The development of dynamic hand orthoses is a fast-growing field of research and has resulted in many different devices. A large and diverse solution space is formed by the various mechatronic components which are used in these devices. They are the result of making complex design choices within the constraints imposed by the application, the environment and the patient’s individual needs. Several review studies exist that cover the details of specific disciplines which play a part in the developmental cycle. However, a general collection of all endeavors around the world and a structured overview of the solution space which integrates these disciplines is missing. In this study, a total of 165 individual dynamic hand orthoses were collected and their mechatronic components were categorized into a framework with a signal, energy and mechanical domain. Its hierarchical structure allows it to reach out towards the different disciplines while connecting them with common properties. Additionally, available arguments behind design choices were collected and related to the trends in the solution space. As a result, a comprehensive overview of the used mechatronic components in dynamic hand orthoses is presented.

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A structured overview of trends and technologies used in dynamic hand orthoses.

This paper proposes a cable-driven parallel waist rehabilitation robot with two-level control algorithm to assist the patients with waist injuries to do some rehabilitation training. The uniqueness of the robot is that it can accurately implement the relative lateral bending, flexion, extension, and rotation of the waist on the premise of the safety. This is enabled by a mechanism design according to the motion characteristics of the human waist, and it can satisfy the need of different waist injury patients. The kinematics and dynamics of the robot are analyzed. In addition, a two-level controller is introduced to improve the accuracy of the rehabilitation training trajectory on the premise of the safety of patients and reduce the system calculation. The proportion-integration-differentiation (PID) algorithm is adopted to realize the position control in the low-level controller to ensure the accuracy of the robot. In the high-level controller, the fuzzy algorithm is used to adjust the parameters of the low-level controller according to the tension variation of cables, which ensures the patient safety and the stable operation of the robot. Finally, a prototype waist rehabilitation robot is developed for experimental calibration and performance testing. Results indicate that the designed robot system can achieve the waist rehabilitation training and the control algorithm can improve the system performance under the external disturbance.

Design and Development of a New Cable-Driven Parallel Robot for Waist Rehabilitation

In this paper, a wearable sensing glove for measuring the motion of the fingers is proposed. The system consists of linear potentiometers, flexible wires, and linear springs, which makes it compact and lightweight so that it does not interfere with the natural motion of the fingers. Inspired by the way wrinkles on finger joints are smoothed out when the finger is flexed, a flexible wire is attached to the back of each finger. As the flexible wire moves due to the motion of the finger, the joint angles are calculated by measuring the change in length of wire. Linear potentiometers with linear springs were used to maintain the tension of the wires in order to measure the wire length change consistently. Because the motion of the proximal interphalangeal (PIP) joint is dependent on that of the distal interphalangeal (DIP) joint, only two linear potentiometers were used for each finger. A compact sensing module including 10 linear potentiometers and springs was attached to a glove. The proposed system can widely be applied for the systems, which require to measure finger motions accurately, e.g., virtual reality or teleoperation systems. Such feasible applications were actually implemented and introduced in this paper.

Development of a wearable sensing glove for measuring the motion of fingers using linear potentiometers and flexible wires

Force feedback gloves have found many applications in fields such as teleoperation and virtual reality. In order to enhance the immersive feeling of interaction with remote or virtual environments, glove-like haptic devices are used, which enable users to touch and manipulate virtual objects in a more intuitive and direct way via the dexterous manipulation and sensitive perception capabilities of human hands. In this survey, we aim to identify the gaps between existing force feedback gloves and the desired ones that can provide robust and realistic sensation of the interaction with diverse virtual environments. By examining existing force feedback gloves, the pros and cons of existing design solutions to the major sub-systems including sensing, actuation, control, transmission and structure are discussed. Future research topics are put forward with design challenges being elaborated. Innovative design solutions are needed to enable the utility of wearable haptic gloves in the upcoming virtual reality era.

Toward Whole-Hand Kinesthetic Feedback: A Survey of Force Feedback Gloves

The tracking and prediction of hand and finger movements along with gesture recognition is an active subject of research due to its vast applications in many fields, such as prosthetic control and robotic telemanipulation of rehabilitation and assistive devices. The common challenge in all of these fields is developing a control interface for operating an automated assistive device in a more precise and human-like manner. In this paper, we aim to study the possibility of using a force-sensing resistors (FSRs) strap for the continuous prediction of finger movements, specifically those of the thumb and middle and index fingers. An array of 8 FSRs is used to construct a wearable band that wraps around the forearm. Ten healthy volunteers participated in this study. The subjects were asked to perform 3 representative grasping motions. The relative displacements of the tips of the thumb and middle and index fingers with respect to a reference marker placed on the hand (slightly above the wrist) was captured using a camera and colored marker system. An epsilon-based function of support vector regression with a radial basis function kernel is employed to train a regression model using the force myography (FMG) signal acquired from the forearm with the displacement of each fingertip. The results demonstrate the feasibility of using an FSR band for continuously predicting the displacement of the fingertips with an average squared correlation coefficient of 0.96 for the thumb and middle and index fingers, spanning three types of grasp.

Continuous Prediction of Finger Movements Using Force Myography

Design and control of a wearable and force-controllable hand exoskeleton system

A Dual-cable Hand Exoskeleton System for Virtual Reality

A portable and spring-guided hand exoskeleton for exercising flexion/extension of the fingers

In this paper, a wearable hand exoskeleton with force-controllable and compact actuator modules is proposed. In order to apply force feedback accurately while allowing natural finger motions, the exoskeleton linkage structure with three degrees of freedom (DOFs) was designed, which was inspired by the muscular skeletal structure of the finger. As an actuating system, a series elastic actuator (SEA) mechanism, which consisted of a small linear motor, a manually designed motor driver, a spring and potentiometers, was applied. The friction of the motor was identified and compensated for obtaining a linearized model of the actuating system. Using a LQ (linear quadratic) tuned PD (proportional and derivative) controller and a disturbance observer (DOB), the proposed actuator module could generate the desired force accurately with actual finger movements. By integrating together the proposed exoskeleton structure, actuator modules and control algorithms, a wearable hand exoskeleton with force-controllable and compact actuator modules was developed to deliver accurate force to the fingertips for flexion/extension motions.

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Design and control of a wearable hand exoskeleton with force-controllable and compact actuator modules

In this paper, design of a wearable hand exoskeleton system for exercising flexion/extension of the fingers, is proposed. The exoskeleton was designed with a simple and wearable structure to aid finger motions in 1 degree of freedom (DOF). A hand grasping experiment by fully-abled people was performed to investigate general hand flexion/extension motions and the polynomial curve of general hand motions was obtained. To customize the hand exoskeleton for the user, the polynomial curve was adjusted to the joint range of motion (ROM) of the user and the optimal design of the exoskeleton structure was obtained using the optimization algorithm. A prototype divided into two parts (one part for the thumb, the other for rest fingers) was actuated by only two linear motors for compact size and light weight.

Inseong Jo

Papers

Design and control of a wearable and force-controllable hand exoskeleton system

A Dual-cable Hand Exoskeleton System for Virtual Reality

A portable and spring-guided hand exoskeleton for exercising flexion/extension of the fingers

Design and control of a wearable hand exoskeleton with force-controllable and compact actuator modules

Design of a wearable hand exoskeleton for exercising flexion/extension of the fingers