Eurico Seabra

A Parametric Study on the Baumgarte Stabilization Method for Forward Dynamics of Constrained Multibody Systems

This paper presents and discusses the results obtained from a parametric study on the Baumgarte stabilization method for forward dynamics of constrained multibody systems. The main purpose of this work is to analyze the influence of the variables that affect the violation of constraints, chiefly the values of the Baumgarte parameters, the integration method, the time step and the quality of the initial conditions for the positions. In the sequel of this process the formulation of the rigid multibody systems is reviewed. The generalized Cartesian coordinates are selected as the variables to describe the bodies’ degrees of freedom. The formulation of the equations of motion uses the Newton-Euler approach that is augmented with the constraint equations that lead to a set of differential algebraic equations. Furthermore, the main issues related to the stabilization of the violation of constraints based on the Baumgarte approach are revised. Special attention is also given to some techniques that help in the selection process of the values of the Baumgarte parameters, namely those based on the Taylor’s series and Laplace transform technique. Finally, a slider crank mechanism with eccentricity is considered as an example of application in order to illustrated how the violation of constraints can be affected by different factors such as the Baumgarte parameters, integrator, time step and initial guesses.© 2009 ASME

Property Patterns for the Formal Verification of Automated Production Systems

Abstract In recent years, several approaches to the analysis of automation systems dependability through the application of formal verification techniques have been proposed. Much of the research has been concerned with the modelling languages used, and how best to express the automation systems, so that automated verification might be possible. Less attention, however, has been devoted to the process of writing properties that accurately capture the requirements that need verification. This is however a crucial aspect of the verification process. Writing appropriate properties, in a logic suitable for verification, is a skilful process, and indeed there have been reports of properties being wrongly expressed. In this paper we put forward a tool and a collection of property patterns that aim at providing help in this area.

Investigation on the Baumgarte Stabilization Method for Dynamic Analysis of Constrained Multibody Systems

This paper presents an investigation on the Baumgarte stabilization method for dynamic analysis of constrained multibody systems. The purpose of this work is to study the influence of the main variables that affect the constraints violation, namely, the values of the Baumgarte parameters. In the process, the formulation of the dynamic equations of motion of constrained multibody systems and the main issues of the Baumgarte stabilization method are revised. Attention is given to the techniques to help in the Baumgarte parameters selection. A demonstrative example is presented and the results of some simulations are discussed.

Web-Assisted Laboratory for Control Education: Remote and Virtual Environments

The Web Assisted Laboratory for Control (WALC) engineering on-line education is described. This on-line platform was developed by a multidisciplinary team. WALC enables the access to several virtual and remote laboratories experiences on automation, process control and numerical methods. The virtual environment enables the registered user to test different control systems (hydraulic, mechanical, electrical) working in open and close loop. This environment is simulated based on the numerical solutions of the differential equations that describe the real world systems. An industrial automation network is available allowing the user to test different programs running on PLCs. The remote access to the platform is confined to pre-registered users and under a booking system ensuring that only the registered user is on-line. Other functionalities are depicted. Based on user’ feedback analysis, and since this platform was developed as a dynamic learning tool, their needs are fulfilled.

Design, implementation and testing of a new user interface for a smart walker

This paper proposes to present and discuss in detail the design of a novel handlebar of a motorized walker to be used as an interface between the user and the motor controller of the wheels. This device enables the user to indicate and command the direction and speed of the walkers motion. This new interface intends to be user-friendly and low cost. Safety considerations are also addressed to detect users fall. Preliminary results indicate that it is feasible to combine low cost sensors with a simple motor control, allowing a smooth and enjoyable driving, and fast response of the walker with no sense of delay.

A new integrated device to read user intentions when walking with a Smart Walker

Walkers are commonly seen in hospitals and clinics, but only individuals with fairly good motor function can use them. Hence, walkers should be more adaptive to the various needs of the users. This study includes the conceptual design, implementation and validation of a Smart Walker with a new interface approach integrated. The implementation of the interface is based on two potentiometers and it intends to read the users movement intentions to command the walker. In addition, this new interface can be adapted to different types of patients through the adjustment of its dynamical characteristics. Based on this real-time identification of users commands, an approach to the control architecture was developed and it is based on a fuzzy logic algorithm that allows to control the walkers motors and permitsthe user to manipulate the Smart Walker at his own pace. Results with healthy users show the reliability of the proposed device and control architecture to read the user intentions and control the walker accordingly.

