A reference force-tracking impedance control system is proposed, consisting of a conventional impedance controller in the inner-loop and a trajectory modifying controller in the outer-loop for force-tracking. The desi...
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A reference force-tracking impedance control system is proposed, consisting of a conventional impedance controller in the inner-loop and a trajectory modifying controller in the outer-loop for force-tracking. The design of the outer-loop is presented and the stability of the two-loop control system is analyzed. A computationally efficient control algorithm for the inner-loop is suggested. Simulation results are presented. The controller is able to achieve excellent position and force-tracking with unknown environment stiffness and the presence of a burr on the tracking surface.< >
This work explores a method for path planning for a robot in an environment that consists of stationary and moving obstacles. The technique uses binary partitioning of the environment by the obstacles to establish and...
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This work explores a method for path planning for a robot in an environment that consists of stationary and moving obstacles. The technique uses binary partitioning of the environment by the obstacles to establish and analyze the spatial relationship between robot and obstacles. Hyperplanes are used to obtain recursively a disjoint set of D-dimensional cells, with each cell designated as belonging to either the interior or the exterior of the set. An overt idea of binary space partitioning as a representation of polytopes is given. Thus, the space-time configuration of free space is viewed as disjoint polytopes; each point in space-time is considered a map into a unique polytope. A traversal of the tree is used to obtain a linear order which gives the collision probability with the environment. Adjacent polytopes between the start and goal polytopes are then utilized to obtain a trajectory. Current implementation for a 2D static environment is discussed.< >
Dynamic segmentation is a method for improving the performance of cooperating tasks executed on loosely coupled multiprocessors. Four different data transfer techniques that can be used for intersegment data transfers...
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Dynamic segmentation is a method for improving the performance of cooperating tasks executed on loosely coupled multiprocessors. Four different data transfer techniques that can be used for intersegment data transfers in dynamically segmented buses are analyzed. Preemptive data transfers are considered for uniform message latencies and results are provided for message latency comparisons using various locality factors. These results indicate dynamic segmentation improves performance considerably, at a fraction of the cost of more complex interconnection networks such as multiple buses.< >
A novel method for solving the motion planning problem in the presence of moving obstacles is presented. Compared to previous approaches, the proposed method is more general in that obstacles are allowed to move with ...
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A novel method for solving the motion planning problem in the presence of moving obstacles is presented. Compared to previous approaches, the proposed method is more general in that obstacles are allowed to move with translation and rotation at nonlinear velocity. Using path/velocity decomposition, the method emphasizes the development of an efficient algorithm for collision detection between the robot and moving polygons. This algorithm is devised using transversability vector theory to determine the geometric relationships between any two convex polygons or convex components of concave polygons. The interference between the robot and the moving obstacles is detected and registered on the constraint map to represent time constraints on the robot's motion along the path. The constraint map is then used for velocity planning using a simple algorithm. The problem of a robot crossing the street is used as an example for computational analysis.< >
A parallel-jaw type multiple-d.o.f. robot hand is designed and implemented to manipulate workpieces within the hand by rotation and translation. An efficient manipulator control algorithm and part mating application i...
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A parallel-jaw type multiple-d.o.f. robot hand is designed and implemented to manipulate workpieces within the hand by rotation and translation. An efficient manipulator control algorithm and part mating application is developed. A simulation result is also presented to show the changes of force during part insertion to verify the models developed.< >
The authors investigate dexterity measures of a manipulator based on its Jacobian matrix. The goal is to derive dexterity measures which can be used for both design and control of a manipulator. Generally, a dexterity...
