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DMD (Duchenne muscular dystrophy) is a genetic disorder characterized by progressive muscle weakness, leading to the eventual loss of muscle function. After losing lower extremity function, DMD patients lose the ability to use their arms. To assist individuals with DMD, an upper extremity exoskeleton is being developed to provide support. The device is required to provide proper weight compensation for the weight of both the user and the support system. Previous literature review has highlighted three strategies for achieving compensation: Model, Calibration dynamic and Calibration static. However, the review lacks a conclusive understanding of the differences between these strategies. Thus, this study aims to validate a weight compensation model by comparing the joint torque with two different measurements: Calibration static and Calibration dynamic on non-disabled participants with a one DOF (Degree of freedom) elbow support system. The weight compensation model was designed to accurately account for the weight of the user's arms and the exoskeleton device itself. It incorporates multiple inputs, including shoulder flexion, shoulder abduction, elbow joint angle, arm mass, and arm center of mass to calculate the required compensation torque for the motor located at the elbow joint. The model was validated by a dead weight experiment. The weight compensation model was validated by comparing the joint torque measurements from Calibration dynamic and Calibration static results. Afterwards, experiments were performed on 12 male non-disabled participants. The weight compensation model results does not align well with the measurements from non-disabled participants. Analysis suggests that joint impedance caused these discrepancies. However, even after accounting for joint impedance, the weight compensation model still exhibits a tendency to overestimate the required compensation torque. A fitted model was used to decrease the product value of, Biomedical Engineering

Duchenne Muscular Dystrophy (DMD) patients suffer from a severe form of progressive muscular weakness. Consequently, as the disease progresses these patients become more and more dependent on assistive devices for their daily activities. For instance lifting their arms against gravity already becomes challenging. So far, a considerable amount of effort has been put in the development of assistive devices. However, compensating the weight of the hand remains challenging as the required balancing torques are dependent on the position of the hand and the orientation of the forearm. In this research a solution is proposed to passively compensate the weight of the hand by making use of a simplified torque profile (a constant torque). The effectiveness of this profile was assessed experimentally in a group of healthy subjects. For this the wrist muscle activity required to lift the hand against gravity was measured through surface electromyography, for several types of compensation. From this experiment the conclusion can be drawn that a constant torque profile performs similar to the theoretically ideal type of balancing, showing a similar reduction in the anti-gravity muscle activity. Based on these findings, a mechanism has been developed capable of providing an adjustable constant force, by making use of a combination of positive and negative stiffness springs, for implementation in a wrist support for DMD patients., Mechanical Engineering | Mechatronic System Design (MSD)

Because the human arm and leg have a similar skeletal structure, it may be possible to use the leg to operate a robot by the master-slave method. However, operation by the leg with six degrees of freedom has two problems. First, people move their ankle with a curved motion despite intending to move it linearly. Second, it is a burden for the operator to suspend their legs in the air during operation. This study dealt with these problems. For the first problem, we hypothesized that one of the reasons was that the muscle load of a curved motion was smaller than that of a linear motion, and we quantitatively compared them by musculoskeletal analysis. The muscle loads of curved motions were 20% smaller in the anteroposterior direction, 3.1% to 23.8% smaller in the lateral direction, and 10% smaller in the vertical direction than linear motions, which showed that the hypothesis was consistent. Further, comparison of the analysis results with the results of a previous study suggested that subjects unconsciously tried to reduce the muscle load and to move closer to a linear line when they moved their ankle while consciously intending to make a linear motion. For the second problem, we developed two different prototypes of a leg support device. An experiment to evaluate the effectiveness of these devices showed that subjective exercise intensity of the tasks in the experiment using the devices was 40% or more less than that without the device, which proved the effectiveness of the devices.

