※一部利用できない機能があります
| 1.
論文 |
論文
|
丸山, 真一 ; 永井, 健一 ; 山口, 誉夫 ; 加藤, 考行
概要:
application/pdf<br />Journal Article<br />Numerical results are presented on chaotic vibrations of a cantilevered beam u
…
nder vibroimpact. The analytical model consists of a cantilevered beam, subjected to periodic excitation, and a bar that restrains the amplitude of the beam. Equation of the motion of the beam is discretised by the finite element method and impacts of the beam are computed by using the coefficient of restitution rule. Time responses of the beam are calculated with direct integration by the Newmark-β method. Then the responses are inspected with the frequency response curves, the Fourier spectra, the Lyapunov exponents and the principal component analysis. The numerical results are compared with the experimental results that are previously presented by the authors, which verify our numerical results. Effects of the location of the bar and of the clearance between the bar and the beam on the chaotic responses are examined by the numerical results. As the location of the bar becomes farther from the clamped end and the clearance becomes smaller, the frequency region of the impact vibration is enlarged. The chaotic responses of the beam generally have contribution ratio of higher vibration modes less than 5%. However, when the location of the impact is close to a node of a higher mode or super-harmonic resonance of a higher mode is excited, contribution of the higher mode increases up to 10% to 30%.
続きを見る
|
||
| 2.
論文 |
論文
|
丸山, 真一 ; 加藤, 考行 ; 永井, 健一 ; 山口, 誉夫
概要:
application/pdf<br />Journal Article<br />Experimental results are presented on chaotic vibrations of a cantilevered beam under vibroimpact. A rigid bar that is located close to the free end of the beam limits the amplitude of the beam under
…
lateral periodic acceleration, and then asymmetric vibroimpacts are induced. In the frequency region of the impact vibration near the fundamental resonance of the lowest mode, two regions of chaotic responses are observed. There is one impact in an excitation cycle in the higher frequency region of the chaos, while occurrence of impacts in the lower frequency region is less frequent than the former one. The maximum Lyapunov exponent of the chaotic response in the higher frequency region takes higher value than that of the chaos in the lower frequency. Mode contributions to the chaos are inspected by the principal component analysis. The lowest mode of vibration prevails in the vibroimpacting response. In the regions of the chaos, contribution of the second mode of vibration to the chaotic responses increases up to 5%. As the exciting frequency is increased, the contribution of the second vibration mode to the chaos becomes larger owing to the increase in the amplitude of impact vibration. Furthermore, contribution of the second vibration mode drastically increases as the super-harmonic resonance of the second mode is generated. The maximum Lyapunov exponent increases as the contribution of the second mode increases, which implies the close relation between the complexity of the chaotic responses and the participation of the higher modes of vibration.
続きを見る
|
||
| 3.
論文 |
論文
|
山口, 誉夫 ; 中原, 直人 ; 永井, 健一 ; 丸山, 真一 ; 藤井, 雄作
概要:
application/pdf<br />Journal Article<br />This paper describes vibration analysis using finite element method for elastic blocks connected by a nonlinear concentrated spring. The restoring force of the spring is assumed to be
…
expressed by power series of the relative displacement between ends of the spring. Finite element for the nonlinear spring is expressed and is connected to the elastic blocks modeled by linear solid finite elements. Further, the discretized equations in physical coordinate are transformed into the nonlinear ordinary coupled equations using normal coordinate corresponding to linear natural modes. This transformation yields computation efficiency. Influences of Young's modulus on nonlinear frequency responses for the elastic block are clarified.
続きを見る
|
||
| 4.
論文 |
論文
|
丸山, 真一 ; 永井, 健一 ; 服部, 伯慕 ; 山口, 誉夫
概要:
application/pdf<br />Journal Article<br />Analytical results are presented on chaotic vibrations of a shallow arch with initial configuration of catenary. The shallow arch is simply supported at both ends and is subjected to periodic
…
lateral force. Equations of motion are reduced to ordinary differential equations of multiple-degree-of-freedom system by the Galerkin procedure. To clarify effects of sag-to-span ratio on chaotic motions, first, steady-state responses are calculated by the harmonic balance method. The chaotic responses are obtained by numerical integration and are examined by Poincare projection, the maximum Lyapunov exponent and bifurcation diagrams. For the arch with comparatively small sag-to-span ratio, chaotic vibrations are generated mainly in the regions of subharmonic resonance of 1/3 order and of ultra-subharmonic resonance of 3/2 order, accompanied by the lowest-symmetric-mode of vibration. As the sag-to-span ratio increases, chaotic responses are generated from the subharmonic resonances both of 1/2 and 1/3 orders. Furthermore, chaotic motion appears within a wider range of exciting frequency and the number of modes that contribute to the chaos increases. Period doubling bifurcation was mainly observed in the bifurcation from periodic responses to chaotic ones. Hopf bifurcation was also found for the arch that satisfies the condition of internal resonance.
続きを見る
|
||
| 5.
