Dynamic equations of chain structured robotic manipulators with compliant links and joints are developed in a non-recursive symbolic form. A program is developed in REDUCE to automate the symbolic expansion of these equations for any given chain structured manipulator. The symbolic non-recursive form of dynamic model is particularly suitable for controller synthesis and real-time control implementations. The link flexibility is included in the formulation using assumed mode shapes. The mode shapes and the parameters that are functions of the mode shapes are kept in symbolic form so that once a symbolic model is generated, different types of mode shapes can be studied using the same model. Because of the structural similarity between the developed equations and the well known rigid manipulator equations, the computer automated symbolic expansion capability presented here are likely to be utilized widely by many other researchers in the area who are already familiar with rigid manipulator problems.

A real-time obstacle avoidance algorithm is proposed for autonomous mobile robots. The algorithm is sensor-based and consists of a H-mode and T-mode. The algorithm can deal with a complicated obstacle environment, such as multiple concave and convex obstacles. It will be shown that the algorithm is more efficient and more robust than other sensor-based algorithms. In addition, the algorithm will guarantee a solution for the obstacle avoidance problem. Since the algorithm only takes up a small computational time, it can be implemented in real time.

The paper describes a free space modeling method by multivalue coding. Each code defines some numerical values representing a set of cells from a grid. The idea consists in using the grid as a Karnaugh board whose rows and columns are binary coded rather than Gray coded. This operating method allows to define, for each code, its grid location and allows numerical comparison in order to locate a code relatively to another. This aspect is helpful for path planning. The free space model is represented by a switching function or a tree to which boolean algebra rules and mathematic operations are applied. We describe an application to mobile robot path planning.

For the navigation of a mobile robot, the determination of its absolute location is one of essential tasks. This paper proposes a stripe type landmark which enables us to develop a fast algorithm to calculate the distance and orientation of a camera relative to the landmark. Exact and closed form solution of the camera location is obtained from the geometric relation between the pattern of landmark and its projected image. Since the presented algorithm requires only one row of the mark image, determination of the location can be processed in real-time. In addition, the mark can be identified using the projective invariant of the original mark pattern without any additional patterns. The effect of the error sources on the location determination is analyzed through a series of simulations and experiments. The applicability of the algorithm to mobile robots is discussed using the experimental results.

An optimization technique based on the well known Dynamic Programming Algorithm is applied to the motion control trajectories and path planning of multi-jointed fingers in dextrous hand designs. A three-fingered hand with each finger containing four degrees of freedom is considered for analysis. After generating the kinematics and dynamics equations of such a hand, optimum values of the joints torques and velocities are computed such that the finger-tips of the hand are moved through their prescribed trajectories with the least time or/and energy to reach the object being grasped. Finally, optimal as well as feasible solutions for the multi-jointed fingers are identified and the results are presented.

In this paper, we discuss the accurate and robust sliding mode tracking control for highly nonlinear robot manipulators using a disturbance observer. Due to the modeling error or environmental uncertainties, sliding mode control may present a significant chattering problem by using a conventional Sliding Mode Control (SMC) which can obtain the desired tracking performance, because the controller design is carried in the uncertainty space of the system parameters.

To solve this chattering problem, the efficient compensation of the disturbance observer has been introduced. Thus the design of the proposed SMC is not influenced by the modeling error or parameter uncertainties.

To ensure bounded stability, the proposed sliding mode controls have been analysed in a preliminary lemma and two main theorems. The stability of the proposed control method is proved in this paper, and the efficiency of the control algorithms has been demonstrated by simulations for a position tracking control of a two-link robot subject to parameter and payload uncertainties.

This paper describes the generation of profiles of jaws of robot grippers for holding parallel-sided workpieces. The profiles are effectively ruled surfaces. The line segments of the ruled surfaces are designed to contact workpieces of different thicknesses. The optimum design of these gripping surfaces is considered in this paper

This paper focuses on the implementation of a dual-mode controller for the maneuver of a single link flexible robotic arm. The joint angle trajectory tracking is accomplished by a proportional and derivative PD and a feedforward controller. Based on the pole placement technique, a linear stabilizer is designed for elastic mode stabilization. The stabilizer is switched on when the trajectory reaches the vicinity of the terminal state, and the effect of switching time on arm vibration is investigated. An optical deflection sensor is used for on-line measurements of elastic deflections, and also used for the prediction of the static deflection of the arm in the target position. The robustness of the linear stabilizer at varying pay loads is presented.

The mass balancing of robotic manipulators has been shown to have favorable effects on their dynamic characteristics. In actual practice, however, since conventional manipulators have flexibility at their joints, the improved dynamic properties obtainable for rigid manipulators may be influenced by those joints flexibilities. This paper investigates the effects of the joints flexibility on the dynamic properties and the controlled performance of a balanced robotic manipulator. The natural frequency distribution and damping characteristics were investigated through frequency response analyses. To evaluate the dynamic performance a series of simulation studies of the open-loop dynamics were made for various trajectories, operating velocities, and joint stiffnesses. These simulations were also carried out for the balanced manipulator with a PD controller situated inside the motor control loop. The results show that, at low speed, the joints flexibility does but little influence the performance of the balanced manipulator, but at high speed it tends to render the balanced manipulator susceptible to vibratory motion and yields large joints deformation errors.

The paper presents a geometric method for collision-free manipulator path planning in 3D Euclidean space with polyhedral obstacles. It ensures that none of the links nor the manipulator tip collide with the objects. The method is computationally very cheap and it does not require intensive off-line preprocessing. Hence, it is real-time applicable if the information about obstacles positions and shapes is obtained from a higher control level. The trajectories generated lie within the reachable workspace. The method is implemented on a VAX 11/750 computer and the simulation results are included.

