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Mechanical Engineering. 2014;136(09):S3-S5. doi:10.1115/9.2014-Sep-4.
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This article explains how robots can help people recover after neurological injury. The most successful robot-administered therapy to aid neuro-recovery is based on several principles of learning. A visual display indicates a target location to which the patient should attempt to move. The robot sets up a virtual channel between the current location of the patient’s limb and the target location. If the patient moves along that channel, no forces are experienced. However, if the patient’s motion deviates to either side of that channel, those aiming errors are permitted but resisted by a programmable damped spring. If the patient moves too slowly (or does not initiate movement at all), the back wall of the channel (the end at the patient’s starting location) moves smoothly towards the target location, nudging the patient to the target. Repeating this process with high intensity provides the stimulus and statistics for the brain to reacquire movement control and coordination. Passively moving a patient’s limbs may help improve joint mobility.

Commentary by Dr. Valentin Fuster
Mechanical Engineering. 2014;136(09):S6-S11. doi:10.1115/9.2014-Sep-5.
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This article discusses development of upper extremity exoskeleton devices for robot-aided rehabilitation. Neurological injuries, including stroke and spinal cord injury, typically result in significant motor impairments. These impairments negatively impact an individual’s movement coordination, in turn affecting their ability to function independently. Exoskeleton type devices are now being developed to isolate the motion of individual joints. These devices tend to have higher complexity and reduced range of motion as compared to endpoint manipulators, but they target more selectively the desired joint(s), and they enable more precise data collection about the motion of the patient's limb. Recent designs have focused on systems that match the full range of motion of the targeted joints, aiming towards actuated systems that have both high torque output, to assist patients with muscle tone, and low intrinsic impedance, to minimally perturb independent arm movements. Satisfying all of these requirements while simultaneously maintaining a high priority on patient safety is still an active area of research.

Commentary by Dr. Valentin Fuster
Mechanical Engineering. 2014;136(09):S12-S17. doi:10.1115/9.2014-Sep-6.
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This article presents and compares two different control systems for a powered knee and ankle prosthesis for transfemoral amputees, which were constructed to provide the user a safe, intuitive, and well-coordinated interaction with the prosthesis. The piecewise-passive impedance (PPI) controller utilizes only impedance-like behaviors, while the second – a hybrid impedance-admittance (HIA) controller – utilizes both impedance-like and admittance-like behaviors in a hybrid approach. The HIA approach maintains many of the desirable characteristics of the PPI controller while also reducing the number of selectable control parameters. The HIA approach essentially incorporates the PPI control structure during the early and middle stance phases of gait, and a trajectory tracking control approach in terminal stance and swing. These controllers were implemented on a powered knee and ankle prosthesis and tested in walking trials by a transfemoral amputee. Data from these trials indicate that both controllers achieve comparable performance with respect to healthy subject data, despite some substantial structural differences between the two.

Commentary by Dr. Valentin Fuster
Mechanical Engineering. 2014;136(09):S18-S21. doi:10.1115/1.2014-Sep-7.
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This article describes the design of Austin exoskeleton – a minimally actuated medical exoskeleton with mechanical swing-phase gait generation and sit-stand assistance. The Austin exoskeleton is an accessible lightweight system that enables individuals with paraplegia to walk. The gait generation hardware of the Austin exoskeleton suit consists of three major components: hip actuation, a hip-knee coupler, and a controllable locking knee. Users operate the exoskeleton with a simple wireless user interface consisting of two push buttons that are installed on the handle of the stability aid. Electrical components are located on the back of the exoskeleton. A single actuator per leg and a mechanical hip-knee coupler power the knee during swing phase and provide assistance for sitting and standing. The suit’s design embeds gait generation into hardware, decreasing controller complexity. By using a bio-inspired coupling mechanism, the Austin system is able to power both the hip and knee joints using a single hip actuator.

Commentary by Dr. Valentin Fuster
Mechanical Engineering. 2014;136(09):30-35. doi:10.1115/1.2014-Sep-1.
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This article discusses the recent development in “cognitive computing” technology. Unlike expert systems of the past, which required inflexible hard-coded expert rules, cognitive computers interpret unstructured data (sensory information, images, voices, and numbers), navigate through vast amounts of information, learn by experience, and participate in dialogues with humans using natural language to solve extremely complex problems. The U.S. Defense Advanced Research Projects Agency is funding a program called SyNAPSE (Systems of Neuromorphic Adaptive Plastic Scalable Electronics) to develop machine technology that will function like biological neural systems. IBM, Hughes Research Labs, and several universities are working on this program. The aim is to build an electronic system that matches a mammalian brain in function, size, and power consumption. It would recreate 10 billion neurons and 100 trillion synapses, consume one kilowatt (same as a small electric heater), and measure less than 2,000 cubic centimeters. Several other projects are also under way to apply cognitive technology to robotics, cars, and production systems.

