This article presents the explanation of higher than expected increase of stiffness of coupled robots in some geometric configurations against its expected simple addition. This phenomenon was named the vault principle for robots. In order to achieve that and to explore fully the consequences it was necessary to develop a new method for robot stiffness analysis. Single serial robot is compared with two serial robots mutually connected. Connected (coupled) robots are analyzed in five various topological configurations. The end effector stiffness field is evaluated at particular points of intersections of workspaces of five topological configurations in order to preserve the objectivity of the comparison. The new method for robot stiffness analysis is based on the evaluation of minimum/maximum values of principal axes of stiffness distribution determined by the singular value decomposition. The manimum/maximum values across the workspace are processed by average/median and used for computing homogeneity factor. It is a new integral criterion for robot topology configuration judgment. The direct implications of these findings are relevant to high-precision milling applications in cooperative robotic setups.

Position control of the mechanical structure with naturally limited stiffness is a common problem. Moreover, the system is usually exposed to random exciting by the external force effects and yet it is needed to hold the system in the desired position. Such an example in engineering practice can be the machine tool quill slim structure, which determines the machining accuracy and the machined surface quality. The limited structure stiffness can be overcome by suitable support structure solution. In principle, it is a matter of introducing the necessary force effect in the place where it is necessary to ensure the required position. A promising means how to apply control force to the flexible structure tip can be a thin cable structure with the force actuation and proper force control. The resulting system is characterized by increased stiffness achieved in a mechatronic manner. Therefore, the introduced concept is called mechatronic stiffness. The article describes selected mechanical arrangement of the mechatronic stiffness concept, its features, behaviour and control results. The proposed approach offers a solution for precise position control of the flexible structure. An experimental device was created in parallel with the simulation experiment and preliminary simulation results are obtained. The described concept is transferable to other flexible structures such as various manipulators.

The paper deals with the enhancement of the robotic arm calibration using corrections based on local linear neuro-fuzzy models. After the standard calibration of the geometric parameters in the robot's kinematic model, there are still residual errors between the measured positions and the positions predicted by the model. The source of these errors are various non-geometric parameters and nonlinear phenomena that traditional kinematic calibration models do not include. The neuro-fuzzy model based on a locally linear model tree can approximate the residual error as a function of the robot's joint angles. Adding this approximation to the output of the calibrated robot model significantly increases the accuracy of the endeffector position. The results of the described method were verified and compared with other approaches on a simulation model of a flexible planar two-link mechanism. Experimental verification was performed on an industrial robot Stäubli TX200 with data measured by Leica laser tracking device.

This work deals with the control of flexible structures as underactuated systems. The invariant control method performs the control of a flexible robot as a representative of an underactuated system with zero dynamics. The control input is separated into two parts. The arbitrary part of the control input is designed to control the directly actuated part of the dynamic system. The invariant part of the control is selected to steer the system zero dynamics in the desired way. The harmonic functions create the base for the invariant part of the control function. The residual vibration cancellation is the target of the presented invariant control strategy. The harmonic function frequencies are overtaken from the so-called natural motion, amplitudes are the results of the optimization process. The main target of this paper is to show the invariant control approach and its application to the system with flexible elements.

Undesired vibration is a common issue when dealing with manufacturing machines, especially when dealing with thin structures. To decrease the external disturbance sensitivity of such systems, represented for example by machine tool quill, the auxiliary cable structure is attached to the system. The auxiliary cable structure increases system damping and decreases undesired structure vibrations by the passive or active way, depending on the deployment and purpose. In this article, cables are attached to the end-effector to suppress undesired vibrations and related experimental stand is prepared. Experimental stand parameters are identified using least square method. The control strategy using pole placement is presented and its suitability is verified using external disturbance force. The frequency analysis shows the promising behaviour of controlled cable structure attached to the original system as well as the experimental results.

