In the design of a compliant admittance controller for physical human-robot interaction, it is necessary to ensure stable and effective cooperation. The stability of the admittance controller is mainly threatened by a stiff environment. Many methods that guarantee stability in arbitrary environments, impose conservative control gains that limit the effectiveness of the cooperation. Inspired by previous work in frequency domain stability observers, a method is proposed in this paper to detect unstable behavior and stabilize the robot with online adaptation of the admittance control gains. The introduced instability index is based on frequency domain analysis, which very quickly detects unstable behavior by monitoring high frequency oscillation in the force signal. To treat the instability, an adaptation scheme of the admittance parameters is proposed, that relaxes conservative gains and improves the cooperation by considering the effect of variable admittance on the operators' effort. We investigate two human-robot co-manipulation tasks; cooperation within a zero stiffness environment and cooperation in contact with a stiff double-wall virtual environment. The proposed methods are validated experimentally with a number of subjects in cooperation with an LWR manipulator.

Three methods for the formulation of the kinematic equations of robots with rigid links are presented in this paper. The first and most common method in the robotics community is based on 4/spl times/4 homogeneous matrix transformation, the second one is based on Lie algebra, and the third one on screw theory expressed via dual quaternions algebra. These three methods are compared in this paper for their use in the kinematic analysis of robot arms. The basic theory and the transformation operators, upon which every method is based, are referenced. Three analytic algorithms are presented for the solution of the direct kinematic problem corresponding to each method, and the geometric significance of the transformation operators and parameters is explained. Finally, a comparative study on the computation and storage requirements for the three methods is worked out.

SUMMARY: Strawberry is a very delicate fruit that requires special treatment during harvesting. A hierarchical control scheme is proposed based on a fuzzy controller for the force regulation of the gripper and proper grasping criteria, that can detect misplaced strawberries on the gripper or uneven distribution of forces. The design of the gripper and the controller are based on conducted experiments to measure the maximum gripping force and the required detachment force under a variety of detachment techniques. It is demonstrated that the hand motion for detaching the fruit from the stem has a significant role in the process because it can reduce the required force. By analysing those results a robotic gripper with pressure profile sensors is developed that demonstrates an efficiency comparable to the human hand for strawberry grasping. The designed gripper and fuzzy controller performance is tested with a considerable number of fresh fruits to demonstrate the effectiveness to the uncertainties of strawberry grasping.

Biomicroelectromechanical systems (bio-MEMS) are MEMS which are designed for medical or biological applications. As with other MEMS, bio-MEMS frequently, have to be packaged to provide an interface to the macroscale world of the user. Bio-MEMS can be roughly divided in two groups. Bio-MEMS can be pure technical systems applied in a biological environment or technical systems which integrate biological materials as one functional component of the system. In both cases, the materials which have intimate contact to biological matter have to be biocompatible to avoid unintentional effects on the biological substances, which in case of medical implants, could harm the patient. In the case of biosensors, the use of nonbiocompatible materials could interfere with the biological subcomponents which would affect the sensor's performance. Bio-MEMS containing biological subcomponents require the use of "biocompatible" technologies for assembly and packaging; e.g., high temperatures occurring, for instance, during thermosonic wire bonding and other thermobonding processes would denature the bioaffinity layers on biosensor chips. This means that the use of selected or alternative packaging and assembly methods, or new strategies, is necessary for a wide range of bio-MEMS applications. This paper provides an overview of some of the strategies, technologies, and applications in the field of bio-MEMS packaging. It includes the following: strategies for the partitioning of subsystems within integrated microsystems for (bio)chemical analysis/synthesis; methods for microassembly of bio-MEMS; technologies for bonding of polymer bio-MEMS components; packaging of miniature medical devices; packaging of biosensors for in vitro applications; packaging of micropumps as a bio-MEMS component. The applications discussed are derived from different fields to demonstrate the plethora of bio-MEMS considerations. In commercial production, packaging is possibly the major cost factor of bio-MEMS-based products, and its development requires special attention.