System for tripping emulation and swing assistance during treadmill walking

Padci predstavljajo visoko tveganje za poškodbo, zlasti pri starejših. Pacienti, ki okrevajo po možganski kapi, imajo slabše dinamično ravnotežje, zato so za padce dodatno dovzetni. Poleg tega imajo zaradi oslabelosti mišic in spastičnosti v svojem vzorcu hoje številne nepravilnosti. Vzrok velikega deleža padcev so spotiki. V procesu rehabilitacije je pomembno, da iz pacientovega cikla hoje eliminiramo deviacije od zdravega cikla hoje, katerih prisotnost povečuje tveganje za spotik in padec. Ker se spotikanju v realnem okolju ne moremo izogniti, je pomembno, da je v rehabilitacijski proces vključen tudi trening povrnitve dinamičnega ravnotežja. Skozi trening se pacient nauči strategij, ki mu omogočajo, da se kljub spotiku izogne padcu. V modernih programih rehabilitacije si veliko pomagamo z roboti. Naš cilj je razviti napravo za rehabilitacijo spodnjih ekstremitet pri hoji po tekočem traku, ki deluje po zgledu tetivnih robotov. Naprava bo modularna, cenovno dostopna in varna, saj razen tekočega traku ne bo vsebovala aktivnih elementov. V tem delu predstavljamo razvoj dveh podsistemov naprave. Prvi je sistem za posnemanje spotikanja, drugi pa za pomoč pri zamahu noge pri hoji po tekočem traku. Razvili smo napravo za posnemanje spotikanja in izdelali njen prototip. Naprava omogoča izvajanje perturbacij na nogo med hojo po tekočem traku. Perturbacijo predstavlja zaustavitev gibanja gležnja v anteriorni smeri za kratek časovni interval. Delovanje naprave smo evalvirali na enem zdravem prostovoljcu. Prostovoljec je hodil po instrumentacijskem tekočem traku, s katerim smo merili reakcijsko silo podlage v vseh smereh ter mesto prijemališča reakcijske sile podlage na tekočem traku. Na izbranih anatomskih mestih telesa prostovoljca so bili nameščeni odsevni markerji, s pomočjo katerih smo s sistemom kamer za zajem gibanja posneli kinematiko segmentov telesa. Prostovoljec je hodil pri treh počasnih hitrostih hoje. Rezultati kažejo, da algoritem za proženje perturbacij razpoznava cikle hoje ter robustno in ponovljivo proži perturbacijo v izbranem trenutku znotraj cikla hoje. Meritve sile podlage in prijemališča sile podlage kažejo, da je ravnotežni odziv po perturbaciji podoben ravnotežnim odzivom po spotiku, ki jih najdemo v literaturi. Posnetek kinematike segmentov telesa nakazuje na to, da lahko z ustrezno nastavitvijo dolžine perturbacije in hitrosti tekočega traku ponovljivo izzovemo strategije za povrnitev ravnotežja, ki jih opisuje literatura. Sistem za pomoč pri zamahu noge pri hoji po tekočem traku smo razvili v simulacijskem okolju. Izdelali smo dinamični model noge, ki posnema delovanje trisegmentnega ravninskega serijskega robotskega mehanizma. Dinamiko noge v zamahu smo modelirali z Newton-Eulerjevo metodo. Oslabelost mišic smo modelirali z zmanjšanimi navori v sklepih, spastičnost pa kot povečani mišični tonus, ki ustvarja navore v sklepih, ki zavirajo gibanje. Zamah hemiparetične noge smo želeli popraviti z uporabo elastičnih vrvi. V elastičnih vrveh se v fazi opore shrani energija, ki jo v sistem vnaša tekoči trak, v fazi zamaha pa vrvi pomagajo, da hemiparetična noga izvede zamah, katerega kinematika je čim bolj podobna zamahu pri zdravi hoji. Za vsako elastično vrv je mogoče izbrati trenutek začetka napenjanja in trenutek prenehanja delovanja vrvi. Simulirali smo vodenje sistema z genetskim algoritmom ter z algoritmom vodenja z iterativnim učenjem (ILC). Oba algoritma omogočata zadovoljivo vodenje napenjanja in delovanja elastičnih vrvi v simulacijskem okolju. V obeh primerih lahko z uporabo elastičnih vrvi dosežemo, da postane zamah hemiparetične noge v ključnih parametrih bolj podoben zamahu zdrave noge. Zaradi lažje implementacije bomo v realnem sistemu za vodenje uporabili algoritem vodenja z iterativnim učenjem. S pomočjo simulacije smo določiti tudi ostale proste parametre pri načrtovanju sistema. Iz evalvacije prvega podsistema sklepamo, da je človekov odziv na perturbacijo, ki jo izvedemo z našo napravo za posnemanje spotikanja, dovolj podoben odzivu na spotik ob fizično oviro, da bi bilo napravo smiselno uporabiti v postopku rehabilitacije. Rezultati simulacijske študije sistema za pomoč pri zamahu noge