Christian Pylatiuk

A new ultralight anthropomorphic hand

In this paper a very lightweight artificial hand is presented that approximates the manipulation abilities of a human hand very well. A large variety of different objects can be grasped reliably and the movements of the hand appear to be very natural. This five finger hand has 13 independent degrees of freedom driven by a new type of powerful small size flexible fluidic actuator. The actuators are completely integrated in the fingers which made possible the design of a very compact and lightweight hand that can either be used as a prosthetic hand or as a humanoid robot hand. A mathematical model for the expansion of a flexible fluidic actuator is given and the mechanical construction and features of the new anthropomorphic hand are illustrated.

Results of an Internet survey of myoelectric prosthetic hand users

The results of a survey of 54 persons with upper limb amputations who anonymously completed a questionnaire on an Internet homepage are presented. The survey ran for four years and the participants were divided into groups of females, males, and children. It was found that the most individuals employ their myoelectric hand prosthesis for 8 hours or more. However, the survey also revealed a high level of dissatisfaction with the weight and the grasping speed of the devices. Activities for which prostheses should be useful were stated to include handicrafts, personal hygiene, using cutlery, operation of electronic and domestic devices, and dressing/undressing. Moreover, additional functions, e.g., a force feedback system, independent movements of the thumb, the index finger, and the wrist, and a better glove material are priorities that were identified by the users as being important improvements the users would like to see in myoelectric prostheses.

Design and Evaluation of a Low-Cost Force Feedback System for Myoelectric Prosthetic Hands

Myoelectrically powered prosthetic hands lack sensory feedback relating to the force exerted by the artificial hand on a grasped object. The degree of control is imprecise, and often much more force than necessary is applied. The aim of this study was to develop and evaluate a force feedback system considering design constraints, providing the user with closed-loop control. Different methods and design criteria for providing myoelectric prosthetic hands with force feedback were analyzed, with stimulation by vibration being preferred. A new feedback system was designed, consisting of a miniature vibration motor, a piezoresistive force sensor, and control electronics. Grasping forces with and without feedback were recorded and compared from five habitual myoelectric hand users when grasping a hand dynamometer with different weights attached to it. All five patients rapidly improved their ability to regulate the grasping force without the help of vision when feedback was applied. An average force reduction of 37% was found when vibration was applied indirectly to the hand, and a decrease of 54% was found when feedback was applied directly to the skin of the residual limb. Constraints for a prosthetic force feedback system such as low power consumption, compactness, and being imperceptible to others are included in the design. General acceptance of vibration as a feedback signal was good, especially when applied indirectly. The results indicate that the new system is of potential value for myoelectric prosthetic hand users. More precise control is possible, and redundant grasping force can be diminished with a feedback system.

A comparison of the grip force distribution in natural hands and in prosthetic hands

Purpose: The aim of this study is to analyse the grip force distribution for different prosthetic hand designs and the human hand fulfilling a functional task. Method: A cylindrical object is held with a power grasp and the contact forces are measured at 20 defined positions. The distributions of contact forces in standard electric prostheses, in a experimental prosthesis with an adaptive grasp, and in human hands as a reference are analysed and compared. Additionally, the joint torques are calculated and compared. Results: Contact forces of up to 24.7 N are applied by the middle and distal phalanges of the index finger, middle finger, and thumb of standard prosthetic hands, whereas forces of up to 3.8 N are measured for human hands. The maximum contact forces measured in a prosthetic hand with an adaptive grasp are 4.7 N. The joint torques of human hands and the adaptive prosthesis are comparable. Conclusions: The analysis of grip force distribution is proposed as an additional parameter to rate the performance of different prosthetic hand designs.

A new anthropomorphic robotic hand

This paper presents the new robotic FRH-4 hand. The FRH-4 hand constitutes a new hybrid concept of an anthropomorphic five fingered hand and a three jaw robotic gripper. The hand has a humanoid appearance while maintaining the precision of a robotic gripper. Since it is actuated with flexible fluidic actuators, it exhibits an excellent power to weight ratio. These elastic actuators also ensure that the hand is safe for interacting with humans. In order to fully control the joints, it is equipped with position sensors on all of the 11 joints. The hand is also fitted with tactile sensors based on cursor navigation sensor elements, which allows it to have grasping feedback and the ability for exploration.

