The study of development either artificial or biological, can highlight the mechanisms underlying learning and adaptive behavior. We shall argue whether developmental studies might provide a different and potentially ...
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ISBN:
(纸本)0819438618
The study of development either artificial or biological, can highlight the mechanisms underlying learning and adaptive behavior. We shall argue whether developmental studies might provide a different and potentially interesting perspective either on how to build an artificial adaptive agent, or on understanding how the brain solves sensory, motor, and cognitive tasks. It is our opinion that the acquisition of the proper behavior might indeed be facilitated because within an ecological context, the agent, its adaptive structure and the environment dynamically interact thus constraining the otherwise difficult "learning problem". In very general terms we shall describe the proposed approach and supporting biological related facts. In order to further analyze these aspects from the modeling point of view, we shall demonstrate how a twelve degrees of freedom "baby" humanoid robot acquires orienting and reaching behaviors, and what advantages the proposed framework might offer. In particular, the experimental setup consists of a five degrees-of-freedom (dof) robot head, and an off-the-shelf six dof robot manipulator, both mounted on a rotating base: i.e. the torso. From the sensory point of view, the robot is equipped with two space-variant cameras, an inertial sensor simulating the vestibular system, and proprioceptive information through motor encoders. The biological parallel is exploited at many implementation levels. It is worth mentioning, for example, the space-variant eyes, exploiting foveal and peripheral vision in a single arrangement, the inertial sensor providing efficient image stabilization (vestibulo-ocular reflex).
Many of the future missions for mobile robots demand multi-robot systems which are capable of operating in large environments for long periods of time. One of the most critical capabilities is the ability to localize ...
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ISBN:
(纸本)0819438618
Many of the future missions for mobile robots demand multi-robot systems which are capable of operating in large environments for long periods of time. One of the most critical capabilities is the ability to localize - a mobile robot must be able to estimate its own position and to consistently transmit this information to other robots and control sites. Although state-of-the-art GPS is capable of yielding unmatched performance over large areas, it is not applicable in many environments (such as within city streets, under water, indoors, beneath foliage or extra-terrestrial robotic missions) where mobile robots are likely to become commonplace. A widely researched alternative is Simultaneous Localization and Map Building (SLAM): the vehicle constructs a map and, concurrently, estimates its own position. However, most approaches are non-scalable (the storage and computational costs vary quadratically and cubically with the number of beacons in the map) and can only be used with multiple robotic vehicles with a great degree of difficulty. In this paper, we describe the development of a scalable, multiple-vehicle SLAM system. This system, based on the Covariance Intersection algorithm, is scalable - its storage and computational costs are linearly proportional to the number of beacons in the map. Furthermore, it is scalable to multiple robots - each has complete freedom to exchange partial or full map information with any other robot at any other time step. We demonstrate the real-time performance of this system in a scenario of 15,000 beacons.
The superb aerial performance of flying insects is achieved with comparatively simple neural machinery. We have been investigating the pathway in the locust visual system that signals the rapid approach of an object t...
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ISBN:
(纸本)0819438618
The superb aerial performance of flying insects is achieved with comparatively simple neural machinery. We have been investigating the pathway in the locust visual system that signals the rapid approach of an object towards the eye. Two identified neurons have been shown to respond selectively to the images of an object approaching the locust's eye. A neural network based on the input organisation of these neurons responds directionally when challenged with approaching and receding objects and reveals the importance of a critical race, between excitation passing down the network and inhibition directed laterally, for the rapid build-up of excitation in response to approaching objects. The strongest response is given to an object approaching on a collision course with the eye, when collision is imminent. Like the neurons, the network is tightly tuned to a collision trajectory. We have incorporated this network into the control structure of a small mobile Kephera robot using the IQR 4-21 software we developed. The network responds to looming motion and is effective at evoking avoidance manoeuvres in the robot, moving at speeds from 1-12.5cm/s. Our aim is to use the circuit as an artificial looming detector for use in moving vehicles.
Traditional robotics uses non-compliant materials for all components involved in the production of movement. Elasticity is avoided as far as possible, because it leads to hazardous oszillations and makes control of pr...
