Prof. Dr. Sandro Wartzack

Chair of Engineering Design, Department of Mechanical Engineering

Research and validation of processes, methods and tools to support the design of medical technologies and interventions.

Research projects

  • Biomechanical Engineering
  • Musculoskeletal Modeling and Simulation
  • Development of Exoskeletons and Ortheses
  • Preoperative Planning of Endosurgeries
  • Analysis and Optimization of User-Product-Interaction

Current projects

  • Product development ontology supporting the provision of decision-relevant knowledge for multicriteria evaluation of decision alternatives

    (Third Party Funds Single)

    Term: 1. October 2022 - 30. April 2024
    Funding source: Deutsche Forschungsgemeinschaft (DFG)
    URL: https://gepris.dfg.de/gepris/projekt/400342876?context=projekt&task=showDetail&id=400342876&

    Due to the growing complexity of modern products, new challenges arisefor product developers, whose central task is to fulfill the requirementsdemanded by the market. These requirements concern specific properties, which haveto be fulfilled by the product and ensured through related productcharacteristics. Due to the increase of product complexity, various relationsbetween the characteristics and properties occur, which makes theirconsideration more difficult. Changes in product characteristics lead todifferent properties of the whole system, which in the case of complex relationnetworks result in unmanageable and often undesirable property changes. Theeffects of this include cost-intensive iterations for the adaptation to the demandedproperties or even the failure of products in the market. For this reason,these influences have to be identified already during development and then takeninto account during multi-criteria evaluation of decision alternatives. Forthis purpose, consistent decision models are required that contain theserelations. In interdisciplinary product development, these relations as well asthe relevant information and data originate from domain-specific models and areavailable as heterogeneous databases. This results in challenges regarding theprovision of decision-relevant knowledge for multi-criteria decision processesand models.

    Motivated by these challenges, the objective of the proposed researchproject is to develop fundamental findings about the formalization and provisionof context-specific knowledge in the fields of requirements-based, multi-criteriadecision making. Ontologies offer a suitable method for the formalization andprovision of context-specific knowledge, therefore, the main objective of theproject has to be achieved with a decision-supporting product developmentontology (PEO). Within the ontology development the own preliminary work fromthe first phase of the project (WA2913/33-1) has be considered, which providesthe necessary fundamentals regarding computer aided multi-criteria decisionmaking based on all product requirements. The extension of the PEO through dataand knowledge integration from heterogeneous sources enables product developersto provide relevant decision knowledge consistently and reduces the effort formanual provision. Verification of the developed PEO requires new approaches fordefining suitable queries. In summary, the research project focuses on scientificfindings regarding the applicability and usability of ontologies for an efficientsupport of multi-criteria decision making.

  • Methodik zur Auslegung passiver, strukturoptimierter Orthesen für die Behandlung bzw. Kompensation pathophysiologischer Bewegungsmuster anhand muskuloskelettaler Menschmodelle

    (Third Party Funds Single)

    Term: 1. October 2021 - 30. September 2024
    Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)

    Ankle joint orthoses are the most common rehabilitation device used to treat pathophysiological gait patterns such as foot drop syndrome. For this purpose, passive orthoses are preferably used which enable a supporting or stabilizing function or even the support of a rotational direction of the joint with spring-damper systems. In the case of extensive paresis or paralysis of the lower leg musculature, active orthoses can be used to restore a healthy gait. With the appropriate actuators, these can support both directions of rotation of the joint. The use of active orthoses, however, is accompanied by many problems, such as their high weight, the less integral design and the complex control and power supply of the actuators. For this reason, a methodology is to be developed within the framework of the research project with which the design of passive ankle joint orthoses can be realized to support both directions of joint rotation. For this purpose, the orthosis is to be provided with suitable fibre-reinforced plastic lightweight structures which, in the event of elastic deformation, exhibit the structural response corresponding to the required support of the pathophysiological gait. The core objective of the research project is the development of a method which enables the structures to be designed in such a way that their structural response is in symbiosis with the patient's gait behaviour and thus enables the best possible treatment or compensation of the patient's disease. To this end, a coupling between an FE model for structural optimization and a musculoskeletal human model for mapping the physiological and pathophysiological gait is to be introduced. The orthosis design optimized with the help of the developed methodology is finally manufactured as a prototype and evaluated on the basis of a test set-up before the orthosis can be tested in practical trials in conjunction with patients.

