Entwicklung eines mobilen motorisierten Arm-Exoskeletts

Abstract

In vielen Fällen ist es Personen mit eingeschränkter motorischer Funktion der Arme nicht möglich alltägliche Bewegungen wie Essen, Trinken, sich Kämmen oder Kratzen auszuführen. Der Verlust dieser Funktionalität bedeutet einen massiven Einschnitt in deren Eigenständigkeit und Lebensqualität. Deshalb wurde im Rahmen dieser Diplomarbeit ein Exoskelett entwickelt, welches die Wiederausführung dieser Bewegungen ermöglichen soll. Der Aufbau des Exoskeletts erfolgt durch die Aneinanderreihung verschiedener Module, welche mit CFK-Stangen verbunden sind. Die Module können auf den Stangen verschoben und anschließend festgeklemmt werden. Dies ermöglicht eine unkomplizierte und schnelle Einstellung des Exoskeletts auf den jeweiligen Träger. Durch diesen modularen Aufbau ist es auch möglich - falls medizinisch gefordert - nur bestimmte Module zu verwenden. Um die Baugröße möglichst klein zu halten und zusätzlich Gewicht zu sparen, wurden für die Motorisierung kleine Schrittmotoren mit Spezialgetrieben der Firma HarmonicDrive® verwendet, die neben der kompakten Baugröße auch hohe Untersetzungen aufweisen und somit für den Einsatz im Exoskelett hervorragend geeignet sind. Auch wurden viele Teile aus Kohlefaserverbundwerkstoffen hergestellt, um Gewichts- und Baugrößeneinsparungen bei gleicher Festigkeit zu erlangen. Jeder der Schrittmotoren wird über eine spezielle Schrittmotor-Steuerung angesprochen. Die Steuerungen werden über einen speziellen Transformator mit Strom versorgt und sind in der Lage sowohl den Motor zu steuern als auch die Winkellagen und Endpositionen per USB-Anschluss an das Notebook zu übermitteln. Eine LabView® Routine kommuniziert ununterbrochen mit allen Schrittmotorsteuerungen und kann vorgegebene Bewegungsmuster wie z.B. Trinken, Kratzen, etc. ausführen. Die Encodersignale liefern dazu andauernd die Winkellagen der einzelnen Gelenksbewegungen, sodass das Programm auch bei Schrittverlust des Schrittmotors die gewünschten Bewegungen positionsrichtig ausführen kann. Ein spezieller Initialisierungsvorgang aller Schrittmotoren verfährt jedes Modul einzeln in seine Endlage und ermöglicht somit eine gleichbleibende Genauigkeit. Nach jeder Bewegungsausführung, sowie nach einer Initialisierung, wird eine speziell definierte "Standby-Haltung" des Exoskeletts angefahren, um den Tragekomfort zu erhöhen. Erste Tests haben gezeigt, dass das Exoskelett angenehm zu tragen ist und bei korrekter Anpassung an den Arm keine Zwangskräfte in den Gelenken generiert. Zurzeit werden die Steuerungsroutinen optimal erweitert, sowie das gesamte Konzept für spätere Tests vorbereitet. Es wird auch an einem "Lernmodus" gearbeitet, der eine Aufzeichnung von manuell ausgeführten Bewegungen ermöglichen soll, welche dann auf Abruf zu einem späteren Zeitpunkt wieder abgespielt werden können. Im Folgenden ist auch geplant, das Exoskelett im Rahmen einer medizinischen Studie in einem Rehabilitationszentrum mit geeigneten Probanden zu testen.