論文 |
論文
|
山口, 誉夫 ; 中原, 直人 ; 永井, 健一
概要:
application/pdf<br />Journal Article<br />This paper describes vibration analysis using finite element method for an elastic block supported by a nonlinear concentrated spring. This block is connected to another block by a
…
linear concentrated spring. The restoring force of the nonlinear spring has cubic nonlinearity. In this system, resonance responses mainly involve nonlinearity due to two vibration modes. Finite element for the nonlinear spring is expressed. Then the nonlinear spring element and linear spring element are combined to the elastic blocks modeled by linear solid finite elements. Further, the discretized equations in physical coordinate are transformed into the nonlinear ordinary coupled differential equations using normal coordinate corresponding to linear natural modes. This transformation yields computation efficiency. Influences of Young's modulus on frequency responses are clarifed.
続きを見る
|
||
| 6.
論文 |
論文
|
山口, 誉夫 ; 永井, 健一 ; 丸山, 真一 ; 油田, 知宏
概要:
application/pdf<br />Journal Article<br />This paper describes vibration analysis using finite element method for an elastic block supported by a nonlinear concentrated spring. The restoring force of the spring has cubic
…
nonlinearity. Finite element for the nonlinear spring is expressed and is connected to the elastic block modeled by linear solid finite elements. Further, the discretized equations in physical coordinate are transformed into the nonlinear ordinary coupled equations using normal coordinate corresponding to linear natural modes. This transformation yields computation efficiency. Influences of Young's modulus on nonlinear frequency responses for the elastic block are clarified.
続きを見る
|
||
| 7.
論文 |
論文
|
永井, 健一 ; 鈴木, 央 ; 山口, 誉夫 ; 丸山, 真一
概要:
application/pdf<br />Journal Article<br />Analytical result is presented on chaotic oscillations of a buckled beam under an axial spring. The beam with a concentrated mass is clamped at both ends. The beam is compressed to the
…
post-buckled configuration by the axial spring. The beam is subjected to periodic lateral acceleration. Introducing a mode shape function to a basic equation, nonlinear ordinary differential equations of multiple-degree-of-freedom system is reduced to by the Galerkin procedure. Changing a stiffness of the axial spring, an internal resonance condition of one to two is selected. First, steady-state resonance responses are calculated by the harmonic balance method. The chaotic responses are obtained by a numerical integration. The chaotic responses are examined by the Poincare projection, the maximum Lyapunov exponent and bifurcation diagrams. The chaos due to the internal resonance is easily generated by a small amplitude of excitation. As the exciting frequency decreased, transition to the chaos from a periodic response needs larger amplitude of excitation. In a lower range of frequency, the chaotic oscillations are mixed with the internal resonance and the dynamic snap buckling. Two modes of vibration contribute to the chaos related to the internal resonance. Number of the modes increases more than three for the chaos involved the dynamic snap buckling.
続きを見る
|
||
| 8.
論文 |
論文
|
小島, 宏行
概要:
application/pdf<br />Journal Article<br />This study is concerned with the trajectory planning method of a CP control flexible robot arm by using a genetic algorithm. The flexible robot arm consists of a first rigid link and a second
…
flexible link, and the desired trajectory is set to be a straight line. In the trajectory planning, the reference trajectory, as if the flexural displacement of the second flexible link is zero, is expressed by use of a cubic spline function, and the velocity profile in the direction of the desired trajectory is depicted using two fifth-order polynomial functions. The individual chromosome of the genetic algorithm is composed using the parameters of the cubic spline function and the fifth-order polynomial functions as the genes. Then, the fitness function of the individual chromosome for the residual vibration reduction and the trajectory tracking control is defined, and the trajectory planning algorithm is constructed using the genetic algorithm. Furthermore, the numerical calculations have been carried out, and it is confirmed that the residual vibrations can be remarkably reduced, and the trajectory error from the desired trajectory can be considerably reduced.
続きを見る
|
||
| 9.
論文 |
論文
|
小島, 宏行 ; 戸塚, 輝成 ; 近藤, 厚哉
概要:
application/pdf<br />Journal Article<br />In this report, the rotation control system of the flexible robot arm is constructed with both the desired signal planning algorithm of the joint angle and the tracking controller. The tracking
…
controller consists of the PD controller and the disturbance observer. Then, the experiments of the rotation control of the flexible robot arm have been carried out. As the results, it is seen that the residual vibrations of the flexible robot arm can be remarkably reduced. Therefore, the usefulness of the present rotation control system of the flexible robot arm using the desired signal planning method of the joint angle and the disturbance observer is confirmed experimentally.
続きを見る
|
||
| 10.
論文 |
論文
|
小島, 宏行
概要:
application/pdf<br />Journal Article<br />In this report, first, the nonlinear equations of motion of a horizontal one-link flexible robot arm are obtained by use of the mode functions of a cantilever beam with a mass. Then, the algorithm
…
of the desired signal planning of the joint angle for the purpose of the reduction control of residual vibrations of the flexible robot arm is derived by use of the initial and final conditions of the flexural displacement of the flexible link and the constraint conditions of the desired signal of the joint angle during the acceleration and deceleration terms as well as the linearized equation of motion of the flexible robot arm. The rotation control system of the flexible robot arm is constructed with the desired signal planning for the joint angle and the PD controller. Furthermore, the numerical simulations of the rotation control of the flexible robot arm have been carried out, and it is confirmed that the residual vibrations of the flexible robot arm can be effectively reduced by the present desired signal planning for the joint angle.
続きを見る
|
