| الوصف: |
U ovoj disertaciji istražena je klasa izravno pogonjenih hidrauličkih sustava upravljanih dvjema pumpama. Sustav je analiziran s aspekta regulacije položaja, energetske učinkovitosti te interneta stvari. Predložen je nelinearni dinamički model sustava, gdje su glavne nelinearnosti trenje u cilindru te protoci kroz proporcionalni ventil. Za regulaciju sustava predložene su četiri različite metode. Prve dvije metode odnose se na linearne regulatore, a to su ISA PID i LQR-I regulator. Iz nelinearne teorije upravljanja odabran je SMC regulator i metoda povratnog koraka. Za sve predložene upravljačke metode dobiveni su simulacijski rezultati za dvije sinusne pobude i jednu skokovitu. Dobiveni simulacijski rezultati usporedeni su sa simulacijskim rezultatima proporcionalnog elektrohidrauličkog sustava te eksperimentalnim rezultatima za oba sustava. Iz eksperimentalnih rezultata, koji su dobiveni za različita opterečenja, izračunato je šest parametara pomoču kojih se usporedivala statička i dinamička točnost sustava. Iz odziva sustava na sinusne pobude izračunate su pogreške u fazi i amplitudi te kumulativna pogreška sustava, dok je za skokovitu pobudu izračunato vrijeme porasta i vrijeme smirivanja odziva te kumulativna pogre_ska sustava. Pomoću navedenih parametara komentirana je statička i dinamička točnost sustava u odnosu na različite regulatore i klasični elektrohidraulički sustav. Energetska učinkovitost sustava izračunata je za različita opterečenja sustava i sve predložene regulatore. Dan je primjer seta mjerenih podataka iz kojih je izračunata energetska učinkovitost sustava kao omjer izlazne i ulazne energije sustava. Dobiveni rezultati međusobno su usporedeni za pojedine regulatore i sustave te su pokazali da je DDH sustav energetski učinkovitiji od klasičnog elektrohidrauličkog sustava. Sa stanovišta IoT-a predloženo je rješenje za udaljeni nadzor i upravljanje sustavom. Razvijen je model baze podataka i web aplikacija te su istraženi mrežni industrijski protokoli. Na kraju, dan je zaključak ovog rada te su predložene smjernice za daljnja istraživanja. In this thesis, comprehensive investigation of a class of direct-driven hydraulic (DDH) systems controlled by two pumps is carried out. The DDH system is investigated from the standpoints of control theory, energy efficiency, and the Internet of Things (IoT). A nonlinear dynamical model of the system is proposed, wherein the main nonlinearities in the proposed model are friction inside the cylinder and ow through the proportional valve. Four different methods have been proposed for solving of fixed and variable setpoint (dynamic trajectory) tracking problems. The first two methods are chosen from the linear control theory, and they are the ISA PID and LQR-I controllers. The SMC controller and backstepping control were chosen from the nonlinear control theory. Simulation results were obtained for the step and dual sine wave reference trajectory for all proposed control methods. Simulation results were compared with ones obtained for proportional electrohydraulic systems, and with experimental results for both systems. Six parameters were calculated from obtained experimental results for different cylinder payloads. Based on these six parameters, the static and dynamic accuracy of the system is evaluated and compared. From the results obtained for the sine wave reference trajectory, phase, amplitude, and cumulative control system error were calculated. The rise and settling time together with cumulative system error were calculated from system response to stepwise reference (setpoint) change. With given parameters, steady-state and dynamical accuracy of the system is evaluated for different control methods and compared to the classical electrohydraulic system. The energy efficiency of the proposed system was calculated for different cylinder payloads and proposed control methods. Energy efficiency has been calculated as the ratio of the output and input system energy based on a measured data set. The obtained results for proposed control methods are mutually compared for DDH and classical hydraulic systems. Results showed that the DDH system's energy efficiency is higher in comparison to the classical electrohydraulic system. From the aspect of IoT, a solution for remote system monitoring and control has been proposed. Web application and database model were developed while network-specific industry protocols have been investigated. Finally, the main contributions of this thesis have been summarized in the conclusion section, which has also given guidelines for further research. This thesis is organized in eight chapters, whose contents are outlined below. Chapter 1: Introduction. In this chapter, a detailed literature review on the topic of this thesis is presented. Motivation