For a manipulator which works in a given fixed environment, like in manufacturing plants for instance, the control system may be designed in a fixed definite way. But when the characteristics of this environment is subject to variations, e.g. change in the mass of the object to be moved, it is necessary to endow the manipulator with some versatility which allows it to adapt itself to the new working conditions. The purpose of the paper is to show that the use of links with varying inertia is a possible way to achieve this flexibility.

A new model for the construction of a sonar map in a specular environment has been developed and implemented. In a real world, where most of the object surfaces are specular ones, a sonar sensor surfers from a multipath effect which results in a wrong interpretation of an object's location. To reduce this effect and hence to construct a reliable map of a robot's surroundings, a probabilistic approach based on Bayesian reasoning is adopted to both evaluation of object orientations and estimation of an occupancy probability of a cell by an object. The usefulness of this approach is illustrated with the results produced by our mobile robot equipped with ultrasonic sensors.

This paper reviews some current research problems in Artificial Intelligence applied to robotics, in particular the processing of sensory information and robot programming. It is perceived that much progress has been made in applying AI techniques to particular isolated tasks, but the important theme at the leading edge of the AI-based robotics technology seems to be the interfacing of the subsystems into an integrated environment. This requires flexibility of the subsystems themselves. But on the other hand it also increases the flexibility of the integrated system in that it broadens the variety of ways for solving problems through functional combination of the subsystems. The presentation in this paper is illustrated by examples from the hardware and software environment of the advanced robotics research at the Turing Institute.

This paper describes a novel form of navigation aid for mobile robots. It is suggested that a robot lay a heated trail to mark its path. This information about the robot trajectory can be used to assist a robot when it performs area coverage operations such as floor cleaning or allow a robot to follow the path previously taken by itself or another robot. Prototype devices for laying and tracking a heat trail are described and details of their performance are given. A mobile robot has been equipped to lay and track a heat trail.

A fuzzy qualitative model of a robot sensor, presented in this paper, is for locating 3-D objects, and the location information is used to guide the movements of an industrial robot to pick up the objects. The sensor consists of a rigid platform mounted on a flexible column. Each object to be located is held rigidly with respect to the platform. The static deflections of the column and natural frequencies of vibration of the dynamic system comprising the object, platform and column are measured and processed using a mathematical model of the system to determine the location of the object. In practice, the frequency measurements have low repeatability, which leads to inconsistent location information. Also, when the orientation is in the region 80°–90° relative to a reference axis of the sensor, the mathematical model becomes ill-conditioned. In this paper, a fuzzy qualitative model of the sensor is described. The fuzzy model is designed to yield the orientation in the region where the mathematical model is unusable. Different stages for constructing the fuzzy model are described. The on-line implementation of the model is outlined and the experimental results obtained are presented.

Position localization is a necessary and important task for an intelligent robot, which moves and works in place of human workers. Various methods for position localization tasks have been proposed and developed by many researchers; for example, can active method using ultrasonic waves or laser and a passive method using images of bar codes or marks in the workspace of the robot. The passive method, using images of the object in the workspace of the robot, is particularly desirable, as this method does not influence the workspace. Thus, an arrangement of the workspace is not necessary and many robots can work simultaneously.

This paper presents an algorithm that solves the inverse kinematics problem of all six degrees of freedom manipulators, “general” or “special”. A manipulator is represented by a chain of characters that symbolizes the position of prismatic and revolute joints in the manipulator and the special geometry that may exist between its joint axes. One form of the loop closure equation is chosen and the Raghavan and Roth method is used to obtain symbolically a square matrix. The determinant of this matrix yields the characteristic polynomial of the manipulator in one of the kinematic variables. As an example of the use of this algorithm we present the solution to the inverse kinematics problem of the GMF Arc Mate welding manipulator. In spite of its geometry, this industrial manipulator has a non-trivial solution to its inverse kinematics problem.

The problem of path tracking in robotic manipulators applications is studied in this paper. The path is generated as a sequence of elementary motions. The characteristic feature of our algorithm is that it avoids singularities, because there is no need to use inverse kinematics. Direction and proximity criteria are introduced.

The application of parallel processing methods to path tracking according to the previous algorithm is presented. The algorithm is implemented in the Alliant FX/80 parallel machine.

Many robotic tasks require the end-effector to come into contact with the external environment. In such complex tasks, the manipulator is constrained by the environment, and certain DOFs are lost for motion. The contact forces must be controlled in constraint directions, while the tip position is simultaneously controlled in the free directions.

Part II continues to develop a hyper-stability framework for presenting physical interpretations of dexterous motion controls, such as hybrid position/force, impedance, model-based adaptive, learning control and coordination. In all cases passivity induced by introduction of a quasi-natural potential plays a key role. In view of these considerations, the final section discusses the possibility of development of a nonlinear circuit theory based on feedback connections of hyper-stable blocks, which may give rise to a physical understanding of dexterous and skilled motions for nonlinear mechanical systems and, eventually lead to the design of intelligent functions implementable in robotic machines.

A new method for calculating the Jacobian for a general n degree-of-freedom robot manipulator is presented and compared with some known other methods. The computational efficiency of the method is estimated in terms of the number of multiplications, additions/subtractions, trigonometric functions required, and the execution time on a VAX 11/750 computer. It is shown that the new method proposed in this paper is one of the most efficient when applied on a robot manipulator with successively parallel or rectangular joint rotations.