Hira Karagülle

Simulation and analysis of vibration signals generated by rolling element bearing with defects

Abstract Dynamic loading of a rolling element bearing structure is modeled by a computer program developed in Visual Basic programming language. The vibration response of the structure to the dynamic loading is obtained using a standard finite element package I-DEAS. A force model is proposed to model the localized rolling element bearing defects. Time and frequency domain analyses are performed for diagnostics of rolling element bearing structures. Statistical properties of the vibration signals for healthy and defected structures are compared. The envelope (HFRT) method is employed in the frequency domain analysis. The effect of the rotational speed on the diagnostics of rolling element bearing defects is investigated. An optimum sensor location on the structure is sought. Effect of the structure geometry on the monitoring techniques is studied. An optimum monitoring method can be employed by analyzing the rolling element bearing structure following the procedure proposed in this study. The present commercial computer aided engineering packages can be used in special engineering applications such as condition monitoring of rolling element bearings.

Analysis of active vibration control in smart structures by ANSYS

It is possible to model smart structures with piezoelectric materials using the product ANSYS/Multiphysics. In this study, the integration of control actions into the ANSYS solution is realized. First, the procedure is tested on the active vibration control problem with a two-degrees of freedom system. The analytical results obtained by the Laplace transform method and by ANSYS are compared. Then, the smart structures are studied by ANSYS. The input reference value is taken as zero in the closed loop vibration control. The instantaneous value of the strain at the sensor location at a time step is subtracted from zero to find the error signal value. The error value is multiplied by the control gain to calculate the voltage value which is used as the input to the actuator nodes. The process is continued with the selected time step until the steady-state value is approximately reached. The results are obtained for the structures analyzed in other studies. The active vibration control of a circular disc is also studied.

Vibration control of a two-link flexible manipulator

In this study, a two-link manipulator with flexible members is considered. The end point vibration signals are simulated by developing a MatLAB code based on the finite element theory and Newmark solution. Experimental results are also presented and compared with simulation results. The mass and stiffness matrices are time dependent because the angular positions of the links change during the motion. Trapezoidal velocity profiles for the actuating motors are used. The time dependent inertia forces are calculated by using the rigid body dynamics. The inertia forces are due to the motors, end point payload mass and distributed masses of the links. The acceleration, constant velocity and deceleration time intervals of the trapezoidal velocity profile are selected by considering the lowest natural frequency of the manipulator structure at the stopping position. Various starting and stopping positions are considered. The root mean square (RMS) acceleration values of the vibration signals after stopping are calculated. It is observed that the residual vibration is sensitive to the deceleration time. The RMS values are lowest if the inverse of the deceleration time equals to the first natural frequency. It is highest if the inverse of the deceleration time equals to the half of the first natural frequency. It is observed that simulation and experimental results are in good agreement.

Original article: An integrated approach for simulation of mechatronic systems applied to a hexapod robot

Mechatronics is the integration of mechanism, electronics and computer control to produce a functional system. The design process involves application of many engineering areas and various approaches are possible. Computer programs are available in different engineering areas. Engineers define systems and inputs, and user-friendly programs establish mathematical models, solve them and give simulation outputs. In this study, SolidWorks is used for solid modeling and assembly, CosmosMotion is used for rigid body dynamics, CosmosWorks is used for finite element vibration and strength analyses, and Adlink module is used for actuator control. The integration of the design process is achieved with a main program developed in Visual Basic, which uses the application programming interface (API) capabilities. The procedure is applied to a hexapod robot. The robot has been produced to develop and test the procedure. CosmosMotion results are verified by the analytical results obtained from the dynamic equations of the hexapod. Besides known kinematic workspace definition of robots, kinetic and rigidity workspace concepts are introduced. Mechatronic systems can be designed and evaluated easily and effectively by using the design process developed in this work.

Residual vibration control of a single-link flexible curved manipulator

Abstract Residual vibrations occur after stopping the movement of flexible manipulators. Accuracy at the end-point positioning decreases if residual vibration amplitudes increase. Productivity decreases in the high speed applications since the settling time required for this residual vibration delays subsequent operations. In this study, the vibration control of single-link flexible manipulators with a payload is studied numerically and experimentally. The mathematical model of a planar manipulator is established by the finite element method (FEM). Then, the transient analysis is realized by the Newmark method. The FEM results are verified by the simulation results obtained ANSYS and experiment. Then, a curved manipulator is studied by ANSYS as the Newmark solution is not valid. Simulation results also are verified by experiments. Cases for different stopping positions and motion times are created using the trapezoidal and triangular velocity profiles. The time parameters of these motion profiles based on the first natural frequency of the manipulators are determined for the vibration control. The root mean square values calculated from the residual vibration signals, and reduction ratios are presented for the cases. It is observed from the results that the residual vibration amplitudes of the manipulators are successfully suppressed by selecting appropriate deceleration times.

