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391
The Haptic Display of Complex Graphical Environments
 Proc. of ACM SIGGRAPH
, 1997
"... Force feedback coupled with visual display allows people to interact intuitively with complex virtual environments. For this synergy of haptics and graphics to flourish, however, haptic systems must be capable of modeling environments with the same richness, complexity and interactivity that can be ..."
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Cited by 158 (10 self)
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Force feedback coupled with visual display allows people to interact intuitively with complex virtual environments. For this synergy of haptics and graphics to flourish, however, haptic systems must be capable of modeling environments with the same richness, complexity and interactivity that can be found in existing graphic systems. To help meet this challenge, we have developed a haptic rendering system that allows for the efficient tactile display of graphical information. The system uses a common highlevel framework to model contact constraints, surface shading, friction and texture. The multilevel control system also helps ensure that the haptic device will remain stable even as the limits of the renderer's capabilities are reached. CR Categories and Subject Descriptors: C.3 [Special Purpose and ApplicationBased Systems]: Realtime Systems
Six DegreeofFreedom Haptic Rendering Using Voxel Sampling
 Proc. ACM Siggraph, ACM
, 1999
"... A simple, fast, and approximate voxelbased approach to 6DOF haptic rendering is presented. It can reliably sustain a 1000 Hz haptic refresh rate without resorting to asynchronous physics and haptic rendering loops. It enables the manipulation of a modestly complex rigid object within an arbitraril ..."
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Cited by 132 (1 self)
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A simple, fast, and approximate voxelbased approach to 6DOF haptic rendering is presented. It can reliably sustain a 1000 Hz haptic refresh rate without resorting to asynchronous physics and haptic rendering loops. It enables the manipulation of a modestly complex rigid object within an arbitrarily complex environment of static rigid objects. It renders a shortrange force field surrounding the static objects, which repels the manipulated object and strives to maintain a voxelscale minimum separation distance that is known to preclude exact surface interpenetration. Force discontinuities arising from the use of a simple penalty force model are mitigated by a dynamic simulation based on virtual coupling. A generalization of octree improves voxel memory efficiency. In a preliminary implementation, a commercially available 6DOF haptic prototype device is driven at a constant 1000 Hz haptic refresh rate from one dedicated haptic processor, with a separate processor for graphics. This system yields stable and convincing force feedback for a wide range of user controlled motion inside a large, complex virtual environment, with very few surface interpenetration events. This level of performance appears suited to applications such as certain maintenance and assembly task simulations that can tolerate voxelscale minimum separation distances.
Mobile Robot Localization Using Landmarks
, 1997
"... We describe an efficient method for localizing a mobile robot in an environment with landmarks. We assume that the robot can identify these landmarks and measure their bearings relative to each other. Given such noisy input, the algorithm estimates the robot's position and orientation with respect t ..."
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Cited by 117 (5 self)
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We describe an efficient method for localizing a mobile robot in an environment with landmarks. We assume that the robot can identify these landmarks and measure their bearings relative to each other. Given such noisy input, the algorithm estimates the robot's position and orientation with respect to the map of the environment. The algorithm makes efficient use of our representation of the landmarks by complex numbers. The algorithm runs in time linear in the number of landmarks. We present results of simulations and propose how to use our method for robot navigation.
On Dynamic MultiRigidBody Contact Problems with Coulomb Friction
"... . This paper is summary of a comprehensive study of the problem of predicting the possible acceleration(s) of a set of rigid, threedimensional bodies in contact in the presence of Coulomb friction. We begin with a brief introduction to this problem and a survey of related work and previous approach ..."
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Cited by 75 (18 self)
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. This paper is summary of a comprehensive study of the problem of predicting the possible acceleration(s) of a set of rigid, threedimensional bodies in contact in the presence of Coulomb friction. We begin with a brief introduction to this problem and a survey of related work and previous approaches. This is followed by the introduction of two novel complementarity formulations for the contact problem under two friction laws: Coulomb's Law and an analogous law in which Coulomb's quadratic friction cone is approximated by a pyramid. Under a full column rank assumption on the system Jacobian matrix, we establish the existence and uniqueness of a solution to our new models in the case where the friction coefficients are nonnegative and sufficiently small. For the model based on the friction pyramid law, we also show that the classical Lemke almostcomplementary pivot algorithm and our new feasible interior point method are guaranteed to compute a solution. Extensive computational result...
