An overview of recent results on the topic of modelling and Combined control for a chaser satellite with a robot arm is presented for an Active Debris Removal (ADR) scenario. The results were obtained during ongoing a...
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An overview of recent results on the topic of modelling and Combined control for a chaser satellite with a robot arm is presented for an Active Debris Removal (ADR) scenario. The results were obtained during ongoing and past projects between DLR and ESA as well as DLR internal studies. Combined control is defined here as a single controller which handles all degrees of freedom (DOF) of a satellite platform and its robot arm system. Therefore, it coordinates all sensor data and actuation to obtain the desired motion of the satellite and the robot arm. Nonlinear simulation models for an ADR scenario for the inactive ENVISAT target satellite have been developed. The nonlinear simulation tool, based on the object-oriented modelling language Modelica, includes the satellites, the robot arm and relevant disturbance terms such as sloshing and thruster dynamics, sensor noise, a visual camera performance model, flexible dynamics and the Low Earth Orbit (LEO) environment. The Combined controller is designed using a multi-stage and multi-objective design and optimization procedure which includes classical robust controldesign and linear analysis techniques, as well as nonlinear simulations using multiple scenarios (cases). Challenging aspects for the design are low sampling rates of the onboard sensors and thruster commands, limited robot actuator and thruster capabilities as well as uncertain parameters and sensor noise, which are considered in the design procedure. In addition, advanced trajectory planning algorithms for the approach, capture and Escape mode were developed, which consider the highly over-actuated system of a seven axis robot arm and the 6 DOF satellite motion as well as the actuator limitations. The Combined control approach was designed and verified using the nonlinear simulation tool for different control modes of the ADR scenario. It allows using all DOF of the system simultaneously. Therefore, highly dynamic maneuvers of the robot arm and satellite are
Besides from pure entertainment, Virtual Reality promises changes for the so-called Industry 4.0 sector. VR allows to visualize complex engineering data and provides a set of multimodal tools to inspect a 3D model on ...
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Besides from pure entertainment, Virtual Reality promises changes for the so-called Industry 4.0 sector. VR allows to visualize complex engineering data and provides a set of multimodal tools to inspect a 3D model on various levels. Early VR setups consisted of projectors, walls and powerful PCs to synchronize the data. These systems were expensive, presuppose expert knowledge and needed much space to be used efficiently. VR technology is still in its early stages, but, as innovations pick up pace, systems get easier to set up and the advances in graphics power allow for novel modes of visualization and interaction. This paper discusses a set of application areas for VR in industry and describes the implementation of a light-weight VR-system for industrial engineering applications. Our approach handles the complexity of native CAD engineering data and integrates tools to support engineering design review. We discuss the chances and limitations of the system and provide best practices for future VR applications in the field of Industry 4.0. (C) 2018, IFAC (international Federation of Automatic control) Hosting by Elsevier Ltd. All rights reserved.
The Internet of things (IoT) is revolutionizing the management and control of automated systems leading to a paradigm shift in areas, such as smart homes, smart cities, health care, and transportation. The IoT technol...
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A new MATLAB based software package which, besides analysis, can be used to design centralized or decentralized controllers to stabilize time-delay systems is introduced.
ISBN:
(纸本)9781509007592
A new MATLAB based software package which, besides analysis, can be used to design centralized or decentralized controllers to stabilize time-delay systems is introduced.
In this paper we introduce an algorithm for the synthesis of polynomial Lyapunov functions for polynomial vector fields. The Lyapunov function is a continuous piecewise-polynomial defined on simplices, which compose a...
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ISBN:
(纸本)9781509007592
In this paper we introduce an algorithm for the synthesis of polynomial Lyapunov functions for polynomial vector fields. The Lyapunov function is a continuous piecewise-polynomial defined on simplices, which compose a collection of simplices. The algorithm is elaborated and crucial features are explained in detail. The strengths and weaknesses of the algorithm are exemplified and a new way of sub-dividing the simplices is presented.
This paper addresses the computation of additively separable Lyapunov functions for interconnected systems. The presented results can be applied to reduce the complexity of the computations associated with stability a...
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ISBN:
(纸本)9781509007592
This paper addresses the computation of additively separable Lyapunov functions for interconnected systems. The presented results can be applied to reduce the complexity of the computations associated with stability analysis of large scale systems. We provide a necessary and sufficient condition for the existence of an additively separable Lyapunov function;subsequently, sparsity conditions are given for finding additively separable polynomial Lyapunov functions for both local and global stability of polynomial systems.
This paper focus on stochastic controldesign in the Kullback-Leibler sense. The technique is called the Fully Probabilistic design (FPD) and consist in essence of finding a stochastic control law, given in terms of a...
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ISBN:
(纸本)9781509007592
This paper focus on stochastic controldesign in the Kullback-Leibler sense. The technique is called the Fully Probabilistic design (FPD) and consist in essence of finding a stochastic control law, given in terms of a probability density function (pdf), minimizing the Kullback-Liebler distance between pdfs describing a given closed loop system and a desired closed loop system. This paper demonstrate that the FPD method can 1) be used in a Model Predictive control strategy, and 2) be used for control of the pneumatic valve which represents a nonlinear system.
A number of Linear Matrix Inequality (LMI) conditions for the design of gain-scheduled quadratic H-infinity output-feedback controllers can be found in the literature under a variety of assumptions on both the system ...
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ISBN:
(纸本)9781509007592
A number of Linear Matrix Inequality (LMI) conditions for the design of gain-scheduled quadratic H-infinity output-feedback controllers can be found in the literature under a variety of assumptions on both the system as well as the controller structure. The first contribution of the present paper is to provide a catalog of such conditions, including some new conditions, which cover most practical applications. In each setup, LMI conditions allowing implicit and explicit computation of the controller matrices are provided. As a second contribution, we illustrate how to use these conditions and compare their performance using a numerical example which allows us to exercise the controller design procedure in the various scenarios covered.
For the optimal point-to-point control of a discrete-time linear system in a time varying non-convex environment, this paper investigates how such problems can be handled online. An illustrative example is that of ste...
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ISBN:
(纸本)9781509007592
For the optimal point-to-point control of a discrete-time linear system in a time varying non-convex environment, this paper investigates how such problems can be handled online. An illustrative example is that of steering a robotic end-effector from an initial to a final state, while executing the motion free of collision in the presence of a human worker. The challenge is to obtain a solution with low effort, to be online applicable, while maintaining a close to optimal solution. The proposed method consists of first computing a range of trajectories, homotopic to the optimal unconstrained solution offline. Then, upon detection of an obstacle which may block the currently executed trajectory, an offline synthesized controller steers the system quickly to a desired homotopic trajectory. The resulting trajectory is free of collision and is determined by a fast iterative procedure.
This paper addresses the design problem of feedforward controllers for discrete-time Linear Time-Invariant (LTI) plant systems under the condition that prior external signals (e.g. disturbance or reference input) are ...
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ISBN:
(纸本)9781509007592
This paper addresses the design problem of feedforward controllers for discrete-time Linear Time-Invariant (LTI) plant systems under the condition that prior external signals (e.g. disturbance or reference input) are measurable online and can be exploited as the input to the feedforward controllers. The representation of descriptor systems is adopted to incorporate the prior external signals into the LTI plant systems. We propose a design method for our problem via the dual formulation of Generalized KYP (GKYP) lemma by considering that GKYP lemma can reduce the numerical complexity in controller design, because it has an ability to specify the frequency ranges of control requirements without introducing weighting functions. We extend the method to the case that plant systems have uncertainties represented as polytopic systems. Academic examples show the usefulness of our proposed methods.
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