Mobility impairments, particularly those caused by stroke-induced hemiparesis, significantly impact independence and quality of life. Current smart walker controllers operate by using input forces from the user to control linear motion and input torques to dictate rotational movement; however, because they predominantly rely on user-applied torque exerted on the device handle as an indicator of user intent to turn, they fail to adequately accommodate users with unilateral upper limb impairments. This leads to increased physical strain and cognitive load. This paper introduces a novel smart walker equipped with a fuzzy control algorithm that leverages shoulder abduction angles to intuitively interpret user intentions using just one functional hand. By integrating a force sensor and stereo camera, the system enhances walker responsiveness and usability. Experimental evaluations with five participants showed that the fuzzy controller outperformed the traditional admittance controller, reducing wrist torque while using the right hand to operate the walker by 12.65 % for left turns, 80.36 % for straight paths, and 81.16 % for right turns. Additionally, average user comfort ratings on a Likert scale increased from 1 to 4. Results confirmed a strong correlation between shoulder abduction angles and directional intent, with users reporting decreased effort and enhanced ease of use. This study contributes to assistive robotics by providing an adaptable control mechanism for smart walkers, suggesting a pathway towards enhancing mobility and independence for individuals with mobility impairments. Project page: https://tbs-ualberta.github.io/fuzzy-sw/

Gait asymmetry, a consequence of various neurological or physical conditions such as aging and stroke, detrimentally impacts bipedal locomotion, causing biomechanical alterations, increasing the risk of falls and reducing quality of life. Addressing this critical issue, this paper introduces a novel diagnostic method for gait symmetry analysis through the use of an assistive robotic Smart Walker equipped with an innovative asymmetry detection scheme. This method analyzes sensor measurements capturing the interaction torque between user and walker. By applying a seasonal-trend decomposition tool, we isolate gait-specific patterns within these data, allowing for the estimation of stride durations and calculation of a symmetry index. Through experiments involving 5 experimenters, we demonstrate the Smart Walker’s capability in detecting and quantifying gait asymmetry by achieving an accuracy of 84.9% in identifying asymmetric cases in a controlled testing environment. Further analysis explores the classification of these asymmetries based on their underlying causes, providing valuable insights for gait assessment. The results underscore the potential of the device as a precise, ready-to-use monitoring tool for personalized rehabilitation, facilitating targeted interventions for enhanced patient outcomes.

This paper introduces a novel hybrid torque allocation method for improving wearability and mobility in integrated functional electrical stimulation (FES) of the quadriceps muscles and powered exoskeleton systems. Our proposed approach leverages a hierarchical closed-loop controller for knee joint position tracking while addressing limitations of powered exoskeletons and FES systems by reducing power consumption and battery size and by mitigating FES-induced muscle fatigue, respectively. The core component is a model-free optimization algorithm that dynamically distributes torque between FES and the exoskeleton by considering tracking error, effort, and the prediction of muscle fatigue in the cost function, computing allocation gain in an online manner. The online optimization approach interactively changes the optimal allocation gain by taking into account the instantaneous value of error and effort and also penalizing FES-induced fatigue, a common challenge in long-duration experiments. The results demonstrate that this dynamic allocation significantly improves system wearability by reducing power consumption without increasing muscle fatigue during the extension phase of walking. This hybrid control approach contributes to improving exoskeleton wearability and rehabilitation outcomes for individuals with SCI and mobility impairments, enhancing assistive technology and quality of life.

This paper introduces intelligent central pattern generators (iCPGs) that can plan personalized walking trajectories for lower-limb exoskeletons. This can make walking more comfortable for the users by resolving one of the significant shortcomings of most commercially available exoskeletons, which is the use of pre-defined fixed trajectories for all users. The proposed method combines reinforcement learning (RL) with previously introduced adaptable central pattern generators (ACPGs) to learn a user's physical interaction behaviour and refine the exoskeleton's walking trajectories. The ACPG method embeds physical human-robot interaction (pHRI) in CPGs to make changing gait trajectories in real-time, possible. However, to effectively refine gait trajectories based on pHRIs, the parameters must be precisely identified and updated as a user interacts with the exoskeleton. Our proposed method uses RL to modify (amplify/attenuate) the pHRI energy based on a user's interaction behaviour, and form an effective energy value which can facilitate reaching desired gait pattern for users via iCPG dynamics. The proposed method can resolve the aforementioned challenges with ACPGs and personalized trajectory generation. The simulation and experimental results provide evidence that the proposed method can effectively adapt to the user's behaviour in different walking scenarios with the Indego lower-limb exoskeleton.

In this survey, various concepts and methodologies developed over the past two decades for varying and learning the impedance or admittance of robotic systems that physically interact with humans are explored. For this purpose, the assumptions and mathematical formulations for the online adjustment of impedance models and controllers for physical human-robot interaction (HRI) are categorized and compared. In this systematic review, studies on: 1) variation and 2) learning of appropriate impedance elements are taken into account. These strategies are classified and described in terms of their objectives, points of view (approaches), and signal requirements (including position, HRI force, and electromyography activity). Different methods involving linear/nonlinear analyses (e.g., optimal control design and nonlinear Lyapunov-based stability guarantee) and the Gaussian approximation algorithms (e.g., Gaussian mixture model-based and dynamic movement primitives-based strategies) are reviewed. Current challenges and research trends in physical HRI are finally discussed.

Human-robot collaboration (HRC) significantly extends robotic systems’ applications when working in spaces like houses, hospitals, or laboratories. However, new challenges appear during a close collaboration between humans and robots and imitating the movement of humans by robots. Learning from demonstration (LfD), or kinesthetic teaching, is a popular approach to help teach a robot human behavior by demonstrations without the need to explicitly reprogram the robot for different procedures. In this paper, we propose a method for object manipulation, including lifting, carrying, and lowering the object through a collaboration of a human with a wheeled mobile manipulator (WMM). The WMM is first trained with the help of a human demonstrator to collaborate with the user to execute the task. Then, the WMM will independently cooperate with the user by reproducing the learned skills to perform the same task. The redundancy of the WMM will also be employed to enhance its force exertion capability in the vertical direction to offset the object’s weight. The advantages and effectiveness of the proposed method are investigated through experiments.

We develop an adaptive active contour tracing algorithm for extraction of spinal cord from MRI that is fully automatic, unlike existing approaches that need manually chosen seeds. We can accurately extract the target spinal cord and construct the volume of interest to provide visual guidance for strategic rehabilitation surgery planning.