Theo de Vries

The safety of domestic robotics: a survey of various safety-related publications

Different branches of technology are striving to come up with new advancements that will enhance civilization and ultimately improve the quality of life. In the robotics community, strides have been made to bring the use of personal robots in office and home environments on the horizon. Safety is one of the critical issues that must be guaranteed for the successful acceptance, deployment, and utilization of domestic robots. Unlike the barrier-based operational safety guarantee that is widely used in industrial robotics, safety in domestic robotics deals with a number of issues, such as intrinsic safety, collision avoidance, human detection, and advanced control techniques. In the last decade, a number of researchers have presented their works that highlighted the issue of safety in a specific part of the complete domestic robotics system. This article presents a general survey of various safety-related publications that focus on safety criteria and metrics, mechanical design and actuation, and controller design.

Learning Feed-Forward Control: A Survey and Historical Note

Abstract From a mechatronic point of view, the performance of electro-mechanical motion systems can be improved by changing both the mechanical design and the controller. The design of a controller is generally based on a model of the plant. Thus, to improve the controller, a more accurate model of the plant is required. When the structure is not known or when many parameters cannot be determined, learning control may be considered. A simple yet powerful learning control scheme that is suitable for electro-mechanical motion systems is Learning Feed-Forward Control. In this paper an overview is given of applications that have been reported concerning this scheme. Also, relations are listed with alternative learning control schemes that are in some sense alike.

Computer support for mechatronic control system design

This paper discusses the demands for proper tools for computer aided control system design of mechatronic systems and identifies a number of tasks in this design process. Real mechatronic design, involving input from specialists from varying disciplines, requires that the system can be represented in multiple views. Several tools are already available but there are still substantial shortcomings. The paper gives indications about the developments needed to come to better design tools in the future. A specific example is worked out in more detail, i.e., automated performance assessment of mechatronic motion systems during the conceptual design stage.

Combining energy and power based safety metrics in controller design for domestic robots

This paper presents a general passivity based interaction controller design approach that utilizes a combined energy and power based safety norms to assert safety of domestic robots. Since these robots are expected to co-habit the same environment with a human user, analysing and ensuring their safety is an important requirement. Safety analysis of domestic robots determine whether a robot achieves a desired safety level according to some quantitative safety metrics. When it comes to controller design for human friendly robots, it often involves introducing compliance and ensuring asymptotic stability using impedance control technique and passivity theories. The controller proposed in this work also uses a passive design that extends the standard impedance control scheme with energy and power based safety metrics to ensure that safety requirements defined in these norms are achieved by domestic robots. The effectiveness of the proposed guideline is illustrated with simulation and experimental results.

PID motion control tuning rules in a damping injection framework

This paper presents a general design approach for a performance based tuning of a damping injection framework impedance controller by using insights from PID motion control tuning rules. The damping injection framework impedance controller is suitable for human friendly robots as it enhances safety due to the compliance it introduces and guarantees asymptotic stability because of its passive nature. In order to perform successful manipulation with a damping injection framework controlled robot, a performance based analysis and tuning of the controller is essential. By mapping a performance based frequency domain tuning of PID controllers on the framework, the proposed tuning method attempts to analyze and define controller parameters that yield a desired performance requirement given in terms of the maximum allowed position error. The effectiveness of the proposed guideline is illustrated with simulation and experimental results.

Improving Price/Performance ratio of a linear motor by means of learning control

A set of experiments is performed to experimentally validate that Learning Feed-Forward Control can compensate for reproducible errors that were introduced because of a low-cost electro-mechanical construction. A linear motor is used in this set of experiments in which the magnet plates and the driving coils could be exchanged. Several configurations are tested with different combinations of magnet plates and coils while Learning Feed-Forward Control is used to compensate for the disturbing effects. It is shown that the tracking error after learning is hardly influenced by the accuracy of the placement of the magnets and the tolerance on their strength. This allows to use low-cost magnets in a linear motor without degenerating the performance. The quality of the driving coils has a more significant influence on the tracking error after learning.

Performance Optimisation of Learning Feed Forward Control

The performance of sub-optimal feedback controllers can be improved in several ways. In this paper a learning control strategy is considered. The learning control system consists of the feedback and a feed forward controller. The feed forward controller is implemented as a neural network that is trained during control in order to minimise the tracking error. The type of neural network is a single layer network, in which B-spline basis functions are used to store the input-output mapping. The distribution of the Bsplines on the domain of the input(s) is of influence on the performance of the learning controller. Until recently, the basis functions were distributed by rule of thumb. In this paper fuzzy clustering techniques are used to obtain the distribution in a systematic way. In experiments the learning controller has been used to control a linear motor. Also when the B-splines are chosen by rule of thumb, the learning controller was able to improve the performance of the feedback controller considerably. The tracking error could be reduced further by determining the distribution of the basis functions using fuzzy clustering.

