Utilization Of Redundancy Research Articles

Robot manipulator control for hazardous waste‐handling applications

AbstractThe U.S. Department of Energy has identified robotics as a major technology to be utilized in its program of environmental restoration and waste management, and in particular has targeted robotic handling of hazardous waste to be an essential element in this program. Successful performance of waste‐handling operations will require a robot to perform complex tasks involving both accurate positioning of its end effector and compliant contact between the end effector and the environment, and will demand that these tasks be completed in uncertain surroundings. This article focuses on the development of a robot control system capable of meeting the requirements of hazardous‐waste‐handling applications and presents as a solution an adaptive scheme for controlling the mechanical impedance of kinematically redundant manipulators. The proposed controller is capable of accurate end effector impedance control and effective redundancy utilization, does not require knowledge of the complex robot dynamic model or parameter values for the robot or the environment, and is implemented without calculation of the robot inverse kinematic transformation. Computer simulation results are given for a 4 degree of freedom redundant robot under adaptive impedance control. These results indicate that the proposed controller is capable of successfully performing tasks of importance in robotic waste‐handling applications.

Task‐based configuration control of redundant manipulators

AbstractThis article establishes new goals for redundancy resolution based on manipulator dynamics and end‐effector characteristics. These goals can be accomplished by employing the recently developed configuration control approach. Redundancy resolution is achieved by controlling the joint inertia matrix or the end‐effector mass matrix that affect the inertial torques or by reducing the joint torques due to gravity loading and payload. The manipulator mechanical advantage and velocity ratio are also used as performance measures to be improved by proper utilization of redundancy. Furthermore, end‐effector compliance, sensitivity, and impulsive force at impact are introduced as redundancy‐resolution criteria. The new goals for redundancy resolution presented in this article allow a more efficient utilization of the redundant joints based on the desired task requirements. Simple case studies using computer simulations are described for illustration.

Efficiency Calculation and Sensor Fault Detection in a Large Scale Plant

With the sale of large-scale chemical plants, the plant constructor undertakes to fulfil certain guaranteed values. For a nitric acid plant one of the essential guarantee figures is the acid yield. Consequently, a check of this value is a central item during the plant acceptance test procedure (test and guarantee runs). Until now stationary material balances have been used to determine the yield. However, the result may be falsified for two major reasons. First the measurements entering the calculation may exhibit systematic errors where the investigation is difficult. Another source of error is the time lag in the measurements caused by the plant dynamics. In the present report the material balances were determined with the plat dynamics taken into account, in addition the measurements made during the process were monitored. This was done on the one hand by utilizing the redundancy of the available measurements by so-called voters (which form weighted means) and on the other hand by the use of mathematical models (input-variable, output-variable and parameter observers). In order to design the observers mathematical models of the various sources of error (error hypotheses) were introduced and the size of the postulated error was estimated. In order to establish the dynamic model of the overall plant the process was shared into subsystems. Through correlation of the individual subsystems and utilization of hardware redundancy it was possible to recognize faulty measurements and obtain an improved material balance.

Cartesian control of redundant robots

AbstractThis article presents a Cartesian‐space position/force controller for redundant robots. The proposed control structure partitions the control problem into a nonredundant position/force trajectory tracking problem and a redundant mapping problem between Cartesian control input Fϵ Rm and robot actuator torque Tϵ Rn(for redundant robots, m < n). The underdetermined nature of the F → T map is exploited so that the robot redundancy is utilized to improve the dynamic response of the robot. This dynamically optimal F → T map is implemented locally (in time) so that it is computationally efficient for on‐line control; however, it is shown that the map possesses globally optimal characteristics. Additionally, it is demonstrated that the dynamically optimal F→T map can be modified so that the robot redundancy is used to simultaneously improve the dynamic response and realize any specified kinematic performance objective (e.g., manipulability maximization or obstacle avoidance). Computer simulation results are given for a four degree of freedom planar redundant robot under Cartesian control, and demonstrate that position/force trajectory tracking and effective redundancy utilization can be achieved simultaneously with the proposed controller.