pri hoji po tekočem traku kažejo, da je sistem pripravljen za implementacijo in primeren za uporabo v rehabilitaciji hoje pacientov, ki okrevajo po možganski kapi.Falls are a major health hazard. The risk of falls is higher for the elderly as well as stroke survivors, whose dynamic balancing capabilities are impaired. Stroke survivors also suffer from muscle weakness and spasticity, which result in a gait, that differs significantly from the gait of the able-bodied. A large part of falls is caused by trips. The goal of the rehabilitation process is to reduce gait deviations that increase the risk of tripping and falling. It is also important for the rehabilitation process to include dynamic balancing training. This training helps patients learn how to employ trip recovery strategies in the events when tripping unexpectedly occurs. Modern rehabilitation processes are often supported by rehabilitation robots. Our goal was to develop a lower limb rehabilitation device for treadmill walking, inspired by tendon-driven robots. The device should be modular, inexpensive and safe. The only active part of the system is going to be a treadmill. Development of two subsystems that will make up this device is presented. The first one is a system for tripping emulation and the second one is a system for swing assistance during treadmill walking. A device for tripping emulation during treadmill walking was developed and prototyped. The device can create gait perturbations by preventing the ankle from moving in the anterior direction for the duration of a short interval of time. To evaluate the device a tripping experiment was conducted on one healthy subject. The subject walked on an instrumented treadmill at three slow walking speeds. Measurement of ground reaction force and center of pressure were taken. Measurements of kinematics of body segments were made using a full-body set of reflective markers and a motion capture system. Results indicate that the algorithm that triggers perturbations is able to successfully segment gait cycles into basic gait phases. Perturbations are triggered in the correct timeframe within the swing phase in a repeatable and robust manner. Measurements of center of pressure and ground reaction force indicate that the perturbation induced balancing response is similar to balancing responses after tripping described in literature. The system for swing assistance during treadmill walking was developed using a simulation software. A human leg dynamic model was developed. The leg is modelled like a three-link planar serial robot using the Newton-Euler method. Muscle weakness was modelled with a decrease in joint torques. Spasticity was modelled like increased muscle tone, that creates torques which oppose joint movement. The goal of the system is to assist with the movement of the hemiparetic limb in the swing phase. This is done using elastic ropes. Elastic ropes can store energy by extending while the leg is moving backwards on the treadmill, and release this energy in the swing phase, causing the movement of the hemiparetic leg to better match the movement of an able-bodied person’s leg in swing phase. The time when an elastic rope starts extending and the time when the assistance of a rope is cut off can be controlled for each individual rope. Two control algorithms were tested: a genetic algorithm and an iterative learning control algorithm. Both control algorithms produce satisfactory results, improving the key parameters of the hemiparetic swing when elastic ropes are used for assistance. Due to easier future implementation in a real-time computing environment, the iterative learning control algorithm was chosen. Other design parameters of the system were also tested and chosen using this simulation. From the evaluation of the first subsystem we conclude that a person’s balancing response, induced by the device for tripping emulation, closely resembles the balancing response which occurs after tripping over a physical obstacle. Therefore, the device has potential for use in rehabilitation. Results of the simulation of the system for swing assistance during treadmill walking indicate that the system is ready for implementation and can be used in rehabilitation of stroke survivors

