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. / Master of Science / This thesis is centered upon the published A Novel Method and Exoskeletons for Whole-arm Gravity Compensation (Turner, Hull 2020), includes a new way to lift a person's arm or robotic linkage. The design can lift weights close to the hand regardless of arm placement. This support is provided with a pantograph. The pantograph design is based on a mirrored, smaller copy of the upper-arm and forearm bars, which is pulled downwards to create an upwards support force at chosen support point. This point is based underneath the forearm or at a heavy tool. The concept is similar to pushing down on a teeter-totter in order to prevent the other end from dropping. Two exoskeletons, using different linkages make use of this pantograph design. The Panto-Arm Exo is slim and light. It is made to help users in lift their arm by supporting its weight. The Panto-Tool Exo has a support point that located where a mass representing a heavy tool sits. The changes between both devices means that they display different lifting qualities. The Panto-Arm Exo was worn by 14 people, also wearing electrodes that measured muscle activation. These users held weights and moved their arms around while muscle activation was recorded. While the Panto-Arm Exo wasn't fine-tuned or adjusted for individual people, it was shown to reduce muscle activation in the measured upper-arm muscles for some of the arm placements.

An underactuated exoskeleton design for walking assistance is presented and evaluated. The exoskeleton uses one motor per leg and makes use of a pantograph to reduce the overall profile and allow the exoskeleton to closely follow the shape of the user's leg. Support is provided between the ball of the user's foot and their waist by compressing a spring in parallel with the user's leg during Stance Phase. The exoskeleton has a mass of 14.0 kg (30.8 lbs) and was tested up to a supplied spring force of 323.6 N (72.75 lbf) which equates to around 161.8 N (36.38 lbf) of assistive force at the waist. Range of motion tests showed minimal restriction at the knee and ankle, but some restriction of the hip. Human subject experiments using a simple gait detection method based on GRF at walking speeds from 0.45 m/s to 1.12 m/s (1.0 mph to 2.5 mph) were performed and showed an increase in the time between actual heel strike and predicted heel strike of approximately 0.05 seconds to 0.1 seconds. Lastly, calculations are presented examining the effect of exoskeleton assistance on the biological joint moments and optimizing the actuator design to reduce power consumption. The actual performance of the exoskeleton is compared with the calculations based on the joint angles during a typical walking cycle. / Master of Science / A design for an exoskeleton capable of providing walking assistance without requiring a motor for every joint is presented and evaluated. The exoskeleton uses one motor per leg and makes use of a pantograph to reduce the required size and allow the exoskeleton to closely follow the shape of the user's leg. Support is provided between the ball of the user's foot and their waist by compressing a spring attached beside the user's leg while the user's foot is on the ground. The exoskeleton weighs 14.0 kg (30.8 lbs) and was tested up to a supplied spring force of 323.6 N (72.75 lbf) which equates to around 161.8 N (36.38 lbf) of assistive force at the waist. Range of motion tests showed minimal restriction at the knee and ankle, but some at the hip. Testing with a human participant using a simple method for determining when to apply support and remove it based on the forces measured at the user's foot were performed at walking speeds of 0.45 m/s to 1.12 m/s (1.0 mph to 2.5 mph). These tests showed an increase in the time between when the heel of the foot initially hits the ground and when the exoskeleton code determined that it occurred of approximately 0.05 seconds to 0.1 seconds. Lastly, calculations are presented examining how exoskeleton assistance affects what is felt at the joints of the user and determining what spring stiffness would best reduce the power required from the motors. The actual performance of the exoskeleton is compared with the calculations based on the joint angles during normal human walking.

Multi-pantograph operation allows several short electric multiple unit (EMU) trainsets to be coupled or decoupled to adapt to daily or seasonal passenger-flow variation. Although this is a convenient and efficient way to operate rolling stock and use railway infrastructure, pantographs significantly influence each other and even significantly change the dynamic behaviour of the system compared to single-pantograph operation in the same condition. The multi-pantograph system is more sensitive and vulnerable than the single-pantograph system, especially at high operational speeds or with pantographs spaced at short distances. Heavy oscillation in the system can result in low quality of current collection, electromagnetic interference, severe wear on the contact surfaces or even structural damage. The mechanical interaction between the pantograph and the catenary is one of the key issues which limits the maximum operational speed and decides the maintenance cost.     Many researchers have paid a lot of attention to the single-pantograph operation and have made great progress on system modelling, optimizing, parameter studies and active control. However, how the pantographs in a train configuration affect each other in multi-pantograph operation and which factors limit the number of pantographs is not fully investigated. Nowadays, to avoid risking operational safety, there are strict regulations to limit the maximum operational speed, the maximum number of pantographs in use, and the minimum spacing distance between pantographs. With the trend of high-speed railways, there are huge demands on increasing operational speed and shortening spacing distance between pantographs. Furthermore, it is desirable to explore more practical and budget-saving methods to achieve higher speed on existing lines without significant technical modification.     In addition to a literature survey of the dynamics of pantograph-catenary systems, this thesis carries out a numerical study on multi-pantograph operation based on a three-dimensional pantograph-catenary finite element (FE) model. In this study, the relationship between dynamic performance and other parameters, i.e. the number of pantographs in use, running speed and the position of the pantographs, are investigated. The results show that the spacing distance between pantographs is the most critical factor and the trailing pantograph does not always suffer from deterioration of the dynamic performance. By discussing the two-pantograph operation at short spacing distances, it is found that a properly excited catenary caused by the leading pantograph and the wave interference between pantographs can contribute to an improvement on the trailing pantograph performance. To avoid the additional wear caused by poor dynamic performance on the leading pantograph and achieve further improvement at high speeds, it is suggested to use the leading pantograph as an auxiliary pantograph, which does not conduct any electric current and optimize the uplift force on the leading pantograph. After a brief discussion on some system parameter deviations, it is shown that a 30% of speed increase should be possible to achieve while still sustaining a good dynamic performance without large modifications on the existing catenary system. / <p>QC 20150928</p>

In the field of MEMS technology, all kinds of actuators are often regarded as the force source. However, some designs of actuators have good precision in position; the working distance to be driven is too short. Therefore, the actuator is often combined with a mechanism with displacement amplify function. The objective of this study is to synthesize the new pantograph mechanism using the concept of mechanism design according to the desirable motion and the requirement of the actuator. The cases of single degree-of-freedom and two degree-of-freedom are assumed simultaneously for the output of the basic design constraints so as to generate new pantograph mechanisms from the catalogue of kinematic chains. The suitable pantographs are then found out with the features such as: (1) single level plane using comb driver, (2) using compliant mechanisms as joints, and (3) suitable for MUMPs process. These constraints of design are considered as the procedures of process design, compliant mechanisms transformation, compliant joints design, actuator configurations design, FEM dynamic analysis and joint modifications. Finally, prototypes are evaluated and transform into planar micro compliant pantographs. Moreover, a test and a discussion of the displacement error are done under the consideration of the designed mechanism actuating using FEM analysis. The percentage of displacement error of planar micro compliant pantograph is defined, and the equation for estimating the percentage of displacement error is proposed so as to modify the motion error for controlling.

Thesis (M.S.)--University of Michigan, 1983.

Thesis (M.S.)--University of Michigan, 1983.

Thesis (M.S.)--University of Michigan, 1979.

Thesis (M.S.)--University of Michigan, 1983.

Thesis (M.S.)--University of Michigan, 1979.

Thesis (M.S.)--University of Michigan, 1983.