Existe un número creciente de individuos, personas mayores o con bajo tono muscular que requieren de asistentes para el desarrollo de sus actividades diarias. El uso de dispositivos mecánicos que auxilien el esfuerzo muscular en los movimientos, constituye una alternativa interesante y complementaria, que otorga a sus usuarios una menor dependencia y un aumento de la autoestima y el bienestar. En este Trabajo de Fin de Grado se ha modelado matemáticamente un exoesqueleto pasivo para miembros inferiores, que auxilia el esfuerzo muscular durante la marcha. Este dispositivo se ha diseñado de acuerdo al principio de compensación de la gravedad y en base a la biomecánica del ciclo de marcha humana. La estructura del exoesqueleto consta de tres eslabones principales (cadera, muslo y pierna) y dos auxiliares, y utiliza dos resortes para la compensación de la gravedad y la reserva/entrega de energía. Se ha tratado de interpretar la demanda de los potenciales usuarios y transformarlas en especificaciones de diseño, optando por soluciones tecnológicas adecuadas, que resuelven cuestiones fundamentales, como el bajo coste, la simplicidad mecánica o la personalización de los ajustes. Se ha optado por el empleo de aluminio, un material ligero y de mecanizado fácil y rápido. Para su adaptabilidad a diferentes usuarios, los eslabones del exoesqueleto podrían ser telescópicos para adaptarse al tamaño de las extremidades, y el grado de ayuda es regulable modificando los puntos de anclaje de los resortes. Se asegura la libertad de movimiento del usuario en el plano sagital, y una razonable confortabilidad con un bajo impacto estético. Se ha analizado la biomecánica de la marcha humana, y se ha modelado satisfactoriamente mediante la discretización de los datos la cinemática de los ángulos de extensión de la cadera y flexión de la rodilla, y de la reacción del suelo, de acuerdo a los perfiles obtenidos en la revisión bibliográfica. Asimismo, se ha realizado de manera satisfactoria el a, There is a growing number of individuals, elderly people or with low muscle tone requiring assistants for the development of their daily activities. The use of mechanical devices helping the muscle effort in movements constitutes an interesting and complementary alternative, which gives its users less dependence and an increase in self-esteem and well-being. In this End-of-Grade Thesis, a passive exoskeleton for lower limbs has been mathematically modelled, which assists muscular effort on walking. This device has been designed according to the principle of gravity compensation and based on the biomechanics of the human gait cycle. The structure of the exoskeleton consists of three main links (hip, thigh and leg) and two auxiliary ones, and uses two springs for compensation of gravity and reserve/delivery of energy. We have tried to interpret the users demands and transform them into design specifications, opting for appropriate technological solutions that solve fundamental questions such as low cost, mechanical simplicity or customization ofsettings. Aluminium, a lightweight material and of easy and fast machining, has been chosen. For their adaptability to different users, the primary links of the exoskeleton are constituted by telescopic elements, and the degree of assistance is adjustable by modifying the anchor points of the springs. This design ensures freedom of movement to the user in the sagittal plane, and a reasonable comfort with a low aesthetic impact. The biomechanics of the human gait have been analyzed and the kinematics of the hip extension angles and of the knee flexion as well as the soil reaction have been satisfactorily modelled using the Finite Element Method, according to the profiles obtained in the bibliographic review. Likewise, kinematic and dynamic analysis and simulation of the lower extremity during gait, with and without exoskeleton, using the MATLAB R2013a software, have been satisfactorily performed. The elaborated MATLAB code shows

We present and analyze two arm exoskeletons based on a pantograph linkage that allow for the support of 89~N (20~pounds) at the user's hand. Using a pantograph linkage allows for a constant force to be created at the hand in any orientation when a constant vertical force is supplied to the other side of the pantograph. We present several topologies and analyze them based on feasibility of manufacture and ability to provide a near vertical force to the pantograph linkage. Simulations are created using the best topologies and the resulting forces at the hand are reported. The mechanical design of an unpowered (passive) exoskeleton which uses a gas spring mechanism is presented. Additionally, simulations and block-CAD of a powered (active) exoskeleton which uses a motor for the supply of force are presented. The performance of the passive exoskeleton is qualitatively compared with simulations.

