The Role of Task and Situational Characteristics on the Dependability of Human-Technology Interaction

While the impact of "human error" on failures of complex human-technology systems has widely been demonstrated and accepted, the relevance of situational and task-related characteristics on human performance has not yet been considered sufficiently. For this purpose and on the example of electrically powered wheel chair control this paper analyzes the effects of situational characteristics ( e.g., turns to the left/right in the backward/forward driving mode) on the impact of fine motor abilities on human performance. A study with 23 participants is described in the paper, during which relevant data such as the subjects' precision and aiming capacity, the number of collisions caused while driving as an indicator for human performance, and the situational characteristics were measured. The data analyses demonstrate an influence of especially the number of turns driven to the right in the backward mode on the impact of the precision ability on the number of safety-critical collisions. The results highlight the necessity not only to develop a wheelchair system which is adaptable to the user’s fine motor abilities, but also to the situational characteristics in order to increase the dependability of the human-technology system at hand

Hierarchical Hybrid Monitoring for Autonomous Systems

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The Impact of Individual Differences in Fine Motor Abilities on Wheelchair Control Behavior and Especially on Safety-Critical Collisions with Objects in the Surroundings

In order to significantly reduce the number of safety-critical collisions of wheelchair users with objects spread in their environment, a study has been conducted which relates wheelchair user's fine motor abilities with the collisions while driving through a standardized course in a realistic office environment. The conducted inferential statistics demonstrate that especially the participants' aiming capacity can sign significantly predict the collisions occurring while driving through the course. A graphical and qualitative analysis of these effects demonstrates in addition that specific maneuvering tasks influence this relationship and that especially driving next to an object without colliding requires a high level of aiming capacity. The results demonstrate the need to develop a wheelchair system which adapts its assistive functionality to the aiming capacity and the difficulty of the maneuvering task in order to provide as much help as necessary without risking the degradation of the wheelchair user's skills

An Integrated Monitor-Diagnosis-Reconfiguration Scheme for (Semi-) Autonomous Systems

A nested monitoring, diagnosis and reconfiguration (MDR) scheme is proposed for a Recursive Nested Behavior based Control structure (RNBC)constituting a generic system architecture for (semi-) autonomous mobile systems. Each behavior layer within the RNBC structure is associated with a MDR schema, which is responsible to ensure the dependability of every single layer. An online dependability measurement and diagnosis procedure is integrated into monitor and diagnosis blocks under consideration of performance and safety acceptability factors. The reconfiguration blocks within the MDR-scheme switch from components with unacceptable behavior to redundant components, which may have degraded performance but more robust and safe behavior. The MDR blocks at each layer are nested through unified interfaces in order to utilize the distributed modeling of system behavior and to facilitate the system design and implementation process. In a small case study the MDR scheme is demonstrated for an assistant wheelchair on the body velocity control and axis velocity control levels. Simulation results show the feasibility and effectiveness of the approach

Dependable System Design for Assistance Systems for Electrically Powered Wheelchairs

In this paper a system design approach is proposed, which is based on a user needs assessment and a flexible and adaptable architecture for dependable system integration. The feasibility of the approach is shown on the example of an assistance system for electrically powered wheelchairs. The system requirements correspond to the cognitive and motor abilities of the wheelchair users. For the wheelchair system built up based on a commercial powered wheelchair several behaviors have been realized such as collision avoidance, local navigation and path planning well known from robotic systems, which are enhanced by human-interfacing components. Furthermore, the system design will be high lighted which is based on robotic systems engineering. Due to the fundamental properties of the system architecture the resulting assistance system is inherently dependable, flexible, and adaptable. Corresponding to the current situation and the users’ abilities the system changes the level of assistance during real-time operation. The resulting system behavior is evaluated using system performance and usability tests

Predictive validity of wheelchair driving behavior for fine motor abilities: Definition of input variables for an adaptive wheelchair system

Abstract-This paper introduces an approach for dynamically adapting the level of automation of a wheelchair system on the basis of the current level of the user's motor abilities. For this purpose, a study is described, during which participants drove through a course consisting of 14 sub-sections. The predictive validity of the participants' wheelchair driving behavior on their precision, tremor, wrist-finger velocity, arm-hand velocity and aiming capability was analyzed. The results demonstrate impressively (1) that some course sections can better be used in order to derive variables allowing a reasoning on the users' motor ability level than other sections and (2) that especially the precision ability can be predicted e.g. on the basis of the distances driven in the forward mode. Implications on how an adaptive assistance system for powered wheelchair could be implemented are discussed as is the impact of such a system on the wheelchair market. (Abstract

Wheelchair control based on a polynomial function approximating a user's gaze curve

We propose a new wheelchair control system based on a polynomial function approximating a user\u27s gaze curve. Conventional studies utilizing gaze data recognized three wheelchair movements: "go straight," "turn right," and "turn left." However, it was difficult for the system to assess when it should switch wheelchair motions because the user\u27s gaze was always changing. To solve this problem, we divided "turn right" and "turn left" wheelchair movements into three groups each in order to control the wheelchair easily. Consequently, the system has to recognize seven wheelchair movements: straight, and three groups each for turning right and left. It is not sufficiency for a system to assess seven wheelchair movements by only the user\u27s gaze. Thus, we developed a wheelchair system considering not only the user\u27s gaze but also the angular velocity and acceleration to control wheelchair motions. We approximated the user\u27s gaze using a polynomial function, and calculated the fine gaze angle, angular velocity and acceleration. The effectiveness of the proposed method was shown by experimental results

Dependable component-based design on the Example of a Heating Control System

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