Asko Rouvinen

Design of parallel intersector weld/cut robot for machining processes in ITER vacuum vessel

This paper presents a new parallel robot Penta-WH, which has five degrees of freedom driven by hydraulic cylinders. The manipulator has a large, singularity-free workspace and high stiffness and it acts as a transport device for welding, machining and inspection end-effectors inside the ITER vacuum vessel. The presented kinematic structure of a parallel robot is particularly suitable for the ITER environment. Analysis of the machining process for ITER, such as the machining methods and forces are given, and the kinematic analyses, such as workspace and force capacity are discussed.

Deflection compensation of a flexible hydraulic manipulator utilizing neural networks

Deflection compensation of flexible boom structures in robot positioning is usually done using tables with inverse kinematics solutions. The number of table values increases greatly if the working area of the boom is large and the required accuracy is high. On the other hand, inverse kinematics problems are very nonlinear, and if the structure is redundant, in some cases it cannot be solved in closed form. If the flexibility of the structure is taken into account, the problem is almost impossible to solve using analytical methods. Neural networks offer a possibility to approximate any linear or nonlinear function. Four different methods of using neural networks in the static deflection compensation of a flexible hydraulically driven manipulator are presented. Training information required for training neural networks is obtained by employing a simulation model that includes elasticity characteristics. The functionality of the presented methods is tested based on simulated results of positioning accuracy. The positioning accuracy is tested in 25 separate coordinate points. For each point, positioning is tested with five different mass loads. The mean positioning error of a manipulator decreases from 48 to 5.8 mm in the test points. This accuracy enables the use of flexible manipulators in the positioning of larger objects.

Robot positioning of a flexible hydraulic manipulator utilizing genetic algorithm and neural networks

Robot positioning requires that the actuator positions are calculated as a function of end effector position. This mapping is called inverse kinematics of a robot. The inverse kinematics problem is very nonlinear and in some cases it cannot be solved in closed form. Several iterative and neural network approaches are studied in solving the inverse kinematics problem. Deflection of the manipulator arms due to flexibility and mass load causes positioning error. The magnitude of the error depends on the amount of mass load and arm positions and the stiffness characteristics of arms. In this paper a method based on genetic algorithm is used to solve the inverse kinematics of a three degrees of freedom log crane. Neural networks are used to solve the correction values for deflection compensation.

Real-time multibody application for tree harvester truck simulator

A real-time simulator for a tree harvester has been developed for training in more effective vehicle and cutter operation and tree management. The equations of motion of the constrained mechanical system of the tree harvester are expressed using a recursive formulation. The hydraulic actuator modelling of the harvester is based on lumped fluid theory, in which the hydraulic circuit is divided into discrete volumes where pressures are assumed to be distributed equally, while pressure wave propagation in pipes and hoses is assumed to be negligible. For modelling purposes, valves are broken up into a number of adjustable restrictors, which can be modelled separately. The contact model used comprises two parts: collision detection and response. Collision detection identifies whether, when and where moving bodies may come in contact. Collision response prevents penetration when contact occurs and identifies how it should behave after collision. A penalty method is used in this study to establish object collision events. The major achievement of this study is combining these three modelling methods in the application of a real-time simulator.

Crane Operators Training Based on the Real-Time Multibody Simulation

This paper introduces a real-time multibody simulation approach. Two main sections have been described in depth and include a description of flexible bodies and modeling of a hydraulic system. In flexible bodies, the bodies are modelled using the floating frame of reference formulation. The equation of motion for the body is developed using the principle of virtual work. Penalty method is used when there are constraints in the mechanical system. The hydraulic system is modelled using lumped fluid theory. Two types of components, valves and hydraulic cylinders, are introduced for modelling. A numerical example is developed using two Craig-Bampton modes deformation modes modelled as flexible bodies.