Considerations and Mechanical Modifications on a Smart Walker

It is known that human mobility has the tendency to decrease, gradually, with age as a consequence of neurological, muscular and/or osteoarticular deterioration. Thus, in an aging society, devices that provide mobility assistance and ambulatory daily exercises are essential for the health and life quality of such individuals. Besides a brief introduction about gait aid devices, this paper presents and proposes improvements on the third prototype of a Smart Walker. This versatile rehabilitation and functional tool developed by a researcher group was used for one year, in a clinical environment at a hospital, by six patients. Based on the acquired know-how, the physicians, physiotherapist and patients feedback, a fourth prototype is being developed, mechanically and electronically improved. This paper will focus on the proposed mechanical, design and ergonomic considerations.

HiL simulation workbench for testing and validating PLC programs

Usually, Model-in-the-loop (MiL), Software-in-the-loop (SiL) and Hardware in the loop (HiL) simulation approaches are used in industry and all of them have to deal with the inter process communication issues between systems components. In this paper it is intended to describe the construction of a prototype workbench for testing and validation of Programmable Logic Controllers (PLC) programs, using HiL simulation approach, focusing this study on guaranteeing adequate plant models to be used. This work is inserted in a bigger project that deals with creation of a flexible automation platform that is used for controlling any kind of networked industrial automation systems. This platform considers several industrial protocol communications and different kind of sensors and actuators, usually used in industry, and it was developed on the context of WALC (Web Assisted Laboratory for Control Engineering on-line) project.

Mechatronic medical device for wrist rehabilitation

In the paper, the mechatronic design of a new type of Powerball®, named ControlledBioBall, carried out to overcome the present drawbacks, is be presented and discussed with special focus on the software developed in the editor LabVIEW®. Devices for wrist rehabilitation must be able to make movements of the wrist quirky and complex. Powerball® is such a market existing device that can be used for wrist rehabilitation and also as a sports aid for strengthening the wrist. The operation of Powerball® is based on the gyroscope principle. While the gyroscope is spinning, the movement of the wrist will tilt the shell and a reaction moment will be produced. Nevertheless, Powerball® in the existing market have considerable limitations, such as: must be manually started; the rotation speed is not controlled; the torque must be at least equal to the minimum torque to maintain the rotation of the mass inside Powerball®, and finally, due to the small panel attached to the ball patients will find inconvenience to view and manipulate it. This manner, for improving the effectivity of the wrist rehabilitation processes, a new type of Powerball® has been developed. This will have adjustable speed given by an electric motor inside the ball, and consequently the manual start and the requirement of minimum torque will be eliminated. Also, a system composed by sensors, data acquisition board and human-machine interface will be considered to allow the process of rehabilitation to be fully controlled..

Development and Optimization of a Small Scale Pellet Burner

Environmental concerns and the drive to reduce the dependence on petroleum brought the use of renewable energies to the forefront. Biomass appears as a very interesting alternative for direct conversion into heat. In this context, densified forms of biomass such as pellets are of great relevance because of their easy of use, high efficiency and low emissions.The practical interest in pellet combustion has been driven by the domestic heating sector, which favors the characteristics that are intrinsic of this fuel, despite its relatively higher price. However, the growing costs of fossil fuels have extended the interest of pellet fuels into industrial applications, including co-firing in power stations.A fast growing market includes the retrofitting of existing fuel boilers and furnaces with alternative burners that can be fitted into existing combustion systems. Such an approach has proved very attractive due to the low installation cost and the growing existence of fuels produced in the vicinity of the end user. This involves in most cases a custom built application which requires a high level of flexibility to variable operating conditions.This work reports on the development of a 120 kW pellet burner. A prototype of the burner was built that enables the independent control of the air supply into various regions of the combustion chamber and an accurate supply of fuel. The burner was fitted into a testing furnace of cylindrical shape oriented horizontally. Its diameter is 0.5 m and is constructed in a modular fashion with a total length of 2.2 m. All the facility is fully instrumented and includes: temperature data in various locations inside the chamber, flue gases emissions (CO, CO2, NOx) measurements and flow rates.The objective of the test and development is to optimize the combustion over the thermal load range of the facility. The excess air, fuel supply (primary and secondary) and the shape of the furnace grate enable the optimization of the burner with CO emissions of approximately 50 ppm, well below the acceptable limits.Copyright