Real-Time Gait Event Detection with Adaptive Frequency Oscillators from a Single Head-Mounted IMU

Accurate real-time gait event detection is the basis for the development of new gait rehabilitation techniques, especially when utilizing robotics or virtual reality (VR). The recent emergence of affordable wearable technologies, especially inertial measurement units (IMUs), has brought forth various new methods and algorithms for gait analysis. In this paper, we highlight some advantages of using adaptive frequency oscillators (AFOs) over traditional gait event detection algorithms, implemented a real-time AFO-based algorithm that estimates the gait phase from a single head-mounted IMU, and validated our method on a group of healthy subjects. Gait event detection was accurate at two different walking speeds. The method was reliable for symmetric, but not asymmetric gait patterns. Our method could prove especially useful in VR applications since a head-mounted IMU is already an integral part of commercial VR products

Korundna zaščita magnetokaloričnih hladilnih elementov pripravljena z metodo nanašanja delcev v curku aerosola

In this work the preparation of a protective insulating alumina coating on magnetocaloric gadolinium elements was investigated. In order to prepare a dense ceramic coating at room temperature the aerosol deposition technique was used. The study reveals that the powder morphology and particle size are important parameters that influence the deposition efficiency, powder packing and consequently also the density and functional properties of the alumina coating. The optimal powder pre-deposition treatment includes heating the powder to 1150 °C, followed by milling. The deposition of this powder resulted in the preparation of dense alumina coatings with a low specific electrical conductivity of 6.4.10-14 [Omega]-1m-1

Investigating the feasibility of preparing metal-ceramic multi-layered composites using only the aerosol-deposition technique

The preparation of metal–ceramic layered composites remains a challenge due to the incompatibilities of the materials at the high temperatures of the co-firing process. For densification, the ceramic thick-film materials must be subjected to high-temperature annealing (usually above 900 °C), which can increase the production costs and limit the use of substrate or co-sintering materials with a low oxidation resistance and a low melting point, such as metals. To overcome these problems, the feasibility of preparing dense, defect-free, metal–ceramic multilayers with a room-temperature-based method should be investigated. In this study, we have shown that the preparation of ceramic–metal Al$_2$O$_3$/Al/Al$_2$O$_3$/Gd multilayers using aerosol deposition (AD) is feasible and represents a simple, reliable and cost-effective approach to substrate functionalisation and protection. Scanning electron microscopy of the multilayers showed that all the layers have a dense, defect-free microstructure and good intra-layer connectivity. The top Al$_2$O$_3$ dielectric layer provides excellent electrical resistance (i.e., 7.7 × 10$^{12}$ Ω·m), which is required for reliable electric field applications

Investigation of structural and electrical properties of ▫Al2O3/AlAl_2O_3/Al▫ composites prepared by aerosol co-deposition

As the microelectronic industry develops, components that can perform several different tasks receive increasingly more attention, resulting in multifunctional materials being highly sought after. ▫$Al_2O_3$▫ is widely present in electronic applications as a protective coating or as an electrical and thermal insulator due to its mechanical and thermal stabilities and chemical inertness. ▫$Al_2O_3$▫ is also an important dielectric material, with high resistivity and stable permittivity over a wide range of temperatures and electric fields, but its modest permittivity necessitates large effective areas or extremely thin layers when a large capacitance is desired. Composites consisting of discrete conducting phases within an insulating matrix can produce large capacitance via Maxwell–Wagner polarization. In this work, ▫$Al_2O_3$▫/Al composite thick films with different volume ratios of Al were prepared using the aerosol deposition method. A relative dielectric permittivity (εr′) of 800 at 1 MHz was achieved at 27 vol% of Al, a sixty-sevenfold enhancement compared to ▫$Al_2O_3$▫. On the other hand, dielectric losses, tan(δ), at 1 MHz increased from 0.01 for ▫$Al_2O_3$▫ up to 0.58 for the composite with 27 vol% of Al. A finite-element model of the composites was implemented, supporting the nonlinear electrical behavior of the composites as function of vol% of Al. Our results show novel possibilities for the applications of ▫$Al_2O_3$▫-based materials in the microelectronic industry, especially for temperature-sensitive applications, for which the integration strengths of aerosol deposition are valuable