Antropomotoryka nr 57 [2012]. - Akademia Wychowania Fizycznego ...

Emilia Mikołajewska, Dariusz Mikołajewskireal time on neuro-muscle level, may lead to intuitivesteering of the exoskeleton and the user’s full integrationwith it. The user perceives the exoskeleton then,as an extension (expanding the capabilities) of his ownbody [12].In the simplest sense of the term, the full cycle ofthe steering of the exoskeleton covers the followingstages realized in the real time:• reading from sensors the intention of the user tomake a movement,• interpretation of that intention while taking into accountthe up-to-date behavior and the programmedpatterns of movement,• interaction of the exoskeleton movement with theuser’s movement while simultaneously strengtheningthe power, reducing the support or even replacingthe deficient part of the user’s body (accordingto needs),• analysis of the final position, and launching the successivecycle [6, 7, 8].The proper realization of the above-mentioned algorithmis being fulfilled by the subordinated detailedfunctioning of the whole (most often doubled) exoskeletonsteering system. It ensures at the same time:• maintenance of the movement and particular positionswithin the frames of natural patterns or thepatterns close to natural for a particular user – themost interesting aspect from biomechanical point ofview,• comfortable and bearable use of the exoskeleton ina long period of exploitation, at altered effort, andmultiple repetitions [8].Human-machine interactionBelow a description of the chosen solutions to the areaof human-machine interaction used in the contemporaryexoskeletons is placed.Myoprocessors [12] are realized in the course ofHMI computationally as the real time models of all themuscles covered by support. These models, workingin combination with the functioning muscle, allowconducting the anticipatory identification of which ofthe muscles – and in what way – will be successivelyactivated. By that means, one can – on the basis of kinematicsof the joints and levels of the activation on theneuronal level – anticipate, for instance, the momentsin joints. It is also possible, due to the fact that eachuser has at his disposal the source of natural movementpatterns, either fairly limited or relatively close tothe natural. The set is also learning in the process ofadjusting the exoskeleton to the user’s needs and inthe process of its entire exploitation. These patternsenable creating the internal database for the needs ofHMI, which allow the calculation, for example of the initialstages of each movement and the assessment andeventual correction of the supporting of the movementby the exoskeleton. These procedures are quite complicatedand they require the involvement of artificialintelligence (for instance GA – genetic algorithms, andsuch complex muscle models as Hill phenomenologicalmuscle model). The recent studies have indicated higheffectiveness of that kind of solutions, as sufficient toolsfor practical use [12].For the time being, the most common type of controlis steering of the exoskeleton with simultaneous applicationof all solutions or the ones chosen from thefollowing solutions:• electro-myographic sensors,• gyroscopic sensors of the position,• sensors of the power of pressure on the foundation,• sensors of acceleration,• sensors of the angles of bending the joints oflimbs,• ultimately (during the research): brain-computer interfaceand steering of the exoskeleton as the comprehensiveand advanced neuroprosthetics [1, 2, 3,13].Conducting electromyography [14] is commonlyused, due to the fact that EMG signals reflect directlythe intention of the user to make a movement. Varioussolutions are examined in this respect:• the exoskeletons for lower limbs with various levelsof the freedom of movement (from level one upwards)in the knee joint, less frequently also in theankle joint (although it is very important for the properwalk) – mostly used for supporting the movementof the disabled people,• the exoskeletons for lower limbs ankle-knee-hipwith the artificial (according to needs) substitutes ofall important muscles – mostly used for re-educationof walk, including the patients with hemiplegiawith the regulated relieve of both the paralyzed andthe healthy sides,• the exoskeletons supporting also the movement ofthe upper limbs: the movement of an arm and themovement in the elbow joint, less frequently in the– 118 –