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Stiction, a manifestation of friction that causes an object to stick in a position until a strong enough force is applied to cause the object to start moving, is a common nonlinearity in control valves in the chemical process industries that can cause set-point tracking issues and control loop oscillations. In this work, we initially investigate the cause of these issues to emphasize that they are...
In process industries, compressor plants provide process fluids with certain flows and pressures. The plant behavior may change over the entire life cycle due to component-specific time-variable factors. Control valves applied in compressor plants are affected by time-variable factors. Their modeling with consideration of specific time-variable factors is described in this paper. Control valves ensure...
Wireless technologies have been successfully applied in the process industry since the creation of the first international standard IEC62591 WirelessHART. Applications started in areas where wireless sensors provide rich process information to the automation systems. Although real and demonstrated control applications are advertised, wireless-for-control is still in the initial stage and faces a lot...
There is a class of control algorithms, which are based on models of the controlled processes. The common feature of these algorithms is the fact that at the design stage the algorithm can be modified to take into account multiple sensors available in the controlled plant. Each additional independent measurement increases the accuracy of the simulation carried on by the model embedded in the algorithm...
The automation of a chemical polishing plant is described. Basically sequential control tasks were applied. The valves and the pump were connected to the process interfaces traditionally and the process interface communicates with the PC via CAN bus. The control tasks, the visualization and the operation are performed by indicators and controls of the real-time graphical programming language LabVIEW...
In the modern process automation industry control valves with digital positioners have the ability to communicate with the process control system. Additional important functions (automatic start-up and control loop self-optimization, alarm signals, detailed fault diagnosis) lead to a process integrated maintenance and more process plant reliability. In this paper, these possibilities and a new diagnostic...
The main idea of plug and play process control is to initialise and reconfigure control systems automatically. In this paper these ideas are applied to a scaled laboratory model of a district heating pressure control system. First of all this serves as a concrete example of plug and play control, secondly some of the first techniques developed for these problems are demonstrated by experiments. The...
A cyber security incident in SCADA systems can cause the disruption of physical process, and may result in significant economic loss, environmental disasters or even human casualties. To exploit the feature of the physical process and find the potential attacks, this paper presents and analyzes a new class of cyber-physical attacks, named false logic attacks, against the logic of control process in...
Normally PID controller tuning rules are derived using linear models of the plant or process, with nonlinearities neglected. This factor often results in the deterioration of loop performance which is tuned using these rules. In the present paper, optimal tuning rules are derived based on a more accurate nonlinear model of the flow process, in which the nonlinearity of the pneumatic actuator (most...
In this paper, the Model Reference Adaptive Control (MRAC) with dead-zone compensation is proposed to improve two MRAC variations: MRAC with fixed adaptive gain (γ) and MRAC with variable γ based on η-adaptive optimization algorithm. The proposed MRAC is often used to compensate the dead-zone effect on valve that is not taken into consideration in the usual MRAC. It was also implemented a compensation...
The Small to Medium Enterprises (SMEs) precise more and more suitable systems to be automated. In this work is examined the possibility of programming a filling system, mixed and packaged of liquids automatic. PLC's are used for control. It is tried to make an integral automation taking into account the questions of rapidity and safety. A study is made on different possibilities in the packaging from...
The introduction of microprocessor-based plant control occurred shortly before 1980 with simple single-loop controllers. This technology quickly evolved into a DCS with control processor redundancy, high-density input/output systems, and a human machine interface (HMI). Today's tank management plans are faced with intense pressure to improve storage reliability. Thereby, current business goals focus...
This study proposes a selective compliant assembly robotic arm (SCARA) with two revolute joints for poultry deboning. The joints of the arm are based on two high performance rotary type hydraulic actuators. These actuators are operated by servo valves, which control hydraulic fluid flow and direction. A PID based independent joint control system is considered for controlling the position of each joint...
A simple method for detecting stick-slip fault of industrial digital positioners (control valves) in control systems is presented. Only the valve travel setting signal and the actual valve travel signal are required. These two signals are available in most industrial processes, such as DCS. Therefore, the proposed method can be applicable to a large number of digital positioners with digital positioner...
The design of the basic control of a chemical plant is mainly based on the P&IDs (pipe & instrumentation diagrams) of the plant. These diagrams, which are complemented by further documents, contain the information which is needed to specify the sensors, actuators, and the binary and continuous control functions in between to run the plant at steady state and to ensure its safe operation. In...
Double-seated control valves are used to a lot of industrial applications due to advantages of reduction in actuator force, a great flow capacity and a deal of slurry fluids. The authors have developed an innovative structure with a compact body carrying out smooth and stable controls. This paper describes a fluid mechanics study to completely suppress unstable behavior possibly induced even in an...
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