A teleoperator is a pair of robot manipulators connected in such a way as to allow an operator handling one manipulator (the master) to operate on a remote environment (via the slave). Feedback from slave to master increases the realism with which the operator interacts with the environment. Two-port models have been extensively used for the analysis of circuits in which bidirectional energy flows are present at two distinct pairs of terminals. This paper applies the hybrid two-port model to teleoperators with force and velocity sensing at the master and slave. The interfaces between human operator and master, and between environment and slave, are ports through which the teleoperator is designed to exchange energy between the operator and environment. By computing or measuring input-output properties of this two-port network, the hybrid two-port model of an actual or simulated teleoperator system can be obtained. It is shown that the hybrid model (as opposed to other two-port forms) leads to an intuitive representation of ideal teleoperator performance and applies to several teleoperator architectures. Thus measured values of the h matrix or values computed from a simulation can be used to compare performance with the ideal. The frequency-dependent h matrix is computed from a detailed SPICE model of an actual system, and the method is applied to a proposed new architecture.

A haptic interface is a kinesthetic link between a human operator and a virtual environment. This paper addresses fundamental stability and performance issues associated with haptic interaction. It generalizes and extends the concept of a virtual coupling network, an artificial link between the haptic display and a virtual world, to include both the impedance and admittance models of haptic interaction. A benchmark example exposes an important duality between these two cases. Linear circuit theory is used to develop necessary and sufficient conditions for the stability of a haptic simulation, assuming the human operator and virtual environment are passive. These equations lead to an explicit design procedure for virtual coupling networks which give maximum performance while guaranteeing stability. By decoupling the haptic display control problem from the design of virtual environments, the use of a virtual coupling network frees the developer of haptic-enabled virtual reality models from issues of mechanical stability.

A patent pending, energy based, method is presented for controlling a haptic interface system to ensure stable contact undes a wide variety of operating conditions. System stabili9 is analyzed in terms of the time -domain definition of passivity We define a "Passivity Observer" (PO) wliich nzeasures enevgy flow in and out of one or more subsystems in real-time software. Active behavior is indicated bjj a negative value ofthe PO at any time.We also define the "Passivity Controller" (PC), an adaptive dissipative element which, at each time sample, absorbs exactly the net energy output (ifany) measured by the PO. The method is tested with simulation and implementation in the "Ekcalibur " haptic interface system. Totally stable operation was achieved under conditions such us stifJizess > 100 N/mm or time delays of 15ms. The PO/PC method requires very little additional computation and does not require a dynamical model to be identified.

Purpose: Automated delineation of structures and organs is a key step in medical imaging. However, due to the large number and diversity of structures and the large variety of segmentation algorithms, a consensus is lacking as to which automated segmentation method works best for certain applications. Segmentation challenges are a good approach for unbiased evaluation and comparison of segmentation algorithms. Methods: In this work, we describe and present the results of the Head and Neck Auto-Segmentation Challenge 2015, a satellite event at the Medical Image Computing and Computer Assisted Interventions (MICCAI) 2015 conference. Six teams participated in a challenge to segment nine structures in the head and neck region of CT images: brainstem, mandible, chiasm, bilateral optic nerves, bilateral parotid glands, and bilateral submandibular glands. Results: This paper presents the quantitative results of this challenge using multiple established error metrics and a well-defined ranking system. The strengths and weaknesses of the different auto-segmentation approaches are analyzed and discussed. Conclusions: The Head and Neck Auto-Segmentation Challenge 2015 was a good opportunity to assess the current state-of-the-art in segmentation of organs at risk for radiotherapy treatment. Participating teams had the possibility to compare their approaches to other methods under unbiased and standardized circumstances. The results demonstrate a clear tendency toward more general purpose and fewer structure-specific segmentation algorithms.

We developed a pneumatically powered orthosis for the human ankle joint. The orthosis consisted of a carbon fiber shell, hinge joint, and two artificial pneumatic muscles. One artificial pneumatic muscle provided plantar flexion torque and the second one provided dorsiflexion torque. Computer software adjusted air pressure in each artificial muscle independently so that artificial muscle force was proportional to rectified low-pass-filtered electromyography (EMG) amplitude (i.e., proportional myoelectric control). Tibialis anterior EMG activated the artificial dorsiflexor and soleus EMG activated the artificial plantar flexor. We collected joint kinematic and artificial muscle force data as one healthy participant walked on a treadmill with the orthosis. Peak plantar flexor torque provided by the orthosis was 70 Nm, and peak dorsiflexor torque provided by the orthosis was 38 Nm. The orthosis could be useful for basic science studies on human locomotion or possibly for gait rehabilitation after neurological injury.