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Open Access
Position sensor and control system for micro hydraulic drives in surgical instruments
(Stuttgart : Fraunhofer Verlag, 2019) Comella, Laura; Bauernhansl, Thomas (Univ.-Prof. Dr.-Ing.)
This work is focused on the research and development of a sensor that permits the control of the movement of a hydraulically driven laparoscopic instrument tip and opens the way towards a new interpretation of surgical instruments. In the new vision the instrument is able to execute automatically preprogrammed tasks, without the constant involvement of the surgeon in the instrument control. After an analysis on the state of the art for laparoscopic instruments and a revision of the relevant literature on sensors for displacement measurement, the coaxial cylindrical capacitive method was identified as the most suitable solution for the application analyzed. This sensor configuration can be integrated directly into the hydraulic cylinder without the need of additional parts. The feasibility of the coaxial cylindrical capacitive sensor is theoretically analyzed, validated with FEA simulation and then characterized experimentally. Relevant is the fact that the tests are run with two different hydraulic cylinders, a mini hydraulic and a micro hydraulic cylinder, to demonstrate the scalability of the sensor and its adaptability to instruments of different size. The experimental results match the simulations and confirm the sensor´s behavior also on experimental level. The sensor is than integrated in a closed loop system to test its suitability for controlling the position of the instrument tip in a scenario as close as possible to the real one. For this reason, a hydraulic drive, which permits the movement of the instrument tip, is designed. The full hydraulic drive system is modeled and this model is used to design a feedback control. The designed controller is initially proven through simulation. Afterwards it is tested with experiments proving the correspondence between simulated and real world behavior of the system.
Open Access
Scoping review of potentials to optimize planar solid oxide cell designs for use in fuel cell and electrolysis applications
(2025) Malicek, Bernhard; Speckmann, Friedrich-Wilhelm; Entenmann, Marc; Birke, Kai Peter
This scoping review evaluates the literature on options for planar solid oxide cell (SOC) performance optimization, with a focus on applied fabrication methods and design enhancements. Literature identification, selection, and charting followed PRISMA-ScR guidelines to ensure transparency, reproducibility, and comprehensive coverage, while also enabling the identification of research gaps beyond the scope of narrative reviews. We analyze the influence of fabrication methods on cell and component characteristics and evaluate optimization approaches identified in the literature. Subsequent discussion explores how design innovations intersect with fabrication choices. The surveyed literature reveals a broad spectrum of manufacturing methods, including conventional processes, thin-film deposition, infiltration, and additive manufacturing. Our critical assessment of scalability revealed that reduction in operating temperature, improving robustness, and electrochemical performance are the main optimization objectives for SOC designs. Regarding production cost, production scale-up, and process control, inkjet, electrophoretic deposition, and solution aerosol thermolysis appeared to be promising manufacturing methods for design enhancements. By combining the PRISMA-ScR evidence map with a synthesis focused on scalability and process control, this review provides practical insights and a strong foundation for future SOC research and scale-up, also for evolving the field of proton-conducting cells.
Open Access
Optimization of disassembly strategies for electric vehicle batteries
(2021) Baazouzi, Sabri; Rist, Felix Paul; Weeber, Max; Birke, Kai Peter
Various studies show that electrification, integrated into a circular economy, is crucial to reach sustainable mobility solutions. In this context, the circular use of electric vehicle batteries (EVBs) is particularly relevant because of the resource intensity during manufacturing. After reaching the end-of-life phase, EVBs can be subjected to various circular economy strategies, all of which require the previous disassembly. Today, disassembly is carried out manually and represents a bottleneck process. At the same time, extremely high return volumes have been forecast for the next few years, and manual disassembly is associated with safety risks. That is why automated disassembly is identified as being a key enabler of highly efficient circularity. However, several challenges need to be addressed to ensure secure, economic, and ecological disassembly processes. One of these is ensuring that optimal disassembly strategies are determined, considering the uncertainties during disassembly. This paper introduces our design for an adaptive disassembly planner with an integrated disassembly strategy optimizer. Furthermore, we present our optimization method for obtaining optimal disassembly strategies as a combination of three decisions: (1) the optimal disassembly sequence, (2) the optimal disassembly depth, and (3) the optimal circular economy strategy at the component level. Finally, we apply the proposed method to derive optimal disassembly strategies for one selected battery system for two condition scenarios. The results show that the optimization of disassembly strategies must also be used as a tool in the design phase of battery systems to boost the disassembly automation and thus contribute to achieving profitable circular economy solutions for EVBs.
