Toma Udiljak

Tool wear estimation using an analytic fuzzy classifier and support vector machines

A new type of continuous hybrid tool wear estimator is proposed in this paper. It is structured in the form of two modules for classification and estimation. The classification module is designed by using an analytic fuzzy logic concept without a rule base. Thereby, it is possible to utilize fuzzy logic decision-making without any constraints in the number of tool wear features in order to enhance the module robustness and accuracy. The final estimated tool wear parameter value is obtained from the estimation module. It is structured by using a support vector machine nonlinear regression algorithm. The proposed estimator implies the usage of a larger number and various types of features, which is in line with the concept of a closer integration between machine tools and different types of sensors for tool condition monitoring.

Drill wear monitoring in cortical bone drilling

Medical drills are subject to intensive wear due to mechanical factors which occur during the bone drilling process, and potential thermal and chemical factors related to the sterilisation process. Intensive wear increases friction between the drill and the surrounding bone tissue, resulting in higher drilling temperatures and cutting forces. Therefore, the goal of this experimental research was to develop a drill wear classification model based on multi-sensor approach and artificial neural network algorithm. A required set of tool wear features were extracted from the following three types of signals: cutting forces, servomotor drive currents and acoustic emission. Their capacity to classify precisely one of three predefined drill wear levels has been established using a pattern recognition type of the Radial Basis Function Neural Network algorithm. Experiments were performed on a custom-made test bed system using fresh bovine bones and standard medical drills. Results have shown high classification success rate, together with the model robustness and insensitivity to variations of bone mechanical properties. Features extracted from acoustic emission and servomotor drive signals achieved the highest precision in drill wear level classification (92.8%), thus indicating their potential in the design of a new type of medical drilling machine with process monitoring capabilities.

A Test Bed Model of an Advanced Handheld Bone Drilling System.

Modern medical drilling systems utilized in bone and joint surgery are characterized with relatively low level of automation, i.e., with no process monitoring and/or adaptive control characteristics, which could potentially prevent mechanical and thermal bone damages. The quality of the drilling process depends solely on the operator skills and tool characteristics. Therefore, a group of research activities have been focused to the development of an advanced next generation hand-held drilling machine. It should provide mechanical and thermal monitoring capabilities of the tool and bone, automated tool feed movement with potential implementation of high-speed drilling regimes, as well as the application of an advanced adaptive control algorithms for cutting forces and drilling temperature limitation. The system would reduce human influence in drill guidance by allowing operator to define drilling location and desired tool direction/angle, while all other activities would be performed autonomously by the machine monitoring and control system. The test bed platform of such system which will be used in the final prototype shaping is presented in this

Non — Contact Volumetric Measurement for Spine Evaluation and Production of Spine Orthotics

Today it is possible to measure human body with completely non-invasive devices [1,2,3,4] but there is no widely used method for quick, accurate and non-invasive evaluation of spine.[5,6,7,8]. Another problem is the fact that such patient should be transported in some specialized center where the appropriate therapeutic solution could be obtained, and where there are technical and medical resources. This work presents the idea, already supported with published work of other authors, of using 3D optical scanning system for evaluating of spine deformities and asymmetry. Considering the fact that commercially available devices for 3D scanning are very expensive, the possibility to scan human body with cameras from several directions and make the reconstruction of body shape seems very promising and competitive. The reconstructed model can be measured with the computer aid which gives tool for quick and quality follow up of shape change through time, and comparison before and after applied therapy. The system could also offer a possibility to design and produce high quality spine orthotics, or highly comfortable and individually adjusted spine supports.