An ankle robot for a modular gait rehabilitation system

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (p. 111-112).Patients with neurological disorders, such as stroke survivors, can be treated with physical rehabilitation to regain motor control and function. Conventional therapy techniques are labor intensive and non-standardized. This is especially true in gait rehabilitation. The robotic therapy paradigm developed in the Newman Lab for Hu- man Rehabilitation uses low impedance robots, such as the MIT-MANUS, to provide assistive therapy in a repeatable and measurable fashion. A system is now being designed to assist gait rehabilitation using a series of lower extremity and pelvis robots that can be used together or independently. The focus of this document is ankle rehabilitation. Ankle function is typically not targeted in conventional or other robotic therapy systems. The result is often that the patient is required to wear a brace or orthosis after therapy. The proposed module allows all normal ankle movements and is capable of driving the two most important movements in gait, dorsi/plantar flexion and inversion/eversion. It is designed to provide sufficient force to position the foot in swing phase while still being as lightweight and backdriveable as possible. The kinematics consist of two parallel two-link mechanisms. The robot is driven by two DC brushless motors with planetary gearheads to amplify the torque output.by Jason W. Wheeler.S.M

Review of control strategies for robotic movement training after neurologic injury

There is increasing interest in using robotic devices to assist in movement training following neurologic injuries such as stroke and spinal cord injury. This paper reviews control strategies for robotic therapy devices. Several categories of strategies have been proposed, including, assistive, challenge-based, haptic simulation, and coaching. The greatest amount of work has been done on developing assistive strategies, and thus the majority of this review summarizes techniques for implementing assistive strategies, including impedance-, counterbalance-, and EMG- based controllers, as well as adaptive controllers that modify control parameters based on ongoing participant performance. Clinical evidence regarding the relative effectiveness of different types of robotic therapy controllers is limited, but there is initial evidence that some control strategies are more effective than others. It is also now apparent there may be mechanisms by which some robotic control approaches might actually decrease the recovery possible with comparable, non-robotic forms of training. In future research, there is a need for head-to-head comparison of control algorithms in randomized, controlled clinical trials, and for improved models of human motor recovery to provide a more rational framework for designing robotic therapy control strategies

Characterization and analysis of an MRI compatible robot design for wrist psychophysics and rehabilitation

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (leaves 110-112).The MIT Wrist Robot has demonstrated the effectiveness of robotic therapy in aiding the rehabilitation of stroke victims. In order to investigate the neurological processes involved in this therapy and evaluate its effectiveness a patented MRI compatible version of the wrist robot is being developed, so that therapy and brain imaging may be carried out simultaneously. Patient actuation is accomplished with two standard electric motors, located outside the MRI chamber, which drive a non-ferrous, MRI compatible, low impedance hydraulic fluid transmission, consisting of two pairs of custom designed and fabricated vane motors. This thesis details the characterization and redesign of this robot, with emphasis placed upon the hydraulic system.Nevan Clancy Hanumara.S.M

serial and parallel robotics: energy saving systems and rehabilitation devices

This thesis focuses on the design and discussion of robotic devices and their applications. Robotics is the branch of technology that deals with the design, construction, operation, and application of robots as well as computer systems for their control, sensory feedback, and information processing [1]. Nowadays, robotics has been an unprecedented increase in applications of industry, military, health, domestic service, exploration, commerce, etc. Different applications require robots with different structures and different functions. Robotics normally includes serial and parallel structures. To have contribution to two kinds of structures, this thesis consisting of two sections is devoted to the design and development of serial and parallel robotic structures, focused on applications in the two different fields: industry and health

Analysis of walking and balancing models actuated and controlled by ankles

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (p. 181-182).Experimental data show that ankle torque is the most important actuator in normal human locomotion. I investigate the dynamics of simple models actuated by ankles alone. To assess the contribution of ankle actuation to locomotion, I first analyze the dynamics of some passive walkers without any joint torque. These passive walkers include a rimless wheel model and springy-legged models with and without a double stance phase. I analyze the stability of the period-one gait of each passive walker to compare it with the stability of the period-one gait of an ankle actuated model. Subsequently, I investigate whether balancing of a double inverted pendulum model whose shape and mass distribution are similar to a human can be achieved by control of ankle torque in a frontal plane. I study the dynamics of the model and design a controller that makes the model balance with biologically realistic ankle torque and a reasonable foot-floor friction coefficient. I conclude that an ankle-actuated model can make a stable period-one gait in a sagittal plane. Also, I deduce that the ankle torque control in a frontal plane can stabilize a double inverted pendulum model whose shape and mechanical properties are similar to those of humans.by Jooeun Ahn.S.M

