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49
Central pattern generators for locomotion control in animals and robots: a review
 NEURAL NETWORKS
, 2008
"... The problem of controlling locomotion is an area in which neuroscience and robotics can fruitfully interact. In this article, I will review research carried out on locomotor central pattern generators (CPGs), i.e. neural circuits capable of producing coordinated patterns of highdimensional rhythmic ..."
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Cited by 151 (20 self)
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The problem of controlling locomotion is an area in which neuroscience and robotics can fruitfully interact. In this article, I will review research carried out on locomotor central pattern generators (CPGs), i.e. neural circuits capable of producing coordinated patterns of highdimensional rhythmic output signals while receiving only simple, lowdimensional, input signals. The review will first cover neurobiological observations concerning locomotor CPGs and their numerical modelling, with a special focus on vertebrates. It will then cover how CPG models implemented as neural networks or systems of coupled oscillators can be used in robotics for controlling the locomotion of articulated robots. The review also presents how robots can be used as scientific tools to obtain a better understanding of the functioning of biological CPGs. Finally, various methods for designing CPGs to control specific modes of locomotion will be briefly reviewed. In this process, I will discuss different types of CPG models, the pros and cons of using CPGs with robots, and the pros and cons of using robots as scientific tools. Open research topics both in biology and in robotics will also be discussed. 1
Synchronization in Networks of Identical Linear Systems
, 2008
"... The paper investigates the synchronization of a network of identical linear statespace models under a possibly timevarying and directed interconnection structure. The main result is the construction of a dynamic output feedback coupling that achieves synchronization if the decoupled systems have n ..."
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Cited by 46 (0 self)
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The paper investigates the synchronization of a network of identical linear statespace models under a possibly timevarying and directed interconnection structure. The main result is the construction of a dynamic output feedback coupling that achieves synchronization if the decoupled systems have no exponentially unstable mode and if the communication graph is uniformly connected. The result can be interpreted as a generalization of classical consensus algorithms. Stronger conditions are shown to be sufficient – but to some extent, also necessary – to ensure synchronization with the diffusive static output coupling often considered in the literature. 1
COORDINATED PATHFOLLOWING IN THE PRESENCE OF COMMUNICATION LOSSES AND TIME DELAYS ∗
"... Abstract. This paper addresses the problem of steering a group of vehicles along given paths while holding a desired formation pattern. The solution to this problem, henceforth referred to as the Coordinated PathFollowing problem, unfolds in two basic steps. First, a pathfollowing control law is u ..."
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Cited by 20 (9 self)
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Abstract. This paper addresses the problem of steering a group of vehicles along given paths while holding a desired formation pattern. The solution to this problem, henceforth referred to as the Coordinated PathFollowing problem, unfolds in two basic steps. First, a pathfollowing control law is used that drives each vehicle to its assigned path regardless of the temporal speed profile adopted. This is done by making each vehicle approach a conveniently defined virtual target that moves along the path. In the second step, the speeds of the vehicles are adjusted so as to synchronize the positions of the corresponding virtual targets (also called coordination states) thus achieving coordination along the paths. In the problem formulation, it is explicitly considered that each vehicle transmits its coordination state to only a subset of the other vehicles, as determined by the communications topology adopted. It is shown that the system that is obtained by putting together the path following and coordination strategies can be naturally viewed as a feedback interconnected system. Using this result and recent results from nonlinear system and graph theory, conditions are derived under which the path following and the coordination errors are driven to a neighborhood of zero in the presence of communication failures and time delays. Two different situations are considered. The first captures the case where the communication graph is alternately connected and disconnected (brief connectivity losses). The second reflects an operating scenario where the union of the communication graphs over uniform intervals of time remains connected (uniformly connected in mean). To better ground the paper on a nontrivial design example, a coordinated pathfollowing algorithm is derived for multiple underactuated Autonomous Underwater Vehicles (AUVs). Simulation results are presented and discussed. Key words. Coordination control, communication losses and time delays, pathfollowing, autonomous underwater vehicle AMS subject classifications. 1. Introduction. Increasingly
A contraction theory approach to stochastic incremental stability
 IEEE Transactions on Automatic Control
, 2009
"... We investigate the incremental stability properties of Itô stochastic dynamical systems. Specifically, we derive a stochastic version of nonlinear contraction theory that provides a bound on the mean square distance between any two trajectories of a stochastically contracting system. This bound can ..."