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The authors investigate dexterity measures of a manipulator based on its Jacobian matrix. The goal is to derive dexterity measures which can be used for both design and control of a manipulator. Generally, a dexterity measure must be independent of the scale of a manipulator for design, and must be expressed analytically so that it can be used for real-time control. Every dexterity measure must bear a physical meaning. The measure of manipulability has an analytical expression, but it depends on the scale of a manipulator. On the other hand, the condition number is independent of the scale, but cannot be expressed analytically. These two main problems (scale dependency and analytical expression) of previous dexterity measures derived from the Jacobian matrix are solved and applied in design and control of manipulators. In addition, a dexterity measure called the measure of isotropy is introduced.< >
For robots to traverse rugged terrain successfully using legged locomotion, they need not only constantly to maintain structural stability but also, and perhaps more importantly, to detect and adapt to changes in the ...
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For robots to traverse rugged terrain successfully using legged locomotion, they need not only constantly to maintain structural stability but also, and perhaps more importantly, to detect and adapt to changes in the terrain properties. The authors address the issue of exploration to extract material properties from a given surface for the specific purpose of aiding in and improving the quality of legged locomotion. While it is important to evaluate terrain properties prior to the start of locomotion, it is even more important to evaluate these properties actively during locomotion so that the robot does not sink, slip or fall. It is proposed that the legs of a robot be used not only for stepping and walking but also as probes to examine those properties of the surface that would contribute to the efficiency of locomotion, one way or another. The proposed framework for active perception for legged locomotion suggests that for stable stepping and walking in an unknown environment, it is necessary actively to recover the material properties of penetrability, compliance and surface traction from the supporting surface. These attributes must be recovered by exploratory procedures that are built into the mobile robotic system. This paper focusses on the implementation of the perceptual scheme so that feedback from the measurement of material properties is used to control robot foot forces during legged locomotion.< >
A new approach to solving the collision detection problem for mobile robots in the presence of moving obstacles is proposed. Both the robot and obstacles in the two-dimensional space are assumed to be polygonal and ar...
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A new approach to solving the collision detection problem for mobile robots in the presence of moving obstacles is proposed. Both the robot and obstacles in the two-dimensional space are assumed to be polygonal and are composed of a set of convex polygons. The half-plane representation uses an algebraic method to describe the object motion including translation and rotation through time. Compared with previous methods, the proposed representation is more general in that obstacles are now allowed to move at nonconstant velocities. To detect collision between polygonal objects, a traversability vector method was developed. Traversability vectors are a simple mechanism used to analyze geometric constraints imposed by polygons. Using these vectors, a simple algorithm for predicting collision is derived. computer simulations were conducted to show the feasibility of the proposed method.< >
The authors present experimental results from a strategy for stable hard-on-hard impacts of a robot manipulator, and show how this method fits into the framework of force control. Previously proposed methods of impact...
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The authors present experimental results from a strategy for stable hard-on-hard impacts of a robot manipulator, and show how this method fits into the framework of force control. Previously proposed methods of impact control are reviewed, and their inadequacies are revealed. A fourth-order model of an arm/sensor/environment system is reviewed. It is pointed out how proportional gain force control with feedforward and impedance control are equivalent when the environment is stiff. An analysis of the model and the controllers shows the gain selection that provides the best impact response. Extensive experimental results confirm the correctness of the model, the equivalence of the controllers, and the efficacy of this impact control strategy.< >
The use of a single-camera 3D computer vision system as a position sensor in order to perform robot calibration is examined. A vision feedback scheme, termed vision-guided robot control (VRC), that can improve the acc...
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The use of a single-camera 3D computer vision system as a position sensor in order to perform robot calibration is examined. A vision feedback scheme, termed vision-guided robot control (VRC), that can improve the accuracy of a robot in an online iterative manner is described. This system demonstrates the advantage that can be achieved by a Cartesian space robot control scheme when end-effector position and orientation are actually sensed instead of calculated from the kinematic equations. The viability of using a vision system for robot calibration is demonstrated by experimentally showing that the accuracy of a robot can be drastically improved. The vision system can also be used to determine the repeatability and accuracy of a robot in a simple, efficient, and quick manner. Experimental work with an IBM electric drive robot and the proposed vision system produced a 97- and 145-fold improvement in the position and orientation accuracy of the robot, respectively.< >
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