ISRA is a support system for robot programming. It provides a means to automatically (guided by knowledge) convert a user's request, expressed in the natural language, into the appropriate conceptual model of the required task. This model incorporates information required for the understanding, planning and sensory-guided performance of the required robotic task.

To develop this system we applied the Natural Computation method. We considered natural information processing by humans during synthesis and interpretation of robotic programs, and then constructed an approximate conceptual model of the relevant dynamically changing real world.

Such a model has to be suitable (e.g. representable and executable) for efficient computer processing. This paper presents the results of a case study which shows that methods built by formalizing human information processing in the robotic domain may be efficiently and naturally implemented in ISRA. It provides evidence that the structure and behavior of ISRA's competence representation and algorithm are comparable with the psychological behavior of humans, as required by the Natural Computation method.

The case study illustrates the use of ISRA for the first phase of an assembly program synthesis i.e. planning of all valid assembly sequences.

This paper presents at first a static and kinematic analysis of closed chains mechanisms which permits to deduce different possible fully parallel architectures. Then we focus on a particular parallel architecture with C5 links designed to perform precise assembly tasks. A general modeling of this C5 parallel robot is presented. Two typical assembly tasks in the automotive industry are also proposed; the first one uses the C5 links parallel robot as a left-hand device, while the second one uses it as the terminal tool of a sequential manipulator.

A new method of optimal cost trajectory planning based on a graph searching algorithm is presented. Various heuristic functions which play the key role in the construction of effective algorithms for solving such problems are proposed. Some numerical examples are given based on the kinematic and dynamic models of a IRb-6 ASEA robot. This method rooted in AI has less computational complexity than a dynamical programming method applying to the same optimal-cost trajectory planning problem.

A binary tactile image feature extraction algorithm using image primitive notation and perceptrons is presented. The basic image segments are defined as geometric factors by which the image structure is described so that effective feature values such as image shape, image size, perimeter and texture may be extracted on the basis of local image computation. The local property of the tactile image computation is evaluated by the concept called order of the perceptrons and based on this feature extraction algorithm, an efficient tactile image recognition system is realised.

This paper describes the structure of the program package for manipulator modeling, control law synthesis and simulation SYM. While the underlying algorithms have been explained elsewhere, this paper puts emphasis on SYM as a program environment with both research and educational purposes. The control law synthesis in symbolic form, as well as system simulation, are given in more details since those features have been introduced into SYM recently. As an illustration we present few instances of SYM outputs which depict main steps in manipulator control system creation process: manipulator structure as a 3D scheme, control law definition form and system simulation results as 2D plots.

The force distribution problem for legged vehicles on rough terrain is considered. A general formulation of the force distribution problem in which the feet contact the ground at arbitrary inclinations, is presented. Three techniques are used to solve the force distribution problem for three representative tasks. The Moore-Penrose pseudo-inverse, a numerical optimization scheme and an approximation to the optimal solution are described. The optimal scheme computes the forces which minimize the maximum ratio of tangential foot reaction force to foot normal force. The approximation is used to achieve certain desirable characteristics of the optimal scheme with considerably less computational resources.

We have suggested a novel approach to autonomously navigate a full sized autonomous vehicle that separately treats vehicle control and obstacle detection. In this paper we discuss the vehicle control that has enabled our autonomous vehicle to travel at speeds upto 20mph. We point out the limitations of existing schemes that restrict their consideration to kinematic models and show that it is possible to obtain an increase in performance through the use of approximate dynamical models that capture first–order effects. Our approach combines such a modeling philosophy with accurate feedback in world coordinates from sensors that have only recently become available. Experimental results of our implementation on NavLab, a modified van at CMU, are presented.

This paper presents a framework for the design of a hierarchical Simulator of a robotized sequential technological process. The framework employs concepts of discrerte event simulation modelling. The Simulator consists of two layers: the Simulator of a robot and technological process, and the interpreter and planner of robot tasks. A format specification of both layers is presented. The proposed simulation approach is expected to result in significant improvements in the robot task plan generation and in higher efficiency of a technological process.

The kinematic control of a planar manipulator with several-degrees of redundancy has been a difficult problem because of the heavy computational burden and/or lack of appropriate techniques. The extended motion distribution scheme, which is based on decomposing a planar redundant manipulator into a series of nonredundant/redundant local arms (referred to as subarms) and distributing the motion of an end-effector to subarms at the joint velocity level, is proposed in this paper. The configuration index, which is defined as the product of minors corresponding to subarms in the Jacobian matrix, is used to globally guide the redundant manipulators. To enhance the performance of the proposed scheme, a self-motion control, which handles the internal joint motion that does not contribute to the end-effector motion, can be used optionally to guarantee globally optimal manipulation. The repeatability problem for the redundant manipulators is discussed using the proposed scheme. The results of computer simulations are shown and analyzed in detail for planar 8-DOF and 9-DOF manipulators, as examples.

This paper outlines a method for control of robotic systems for part sorting operations in unstructured manufacturing environments. The sorting is accomplished simply and without any change in the kinematic structure of the robot or any need for inclusion of complicated external sensory systems. The method developed is based on the inherent relationship between the mass of parts to be carried and the maximum velocity of the tool centre point attainable along certain specified paths.

The actuators' maximum velocity is detected and is communicated to a devised expert system. The expert system uses this maximum velocity as a part of its matching procedure for the purpose of part sorting.