Papers by Keyword: Stewart Platform

Abstract: Shape Memory Alloy (SMA) is a material with the ability to return to its original position, when being subjected to an appropriate thermo mechanical procedure. SMA find very wide applications in various facets of robotic and bio medical engineering. In this paper, review on ankle/foot diseases and the effective use of heat treated SMA was carried out. The manufacturing industry normally uses a range of between 200°C to 400°C to shape any biomedical product which has been used as the benchmark temperature throughout this research. The results suggested that annealing of 200°C produced the best suited for generating substantial displacement which can promote early rehabilitation of ankle/foot.

Abstract: In this paper, the analyses results on the behavior of Shape Memory Alloy (SMA) in Medical application were carried out. SMA materials are known by their aptitude to recover its original form when undergone suitable thermal changes. SMA is widely used in robotics, automotive, aerospace and it can be a potential application in biomedical engineering due to its low cost, high corrosion resistance and can be easily integrated with human applications. Stewart platform with two different upper platform diameters of 150 mm and 300 mm were designed, fabricated and used as experimental test-rig. Inverse kinematic calculations were carried out to identify a maximum deflection of Stewart platform that can promote continuous passive motion (CPM). The 150 mm base diameter Stewart platform is found to be the suited for generating substantial displacement between ankle and foot. The mechanical changes induced by the heat could be used as a property in manufacturing of rehabilitation device for foot and ankle.

Abstract: Determination of workspace is one of the main considerations in the design of any robot since the workspace geometry is considered a fundamental issue for robot design. This also plays a crucial role in trajectory planning. Among parallel manipulators, 6-DOF Stewart platforms is the most researched and widely used robot. However, till date there is no closed form expression of workspace volume for Stewart platform. In this paper, a novel method is proposed to find out the workspace volume of Stewart platform. In this paper, individual workspace of each leg of the manipulator (P-U-S) is determined and then translated by a common distance towards their geometrical center thus generating constant orientation workspace. To determine the workspace volume, geometric intersection of the six spheres is computed. This results in workspace of definite shape and size, whose volume is calculated using simple formulae. It is observed that the geometric way of determination of workspace area is computationally less tedious than the algebraic method. This also helps a lot for workspace optimization of such manipulators.

Abstract: Stewart platform is a typical parallel manipulator, which is equipped with rigidity, high positioning accuracy and other advantages. To achieve wonderful fit of the spacesuit upper torso, the Stewart platform is applied in the upper torso fit design, by which the upper torso active fit design method is proposed. The mathematical model and the experimental model are established to study the validly of the fit design method. The results verify that the application of Stewart platform in the fit design of spacesuit upper torso is feasible. The research in this paper provides useful guide for the fit design of the spacesuit in the future

Abstract: This paper analyses the result of the ongoing experimental research on the operational behavior of SMA in medical and robotics application. SMA are the materials that have the ability to return their original shape when subjected to the appropriate thermo mechanical interaction. SMA finds very wide applications in various facets of robotic equipments and industrial automation. They are easy to manufacture, low cost and can be integrated with human operations without any large scale safety requirements. Three SMA wires with diameters of 0.254 mm, 0.381 mm and 0.508 mm were experimented to measure the displacement of the wire with various bias forces. The 0.25 mm wire is best suited for generating substantial displacement. The displacement may be used to create CPM (Continues Passive Motion) for the Stewart platform for ankle rehabilitation therapy.

Abstract: Modern CAD/CAE allows supporting the process of design and construction at many stages, from concept development through specific engineering calculations to the creation of design documentation. In the case of constructing mechanisms, the kinematic and dynamic analysis of the proposed system is an important step in the introduced process. The paper presents an example of the kinematic and dynamic analysis of the Stewart platform using Siemens NX software [1, 2]. The conducted investigation has allowed determining the geometric characteristics of the mechanism of the Stewart platform as well as the geometric parameters of actuators and their location. A dynamic analysis of the platform helped with establishing the required motor forces for realizing the moves with the maximum speed and acceleration. This allowed the initial selection of the parameters of electric motors. Traffic analysis was also performed for investigating collisions between the parts of the hexapod and between the hexapod and its environment.

Abstract: This paper presents the results of the project conducted by the authors, which purpose was to build the simulator for teaching the disabled persons driving a car. This paper presents also the functional design requirements established for the project. The structure of the mechatronic system, basing on which the simulator was built, is also presented. It was also described the details of each subsystem of the simulator and its possibilities and the method of its functioning.

Abstract: In order to identify the geometrical parameters of parallel kinematics machines tools (PKM), a new parameters identification method is presented. The identification method is proposed based on a pose discrepancy model, which is deduced from the error between the nominal and measurement relative distance of two different spatial locations of the moving platform. In the identification method, an error sensitivity matrix, which expresses the sensitivity between the pose error and geometrical structural parameters error of PKM, can be created with numerical methods. The results of different numerical methods are analyzed. A measurement method to get the precise lengths of legs is presented, which decrease the number of identified parameters. In an experiment, the error of PKM is reduced from 6.71mm to 1.144mm. Therefore, the identification method is verified effective and feasible.

Abstract: The paper presents the implementations of the control algorithm of a virtual system (Stewart platform) in the CAD/CAE system (Siemens NX) and in the NI LabVIEW supervisory and control system. The combination of both systems enables the virtual simulation and presentation of the results in relation to the chosen in the work virtual model of the Stewart platform. The virtual model of the Stewart platform with the imposed constraints and mobility limitations was built in the Siemens NX CAD/CAE system. Each of the modeled elements is based on the real components of the car simulator prepared for the persons with mobility impairments. The chosen model of a Stewart platform is a system with six degrees of freedom that is often used to build various types of simulators (e.g. flight, car). Using the NI LabVIEW software, a mathematical model of the Stewart platform was built and inverse kinematics task was implemented in relation to the model of the platform. The created mathematical model that describes the behavior of the Stewart platform was used to determine the inputs to the control system of platform actuators.

Abstract: The study outlines the geometric analysis of motions executed by the Stewart platform and operated in the environment of a simulator for driving learning to be used by disabled people. The analysis was carried out on the basis of results obtained from the resolved kinematic problem for the inversed platform.