This thesis is centered upon the published A Novel Method and Exoskeletons for Whole-arm Gravity Compensation (Turner, Hull 2020), and includes a novel concept for supporting the weight of a person's arm or robotic linkage. The design is capable of supporting weights held near the hand, and provides support regardless of position. This support is provided with a pantograph. The upper-arm and forearm bars are mirrored by smaller copies. Force applied to a pull point on the scaled copy of the arm is flipped and applied at a support point on the forearm or to a tool near the hand. Two exoskeletons, using different linkages make use of the pantograph design. These include the Panto-Arm Exo, which uses it's slim, reduced size to comfortably assist users in lifting their arm, and the Panto-Tool Exo which is designed for a support point that coincides with a mass representing a heavy tool. The differing topologies and purposes of these two devices resulted in different qualities regarding their ability to lift weight. The Panto-Arm Exo was specifically used in human subject testing, in which fourteen users wore electromyography electrodes and performed simple arm movements and holding tasks. While the Panto-Arm Exo did not undergo stringent design improvements or user-specific optimization, the device was shown to reduce muscle use in the measured upper-arm muscles for certain arm positions.

The ever increasing demand for better and cheaper electronic devices, sensors, optical components, etc. fuels innovation in nanometer precision positioning machines. However, the overall architecture of these machines has not changed much over the past years. A huge improvement in the architecture is currently impossible due to a crucial element of these machines -- namely, the gravity compensator. A gravity compensator is a passive element providing a supporting force that reduces the heat generation of the actuators in the gravity direction. Additionally, the gravity compensator is required to have a low stiffness to limit the disturbance forces due to vibrations present inside the machine. The state of the art gravity compensators are based on permanent magnets, as they are a non-contact solution providing the best performance and excellent vacuum compatibility. However, the current designs are limited to a single operating point. To enable the development of the next generation of nanometer precision positioning machines, a gravity compensator with an operating line is required. Therefore, the goal of this research is: “To design and experimentally validate a magnetic long-stroke gravity compensator for a nanometer precision positioning machine”. In this study the most suitable magnetic design was developed using various modelling techniques. Subsequently, the model and the design were validated by means of measurements taken with an experimental setup. From this study it was concluded that the design requirements can be met using high grade magnets. Thereby, with this Master Thesis, the first step has been taken towards the next generation of nanometer precision positioning machines., Mechanical Engineering | Mechatronic System Design (MSD)

We present a new method for providing gravity compensation to a human or robot arm. This method allows the arm to be supported in any orientation, and also allows for the support of a load held in the hand. We accomplish this with a pantograph, whereby one portion of the linkage duplicates the arm's geometry, and another portion of the linkage contains a scaled copy of the arm. Forces applied to the scaled copy are transferred back to the original arm.We implement these concepts with two exoskeletons: the Panto- Arm Exo, a low-prole exoskeleton that supports the arm's weight, and the Panto-Tool Exo that supports a mass held in the hand. We present two linkages used for pantographs, and analyze how different linkage dimensions and their positioning relative to the body affect the forces providing gravity compensation. We also measured the effect of the Panto-Arm exoskeleton on fourteen subjects' arm muscles during static holding tasks and a task in which subjects drew horizontal and vertical lines on a whiteboard. Even though the Panto-Arm Exo linkage geometry and forces were not optimized, it reduced the Mid Deltoid by 33-43% and the Biceps Brachii by up to 52% in several arm postures.