Product Processes based on Digital Twin

Product development is performed by accomplished designers who make their best efforts to understand customer needs and desires via verbal or written feedback. This approach becomes cumbersome if a product design undergoes revolutionary changes. This paper focuses on how the potential of realtime simulation models based on Multibody System Dynamics or, in short, physics based Digital Twins, is utilized as a tool to interpret customers’ needs. The complete real-time simulation model can be seen as an interaction of several subsystems, such as environment, work process, mechanics, actuators, control system and user input. A mechanical subsystem based on the use of multibody system dynamics includes modeling of mechanical bodies, force elements acting between bodies, joints connecting bodies, and contacts. In this way, three main areas of product lifecycle are consistently covered. First, the benefits of the proposed approach are discussed in the Research & Development and Product Development section. Then comes service business, and finally, the authors discuss the effect of the approach in marketing and sales.

Real-time analysis of mobile machines using sparse matrix technique

The use of modern multibody simulation techniques enables the description of complex products, such as mobile machinery, with a high level of detail while still solving the equations of motion in real time. Using the appropriate modelling and implementation techniques, the accuracy of real-time simulation can be improved considerably. Conventionally, in multibody system dynamics, equations of motion are implemented using the full matrices approach that does not consider the sparsity feature of matrices. With this implementation approach, numerical efficiency decreases when sparsity increases. In this study, a numerical procedure based on semi-recursive and augmented Lagrangian methods for real-time dynamic simulation is introduced. To enhance computing efficiency, an equation of motion is implemented by employing the sparse matrix technique.

Simulation Environment for the Real-Time Dynamic Analysis of Hybrid Mobile Machines

The interest in using hybrid technology in Non-Road Mobile Machinery (NRMM) has increased significantly in the late 2000s due to tightening emission regulations (Tier 4). In general, utilization of hybrid technology can simplify the vehicle driveline compared to conventional mechanical and hydraulic power transmissions. On the other hand, hybrid technology and its different driving modes and multiple power sources creates new challenges in the design process. Many industries have used co-simulation and virtual prototyping approaches successfully as a development and diagnostic tool. However, it is still rarely used in the design of hybrid mobile machines. This is due to the fact, that the computer analysis of a mobile machine is a multidisciplinary task which requires a deep knowledge in several engineering areas. In this paper, a novel real-time co-simulation platform is presented that couples multi-body dynamics based physics modelling and Matlab/Simulink–based hybrid driveline modelling. The presented approach enables a fast and accurate virtual prototyping tool to calculate dimension hybrid driveline components and test various hybridization concepts.Copyright

Multibody approach for model-based fault detection of a reel

In order to improve the recognition of faulty situations, model-based fault detection can be used together with signal processing methods. In this study, faults and abnormalities of a reel are studied by employing the multibody simulation approach. The reel under consideration consists of a number of subsystems, including hydraulics, electrical drives, and mechanical parts. These subsystems are coupled by joints, friction forces, and contact forces. Using the multibody simulation approach, the complete model of the reel can be obtained by coupling different subsystems together. Three well-known multibody formulations, a method of Lagrange multipliers, an Augmented Lagrangian method, and a method based on projection matrix R, are briefly described and compared in order to find out the most efficient method for simulating the studied reel. Although this study is focused on the simulation of fault scenarios, the introduced multibody simulation approach can be utilized in real-time simulation. This makes it possible to apply the model to an existing reel.

Multibody Simulation Formulations in Fault Diagnosis of a Reel

In order to improve the recognition of faulty situations, the model-based fault diagnosis can be used together with signal processing methods. In this study, faults and abnormalities of a reel is studied by employing the multibody simulation approach. The reel under consideration consists of a number of subsystems including hydraulics, electrical drives and mechanical parts, which are coupled by joints, friction forces and contact forces. Using the multibody simulation approach, the complete model of the reel can be obtained by coupling different subsystems together. Three well-known multibody formulations, a method of Lagrange multipliers, an Augmented Lagrangian method and a method based on projection matrix R, are briefly described and compared in order to find out the most efficient method for simulating the studied reel. It is noteworthy, that the method based on an Augmented Lagrangian formulation is also capable of real-time fault diagnosis of a reel.Copyright