for this research is given alongside an overview of the previous work. Based on the detailed literature review, hypotheses and scientific contributions are defined. The outline of the thesis also provided herein. Chapter 2: Experimental setup. This chapter describes the experimental setup used to carry out all the tests presented in this thesis. Hydraulic schematics for proportional and DDH system are also shown. A detailed description of all used components is given along with their technical specifications. Chapter 3: Mathematical modeling. The nonlinear mathematical model of the system is derived in this chapter. First, the dynamical model of the hydraulic cylinder is given, incorporating the nonlinear LuGre friction model. Proportional valve dynamics are modeled as the second-order lag term while the flows through the valve are represented by a nonlinear static function normalized over the maximum range of the control spool movement. A proportional term with volumetric efficiency is used for describing the dynamical behavior of the gear pump. Finally, state-space models of the DDH and classical hydraulic system are given as fifth-order and seventh-order lag terms respectively. Chapter 4: Classical control methods. From the linear control theory, two control methods are chosen for solving of fixed and variable setpoint (dynamic trajectory) tracking problems. The first control method is widely used the ISA PID controller. The controller parameters are obtained with the Ziegler-Nichols method. Simulation results are given for the case of a fully loaded cylinder and comparison has been carried out between the classical system and DDH system through experimental results. For different proportional-integral-derivative (PID) controller structures experimental results are given and mutual comparison between individual PID controller types has been performed. Linear quadratic regulator (LQR) type state controller with integral action (LQR-I) is chosen as the alternative linear control method, with parameters for the proposed control method obtained from a linearized dynamic process model. Obtained experimental results indicated superior control performance (i.e. faster response and smaller control error) compared to the PID controller. Chapter 5: Nonlinear control methods. The sliding mode controller (SMC) and backstepping state-space controller are selected from the nonlinear control system methods in order to further improve set point accuracy and trajectory tracking ability. For both controllers, simulations are carried out and their results compared to those obtained for the classical system, as well as with experimental results for the fully loaded cylinder. In particular, the obtained experimental results show excellent response and tracking capabilities for sine wave reference input. For the case of step reference input signal, both controllers showed roughly the same transient dynamics and obtained similar results as ISA PID and LQR-I controllers. Chapter 6: Energy efficiency. In this chapter, the energy efficiency of the proposed system is investigated. The equations used for calculating the system power and energy are defined. For the cylinder velocity estimation, an algebraic approach is used to determine signal time-derivatives of arbitrary order. An example set of measured data from which energy efficiency is calculated is given for both the DDH and classical hydraulic system. Thus obtained results are mutually compared for both systems and different control methods used in this thesis. Finally, some general conclusion on energy efficiency have been given. Chapter 7: Remote system control and monitoring. An Internet of Things (IoT) solution for remote system control and monitoring is presented in this chapter. Firstly, a schematic representation of the proposed setup is given. Connections between programmable logic controller (PLC), human-machine interface (HMI), camera, web server and, user are defined and explained. A detailed literature review on industrial network protocols is also given herein. Modbus TCP protocol is chosen, as the most suitable protocol for communication between PLC and web server. A suitable database model is designed for continuous data logging and system overall monitoring, with the user administration database model is adopted from the Web2py framework. The developed web application is user-friendly and easy to use. It provides for sending the information to the PLC and monitoring of all relevant data in real-time, with easy integration of new systems being possible through the system administration page. Chapter 8: Conclusion. In this chapter main contributions of the dissertation have been listed, and all hypotheses are confirmed. Several recommendations are given for future research. |