Commentary by Dr. Valentin Fuster
Mechanical Engineering. 2014;136(09):36-41. doi:10.1115/9.2014-Sep-2.
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This article elaborates the concept of programming a robot by showing it how to do the job. This is often called “learning from demonstrations” or “imitation learning.” Labs at several institutions – for example, the Swiss Federal Institute of Technology at Lausanne, the University of Maryland, Massachusetts Institute of Technology, and Worcester Polytechnic Institute – are experimenting with technology that may one day make imitation learning common for machines. The underlying idea of this approach is to allow an agent to acquire the necessary details of how to perform a task by observing another agent (who already has the relevant expertise) perform the same task. Usually, the learning agent is a robot and the teaching agent is a human. Often, the goal of imitation learning approaches is to extract some high-level details about how to perform the task from recorded demonstrations. Research into imitation learning has achieved some impressive results ranging from training unmanned helicopters to perform complex maneuvers to teaching robots general-purpose manipulation tasks.

Topics: Robots
Commentary by Dr. Valentin Fuster
Mechanical Engineering. 2014;136(09):42-45. doi:10.1115/9.2014-Sep-3.
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This article explains how electrostatic discharge from oil can destroy sensitive and crucial engine components. All thermomechanical power systems contain a dielectric fluid – namely the circulating lubricant oil – where its circulation can create friction and cause a static electric charge to build up. The charge can induce voltage spikes in portions of the circulation manifold during the initial warm-up period. The spike can destroy a sensitive component such as a sensor or microprocessor, and if that component is critical to operation, the engine will shut down. Flow electrification of liquids has been a source of numerous industrial hazards, primarily in the petroleum and power industries. This effect occurs in improperly grounded systems carrying fuels, lubricating oils, and other hydrocarbon liquids. That’s why some commercial gasoline fuel hoses in the United States have an attached ground wire to dissipate electric charge accumulation during fueling operations and there exist regulations to shut off the engine when pumping fuel into a vehicle.

Commentary by Dr. Valentin Fuster
Mechanical Engineering. 2014;136(09):75-83. doi:10.1115/9.2014-Sep-8.
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This article demonstrates the feasibility of implementing an entire sensor coating system – thermal barrier coatings – on an operating engine and successfully detecting highly precise measurements. These coatings were first used on jet engines in the 1970s and are now a common feature on power generation turbines. In the experimental design, an advanced optical probe was specifically manufactured, characterized, and implemented to enable remote detection of a moving phosphorescent spot at speeds up to 350 m/s. The comparison of the sensor coating system with a standard thermocouple measuring the temperature in the exhaust gas stream revealed that the precision of the new system was similar to that of the thermocouple and was of the order of 5K. The calibration error was estimated to be of the same order. The Viper engine results demonstrate the capability of such a system to provide precise temperature readings in the most difficult environment of a gas turbine.

Commentary by Dr. Valentin Fuster
Mechanical Engineering. 2014;136(09):76-77. doi:10.1115/9.2014-Sep-9.
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This article discusses the use of turbine single-crystal blades in gas turbines. Single-crystal turbine blades were first used in military engines on Pratt’s F100 engine, which powered the F16 and F15 fighter aircrafts. Their first commercial use was on P&WA’s JT9D-7R4 engine, which received FAA certification in 1982, powering Boeing’s 767 and the Airbus A310. In jet engines, single-crystal turbine airfoils have proven to have as much as nine times more relative life in terms of creep strength and thermal fatigue resistance and over three times more relative life for corrosion resistance, when compared to equiaxed crystal counterparts. Modern high turbine inlet temperature jet engines with long life would not be possible without the use of single-crystal turbine airfoils. By eliminating grain boundaries, single-crystal airfoils have longer thermal and fatigue life, are more corrosion resistant, can be cast with thinner walls, and have a higher melting temperature. These improvements all contribute to higher gas turbine thermal efficiencies.

Commentary by Dr. Valentin Fuster

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