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.

It is expected that an appropriate robotic appliance can play a major role in providing long periods of independence, which in turn will lead to improved quality of life, for people who are severely physically limited. As part of its research programme over the past several years the Neil Squire Foundation has been developing a workstation-based robotic assistive appliance (RAA) for use by such persons. We feel that robotic aids initially will have their most profound impact when applied in a vocational environment. Although other rehabilitation researchers have similar interests there is a great need for the utility of robots in these environments to be more fully substantiated and assessed. A formal evaluation process currently is under way in an attempt to quantify and to understand the cost/benefit results of using the RAA in office situations.

This paper deals with the study of the effects of Harmonic Drives characteristics on the dynamic behaviour of industrial robots. These components are firstly analyzed on the basis of the technical literature and, as a result, a mechanical model with concentrated parameters is obtained. Finally, the influence of these parameters on the dynamic behaviour of an actual SCARA robot in our department is investigated by means of experimental tests and by a computer simulation program purposely written.

The consideration of part motion instability is crucial to the determination of assembly sequence since this affects the complexity of fixtures and dexterity of robots. This paper presents a new approach to the inference of robotic assembly sequences, taking into consideration the instability of base assembly motions. Based upon the evaluation of motion instability, the method generates stable assembly sequences by use of the precedence constraint inference method previously developed by the authors. An example assembly of a 10-part electrical relay is given to illustrate the concepts and procedure of the proposed scheme. The results show that the proposed method can be effectively utilized to generate stable assembly sequences, thus providing crucial information on the fixture design and selection of types of assembly robots.

This paper addresses widely applicable methods for solving the kinematics problem of any class of serial-link robot manipulators. First, the position and orientation of the manipulator hand, the Jacobian matrix and their symbolic generation are clearly presented using recursive relations. Second, the inverse problem to such formulations is posed as an unconstrained non-linear optimization one, where numerical techniques for the overdetermined and underdetermined kinematic problems are considered separately to derive consistent arm solutions. On the basis of several proposals on step lengths involved to maintain good numerical stability, the results of computer simulation show that performance is sufficiently reliable.

The application of heavy robots is usually restricted to those problems where large loads are carried and high speed is not required. This paper proposes a method for the improvement of robot dynamic capabilities thus enabling a heavy robot to perform the fast manipulation. The approach follows the idea of “distributed positioning” and introduces redundancy. The concept adopted is proved on two different configurations: an elbow-scheme manipulation robot and a gantry welding robot.

A global optimal control algorithm was developed with the aim of finding a control which satisfies some special requirements in the sense of obtaining singular position free movement of the redundant robot mechanism. The solution of the developed global optimal control algorithm is a boundary value problem. The additional constraints in the boundary value problem were constructed with the use of an optimization process. The usefulness of the developed global optimal control algorithm is demonstrated by the example of the 3 DOFs planar redundant robot mechanism of SCARA type.