  • OptNeTol: Integrated, optimization-based parameter and tolerance design

    (Third Party Funds Single)

    Term: 1. July 2021 - 31. December 2023
    Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)

    The usage of optimization methods for optimal tolerance allocation significantly contributes to the development of least-cost and high-quality products. By formulating suitable optimization problems and solving them with the aid of powerful algorithms, nominal dimensions and tolerance values can be allocated in a way that the cost potential is fully exploited while ensuring that the stringent requirements on robustness, function and aesthetics are fulfilled. In this way, optimization-based methods successively replace purely qualitative approaches, such as simple rules of thumb or well-known theorems like "define tolerances as wide as possible, but as tight as necessary", and thereby create an undisputed competitive advantage.

    In the preceding funding phase, an important basis for the productive use of tolerance optimization in the industrial environment was established. However, it cannot effectively contribute to answering practice-relevant questions yet. This is mainly due to the deficits of efficient, valid optimization methods, the missing link between the interdisciplinary methods and their lack of focus on practical problems.

    Therefore, the aim of this research project is to enable the product developer to assign cost-optimal part dimensions and tolerances to practically relevant application cases. This implies that the obstacles to the practical application of the interdisciplinary and at the same time highly specialized methods of nominal dimension and tolerance optimization are largely eliminated. In this context, innovative methods of nominal dimension and tolerance optimization are developed addressing aspects that have not been considered so far, but are absolutely necessary for practical use, such as geometrical tolerances or the handling of missing or uncertain cost information. However, since the optimization problems can only be solved by powerful, sampling-based optimization algorithms, the focus of this research project is also on the development and combination of methods to significantly increase the efficiency in the determination of valid optimization results, such as adaptive sampling and surrogate modelling, including statistical tolerance analysis methods. Finally, the individually developed methods will be linked in a software prototype based on a common, interdisciplinary knowledge base and their applicability will be evaluated in user studies. This ensures that product developers without in-depth knowledge of optimization are supported in defining and solving practical problems as automatically as possible. Thus, currently open research gaps preventing the change from an expert tool for mere tolerance optimization to an integrated, optimization-aided tolerance management are finally closed.

  • Bereinigung multimodaler Bewegungsmessdaten mittels individualisierter muskuloskelettaler Menschmodelle

    (Third Party Funds Group – Sub project)

    Overall project: Empathokinästhetische Sensorik - Sensortechniken und Datenanalyseverfahren zur empathokinästhetischen
    Modellbildung und Zustandsbestimmung
    Term: 1. July 2021 - 30. June 2025
    Funding source: DFG / Sonderforschungsbereich (SFB)
    URL: https://www.empkins.de/

    Es wird eine neuartige Methode zur Bereinigung und Filterung multimodaler Bewegungsmessdaten in Verbindung mit einer entsprechend notwendigen Multidomänenmodellierung muskuloskelettaler Ganzkörpermenschmodelle erforscht. Aufbauend auf den individualisierten Menschmodellen werden kinematische bzw. dynamische Trackingalgorithmen untersucht, die auf unterschiedliche Kombinationen multimodaler Messdaten angewendet werden können. Außerdem werden die neuen Methoden erprobt und evaluiert, sowie Benchmarks zu konventionellen Methoden durchgeführt. Neue EmpkinS-Messtechniken werden sobald verfügbar auf die neu etablierten Methoden transferiert.

  • Erforschung der posturalen Kontrolle basierend auf sensomotorisch erweiterten muskuloskelettalen Menschmodellen

    (Third Party Funds Group – Sub project)

    Overall project: Empathokinästhetische Sensorik
    Term: 1. July 2021 - 30. June 2025
    Funding source: DFG / Sonderforschungsbereich (SFB)
    URL: https://www.empkins.de/

    A novel postural control model of walking is explored to characterise the components of dynamic balance control. For this purpose, clinically annotated gait movements are used as input data and muscle actuated multi-body models are extended by a sensorimotor level. Neuromotor and control model parameters of (patho-)physiological movement are identified with the help of machine learning methods. Technical and clinical validation of the models will be performed. New EmpkinS measurement techniques are to be transferred to the developed models as soon as possible.

  • Hybrid Models for the Development of Technical Systems for Direct Interaction with Humans - Units with Power Tools and Upper Body Support Systems as an Example

    (Third Party Funds Single)

