O. Christ

Active lower limb prosthetics: a systematic review of design issues and solutions

This paper presents a review on design issues and solutions found in active lower limb prostheses. This review is based on a systematic literature search with a methodical search strategy. The search was carried out across four major technical databases and the retrieved records were screened for their relevance. A total of 21 different active prostheses, including 8 above-knee, 9 below-knee and 4 combined knee-ankle prostheses were identified. While an active prosthesis may help to restore the functional performance of an amputee, the requirements regarding the actuation unit as well as for the control system are high and the development becomes a challenging task. Regarding mechanical design and the actuation unit high force/torque delivery, high efficiency, low size and low weight are conflicting goals. The actuation principle and variable impedance actuators are discussed. The control system is paramount for a “natural functioning” of the prosthesis. The control system has to enable locomotion and should react to the amputee’s intent. For this, multi-level control approaches are reviewed.

Design and control of a robot for the assessment of psychological factors in prosthetic development

This paper introduces a robotic concept for the assessment of psychological factors in prosthetic design. Its aim is to imitate the postural movements of the participants while those are conducting squatting movements in order to investigate the integration of artificial limbs to the subjects body scheme. Therefore, the robot mimics the functionality and appearance of the human foot, shank and thigh as well as the ankle and knee joint. To induce a more realistic outer appearance, the hull of a shop-window mannequin is used as cladding. The robot is controlled by a computed torque control combined with a RGB-D sensor for the acquisition of the desired trajectories from the participant. In the test setup one leg of the participant is hidden from his view while the robot stands next to him and imitates the movements of this leg. This paper gives an insight in the theory of body schema integration. The concept of the robot is described and detailed information about the mechanical design and actuator dimensioning in accordance with psychological and biomechanical requirements are given. Furthermore, the concept of the human-machine interface, the control algorithm and simulations based on experimental data from a human subject are presented.

Prosthesis-User-in-the-Loop: A user-specific biomechanical modeling and simulation environment

In this paper, a novel biomechanical modeling and simulation environment with an emphasis on user-specific customization is presented. A modular modeling approach for multi-body systems allows a flexible extension by specific biomechanical modeling elements and enables an efficient application in dynamic simulation and optimization problems. A functional distribution of model description and model parameter data in combination with standardized interfaces enables a simple and reliable replacement or modification of specific functional components. The user-specific customization comprises the identification of anthropometric model parameters as well as the generation of a virtual three-dimensional character. The modeling and simulation environment is associated with Prosthesis-User-in-the-Loop, a hardware simulator concept for the design and optimization of lower limb prosthetic devices based on user experience and assessment. For a demonstration of the flexibility and capability of the modeling and simulation environment, an exemplary application in context of the hardware simulator is given.

The influence of Antonovsky’s sense of coherence (SOC) and psychoeducational family intervention (PEFI) on schizophrenic outpatients’ perceived quality of life: a longitudinal field study

BackgroundAntonovsky’s sense of coherence (SOC) as well as psychoeducational interventions has a convincing impact on the quality of life (QOL) of patients suffering from schizophrenia. This study explores the influence of SOC on QOL among participants of a PEFI group (PG) compared to a control group (CG).MethodsIn a quasi-experimental field study 46 schizophrenic outpatients had an option to participate together with their family members the PG (n = 25) or the CG (n = 21). They were assessed amongst others with the Quality of Life Questionnaire (WHOQOL-BREF), the Global Assessment of Functioning Scale (GAF), the Positive and Negative Syndrome Scale (PANSS) and the Sense of Coherence Scale (SOC-29). The efficacy of the PG on QOL was compared to the CG within two different SOC levels.ResultsBefore intervention patients with high SOC scores had significant higher levels in GAF and QOL and a trend of lower PANSS scores. The strongest relationship was found between SOC and QOL. Regarding the SOC level after intervention PG participants had higher QOL values than the CG within the last three measurements. The highest benefit due to QOL was observed within PG participants with high SOC scores.ConclusionsThe results of the study suggest that SOC is a good predictive variable for clinical outcomes including QOL. Generally, the influence of the SOC level on QOL was stronger than the effect of PEFI. Hence schizophrenic patients with high SOC scores did benefit most from participating in a PG regarding their QOL. To optimize the effect of PEFI more efforts are needed to enhance the SOC of the participants. Altogether PEFI seems to be an important completion to the standard treatment for schizophrenic outpatients.

The rubber hand illusion: Maintaining factors and a new perspective in rehabilitation and biomedical engineering?

Feelings of unrealistic body parts are related to deficits in human information processing and can occur as a part of phan, tom sensations after amputation [8]. Experimentally induced sensoric illusions like rubber hand illusion (RHI) [1] may help to understand basic information processing and could give new ideas for treatment or the rehabilitation pro, cess. Factors that are related to modulate sensoric illusions during movement may help to develop new intervention strategies in the rehabilitation of illusory symptoms. The goal of this study was to review the factors affecting persis, tence of the RHI effect during movement. We selected 13 keywords and searched in the following www.dimdi.de data bases (CCTR93, CDAR94, CDSR93, DAHTA, DAHTA, EA08, ED93, EM00, EM47, HG05, KP05, KR03, ME00, ME60, PI67, PY81, TV01, TVPP). A total of 160 articles were found. Duplicates were removed and the remaining list was filtered with the objective to explore the influence of active or passive movement during experimentally induced RHI. Then we identified six articles which experimentally examined persistence of RHI during active or passive move, ments. Results indicate that RHI are maintained during active or passive movements due to visual and temporal congru, ency. During active movements the RHI is more stable or global than in passive movements or during tactile stimulation. Factores like visual and temporal congruency are related to maintain RHI and are discussed in the rehabilitation of phan, tom sensations regarding new innovations in the design of prosthetics

P-224 - Persistence of the rubber hand illusion and maintaining factors during active or passive movements: new indicators for rehabilitation?

Introduction Feelings of unrealistic body parts are related to deficits in human information processing and can occur as a part of schizophrenic disorders or phantom sensations after amputation (Koide, 2008; Goller, in press). Experimentally induced sensoric illusions like rubber hand illusion (RHI) (Botvinik & Cohen, 1998) may help to understand basic information processing and could give new ideas for treatment or the rehabilitation process. Objectives Factors that are related to modulate sensoric illusions during movement may help to develop new intervention strategies in the rehabilitation of illusory symptoms. Aims The goal of this study was to review the factors affecting persistence of the RHI effect during movement. Methods We selected 13 keywords and searched in the following www.dimdi.de data bases (CCTR93, CDAR94, CDSR93, DAHTA, DAHTA, EA08, ED93, EM00, EM47, HG05, KP05, KR03, ME00, ME60, PI67, PY81, TV01, TVPP). A total of 160 articles were found. Duplicates were removed and the remaining list was filtered with the objective to explore the influence of active or passive movement during experimentally induced RHI. Then we identified six articles which experimentally examined persistence of RHI during active or passive movements. Results Results indicate that RHI are maintained during active or passive movements due to visual and temporal congruency. During active movements the RHI is more stable or global than in passive movements or during tactile stimulation. Conclusion Factores like visual and temporal congruency are related to maintain RHI and are discussed in the rehabilitation of phantom sensations or symptomes of schizophrenic disorders.

Appearance of fetal pain could be associated with maturation of the mesodiencephalic structures

Fetal pain remains a controversial subject both in terms of recognizing its existence and the time-frame within which it appears. This article investigates the hypothesis that pain perception during development is not related to any determined structures of the central nervous system (CNS), on the contrary, the process of perception could be made with any structure satisfying conditions that the perception of pain is the organization, identification, and interpretation of sensory information in order to represent and understand the environment. According to this definition, chronic decerebrate and decorticate experimental animals, anencephalic, and hydranencephalic patients demonstrate that the basic, most general, appropriate interaction with the environment can be achieved with a functional mesodiencephalon (brain stem, and diencephalon) as the hierarchically highest structure of the CNS during development. In intact fetuses, this structure shows signs of sufficient maturation starting from the 15th week of gestation. Bearing in mind the dominant role of the reticular formation of the brain stem, which is marked by a wide divergence of afferent information, a sense of pain transmitted through it is diffuse and can dominate the overall perception of the fetus. The threshold for tactile stimuli is lower at earlier stages of gestation. The pain inhibition mechanisms are not sufficiently developed during intrauterine development, which is another factor that leads to increased intensity of pain in the fetus. As a conclusion it could be proposed that the fetus is exposed to rudimentary painful stimuli starting from the 15th gestation week and that it is extremely sensitive to painful stimuli.