People suffering from neuromuscular diseases have troubles performing elementary activities of living such as eating, drinking, combing or scratching. The loss of this functionality represents a massive cut in their independence and quality of life. As part of this thesis an exoskeleton was developed, which should enable to re-perform these movements. The construction consists of five basic modules, which are connected with carbon rods or carbon tubes and fixated with clamping mechanisms. This allows the adaption on various arm sizes in a simple way. In addition the modular construction allows the use of individual modules, if clinically needed. To minimize the overall size of the motor gearbox unit by simultaneous high torque output, combinations of gearboxes with high gear reduction and miniature stepper motors were needed. For every module a combination of HarmonicDrive People suffering from neuromuscular diseases have troubles performing elementary activities of living such as eating, drinking, combing or scratching. The loss of this functionality represents a massive cut in their independence and quality of life. As part of this thesis an exoskeleton was developed, which should enable to re-perform these movements. The construction consists of five basic modules, which are connected with carbon rods or carbon tubes and fixated with clamping mechanisms. This allows the adaption on various arm sizes in a simple way. In addition the modular construction allows the use of individual modules, if clinically needed. To minimize the overall size of the motor gearbox unit by simultaneous high torque output, combinations of gearboxes with high gear reduction and miniature stepper motors were needed. For every module a combination of HarmonicDrive® gearboxes with stepping motors were chosen. Considering additional weight reduction, for many parts carbon-fibre materials were chosen. All stepping motors are armed with angle encoders. This provides precise positioning information and enables a correct movement of the exoskeleton. For every stepping motor an own controller was taken. All controllers communicate via USB and can be actuated by a computer. To reduce cables, all controllers were connected with an USB hub. The electric equipment works on 48V DC that will be provided by a power supply. With a LabView® routine the communication of all stepper motor controllers is given and it is possible to carry out movement patterns such as Drinking, scratching, etc. The encoder signals provide the live time angular positions of the individual joint movements, so that the program can perform the desired movements. Due to this concept, the loss of steps doesnt have any effect. A special initialization routine for all stepper motors enables a constant accuracy. After each movement or after initialization, a specially defined "standby position" of the exoskeleton is approached to increase the wearers comfort. First tests on the prototype had shown that the motorized arm exoskeleton fits very well to the arm. If the exoskeleton is adapted to the wearer¿s anthropometric properties, there are no determinable generated restraint forces in the joints. Currently the control routines and the whole concept will be optimized for additional tests in the future. Moreover a "Teaching Mode" will be developed will should enable recording manually specific movements that can be later performed on demand. In the near future it is planned to test the exoskeleton in a medical study carried out in a rehabilitation center with appropriate subjects.People suffering from neuromuscular diseases have troubles performing elementary activities of living such as eating, drinking, combing or scratching. The loss of this functionality represents a massive cut in their independence and quality of life. As part of this thesis an exoskeleton was developed, which should enable to re-perform these movements. The construction consists of five basic modules, which are connected with carbon rods or carbon tubes and fixated with clamping mechanisms. This allows the adaption on various arm sizes in a simple way. In addition the modular construction allows the use of individual modules, if clinically needed. To minimize the overall size of the motor gearbox unit by simultaneous high torque output, combinations of gearboxes with high gear reduction and miniature stepper motors were needed. For every module a combination of HarmonicDrive® gearboxes with stepping motors were chosen. Considering additional weight reduction, for many parts carbon-fibre materials were chosen. All stepping motors are armed with angle encoders. This provides precise positioning information and enables a correct movement of the exoskeleton. For every stepping motor an own controller was taken. All controllers communicate via USB and can be actuated by a computer. To reduce cables, all controllers were connected with an USB hub. The electric equipment works on 48V DC that will be provided by a power supply. With a LabView® routine the communication of all stepper motor controllers is given and it is possible to carry out movement patterns such as Drinking, scratching, etc. The encoder signals provide the live time angular positions of the individual joint movements, so that the program can perform the desired movements. Due to this concept, the loss of steps doesnt have any effect. A special initialization routine for all stepper motors enables a constant accuracy. After each movement or after initialization, a specially defined "standby position" of the exoskeleton is approached to increase the wearers comfort. First tests on the prototype had shown that the motorized arm exoskeleton fits very well to the arm. If the exoskeleton is adapted to the wearers anthropometric properties, there are no determinable generated restraint forces in the joints. Currently the control routines and the whole concept will be optimized for additional tests in the future. Moreover a "Teaching Mode" will be developed will should enable recording manually specific movements that can be later performed on demand. In the near future it is planned to test the exoskeleton in a medical study carried out in a rehabilitation center with appropriate subjects.gearboxes with stepping motors were chosen. Considering additional weight reduction, for many parts carbon-fibre materials were chosen. All stepping motors are armed with angle encoders. This provides precise positioning information and enables a correct movement of the exoskeleton. For every stepping motor an own controller was taken. All controllers communicate via USB and can be actuated by a computer. To reduce cables, all controllers were connected with an USB hub. The electric equipment works on 48V DC that will be provided by a power supply. With a LabView® routine the communication of all stepper motor controllers is given and it is possible to carry out movement patterns such as Drinking, scratching, etc. The encoder signals provide the live time angular positions of the individual joint movements, so that the program can perform the desired movements. Due to this concept, the loss of steps doesn¿t have any effect. A special initialization routine for all stepper motors enables a constant accuracy. After each movement or after initialization, a specially defined "standby position" of the exoskeleton is approached to increase the wearers comfort. First tests on the prototype had shown that the motorized arm exoskeleton fits very well to the arm. If the exoskeleton is adapted to the wearer¿s anthropometric properties, there are no determinable generated restraint forces in the joints. Currently the control routines and the whole concept will be optimized for additional tests in the future. Moreover a "Teaching Mode" will be developed will should enable recording manually specific movements that can be later performed on demand. In the near future it is planned to test the exoskeleton in a medical study carried out in a rehabilitation center with appropriate subjects.