The mechanism presented in this paper generates a partially negative stiffness characteristic, which is suitable for the balancing of a pendulum in a gravity field. The mechanism uses deformation in the axial direction of the base joint to store potential energy. The proposed design is located next to the base joint of the pendulum in an area rarely used by other balancing mechanisms. Utilising this space makes it an attractive alternative when space in the plane of motion is restricted. The mechanism consists of two linear springs and a non-linear transmission that form a compact system which can be manufactured out of tubes. The balancing curve that is generated by the mechanism has a theoretical maximum error of < 0:05% between ±22:5° around the horizontal position. The difference between the test results and the theory ranged from 0.4 % and 1.7 %. This gravity balancing mechanism is interesting when the mechanism should be located beside the base joint and or when low hysteresis and low error are required., Mechanical Engineering | Mechatronic System Design (MSD)

The mechanism presented in this paper generates a partially negative stiffness characteristic, which is suitable for the balancing of a pendulum in a gravity field. The mechanism uses deformation in the axial direction of the base joint to store potential energy. The proposed design is located next to the base joint of the pendulum in an area rarely used by other balancing mechanisms. Utilising this space makes it an attractive alternative when space in the plane of motion is restricted. The mechanism consists of two linear springs and a non-linear transmission that form a compact system which can be manufactured out of tubes. The balancing curve that is generated by the mechanism has a theoretical maximum error of < 0:05% between ±22:5° around the horizontal position. The difference between the test results and the theory ranged from 0.4 % and 1.7 %. This gravity balancing mechanism is interesting when the mechanism should be located beside the base joint and or when low hysteresis and low error are required., Mechanical Engineering | Mechatronic System Design (MSD)

We present a new method for providing gravity compensation to a human or robot arm. This method allows the arm to be supported in any orientation, and also allows for the support of a load held in the hand. We accomplish this with a pantograph, whereby one portion of the linkage duplicates the arm's geometry, and another portion of the linkage contains a scaled copy of the arm. Forces applied to the scaled copy are transferred back to the original arm.We implement these concepts with two exoskeletons: the Panto- Arm Exo, a low-prole exoskeleton that supports the arm's weight, and the Panto-Tool Exo that supports a mass held in the hand. We present two linkages used for pantographs, and analyze how different linkage dimensions and their positioning relative to the body affect the forces providing gravity compensation. We also measured the effect of the Panto-Arm exoskeleton on fourteen subjects' arm muscles during static holding tasks and a task in which subjects drew horizontal and vertical lines on a whiteboard. Even though the Panto-Arm Exo linkage geometry and forces were not optimized, it reduced the Mid Deltoid by 33-43% and the Biceps Brachii by up to 52% in several arm postures.

We present a new method for providing gravity compensation to a human or robot arm. This method allows the arm to be supported in any orientation, and also allows for the support of a load held in the hand. We accomplish this with a pantograph, whereby one portion of the linkage duplicates the arm's geometry, and another portion of the linkage contains a scaled copy of the arm. Forces applied to the scaled copy are transferred back to the original arm.We implement these concepts with two exoskeletons: the Panto- Arm Exo, a low-prole exoskeleton that supports the arm's weight, and the Panto-Tool Exo that supports a mass held in the hand. We present two linkages used for pantographs, and analyze how different linkage dimensions and their positioning relative to the body affect the forces providing gravity compensation. We also measured the effect of the Panto-Arm exoskeleton on fourteen subjects' arm muscles during static holding tasks and a task in which subjects drew horizontal and vertical lines on a whiteboard. Even though the Panto-Arm Exo linkage geometry and forces were not optimized, it reduced the Mid Deltoid by 33-43% and the Biceps Brachii by up to 52% in several arm postures.

We present a new method for providing gravity compensation to a human or robot arm. This method allows the arm to be supported in any orientation, and also allows for the support of a load held in the hand. We accomplish this with a pantograph, whereby one portion of the linkage duplicates the arm's geometry, and another portion of the linkage contains a scaled copy of the arm. Forces applied to the scaled copy are transferred back to the original arm.We implement these concepts with two exoskeletons: the Panto- Arm Exo, a low-prole exoskeleton that supports the arm's weight, and the Panto-Tool Exo that supports a mass held in the hand. We present two linkages used for pantographs, and analyze how different linkage dimensions and their positioning relative to the body affect the forces providing gravity compensation. We also measured the effect of the Panto-Arm exoskeleton on fourteen subjects' arm muscles during static holding tasks and a task in which subjects drew horizontal and vertical lines on a whiteboard. Even though the Panto-Arm Exo linkage geometry and forces were not optimized, it reduced the Mid Deltoid by 33-43% and the Biceps Brachii by up to 52% in several arm postures.