Automated Assessment of Patients’ Self-Narratives for Posttraumatic Stress Disorder Screening Using Natural Language Processing and Text Mining

Patients’ narratives about traumatic experiences and symptoms are useful in clinical screening and diagnostic procedures. In this study, we presented an automated assessment system to screen patients for posttraumatic stress disorder via a natural language processing and text-mining approach. Four machine-learning algorithms—including decision tree, naive Bayes, support vector machine, and an alternative classification approach called the product score model—were used in combination with n-gram representation models to identify patterns between verbal features in self-narratives and psychiatric diagnoses. With our sample, the product score model with unigrams attained the highest prediction accuracy when compared with practitioners’ diagnoses. The addition of multigrams contributed most to balancing the metrics of sensitivity and specificity. This article also demonstrates that text mining is a promising approach for analyzing patients’ self-expression behavior, thus helping clinicians identify potential patients from an early stage.

Cooperation Instead of Competition

Introduction: A national healthcare system can be managed by the government, independent market-driven providers, networks of managed care organizations, or a combination of the public—private partnership. While the benefits and limitations of government-managed care and market competition are well documented, little is known about the functioning of privately operated networks. In 2008, we investigated how the quality of care provided by these private networks is affected by unique characteristics and external influences. Methods: Over 1,000 managers and municipal administrators in eight regional healthcare networks in South Holland (a Dutch province; population 3.5 million) were surveyed. Results: The overall survey response rate was 49%. We found that the fitness of a network depends on the tightness of the couplings between its elements and the interactions with its environment. Loose couplings in a simple environment and tight couplings in a complex environment result in positive outcomes. The opposite is true if internal constraints (tightness) do not match external complexity. Fitness and regional outcome variability were measured by the quality of care provided by the networks. Correlations were found between quality and two independent variables: environmental complexity (r=0.75, p=0.017) and strength of couplings (r=0.76, p=0.015). Together complexity and coupling tightness explain almost three-quarters of the quality of care variability (adjusted R square=0.74). Conclusions: The authors propose that the knowledge of network mechanisms can guide interventions to improve care, as compared to government planning or free market competition. SamenvattingInleiding: een nationaal zorgsysteem kan georganiseerd worden door de overheid, onafhankelijke marktgedreven aanbieders, netwerken van zorgorganisaties, of een combinatie van publiek/private samenwerking. Terwijl de voordelen en beperkingen van door de overheid geplande zorg en marktwerking goed gedocumenteerd zijn, is er weinig bekend over het functioneren van privaat opererende netwerken. In 2008 hebben we onderzocht hoe de zorgkwaliteit, die deze netwerken leveren, door unieke eigenschappen en externe krachten beinvloed wordt. Methoden: Ruim 1.000 managers en locale beleidsambtenaren in acht regionale zorgnetwerken in Zuid-Holland (een Nederlandse provincie; 3,5 miljoen inwoners) werden bevraagd. Resultaten: De respons was 49%. We vonden dat de geschiktheid van een netwerk afhankelijk was van de sterkte van de koppelingen tussen de netwerkelementen en de interactie met zijn omgeving. Losse koppelingen in een simpele omgeving en strakke koppelingen in een complexe omgeving hebben positieve uitkomsten tot resultaat. Het omgekeerde geldt als de (sterkte) van de interne verknooptheid niet in overeenstemming is met de omgevingscomplexiteit. Geschiktheid en variatie in de regionale outcome werden afgemeten aan de zorgkwaliteit die de netwerken leveren. Verbanden werden gevonden tussen de kwaliteit en twee onafhankelijke variabelen: omgevingscomplexiteit (r=0.75, p=0.017) en sterkte van de koppelingen (r=0.76, p=0.015). Samen verklaren complexiteit en sterkte van de koppelingen bijna driekwart van de variatie in zorgkwaliteit (adjusted R square=0.74). Conclusies: De auteurs stellen dat kennis van netwerkmechanismen beter de interventies om de zorg te verbeteren kunnen leiden dan overheidsplanning of marktconcurrentie.

Energetic optimization of a piezo-based touch-operated button for man-machine interfaces

This paper discusses the optimization of a touch-operated button for man–machine interfaces based on piezoelectric energy harvesting techniques. In the mechanical button, a common piezoelectric diaphragm, is assembled to harvest the ambient energy from the source, i.e. the operator’s touch. Under touch force load, the integrated diaphragm will have a bending deformation. Then, its mechanical strain is converted into the required electrical energy by means of the piezoelectric effect presented to the diaphragm. Structural design (i) makes the piezoceramic work under static compressive stress instead of static or dynamic tensile stress, (ii) achieves a satisfactory stress level and (iii) provides the diaphragm and the button with a fatigue lifetime in excess of millions of touch operations. To improve the button’s function, the effect of some key properties consisting of dimension, boundary condition and load condition on electrical behavior of the piezoelectric diaphragm are evaluated by electromechanical coupling analysis in ANSYS. The finite element analysis (FEA) results indicate that the modification of these properties could enhance the diaphragm significantly. Based on the key properties’ different contributions to the improvement of the diaphragm’s electrical energy output, they are incorporated into the piezoelectric diaphragm’s redesign or the structural design of the piezo-based button. The comparison of the original structure and the optimal result shows that electrical energy stored in the diaphragm and the voltage output are increased by 1576% and 120%, respectively, and the volume of the piezoceramic is reduced to 33.6%. These results will be adopted to update the design of the self-powered button, thus enabling a large decrease of energy consumption and lifetime cost of the MMI.