Engineering topics

Ider, Sitki Kemal

Publications and source records attributed to Ider, Sitki Kemal.

4 records

NASA NTRS1989

Optimum control forces for multibody systems with intermittent motion

The objective is to address the continuity of motion when a dynamical system is suddenly subjected to constraint conditions. Motion discontinuity due to the initial constraint violation is avoided by prior control forces that adjust the motion and yield velocity and acceleration consistent at the point of application of the constraint. The optimum control forces are determined for a specified control interval. The method proposed provides an optimum adjustment of the system's motion and assures that the stresses developed at the system components are kept within acceptable limits. The procedures developed will be illustrated making use of inequality constraints applied to obstacle avoidance problems in robotics.

Ider, Sitki Kemal↗

NASA NTRS1989

Explicit modeling of composite plates and beams in the dynamics of multibody systems

The state of the art dynamic response analysis of flexible multibody systems is currently restricted to elastic bodies with homogeneous materials. The requirements for high speed operation has made it necessary to use lightweight multi layered composite bodies in robotic systems and space structure applications. Dynamic modeling and analysis of such systems are particularly important since the effects of body flexibility to the performance are likely to be more pronounced. The eight-noded isoperimetric quadrilateral element with independent rotational and displacement degrees of freedom is extended to laminated composite elements. The element includes an arbitrary number of bonded layers, each of which may have a different thickness. The transverse shear deformation which is a predominant factor in the analysis of laminated composite structures is taken into account in developing the stiffness and mass matrices. The corresponding 3-D mode shapes are then incorporated to the multibody system dynamical equations. Floating body reference frames allow the selection of different boundary conditions, and the dynamical equations contain all the nonlinear interactions between the rigid and elastic motion. Example simulations are presented to illustrate the methods proposed.

Amirouche, F. M. L.↗

NASA NTRS1989

Modeling of control forces for kinematical constraints in the dynamics of multibody systems: A new approach

Conventionally kinematical constraints in multibody systems are treated similar to geometrical constraints and are modeled by constraint reaction forces which are perpendicular to constraint surfaces. However, in reality, one may want to achieve the desired kinematical conditions by control forces having different directions in relation to the constraint surfaces. The conventional equations of motion for multibody systems subject to kinematical constraints are generalized by introducing general direction control forces. Conditions for the selections of the control force directions are also discussed. A redundant robotic system subject to prescribed end-effector motion is analyzed to illustrate the methods proposed.

Ider, Sitki Kemal↗

NASA NTRS1989

Determination of joint drives for stable end-effector motion in flexible robotic systems

The prescribed tasks in high speed robotic systems are severely deteriorated because of their manipulator dynamic deflections. On the other hand conventional dynamic modeling techniques fail to reveal appropriate control forces in flexible systems. The conventional dynamic equations of motion for systems subject to kinematical constraints are modified by a new concept of control force representation. The directions of the control forces are selected such that they correspond to the joint degrees of freedom. Then the joint control forces and torques that yield unperturbed prescribed motions are solved simultaneously with the system motion. A flexible manipulator is presented to illustrate the methods proposed.

Ider, Sitki Kemal↗