The work presented here is the description of the control strategy of two cooperating robots. A two–finger hand is an example of such a System. The control method allows for position control of the contact point by one of the robots while the other robot controls the contact force. The stability analysis of two robot manipulators has been investigated using unstructured models for dynamic behavior of robot manipulators. For the stability of two robots, there must be some initial compliance in either robot. The initial compliance in the robots can be obtained by a non-zero sensitivity function for the tracking controller or a passive compliant element such as an RCC.

This paper is concerned with the design of intelligent subsystems that interface actuators and sensors to intelligent supervisors for robot work-cells. Benefits of our approach include removal of low level computation and stringent real-time constraints from the superviser, potential for combining and interpreting information from sensor combinations, and provision of a uniform information interface for disparate devices. Our approach to the design and organisation of these subsystems is based on the concept of virtual devices. We demonstrate the applicability of the concept by describing the design and implementation of an intelligent controller for a sensory gripper.

An approach for collision–free trajectory planning along designated paths of two robots in a common workspace is presented. Specifically, in order to describe potential collision between the links of two robots along the designated paths, explicit forms of virtual obstacle are adopted, according to which links of one robot are made to grow while the other robot is forced to shrink as a point on the path. Then, a notion of virtual coordination space is introduced to visualize all the collision–free coordinations of two trajectories. Assuming that a collision–free coordination curve between the two robots is given via a virtual coordination space, the minimum time collision–free trajectory pair for the two robots is sought considering dynamic constraints of torque and velocity bounds of actuators of the two robots.

In this paper, a new splines–based control method for robot manipulators is presented and discussed. The above method can be effectively used for path planning and control of rigid and flexible robots. The computational simplicity of the proposed algorithm, together with its flexibility and its high–level intelligence built in, can be considered as promising tools for achieving the goals of modem robot manipulator design.

The use of ultrasonic range transducers is an inexpensive method of obtaining information about the environment surrounding a robotic System. However, ultrasonic ranging suffers from various shortcomings, one of the major being the production of unreliable data caused by specular reflection.

This work presents an original approach to overcoming the problem of unreliable ultrasonic range data which is caused by specular reflection of the ultrasonic beam. The approach is shown to discriminate between reliable and unreliable data, thus enhancing the role of the ultrasonic range transducer in robotic applications.

A novel approach to control synthesis of biped locomotion mechanisms is suggested. The synthesis is carried out in two stages: the stage of nominal regimes (the synthesized control has to ensure the realization of gait in the absence of any disturbance), and the stage of perturbed regimes (the control has to eliminate deviations from the nominals under an additional condition of preserving the stability of the overall System). At the level of perturbed regimes, the proposed control synthesis should ensure the compensating movements such to bring the System ot its nominal during the gait. However, the compensating movements can, as a side–effect, induce the undesirable inertial forces which can influence the mechanism overall stability. To avoid this, it is suggested such a control which ensures that the acceleration of compensating movements does not exceed a value given in advance. In addition, the case is considered when an additional correction of the zero moment point ZMP position is accomplished by different mechanism joints.

Solving the direct kinematic problem in a symbolic form requires a laborious process of successive multiplications of the link homogeneous transformation matrices and involves a series of algebraic and trigonometric simplifications. The manual production of such solutions is tedious and error-prone. Due to the efficiency of the Prolog language in symbolic processing, a rule–based Prolog program is developed to automate the creation of the following processes: Link transformation matrices; forward kinematic solutions; and the Jacobian matrix. This paper presents the backward recursive formulation techniques, the trigonometric identity rules, and some heuristic rules for implementing the System. A verification of the System has been demonstrated in case of several industrial robots.

The author introduced the use of time–varying inertia links to increase the flexibility (or versatility) of manipulators in the sense that they can so achieve more tracking capabilities. Clearly, we then have a pair of control vectors (link inertias and external forces) instead of one control vector only (applied forces). After a careful derivation of the dynamical equations of such manipulators, one shows that their control procedure can be decomposed into two stages, each of them involving sliding control schemes via prescribed dynamics on the error term, that is to say the difference between the desired position and the actual position. This approach provides a good technique to take account of possible constraints on the magnitude of the control, and in addition, it is possible to consider the sliding conditions as an ideal mechanical constraint, therefore the use of the principle of virtual displacements.

This paper is a continuation of the one entitled “Trajector control of manipulators with time–varying inertia links” (Robotica 6, No. 3, 197–202, 1988). It described new techniques to circumvent difficulties arising when the values of the mechanical parameters are not exactly known and when linearization does not apply because of the important deviation. In addition this paper shows that Appel's principle of virtual displacements is more efficient than the Lagrangian parameters for the derivation of the manipulator's dynamic parameters in the presence of mechanical constraints.