6 minute read
Path Following Robot
DALE CHETCUTI | SUPERVISOR: Dr Ingrid Vella COURSE: B.Sc. IT (Hons.) Artificial Intelligence
Recently, there has been an increase in the application of robotics to various areas, one of which is transportation. These include public transport and self-driving cars, which need to follow a predefined path. Path-following is a task that entails robots following a predefined path from a starting position to an end goal.
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This project set out to investigate different techniques that could be applied to a robot for following a predefined path. Additionally, the study has considered ways of rendering smooth movement.
The Lego Mindstorms EV3 Robot Educator was used for the experiment. A colour sensor was attached on the front of the device, aligned at the centre. The environment chosen for the experiment was a black path on a white background for maximum distinction (see Figure 1). The robot could identify whether it was on the black path or the white background, through the colour sensor.
The project considered three algorithms that are commonly used in path-following robots, and compared their performance on four different paths. The first approach used a proportional-integral-derivative controller (PID controller), which is commonly employed in similar projects, as it achieves smooth movement. The second approach applied Q-learning, whereby the robot would attempt to learn from its actions to navigate the predefined path efficiently. Thirdly, the fuzzy logic method was tested; this makes decisions based on a predefined set of rules.
To evaluate the performance of the algorithms, a marker was attached to the front of the colour sensor to trace the path followed by the robot, so as to compute the root-mean-square error (RMSE) between the predefined path and the actual path. Testing the three algorithms on the four different paths showed that all the algorithms achieved a low RMSE, with the PID controller yielding the smoothest movement (see Figure 2).
Figure 1. The robot following the predefined path Figure 2. The predefined path, and the path taken by the robot
Software Engineering & Web Applications Tools to construct the comparative analysis of existing medical portals
STEFANIA FARRUGIA | SUPERVISOR: Prof. Ernest Cachia COURSE: B.Sc. IT (Hons.) Software Development
Portals, which are made up of information sources, provide an interface offering a structured view of the data accessible to a user (see Figure 1). Nevertheless, there remain concerns about which factors contribute to long-term use of a portal. This project focuses on the development of medical portals that could provide the medical community with access to medical records through the web browser. Medical portals are considered to be a valid representative class of web portals, as the information they offer is by its nature large, non-trivial, and distributed. Furthermore, medical-patient portals draw their effectiveness from the extent of patient involvement they engender.
At a basic level, this project set out to define what a web portal is through functional and non-functional properties, and also defines various portal classifications. Moreover, the issue of portal usability and longevity was addressed with reference to the findings of previous researchers in developing these types of information products, coupled with a study of technologies required to construct portals, using medical portals as a representative case. By analysing previous studies, it was concluded that the most important characteristics when developing an effective portal were the level of maturity of the target users, portal usage and portal overall security.
By understanding the motivation for the use of portals, the project explored the application techniques, such as activity theory that seeks to comprehend human interaction through analysis of their activities to increase the effectiveness of portals. In the case of medical portals, studies have shown that activity theory is an effective tool for depicting the non-trivial nature of medical environments. For this reason, a system was developed through an activity-theory approach and implemented through the use of appropriate frameworks (see Figure 2). For portals to be accessible, they must be constructed in a manner that would make them simple to use, while always fulfilling both requirements and usage constraints.
Figure 1. The conventional web portal architecture Figure 2. A structured web portal implementing the activity-theory technique
TRISTAN Oa GALEA | SUPERVISOR: Dr Sandro Spina COURSE: B.Sc. (Hons.) Computing Science
This work outlines a grammar-based solution for the rapid modelling of building façades from images. The project involved a user-annotated image of a façade being interpreted by the system, which in turn encodes the positional relationship between the façade’s elements into an internal representation, known as a split grammar [1]. The latter was evaluated further to construct a hierarchical subdivision, producing a meaningful 3D model upon traversal (see Figure 1).
The main objectives of this project include: an automatic system for deriving split rules from a single annotated image; a procedural approach for modelling a façade from a given ruleset and a procedural approach for generating a random façade structure from all the previously encountered instances. Practical applications include: architectural model creation, simulation creation and large-scale urban modelling with building variations, benefitting architects, game designers and film-set designers alike.
In the same way that the structure of a language is often defined through its grammar, a building façade could be encoded as a context-free grammar - G(T, NT, R, S₀) - consisting of terminal (T) and non-terminal (NT) symbols, production rules (R) and a starting symbol (S₀) respectively. The terminal and non-terminal symbols together define the set of symbols acceptable by the system. Symbols in T represent the individual façade elements (i.e., regions in which further splitting is not possible), while those in NT correspond to any compound grouping of terminal regions. Production rules are a vital component of any grammar, as they specify ways in which non-terminal regions could be converted into terminal symbols. The chosen system defines split and conversion rules to achieve its goal, the two key qualities which distinguish a split grammar [1].
The proposed system has been designed to cater for the following façade elements: doors, windows, balconies, balcony doors and shop items (e.g., banners, posters, signs and shop windows). The user marks these features using a different coloured rectangle for each separate group. To help the system distinguish between the different floors, the user would also be asked to select the floors to be modelled. This initial interaction is beneficial for both parties because, while a user has full control of the floor-selection process, the system would be made aware of the elements pertaining to each chosen floor.
A recursive splitting algorithm evaluates each floor region to determine the positional arrangement of all the façade elements falling within the current scope. This creates the production ruleset, which is the set of rules that uniquely define a façade structure. From these rules, an abstract syntax tree is constructed. This hierarchical data structure converts the scope-based positional relationship between elements in the same region to geometric information pertaining to the global scope. Finally, a depth-first traversal of this tree would lead to the construction of a 3D model.
The outcome of the project suggests that procedural modelling of façades from images is possible through the creation of deterministic split grammars, which uniquely encode single façades. On the other hand, the procedural modelling of a random building is achievable through the construction of a stochastic split grammar, which encodes all previously encountered variations [2].
Figure 1. An annotated façade image is given as input (top left); the system constructs a split grammar (bottom left) from which an abstract syntax tree is generated (centre) to produce a corresponding 3D model (right)
REFERENCES
[1] P. Wonka, M. Wimmer, F. Sillion and W. Ribarsky, “Instant architecture”, ACM Transactions on Graphics, vol. 22, no. 3, pp. 669-677, 2003.
[2] F. Wu, D. Yan, W. Dong, X. Zhang and P. Wonka, “Inverse Procedural Modeling of Facade Layouts”, ACM Transactions on Graphics, vol. 33, no. 4, pp. 1-10, 2014.
