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Industrial machine tool feed drives are predominantly controlled by cascade control due to their low tuning complexity and inherent robustness. However, the cascaded structure requires the inner cascades to have higher dynamics than the outer cascades, which limits the achievable dynamic accuracy. Direct control approaches, which substitute the position and velocity cascade, offer the potential to utilize the unused potential. A promising approach is model predictive control (MPC), which optimizes the manipulated variable with a plant model along a prediction horizon. However, model uncertainties between the nominal model and the real plant lead to tracking errors. Therefore, this paper presents, a linear MPC (LMPC) and an adaptive MPC (AMPC) with an additional integral action to robustly compensate for model mismatches. Both controllers use a compliant model, are real-time capable with a sample rate of $${{2}\,\textrm{kHz}}$$ 2 kHz and consider state and input space constraints. The AMPC accounts for position-varying stiffness and friction. The controllers are experimentally compared with classical P-PI cascaded control on a ball screw drive. They show a tracking error reduction of $${{37}{\,\%}}$$ 37 % (LMPC) and $${{44}{\,\%}}$$ 44 % (AMPC) during a high speed motion profile and an increase in bandwidth of $${{180}{\,\%}}$$ 180 % (LMPC) and $${{184}{\,\%}}$$ 184 % (AMPC), resulting in significantly improved dynamic accuracy.

Load-oriented lightweight structures are commonly designed based on topology optimization. For machine tool parts, they enable the reduction of moving masses and therefore increase the resource and energy efficiency of production systems. However, this usually results in complex part structures that are difficult or impossible to produce using conventional manufacturing methods. In this paper, a hybrid layer laminated manufacturing (LLM) method is proposed enabling manufacturing of topology-optimized machine tool parts. The method is referred to as hybrid, as the subtractive structuring of metal sheets is combined with the additive joining of the sheets by adhesive bonding. This enables enclosed inner cavities without support structures, which are used to approximate the optimal density distribution from a topology optimization via manufacturing. The proposed LLM method is validated on the basis of a bearing block of a ball screw feed drive. A experimental study in the time and frequency domain on a test rig confirms the principle suitability of the LLM method for the production of industrial applicable lightweight components., Deutsche Forschungsgemeinschaft, Projekt DEAL

Recent trends show that products are becoming more complex and multi-variant. Therefore, future production systems need to become more advanced in terms of reconfigurability, flexibility, and transformability. To achieve these advancements, future systems must be highly changeable and support plug-and-produce approaches. The majority of today’s engineering methods focus on static workflows based on predefined assets and setups. As a consequence, changes in the production system come with high costs, especially during production process execution. Therefore, new engineering methods are required which are explicitly designed for highly changeable production systems. To contribute towards fully changeable production systems, an I4.0 framework is proposed that covers the entire engineering process. The focus is set on presenting a graphical I4.0-enabled engineering method that enables dynamic workflows with varying assets and setups. Moreover, in order to evaluate the method, a user study was conducted, in which participants were asked to solve multiple engineering tasks by utilizing the presented I4.0-enabled method as well as a conventional approach. The results indicated that the proposed I4.0-enabled engineering method significantly outperformed the conventional method in terms of required engineering times and subjective ratings.

The mechanical stiffness of rack-and-pinion drives is independent from the current positioning, which yields the advantage that even long travel distances can be realized without sacrificing dynamics. A substancial disadvantage of this kind of drive, however, is the influence of nonlinear friction effects and the occurance of backlash. Proven methods minimizing the effects of these disturbances are mechanically or electrically pre-loaded powertrains, which, by requiring mutiple drive components and causing higher wear, are cost-intesive. Within this work, the possibility of a control-based strategy to compensate friction effects, which mutually interact with backlash, is investigated. The aim is the usage of MEMS-accelerometers in order to provide a cost-effective alternative to exisiting compensation measures. Central requirements are the enhancement of positioning accuracy as well as industrial applicability. The results of this work provide a strategy, which, by measuring the current acceleration of the drive and utilizing a simplified rack-and-pinion model, counteracts the negative influence of friction and backlash effectively. As part of a theoretical analysis, stability and robustness of the presented strategy are proven. Furthermore, the results found are validated experimentally by the realization of the compensation scheme on a rack-and-pinion test rig.

