Hiroyuki Kojima

Optimal trajectory planning of a two-link flexible robot arm based on genetic algorithm for residual vibration reduction

The optimal trajectory planning method for residual vibration reduction of a two-link flexible robot arm is proposed. The two-link flexible robot arm consists of a first rigid link and a second flexible link. The first and second joint angular velocities are described by use of four cubic polynomial functions. Then, applying both the constraint conditions and the initial and final conditions of the joint angular velocities, the trajectory of the two-link flexible robot arm is expressed by use of the four unknown parameters. Then, the fitness function of the genetic algorithm for the residual vibration reduction of the second flexible link is defined using the four unknown parameters as the genes, and the optimal trajectory planning algorithm is constructed by use of the genetic algorithm. Furthermore, the numerical calculations and the experiments were carried out, and it is confirmed that the residual vibrations can be greatly reduced.

Transient vibrations of a beam/mass system fixed to a rotating body

Abstract Transient flexural vibrations of a beam/mass system fixed to a rotating body are investigated. The rotating body is driven so as to have a velocity profile of trapezoidal shape. The governing ordinary differential equations of the beam mass system are derived by use of the extended Galerkin method, and the transient response is obtained by the Laplace transformation. Then the effects of the flexibility of the beam and the rotational period of the rotating body upon the flexural vibrations are investigated.

Transient response of torsional feedback servomechanisms with consideration of vibration of shafts

Abstract This paper deals with a closed loop torsional position control system consisting of shafts and gear mechanisms. The dynamic response of the system has been investigated theoretically by application of the Laplace transform method. In the analysis the transformed equations for both electrical and mechanical systems have been expressed in a matrix form, and the solution has been determined directly by use of the residue theorem. The solution obtained gives the angles of rotation of the controlling body, gears, rotor, shafts and the torques of the shafts in the transient motion. An experimental test has been performed in order to assess the accuracy of the present solution.

Quasi-minimum time trajectory planning of electromagnetic attraction transfer robot arm using PTP motions

In this study, the quasi-minimum time trajectory planning method for the electromagnetic attraction transfer control of a magnetic object by use of a two-joint robot arm with an electromagnetic attraction hand is proposed. In the quasi-minimum time trajectory planning, the trajectory polynomial expression is derived by using the boundary and continuous conditions of joint angle, joint angle velocity, and the trajectory is expressed using three genes of genetic algorithm. Then, using three genes and the genetic algorithm and defining the fitness function for the quasi-minimum time trajectory, the quasi-minimum time trajectory planning algorithm is constructed. The fitness function is defined using two constraint conditions for the allowable maximum moment applied to the magnetic object and allowable rated DC motor torque. Furthermore, the numerical calculations and the experiments are demonstrated, and the usefulness of the present quasi-minimum time trajectory planning method is confirmed.

Vibration analysis and motion control of stand-up robot consisting of body link, arm link and leg link

In this study, first, the forced vibration response of a three -link stand-up robot is investigated theoretically. The stand-up robot consists of an arm link, a body link and a leg link. Considering the vibration analysis results, the trajec tory planning algorithm for the stand-up motion control by using a touch sensor attached to the body link is devised. In the stand-up motion control, initially, the vibrational swing motion co ntrol of the arm link starts. Then, immediately after the tim e when the touch sensor signal is on for the first time, the swing moti on control of the leg link starts, and after a brief interval, the vibrational swing motion control of the arm link finishes. Fu rthermore, the stand-up motion control system consisting of the trajectory planning and the joint angle tracking controlle r is constructed. Moreover, the experiments of the stand-up motion control have been carried out, and it is confirmed that the sta nd-up motion control could be well executed.

Position and Force Neuro-Adaptive Control of a Flexible Robot Arm.

This paper describes the position and force neuro-adaptive control of a two-link flexible robot arm. First, the equation of motion of the flexible robot arm consisting of the first rigid link and second flexible link is shown. The end of the second flexible link is constrained by a rgid wall. Second, the position and force neuro-adaptive control system is composed of two-layer neural networks and proportional feedback control loops. Furthermore, from the experimental results and the numerically simulated ones, it is confirmed that the control error of position and force with the neuro-adaptive control is markedly smaller than the control error without the neuro-adaptive control.

Finite element modeling and frequency response of a flexible rotating plate.

In this paper, the finite element modeling of a flexible rotating plate, in consideration of both the bending vibration and the rotating motion, is presented. The frequency responses of the system consisting of the flexible rotating plate and the rotating axis with a torsinal spring and damper are investigated. In the finite element modeling of the rotating flexible plate, the element mass matrix of the rectangular plate element modeling of the rotating flexible plate, the element mass matrix of the rectangular plate element modeling of the rotating flexible plate, the element mass matrix of the rectangular plate element is formulated by use of the shape function derived by Melsoh. This element mass matrix, consists of three parts that correspond to the bending vibration, the interaction between the bending vibration and the rotating motion, and the moment of inertia. By using the element mass matrix, the equation of motion is obtained. Furthermore, the effects of the rigidity of the torsional spring on the frequency responses are demonstrated.

Finite element analysis of forced vibrations of a rectangular plate subjected to electromagnetic force.

In this report, the forced vibrations of a rectangular plate subjected to electromagnetic force by an electromagnet are investigated theoretically by the finite element method, and the numerical results are compared with the experimental ones. The rectangular plate is fixed along one edge and free along the other three, and twelve rectangular elements are used in the finite element analysis. The electromagnetic force character is supposed to be uniformly proportional to the square of the exciting current of the electromagnet in each rectangular element according to the measured data about the magnetic flux density. The numerical results agree well with the experimental ones except for nonlinear vibration behaviors. Then, it is observed experimentally the the second order superharmonic and the one-second order subharmonic vibration s due to the nonlinearity of the electromagnetic force.

Effects of Torsional Vibrations on a Position Control System Consisting of a Servo-Mortar and a Magnetic Damper

磁気ダンパとサーボモータを用いた,コンピュータによるパルス信号制御の開ループ位置決め系を提示し,この系の妥当性を検討した.解析では軸振動の影響を考慮し,ばねと連続体についての両結果を誘導して両者の比較検討を行い,通常の制御速度でのばね系による解析の妥当性を明らかにした.また軸を剛体とした場合の結果を示して軸振動の影響を検討した.さらに軸の強度設計の観点から,軸のねじりモーメントを与える式をも示した.