ROBOTICS AND AUTOMATION WORLDWIDE

1. Australia

Robot Etherbot. At Monash University researchers report the development of a portable mobile robot system called ‘Etherbot’. It carries no computer aboard but instead, the calculations required to determine the robot's location and the shortest obstacle-free path to a desired destination are carried on a nearby workstation. This is a Silicon Graphics workstation with which the robot communicates via a 2Mb radio Ethernet link. This reduces the payload and increases the time that the robot can travel before its batteries need recharging.

In a previous paper we presented a neural network called FRONTAL that attempted to capture the ability of infants to actively self-organize in a non-stationary environment. This paper describes the procedure whereby FRONTAL is interfaced to a robotic system called DART. DART comprises of a PUMA-562 arm and a real-time image processing system. The implementation procedure consisted of first connecting FRONTAL to a simulated DART robot. After successful operation, FRONTAL was connected to the real hardware DART. The ability of this robotic system to actively explore its surroundings and modify its behavior based on experience and environmental feedback confirms previous simulation results.

This special issue of “Robotica” gives an opportunity to present a cross-section of the wide range of research and development projects in rehabilitation robotics. Rehabilitation Robotics (RR) is the application of robotic technology to the rehabilitative needs of people with disabilities as well as the growing elderly population. The papers were originally presented at the ICORR'97 conference, organised by the Bath Institute of Medical Engineering and held in April 97 at the University of Bath. ICORR'97 was the fifth in the series of International Conferences on Rehabilitation Robotics and, after a break of three years, was a welcome and overdue time for sharing of ideas between workers in the field.

At the Forensic Science Service laboratories in Birmingham, U.K., robots are helping to build what is claimed to be the world's first digitised database of DNA samples taken from convicted criminals.

“Intelligent robotic assembly” indicates a complete degree of autonomy and a high adaptability in performing assembly tasks. For instance, a highly flexible and intelligent assembly system appears to be one that can autonomously perform any assembly work in entirely unstructured environments. This system does not require organized, orderly forms of part transport and presentation devices, such as assembly jig and fixture, part feeding devices, tray, magazine, conveyor, etc., but needs only an assembly table where parts to be assembled are stacked up in a cluttered manner.

A new global isotropy index (GII) is proposed to quantify the configuration independent isotropy of a robot's Jacobian or mass matrix. A new discrete global optimization algorithm is also proposed to optimize either the GII or some local measure without placing any conditions on the objective function. The algorithm is used to establish design guidelines and a globally optimal architecture for a planar haptic interface from both a kinematic and dynamic perspective and to choose the optimum geometry for a 6-DOF Stewart Platform. The algorithm demonstrates consistent effort reductons of up to six orders of magnitude over global searching with low sensitivity to initial conditions.

A basic problem in the development of an intelligent vehicle/highway system (IVHS), or an autonomous mobile robot system (AMRS) is to find suitable input controls which can be used to drive the vehicle between any two configurations. In this paper a trajectory generation problem for a four-wheel-steering tractor/semi-trailer system is investigated, and it is shown that this nonholonomic constraint problem can be converted into one of finding fitting-functions satisfying certain necessary boundary conditions. Proposals for control laws are presented and simulation results for a lane change manoeuvre are given.

This paper concerns the modeling and control of a mobile manipulator which consists of a robotic arm mounted upon a mobile platform. The equations of motion are derived using the Lagrange-d'Alembert formulation for the nonholonomic model of the mobile manipulator. The dynamic model which considers slip of the platform's tires is developed using the Newton-Euler method and incorporates Dugoff's tire friction model. Then, the tracking problem is investigated by using a well known nonlinear control method for the nonholonomic model. The adverse effect of the wheel slip on the tracking of commanded motion is discussed in the simulation. For the dynamic model, a variable structure control approach is employed to minimize the harmful effect of the wheel slip on the tracking performance. The simulation results demonstrate the effectiveness of the proposed control algorithm.

