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Objective: Recently, human joint impedance—the instantaneous mechanical response to a perturbation—has been quantified during gait, providing new insight beyond the traditional biomechanical descriptions of kinetics and kinematics. However, the role of joint impedance in neuromotor control and the development of exoskeletons and other wearable robotic systems remains unknown. One approach to studying...
The design employs direct drive torque motor to achieve a robot single joint with active compliance based on the impedance model. In order to maximize the torque density, transmission transparency and backdrivability, the joint employs a quasi-direct actuator that a single-stage planetary gear is mounted on the motor's rotor. When robot interacts with environments, it's inevitable to change the stiffness...
In this paper, we propose the novel gait trajectory adaptation method applicable to an exoskeleton for strength augmentation. The proposed method consists of the online positive feedback trajectory adaptation method and the swing phase duration adaptation method. The swing test results of an exoskeleton prototype showed that the proposed method is more adaptable to the change of the trajectory amplitude...
For the purpose of enhancing compliance of robot joint, an impedance control strategy with new inner torque controller is proposed. Apparent inertia of the motor can be scaled down thanks to this new type of torque controller. Effects of different position (motor-side position θ and link-side position q) feedback strategies are explored through theoretical deviation, simulation and static stiffness...
This paper describes the methods and experiment protocols for estimation of the human ankle impedance during turning and straight line walking. The ankle impedance of two human subjects during the stance phase of walking in both dorsiflexion plantarflexion (DP) and inversion eversion (IE) were estimated. The impedance was estimated about 8 axes of rotations of the human ankle combining different amounts...
Powered exoskeletons can facilitate rehabilitation of patients with upper limb disabilities. Designs using rotary motors usually result in bulky exoskeletons to reduce the problem of moving inertia. This paper presents a new linearly actuated elbow exoskeleton that consists of a slider crank mechanism and a linear motor. The linear motor is placed beside the upper arm and closer to shoulder joint...
This paper presents the result of the research about designing a device to support ankle joint by using Series Elastic Actuator (SEA). SEA is a system which consist of a DC motor, ball screw and the springs. The output force is controlled to track a trajectory which has been built before. Control force is done through control the transpose of the spring. A prototype was built to verify the possibility...
The tension control of wires can benefit from Series Elastic Actuator (SEA), which is a potential emerging actuator system. In this paper, it is verified that the tension of wires can be successfully controlled by a novel SEA, called Compact Planetary-geared Elastic Actuator (cPEA), which incorporates a planetary gear and a spring to achieve precise force sensing and compactness at the same time....
There has been consistent trials to make a hydraulic actuator to be effective in interactive robot applications that require high power and durability. However, conventional strategies to obtain this goal, such as force/torque servo control or adding elastic components, suffer from complexity, sensor problems, and reduced system robustness. In this paper, we show that introducing backdrivability to...
In this paper the concept of a unified torque/impedance controller is applied to a pneumatically actuated, antagonistic robot joint. The investigated control algorithm consists of a cascaded structure in which the outer torque/impedance controller commands a desired torque to two cylinder-based force controllers. The torque-/impedance controller is equipped with a virtual tank that ensures passivity...
This paper, for the first time, describes the estimation of the time-varying impedance of the human ankle in the sagittal (SP) and frontal (FP) planes during the stance phase of walking. The result of this work is aimed to provide design parameters for the development of 2-DOF powered ankle-foot prostheses capable of mimicking the time-varying impedance of the human ankle. Sixteen axes of rotations...
There are wide verities of human movement possible that involves a range from the gait of the physically handicapped, the lifting of a load by a factory worker to the performance of a superior athlete. Output of the movement can be described by a large number of kinematic variables. Modeling each case with a muscle model is difficult. Intended action data can also be extracted from surface Electromyography...
Interaction control is a mature, but still, current area of research in robotics. Various approaches have been developed for passive and active force regulation and tracking, e.g. impedance control, direct force and hybrid force-position control. The latter method implements a force feedback outer loop on top of a position controller inner loop, where commands are issued with respect to a compliant...
Suturing is a challenging and highly dexterous task in minimally invasive surgery, even with the assistance of robotic surgical systems. In this work, we propose a simple yet versatile impedance virtual fixture framework, which can be applied on the master manipulator in a tele-operated robotic surgical system. With this framework, we further develop two types of virtual fixtures that assist with...
This paper proposes a robotics therapeutic massage evaluation system using electroencephalogram (EEG) signal analysis approach. An anthropomorphic dual arm robot is developed in this work for massage application. Compare to other massage systems, our dual arm robot can provides diversified massage techniques through the impedance control of both Cartesian space and joint space. In order to evaluate...
Impedance control offers a theoretical basis for safe interaction between a robot and the environment, but model uncertainty, disturbances and actuation dynamics can compromise the accuracy of the rendered impedance in implementation. If both the interactive force and motion are directly sensed, the relationship between them can be robustly regulated to present the desired impedance dynamics. In this...
Ankle joint dynamics properties have been widely studied because of their important role in interaction with environment. In this paper, these properties were studied under the experimental condition of push-recovery. The disturbance was exerted on backs of subjects. The amplitude of disturbance was limited so that only ankle joint strategy was evoked, without foot tilting. A data-synchronized-collection...
In order to make full use of the ability of the low impact docking mechanism to reduce the contact force in the docking process, the impedance control strategy is designed. And then a kind of parameter adjusting flow is proposed for the impedance controller based on the influence rules of the target impedance. To perform a low impact docking mission unaware of the initial position error and orientation...
In this paper, a new impedance control method based on pressure distribution for wearable assist robot on multi-joint part is proposed. Generally, assist robots were designed based on assisting for a simple joint body part of the user such as elbow, knee, limb and so on. These robots can be similar structure to the assisted body part, and they can follow the user's movements. On the other hand, it...
In this paper, a novel upper limb rehabilitation robot is introduced which is based on cable-driven mechanism. The research focuses on developing a specific cable actuator that brings back-drivability characteristic for the rehabilitation robot. The main idea based on using a series of cables with single tension motor as power supply to control motion of multi-joint arm. Dynamic specification of two-joint...
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