An Intelligent Predictive Control Approach to the HighSpeed CrossCountry Autonomous Navigation Problem
, 1995
"... mRIm9533 submitted in partial fulfiumtnr of the reqimlmts for the degm of ..."
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Cited by 72 (3 self)
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mRIm9533 submitted in partial fulfiumtnr of the reqimlmts for the degm of
Speech sound acquisition, coarticulation, and rate effects in a neural network model of speech production
 Psychological Review
, 1995
"... This article describes a neural network model of speech motor skill acquisition and speech production that explains a wide range of data on variability, motor equivalence, coarticulation, and rate effects. Model parameters are learned during a babbling phase. To explain how infants learn languagesp ..."
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Cited by 71 (21 self)
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This article describes a neural network model of speech motor skill acquisition and speech production that explains a wide range of data on variability, motor equivalence, coarticulation, and rate effects. Model parameters are learned during a babbling phase. To explain how infants learn languagespecific variability limits, speech sound targets take the form of convex regions, rather than points, in orosensory coordinates. Reducing target size for better accuracy during slower speech leads to differential effects for vowels and consonants, as seen in experiments previously used as evidence for separate control processes for the 2 sound types. Anticipatory coarticulation arises when targets are reduced in size on the basis of context; this generalizes the wellknown lookahead model of coarticulation. Computer simulations verify the model's properties. The primary goal of the modeling work described in this article is to provide a coherent theoretical framework that provides explanations for a wide range of data concerning the articulator movements used by humans to produce speech sounds. This is carried out by formulating a model that transforms strings of phonemes into continuous articulator movements for
Neural Control of Rhythmic Arm Movements
 Neural Networks
, 1998
"... In this paper we present an approach to robot arm control based on exploiting the dynamical properties of a simple neural network oscillator circuit coupled to the joints of an arm. The entrainment and input/output properties of the oscillators are used to perform a variety of tasks with the same ar ..."
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Cited by 65 (3 self)
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In this paper we present an approach to robot arm control based on exploiting the dynamical properties of a simple neural network oscillator circuit coupled to the joints of an arm. The entrainment and input/output properties of the oscillators are used to perform a variety of tasks with the same architecture, without any modeling of the arm or its environment. The approach is implemented on two real robot arms, and has been used to tune into the resonant frequency of pendulums, perform multijoint coordinated motion by turning cranks, and exploit the dynamics of a `Slinky' toy to coordinate the motion of two arms. By exploiting the coupling between the physical arm and the neural oscillator, a range of complex behaviors can be achieved with a very simple system. Keywords: Oscillator, Neural control, Neural network, Robot Manipulator, Rhythmic movement. Neural Control of Rhythmic Arm Movements 2 1 Introduction This paper describes the properties of a set of simple neural network os...
Hybrid Zero Dynamics of Planar Biped Walkers
 IEEE Transactions on Automatic Control
, 2001
"... Planar, underactuated, biped walkers form an important domain of applications for hybrid dynamical systems. This paper presents the design of exponentially stable walking controllers for general planar bipedal systems that have one degree of freedom greater than the number of available actuators. Th ..."
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Cited by 59 (21 self)
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Planar, underactuated, biped walkers form an important domain of applications for hybrid dynamical systems. This paper presents the design of exponentially stable walking controllers for general planar bipedal systems that have one degree of freedom greater than the number of available actuators. The withinstep control action creates an attracting invariant seta two dimensional zero dynamics submanifold of the full hybrid modelwhose restriction dynamics admits a scalar LTI return map. Exponentially stable periodic orbits of the zero dynamics correspond to exponentially stabilizable orbits of the full model. A convenient parameterization of the hybrid zero dynamics is imposed through the choice of a class of output functions. Parameter optimization is used to tune the hybrid zero dynamics in order to achieve closedloop, exponentially stable walking with low energy consumption, while meeting natural kinematic and dynamic constraints. The general theory developed in the paper is illustrated on a five link walker, consisting of a torso and two legs with knees.