Carrying a payload directly on the body is an unavoidable aspect of human life. Human bipedal locomotion knows no equal: people travel on foot to virtually every corner of the globe. Despite the efficiency and convenience of wheeled apparatus, uneven terrain, enclosed environments and accessibility limits require virtually every transportation task to include a phase in which material goods must be physically carried by a person. As of today, no artificial intelligence or programmed behavior has been able to match a human’s ability to balance and maneuver in unstructured real-world environments. The Berkeley Lower Extremity Exoskeleton solves the problem of supporting and carrying heavy loads on the body and allows a person to navigate unencumbered by the weight of the payload they are carrying. The Berkeley Lower Extremity Exoskeleton is an anthropomorphic and energetically autonomous robotic device comprised of two legs, a backpack, a harness system and a control computer that provides a wearable load support platform. This thesis presents a control scheme called Sensitivity Amplification Control that enables an exoskeleton to support a payload and shadow the movement of the wearer in an intuitive and unobtrusive manner. The control algorithm developed here increases the closed-loop system sensitivity to its wearer’s forces and torques without any measurement from the wearer. This strategy requires an accurate dynamic model of the system but does not require direct measurements from the human. The trade-off between not having sensors to measure human action and the sacrificed robustness due to model parameter variation is described. A modification to the controller is also explored that partially circumvents this limitation.

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Metabolic studies have shown that there is a metabolic cost associated with carrying load (T. M. Griffen, et al., 2003). In previous work, a lightweight, underactuated exoskeleton has been described that runs in parallel to the human and supports the weight of a payload (C. J. Walsh, et al., 2006). A state-machine control strategy is written based on joint angle and ground-exoskeleton force sensing to control the joint actuation at thisexoskeleton hip and knee. The joint components of the exoskeleton in the sagittal plane consist of a force-controllable actuator at the hip, a variable-damper mechanism at the knee and a passive spring at the ankle. The control is motivated by examining human walking data. Positive, non-conservative power is added at the hip during the walking cycle to help propel the mass of the human and payload forward. At the knee, the damper mechanism is turned on at heel strike as the exoskeleton leg is loaded and turned off during terminal stance to allow knee flexion. The passive spring at the ankle engages in controlled dorsiflexion to store energy that is later released to assist in powered plantarflexion. Preliminary studies show that the state machines for the hip and knee work robustly and that the onset of walking can be detected in less than one gait cycle. Further, it is found that an efficient, underactuated leg exoskeleton can effectively transmit payload forces to the ground during the walking cycle.

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Using CMU actuators, a Prototype of Mechanical Assistance Device for the Wrist’s Flexion Movement (PMA) was developed and probed in a mechanical model, in order to be implemented in a future as a dynamic powered orthosis or as a rehabilitation assistant instrument. Two Mayor Actuators conformed by three CMU actuators arranged in a series configuration, allows to an artificial hand to be placed in four predefined positions: 0º, 20º, 40º and 60º. The synchronism and control of the actuators is achieved with the Programmable Control Module (PCM). It is capable to drive up to six CMU actuators, and possess two different modes of execution: a Manual mode and an Exercise mode. In the Manual Mode, the position of the hand responds directly to the commands of the keyboard of the front panel, and in the Exercise mode, the hand realizes a repetitive and programmed movement. The prototype was tested in 100 positions in the Manual Mode and for 225 works cycles in the Exercise Mode. The relative repetition error was less than 5% for both test. This prototype only consumes 4,15W, which makes it possible to be powered by small rechargeable batteries, allowing its use as a portable device.

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A novel multi-fingered exoskeleton haptic device using passive force feedback has been proposed by the authors. The haptic device solves the conventional problems of previously developed master-slave systems with force feedback, such as oscillations, complex structures and complicated control algorithm. However, some problems still remain in the conventional passive elements. In the present paper, an ultrasonic clutch for multi-fingered exoskeleton haptic device with passive force feedback function is developed. The ultrasonic clutch can solve problems of conventional passive elements, such as time delay, instability, and large size, by using unique characteristics of ultrasonic motor, as fast response, silent motion, and non-magnetic feature. It can also be designed to be smaller than conventional elements due to its simple structure. The clutch locks or releases the rotor by use of ultrasonic levitation phenomenon. First, we have designed the structure of the ultrasonic clutch using an equation of ultrasonic levitation phenomenon, results from structural analysis and finite element (FE) analysis of piezoelectric material of the vibrator. Then we have manufactured the ultrasonic clutch and have conducted a driving experiment. Finally, we have demonstrated that the maximum levitation force is around 20 N and the static friction torque of the ultrasonic clutch is up to 0.14 Nm.

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Partial weight bearing is a generally accepted principle of rehabilitation following trauma or reconstructive surgery of the lo-wer extremity. Individual dynamic loads during partial weight bearing to a given load level of 200 N were compared in 23 patients who had sustained a fracture of the lower extremity and 11 healthy volunteers using dynamic sole pressure measurements. Excessive dynamic loading compared with the statically pre-tested 200 N level was observed in all groups. Maximum force levels were up to 690 N in young patients and up to 580 N elderly patients beyond the prescribed static load. None of the healthy volunteers was able to keep within the given load of 200 N. The set load level was exceeded by at least 38 N (119%) in the elderly patient group. In com-parison, elderly patients showed statistically significantly higher maximum forces than young patients during the first two test days (p = 0.007 and 0.013). On the 3rd test day the maximum ground contact forces were on average 71 N higher than in the young patients group. Analysis of the force time integrals (impulses transferred to the ground) displayed higher values in the older again than in young patients. The differences were statistically significant during the first two test days (p = 0.006 and 0.037). This study implies that the conventional concept of postoperative partial weight bearing starting from 200 N and a stepwise in-crease of the load level until full weight bearing is not valid during clinical practice.

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