Criteria optimization using self‐motion of a 9‐R redundant robot

AbstractUsing inverse kinematic solutions for self‐motion of a class of 9‐R redundant robots, a conjugate‐gradient based constrained optimization scheme for incremental trajectory planning is formulated. The proposed scheme has been evaluated and proved to be an efficient optimization method for redundancy utilization. It can also be used for studying 7‐R and 8‐R manipulators by simply restricting to one‐variable and two‐variable optimization, respectively. In contrast with other approaches which are based on the Jacobian, our scheme exploits the availability of closed‐form inverse kinematic solutions to give more effective and accurate results.

Advanced Carrier Systems and Telerobotics

Basic concepts for wide range telerobotic systems working in complex environments with obstacles are described. These concepts include the cooperation of man and machine to achieve a high degree of autonomy, the usage of CAD models and advanced sensory systems, a functional structuring of the control system with neutral interfaces, and the utilization of kinematic redundancy for obstacle avoidance and increase of dexterity. Three different systems presently under development are described which follow these concepts.

Redundant robot control using task based performance measures

AbstractThe joint velocities required to move the end‐effector of a redundant robot with a desired linear and angular velocity depend on its configuration. Similarly, the joint torques produced due to the force and moment at the end‐effector also depend on its configuration. When the robot is near a singular configuration, the joint velocities required to attain the end‐effector velocity in certain directions are extremely high. Similarly, in some configurations the joint torque produced at certain joints may be high for a relatively small magnitude of external force. An infinite number of trajectories in the joint space can be used to achieve a desired end‐effector trajectory for redundant robots. However, a joint trajectory resulting in robot configurations requiring lower joint velocities or joint torques is desired. This may be achieved through a proper utilization of redundancy. Local performance measures for redundant robots are defined in this article as indicators of their ability to follow a desired end‐effector trajectory and their ability to apply desired forces at the end‐effector. Thus, these performance measures depend on the task to be performed. Control algorithms which can be efficiently applied to redundant robots to improve these performance measures are presented. These control algorithms are based on the gradient projection method. Gradients of the performance measures used in the control schemes result in simple symbolic expressions for “real world” robots'. Feasibility and effectiveness of these control schemes is demonstrated through the simulation of a seven‐degree‐of‐freedom redundant robot derived from the PUMA geometry.

Task Compatibility of Manipulator Postures

In performing a manipulation task, humans tend to adopt arm postures that most effectively utilize the motion and strength capabilities of the arm. Selecting arm postures that are compatible with the task requirements has become almost instinctive to humans. By mimicking this approach in robotic manipulation, we can exploit the full capability of a manipu lator in performing a task. An index is proposed for measur ing the compatibility of manipulator postures with respect to a generalized task description. The manipulator is viewed as a mechanical transformer, with joint space velocity and force as input and task space velocity and force as output. Optimi zation of the index corresponds to matching the velocity and force transmission characteristics to the task requirements. The applications of this index to manipulator redundancy utilization and workspace design are also discussed.

Task-Priority Based Redundancy Control of Robot Manipulators

In this paper, we describe a new scheme for redundancy control of robot manipulators. We introduce the concept of task priority in relation to the inverse kinematic problem of redundant robot manipulators. A required task is divided into subtasks according to the order of priority. We propose to determine the joint motions of robot manipulators so that subtasks with lower priority can be performed utilizing re dundancy on subtasks with higher priority. This procedure is formulated using the pseudoinverses of Jacobian matrices. Most problems of redundancy utilization can be formulated in the framework of tasks with the order of priority. The results of numerical simulations and experiments show the effectiveness of the proposed redundancy control scheme.

Stimulus Processing Models from Psychology: Can We Use Them in Cartography?