This paper presents a new control principle to improve the bandwidth of feed drives without any additional sensor or actuator. The speed difference between the motor and the table is regarded as the mechanical vibration and fed back to the controller. The presented principle is feasible for feed drives with large inertia ratio, which can be achieved by utilizing a ball screw with high pitch and a high dynamic motor with small inertia. The stability condition is found through the Lyapunov criteria. The experimental results verify its effectiveness and robustness.

Increasing resource and energy efficiency for a sustainable production has led to the analyses of saving potentials and subsequently to the development of saving strategies in a multitude of disciplines. Each of those strategies resulted in numerous improvements, however, they still lack universal valid consideration. To overcome this deficit, a machine- and machine control-independent energy control system has been developed in the research group ECOMATION. The energy control system allows to execute any control- or operation-based energy optimizer. To use this energy control system more efficient machine tool controls need to be extended by additional functionality. The energy control system and the necessary migration strategy of machine tool controls will be discussed in this paper.

This paper presents an approach to how existing production systems that are not Industry 4.0-ready can be expanded to participate in an Industry 4.0 factory. Within this paper, a concept is presented how production systems can be discovered and included into an Industry 4.0 (I4.0) environment, even though they did not have I4.0-interfaces when they have been manufactured. The concept is based on a communication gateway and an information server. Besides the concept itself, this paper presents a validation that demonstrates applicability of the developed concept.

Machining using industrial robots is currently limited to applications with low geometrical accuracies and soft materials. This paper analyzes the sources of errors in robotic machining and characterizes them in amplitude and frequency. Experiments under different conditions represent a typical set of industrial applications and allow a qualified evaluation. Based on this analysis, a modular approach is proposed to overcome these obstacles, applied both during program generation (offline) and execution (online). Predictive offline compensation of machining errors is achieved by means of an innovative programming system, based on kinematic and dynamic robot models. Real-time adaptive machining error compensation is also provided by sensing the real robot positions with an innovative tracking system and corrective feedback to both the robot and an additional high-dynamic compensation mechanism on piezo-actuator basis.

Assembly modeling, which is established by geometric constraints, plays an important role in product design. However, most constraint solving methods are only applicable for the cases in which the orientation constraints between base and mating component are either fit or against. This paper presents a modified geometric constraint solving method. It allows arbitrary angles for the orientation constraints and implements them into rotation matrix that determines the relative orientation of a mating component to a base component. The method transforms the constraints to a set of nonlinear equations firstly, and then solves it algebraically instead of using numerical methods.

This paper presents an algorithm to automatically generate the finite element models for parallel kinematics. The algorithm translates the geometric constraint information of each component to equations. The relative positions between components can be determined by solving those equations. The algorithm is independent of the kinematic structure. It has been already implemented in component oriented finite element modeling software and has been tested on some practical examples.

Current developments in automation technology deal with “cyber physical systems”. These cyber physical systems have sensors and actors and can make decisions based on their own intelligence as well as partially adapt to changing conditions. For a versatile and networked production cyber physical systems are of limited value. Precisely where the available sensors and actuators have to be combined flexibly due to ever new conditions, these systems find their limits because of their insularity. Limited computing hardware resources and lacking interfaces confine the possibilities of cyber physical systems in production environment. This paper explains how cyber physical systems need to be developed further in order to meet the requirements of a versatile and networked production plant.

In flexible und complex handling systems trajectory planning becomes increasingly demanding. As an example, the geometry of the work pieces tends to vary more than it used to. Therefore, the planned trajectory of the handling robot has to either be adjusted for each piece individually or the trajectory has to allow general geometry. This leads to performance loss for smaller work pieces since they are less sensitive to obstacles and can therefore be moved on shorter (faster) trajectories. In both cases, time and costs could be reduced. Another characteristic of handling systems is that several handling robots share the same workspace. Again the positions of these obstacles are only known at runtime. This places great demands on the planning tools. In this paper, it is shown that both problems can be treated with a hybrid method called curve flow method. This method combines a gradient flow which comes from a variational principle and a potential field method. The variational principle makes the planned trajectories short, the potential field prevents collision.

Ball screw feed drives are the most commonly used mechanism to provide linear motion in high speed machine tools. Position accuracy and the achievable closed loop bandwidth of such drive systems are usually limited by the structural vibration modes of the mechanical components. Higher order plant models allow for a better understanding of the system dynamics, improve the design process of feed drives and are essential for the development of sophisticated control strategies. The ball screw shaft, describing a complex flexible structure, is probably the most significant component concerning structural vibration modes of a feed drive. In this paper, the behavior of the shaft and its dominant influence at different operating and coupling conditions is particularly addressed. Using a hybrid modeling technique, the main characteristics of the shaft are derived and projected onto a clearly arranged and versatile lumped mass model. Simulative and experimental examinations are conducted and a parameter analysis is performed. The presented model proofs to be accurate for a great range of parameters and in addition allows for a physical interpretation of the dominant structural vibration modes of a feed drive.

Today’s machine tools are highly complex mechatronic systems capable to exert large translational and rotatory movements. In most cases rolling bearings are used to connect the moving parts to each other. As full FE models of rolling bearings can consume a large amount of degrees of freedom (DOF) efficient methods for reducing the DOF consuming rolling elements to more simple equivalent models are needed. As an example a linear guide system is used. A special feature of the considered linear guide is that the runner block consists of three separate parts, which are hold together only by pretension and friction. FE simulations of such linear guide system were not reported before in the literature. Beside the full FE model three equivalent contact models are presented. The first two equivalent contact models feature novel characteristics. Advantages and disadvantages of the equivalent models are discussed using as reference a slice of the full model and simulation results of static stiffness. The validation of the numerical models is also done using the general analytical solution of Hertz.

Lightweight design of production machines results in a problematically high inclination of vibration. Existing control techniques can avoid those vibrations based on the knowledge of the instantaneous system behavior, which is highly nonlinear and dependent on the machine’s pose. One possibility is to calculate the machine behavior using a model of the machine on the control device. By this, additional and expensive sensors in the machine structure are avoided but it requires a fast and efficient algorithm of model-based system behavior identification calculated online on the control device. In this paper, we describe a new approach for model-based system behavior calculation on the control device for the vibration reduction. Emphasizes lies on the integration of the method into the engineering process, which is shown in the fact that standard models out of the engineering process are used. The approaches and benefits of the technique are shown on a two-axes machine structure.

In the product development process numerical optimization can successfully be applied in the early product design stages. In the very common case of ball screw drives, the dynamical behavior is most depending on the geometrical shape of the ball screw itself. Properties like axial and torsional stiffness, moment of inertia, maximum velocity and acceleration are determined not only by the servo motor but also by screw diameter, slope and ball groove radius. Furthermore coupling effects between the design variables make the optimization task even more difficult. In order to capture these effects, efficient numerical (usually FEM or MBS) models are needed. In this work a new more accurate and efficient method of computing the axial and torsional stiffness of ball screw spindles is presented. We analytically derive parametric equations which depicts most of the dependencies of stiffness on geometrical parameters of the screw. Furthermore, we enhance the analytical model with an identified function, which increase the accuracy even more. The presented analytical model is validated against FEM model and catalog data with the help of numerous examples.

Bisher gab es keine zerstorungsfreie Untersuchungsmethode, die eine uber den rein qualitativen Nachweis von Defekten hinausgehende quantitative Beurteilung von Klebeigenschaften erlaubt. Erstmals moglich wird dies durch den intelligenten Einsatz der digitalen Shearografie unter Ausnutzung spezifischer thermoelastischer Effekte. Diese aktuell erforschte laseroptische Methode zur kosteneffizienten zerstorungsfreien Quantifizierung von Adhasionseigenschaften im geklebten Werkstoffverbund lasst sich ohne Probleme in den Produktionsprozess integrieren.