Open Access
A method for the assembly of microelectronic packages using microwave curing
(Stuttgart : Fraunhofer Verlag, 2018) Adamietz, Raphael; Verl, Alexander (Univ.-Prof. Dr.-Ing. Dr. h. c. mult.)
Advanced electronic packaging continues to gain prevalence, driven by the continuous trend for miniaturization with concurrent functional integration. Processes in use today are typically efficient for mass production, but are not suitable for the purposes of low volume and prototype production. Adhesive bonding circumvents the elaborate tooling typical for mass production and provides a higher degree of flexibility. Disadvantages lie in long curing cycle times and high handling effort. To overcome these problems, a novel method for the assembly of electronic packages is proposed, one that improves the performance and efficiency of the assembly processes and reduces the handling effort between the separate process steps by integration of assembly and curing process equipment into a single machine. An analysis of the field of electronic packaging with particular respect to adhesive curing processes is performed. Then the relevant state-of-the-art is reviewed and the need of a novel method is identified. The conception and realization of a microwave curing system, based on an open-ended waveguide resonator are carried out. Different concepts for the control of the curing process are described. A machine integrating the curing system and the assembly process equipment is designed and prototypically realized. This is followed by extensive evaluation and testing of the novel method. In the course of the evaluation a representative flip-chip assembly is realized. In order to assess the influence on reliability, a series of temperature cycling tests is performed. Additionally, stress-measurement dies are packaged and the influence of the proposed method onto residual stresses is studied. The influence of the proposed method on throughput and assembly efficiency is investigated. The proposed method provides reduction of curing cycle times for three different adhesive materials and therewith an increase of the overall throughput. By reduction of handling effort, the overall process efficiency could be improved. Furthermore, by microwave curing with the proposed method, a higher reliability of the resulting electronic packages can be achieved. The experiments with the stress chips reveal lower residual stresses in the microwave-heated chips compared to convection heating.
Open Access
A systematic selection process of machine learning cloud services for manufacturing SMEs
(2022) Kaymakci, Can; Wenninger, Simon; Pelger, Philipp; Sauer, Alexander
Small and medium-sized enterprises (SMEs) in manufacturing are increasingly facing challenges of digital transformation and a shift towards cloud-based solutions to leveraging artificial intelligence (AI) or, more specifically, machine learning (ML) services. Although literature covers a variety of frameworks related to the adaptation of cloud solutions, cloud-based ML solutions in SMEs are not yet widespread, and an end-to-end process for ML cloud service selection is lacking. The purpose of this paper is to present a systematic selection process of ML cloud services for manufacturing SMEs. Following a design science research approach, including a literature review and qualitative expert interviews, as well as a case study of a German manufacturing SME, this paper presents a four-step process to select ML cloud services for SMEs based on an analytic hierarchy process. We identified 24 evaluation criteria for ML cloud services relevant for SMEs by merging knowledge from manufacturing, cloud computing, and ML with practical aspects. The paper provides an interdisciplinary, hands-on, and easy-to-understand decision support system that lowers the barriers to the adoption of ML cloud services and supports digital transformation in manufacturing SMEs. The application in other practical use cases to support SMEs and simultaneously further development is advocated.
Open Access
A performance and cost overview of selected solid-state electrolytes : race between polymer electrolytes and inorganic sulfide electrolytes
(2021) Karabelli, Duygu; Birke, Kai Peter; Weeber, Max
Electrolytes are key components in electrochemical storage systems, which provide an ion-transport mechanism between the cathode and anode of a cell. As battery technologies are in continuous development, there has been growing demand for more efficient, reliable and environmentally friendly materials. Solid-state lithium ion batteries (SSLIBs) are considered as next-generation energy storage systems and solid electrolytes (SEs) are the key components for these systems. Compared to liquid electrolytes, SEs are thermally stable (safer), less toxic and provide a more compact (lighter) battery design. However, the main issue is the ionic conductivity, especially at low temperatures. So far, there are two popular types of SEs: (1) inorganic solid electrolytes (InSEs) and (2) polymer electrolytes (PEs). Among InSEs, sulfide-based SEs are providing very high ionic conductivities (up to 10−2 S/cm) and they can easily compete with liquid electrolytes (LEs). On the other hand, they are much more expensive than LEs. PEs can be produced at less cost than InSEs but their conductivities are still not sufficient for higher performances. This paper reviews the most efficient SEs and compares them in terms of their performances and costs. The challenges associated with the current state-of-the-art electrolytes and their cost-reduction potentials are described.