A robot for gait rehabilitation

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (p. 216-220).After a stroke, persons suffer from neurological impairments that affect gait, and so require rehabilitation to regain ambulatory function. While 82% of patients recover the ability to walk, current methods including physiotherapy and partial body-weight supported treadmill training (PBWSTT) are monotonous and require intense therapist effort. The Mechanized Gait Trainer and the LOKOMAT are two robotic devices that have been developed to improve gait rehabilitation, but neither provides the facilitation of pelvis movements afforded by traditional methods. In addition, neither device is truly backdrivable. As shown by Hogan and Krebs, backdrivable, impedance-controlled robots are ideal for rehabilitation because of their stable interaction properties. Robots for the arm/shoulder, wrist, ankle, and hand have already been developed. This thesis describes the design of a robot for gait rehabilitation through the facilitation of pelvis movements. Four degrees of freedom (DOF) are actuated: vertical, lateral, and frontal translations as well as the rotation about the vertical axis. Vertical forces support part of the patient's weight. Lateral forces assist the weight shift from stance leg to swing leg and are a part of physiotherapy and treadmill training.(cont.) Frontal forces help pace the subject as on a treadmill. Pelvic rotations can impart energy into the swing leg without direct actuation of the hip and knee muscles. A four DOF mechanism was designed to control these movements, consisting of a three-DOF planar linkage with a vertical prismatic translation. A mockup of the configuration was designed and tested to show that the non-actuated pelvis DOFs are not adversely affected by the device. Design calculations include finding the optimal linkage configuration, selecting ballspline shafts for the vertical DOF, selecting actuators, and designing the robot arm cross-sections and joints. A final design for the four-DOF module is presented.by Michael H. Roberts.S.M

Stable, high-force, low-impedance robotic actuators for human-interactive machines

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (p. 347-359).Robots that engage in significant physical interaction with humans, such as robotic physical therapy aids, must exhibit desired mechanical endpoint impedance while simultaneously producing large forces. In most practical robot configurations, this requires actuators with high force-to-weight ratios and low intrinsic impedance. This thesis explores several approaches to improve the tradeoff between actuator force capacity, weight, and ability to produce desired impedance. Existing actuators that render impedance accurately generally have poor force densities while those with high force densities often have high intrinsic impedance. Aggressive force feedback can reduce apparent endpoint impedance, but compromises coupled stability. The common standard for ensuring coupled stability, passivity, can limit performance severely. An alternative measure of coupled stability is proposed that uses limited knowledge of environment dynamics (e.g. a human limb) and applies robust stability tools to port functions. Because of structural differences between interaction control and servo control, classical single-input, single-output control tools cannot be directly applied for design. Instead, a search method is used to select controller parameters for an assumed structure.(cont.) Simulations and experiments show that this new approach can be used to design a force-feedback controller for a robot actuator that improves performance, reduces conservatism, and maintains coupled stability. Adding dynamics in series to change an actuator's physical behavior can also improve performance. The design tools developed for controller design are adapted to select parameters for physical series dynamics and the control system simultaneously. This design procedure is applied to both spring-damper and inertial series dynamics. Results show that both structures can be advantageous, and that the systematic design of hardware and control together can improve performance dramatically over prior work. A remote transmission design is proposed to reduce actuator weight directly. This design uses a stationary direct-drive electromagnetic actuator and a passive, flexible hydraulic transmission with low intrinsic impedance, thereby utilizing the impedance- rendering capabilities of direct-drive actuation and the force density of hydraulic actuation. The design, construction and characterization of a low-weight, low-friction prototype for a human arm therapy robot are discussed. Recommendations and tradeoffs are presented.by Stephen Paul Buerger.Ph.D