    Term: 1. November 2020 - 30. May 2023
    Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
    The aim of the present research project is the development of a methodology for the development of wearable and hand-held technical systems, which are in close interaction with human beings. Systems in focus are both support systems that are parallel to the human body (e.g., exoskeletal systems) as well as systems acting serial to the human body (e.g., hand-held devices such as power tools). This methodology merges methods of use-case modelling, support systems, bio-mechanical models of the human body and multi-critical optimization algorithms. Through the combination and extension of common simulation approaches with bio-mechanical models of the human body arise hybrid models for the product development of exoskeletons and power tool, one parallel and one serial to the human body. This proposed research project enables, in contrast to today, the integrative development of exoskeletons and power tools regarding the focused use-cases. Currently, the direct combination of support-system and power tools happens to be challenging for the developer. Reasons are the consideration of the complex human anatomy, the correct choosing of harmless force introduction into the human body and especially the complex human motion patterns. The current approach of intuitive evaluation of boundary conditions regarding the user is experience based knowledge of experts and engineers familiar with the topic. An evaluation during development of support-system and power tool is yet not possible since final and wearable prototypes are required. The proposed methodology aims to close this gap by providing new hybrid models for the full support during design and a continuous evaluation of the developed support-system and power tool. Therefore, methods of use-case and human body modelling are merged to create these hybrid models through co-simulation. In this proposed research project, the methodology will be developed and evaluated for an upper-body support-system (exoskeleton) with an integrated wrench for the use case bolting above the head.
  • Customized Digital Engineering für bayerische KMU am Beispiel des Antriebsstrangs elektrischer Fahrzeuge

    (Third Party Funds Single)

    Term: 1. April 2020 - 31. March 2023
    Funding source: Bayerische Forschungsstiftung
    URL: https://www.bayfor.org/forcude
  • Virtual and experimental tolerance analysis of deviated assembly groups

    (Third Party Funds Group – Sub project)

    Overall project: FOR 2271: Prozessorientiertes Toleranzmanagement mit virtuellen Absicherungsmethoden
    Term: 1. April 2020 - 31. March 2023
    Funding source: DFG / Forschungsgruppe (FOR)
    URL: https://www.for2271.tf.fau.de/startseite/for-2271-tp1/
    The aim of the research project is to enable a process-oriented tolerancing, which considers all geometric deviations and their various sources as well as measurement uncertainties, by providing the required methods and tools. In order to achieve this goal, particularly the research challenges regarding the best practice for process-oriented tolerance specification, regarding the integration of various kinds of geometric deviations in tolerance simulation models and regarding the use of tolerance simulation results for optimized tolerance allocation and process design are answered. The focus of the research project in the second funding period of the research unit is on the extension of the interdisciplinary process-oriented tolerance allocation with regard to the consideration of wear behavior during use. Here, the entire intended product use is virtually validated with tolerance management tools by not only taking into account process variations during product development, but also virtually mapping wear influences during operation in the simulation models. In order to validate the novel simulation models developed, experimental tolerance analysis are carried out on the test stand of the research unit, the results from which are compared with the virtual results. In addition, a tolerance optimization is to be carried out in order to meet specified quality targets over the product lifecycle while at the same time ensuring that production and measuring process-related restrictions are observed.Beside the development of virtual tools for the tolerance analysis and their validation, methods and best practices for the integrated and holistic tolerance management are provided, which consider the characteristic features of computer-aided engineering tools and which will be checked in cooperation with the partners of the research unit. Thus, the main benefit of the research project is a procedure for process-oriented tolerancing, which allows the holistic consideration of various kinds and sources of geometric deviations already during product development as well as the identification of relevant process and operating parameters. Based thereon, manufacturing and inspection processes can be systematically optimized, costs can be saved and the time-to-market can be shortened.
  • Konstruktive Auslegung wandlungsfähiger Fügeverbindungen

    (Third Party Funds Group – Sub project)

    Overall project: Methodenentwicklung zur mechanischen Fügbarkeit in wandlungsfähigen Prozessketten
    Term: 1. July 2019 - 30. June 2023
    Funding source: Deutsche Forschungsgemeinschaft (DFG)
    URL: https://trr285.uni-paderborn.de/

