Method and apparatus for creating time-optimal commands for linear systems

A system for and method of determining an input command profile for substantially any dynamic system that can be modeled as a linear system, the input command profile for transitioning an output of the dynamic system from one state to another state. The present invention involves identifying characteristics of the dynamic system, selecting a command profile which defines an input to the dynamic system based on the identified characteristics, wherein the command profile comprises one or more pulses which rise and fall at switch times, imposing a plurality of constraints on the dynamic system, at least one of the constraints being defined in terms of the switch times, and determining the switch times for the input to the dynamic system based on the command profile and the plurality of constraints. The characteristics may be related to poles and zeros of the dynamic system, and the plurality of constraints may include a dynamics cancellation constraint which specifies that the input moves the dynamic system from a first state to a second state such that the dynamic system remains substantially at the second state

Avaliação da dinâmica de manipuladores robóticos sobre bases flexíveis

This work presents a method to predict the failure of a robotic manipulator’s task due to the flexibility of the elastic bodies that serves as a base. The errors can be the position, velocity and orientation of the tool attached to the tip of the robot. The method also provides a way to verify how modifications in the base design can change the dynamic behaviour of the coupled system. The motivation of such analysis is the crescent employment of service robots for in situ applications, where the use of a light and slender structure for the base may be the best and more feasible solution for placing the robot in the service environment. The analysis are divided as: model the Dynamic Multibody Systems of the robot, the base and the coupled base-robot, by Kane’s method; find the stiffness matrix of the base, by Finite Element Analysis; find the Rayleigh parameters of the proportional damping matrix of the base, by Experimental Modal Analysis. An in situ robotic hardcoating system (EMMA) is chosen as the case of study. Simulations are done for two different trajectories and three different bases. The results of the reference model (rigid base) and the coupled model (robot - flexible base) are then compared and shows the changes in the controled parameters due to the flexibility of the base. This analysis allows the verification of compliance to the hardcoating requirements like position, velocity and orientation of the gun with respect to the surface.Apresenta-se neste trabalho um método para prever a falha de um manipulador robótico ao realizar uma tarefa, devido à flexibilidade dos corpos elásticos que lhe servem como base. Os erros podem ser de posição, velocidade e orientação da ferramenta na extremidade do robô. O método também fornece um meio para verificar como modificações no projeto da base podem alterar o comportamento dinâmico do sistema acoplado. A motivação de tal análise se dá pelo crescente emprego de robôs de serviço para aplicações in situ, onde o uso de uma estrutura leve e esbelta pode ser a melhor e mais viável solução para posicionar o robô dentro do ambiente de serviço. A análise se divide em: modelar pelo método de Kane, os sistemas dinâmicos multicorpos do robô, da base e do sistema acoplado robô e base; encontrar a matriz de rigidez da base, pela análise por Elementos Finitos; e encontrar os parâmetros de Rayleigh da matriz de amortecimento proporcional, por análise Modal Experimental. Um sistema para revestimento robótico in situ (EMMA) é escolhido para estudo de caso. Simulações são realizadas para duas trajetórias e três bases diferentes. Os resultados do modelo de referência (base rígida) e o modelo acoplado (robô - base flexível) são então comparados e apresentam as mudanças que ocorrem, devido à flexibilidade da base, nos parâmetros controlados da tarefa. Esta análise permite a verificação da conformidade aos requisitos do processo de revestimento robótico, como posição, velocidade e orientação dadas à flexibilidade e o amortecimento da base

From plain visualisation to vibration sensing: using a camera to control the flexibilities in the ITER remote handling equipment

Thermonuclear fusion is expected to play a key role in the energy market during the second half of this century, reaching 20% of the electricity generation by 2100. For many years, fusion scientists and engineers have been developing the various technologies required to build nuclear power stations allowing a sustained fusion reaction. To the maximum possible extent, maintenance operations in fusion reactors are performed manually by qualified workers in full accordance with the "as low as reasonably achievable" (ALARA) principle. However, the option of hands-on maintenance becomes impractical, difficult or simply impossible in many circumstances, such as high biological dose rates. In this case, maintenance tasks will be performed with remote handling (RH) techniques. The International Thermonuclear Experimental Reactor ITER, to be commissioned in southern France around 2025, will be the first fusion experiment producing more power from fusion than energy necessary to heat the plasma. Its main objective is “to demonstrate the scientific and technological feasibility of fusion power for peaceful purposes”. However ITER represents an unequalled challenge in terms of RH system design, since it will be much more demanding and complex than any other remote maintenance system previously designed. The introduction of man-in-the-loop capabilities in the robotic systems designed for ITER maintenance would provide useful assistance during inspection, i.e. by providing the operator the ability and flexibility to locate and examine unplanned targets, or during handling operations, i.e. by making peg-in-hole tasks easier. Unfortunately, most transmission technologies able to withstand the very specific and extreme environmental conditions existing inside a fusion reactor are based on gears, screws, cables and chains, which make the whole system very flexible and subject to vibrations. This effect is further increased as structural parts of the maintenance equipment are generally lightweight and slender structures due to the size and the arduous accessibility to the reactor. Several methodologies aiming at avoiding or limiting the effects of vibrations on RH system performance have been investigated over the past decade. These methods often rely on the use of vibration sensors such as accelerometers. However, reviewing market shows that there is no commercial off-the-shelf (COTS) accelerometer that meets the very specific requirements for vibration sensing in the ITER in-vessel RH equipment (resilience to high total integrated dose, high sensitivity). The customisation and qualification of existing products or investigation of new concepts might be considered. However, these options would inevitably involve high development costs. While an extensive amount of work has been published on the modelling and control of flexible manipulators in the 1980s and 1990s, the possibility to use vision devices to stabilise an oscillating robotic arm has only been considered very recently and this promising solution has not been discussed at length. In parallel, recent developments on machine vision systems in nuclear environment have been very encouraging. Although they do not deal directly with vibration sensing, they open up new prospects in the use of radiation tolerant cameras. This thesis aims to demonstrate that vibration control of remote maintenance equipment operating in harsh environments such as ITER can be achieved without considering any extra sensor besides the embarked rad-hardened cameras that will inevitably be used to provide real-time visual feedback to the operators. In other words it is proposed to consider the radiation-tolerant vision devices as full sensors providing quantitative data that can be processed by the control scheme and not only as plain video feedback providing qualitative information. The work conducted within the present thesis has confirmed that methods based on the tracking of visual features from an unknown environment are effective candidates for the real-time control of vibrations. Oscillations induced at the end effector are estimated by exploiting a simple physical model of the manipulator. Using a camera mounted in an eye-in-hand configuration, this model is adjusted using direct measurement of the tip oscillations with respect to the static environment. The primary contribution of this thesis consists of implementing a markerless tracker to determine the velocity of a tip-mounted camera in an untrimmed environment in order to stabilise an oscillating long-reach robotic arm. In particular, this method implies modifying an existing online interaction matrix estimator to make it self-adjustable and deriving a multimode dynamic model of a flexible rotating beam. An innovative vision-based method using sinusoidal regression to sense low-frequency oscillations is also proposed and tested. Finally, the problem of online estimation of the image capture delay for visual servoing applications with high dynamics is addressed and an original approach based on the concept of cross-correlation is presented and experimentally validated