A hydraulically driven multifunctional prosthetic hand

In this paper a new prosthetic hand is presented that closely approximates the grasping abilities of a human hand. A large variety of different objects can be grasped reliably and the movements of the hand appear to natural. This five-finger hand has 15 degrees of freedom driven by small sized flexible fluidic actuators. The drives are within the fingers allowing a very compact and lightweight hand. Also, a concept for the control of different grasp types is presented. The characteristics of the new hand are illustrated.

Development of an anthropomorphic hand for a mobile assistive robot

In this paper the mechanism, design, and control system of a new humanoid-type hand with human-like manipulation abilities is discussed. The hand is designed for the humanoid robot which has to work autonomously or interactively in cooperation with humans. The ideal end effector for such a humanoid would be able to use the tools and objects that a person uses when working in the same environment. Therefore, a new hand is designed for anatomical consistency with the human hand. This includes the number of fingers and the placement and motion of the thumb, the proportions of the link lengths, and the shape of the palm. The hand can perform most of human grasping types. In this paper, particular attention is dedicated to measurement analysis, technical characteristics, and functionality of the hand prototype. Furthermore, first experience gained from using hand prototypes on a humanoid robot is outlined.

Development of a Multifunctional Cosmetic Prosthetic Hand

An innovative artificial hand is presented, which can help to restore both motor and sensory capabilities of upper extremity amputees. All requisite components of the revolutionary prosthesis fit into the small volume of the metacarpus. A new high-power actuating technology has been developed for maximizing the benefit in using the prosthetic hand by increasing the number of grasping patterns. An optional sensory feedback system has been designed for the prosthesis, which is based on mechanical vibration. First clinical trials with the prosthetic hand revealed a high acceptance, as the force necessary to hold an object securely was reduced significantly.

OrthoJacket: an active FES-hybrid orthosis for the paralysed upper extremity.

Abstract The loss of the grasp function in cervical spinal cord injured (SCI) patients leads to life-long dependency on caregivers and to a tremendous decrease of the quality of life. This article introduces the novel non-invasive modular hybrid neuro-orthosis OrthoJacket for the restoration of the restricted or completely lost hand and arm functions in high tetraplegic SCI individuals. The primary goal of the wearable orthosis is to improve the paralysed upper extremity function and, thus, to enhance a patients independence in activities of daily living. The system combines the advantage of orthotics in mechanically stabilising joints together with the possibilities of functional electrical stimulation for activation of paralysed muscles. In patients with limited capacity, for force generation, flexible fluidic actuators are used to support the movement. Thus, the system is not only intended for functional restoration but also for training. Several sensor systems together with an intelligent signal processing allow for automatic adaptation to the anatomical and neurological individualities of SCI patients. The integration of novel user interfaces based on residual muscle activities and detection of movement intentions by real-time data mining methods will enable the user to autonomously control the system in a natural and cooperative way.

Comparison of surface EMG monitoring electrodes for long-term use in rehabilitation device control

In this paper different types of electrodes for long-term surface EMG recording are compared to a reference electrode that is established for clinical use. The electrode materials include four different polymers with conductive load and a fabric of threads coated by a conductive layer. Different criteria are used to evaluate surface EMG recording: the signal quality, including signal-to-noise (SNR) ratio, and impedance in long-term monitoring. The aim of the study is to find an EMG electrode that allows for both silicone liner and textile integration for control of rehabilitation devices for quadriplegics with a partial residual function of the upper limb and for multifunctional prosthetic hands. Besides electrical properties, the biocompatibility and the wearing comfort have to be considered to achieve a wide acceptance by the patients. Except for one evaluated electrode, the signal quality of the four different surface electrodes is comparable to commercial Ag/AgCl gel electrodes in long-term monitoring.