Analysis of active vibration control of multi-degree-of-freedom flexible systems by Newmark method

Abstract A flexible robot arm can be modeled as a lumped-parameter multi-degree-of-freedom mass–spring system. The actuator at one end positions the payload at the other end. The flexibility causes the vibration of the payload at the end point. This paper considers a 4-degree-of-freedom mass–spring system. A closed loop active vibration control system is analyzed to suppress the end-point vibrations. The mathematical model of the system is established by using the Lagrange equations. The average of the displacements of the masses is used for the feedback. A PID control is applied. The numerical solution is obtained by integrating the control action into the Newmark method. The instantaneous average displacement is subtracted from the reference input to find the error signal value at a time step in the Newmark solution. The PID control action is applied to find the actuator signal value in the time step. This input value is used to find the displacements for the subsequent time step. The process is continued until the steady-state value is approximately reached. The analytical solution is given by using the Laplace transform method to check the validity of the Newmark solution. It is observed that the numerical and analytical results are in good agreement. The integration of the control action into Newmark solution as presented in this study can be extended to finite element solutions to simulate the control of complex mechanical systems.

Kinematic-Kinetic-Rigidity Evaluation of a Six Axis Robot Performing a Task

Six axis serial robots of different sizes are widely used for pick and place, welding and various other operations in industry. Developments in mechatronics, which is the synergistic integration of mechanism, electronics and computer control to achieve a functional system, offer effective solutions for the design of such robots. The integrated analysis of robots is usually used in the design stage. In this study, it is offered that the integrated analysis of robots can also be used at the application stage. SolidWorks, CosmosMotion and ABAQUS programs are used with an integrated approach. Integration software (IS) is developed in Visual Basic by using the application programming interface (API) capabilities of these programs. An ABB-IRB1400 industrial robot is considered for the study. Different trajectories are considered. Each task is first evaluated by a kinematic analysis. If the task is out of the workspace, then the task is cancelled. This evaluation can also be done by robot programs like Robot Studio. It is proposed that the task must be evaluated by considering the limits for velocities, motor actuation torques, reaction forces, natural frequencies, displacements and stresses due to the flexibility. The evaluation is done using kinematic, kinetic and rigidity evaluation charts. The approach given in this work can be used for the optimal usage of robots.

FINITE ELEMENT ANALYSIS OF STRUCTURES WITH EXTRUDED ALUMINUM PROFILES HAVING COMPLEX CROSS SECTIONS

EXTRUDED ALUMINUM PROFILES ARE WIDELY USED IN BUILDING AND AU-TOMATION STRUCTURES DUE TO THEIR DURABILITY, LIGHTWEIGHT, CORROSION RESISTANCE, SHORTER FASTENING TIME AND REUSABILITY. PROPER DESIGN IS CRUCIAL IN MAINTAINING THE LIFESPAN OF THESE STRUCTURES. IT IS THERE-FORE ESSENTIAL TO DETERMINE THE STRUCTURAL BEHAVIORS OF THE STRUC-TURES SUCH AS THE NATURAL FREQUENCY, MODE SHAPE, ETC. THE FINITE ELEMENT ANALYSIS IS A METHOD WHICH HAS BEEN COMMONLY USED IN DETERMINING STRUCTURAL BEHAVIORS. HOWEVER, THERE ARE ALSO NUMER-OUS PROBLEMS IN ANALYZING THESE KINDS OF PROFILES USING SOLID FINITE ELEMENTS, SUCH AS MODELING, MESHING, SOLUTION TIME PROBLEMS, ETC. THEREFORE, BEAM FINITE ELEMENTS HAVE BEEN USED IN THE PRESENT STUDY IN MODELING OF THE PROFILES. FURTHERMORE, AN EQUIVALENT BEAM ELEMENT MODEL HAS BEEN DEVELOPED FOR BOLT-TOGETHER CON-NECTORS OF THE PROFILES. SIMULATION AND EXPERIMENTAL MODAL ANALY-SIS HAVE BEEN CONDUCTED ON EXAMPLE TEST SYSTEMS. IT HAS BEEN DEMONSTRATED THAT THIS MODELING TECHNIQUE IS VERY PRACTICAL AND THE RESULTS OBTAINED FROM THE METHOD AGREE WELL WITH THE EXPERI-MENTAL RESULTS.

Design of medical robotic operating rooms by SolidWorks

Medical robotic applications are increasing in operation rooms. It is necessary to select, locate and program appropriate robots for medical operations. SolidWorks and CosmosMotion controlled by the modeling and motion simulation programs created in VisualBASIC in this study are used for this purpose. The designer prepares the model input file which contains the information about the selected units and their locations in the room. The unit folders are prepared using the models of the producers given in the web sites. The unit folders prepared once can be used for other applications. The motion input file is prepared and the motions of the robots are simulated using the motion simulation program. Locations and animations of the robots are studied visually and the design is evaluated for the final decision.

A Mechatronic Design Process for Three Axis Robots

Three axis serial robots with different sizes are widely used for pick and place, welding and various operations in industry. Developments in mechatronics, which is the synergistic integration of mechanism, electronics and computer control to achieve a functional system, offer effective solutions for the design of such robots. The mechatronic design process involves solid modeling, assembly, rigid body dynamics, finite element rigidity analysis, motion control and computer programming. In this study, SolidWorks, CosmosMotion, CosmosWorks and PC-based motion control programs are used with an integrated approach. The integration software is developed in VisualBASIC by using the application programming interface (API) capabilities of these programs. An experimental three axis serial robot with a reach distance of 790 mm has been produced to develop and test the process.Copyright