With the growing aging population, there is an increasing demand and oppor-tunity to develop exoskeletons, which are typically designed for military or industrial use, to be used on a daily basis to provide power assistance. Such exoskeletons could be used by the physically impaired and injured, in addition to the elderly. This report describes the design of a power-assist exoskeleton specifically for the pronation and supination motion of the forearm. The exoskeleton is controlled by two push-button sensors to indicate the direction of rotation, which is controlled by the user at all times. As a safety precaution, visual feedback was implemented to confirm the user’s inputs were received by the exoskeleton and that the robot is actuating. A stepper motor, whose torque is transferred to the system using a bidirectional winch system, is used such that the exoskeleton is able to output such holding torques to lock the position of the arm. The mechanical structure is composed of various PVC and ABS coupling hubs, which form a stationary and rotating unit. The exoskeleton is fixed onto the user’s forearm through a blood pressure cuff, and torque is transferred from the motor to the user’s wrist through a custom-carved Styrofoam wrist cuff. From testing, the average running torque of the system ranged from 5.24 Nm to 9.17 Nm for motor speeds from 60 rpm to 45 rpm, respectively, which confirmed that decreasing motor speeds increased running torque. The amount of holding torque could not be quantified because the testing setup was unable to produce sufficient loads (>55Nm) to move the system out of its fixed position. However, when in “idle”, the system still produced a holding torque of 30 Nm, suggesting a significant source of torque transfer loss in the system. The exoskeleton was worn by a user and tested for comfort, usability and overall functionality. While there were a few sources of discomfort that were expected, the robot was able to actuate the proper motions for the user and provide powered assistance. Overall, the system was able to pronate, supinate and hold the user’s forearm as controlled, demonstrating that the exoskeleton successfully provided powered-assistance.

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Previous studies from our laboratory have demonstrated that the choice of control algorithm greatly affects how a human adapts to a robotic lower limb exoskeleton. We have shown that proportional myoelectric controllers have distinct advantages over kinematic based controllers in healthy humans. However, many neurologically impaired patients that could benefit from a robotic lower limb exoskeleton do not have sufficient muscle activation patterns for robust myoelectric control. Our long term goal is to develop an artificial neural oscillator that can provide adaptive control for robotic lower limb exoskeletons and other robotic assistive devices for human locomotion. As a first step towards this goal, we used computer simulations to assess the stability and robustness of various neural oscilla-tor algorithms coupled with dynamic systems. Due to the pendular nature of human walking mechanics, our dynamic systems included damped pendulums and a three-dimensional passive dynamic walker. We used a Hopf oscillator as our artificial neural oscillator providing neural control to the actuators. Overall results indicated that the Hopf oscillator could entrain to the resonant movement dynamics of the mechanical system with sufficient proprioceptive feedback. Our future work will examine methods to shape the timing and profile of the Hopf oscillator output to more closely mimic human muscle activation patterns. After coupling the revised Hopf oscillator to more complex dynamic walking models, we plan on testing their implementation on the robotic lower limb exoskeletons in our laboratory.

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This paper presents an approach to the development of bipedal robotic control techniques for multiple locomotion behaviors. Insight into the fundamental behaviors of human loco-motion is obtained through the examination of experimental human data for walking on flat ground, upstairs and downstairs. Specifically, it is shown that certain outputs of the human, independent of locomotion ter-rain, can be characterized by a single function, termed the extended canonical human function. Optimized functions of this form are tracked via feedback linearization in simulations of a planar robotic biped walking on flat ground, upstairs and downstairs — these three modes of locomotion are termed “motion primi-tives.” A second optimization is presented, which yields controllers that evolve the robot from one motion primitive to another — these modes of locomotion are termed “motion transitions.” A final simulation is given, which shows the controlled evolution of a robotic biped as it transitions through each mode of loco-motion over a pyramidal staircase.

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This thesis presents the preliminary work in the development of a biomimetic actuation mechanism for prosthetic and wearable robotic hand applications. This work investigates the use of novel artificial muscle technology, namely, shape memory alloys. The mechanism developed is based on the combination of compliant tendon cables and one-way shape memory alloy wires that form a set of agonist–antagonist artificial muscle pairs for the required flexion/extension or abduction/adduction of the finger joints. For the purpose of this thesis, an anthropomorphic four degree of freedom artificial testbed was developed with the same kinematic properties as the human finger. Hence, the size, appearance and kinematic architec-ture of the index finger were efficiently and practically mimicked. The biomimetic actuation scheme was implemented on the anthropomorphic artificial finger and tested, in an ad-hoc fashion, with a simple microcontroller-based pulse width modulated proportional derivation (PWD-PD) feedback controller. The tests were done to experimentally validate the performance of the actuation mechanism as emulating the natural finger’s joints movement. This thesis details the work done for the finger design process as well as the mechanisms and material used to achieve the actuation and control objectives. The results of the experiments done with the actuation platform are also presented.

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This paper presents the design, analysis, and a clinical application of a reconfigurable, parallel mechanism based, force feedback exoskeleton for the human ankle. The device can either be employed as a balance/proprioception trainer or configured to accommodate range of motion (RoM)/strengthening exercises. The exoskeleton can be utilized as a clinical measurement tool to estimate dynamic parameters of the ankle and to assess ankle joint properties in physiological and pathological conditions. Kinematic analysis and control of the device are detailed and a protocol for utilization of the exoskeleton to determine ankle impedance is discussed. The prototype of the device is also presented.

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