Serial/parallel and holistic models have been developed by psychologists to explain how subjects compare two stimuli, a function map readers also perform with symbols in maps. These models, along with the related concept of integral and separable categories of stimulus dimensions, have potential use in cartography. A review of these models suggests: the utility of redundancy to aid discrimination, the possible use of psychological space rather than physical space as a predictor of reader performance, and the kinds of dimensions that should be used for multivariate symbols.

The utilization of intraword structure in poor readers: Experimental evidence and a training program

The paper is concerned with the utilization of linguistic structure in reading-disabled children. Discussing models of word recognition, it is argued that the ‘lexical’ approach need not necessarily imply ‘holistic’ processing; intervening stages related to the utilization of intraword structure are also compatible with the basic assumptions of the lexical model. Two experiments using pseudowords as stimuli are reported, showing that poor readers from third grade are inferior to good readers in the utilization of intraword redundancy (Experiment 1) and that poor readers' performance with redundant stimuli can be increased when the stimuli are grouped into syllables (Experiment 2). A reading intervention program is then presented, in which the children are taught how to segment words into syllables. Fifteen poor readers from the third grade were trained for 12 sessions. The success of the program was tested in an oral reading test and in a laboratory experiment investigating changes in the utilization of intraword redundancy after training.

Analysis and Control of Articulated Robot Arms with Redundancy

Industrial robot applications have seen remarkable growth in numbers and in diversity of uses. In configuration, it is also slowly changing from cartesian and cylindrical coordinate types to articulated one mainly due to the fact that articulated robot arms are more flexible and versatile. From the view point of control, however, arms of this type possess certain inherent problems. One concerns the nonlinear relation between the position and orientation of the robot hand and the rotational angles of the joints of the arm. Another problem concerns the existence of singular points in the state space of joints, which reduces the robot's degree of freedom. Although it has sometimes been claimed that redundant arms can effectively overcome the problem of singularity and increase flexibility and versatility, these have yet to be studied in full. In this paper, the manipulatability and redundancy of multi-articulated robot arms are analyzed and utilization of redundancy is discussed. Experimental results are also presented concerning the utilization of redundancy for trajectory control with provisions for an obstacle.

Observability and redundancy classification in process networks: Theorems and algorithms

The utility of observability and redundancy in characterizing the performance of process data estimators was established in previous studies [10]. In this paper two classification algorithms for determining local and global observability and redundancy for individual variables and measurements are presented. The concepts of biconnected components, perturbation subgraphs and feasible unmeasurable perturbations are introduced, and their properties are developed and used to effect classification, simplification and dimensional reduction. Step-by-step application of these algorithms is illustrated by examples.

Perceptual deficit in schizophrenia: a defect in redundancy utilization, filtering or scanning?

The perception by schizophrenic patients of stimuli with more than one feature (dimension) was investigated using psychiatric and non-psychiatric control groups. Indices of the ability (a) to make use of redundant stimulus cues, (b) to 'screen out' or filter irrelevant stimulus features, and (c) to scan the perceptual field for relevant stimulus features, indicated that only filtering was consistently poor in schizophrenia. It has been suggested that the schizophrenic patient may tend to perceive his environment in an undifferentiated holistic manner rather than in an analytic manner and the implication for the theory of left hemisphere pathology in schizophrenia is discussed. However, the performance of the schizophrenic subjects did not differ significantly from that of the group of depressed patients, which suggests that the selective attention deficits previously observed in schizophrenia are not specific to the disorder.

Mutation-absorption model of the enzyme.