Dry machining is one of the main ways to reduce the environmental burden of the machining process and reduce the negative effect of the cutting fluid and aerosols on operators. In addition, dry machining can reduce overall machining costs and, in the case of large workpieces, reduce the extra work associated with removing residual cutting fluid from the workpiece and adjacent area. For high-strength structural steel products, it is typical to drill holes with larger diameters of around 20 mm. Therefore, this work is devoted to the investigation of the dry drilling process carried out on a workpiece made of S960QL steel with a helical drill with a diameter of 21 mm. The aim was to find suitable cutting conditions for dry drilling with regard to process stability and workpiece quality. An experiment performed with a coolant served as a comparison base. A dry drilling experiment was performed with cutting speeds from 30 to 70 m·min−1 and feeds from 0.1 to 0.3 mm·rev−1, and with the results of this experiment, the same experiment with flood cooling was performed. During the drilling process, spindle torque values were recorded using the indirect spindle current recording method. The macroscopic chip morphology was studied to understand the cutting process. The chip thickness ratio was measured, as well as the maximum diameter of spiral chips. On the final workpiece, the qualitative and dimensional parameters of the holes were evaluated, such as the diameter, cylindricity and surface roughness, depending on the change in the cutting conditions and cutting environment. Evaluation of the obtained data led to the following conclusions. When drilling the S960QL material, there is only a very small increase in the drilling torque during dry drilling compared to drilling with cutting fluid. The increase in friction demonstrated by the chip thickness coefficient is significant. The influence of the environment on the dimensional accuracy showed a tendency for a slight increase in the holes’ diameters during dry machining. In comparison, the cylindricity of the dry-drilled holes shows a lower deviation than the holes drilled with cutting fluid. The surface roughness of the holes after dry drilling is affected by the increased friction of the outgoing chips, despite the resulting parameters being very good due to the drilling technology standards. This work provides a comprehensive view of the dry drilling process under defined conditions, and the results represent suitable cutting conditions to achieve a stable cutting process and a suitable quality of drilled holes.

This paper focuses on the implementation of principles of Industry 4.0 concept to ceramic industry. The topic of this paper is to address the problematics of the implementation of processes and elements of digitization within the Industry 4.0 concept into ceramic industry. Firstly, thorough literature and bestpractice research will be discussed. Based on the state of current knowledge, concept of the Industry 4.0 Readiness Model for Refractory will be presented. The model’s main focus is on the readiness of current business structures, processes and technical and economical situation. It will provide necessary analysis and insight into potential company’s processes and background. Based on this analysis, it will be possible to define the main obstacles for future digitalization and automation within Industry 4.0 concept in Refractory industry. On the foundation of data obtained by Industry 4.0 Readiness Model for Refractory, it will be possible to implement the Industry 4.0 solutions with highest added value to specific company, based on its current state. The main purpose of this paper is to summarize and discuss key parameters and framework for Industry 4.0 Readiness Model for Refractory and its connection to future implementation of Industry 4.0 features within ceramic industry.

This article deals with automation of dimensional control on Coordinate Measuring Machine using a collaborative robot. Thanks to the dimensional control automation, it is possible to save staff capacity as well as to increase the repeatability and productivity of component measurement in series production. Within the design and implementation of the workplace, the subject of inspection was chosen. Necessary equipment of workplace and variants of workplace layout were designed for the inspected part. The part of workplace realization was also to create a robot program to fully automate the process, including product placement and placement after component inspection, depending on the measurement result. The result of the project was an automated inspection of components, which could be implemented with minimal modifications to the real manufacturing system.

This paper presents a new dynamic inflation experiment method for identifying the viscoelastic parameters of blood vessels and grafts. The material parameters are estimated only from the recorded damped natural pressure oscillation and from the initial geometry of the tested specimens. The identified parameters are dynamic compliance, the damping ratio, fictitious fluid viscosity, frequency, and, for tubular samples, the elastic incremental modulus and the wall viscosity. Several experiments with latex tubular samples were performed to check the suitability of this unique experimental method, and to estimate the limits of its applicability (effects of operational parameters, e.g. the geometry of the samples and the viscosity of the working fluids).

The motivation for this work is the control of flexible mechanical systems, specifically their position control without residual vibrations. The actuators are attempting to position the “important point” at the far end of the flexible system through wave based control to eliminate the vibrations at the end of the motion. The synchronous electric generator is modelled as flexible mechanical system. The wave-based control method is presented. The paper shows how to compute and use the “launch” and “reflected” waves for control. If appropriate strategy is used, the flexible system will be displaced to the required position with no residual vibrations. If the superposition principle is valid, various motions can be controlled simultaneously. The state feedback control is shown for comparison.

This paper deals with a concept of mechatronic stiffness applied to branched mechanical structures. It is based on the introduction of auxiliary structure that functions as a support for embedded actuators. Feedback control enables significant increase of a dynamic stiffness of the original mechanical structure around its eigenfrequencies. The system is controlled by state space and state derivative controllers synthesized by LQR approach. Presented concept aims at machine tools where mechanical compliance is a major obstacle.