Nicolae Dumitru

Dynamic Analysis of an Exoskeleton New Ankle Joint Mechanism

In this paper, a dynamic analysis is performed for a new ankle joint mechanism used on an exoskeleton structure. The designed exoskeleton structure will be used in human rehabilitation purposes. The aim of this research is to determine the connection forces through an inverse dynamic analysis in order to use these for numerical simulations of the proposed prototype. The obtained results validate the design techniques, which demonstrates the engineering feasibility of the proposed design.

Motion Analysis of a Robotic Wheelchair

This paper presents the authors’ contribution in designing and evaluating a transmission system for a robotic wheelchair. The kinematics of the proposed transmission is analysed in order to realize a proper gear synthesis. A 3D model of the transmission and wheelchair are designed in Solid Works, being then used for the dynamic simulation of the system in Adams software. The wheelchair motion simulation is done in Adams in two modes: traction motion and steering motion active. In case of traction motion simulation the resulting trajectory is a straight line displacement, whereas in the case of active steering motion the resulting displacement trajectory is circular. Simulation results demonstrate the efficiency of the developed transmission model and assure successful implementation of this design in a robotic wheelchair.

Kinematic and Dynamic Study of a Mechanism for a Vehicle Front and Rear Stabilizer Bars

In this paper, a method is described for theoretical and experimental studies of a front and rear stabilizer bars used on vehicle steering and suspension systems. Based on the fatigue experimental tests performed on a special test-bed, a complex actuation mechanism from the test bed structure will be analyzed. This mechanism through his kinematic and dynamic structure assures complete conditions for simulating the dynamic behavior in a complex mode of the rear stabilizer bar used on a vehicle steering and suspension structures.

Design and Motion Analysis of a Powered Wheelchair

This paper presents researches developed by authors to design a motorized robotic wheelchair for disabled people. These devices enable disabled people perform many activities of daily living thus improving their quality of life. Proposed solution uses for traction one DC motor with steps adjustable angular speed, and for steering one smaller motor. It is presented the kinematic scheme of the proposed transmission and kinematic analysis. It is developed a CAD model of the transmission, mounted on a wheelchair. They are made simulation in Adams, in order to verify the functionality of the proposed transmission. The obtained results validate proposed transmission model and enable success implementation of this transmission to a wheelchair experimental model.

Modular Knee Orthosis FEM Analysis from Kinematic Considerations

In this paper a locomotion system kinematic analysis is presented in order to obtain the knee motion equations for a child walking. With these equations a modular knee orthosis with flexible elements was designed and simulated through finite elements analysis with ADAMS. The whole human locomotion system is analyzed. Based on these results a modular knee orthosis prototype for a 7 years old child with locomotion disabilities was fabricated. The prototype was evaluated through experimental tests with CONTEMPLAS motion analysis equipment.

Studies about Movement Biofidelity of a Dummy Neck Used in an Impact Testing Device

The paper presents the studies made on a similar biomechanical system composed by neck, head and thorax bones. The main movements analyzed were: axial rotation (left-right), lateral bending (left-right) and flexion-extension movement. After simulation was obtained the entire mechanical behavior based on data tables or diagrams. The models were defined in a CAD environment which includes Adams algorithm for dynamic simulations. The virtual models were obtained starting with CT images made on a living human subject. That virtual model composed by neck and head can be included in complex system (as a car system) and supposed to impact simulations (virtual crash tests). Also was developed a mathematical model based on Lagrange equations for a frontal impact testing cervical system. Our research team built main components of a testing device for dummy car crash neck-head system using anatomical data.

Human Upper Limb Robotic System Experimental Analysis by Using CONTEMPLAS Motion Software

In this paper a human upper limb robotic system is analyzed through an experimental study. The experimental analysis aim is to validate this robotic system type in order to use it in some kinetotherapy programs for the human upper limb recovery. The robotic system experimental research was performed by using special equipment called CONTEMPLAS which enables to evaluate angular variations in 3D environment. The equipment used in this research has two high-speed cameras which can record and establish the angular variations developed at the robotic system joints level. This paper consists of three main parts. In the first part there is an actual study of the robotic systems specially designed for the human upper limb rehabilitation, where the robotic system proposed for this experimental research is described. The second part includes some literature aspects regarding the movements developed by the human upper limb, and in the third part the experimental research is described in detail.

Dynamic Analysis of a Mobile Mechanical System with Deformable Elements

The paper presents a method for studying mechanisms with deformable elements, based on overlapping the solid rigid motion over the elastic solid one, in order to identify the dynamic response of the system. Modeling was based on finite element method, so the cinematic elements were meshed in bar type finite elements and the degrees of freedom per node were settled according to the motion character (planar or spatial). A Lagrange formulation of the finite element was adopted for the deformable elements connected in multibody systems. In order to define the joints constraints, the conditions for compatibility between elements were defined using a Boolean constant matrix. Computer processed results were verified by an experimental model.

Experimental and theoretical study of friction torque from radial ball bearings

In this paper it is presented a numerical simulation and an experimental study of total friction torque from radial ball bearings. For this purpose it is conceived a virtual CAD model of the experimental test bench for bearing friction torque measurement. The virtual model it is used for numerical simulation in ADAMS software, that allows dynamic study of multi-body systems and in particularly with facility Adams Machinery of dynamic behavior of machine parts. It is manufactured an experimental prototype of the test bench for radial ball bearings friction torque measurement. In order to measure the friction torque of the tested bearings it is used an equal resistance elastic beam element, with strain gauge transducer to measure bending deformations. The actuation electric motor of the bench has the shaft mounted on two bearings and the motor housing is fixed to the free side of the elastic beam, which is bended by a force proportional with the total friction torque. The beam elastic element with strain gauge transducer is calibrated in order to measure the force occurred. Experimental determination of the friction torque is made for several progressive radial loads. It is established the correlation from the friction torque and bearing radial load. The bench allows testing of several types and dimensions of radial bearings, in order to establish the bearing durability and of total friction torque.

Determination of Kinematic and Dynamic Behavior in the Driver’s Skull upon the Impact with the Steering Wheel

At European level, one of the main causes of death rates is generated by severe injuries following traffic accidents. The most serious consequences of traffic accidents result from lesions in the head.