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.

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).

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.

This paper presents a virtual headstick system as an alternative to the conventional passive headstick for persons with limited upper extremity function. The system is composed of a pair of kinematically dissimilar master-slave robots with the master robot being operated by the user's head. At the remote site, the end-effector of the slave robot moves as if it were at the tip of an imaginary headstick attached to the user's head. A unique feature of this system is that through force-reflection, the virtual headstick provides the user with proprioceptive information as in a conventional headstick, but with an augmentation of workspace volume and additional mechanical power. This paper describes the test-bed development, system identification, bilateral control implementation, and system performance evaluation.

The Multimodal User Supervised Interface and Intelligent Control (MUSIIC) project focuses on a multimodal human-machine interface which addresses user need to manipulate familiar objects in an unstructured environment. The control of a robot by individuals with significant physical limitations presents a challenging problem of telemanipulation. This is addressed by a unique user-interface integrating the user's command (speech) and gestures (pointing) with autonomous planning techniques (knowledge-bases and 3-D vision). The resultant test-bed offers the opportunity to study telemanipulation by individuals with physical disabilities, and can be generalized to an effective technique for other, including remote and time-delayed, telemanipulation. This paper focuses on the knowledge-driven planning mechanism that is central to the MUSIIC system.

A number of techniques, grouped under the umbrella term of usability inspection, have been devised in recent years to help software developers focus more closely on the needs of end-users during the development of interactive applications. Central to the use of such methods is the question of how proposed designs can be tested before a complete system has been implemented. This paper discusses the role of high and low-fidelity prototypes used for this purpose in software development and proposes the use of a “variable-fidelity” prototype as an aid to the development of interactive robotic systems. The approach is outlined and illustrated through the example application of an Interactive Robotic Visual Inspection System (IRVIS) developed for use by a person with limited physical manipulation skills.

A person with a moderate or severe motor disability will often use specialised or adapted tools to assist their interaction with a general environment. Such tools can assist with the movement of a person's arms so as to facilitate manipulation, can provide postural supports, or interface to computers, wheelchairs or similar assistive technologies. Designing such devices with programmable stiffness and damping may offer a better means for the person to have effective control of their surroundings.

This paper addresses the possibility of designing some assistive technologies using impedance elements that can adapt to the user and the circumstances. Two impedance elements are proposed. The first, based on magnetic particle brakes, allows control of the damping coefficient in a passive element. The second, based on detuning the P-D controller in a servo-motor mechanism, allows control of both stiffness and damping. Such a mechanical impedance can be modulated to the conditions imposed by the task in hand. The limits of linear theory are explored and possible uses of programmable impedance elements are proposed.

The current designs of commercial artificial hands have a low level of innovation. As feedback to the user is difficult to achieve reliably, most devices are simple in design and operation, and limited in functional range. If information on the state of the hand, the forces and any slippage that is occurring is fed back to a microcontroller then more than one degree of freedom can be controlled and a greater and more natural functional range is possible. This paper describes the development of such a device. It outlines the design requirements, the methods of detection of the signals and the training required to operate the hand.

This paper presents a prototype development of a robot arm to assist walking of elderly people. For effective use in Japanese houses, a robot arm mounted on a rail was designed. Force sensors were used to provide an easy-to-use interface. Thresholds of forces were determined to detect the user's intention to walk as well as for safety considerations. Applying a step by step motion, the arm could follow the rhythmical walking of the subject. We examined an interface method using force sensors and concluded that it can detect the user's motion at the beginning of a walk.

This paper presents a compliant control method for insertion of complex objects with concavities. Most work on robot assembly using compliant motion control schemes focuses on overcoming jamming conditions for simple peg-in-hole problems, and cannot be used for complex shapes frequently encountered in assembly applications. When an object is being inserted to a hole or slot with a small clearance, a contact path is issued to compensate for uncertainties. When the object shape is complex, however, the contact state changes several times and severely, making compliant control difficult. The algorithm presented here is capable of generating satisfactory compliant motion control in spite of changing contact states. During the execution of a nominal motion plan, it computes the actual position of the contact point from the force/torque sensor reading using a contact localization algorithm. It then dynamically updates the center for compliance to the computed contact point, and minimize the chance of jamming and unwanted collisions. The control scheme has been implemented on hardware and tested on the task of inserting a T-shape into a C-shape involving a very tight tolerance. The insertion motion was accomplished by a sequence of 2 translational and 1 rotational compliant motions, and successfully executed by the proposed compliant motion controller.

In this paper, we develop a force display system using parallel wire mechanism for virtual sports training with high speed motion. We firstly point out a control issue of the force display system driven by parallel wire mechanism. Based on the analysis, control laws are proposed to improve performance of the force display system. It is experimentally demonstrated that the proposed control laws realize higher acceleration and lower reaction force than other force display systems. Using the experimental result, the performance of the system is evaluated quantitatively.

The goal of this paper is to provide a critical review of the well-known resolved-acceleration technique for the tracking control problem of robot manipulators in the task space. Various control schemes are surveyed and classified according to the type of end-effector orientation error; namely, those based on Euler angles feedback, quaternion feedback, and angle/axis feedback. In addition to the assessed schemes in the literature, an alternative Euler angles feedback scheme is proposed which shows an advantage in terms of avoidance of representation singularities. An insight into the features of each scheme is given, with special concern to the stability properties of those schemes leading to nonlinear closed-loop dynamic equations. A comparison is carried out in terms of computational burden. Experiments on an industrial robot with open control architecture have been carried out, and the tracking performance of the resolved-acceleration control schemes in a case study involving the occurrence of a representation singularity is evaluated. The pros and cons of each scheme are evidenced in a final discussion focused on practical implementation issues.

A genetic algorithm for the path planning problem of a mobile robot which is moving and picking up loads on its way is presented. Assuming a findpath problem in a graph, the proposed algorithm determines a near-optimal path solution using a bit-string encoding of selected graph vertices. Several simulation results of specific task-oriented variants of the basic path planning problem using the proposed genetic algorithm are provided. The results obtained are compared with ones yielded by hill-climbing and simulated annealing techniques, showing a higher or at least equally well performance for the genetic algorithm.

This paper describes an automated procedure for analysing the significance of each of the many terms in the equations of motion for a serial-link robot manipulator. Significance analysis provides insight into the rigid-body dynamic effects that are significant locally or globally in the manipulator's state space. Deleting those terms that do not contribute significantly to the total joint torque can greatly reduce the computational burden for online control, and a Monte-Carlo style simulation is used to investigate the errors thus introduced. The procedures, freely available, are a hybrid of symbolic and numeric techniques implemented using a standard computer algebra package.