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Cited by 19 (8 self)
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We investigate the incremental stability properties of Itô stochastic dynamical systems. Specifically, we derive a stochastic version of nonlinear contraction theory that provides a bound on the mean square distance between any two trajectories of a stochastically contracting system. This bound can be expressed as a function of the noise intensity and the contraction rate of the noisefree system. We illustrate these results in the contexts of stochastic nonlinear observers design and stochastic synchronization. 1
Synchronization of Interconnected Systems With Applications to Biochemical Networks: An InputOutput Approach
, 2010
"... This paper provides synchronization conditions for networks of nonlinear systems. The components of the network (referred to as “compartments ” in this paper) are made up of an identical interconnection of subsystems, each represented as an operator in an extended 2 space and referred to as a “spec ..."
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Cited by 17 (4 self)
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This paper provides synchronization conditions for networks of nonlinear systems. The components of the network (referred to as “compartments ” in this paper) are made up of an identical interconnection of subsystems, each represented as an operator in an extended 2 space and referred to as a “species.” The compartments are, in turn, coupled through a diffusionlike term among the respective species. The synchronization conditions are provided by combining the inputoutput properties of the subsystems with information about the structure of the network. The paper also explores results for statespace models, as well as biochemical applications. The work is motivated by cellular networks where signaling occurs both internally, through interactions of species, and externally, through intercellular signaling. The theory is illustrated by providing synchronization conditions for networks of Goodwin oscillators.
Application of Synchronization to Formation Flying spacecraft: Lagrangian Approach
 Journal of Guidance, Control, and Dynamics
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Collective stability of networks of winnertakeall circuits
 Neural Computation
, 2011
"... The neocortex has a remarkably uniform neuronal organization, suggesting that common principles of processing are employed throughout its extent. In particular, the patterns of connectivity observed in the superficial layers of the visual cortex are consistent with the recurrent excitation and inhib ..."
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Cited by 9 (3 self)
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The neocortex has a remarkably uniform neuronal organization, suggesting that common principles of processing are employed throughout its extent. In particular, the patterns of connectivity observed in the superficial layers of the visual cortex are consistent with the recurrent excitation and inhibitory feedback required for cooperativecompetitive circuits such as the soft winnertakeall (WTA). WTA circuits offer interesting computational properties such as selective amplification, signal restoration, and decision making. But, these properties depend on the signal gain derived from positive feedback, and so there is a critical tradeoff between providing feedback strong enough to support the sophisticated computations, while maintaining overall circuit stability. The issue of stability is all the more intriguing when one considers that the WTAs are expected to be densely distributed through the superficial layers, and that they are at least partially interconnected. We consider the question of how to reason about stability in very large distributed networks of such circuits. We approach this problem by approximating the regular cortical architecture as many interconnected cooperativecompetitive
Global convergence of quorumsensing networks
 Physical Review E
, 2010
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On differentially dissipative dynamical systems
 In 9th IFAC Symposium on Nonlinear Control Systems
, 2013
"... Abstract: Dissipativity is an essential concept of systems theory. The paper provides an extension of dissipativity, named differential dissipativity, by lifting storage functions and supply rates to the tangent bundle. Differential dissipativity is connected to incremental stability in the same way ..."
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Cited by 6 (2 self)
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Abstract: Dissipativity is an essential concept of systems theory. The paper provides an extension of dissipativity, named differential dissipativity, by lifting storage functions and supply rates to the tangent bundle. Differential dissipativity is connected to incremental stability in the same way as dissipativity is connected to stability. It leads to a natural formulation of differential passivity when restricting to quadratic supply rates. The paper also shows that the interconnection of differentially passive systems is differentially passive, and provides preliminary examples of differentially passive electrical systems.
CPGbased Control of a Turtlelike Underwater Vehicle
"... Abstract—We present a new bioinspired control strategy for an autonomous underwater vehicle by constructing coupled nonlinear oscillators, similar to the animal central pattern generators (CPGs). Using contraction theory, we show that the network of oscillators globally converges to a specific patt ..."
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Cited by 4 (3 self)
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Abstract—We present a new bioinspired control strategy for an autonomous underwater vehicle by constructing coupled nonlinear oscillators, similar to the animal central pattern generators (CPGs). Using contraction theory, we show that the network of oscillators globally converges to a specific pattern of oscillation. We experimentally validate the proposed control law using a turtlelike underwater vehicle, whose fin actuators successfully exhibit a pattern that resembles the motion of fore limbs of a swimming sea turtle. In order to further fulfill the potential of the CPGbased control, we propose to feed back the actuator states to the coupled oscillators, thereby achieving not only the synchronization of the oscillators, but also the synchronization of actual foil states. Such a closedloop version of CPGs makes the controller more robust and practical in the presence of external disturbances. I.