Diode-Grid Oscillators

Loading a two-dimensional grid with active devices offers a means of combining the power of solid-state devices in the microwave and millimeter-wave range. The grid structure allows a large number of negative resistance devices to be combined. This approach is attractive because the active devices do not need an external locking signal, and the combining is done in free space. The loaded grid is a simple planar structure suitable for monolithic integration. Preliminary measurements on a nine-diode grid at 10 GHz show power-combining and frequency-locking without an external locking signal

The instrumented shoe insole for rule-based control of gait in persons with hemiplegia

We describe the use of an insole with five pressure sensors having small hysteresis, an inertial measurement unit, and the circuitry for wireless synchronized communication for the rule-based control of gait. The system was tested with the multichannel electronic stimulator MOTIMOVE that can receive signals from analog and digital sensors to activate up to eight muscle groups. The rule-based control implements the heuristically determined mapping of the four joint states (blocked -B, flexion - F, extension - E, loose - L) and Gait Teacher based representation of the events and phases of the gait cycle. The four joint states can be achieved by the activation of flexors (F), extensors (E), coactivation of flexors and extensors (B), and no action (L). The feasibility of the operation was tested only in a small number of persons with hemiplegia since the stimulator certification procedure required for the full clinical study is in progres

Simulation of a Texas Hold'Em poker player

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FES of Upper Extremities: Post-conference course

The workshop is structured to have a theoretical introduction and subsequent application oriented hands-on demonstrations. The workshop is planned to include continuous interactive discussion. The workshop will focus on non-invasive options for the control of paralyzed arm-hand complex after the central nervous system lesion (brain lesion, cervical lesion of the spinal cord, and similar). The workshop starts with theory describing the principle of the operation of functional activation of paralyzed muscles by means of electrical field and differences between the use of transcutaneous and implantable technologies. The results on the efficacy of FES augmented manipulation and grasping, with the emphasis on what were the limitations of the systems applied, will follow. The main questions that will be answered deal with methods to provide sufficient selectivity, minimize muscle fatigue, and have the control that matches the needs of users. The practical part will be a demonstration of the strategies and limitations of the surface activation of arm muscles to support the exercise, manipulation and exercise. The presentation will include the activation of sensory pathways for possible feedback applications. An interesting example will be described where the FES technology can be used for the reduction of tremor. The practical part will be with the new stimulators MOTIMOVE (https://www.3-x-f.com/products.php) and UNAFET stimulators used in clinical trials for therapy persons after stroke and spinal cord lesion at the cervical level

A 100-MESFET planar grid oscillator

A 100-MESFET oscillator which gives 21 W of CW effective radiated power (ERP) with a 16-dB directivity and a 20% DC-to-RF conversion efficiency at 5 GHz is presented. The oscillator is a planar grid structure periodically loaded with transistors. The grid radiates and the devices combine quasi-optically and lock to each other. The oscillator can also be quasi-optically injection-locked to an external signal. The planar grid structure is very simple. All of the devices share the same bias, and they can be power and frequency tuned with a mirror behind the grid or dielectric slabs in front of it. An equivalent circuit for an infinite grid predicts the mirror frequency tuning. The planar property of the oscillator offers the possibility of a wafer-scale monolithically integrated source. Thousands of active solid-state devices can potentially be integrated in a high-power source for microwave or millimeter-wave applications

Wireless powering for low-power distributed sensors

In this paper, an overview of the field of wireless powering is presented with an emphasis on low-power applications. Several rectenna elements and arrays are discussed in more detail: (1) a 10-GHz array for powering sensors in aircraft wings; (2) a single antenna in the 2.4-GHz ISM band for low-power assisted-living sensors; and (3) a broadband array for power harvesting in the 2-18GHz frequency range

Learning Arm/Hand Coordination with an Altered Visual Input

The focus of this study was to test a novel tool for the analysis of motor coordination with an altered visual input. The altered visual input was created using special glasses that presented the view as recorded by a video camera placed at various positions around the subject. The camera was positioned at a frontal (F), lateral (L), or top (T) position with respect to the subject. We studied the differences between the arm-end (wrist) trajectories while grasping an object between altered vision (F, L, and T conditions) and normal vision (N) in ten subjects. The outcome measures from the analysis were the trajectory errors, the movement parameters, and the time of execution. We found substantial trajectory errors and an increased execution time at the baseline of the study. We also found that trajectory errors decreased in all conditions after three days of practice with the altered vision in the F condition only for 20 minutes per day, suggesting that recalibration of the visual systems occurred relatively quickly. These results indicate that this recalibration occurs via movement training in an altered condition. The results also suggest that recalibration is more difficult to achieve for altered vision in the F and L conditions compared to the T condition. This study has direct implications on the design of new rehabilitation systems

The assessment of spasticity: Pendulum test based smart phone movie of passive markers

The pendulum test is the method for quantification of the level of spasticity in persons with spinal cord and brain injuries/diseases. The data for the assessment comes from the analysis of lower leg rotation in the sagittal plane while sitting caused by gravity. We built a simple instrument that uses the smart phone and passive markers for studying the pendulum movement of the leg. We compared the results of the new device with the results acquired with the conventional apparatus which uses a knee joint angle encoder and inertial sensors mounted on the upper and lower leg. The differences of parameters estimated from the test between the two systems are in the range of 5%, which is in the same range as the precision of the positioning of the pendulum apparatus on the leg. The new system is simple for the application (donning, doffing, setup time, accuracy, repeatability) and allows a straightforward interpretation to a clinician. © Serbian Journal of Electrical Engineering. 2018