Overexertion is a common cause of work related musculoskeletal disorder (WMSD) in the modern industry. The shoulder is one of the most susceptible joints to injury and requires the longest amount of recovery time to heal, currently accounting for about one fifth of the total cost associated with WMSD’s. Exoskeleton technology has the potential to provide beneficial augmentation to workers in many industrial fields. A strategic application of support reduces the forces exerted by the operator, potentially decreasing risk of injury and increasing productivity though the added capability. Their mobility allows for application in environments where a static aid is not feasible due to constantly changing surroundings, such as in construction or shipbuilding, or due to high costs of modifying an established manufacturing line for ergonomic benefit. As the field of shoulder supporting exoskeletons begins to emerge, little is known about the effects these devices have on operator’s effort and productivity.This work introduces a novel design for a shoulder supporting exoskeleton as well as a preliminary evaluation of the device’s effects during common workplace tasks. The exoskeleton builds off of the success of a trunk and a leg supporting exoskeleton developed at the UC Berkeley Human Engineering and Robotics Laboratory. A passive actuation strategy is presented to augment the torques about the shoulder due to the gravitational forces on the arm and a handheld tool for a variety of workplace tasks and individual preference. A modified iso-elastic base profile divides support into a working and non-working range of motion and can be modified in its amplitude, on/off state, and gravitational offset. A biomimetic frame design provides the support and motion necessary to apply the supporting torques across the shoulder joint for a majority of worker dimensions. Couplings at the arm, shoulders, and hip comfortably secure the frame to the body in a familiar manner that is easy t

An additional mechanical mechanism for a passive parallelogram-based exoskeleton arm-support is presented. It consists of several levers and joints and an attached extension coil spring. The additional mechanism has two favourable features. On the one hand it exhibits an almost iso-elastic behaviour whereby the lifting force of the mechanism is constant for a wide working range. Secondly, the value of the supporting force can be varied by a simple linear movement of a supporting joint. Furthermore a standard tension spring can be used to gain the desired behavior. The additional mechanism is a 4-link mechanism affixed to one end of the spring within the parallelogram arm-support. It has several geometrical parameters which influence the overall behaviour. A standard optimisation routine with constraints on the parameters is used to find an optimal set of geometrical parameters. Based on the optimized geometrical parameters a prototype was constructed and tested. It is a lightweight wearable system, with a weight of 1.9 kg. Detailed experiments reveal a difference between measured and calculated forces. These variations can be explained by a 60% higher pre load force of the tension spring and a geometrical offset in the construction.

Overexertion is a common cause of work related musculoskeletal disorder (WMSD) in the modern industry. The shoulder is one of the most susceptible joints to injury and requires the longest amount of recovery time to heal, currently accounting for about one fifth of the total cost associated with WMSD’s. Exoskeleton technology has the potential to provide beneficial augmentation to workers in many industrial fields. A strategic application of support reduces the forces exerted by the operator, potentially decreasing risk of injury and increasing productivity though the added capability. Their mobility allows for application in environments where a static aid is not feasible due to constantly changing surroundings, such as in construction or shipbuilding, or due to high costs of modifying an established manufacturing line for ergonomic benefit. As the field of shoulder supporting exoskeletons begins to emerge, little is known about the effects these devices have on operator’s effort and productivity.This work introduces a novel design for a shoulder supporting exoskeleton as well as a preliminary evaluation of the device’s effects during common workplace tasks. The exoskeleton builds off of the success of a trunk and a leg supporting exoskeleton developed at the UC Berkeley Human Engineering and Robotics Laboratory. A passive actuation strategy is presented to augment the torques about the shoulder due to the gravitational forces on the arm and a handheld tool for a variety of workplace tasks and individual preference. A modified iso-elastic base profile divides support into a working and non-working range of motion and can be modified in its amplitude, on/off state, and gravitational offset. A biomimetic frame design provides the support and motion necessary to apply the supporting torques across the shoulder joint for a majority of worker dimensions. Couplings at the arm, shoulders, and hip comfortably secure the frame to the body in a familiar manner that is easy t