    Das Teilprojekt B05 verfolgt das Ziel, eine ganzheitliche Konstruktionsmethode bereitzustellen, die den Produktentwickler befähigt, in der Entwurfsphase sowohl die Gestalt von Fügeteil und Fügestelle festzulegen als auch die Fügeverbindung selbst auszuwählen und rechnerisch zu dimensionieren. Dafür wird ein für den Konstrukteur handhabbares, analytisches Formelwerk sowie ein wissensbasierter Gestaltungsprozess erforscht werden, mit dem die Anforderungen der Fertigung, aber auch der Beanspruchungsgerechtheit berücksichtigt werden können. Unterstützt wird hierdurch vor allem die frühe Phase der Produktentwicklung, noch vor der gestaltgebenden Phase bzw. dem Vorliegen ausdetaillierter CAD-Produktmodelle. Die zentrale wissenschaftliche Herausforderung des Teilprojekts besteht darin, die Methode zur konstruktiven Auswahl und Auslegung mechanischer Fügeverbindungen einerseits handhabbar zu halten und andererseits so anpassungsfähig zu gestalten, um auch verschiedene Fügeverfahren flexibel und robust in wandlungsfähigen Prozessketten auslegen zu können. Um dies zu erreichen, sind Methoden zu erarbeiten, die es erlauben, aus mathematischen Metamodellen analytische Auslegungsformeln abzuleiten. Grundlegend untersucht wird zudem die Erzeugung von aussagekräftigen mathematischen Metamodellen auf Basis experimentell und simulativ gewonnener Daten. Dies stellt aufgrund der Begrenztheit der zugrundeliegenden Daten gegenüber der bekannten, auf großen Datenmengen basierenden Metamodellierung eine besondere Herausforderung dar. Aus Sensitivitäts- und Robustheitsanalysen an den Metamodellen ergeben sich relevante und nicht-relevante Parameter als Basis für die Modellreduktion. Diese sind ferner abzugrenzen in vom Konstrukteur direkt beeinflussbare Parameter (Merkmale) und sich daraus ergebende Parameter (Eigenschaften). Neben der Ermittlung der relevanten Konstruktionsparameter stellt die Betrachtung der geometrischen Gestaltung einen weiteren Fokus des Teilprojekts dar. Die geometrischen Gestaltungsmöglichkeiten und -restriktionen, die sich beispielsweise aus den Anforderungen der Fertigung, aber auch für eine kraftflussgerechte Gestaltung ergeben, sollen dazu in eine Wissensbasis überführt werden. Auf den Ergebnissen der Parameterabstraktion und der Gestaltungsrestriktionen aufbauend ist ein konstruktionsmethodischer Entwicklungsprozess zu strukturieren, der die relevanten Auslegungskriterien wie beispielsweise Steifigkeit, Festigkeit oder Korrosionsbeständigkeit der Verbindung gewichtet und die vom Konstrukteur zu unternehmenden Schritte definiert. Zur Kontrolle der Zielerreichung wird der erarbeitete Konstruktionsprozess am Beispiel des Clinchens zweier gleichartiger Metalle unter statischer Last auf seine Handhabbarkeit hin evaluiert. Nach Abschluss des Vorhabens steht damit eine Konstruktionsmethode zur Verfügung, welche der Wandlungsfähigkeit mechanischer Fügeverbindungen sowie der Robustheit und Übertragbarkeit auf weitere Verfahren Rechnung tragen kann.

  • FOR 2271: Prozessorientiertes Toleranzmanagement mit virtuellen Absicherungsmethoden

    (Third Party Funds Group – Overall project)

    Term: 1. June 2016 - 31. December 2019
    Funding source: DFG / Forschungsgruppe (FOR)
    URL: https://www.for2271.tf.fau.de/

    The comprehension of geometric part deviationsand their manufacturing and assembly related sources as well as the investigationof their effects on the function and quality of technical products builds theframework for the planned research group “process-oriented tolerance managementbased on virtual computer-aided engineering tools”. The aim of this researchgroup is the provision of holistic methods and efficient tools for thecomprehensive management of geometric deviations along the product originationprocess, which are to be validated in a model factory. In doing so, aparticular focus is set on the development of a procedure for the fruitfulcooperation of all departments involved in geometric variations management,from product development, to manufacturing, to assembly and to metrology, whichwill enable companies to quickly specify functional tolerances, which aremanufacturable and measurable, and consequently to save costs and to reduce thetime to market.

    In this regard, the vision of the researchgroup is to enable the close collaboration of product development,manufacturing, assembly and metrology in computer-aided tolerancing, i. e.the joint formulation of functional tolerances, which are manufacturable andmeasurable. By enabling this close collaboration, all manufacturing andassembly related sources of later problems regarding the product function andquality can be considered already during early phases of virtual product andprocess development. As a consequence, tolerances can be specified efficientlyand optimized inspection plans as well as robust manufacturing and operatingwindows can be identified, which allows the development of robust products tobe manufactured and measured at low costs.  

    Since geometric part deviations are inevitableand affect the function and quality of technical products, their managementalong the product origination process is essential for the development offunctioning products, which conform to the quality and usage requirements ofcustomers and are successful on international markets. As a consequence,tolerance management is a fundamental task in product development and reachesvarious fields of industry, from consumer to industrial goods. Due to steadilyincreasing requirements on quality and efficiency, it strongly gains importancenot only with large, but also small and medium-sized enterprises. In thiscontext, the industrial application of the scientific findings of the researchgroup will contribute to the success of the German economy.  

Recent publications

2023

2022

2021

2020

Related Research Fields

Contact: