This paper presents a position control approach based on an integrator state correction that allows for improving the positioning accuracy during the tuning of an adaptable gravity compensation. It comprises a variable reluctance actuator with a tunable electropermanent magnet (EPM), which provides gravity compensation forces ranging from 0 to 25 N with minimal power consumption. The proposed integrator state correction reduces the positioning error during the EPM force tuning and enables continuous and accurate positioning of the magnetically levitated mover position while maintaining an energy optimal operating point. The positioning accuracy of the zero-power magnetic levitation system is improved up to factor of 10 in comparison to conventional PID control. The proposed MAGLEV system enables highly efficient positioning for high-precision applications.

This paper proposes a pose estimation approach of an industrial six-degree-of-freedom robot without the need of externally placed sensors. An RGB-D camera that is placed at the robots end-effector is combined with a SLAM algorithm to act as a sensor system. The presented system based on the novel integration approach is evaluated by performing test trajectories and is capable of estimating the tool-center point with a standard deviation of 2.6 mm and performing a joint state estimation with a standard deviation of 13.6 mrad without any external sensor.

Depth-data-based sensor systems, such as depth cameras or LiDAR systems, are gaining popularity in the field of robotics, especially in human-robot collaboration. To avoid collisions with humans or external objects, object detection and tracking in the workspace is needed. This paper presents an integrated object cluster tracking and velocity estimation method that is purely based on depth data. Therefore, a tracking heuristic based on similarity and the velocity of the object is used to enable the tracking of external objects. To obtain the velocity, a Kalman filter utilizing a constant velocity model is implemented. For experimental verification, a case study comprising two objects moving within the robot workspace is designed. The experimental setup allows for the initial tracking a maximal trackable object velocity of 9 m s −1, and for already tracked objects a velocity deviation of 3.4 m s-1 to correctly track both repetitive and arbitrary motions of the test objects, and thus constitutes the proposed integrated object cluster tracking approach as a foundation for collision avoidance strategies in robotic tasks.

The measurement of external forces in Collaborative Robots (Cobots) is commonly realized by dedicated sensors in the joints. Since the use of these sensors is cost-intensive and reduces the stiffness of the manipulator, alternative approaches are needed. This paper presents a sensing principle for measuring external forces acting on a robot arm using a generalized momentum observer. The proposed approach does not require dedicated force/torque sensors and relies on measurements available in standard robot joints. The presented method estimates the external forces based on motor current measurement and joint torsion measurement. Both measurements are implemented and compared against a dynamometer in terms of accuracy. Depending on the joint, an RMS error within 2% to 4% of the dynamometer measurement can be achieved.

IEC 61499 is currently explored at a rapid pace, although only few studies were conducted on the role of FPGAs for automation systems based on IEC 61499. With the necessary time quantization for synchronous FPGA systems, a new problem arises – the phenomenon of simultaneous events. Additionally, fan-ins of events complicate the requirements for the system, as it must be ensured that all arriving events are considered. This work proposes an implementation for concurrent events for FPGAs in the context of IEC 61499. To overcome the described problem, the incoming events are split into several single bit signals and are stored in a ring buffer. The proposed approach is verified in simulations of typical situations, testing the behavior of the system with respect to simultaneous events.

Today's markets are short-lived and volatile. The producing industry needs to be able to react fast and cost-effective to product and process changes. Following the trend of Industry 4.0, current automation systems are designed as Cyber-Physical Production System (CPPS), which main properties are the distribution of capabilities and strict modularization to enhance reuse of off-the-shelf automation components. The currently dominant Programmable Logic Controller programming standard IEC 61131 was conceived with mainly centralistic systems in mind, which limits its use for nowadays CPPS scenarios. Focusing on the software aspect, the contribution of this work is an enhanced hierarchic development approach for automation systems, which aims to decouple all hardware from the control flow logic of an automation system for combined IEC 61131 and IEC 61499 systems. Therefore, a migration path for IEC 61131 Function Blocks into the development model of the event-driven IEC 61499 is presented, and issues are discussed. Both approaches pay special attention to the reusability of software.

Automation system engineering becomes more complex, due to the trend toward more flexible, reconfigurable, and modular design approaches, like Industry 4.0. For the modeling and design of the according software, two standards are present: IEC 61131-3 and IEC 61499. In order to satisfy the requirements for modern, large scale, highly distributed applications while also supporting still existing legacy systems, the demand for a combined development framework arises, where the best of breed tool can be chosen for a given automation task. Considering that, the IEC 61499 model is extended to allow the dual development and execution of IEC 61131-3 programs, and enabling easy and correct interaction between the two paradigms. In order to verify the validity of the chosen approach, an IEC 61499 development tool and a runtime environment is modified to support IEC 61131-3. A sample application is implemented, which comprises a pure IEC 61131-3 part with a 1 ms cycle time, a pure IEC 61499 part, and a part with interaction between both subparts, in order to evaluate possible interference between the runtime parts. Experimental results show that no interference is occurring, and the chosen development approach allows the seamless integration of IEC 61131-3 and IEC 61499 in one combined development framework.

This research focuses on an adaptive control method for a pulling motion of a fibril. From the viewpoint of the biotechnology, analyses of a mechanical characteristic of a fibril are important. For the analyses, the pulling motion of the fibril is conducted by a piezoelectric actuator with a cantilever. The fibril is attached at the tip of the cantilever, and is pull by the piezoelectric actuator. By this pulling motion, it is possible to measure the mechatronic parameters of the fibril. During the pulling motion, the mechatronic parameters of fibril are changed due to the pulling force. Therefore, it is hard to conduct the pulling motion at the desired force command such as the constant force. From this view point, this paper proposes the adaptive control method based on the recursive least squares algorithm (RLS). These mechanical parameters are estimated in real-time by RLS. By using these estimated parameters, the position command to achieve the force command is calculated. In the simulation, the proposed method is implemented, and the pulling motion with the contact force is simulated. The validity of the proposed method is confirmed from the simulation results.

The IEC 61131-3 and IEC 61499 standards are currently used to implement automation systems. Although aspects as reuseability, execution models, and component-based design have been discussed and analyzed for both standards, the programming effort and complexity of implementation for typical tasks in industrial automation have not been compared so far. This work proposes two typical application classes of industrial automation systems and implements one concrete application for each class with IEC 61131-3 and IEC 61499, respectively. Both implementations are then evaluated via McCabe's Cyclomatic Complexity and Halstead software measures, providing an objective comparison on the implementations.

In this paper, a framework for the automatic generation of redundancy-free interlock code is proposed. The core component is represented by an ontology-based integration framework that holds the relevant information from a developed piping and instrumentation diagram (P&ID) editor as well as the PLC program where the interlocks should be added. The integration framework is mainly based on AutomationML concepts as glue model between the different internal models of the P&ID editor and the PLC programming tool. In order to enable the coexistence of manual and automatically generated interlocking code, the approach is extended by additionally applying a theorem prover. Here, the theorem prover Z3 is utilized to eliminate redundant interlock logic whereas the redundancy-free logic is then automatically added as interlock code to the IEC 61131-3 compliant program. The framework is evaluated by application to a laboratory process plant.

In this paper, a framework for automatic generation of a flexible and modular system for fault detection and diagnosis (FDD) is proposed. The method is based on an ontology-based integration framework, which gathers the information from various engineering artifacts. Based on the ontologies, FDD functions are generated based on structural and procedural generation rules. The rules are encoded as SPARQL queries which automatically build logical segments of the entire manufacturing system in the ontology, assign sub-processes to these segments, and finally generate the appropriate FDD system for the sub-process. These generated modular FDD functions are additionally combined in a modular way to enable the fault detection and diagnosis of the entire system. The effectiveness of the approach is demonstrated by a first application to a conveyor system.

In this paper, an implementation approach for norm-optimal iterative learning control (ILC) on programmable logic controllers (PLCs) is presented. After a detailed conceptual overview and discussion of the norm-optimal ILC algorithm, the challenges for implementing ILC algorithms on PLCs are discussed and an efficient three-phase implementation approach is proposed. Here, the three phases consist of an offline calculation, the calculation of the feedforward part between consecutive iterations, and the online calculation of the current control input. It is also shown that this separation enables the efficient implementation of the norm-optimal ILC algorithm on standard industrial controllers like PLCs. The proposed norm-optimal ILC implementation approach is verified by a simulation of a gantry robot with three degrees of freedom, where the norm-optimal ILC algorithm is executed within a Soft-PLC.

The demand for flexible automation architectures in industry is raising, due to the trend to individualized products and the shortening of product life-cycles in general. Current approaches in automation systems are either only suited for a small range of processes or are only reprogrammable by software and automation experts. The presented domain specific language based approach decouples production-domain concerns from the automation program, by separating the process description into a specialized domain language. This domain language can be used by plant owners and domain experts to define and execute vastly different processes, as long as the needed process steps are supported by the actual automation system. This contribution demonstrates the development of a domain-centric SOA-based batch process automation system, by creating a directly executable DSL based on domain terms found in ISA-88.

In this paper, an ontology-based approach to automatically generate control applications to handle diagnostic information of decentralized control devices is presented. Diagnostic possibilities of modern remote I/O devices are analyzed and software components in terms of function blocks to handle the specific diagnostic information are defined. After a detailed conceptual overview, the application of the proposed knowledge-based code generation approach to a PLC-based control architecture of a hot rolling mill is described. It is shown that the proposed approach significantly reduces engineering time and the error rate in the design processes of industrial control and diagnostic applications, since the application engineering is raised to an abstract level by utilizing pre-defined, tested, and reusable function blocks and a user-definable set of code generation rules to encode repetitive implementation tasks. The rules are defined in the query language SPARQL with additional ARQ functions to reduce the complexity.

The objective of this paper is to propose a methodology for strictly separating fault detection and fault handling methods from control code in discrete manufacturing systems. In order to enable the separation, two different design patterns are elaborated. Based on an analysis of typical faults in manufacturing systems, a library of reusable function blocks for fault detection, handling, and also fault recovery is developed. These function blocks are implemented according to the international standard IEC 61499 and are applied within the design patterns. The design patterns are evaluated with the sequential control of an injection molding machine. It is shown, that the design patterns simplify the engineering and the separation of the fault detection and fault handling from control code significantly, since they provide clear design rules. Applying the proposed design patterns reduces the complexity of industrial control applications drastically. Furthermore, the function block library provides reusable and proven fault detection and fault handling methods.