An articulated bogie illustrationMultibody dynamics is also abundantly exploited within PhD research in our laboratory, as a tool for designing a prototype or to model a particular application, as for instance :

  • a new concept of articulated railway bogie
  • a parallel robot
  • a mobile robot
  • an overactuated manipulator
  • a human body model

Beside applications, researches are continuing in the field of multibody dynamics. The last decade (1990-2000) was devoted to modeling and numerical aspects (e.g. recursive methods, intermittent contacts, flexible bodies, implicit time integration schemes, symbolic computation, parameter identification,…).
More recently, we have focused our research activities towards mechatronic modeling, multiphysics analysis, system overactuation, multibody optimization, parallel computation, etc.
A particular emphasis is made on the teaching of multibody dynamics which, with the ROBOTRAN philosophy, is a research topic by itself. Indeed, the way of tackling a multibody problem is coarsely the same, for solving an student project, or for answering an industrial problem.

The following example illustrates the modeling and analysis of the lateral stability of an urban tramway equipped with articulated bogies with independent wheels. This work has been done in the frame of a PhD thesis (collaboration Bombardier-Eurorail). Animations show some eigenmodes obtained on the basis of a ROBOTRAN multibody model of the bogie, numerically linearized around quasi-static equilibrium on a straight track.

Optimal Control of Multibody systems

The Optimal Control of Multibody system (MBS) requires the use of appropriate tools for both the MBS modelling and the Optimal Control Problem (OCP) formulation. Optimal control consists of finding the control law for a given system such that a certain optimality criterion is achieved. In other words, the goal is to determine the control sequence u(t) for a given time interval [0,T] that minimizes a given cost function p. In addition, the optimization can be subjected to constraints on the states and/or the input of the system (e.g. actuator limits, safety operating conditions). To link the system input u(t) to its states x(t), such control strategy relies on an accurate model for the system dynamics. Symbolic equations generated by Robotran are very suitable for this purpose, in combination with CasADi which is used to formulate and solve the OCP. This approch works for both open-loop and closed loop systems.

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HIL vehicle simulator with haptic torque feed-back

View of the haptic steering wheelThe efficient code generated by Robotran enables to run simulations fast enough to include the human in the loop. To this purpose a steering wheel was developped and connected to a realtime Robotran simulation in order to analyze the pilot perception while driving different vehicles.

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Humanoid robot simulator for controller design

Walking of the COMAN robotThe design of humanoid robot controllers is a complex task. For this reason, the design of these robot controllers can benefit from being first performed in simulation, with the purpose to port them later to the real hardware. Robotran allows to develop very efficient simulators that enable the design of controllers, in particular for the locomotion.

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Pneumatic muscles for rail and road vehicle suspensions

Car corneringAdding pneumatic muscles in combination with classic air springs allows to increase the lateral stability of a road or rail vehicle while keeping good comfort performance. Indeed, using the principle of cross connected suspension, the muscles increases the roll stiffness of the suspension while keeping the same bounce stiffness.

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WalkMan

WALK-MAN targets at enhancing the capabilities of existing humanoid robots, permitting them to assist or replace humans in emergency situations. These include rescue operations in damaged or dangerous sites like destroyed buildings or power plants. 

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Muscles Based Controller Applied to an Active Ankle Prosthesis

Transtibial amputation can alter considerably the quality of life. Passive prosthesis (without energy supply) can restore basic locomotion but lacks the ability to produce healthy-like gait support. Indeed, the ankle joint needs high power peaks to propel the whole body forward during ankle pushoff. Without this power, an increase in metabolic energy consumption might appears due to muscles and joints fatigue. A motorised ankle prosthesis is therefore necessary to restore natural gait. This project aims at designing an active artificial ankle which mimick biological functions. Its mechanical conception targets a minimization of electrical energy consumption with the use of a serie elastic actuator. Both simulations and real tests are under development to setup bio-inspired reflexes able to adapt changing walking speed.

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Musculoskeletal modeling – quantification of upper limb internal efforts during movement

Illustration of the upper limbThis project consists in the development of a robust multibody model of the upper limb, which can be used for rehabilitation applications such as joint torque and muscle force quantification in the evaluation of musculoskeletal pathology severities.

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