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Traditional robotics uses non-compliant materials for all components involved in the production of movement. Elasticity is avoided as far as possible, because it leads to hazardous oszillations and makes control of precise movements very difficult. Due to this deliberate stiffness, robots are typically heavy and clumsy structures in comparison to their living counterparts (i.e. man and animals). Yet, moving systems in nature cope not only with the difficulties introduced by compliant materials, they also take advantage of the elasticity in muscles and tendons to produce smooth and even rapid movements. It is understood, that elasticity in a multi-jointed moving system requires sophisticated control mechanisms - as provided by a nervous system or a suitably programmed computer. In this contribution I shall describe a two-jointed robot with purpose-built elasticity in its actuators. This is accomplished by spiral springs placed in series with a conventional electric motor and a tendon to the arm. It is shown that, with sufficiently, soft elasticity, oscillations can be avoided by active oscillation damping. (Such active oscillation damping presumably also governs movement control in man and animals.) Furthermore, once the major problem has been overcome, elasticity is found to offer a wide spectrum of valuable advantages, as far as the most serious problems in traditional robotics are concerned. They are summarized by terms such as, `less dangerous', `position tolerant', `lightweight construction', `controlled forces' and, `ballistic movements'. These will be explained in detail and presented for discussions.
RoBlock is the first phase of an internally financed project at the Institute aimed at building a system in which two industrial robots suspended from a gentry, as shown below, cooperate to perform a task specified by...
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ISBN:
(纸本)0819438618
RoBlock is the first phase of an internally financed project at the Institute aimed at building a system in which two industrial robots suspended from a gentry, as shown below, cooperate to perform a task specified by an external user, in this case, assembling an unstructured collection of coloured wooden blocks into a specified 3-dimensional pattern. The blocks are indentified and localised using computer vision and grasped with a suction cup mechanism. Future phases of the project will involve other processes such as grasping and lifting, as well as other types of robot such as autonomous vehicles or variable geometry trusses. Innovative features of the control software system include: The use of an advanced trajectory planning system which ensures collision avoidance based on a generalisation of the method of artificial potential fields [1], The use of a generic model-based controller which "learns" the values of parameters, including static and kinetic friction, of a detailed mechanical model of itself by comparing actual with planned movements [2], The use of fast, flexible, and robust pattern recognition and 3D-interpretation strategies, Integration of trajectory planning and control with the sensorsystems in a distributed Java application running on a network of PC's attached to the individual physical components. In designing this first stage, the aim was to build in the minimum complexity necessary to make the system non-trivially autonomous and to minimize the technological risks. The aims of this project, which is planned to be operational during 2000, are as follows: To provide a platform for carrying out experimental research in multi-agent systems and autonomous manufacturing systems, To test the interdisciplinary cooperation architecture of the Maersk Institute, in which researchers in the fields of applied mathematics (modelling the physical world), software engineering (modelling the system) and sensor/actuator technology (relating the virtual and
The American Lobster Homarus americanus is a highly mobile marine decapod, ubiquitous to the benthic environment of the eastern North Atlantic. Lobsters occupy a range of subtidal habitats on the continental shelf, an...
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ISBN:
(纸本)0819438618
The American Lobster Homarus americanus is a highly mobile marine decapod, ubiquitous to the benthic environment of the eastern North Atlantic. Lobsters occupy a range of subtidal habitats on the continental shelf, and are capable of navigating through spatially complex boulder fields, as well as coping with variable water currents. Given these competencies, we have adopted the lobster as a design model for a biomimetic autonomous underwater vehicle intended for operation in similar environments. A central motor pattern generator model was developed from electromyographic data from lobsters, and is being implemented on an eight-legged ambulatory vehicle. The vehicle uses Nitinol shape-memory alloy wires as linear actuators, physically modeling the antagonistic muscle pairs of a lobster leg. The contraction of the wires is produced by heating them with an electrical current. This produces a change in the crystalline structure of the material from a martensite to an austenite state, resulting in a 5% contraction of the wire. Three pairs of wires are used around three joints to produce a three-degrees-of-freedom walking leg. Current drivers power the actuators, and pulse-width modulation is used to obtain graded contractions from the muscles. The combination of a biologically based control system coupled with a linear actuator sharing many characteristics of invertebrate muscle tissue has enabled us to construct a biomimetic ambulatory robot sharing some of the competencies of the model.
While significant recent progress has been made in development of mobile robots for planetary surface exploration, there remain major challenges. These include increased autonomy of operation, traverse of challenging ...