Gradual changes in function of proteins in response to single changes in primary structure are often observed to occur and are a necessary condition for evolution by variation and natural selection at the protein level. A probabilistic (entropy theory_ analysis of the effect of changes in primary structure on three-dimensional shape and function shows that such gradualism is based on the presence of a control system in the molecule involving a definite general form of structure-function degeneracy. The assumptions of the analysis are that primary structure determines tertiary structure (or a thermal distribution of tertiary configurations and allosteric forms), tertiary structure determines function (characterized by rate and other parameters), and that certain features of tertiary structure may be specialized for particular functions. The main conclusion is that embodied in the molecule is a subsystem which serves as a buffer, absorbing mutation or other forms of genetic variation and expressing these as graceful variations in features of the shape critical for function. This buffer system may be realized by numerical redundancy of amino acids or other mechanisms which increase the redundancy of weak interactions responsible for folding, utilization of amino acids having a greater number of analogs with redundant features, or local and global structural formats which allow for more effective utilization of redundancy. The mutation-absorption model has implications for the interpretation of structure-function relations in biology, the topology of the adaptive landscape, the interpretation of isoenzymes and allozymes, the relationship between selection and neutralism in evolution, and the relation between the complexity of and energy required by biological systems and the effectiveness of evolutionary optimization.

Mutation-absorption model of the enzyme

Gradual changes in function of proteins in response to single changes in primary structure are often observed to occur and are a necessary condition for evolution by variation and natural selection at the protein level. A probabilistic (entropy theory) analysis of the effect of changes in primary structure on three-dimensional shape and function shows that such gradualism is based on the presence of a control system in the molecule involving a definite general form of structure-function degeneracy. The assumptions of the analysis are that primary structure determines tertiary structure (or a thermal distribution of tertiary configurations and allosteric forms), tertiary structure determines function (characterized by rate and other parameters), and that certain features of tertiary structure may be specialized for particular functions. The main conclusion is that embodied in the molecule is a subsystem which serves as a buffer, absorbing mutation or other forms of genetic variation and expressing these as graceful variations in features of the shape critical for function. This buffer system may be realized by numerical redundancy of amino acids or other mechanisms which increase the redundancy of weak interactions responsible for folding, utilization of amino acids having a greater number of analogs with redundant features, or local and global structural formats which allow for more effective utilization of redundancy. The mutation-absorption model has implications for the interpretation of structure-function relations in biology, the topology of the adaptive landscape, the interpretation of isoenzymes and allozymes, the relationship between selection and neutralism in evolution, and the relation between the complexity of and energy required by biological systems and the effectiveness of evolutionary optimization.

The Independence of Letter, Word, and Meaning Identification in Reading

ed from context. Feature analytic model of meaning identification We suggest the term meaning identification to embrace both comprehension and the utilization of semantic redundancy in sequences of words because the process by which such information is extracted from text by the skilled reader may be regarded as essentially no different from the process by which he identifies letters or words. Featural information from the visual array is analyzed and allocated to reduce uncertainty in: a] the domain of letter categories, for letter identification b] the domain of word categories, for word identification or c] the domain of cognitive structure, for meaning identification. Obviously it cannot be asserted that the domain of meaning to which visual information is applied in meaning identification is a domain of categories in the same way that sets of letters or of words constitute domains. Rather, comprehension may be conceptualized as either a i)ermanent or temporary reorganization of cognitive structures or the rearrangement of feature specifications on semantic feature lists. It is also not easy to identify the mechanisms by which meaning identification reduces the set of word categories (or reduces the size and increases the number of criterial sets for a number of categories in the word domain) to produce the lowered information threshold for words in sentences. However, reluctance to speculate 3. We are aware that some of the sequential constraint in a sequence of words may often be syntactic as well as semantic, but the syntactic component is subordinate in normal language (Treisman, 1965) as well as difficult to disentangle. It is convenient to subsume syntactic and semantic information in the terms meaning and compre-

Optimizing the Utilization of Redundancy of the Apollo Acceptance Checkout Equipment

Abstract This article describes a model useful for optimizing the utilization of redundant subsystems in complex test systems. Developed for the Apollo Acceptance Checkout Equipment (ACE), the procedure describes the critical operational modes of the test system; predicts system reliability under various configurations by the use of a Markovian process; and assesses penalties for the use of redundant elements. A ranking scheme then permits management to select the optimum configuration for each critical test.