Ahmet Sagirli

Modeling the Dynamics and Kinematics of a Telescopic Rotary Crane by the Bond Graph Method: Part II

Cranes employed for load transfer are large volume machines and canbe designed to accomplish linear, planar or spatial motions dependingon the intended use. Understanding the dynamic behavior of thesesystems, which have a load-carrying capacity of hundreds of tonnes, ishighly noteworthy for system design, control, and work safety. Inthis study, a theoretical model of a spatially actuated telescopic rotarycrane is obtained with provided assumptions using Bond Graph techniques.Following the modeling of an actuation system and of a main structure,unification of these two is accomplished. Since the overall system consistsof high nonlinearity originating from geometric nonlinearity, gyroscopicforces, hydraulic compressibility, and elastic boom structure, the resultingderivative causality problem caused by rigidly coupled inertia elementsis addressed for this highly nonlinear system and consequential systemstate-space equations are presented.

Investigation of the Dynamic Behaviors of Cranes under Seismic Effects with Theoretical and Experimental Study

This paper is concerned with investigation of the dynamic behaviors of cranes under seismic effects. For this purpose, firstly we have performed experiment on a 1/20 scale crane model on the shake table with real earthquake data, then a multi degree-of-freedom non-linear mathematical model is developed including behavior of the container cranes under earthquakes and simulated. The simulation system has a five degrees-of-freedom and modeled system was simulated for the ground motion of the El Centro earthquake in USA, 1940. Finally, the time history of the crane bridge displacement and acceleration responses of the both theoretical and experimental cases are presented. Theoretical and experimental results exhibit that the mathematical model is accurate. This study also shows the destructive effects of high accelerations which occur during the earthquake. These effects cannot be omitted in the design of cranes. The result of this study which is an accurate mathematical model can be inspiring for the engineers in terms of design parameters.

Investigation of Seismic Behavior of Container Crane Structures by Shake Table Tests and Mathematical Modeling

This paper is concerned with the verification of mathematical modeling of the container cranes under earthquake loadings with shake table test results. Comparison of the shake table tests with the theoretical studies has an important role in the estimation of the seismic behavior of the engineering structures. For this purpose, a new shake table and mathematical model were developed. Firstly, a new physical model is directly fixed on the shake table and the seismic response of the container crane model against the past earthquake ground motion was measured. Secondly, a four degrees-of-freedom mathematical model is developed to understand the dynamic behaviour of cranes under the seismic loadings. The results of the verification study indicate that the developed mathematical model reasonably represents the dynamic behaviour of the crane structure both in time and frequency domains. The mathematical model can be used in active-passive vibration control studies to decrease structural vibrations on container cranes.

A novel visualization technique in Bond-Graph method for modeling of a generalized stewart platform

This paper represents dynamic modeling of generalized stewart platform manipulator by Bond Graph method with a new spatial visualization method and the state-space representation of the dynamic equations of the system. Dynamic model includes all the dynamics and gravity effects, linear motor dynamics as well as the viscous friction at the joints. Following modeling of actuation system and of main structure, unification of these two is accomplished. Linear DC motors are utilized and modelled as the actuation system. Since overall system consists of high nonlinearity originated from geometric nonlinearity and gyroscopic forces, resultant derivative causality problem caused by rigidly coupled inertia elements is addressed and consequential system state-space equations are presented.

Active Vibration Control of Container Cranes against Earthquake by the Use of LMI Based Mixed State-Feedback Controller

This paper studies the design of a linear matrix inequality (LMI) based mixed state-feedback controller for vibration attenuation problem of seismic-excited container cranes. In order to show effectiveness of the designed controller, a six-degree-of-freedom container crane structural system is modeled using a spring-mass-damper subsystem. The system is then simulated against the real ground motion of El Centro and Northridge earthquakes. Finally, the time history of the crane parts displacements, accelerations, control forces, and frequency responses of both uncontrolled and controlled cases are presented. Additionally, the performance of the designed controller is also compared with a nominal state-feedback controller performance. Simulations of the designed controller show better seismic performance than a nominal state-feedback controller. Simulation results show that the designed controller is all effective in reducing vibration amplitudes of crane parts.

Nonlinear state-space representations of a quadrotor through bond-graph technique

Obtaining efficient dynamic equations of complex systems, like processes or robotic systems, are very important for control system design. While various forms of acquiring motion equations exist, state-space form has its advantages for analyzing complex systems. Among analytical and graphical techniques of finding dynamic behavior of a system, bond-graph provides straight forward way of serving linear/nonlinear equations of systems in state-space form. In this study, a four-propeller-actuated full/reduced order quadrotor spatial dynamics are investigated by using bond-graph technique. Full order dynamic behavior is obtained including motor, gear, shaft, propellers and the body. Additionally, neglecting motor dynamics, reduced order state-space representations of the system is also provided, assuming force/moment input and propeller speed as inputs to the vehicle separately. Responses of the models are compared and discussed.

A stewart platform as a FBW flight control unit for space vehicles

A variety of flight control units have been put into realization for navigational purposes of spatially moving vehicles, which is mostly manipulated by 2–3 degrees-of-freedom (DOF) joysticks. Since motion in space consists of three translational motions in forward, side and vertical directions and three rotational motions about these axis; with present joystick interfaces, spatial vehicles has to employ more than one navigational control unit to be able to navigate on all required directions. In this study, a 3×3 Stewart-Platform-based FBW (Fly-By-Wire) flight control unit with force feedback is presented which will provide single point manipulation of any space vehicle performing spatial motions along three translational and three rotational axis. Within the frame of this paper, design, capability and the advantages of the novel system is mentioned. Kinematics of the Stewart Platform (SP) mechanism employed and its motion potentials is presented by simulations and workspace of the system is evaluated. Dynamic analysis by Bond-Graph approach will be mentioned. Mechatronic design of the complete structure is discussed and force reflection capability of the system with simulations is pointed out using stiffness control. Finally, the possible future work of the subject is discussed which may include the feasible solutions of the SP in terms of size and safety when implementing inside a cockpit.