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ISBN:
(纸本)0819438618
While significant recent progress has been made in development of mobile robots for planetary surface exploration, there remain major challenges. These include increased autonomy of operation, traverse of challenging terrain, and fault-tolerance under long, unattended periods of use. We have begun work which addresses some of these issues, with an initial focus on problems of "high risk access," that is, autonomous roving over highly variable, rough terrain. This is a dual problem of sensing those conditions which require rover adaptation, and controlling the rover actions so as to implement this adaptation in a well understood way (relative to metrics of rover stability, traction, power utilization, etc.). Our work progresses along several related technical lines: 1) development a fused state estimator which robustly integrates internal rover state and externally sensed environmental information to provide accurate "configuration" information;2) kinematic and dynamical stability analysis of such configurations so as to determine "predicts" for a needed change of control regime (e.g., traction control, active c.g. positioning, rover shoulder stance/pose);3) definition and implementation of a behavior-based control architecture and action-selection strategy which autonomously sequences multi-level rover controls and reconfiguration. We report on these developments, both software simulations and hardware experimentation. Experiments include reconfigurable control of JPL's Sample Return Rover geometry and motion during its autonomous traverse over simulated Mars terrain.
This paper presents a sensorimotor architecture integrating computational models of a cerebellum and a basal ganglia and operating on a microrobot. The computational models enable a microrobot to learn to track a movi...
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ISBN:
(纸本)0819438618
This paper presents a sensorimotor architecture integrating computational models of a cerebellum and a basal ganglia and operating on a microrobot. The computational models enable a microrobot to learn to track a moving object and anticipate future positions using a CCD camera. The architecture features pre-processing modules for coordinate transformation and instantaneous orientation extraction. Learning of motor control is implemented using predictive Hebbian reinforcement-learning algorithm in the basal ganglia model. Learning of sensory predictions makes use of a combination of long-term depression (LTD) and long-term potentiation (LTP) adaptation rules within the cerebellum model. The basal ganglia model uses the visual inputs to develop sensorimotor mapping for motor control, while the cerebellum module uses robot orientation and world-coordinate transformed inputs to predict the location of the moving object in a robot centered coordinate system. We propose several hypotheses about the functional role of cell, populations in the cerebellum and argue that mossy fiber projections to the deep cerebellar nucleus (DCN) could play a coordinate ransformation role and act as gain fields. We propose that such transformation could be learnt early in the brain development stages and could be guided by the activity of the climbing fibers. Proprioceptor mossy fibers projecting to the DCN and providing robot orientation with respect to a reference system could be involved in this case. Other mossy fibers carrying visual sensory input provide visual patterns to the granule cells. The combined activities of the granule and the Purkinje cells store spatial representations of the target patterns. The combinations of mossy and Purkinje projections to the DCN provide a prediction of the location of the moving target taking into consideration the robot orientation. Results of lesion simulations based on our model show degradations similar to those reported in cerebellar lesion st
Rapid and high precision data acquisition methodology from coordinate components with free-form surface and geometrical model can be implemented widely. Typical application covers part localization, automatic calibrat...
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Rapid and high precision data acquisition methodology from coordinate components with free-form surface and geometrical model can be implemented widely. Typical application covers part localization, automatic calibration and reverse engineering. Integrated structured light vision sensor with CMM (Coordinate Measurement Machine) enhances the high-precision coordinate measurement capability. In this paper a curvature-based adaptive sampling approach and the evaluating index for the sampling precision are presented. The matching and subdividing algorithm for generating matrix-type mesh data from sample points is described. The methodology to register and merge the measured data from multiple viewpoints to model the free-form surface is also presented. Based on the given initial coordinate rotation matrix R and transformation vector T, the different viewpoints can be translated into a unique frame of reference. By introducing special coordinate of 3D space, the registered data is divided into mesh, which cover the whole surface of object. An application example for shoe modeling is described to illustrate the advantages.
A method is presented for distributed position control of the tip of a high degree of freedom tentacle. The scheme employs limited communications which occurs only between adjacent degrees of freedom. Total computatio...
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ISBN:
(纸本)0819434329
A method is presented for distributed position control of the tip of a high degree of freedom tentacle. The scheme employs limited communications which occurs only between adjacent degrees of freedom. Total computational requirements for the tentacle are linear with the number of degrees of freedom and are distributed as identical processes at joint. An iterative approach to position control allows automatic path planning around obstacles to occur. The resulting system allows complex tasks to be performed with limited computation and sensing resources. The algorithm was used as a basis for locomotion for a mobile robot with four tentacles.
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