Human task performance using teleoperator systems depends on the physical and controlled parameters of the system. Two teleoperated grasping tasks-size and stiffness discrimination-were studied to investigate how changes in system parameters influence human capabilities. The device characteristics altered were teleoperator stiffness (size and stiffness discrimination) and teleoperator damping (size discrimination only). It was found that neither teleoperator stiffness nor teleoperator damping influenced size discrimination. Also, teleoperator stiffness did not influence stiffness discrimination. Furthermore, teleoperated performance was compared with direct interaction using bare hands or with the fingers in a bracket. Size discrimination performance was equivalent for these three conditions, but stiffness discrimination performance was lower for teleoperation than for direct interaction.

The quality of a teleoperation system depends on a combination of device characteristics and human perception. This paper presents a study on the relationship between human size discrimination capabilities and teleoperator stiffness for a finger grip grasp task. The teleoperator stiffness was varied in a wide range, and for each setting the human size discrimination capabilities was measured. The teleoperator grasp performance was also compared with two reference conditions: bare hands and fingers in brackets. It was found that the teleoperator stiffness has no measurable influence on operator performance. It was also found that humans surprisingly perform equally well using the teleoperator as with bare hands

This paper introduces a novel type of actuator that is investigated by ESA for force-reflection to a wearable exoskeleton. The actuator consists of a DC motor that is relocated from the joint by means of Bowden cable transmissions. The actuator shall support the development of truly ergonomic and compact wearable man-machine interfaces. Important Bowden cable transmission characteristics are discussed, which dictate a specific hardware design for such an actuator. A first prototype is shown, which was used to analyze these basic characteristics of the transmissions and to proof the overall actuation concept. A second, improved prototype is introduced, which is currently used to investigate the achievable performance as a master actuator in a master-slave control with force-feedback. Initial experimental results are presented, which show good actuator performance in a 4 channel control scheme with a slave joint. The actuator features low movement resistance in free motion and can reflect high torques during hard contact situations. High contact stability can be achieved. The actuator seems therefore well suited to be implemented into the ESA exoskeleton for space-robotic telemanipulation.

Stability control for walking bipeds has been considered a complex task. Even two-dimensional fore-aft stability in dynamic walking appears to be difficult to achieve. In this paper we prove the contrary, starting from the basic belief that in nature stability control must be the sum of a number of very simple rules. We study the global stability of the simplest walking model by determining the basin of attraction of the Poincare/spl acute/ map of this model. This shows that the walker, although stable, can only handle very small disturbances. It mostly falls, either forward or backward. We show that it is impossible for any form of swing leg control to solve backward falling. For the problem of forward falling, we devise a simple but very effective rule for swing leg action: "You will never fall forward if you put your swing leg fast enough in front of your stance leg. In order to prevent falling backward the next step, the swing leg shouldn't be too far in front." The effectiveness of this rule is demonstrated with our prototype "Mike.".

Describes the development of an efficient mechanical oscillator. It is capable of combining the energetic advantages of ballistic movement with cycle adjustability and active orbital control. Pneumatic artificial McKibben muscles are used as variable springs, from which the stiffness is varied in order to induce a limit cycle.

Previous research has shown that passive (or ballistic) walking is an energetic efficient and mechanical cheap way of walking. Therefore, ballistic walking would be suitable for applications in rehabilitation technology and autonomous robots. Successful application would require a smooth hip trajectory in order to protect respectively the patient or electronics against large velocity changes due to ground collisions. It is shown that an actively adjustable stance leg compliance in combination with a viscous damping can result in smaller hip velocity changes.