Towards active lower limb prosthetic systems: design issues and solutions

Background A prosthesis is a crucial technical substitute that should restore biomechanical function and body integrity for people with lower limb loss or congenital limb absence [1]. Within the last decades, lower limb prostheses developed from passive mechanisms to adaptive mechatronic systems [2]. Contemporary, such prostheses evolve to robotic systems providing powered locomotion support by drives as shown in [3, 4]. According to the review in from [5], 21 different active lower limb prostheses are found in the research literature. With such technologies, various new research questions arise and the idea of prosthesis technology simulation is being discussed [6, 7]. Technically, the mechatronic design of actuators and kinematics as well as the development of suitable control algorithms are challenging tasks [3, 4]. A promising approach to actuation is found in compliant actuators and kinematics that store and transfer energy between gait phases [8]. To command those actuators, controllers that mimic biological function during different gait situations, speeds, and transitions as the one propose by Grimmer et al. [9] are required. Analyzing human biomechanics with and without considering the prosthetic system is a crucial basis for design and control that provides requirements and constrains [10]. Further, biomechanical studies can be used to assess the utility of active prostheses and indicate that those improve amputee gait [3, 11]. As prostheses are not only used by people, but aim at replacing lost parts of amputees’ bodies, human factors show significant impact on prosthetic development from a psychological perspective [12–14]. Those comprise aspects such as acceptance [15] and integration to the body schema [16–20]. Those human factors impact technical design [21, 22] and need psychological methods to be surveyed [23–25] and considered in design [26]. Additionally, insights regarding human factors can be used to develop and improve novel techniques for movement rehabilitation, e.g., gait training in virtual reality environments [27–29].

Exploration of lower limb body schema integration with respect to body-proximal robotics

The integration of body-proximal robots into the body schema of their users is a crucial aspect for the acceptance of those artificial devices. Humans integrate information about such systems from visual, tactile, and proprioceptive perception. For the design of novel, human-oriented robotics, it is important to understand how this integration can be supported by the technical design of the robot. In this paper, first experiments aiming at the assessment of lower limb body schema integration during postural motions are performed. A robot is used to imitate the squatting movements of human subjects. In contrast to a previous implementation, human motion sensing is improved for real-time operation by using inertial measurement units. A first human-in-the-loop experiment indicates that this approach resolves limitations caused by delays of the previous RGB-D measurements. The integration into the body schema of the participants is assessed by means of a psychometric questionnaire. Experimental results regarding body schema integration suggest that for body-proximal robotics noticeably detached from human subjects, agency is the most stable of body schema variables and that to induce a sense of ownership and location, more feedback channels to the subjects might be required.

Implementation, control and user-feedback of the Int 2 Bot for the investigation of lower limb body schema integration

The integration of prostheses or wearable robotics into the body schema of their users is a fundamental requirement for the acceptance and control of such artificial devices. Duration and progress of integration are primarily influenced by visual, tactile, and proprioceptive perception. This paper describes the Int2Bot, a robot for the assessment of lower limb body schema integration during postural motion. The robot is designed to imitate human squatting movements to investigate the integration of artificial limbs into the body schema. The psychological and technical concepts as well as the mechatronic implementation and control are presented along with interface extensions comprising human knee position sensing and tactile user-feedback. The performance of the robot is examined by experiments excluding and including the human-robot interface and a human user. Those without interface show that the robot itself can perform considerably fast squats with 0.8 Hz, which comes up to maximum human capabilities. The computed torque control achieves good tracking results and fuzzy-based friction compensation further reduces position errors by up to 50%. Yet, results considering the vision-based part of the human-robot interface show that the setup is mainly limited due to delays in motion acquisition with the RGB-D sensor.