It is an established fact that a majority of a product's cost is determined by its design. Hence, effort should be directed to achieve a lower cost design without sacrificing the original functionality. A computer-aided product redesign system is proposed to provide help in generating assembly-oriented redesign by taking the robotic assembly constraints into consideration. The system operates in two phases: In the first phase, an objective evaluation of the input design is performed to determine whether there is a need for redesign. During the second phase, the focus is to aid the designer in searching for feasible design alternatives. Three quantitative measures have been proposed to evaluate the conformity of an input design to a list of DFA design guidelines. If the input design received a bad evaluation results on any of the three measures, a search for feasible redesign suggestions is initiated to derive suitable redesign suggestions.

In this paper, we present an experimental evaluation of several link position tracking control algorithms for rigid-link flexible-joint robot manipulators. To study the performance of the controllers, an IMI 2-link direct-drive planar robot manipulator was modified to approximate linear torsional spring couplings from the actuators to the links. Preliminary experimental results seem to indicate that reduced-order, model-based controllers with an actuator feedback loop provide relatively good link position tracking while a full-order, model-based controller offers some further improvement in link position tracking at the expense of increased computation.

Planning appropriate trajectories can significantly increase the productivity of robot systems. To plan realistic time-optimal trajectories, the robot dynamics have to be described precisely. In this paper, a neural network based algorithm for tim e-optimal trajectory planning is introduced. This method utilises neural networks for representing the inverse dynamics of the robot. As the proposed neural networks can be trained with data obtained from exciting the robot with given torque inputs, they will capture the complete dynamics of the robot system. Threfore, the trajectories generated will be mo re realistic than those obtained by using nominal dynamic equations based on nominal parameters. Time-optimal trajectories are generated for a PUMA robot to demonstrate the proposed method.

Rehabilitation Robotics (RR) is a challenging field with a high potential to support people with severe disabilities in their daily life. In the past years this field developed in Europe with a European dimension. European consortia have been supported in technical development and investigations. Also, several robotic aids have been sold and installed in Europe and support end users in their daily life. However, the breakthrough on the market is still outstanding. This paper tries to draw a picture of the RR situation in Europe and discusses aspects to move forward. Particular reference is given to TIDE (Technology Initiative for Disabled and Elderly people of European Union) and the special interest group on RR (SIG-1) of the AAATE (Association for the Advancement of Assistive Technology in Europe).

One of the most difficult challenges in mobile robotics is real-world navigation. A real world can change suddenly and this change makes the robot relinquish planning actions in advance. In order to overcome such a change, behavior-based navigation was introduced. However, it had a difficulty in planning deliberate actions and in communicating with humans.

We propose a new control strategy combining both the merits of behavior-based and planner-based approaches. The architecture consists of three major parts: Behaviors, Planner, and Coordinator. The Planner plays two important roles: 1) as a flexible human interface and 2) as the planner itself. The Coordinator serves as an interface between Behaviors and Planner and guides Behaviors to accomplish meaningful tasks according to the guidelines from the Planner and the Position estimator.

We also provide a brief description of the intelligent mobile robot CAIR-2 and for '95 IJCAI/AAAI Robot Competition and Exhibition when the robot was placed first in the Office Delivery event.

This paper contains the result of a computer simulation of the dynamic performance of a manipulator. Provision is made in the program developed to represent the manipulator in either a redundant or non-redundant form. The models derived are used in simulation studies to evaluate the dynamic behaviour of the process when subjected to different control strategies for a range of operational tasks. The dynamic manipulator model presented is derived from the laws of Newtonian and Lagrangian Mechanics.

Realisations and concepts are presented on the control of the MANUS wheelchair-mounted telemanipulator arm by severely disabled persons with few residual functions. Functional aspects are stressed as a basis for technical implementations, with special attention to the ergonomics of interactive control of the manipulator-wheelchair system in unstructured human environments. Adaptability of the control is accentuated, both with respect to abilities and impairments of the individual user and with respect to characteristics of the environment and the task to be executed. Some methods to improve adaptability are discussed, and the need for standard interfacing methods is underlined. Control configurations in actual daily use by persons with different severe disabilities are presented in some detail. A first implementation of integrated chin joystick control of MANUS manipulator and electric wheelchair, in daily use by a person with a C4/C5 spinal cord lesion, is reported as an example.

