Technological advancements have led to the development of numerous wearable robotic devices for the physical assistance and restoration of human locomotion. While many challenges remain with respect to the mechanical design of such devices, it is at least equally challenging and important to develop strategies to control them in concert with the intentions of the user.This work reviews the state-of-the-art techniques for controlling portable active lower limb prosthetic and orthotic (P/O) devices in the context of locomotive activities of daily living (ADL), and considers how these can be interfaced with the user’s sensory-motor control system. This review underscores the practical challenges and opportunities associated with P/O control, which can be used to accelerate future developments in this field. Furthermore, this work provides a classification scheme for the comparison of the various control strategies.As a novel contribution, a general framework for the control of portable gait-assistance devices is proposed. This framework accounts for the physical and informatic interactions between the controller, the user, the environment, and the mechanical device itself. Such a treatment of P/Os – not as independent devices, but as actors within an ecosystem – is suggested to be necessary to structure the next generation of intelligent and multifunctional controllers.Each element of the proposed framework is discussed with respect to the role that it plays in the assistance of locomotion, along with how its states can be sensed as inputs to the controller. The reviewed controllers are shown to fit within different levels of a hierarchical scheme, which loosely resembles the structure and functionality of the nominal human central nervous system (CNS). Active and passive safety mechanisms are considered to be central aspects underlying all of P/O design and control, and are shown to be critical for regulatory approval of such devices for real-world use.The works discussed herein provide evidence that, while we are getting ever closer, significant challenges still exist for the development of controllers for portable powered P/O devices that can seamlessly integrate with the user’s neuromusculoskeletal system and are practical for use in locomotive ADL.

evelopment of robotic devices for gait rehabilitation of stroke patients is motivated by the need for a both intensive and task-specific training, which are key factors in recovery [1], [2], and by the need for therapist-friendly training. Evaluations of the first-generation commercial devices have shown that gait training using these devices is at least as effective as manual therapy [3], [4]. First-generation devices are characterized by the approach of enforcing gait upon a patient by rigidly moving the legs through a prescribed pattern, so that the patient can hardly influence these motions. The training effect may be extendable by increasing active participation of patients, e.g., by letting the patient walk on own effort and only offer robotic assistance as needed (AAN).The potential of AAN algorithms in promoting neural recovery has not yet been shown in gait training of humans, but it was assessed in gait training of mice [5] and in arm training of stroke patients [6], [7]. AAN strategies require interaction control [8], meaning that the apparent mechanical impedance of the device is programmable to desired values (within limits), so that the behavior of the robot can be varied from very stiff to very compliant. Compared with general haptic devices, low apparent stiffness and mass are demanded from a gait trainer, and gait motions are slow. We opted for a combination of compliant actuation and impedance control [9], [10], which provides means to minimize undesired interaction torques. This article describes and discusses the general advantages and limitations of a compliant actuation concept for rehabilitation robots on the example of our realization called the lower extremity powered exoskeleton (LOPES). The major focus is on the limitations: stiffness and bandwidth constraints as well as the influence of uncompensated exoskeleton dynamics. The stability analysis provides an interesting new result. If the rendered stiffness of an elastically actuated joint is increased beyond the intrinsic stiffness of the elastic element, stability of the coupled system human-robot cannot be guaranteed, at least not in the conservative terms of passivity. Finally, the experimental results with subjects walking with the device are presented. These results show that the limitations, in the given application, become secondary to the gain of compliant actuation. LOPES: A Low-Weight Exoskeleton with Series Elastic Actuated Joints Mechanical DesignImpedance control implies that the actuators should be high-precision force sources. Mass and inertia of the actuated construction (the exoskeleton) should be minimized, as the means to reduce the apparent mass by control are limited. Our gait rehabilitation robot LOPES is characterized by 1) the choice of degrees of freedom (DoF) that are actuated or left free to allow kinematically natural walking patterns and 2) the possibility

BackgroundStroke is the most common cause of disability in the developed world and can severely degrade walking function. Robot-driven gait therapy can provide assistance to patients during training and offers a number of advantages over other forms of therapy. These potential benefits do not, however, seem to have been fully realised as of yet in clinical practice.ObjectivesThis review determines ways in which robot-driven gait technology could be improved in order to achieve better outcomes in gait rehabilitation.MethodsThe literature on gait impairments caused by stroke is reviewed, followed by research detailing the different pathways to recovery. The outcomes of clinical trials investigating robot-driven gait therapy are then examined. Finally, an analysis of the literature focused on the technical features of the robot-based devices is presented. This review thus combines both clinical and technical aspects in order to determine the routes by which robot-driven gait therapy could be further developed.ConclusionsActive subject participation in robot-driven gait therapy is vital to many of the potential recovery pathways and is therefore an important feature of gait training. Higher levels of subject participation and challenge could be promoted through designs with a high emphasis on robotic transparency and sufficient degrees of freedom to allow other aspects of gait such as balance to be incorporated.