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In this study, we evaluate the support effect of a knee orthosis that uses the elasticity element from the perspective of human motor control. The speeds during level-ground walking and the angles during slope walking were varied during the experiments. It was observed that the support effect was remarkable at 4 km/h during the level-ground walking. In particular, at 12° during slope walking, the...
The MIT-Skywalker is a robotic device developed for the rehabilitation of gait and balance after a neurological injury. This device has been designed based on the concept of a passive walker and provides three distinct training modes: discrete movement, rhythmic movement, and balance training. In this paper, we present our efforts to evaluate the comfort of a bicycle/saddle seat design for the system's...
Robotic therapy for rehabilitation of the lower extremity is currently in its early stage of development. Aiming at exploring an efficacious intervention for gait rehabilitation, we investigate the characteristics of an end-effector gait-training device that combines saddle-seat-type body-weight-supported treadmill training with functional electrical stimulation (FES). This is a task-oriented approach...
A practical method for exploiting the neuromuscular coordination in a human arm posture to control a musculoskeletal robotic arm is proposed. The method enables the low-dimensional control of multiple muscles in the arm robot without considering the differences in the size and force balance between the human and artificial muscles. The central idea is based on the assumption that the equilibrium point...
Developing a musculoskeletal robot with multiple muscles is important for not only establishing a novel robot that achieves coordination with a human but also in understanding the framework of motor control in the human body. Our pioneering work proposed a biologically inspired control framework for multiple redundant muscles; however, very few practical results have been reported on controlling a...
Motor redundancy is a fundamental problem inherent to the inverse problem of motor planning in a muscle-activated endoskeleton such as that of a human and an anthropomorphic musculoskeletal robot. This paper proposes a biologically inspired control framework for multiple redundant muscles, based on the invariant structure in the group of agonist-antagonist coactivation. The theoretical framework explains...
This paper presents adaptive tracking control with a partial regressor for multi-joint robots. The proposed controller can abbreviate the elaborate computations of a regressor matrix, which needs to be wholly calculated in conventional adaptive control. Therefore, this controller can be easily implemented in robotic systems. Even though the proposed controller does not utilize robustification techniques...
Stroke rehabilitation requires intralimb coordination to achieve natural movement after recovery. Focusing on mechanical impedance by the coactivation of agonist muscles, we performed two experiments to assess the intralimb coordination of a post-stroke subject using two indices of the endpoint stiffness and muscle synergies. The results of the first experiment showed that the endpoint stiffness of...
This paper proposes an iterative motion learning method with stiffness adaptation for energy saving in multi-joint robots. The method iteratively updates both a desired motion and joint stiffness using time-series data of the actuator torque obtained in a control trial with the desired periodic motion. The iterative method is designed to realize the convergence of the desired motion to an energy-efficient...
This paper proposes a novel method for assessment of muscle imbalance based on muscle synergy hypothesis and equilibrium point (EP) hypothesis of motor control. We explain in detail the method for extracting muscle synergies under the concept of agonist-antagonist (AA) muscle pairs and for estimating EP trajectories and endpoint stiffness of human upper limbs in a horizontal plane using an electromyogram...
Based on the idea of synergy to explore the building blocks of movements, this study focused on the muscle space for reaching movements by human upper limbs on a horizontal plane to estimate the relationship among muscle synergies, equilibrium-point (EP) trajectories, and endpoint stiffness in two ways: (1) a novel estimation method that analyzes electromyographic signals under the concept of agonist-antagonist...
The tacit representation of muscle coordination has been a major topic of research on motor control since Bernstein's pioneering work. To unravel the mechanisms underlying voluntary movements, we investigated the electromyography signals of six muscles in a non-dominant upper limb during fast spiral movements on a horizontal plane. We considered muscle synergy to be a coordination index that we defined...
We investigated the effects of the soil moisture and gaseous environment on growth of sweet potato during its establishment period in order to confirm the hypothesis that elevated CO 2 concentrations in the root zone associated with elevated soil water contents lead to growth stagnation in sweet potato in a series of experiments. In Experiment 1 sweet potato was cultured on soil ridges irrigated...
This paper describes a novel method for controlling a human-like musculoskeletal leg robot by implementing muscle coordination in human voluntary movement. To examine human motor control involving the ill-posed problem of redundant degrees-of-freedom (DOFs), we introduce the concept of the agonist-antagonist muscle pair ratio (A-A ratio) which represents the coordination of agonist-antagonist muscle...
This paper presents a variable-stiffness knee exoskeleton to enhance human walking. The developed exoskeleton is an agonist-antagonist system with pneumatic artificial muscles (PAMs), and its equilibrium-joint angle and joint stiffness are separately controlled using on our concepts of the agonist-antagonist muscle-pair ratio (A-A ratio) and agonist-antagonist muscle-pair activity (A-A activity)....
This paper presents an electromyographic-based human-machine interface for the agonist-antagonist system with two pairs of pneumatic artificial muscles (PAMs) that replicates the human elbow-joint system. We introduce the novel concepts of agonist-antagonist muscle-pair ratio (A-A ratio) and agonist-antagonist muscle-pair activity (A-A activity) to link the human muscle system to the PAM system, and...
This paper presents a novel method for controlling a single-joint robot arm driven by two pneumatic artificial muscles (PAMs). We introduce the concepts of the agonist-antagonist muscle-pairs ratio (A-A ratio) and the agonist-antagonist muscle-pairs activity (A-A activity), and demonstrate that our concepts enable separate linear control of the equilibrium joint angle and joint stiffness. We also...
The study of decomposition of body movement into motor primitives is evolving in neuroscience. Meanwhile, in robotics, the motor control of human-like musculoskeletal robots is difficult due to redundant degrees of freedom (DOF) of the robot body. The application of the concept of decomposing into units of motor function to robotics is anticipated to render the control of the robot low-dimensional...
The study of decomposition of body movement into motor primitives is evolving in neuroscience. Meanwhile, in robotics, the motor control of human-like musculoskeletal robots is difficult due to redundant degrees of freedom (DOF) of the robot body. The application of the concept of decomposing into units of motor function to robotics is anticipated to render the control of the robot low-dimensional...
The need of solving the problem of multi-degrees-of-freedom in motor control is increasing as human-like robots become more popular these days. Muscle synergies hypothesis is a prominent suggestion for this problem. In this paper, we investigated the muscle synergies extracted from human subjects in a producing-force task to explore the mechanism of the human's skillful hand-movement at producing...
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