This thesis presents the design, simulation, and evaluation of a passive, wearable, and human-scale actuator that includes pulleys and uses polymers for energy storage. Repetitive tasks such as packing boxes on an assembly line may require high strength movements of the shoulder, arm, and hand and may result in musculoskeletal disorders. With the objective to offset the weight of the arm and thereby lower the forces on the muscles in the shoulder and arm, this actuator is able to provide gravity compensation for the upper extremities of workers, if used in conjunction with an arm exoskeleton. The actuator is passive, meaning that it does not use motors or sensors, but instead creates a force on a cable that is a function of the displacement of the cable. This thesis details the design of the actuator and the selection of an appropriate polymer for use with the actuator. To determine the best polymer for this application, tests were conducted on nine polymers to ind their average Young's modulus and their hysteresis. A 90A abrasion-resistant polyurethane rubber belt was used in the final design due to its high modulus and low hysteresis. The final actuator design was tested in an Instron machine to validate its performance. During testing, the actuator provided 720N in extension and 530N in retraction, which are roughly 112% and 83% of the torque required to lift a human arm, respectively.

An additional mechanical mechanism for a passive parallelogram-based exoskeleton arm-support is presented. It consists of several levers and joints and an attached extension coil spring. The additional mechanism has two favourable features. On the one hand it exhibits an almost iso-elastic behaviour whereby the lifting force of the mechanism is constant for a wide working range. Secondly, the value of the supporting force can be varied by a simple linear movement of a supporting joint. Furthermore a standard tension spring can be used to gain the desired behavior. The additional mechanism is a 4-link mechanism affixed to one end of the spring within the parallelogram arm-support. It has several geometrical parameters which influence the overall behaviour. A standard optimisation routine with constraints on the parameters is used to find an optimal set of geometrical parameters. Based on the optimized geometrical parameters a prototype was constructed and tested. It is a lightweight wearable system, with a weight of 1.9 kg. Detailed experiments reveal a difference between measured and calculated forces. These variations can be explained by a 60% higher pre load force of the tension spring and a geometrical offset in the construction.

We present a design for a manipulator that is intrinsically mechanically safe, i.e. it can not cause pain (let alone damage) to a human being even if the control system has a failure. Based on the pressure pain thresholds for human skin, we derive a pinching safety constraint that limits the actuator torque, and an impact safety constraint that results in a trade-off between mass and velocity. To fulfill all constraints, the manipulator requires a spring balancing system that counteracts gravity in all configurations of the manipulator. This allows the use of extremely low-power DC motors (only 4.5 W). Thanks to the torque and speed limitations of these motors the manipulator is indeed intrinsically safe, yet still capable of moving a useful payload of 1.2 kg over a distance of 0.8 m in 1.5 s., Biomechanical Engineering, Mechanical, Maritime and Materials Engineering

We present a design for a manipulator that is intrinsically mechanically safe, i.e. it can not cause pain (let alone damage) to a human being even if the control system has a failure. Based on the pressure pain thresholds for human skin, we derive a pinching safety constraint that limits the actuator torque, and an impact safety constraint that results in a trade-off between mass and velocity. To fulfill all constraints, the manipulator requires a spring balancing system that counteracts gravity in all configurations of the manipulator. This allows the use of extremely low-power DC motors (only 4.5 W). Thanks to the torque and speed limitations of these motors the manipulator is indeed intrinsically safe, yet still capable of moving a useful payload of 1.2 kg over a distance of 0.8 m in 1.5 s., Biomechanical Engineering, Mechanical, Maritime and Materials Engineering