Virtual impedance adjustment in unconstrained motion for an exoskeletal robot assisting the lower limb

The objective of this paper is to establish the criteria for adjusting the virtual impedance of an exoskeletal robot for the lower limb in order to minimize the operator's physical stress in unconstrained motion. The exoskeletal robot HAL (Hybrid Assistive Limb)-3 which we developed for assisting the motor function of the lower limb was used for experiments in this research. To accomplish the objective (i) the physical parameters around the joint of HAL-3 were identified and (ii) the relationships between the virtual impedance values and the physical stress of operators were examined through experiments for swinging motions of the lower leg. The physical stress was evaluated with myoelectricity, the musculoskeletal moment of the operator and the operator's feelings during the experimental motion. As a result, we found that the physical stress tended to decline with the decrease of virtual inertia and virtual Coulomb friction, and to increase slightly with the decrease of virtual gravitational moment. The decrease of virtual viscous friction made the physical stress increase gradually after it declined to a trough during the positive virtual viscous friction. Based on the results, we could establish the criteria for adjusting the virtual impedance for minimizing the operator's physical stress in unconstrained motion.     

Active compliant motion: a survey

Whether they are asked to polish or assemble parts, clean the house or open doors, the future generation of robots will have to cope with contact tasks under uncertainty in a stable and safe manner. Obtaining a controlled contact motion under uncertainty is still a major challenge for the robotics community. At present most research groups focus on one of the subcomponents (i.e., modeling, planning, estimation or control) of the system, and no overall system is developed yet. This paper presents a literature survey of the state-of-the-art of the subcomponents and points to the need for effective integration of those components.     

Control System Design for an Upper-Limb Rehabilitation Robot

Control system implementation is one of the major difficulties in rehabilitation robot design. The purpose of our study is to present newly developed control strategies for an upper-limb rehabilitation robot. The Barrett WAM Arm manipulator is used as the main hardware platform for the functional recovery training of the past-stroke patient. Passive and active recovery training have been implemented on the WAM Arm. A fuzzy-based PD position control strategy is proposed for the passive recovery exercise to control the WAM Arm stably and smoothly to stretch the impaired limb to move along predefined trajectories. An adaptive impedance force controller is employed in the active motion mode in which a fuzzy logic regulator is used to adjust the desired impedance between the robot and impaired limb to generate adaptive force in agreement with the change of the impaired limb's muscle strength. In order to evaluate the change of the impaired limb's muscle power, the impaired limb's mechanical impedance parameters as an objective evaluation index is estimated online by using a recursive least-squares algorithm with an adaptive forgetting factor. Experimental results demonstrate the effectiveness and potential of the proposed control strategies.     

Mobile robot with a self-positioning system

This paper describes a general method using configuration space for planning a collision-free path of a manipulator with 6 degrees of freedom (DOF). The basic approach taken in this method is to restrict the free space concerning path planning and to avoid executing unnecessary collision detections, based on the idea that a collision-free path can be planned using only partial information of the configuration space. The configuration space is equally quantized into cells, and the cells concerning path planning are efficiently enumerated based on a heuristic graph search algorithm. A heuristic function which characterizes the search strategy can be defined to give priority to the gross motion using the first few joints. A bi-directional search strategy is also introduced to improve efficiency. The memory is allocated only to the portion of the configuration space concerning path planning, and the data of the free space defined in the 6-dimensional configuration space can be efficiently stored. This algorithm of free space enumeration is independent of the kinematic characteristics of the manipulator. Therefore, this method is generally applicable to any type of manipulator. It has actually been implemented and has been applied to a 6-DOF articulated manipulator.     

An Experimental Study on Cartesian Impedance Control for a Joint Torque-Based Manipulator

The purpose of this paper is to present our results on experimental investigations on Cartesian impedance control and nonlinearity compensation for our harmonic drive robot based on joint torque sensors. The imperfection of the cubic model for harmonic drive friction is detected according to friction identification experiments. In addition, five different Cartesian impedance control schemes are considered and four of them are tested by corresponding experiments with/without friction compensation. Experimental results tell us that the force-based impedance control strategy is more suitable than the position-based strategy for the harmonic drive robot based on joint torque feedback.     

Rule Discovery in Telecommunication Alarm Data

Fault management is an important but difficultarea of telecommunication network management: networksproduce large amounts of alarm information which must beanalyzed and interpreted before faults can be located. So called alarm correlation is acentral technique in fault identification. While the useof alarm correlation systems is quite popular andmethods for expressing the correlations are maturing, acquiring all the knowledge necessary forconstructing an alarm correlation system for a networkand its elements is difficult. We describe a novelpartial solution to the task of knowledge acquisition for correlation systems. We present a methodand a tool for the discovery of recurrent patterns ofalarms in databases; these patterns, episode rules, canbe used in the construction of real-time alarm correlation systems. We also present tools withwhich network management experts can browse the largeamounts of rules produced. The construction ofcorrelation systems becomes easier with these tools, as the episode rules provide a wealth ofstatistical information about recurrent phenomena in thealarm stream. This methodology has been implemented ina research system called TASA, which is used by several telecommunication operators. We briefly discussexperiences in the use of TASA.     

Implementation of Network Intrusion Detection System Based on Density-based Outliers Mining

1 Introduction There are m any kinds of network intrusion detec- tion techniques,but which can be divided into two cata- logs generally: one is rule-based, and the other is anom aly-based. The form er is one which detects intru- sion behaviors according t…     

Adaptive control of free-floating space robots in Cartesian coordinates

An adaptive control scheme is proposed for the end-effector trajectory tracking control of free-floating space robots. In order to cope with the nonlinear parameterization problem of the dynamic model of the free-floating space robot system, the system is modeled as an extended robot which is composed of a pseudo-arm representing the base motions and a real robot arm. An on-line estimation of the unknown parameters along with a computed-torque controller is used to track the desired trajectory. The proposed control scheme does not require measurement of the accelerations of the base and the real robot arm. A two-link planar space robot system is simulated to illustrate the validity and effectiveness of the proposed control scheme.     

Assay on FAQ''s on Total Lab Automation

The purpose of the introduction of an automated laboratory system in one format or another is reducing the costs of the laboratory by cutting staff. Also speeding up the performance often is a goal. At the same time it is planned to increase the quality of the work done by using automated labelling and reading of documents. The use of vacuum tubes and the handling of these by the apparatus are raising the safety of the labwork.

In this paper many aspects of the daily routines when using a TLA system are discussed. The aspects are collected during the discussions before and after the implementation of the Roche CLAS system in our laboratory. Some consequences were foreseen, and others came unexpectedly. But still the subjects form a point of discussion around the TLA systems. The most important message to be picked up is that one really has to consider all possible problems that could arise from the implementation of TLA.