A system to control a database is used for modelling of robotic mechanisms. This brings up the modelling process of robotic mechanisms to a higher level of abstraction and reduces the problem of numerical complexity reduction of the robotic mechanism model to database updating. Structural System Analysis was used to describe the functionality of the system for modelling of robotic mechanisms. The database model is presented by Extended Model Object-Connections, and all the object types for representation of mathematical expressions in the form of calculating graph are described in detail. The complete system is implemented and tested on the example of a robotic mechanism with six degrees of freedom and on the example of anthropomorphic locomotion robotic mechanism.

The design of tolerances should take the functionality, manufacturability, assemblability and cost effectiveness of a product into consideration. This paper presents a method of analyzing and evaluating the assemblability of a product under given tolerance specifications in order to provide a tool to aide for tolerance design. Introduced is the range of feasible displacement of a part of an assembly as a result of the accumulation of clearances between mating parts along the serial as well as parallel chain of assembly, which can play a role of compensating for the pose error of the corresponding part due to the accumulation of tolerances. Assemblability is determined by the probability that all the parallel as well as serial chains of the assembly can be f ormed successfully under given statistical properties of tolerances. This requires to numerically compute the probability that a pair of mating parts forming a parallel chain can align themselves within the error margin defined by their mating clearance, accounting for the possible compensation of the ranges of pose errors associated with the mating parts due to tolerance accumulations by the ranges of feasible displacements of the mating parts due to clearance accumulations. Simulation results are shown.

One of the most fundamental problems in the development of an intelligent highway system or an autonomous mobile robot system for factory use is to find the necessary input control variables for smooth and safe movement of the vehicle, or robot, between any two configurations. In this paper it is demonstrated that this problem can be converted into one of finding a fitting function which satisfies the boundary conditions. Three curves, a quintic polynomial, a cubic polynomial and a triangular function are developed to perform the parallel transfer manoeuvre which forms the basis of several important manoeuvres such as reverse parking, moving off, negotiating a stationary obstacle, overtaking a moving vehicle, and changing lane. A detailed discussion of the effect of the vehicle's steering angle limit on the feasibility of these manoeuvres is presented. Simulation results using three typical vehicles, a long commercial vehicle, an ordinary car, and a small laboratory robot, travelling along three curves are also presented and discussed. Based on the comparative study, some suggestions for further work are made. Compared with other methods, this approach is simple and provides excellent simulation of human driver techniques. The paper concludes with a focused discussion about the integration of these techniques with satellite based GPS systems for automated vehicle guidance on highways.

The paper addresses the robust adaptive control problem of robot manipulators. The dynamic equations of robot manipulators and their fundamental properties that facilitate analysis and control system design are first reviewed. Then the direct, indirect, and combined direct and indirect adaptive control approaches of robot manipulators are presented. After that, a number of variable structure adaptive control approaches which combines features of the robust design based on variable structure systems with parameter adaptive control, are studied. After that, a new combined adaptive and variable structure adaptive control approach is proposed for the tracking control of robot manipulators under the uncertainty environment. This is a robust, high-performance adaptive control scheme that combines the advantages and overcomes the disadvantages of both types of techniques. Finally, the extensive comparing simulation results are presented to demonstrate the theory study.

A general method for the computation of the canonical form of three-systems of infinitesimal screws is presented. The method is particularly simple when the three-system has a basis that is simultaneously perpendicular and reciprocal. However, it can also handle the special or degenerate cases. The method and the concurrent results are important from the theoretical point of view because of the obvious connection with the classification of screw-systems. Moreover, the results are also important for applied kinematics after recent applications of the canonical form of screw-systems to the analysis and synthesis of manipulators and manipulator substructures.