Open Access
Analytic free-energy expression for the 2D-Ising model and perspectives for battery modeling
(2023) Markthaler, Daniel; Birke, Kai Peter
Although originally developed to describe the magnetic behavior of matter, the Ising model represents one of the most widely used physical models, with applications in almost all scientific areas. Even after 100 years, the model still poses challenges and is the subject of active research. In this work, we address the question of whether it is possible to describe the free energy A of a finite-size 2D-Ising model of arbitrary size, based on a couple of analytically solvable 1D-Ising chains. The presented novel approach is based on rigorous statistical-thermodynamic principles and involves modeling the free energy contribution of an added inter-chain bond DAbond(b, N) as function of inverse temperature b and lattice size N. The identified simple analytic expression for DAbond is fitted to exact results of a series of finite-size quadratic N N-systems and enables straightforward and instantaneous calculation of thermodynamic quantities of interest, such as free energy and heat capacity for systems of an arbitrary size. This approach is not only interesting from a fundamental perspective with respect to the possible transfer to a 3D-Ising model, but also from an application-driven viewpoint in the context of (Li-ion) batteries where it could be applied to describe intercalation mechanisms.
Open Access
Effects of load forecast deviation on the specification of energy storage systems
(2023) Emde, Alexander; Märkle, Lisa; Kratzer, Benedikt; Schnell, Felix; Baur, Lukas; Sauer, Alexander
The liberalization of the German energy market has created opportunities for end-consumers, including industrial companies, to actively participate in the electricity market. By making their energy loads more flexible, consumers can generate additional income and thus save money. Energy storage systems can be utilized to achieve the required flexibility by temporarily storing excess electrical energy in the form of heat, cold, or electricity for later use. This publication focuses on how the dimensionality of energy storage is influenced by load forecasting. The results show that inaccuracies in load forecasting lead to a direct over-dimensioning and thus, a deterioration of the economics of energy storage technologies. Using two scenario cases, it shows on the one hand how important good forecasts are and on the other hand that buffers must be included in the conceptual design in order to be able to compensate for forecast errors.
Open Access
Feasible energy density pushes of Li-metal vs. Li-ion cells
(2021) Karabelli, Duygu; Birke, Kai Peter
Li-metal batteries are attracting a lot of attention nowadays. However, they are merely an attempt to enhance energy densities by employing a negative Li-metal electrode. Usually, when a Li-metal cell is charged, a certain amount of sacrificial lithium must be added, because irreversible losses per cycle add up much more unfavourably compared to conventional Li-ion cells. When liquid electrolytes instead of solid ones are used, additional electrolyte must also be added because both the lithium of the positive electrode and the liquid electrolyte are consumed during each cycle. Solid electrolytes may present a clever solution to the issue of saving sacrificial lithium and electrolyte, but their additional intrinsic weight and volume must be considered. This poses the important question of if and how much energy density can be gained in realistic scenarios if a switch from Li-ion to rechargeable Li-metal cells is anticipated. This paper calculates various scenarios assuming typical losses per cycle and reveals future e-mobility as a potential application of Li-metal cells. The paper discusses the trade-off if, considering only the push for energy density, liquid electrolytes can become a feasible option in large Li-metal batteries vs. the solid-state approach. This also includes the important aspect of cost.
Open Access
Exploring different extrapolation approaches for the critical temperature of the 2D-Ising model based on exactly solvable finite-sized lattices
(2025) Markthaler, Daniel; Birke, Kai Peter
The fact that the Ising model in higher dimensions than 1D features a phase transition at the critical temperature Tcdespite its apparent simplicity is one of the main reasons why it has lost none of its fascination and remains a central benchmark in modeling physical systems. Building on our previous work, where an approximative analytic free-energy expression for finite 2D-Ising lattices was introduced, we investigate different extrapolation strategies for estimating Tcof the infinite system from exactly solvable small lattices. Finite square lattices of linear dimension N with free and periodic boundary conditions were analyzed, exploiting their exactly accessible density of states to compute the heat capacity profiles C(T). Different approaches were compared, including scaling models for the peak temperature Tmax(N)and an envelope construction across the set of C(T)-profiles. We find that both approaches converge to the same asymptotic value and compare favorably to the established Binder cumulant method. Remarkably, a model for Tmaxwith a single model parameter following an N/(N+1)-law provides robust convergence, with a physical analogy motivating this proportionality. Our findings highlight that surprisingly few, but highly accurate, finite-size results are sufficient to obtain a precise extrapolation.

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