This paper presents an algorithm for finding a kinematically feasible path which satisfies a given set of nonholonomic constraints while enforcing both equality and inequality constraints on the configuration vector. ...
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This paper presents an algorithm for finding a kinematically feasible path which satisfies a given set of nonholonomic constraints while enforcing both equality and inequality constraints on the configuration vector. The path planning problem is transformed from a finite time nonlinear control problem into a static root finding problem which is iteratively solved. By using an exterior penalty function method, the constrained root finding problem is converted to an unconstrained problem. Convergence of the algorithm depends upon a certain gradient operator being full rank. It has recently been shown that, in the absence of any configuration inequality constraints, the full rank condition is generic. In this paper, we show the full rank condition for a special inequality constraint case. An experiment in which the algorithm is applied to an actual double tractor-trailer vehicle is presented.< >
A general approach to model-based multisensor data fusion using a minimal representation size criterion is described. Each sensor is modeled by a general constraint equation which defines a data constraint manifold (D...
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A general approach to model-based multisensor data fusion using a minimal representation size criterion is described. Each sensor is modeled by a general constraint equation which defines a data constraint manifold (DCM), and observed sensor data populate the measurement space according to these constraints. The choice of multisensor interpretations is based on a minimal representation size criterion which evaluates the complexity through correspondence and encoded errors weighted by relative sensor accuracy and precision. This general framework automatically selects subsets of data features called constraining data feature sets (CDFS) and chooses the CDFS corresponding to a minimal representation interpretation of the observed data. The resulting procedure fuses heterogeneous sensor readings into a single estimation method. The method is illustrated for a visual and tactile data fusion example. The approach generalizes to problems with non-geometric models, and can be used for multisensor system identification in other domains such as process control.< >
A system for exhaustively inspecting a workpiece, not merely certain features, is presented. The system is based on comparing a volumetric representation of a reference object to a volumetric representation of an actu...
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A system for exhaustively inspecting a workpiece, not merely certain features, is presented. The system is based on comparing a volumetric representation of a reference object to a volumetric representation of an actual object iteratively created from sensor data. The use of volumetric representations gives this approach a number of distinct advantages over the more traditional boundary-based inspection methods. The method is capable of handling arbitrarily complex geometries and does not rely on the identification of features. It lends itself naturally to a multisensor environment, and facilitates true 3-D inspection as opposed to methods that require dimensional reductions of data by projection onto a 2-D plane. The authors focus on an important aspect of volumetric inspection which is the automatic generation of a sequence of sensor operations that will acquire the complete geometry of the object being inspected.< >
There are numerous applications in which robots are needed to assist rather than replace human operators. These applications typically involve either work in a dangerous environment or performing tasks that are physic...
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There are numerous applications in which robots are needed to assist rather than replace human operators. These applications typically involve either work in a dangerous environment or performing tasks that are physically impossible for humans to accomplish by themselves. Robots used in this mode do not need to be autonomous because they can essentially be controlled by the operator. Nonetheless, it is difficult for an operator to flawlessly control a robot with a large number of degrees of freedom. Therefore, an intelligent control system is needed to correct and improve the operator's input to the robot. In this paper the authors discuss a central component in this control system known as the variably-autonomous trajectory generator (VATG). The VATG combines input from the operator with input from one or more autonomous control modules (CM) to generate the robot trajectory. The amount of impact the autonomous CMs will have on the overall trajectory will depend on a number of factors such as the task being performed and the sensing modalities available, hence the authors refer to this type of control as being variably-autonomous.< >
General-purpose CAD-based inspection of a manufactured workpiece often involves comparing a part model created using intensity or range images of the part to a toleranced reference model of the part. Before this compa...
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General-purpose CAD-based inspection of a manufactured workpiece often involves comparing a part model created using intensity or range images of the part to a toleranced reference model of the part. Before this comparison can be made, however, the sensed object model must be registered to the reference object model. Most registration approaches assume that it is possible to identify and match features in the models and that the object models represent very similar geometries. A registration approach that deals with featureless dissimilar models is presented, and experimental results are demonstrated. Although the need for such an approach was motivated by needs in inspection, the approach is very general and can be used in a variety of other applications.< >
The kinematic path planning problem of a nonholonomic system can be posed as a point-to-point control problem of a nonlinear system. This system has the property that it is not locally stabilizable but is globally con...
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The kinematic path planning problem of a nonholonomic system can be posed as a point-to-point control problem of a nonlinear system. This system has the property that it is not locally stabilizable but is globally controllable. In this paper, we present a new algorithm for constructing a feasible path between specified initial and final configurations. Polyhedral constraints in both configuration and non-configuration spaces (possibly non-convex) can also be incorporated in this framework. The algorithm is based on the assumption that the system is usually controllable about a non-trivial trajectory, which is true for many cases. An initial trajectory is iteratively warped until the desired final configuration is reached. Examples of a front-wheel driven car, and tractors with one, two, and three trailers are included to illustrate the efficacy of the proposed algorithm.
A class of newton-type algorithms is effective in solving the kinematic path planning problem for a system with nonholonomic equality constraints. A key result in this approach has been the generic full rank condition...
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A class of newton-type algorithms is effective in solving the kinematic path planning problem for a system with nonholonomic equality constraints. A key result in this approach has been the generic full rank condition of a certain gradient operator. We have extended this method to path planning problems with inequality constraints and shown its efficacy in solving some challenging problems, but a similar genericity result is not currently available. In this paper, we present some extension of our algorithm for nonholonomic path planning with equality and inequality constraints and show the generic full rank condition for a special case. Simulation examples involving a steerable tractor-trailer vehicle and experiment results of a quarter-scale car with a trailer are presented.< >
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