Samopodešavajuće prediktivno funkcionalno upravljanje temperaturom egzotermičkog šaržnog reaktora

In this paper we study a self-adaptive predictive functional control algorithm as an approach to control of temperature in an exothermic batch reactor. The batch reactor is situated in a pharmaceutical company in Slovenia and is used in the production of medicines. Due to mixed discrete and continuous inputs the reactor is considered as a hybrid system. The model of the reactor used for the simulation experiment is explained in the paper. Next, we assumed an exothermic chemical reaction that is carried out in the reactor core. The dynamics of the chemical reaction that comply with the Arrhenius relation have been well documented in the literature and are also summarized in the paper. Furthermore, the online recursive least-squares identification of the process parameters and the self-adaptive predictive functional control algorithm are thoroughly explained. We tested the proposed approach on the batch reactor simulation example that included the exothermic chemical reaction kinetic model. The results suggest that such implementation meets the control demands, despite the strongly exothermic nature of the chemical reaction. The reference is suitably tracked, which results in a shorter overall batchtime. In addition, there is no overshoot of the controlled variable (temperature in the reactor core), which yields a higher-quality production. Finally, by introducing a suitable discrete switching logic in order to deal with the hybrid nature of the batch reactor, we were able to reduce switching of the on/off valves to minimum and therefore relieve the wear-out of the actuators as well as reduce the energy consumption needed for control.U članku se analizira samopodešavajući algoritam prediktivnog funkcionalnog upravljanja kao pristup upravljanju temperaturom egzotermičkog šaržnog reaktora. Šaržni se reaktor nalazi u jednoj slovenskoj farmaceutskoj tvrtki gdje se koristi za proizvodnju medikamenata. Budući da su ulazi u rektor i kontinuirani i diskretni, reaktor je promatran kao hibridni sustav. U članku je opisan model reaktora korišten za simulacije. Nadalje, pretpostavljeno je da se u jezgri reaktora odvija egzotermička reakcija. Opis dinamike kemijske reakcije Arrheniusovim jednadžbama dobro je dokumentiran u literaturi, pa je u članku dan samo kratki pregled. Posebno detaljno opisana je metoda najmanjih kvadrata za procjenu parametara modela te samopodešavajući agoritam prediktivnog funkcionalnog upravljanja. Predloženi pristup upravljanju provjeren je simulacijom na šaržnom reaktoru koji uključuje kinetički model egzoterničke kemijske reakcije. Simulacijski rezultati ukazuju da predloženo upravljanje ispunjava tražene zahtjeve, unatoč jakoj egzotermičkoj naravi kemijske reakcije. Zadane su reference dobro praćene, što rezultira skraćenjem trajanja šaržnog procesa. Osim toga, nepostojanje nadvišenja u temperaturi jezgre reaktora osigurava veću kakvoću proizvodnje. Na koncu, uvođenjem prikladne logike prekapčanja za prilagodbu hibridnoj naravi šaržnog reaktora moguće je značajno smanjiti prekapčanje dvopoložajnih ventila što ima za posljedicu smanjenje njihova trošenja i uštedu u potrošnji energije

Smart workload input-output control of production systems:A proof of concept

Workload control (WLC) relies on order release (input control) and capacity adjustments (output control) to regulate manufacturing throughput times. Research concerning integrated input-output control is very scarce. A novel approach is proposed: a closed-loop integrated model, where automatic feedback control is added and where order release and capacity decisions are a continuous function of the shop floor current state. In existing models, capacity increments are triggered by a threshold utilisation and have a fixed value, defined by means of experiments. In the proposed approach, these values are dynamically and flexibly defined (by the controller), addressing a gap regarding input-output parameterisation. The model was applied to a shop with unidirectional flow and three control rules were tested in scenarios of unbalanced work in process (WIP) and demand fluctuations. The results showed that the simultaneous input-output control is effective, leading the system to restore WIP balance, reach stability and absorb demand fluctuations, especially when global information is provided to the controller. The results of continuous closed-loop model simulation were integrated into a discrete-event simulation (DES) model, to compare the proposed capacity policies with the policies presented in the literature. The comparison showed that the proposed policies are cost-effective for a reasonable throughput time reduction. Moreover, the closed-loop model provided good parameters for a step-increment capacity policy that minimizes throughput times. Closed-loop control models are responsive and prescriptive, in contrast to DES models used in WLC research, which are descriptive. With this approach, WLC research can benefit from the strengths of both methods.</p

Optimization of Fuel Consumption with Respect to Orbital Requirements for High Resolution Remote Sensing Satellite Constellations

Among applications of formation flying, several case scenarios for High Resolution Remote Sensing Satellite Constellations were proposed in the literature. For a radar interferometric system a pair of satellites has to be at two different positions that are separated by a distance of several hundred meters during measurement sequence. The satellites can be either in the same orbit or in a part of approximately parallel orbits. During imaging the relative separation of the satellites has to be stable and precisely known. In the case of an optical payload, one satellite can hold the optical lens system and the other the imaging sensors. The satellites must fly one over the other or one behind the other at a close range. In the paper, several manoeuvres for Satellite Constellations are analysed and simulated with the respect to fuel consumption. A linear model based on Hill-Clohessy-Wiltshire equations is solved analytically for the fuel consumption analysis. Linear models are optimised serving an approximate solution with respect to optimal fuel consumption respecting constraints, such as maximal disposable time and the instant of required formation position. Better results are obtained when orbit eccentricity is taken into account, as shown in the simulated examples

Validation of Astrodynamic Formation Flying Models against SPACE-SI Experiments with Prisma Satellites

In this paper several astrodynamical formation flying models are assessed against the experimental results derived from the SPACE-SI formation flying experiments performed in September 2011 with the OHB Sweden developed Prisma satellites Mango and Tango. In these formation flying experiments critical manoeuvres for three types of missions were investigated with respect to in-orbit performances. The experiments included parallel flying with in track displacement demonstrating high-resolution optical dual satellite imaging and radar interferometric constellation, circumvolution as well as encircling of the target demonstrating debris observation and parallel flying with the radial displacement demonstrating fractionated spacecraft and accurate pointing of the formation. The astrodynamic data of the experiment are used to verify several formation flying models including a nonlinear model, a linear Hill-Clohessy-Wiltshire model, STK models with four propagators (Earth mass point, J2, default HPOP and HPOP with all disturbances) and the hereby originally proposed extension to the Hill-Clohessy-Wiltshire model, a linear model for orbits with small eccentricities