai Cheng ◽  
Wei Li

Delta robot is typically mounted on a frame and performs high speed pick and place tasks from top to bottom. Because of its outstanding accelerating capability and higher center of mass, the Delta robot can generate significant frame vibration. Existing trajectory smoothing methods mainly focus on vibration reduction for the robot instead of the frame, and modifying the frame structure increases the manufacturing cost. In this paper, an acceleration profile optimization approach is proposed to reduce the Delta robot-frame vibration. The profile is determined by the maximum jerk, acceleration, and velocity. The pick and place motion (PPM) and resulting frame vibration are analyzed in frequency domain. Quantitative analysis shows that frame vibration can be reduced by altering those dynamic motion parameters. Because the analytic model is derived based on several simplifications, it cannot be directly applied. A surrogate model-based optimization method is proposed to solve the practical issues. By directly executing the PPM with different parameters and measuring the vibration, a model is derived using Gaussian Process Regression (GPR). In order to reduce the frame vibration without sacrificing robot efficiency, those two goals are fused together according to their priorities. Based on the surrogate model, a single objective optimization problem is formulated and solved by Genetic Algorithm (GA). Experimental results show effectiveness of the proposed method. Behavior of the optimal parameters also verifies the robot-frame vibration mechanism.


2018 ◽  
Vol 19 (2) ◽  
pp. 201-211 ◽  
Author(s):  
Leland Barker ◽  
Bryan Burnstein ◽  
John Mercer

1966 ◽  
Vol 6 (6) ◽  
pp. 756-766
Author(s):  
JOHN H. HENZEL ◽  
JAMES W. BRINKLEY ◽  
GEORGE C. MOHR
Keyword(s):  

2000 ◽  
Vol 27 (3) ◽  
pp. 533-542 ◽  
Author(s):  
Mohamed A Khedr ◽  
Ghyslaine McClure

A simplified static method for estimating the member forces in self-supporting lattice telecommunication towers due to both horizontal and vertical earthquake excitations is presented in this paper. The method is based on the modal superposition technique and the response spectrum approach, which are widely used for seismic analysis of linear structures. It is assumed that the lowest three flexural modes of vibration are sufficient to correctly estimate the tower's response to horizontal excitation, while only the lowest axial mode is sufficient to capture the response to vertical excitation. An acceleration profile along the height of the tower is defined using estimates of the lowest three flexural modes or the lowest axial mode, as appropriate, together with the spectral acceleration values corresponding to the associated natural periods. After the mass of the tower is calculated and lumped at the leg joints, a set of equivalent static lateral or vertical loads can be determined by simply multiplying the mass profile by the acceleration profile. The tower is then analyzed statically under the effect of these loads to evaluate the member forces. This procedure was developed on the basis of detailed dynamic analysis of ten existing three-legged self-supporting telecommunication towers with height range of 30-120 m. The maximum differences in member forces obtained with the proposed method and the detailed seismic analysis are of the order of ±25% in the extreme cases, with an average difference of ±7%. The results obtained for two towers with heights of 66 and 83 m are presented in this paper to demonstrate the accuracy and practicality of the proposed method.Key words: self-supporting tower, earthquake, vertical excitation, dynamic analysis.


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