A hybrid backtracking algorithm for automatic test data generation

Kao osnovno pitanje u ispitivanju softvera, automatsko generiranje podataka za ispitivanje je od najveće važnosti, što je u biti problem zadovoljavanja ograničenja, a rješava se algoritmima pretraživanja. U našem prethodnom istraživanju za rješenje ograničenja predložena je metoda grananja i ograničavanja, a elaborirane su unaprijedne metode. Zasnovan na intervalnom aritmetičkom i simboličkom izvršenju, ovaj je rad usredotočen na unatražnu metodu, a to je povezivanje unaprijednog provjeravanja i unatražnog ispitivanja usmjerenog konflikta, u cilju poboljšanja učinkovitosti unatražnog praćenja u postupku traženja. Zatvaranja varijabli se koriste kako bi se olakšalo lociranje nesuglasica koje dovode do neriješenih rezultata (dead ends). Empirijski eksperimenti dokazuju učinkovitost predložene hibridne unatražne metode i njenu primjenljivost u inženjerstvu.As a fundamental issue in software testing, automatic test data generation is of crucial importance, which is essentially a constraint satisfaction problem and solved by search algorithms. In our previous research, branch and bound was proposed as our constraint solver and the look-ahead methods were elaborated. Based on interval arithmetic and symbolic execution, this paper focuses on the look-back or backtracking method, which is the hybridization of forward checking and conflict-directed backjumping, with the aim of improving the efficiency of backtracking in the search procedure. The closures of variables are used to facilitate the localization of the conflicts which cause dead ends. Empirical experiments prove the effectiveness of the proposed hybrid backtracking method and its applicability in engineering

Hybrid type multi-robot path planning of a serial manipulator and SwarmItFIX robots in sheet metal milling process

This work investigates on the coordinated locomotion between a ceiling-mounted serial manipulator and two SwarmItFIX robots. The former holds the machining tool as an end effector, and the other two robots act as swarm robotic fixtures in a sheet metal milling process. A novel offline coordination planner which follows the hierarchical based hybrid type decentralized planning strategy has been proposed. Motion of the serial manipulator and SwarmItFIX robots’ coordinated locomotion are divided into three sub-problems, viz, trajectory planning of serial manipulator, task planning of SwarmItFIX robots, and homogenous prioritized multi-robot path planning of SwarmItFIX robots. Mathematical formulation of all the three sub-problems is developed and presented in this paper. A hexagonal segment that fits inside the boundaries of the workspace is considered as the machining trajectory. The tool velocity is assumed to be constant as it improves the quality of machining. The results obtained from the proposed planner is found to be efficient as the task planning module has computed the precise support locations and support duration for the SwarmItFIX robots. The multi-robot path planning module of the planner computes the optimal collision-free paths of SwarmItFIX robots for all goal positions. Finally, trajectories of SwarmItFIX robots are found to be completely in-line with the trajectory of tool center point (TCP) of the serial manipulator

Modelska ispitivanja popustljivosti kontakta tangencijalno opterećenih veza različite makro geometrije u uslovima dinamičkih opterećenja

REZIME: U okviru doktorske disertacije sprovedena su modelska ispitivanja popustljivosti tangencijalno opterećenih veza različite makro geometrije u uslovima dinamičkih opterećenja. Veliki broj elemenata kod savremenih mašinskih sistema ima funkciju da obrazuje rastavljivu vezu koja onemogućava ili ograničava relativno kretanje elemenata. Tangencijalno opterećene rastavljive veze elemenata mašinskih sistema spoljašnje opterećenje uravnotežavaju preko napona nastalih u zonama kontakta elemenata. Pojava tangencijalnih i normalnih napona u zonama kontakta pomenutih elemenata dovodi do relativnog pomeranja elemenata. Nastalo pomeranje i veličina tangencijalnog opterećenja kontakta definiše popustljivost kontakta određenog tipa veze. Istraživanja ove doktorske disertacije usmerena su na optimizaciju kontakta sa aspekta povećanja nivoa tangencijalne nosivosti kontakta i smanjenja popustljivosti kontakta u uslovima malih lokalnih deformacija zona kontakta bliskih vrhovima neravnina kontaktnih površina. Pored navedenog doktorska disertacija razmatra i uticaj sredstva za hlađenje i podmazivanje koje se nalazi unutar kontaktne zone na popustljivost kontakta. Ispitivanja su dovela do razvoja novih tipova kontaktnih elemenata, a sprovodena su upotrebom specijalno dizajniranog pribora za ispitivanje popustljivosti tangencijalno opterećenih veza različite makro geometrije u dinamičkim uslovima. Sprovedene analize primenom metode konačnih elemenata ukazuju na primenljivost predloženih ideja, dok su eksperimentalna istraživanja dovela do rešenja makro geometrije stezača/oslonca koji u odnosu na postojeća rešenja poseduje znatno veću tangencijalnom nosivost i manju popustljivost. Analiziranjem sprovedenih eksperimentalnih istraživanja jasno se uočava da prisustvo sredstva za hlađenje i podmazivanje utiče na smanjenje tangencijalne nosivosti, odnosno na povećanje popustljivosti unutar kontaktne zone.ABSTRACT: This doctoral disseration contains model examination of compliance tangentially loaded contact elementswith different macrogeometrics in dinamic conditions. A large number of elements in modern mechanical systems have the function to form a detachable connection that prevents or restricts the relative movement of an element.The tangentially loaded detachableconnections of the mechanical elements balance the externall load with stress generated in the contact zones of the elements. The occurrence of tangential and normal stress in the contact zone creates the relative movement between contact elements. The resulting movement and the size of the tangential load of the contact define the contact compliance of the certain connection type. The research of this doctoral dissertation is focused on optimizing contact from the aspect of increasing the level of tangential load and reducing the level of compliance in conditions of small local deformation in contact zones. In addition to the above mentioned, in this doctoral dissertation we are considering the influence of the cooling and lubricating fluid located within the contact zone on the compliance of the contact elements. The conducted experiments led to the development of new types of contact elements, and were carried out using specially designed equipment for testing the compliance of tangentially loaded connections with different macrogeometrics in dynamic conditions. The analyses carried out using the finite element method indicate the applicability of the proposed ideas, while the experimental research has led to the solution of the macro geometry of the clamp / support which, in relation to the existing solutions, has considerably higher tangential load and less compliance. By analyzing the conducted experimental research it is clearly noticed that the presence of a cooling and lubricating fluid influences the increase in compliance within the contact zone