Within the European initiative OSACA (Open System Architecture for Controls with Automation Systems) a company-spanning open control architecture has been developed as of 1992. Since then the development of open control systems has continued until today. In 2008 a study was carried out with the objective to verify the results of 15 years of work for open control systems in Europe. It ought to identify especially the state of the art in the polled companies as well as their wishes and goals for the future. This article contains the most important results.

Modular system-based engineering is the key to a quick, customized machine and plant configuration. This approach is seen as the best method to implement different functional requirements with a minimum amount of resources. The interdisciplinary configuration of control systems to automate machines has previously not been supported by engineering tools. This is partially due to the lack of standardized mechatronic information models. The machine manufacturer is required to create the necessary mechatronic information models uniquely for each control system independently. Thus, he does not comply with any modeling specifications. As a result, the mechatronic information models are not applicable for other control system architectures. The conventionally used mechatronic information models as well as the manufacturer-specific engineering tools define the control hardware components and their configurations. An abstraction of the logical and functional layers does not take place. Consequently, a mechatronic control architecture model is required. This architecture can serve as a modeling basis in modular system-based interdisciplinary engineering tools. Therefore, an approach to a manufacturer independent, mechatronic information model for control systems is the subject of this article.

Nowadays, machining systems worldwide are on a very high level, regarding mechanics as well as control technology. Therefore, in the case of challenging sub-assemblies like drive and control systems and technological components (e.g. high-frequency spindles and processing heads) the emphasis should be placed on the integration of these components in specialised machine and plant configurations, especially by reducing the interfaces with a new communication system. In the future, technological innovations can be primarily expected from the introduction of highly integrated mechatronic machine modules. The concept of this new powerline communication system is the transmission of data and power for a drive unit over a common power cable. This can be achieved by high-frequency modulation of the data onto the cable. In this paper, the basic conditions for the industrial powerline communication are presented. First an overview is given on the existing communication systems in production technology. As an essential requirement the transfer function of the transmission channel is analysed. Further, the disturbances on the transmission channel are discussed. The final essential requirement is the compliance with the standards regarding elimination of disturbances, conducted as well as radiated. For proof of functionality the Orthogonal Frequency Division Multiplex- (OFDM-) transmission method is applied. This is implemented in two modems which have been set up within a demonstration system.

The preloading is a main characteristic for the functionality of a ball screw. The path of preloading during operation with no thrust load is an indicator for the actual inner forces, the friction produced by the ball screw and finally for the quality of the unit. Due to manufacturing tolerances the preloading over the useful travel of the ball screw differs from its specified value. However, not only the overall loading of a ball screw varies, but also the local load distribution within the nut. This is expressed by a periodic variation of the internal forces which has an effect on the alignment of the nut and therefore on the uniformity and the motion characteristics of a ball screw feed drive. The following paper deals with the occurrence of these periodic force variations and offers an explanation for this particular phenomenon.

Currently, the Institute for Control Engineering of Machine Tools and Manufacturing Units (ISW) has been researching and developing a universal concept for a redundant, failure-tolerant numerical control system. The results of this research project meet the increasing demands on the reliability of machines and plants and the frequent applications of numerical controls in safety critical areas. In this case, reliability means the capability of a numerical control to function according to its specification during the entire machining time. This is achieved by a redundant design and will be exhibited on a demonstrator, which is introduced in this paper.

In the product development process topology optimization can successfully be applied in the early product design stages. In this work a new penalization scheme for the SIMP-method (Solid Isotropic Material with Penalization) is presented. One advantage of the presented method is a linear density-stiffness relationship, which has advantages for self-weight or eigenfrequency problems. The optimization problem is solved through derived optimality criteria (OC), which is also introduced in this paper. The derived OC uses no sensitivities of the optimization function but is equivalent to the classical OC in the case of no penalization. In the case with penalization we present an objective function for the penalty factor. By maximizing the objective function in each iteration, we get an adaptive penalty factor. Numerical experiments show, that the adaptive penalty factor leads to better optimization results then a fixed penalty factor. The presented topology optimization method is implemented in the commercial FEM package ANSYS under the name TopoAD. One useful extension of TopoAD is the concept of “meta elements”, which is also presented in this paper.