2015 23rd Mediterranean Conference on Control and Automation (MED), 2015
This paper presents the control of a master-slave system for teleoperated needle insertion under ... more This paper presents the control of a master-slave system for teleoperated needle insertion under guidance by Magnetic Resonance Imaging (MRI). The primary aim of our research is the robot-assisted laser ablation of liver tumors. The master-slave system consists of a master unit that sits next to the operator, outside the scanner room, and of a slave unit located inside the cylindrical MRI scanner. The needle insertion force is measured with a specially designed fiber optic force sensor mounted on the slave unit. Pneumatic actuation is employed in both master and slave in order to minimize the interference with the MRI environment. Accurate position control of the slave unit is achieved with a Time Delay Control scheme (TDC). Differently from previous designs, the force feedback on the master unit is provided by an adaptive controller that compensates the friction of the pneumatic actuator. The advantages over a baseline force controller are demonstrated with experiments on silicone rubber phantoms.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2017
A normal conducting 805 MHz test cavity with an in built button shaped sample is used to conduct ... more A normal conducting 805 MHz test cavity with an in built button shaped sample is used to conduct a series of surface treatment experiments. The button enhances the local fields and influences the likelihood of an RF breakdown event. Because of their smaller sizes, compared to the whole cavity surface, they allow practical investigations of the effects of cavity surface preparation in relation to RF breakdown. Manufacturing techniques and steps for preparing the buttons to improve the surface quality are described in detail. It was observed that even after the final stage of the surface treatment, defects on the surface of the cavities still could be found.
Applications in engineering manufacture, such as dimensional inspection, often require triangulat... more Applications in engineering manufacture, such as dimensional inspection, often require triangulation of large sets of measured 3D data. The CAD models of relevant complex parts are usually defined using trimmed NURBS (non-uniform rational B-spline). With such situations in mind, the paper proposes a new triangulation procedure which achieves high efficiency and robustness by utilising the CAD model as an available
Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 1997
Accurate dimensional inspection and error analysis of free-form surfaces requires accurate regist... more Accurate dimensional inspection and error analysis of free-form surfaces requires accurate registration of the component in hand. Registration of surfaces defined as non-uniform rational B-splines (NURBS) has been realized through an implementation of the iterative closest point method (ICP). The paper presents performance analysis of the ICP registration method using Monte Carlo simulation. A large number of simulations were performed on an example of a precision engineering component, an aero-engine turbine blade, which was judged to possess a useful combination of geometric characteristics such that the results of the analysis had generic significance. Data sets were obtained through CAD (computer aided design)-based inspection. Confidence intervals for estimated transformation parameters, maximum error between a measured point and the nominal surface (which is extremely important for inspection) mean error and several other performance criteria are presented. The influence of sh...
International Journal of Biomechatronics and Biomedical Robotics, 2015
This article presents the design and control of a pneumatic needle positioner for laser ablation ... more This article presents the design and control of a pneumatic needle positioner for laser ablation of liver tumours under guidance by Magnetic Resonance Imaging (MRI). The prototype was developed to provide accurate point-to-point remote positioning of a needle guide inside an MR scanner with the aim of evaluating the potential advantages over the manual procedure. In order to minimize alterations to the MR environment the system employs plastic pneumatic actuators and 9 m long supply lines connecting with the control hardware located outside the magnet room. An improved Sliding Mode Control (SMC) scheme was designed for the position control of the device. Wireless micro-coil fiducials are used for automatic registration in the reference frame of the MR scanner. The MRI-compatibility and the accuracy of the prototype are demonstrated with experiments in the MR scanner.
International Conference on Shape Modeling and Applications 2005 (SMI' 05), 2005
We present an algorithm for computing the thickness of a trimmed Non-Uniform Rational B-Spline (N... more We present an algorithm for computing the thickness of a trimmed Non-Uniform Rational B-Spline (NURBS) model, by finding the radius of maximal spheres contained within the modelled object. This information can then be visualised as a colour coded thickness map on the object's surface, allowing intuitive interpretation by designers and engineers. By making use of surface normal information the task of finding maximal spheres can be reduced to a simple minimisation problem, avoiding the calculation of Delaunay tetrahedra or Voronoi diagrams. Also our method allows the thickness to be evaluated one point at a time, so computation can be focused on a localised region of the model. The simplicity of this method makes implementation straightforward allowing it to be rapidly integrated into existing CAD/CAM packages.
Proceedings of 3rd IEEE International Conference on Image Processing, 1996
Registration of a rigid body is an essential step in many machine vision tasks. This paper presen... more Registration of a rigid body is an essential step in many machine vision tasks. This paper presents performance analysis of the iterative closest point method implemented for dimensional inspection of free form surfaces where the set of measured points is registered to a NURBS model. The results were obtained through Monte Carlo simulation. A large number of experiments were performed
Today's manufacturing industry is characterised by strong interdependencies between companies ope... more Today's manufacturing industry is characterised by strong interdependencies between companies operating in globally distributed production networks. The operation of such value-added chains has been enabled by recent developments in information and communication technologies (ICT) and computer networking. To gain competitive advantages and efficiency improvements such as reduced inventory and higher delivery reliability, companies are introducing information exchange systems that communicate demand to suppliers and production progress information to customers in the network. This article proposes a system that supports cooperation in complex production networks by enabling companies to determine and exchange supply information with their customers. The requirements for such a system are analysed and it is embedded in a framework of supply chain management business processes. The system facilitates the determination and exchange of meaningful, reliable and upto-date order status information from the supplier to the customer. Based on comparing the progress of an internal production order with a pre-defined milestone model for each product, the status of the customer order is determined and-in case of lateness-communicated to the customer together with an early warning. To demonstrate the developed supply information concepts and processes, the business process is implemented as a pilot system and evaluated by the user companies participating in the 5th Framework IST project CoOPERATE .
Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2001
Probe radius compensation is necessary in metrology applications that employ contact probes, but ... more Probe radius compensation is necessary in metrology applications that employ contact probes, but it can be a significant source of systematic measurement errors when dealing with free-form part geometry. The paper presents implementation and performance analysis of a proposed new compensation technique based on the nominal computer aided design (CAD) model, which is assumed to be defined using non-uniform rational B-splines (NURBS). Errors associated with the conventional compensation approach are assessed on the basis of experiments using a modern coordinate measuring machine (CMM), providing clear motivation for this work. The proposed method consists of a number of steps, including measurement, generation of offset nominal surfaces, registration, surface fitting, data smoothing and calculation of compensating offsets. Critical steps include registration and NURBS surface fitting and their implementation is presented. Simulation studies are used to analyse the registration accurac...
The paper proposes a new method for efficient triangulation of large, unordered sets of 3D points... more The paper proposes a new method for efficient triangulation of large, unordered sets of 3D points using a CAD model comprising NURBS entities. It is primarily aimed at engineering applications involving analysis and visualisation of measured data, such as inspection, where a model of the object in question is available. Registration of the data to the model is the necessary first step, enabling the triangulation to be efficiently performed in 2D, on the projections of the measured points onto the model entities. The derived connectivity is then applied to the original 3D data. Improvement of the generated 3D mesh is often necessary, involving mesh smoothing, constraint-based elimination of redundant triangles and merging of mesh patches. Examples involving random measurements on aerospace and automotive free-form components are presented.
International Journal of Computer Integrated Manufacturing, 2004
Manufacturing industries, especially the aerospace and the automotive, require updating of CAD mo... more Manufacturing industries, especially the aerospace and the automotive, require updating of CAD models so that the manufactured geometry is accurately represented. Often, additional constraints such as continuity are imposed on the model. The updated model may be employed to provide a more realistic analysis of the part's in-service performance. The necessary tools for realizing this task included dimensional measurement and geometric modelling. This paper discussed how this was achieved in the case of an aeroengine gas turbine blade. Measurement was performed using a coordinate measuring machine equipped with a touch trigger probe. Measurement path plan is based on the pre-processed CAD model. The accuracy was improved using our method for probe radius compensation. The remodelling steps include preparation of the base surface, registration and least squares surface fitting. The surface preparation is needed in order to maintain prescribed continuity. Also, special attention was paid to cure ill-conditioning, which occurs when fitting trimmed surfaces. The adopted novel solution involves regularization and introduces two additional terms in the fitting functional. Two weighting coefficients are introduced to improve flexibility of the solution and they represent the user's confidence in the measurements and quality of the initial model.
The International Journal of Advanced Manufacturing Technology, 2000
... can be seen that no direct connection between global applications and the LIM is allowed. ...... more ... can be seen that no direct connection between global applications and the LIM is allowed. ... So all these distributed data can arrive at the GIM for the application before being ... all distributed applications with IDL interfaces regardless of their platforms and program-ming languages ...
The International Journal of Advanced Manufacturing Technology, 1998
The paper presents an implementation of a methodolgy for reliable and feasible dimensional measur... more The paper presents an implementation of a methodolgy for reliable and feasible dimensional measurement of engineering components containing free-form surfaces. Two main requirements had to be satisfied. First, a large number of points had to be accurately measured. Secondly, the set of corresponding points on the nominal model had to be compuIed within a reasonable time. The first aspect was satisfied by adopting a non-contact measurement technique based on laser triangulation. High accuracy was achieved through software prealignment for precise component localisation and through appropriate measurement planning, both based on the CAD model Detem~ination of the corresponding nominal points was solved by best-fitting. Significant speed improvements were achieved through an implementation of the iterative closest point algorithm, based on a dual representation of the surface. The nominal surface is defined using NURBS entities and its approximation is determined as a polyhedral mesh. A sampling criterion for complex surfaces was derived and implemented, producing encouraging results. Validity of the proposed approach is supported by experiments and by simulation studies involving real engineering components'.
The paper presents an implementation of free-form surface registration in relation to inspection ... more The paper presents an implementation of free-form surface registration in relation to inspection of engineering components, defined as NURBS. Registration is principally performed through the Iterative Closest Point (ICP) method. The time-critical step in ICP was found to be the determination of the closest points on NURBS to a given point in space. Significant speed improvements were achieved through the
2015 23rd Mediterranean Conference on Control and Automation (MED), 2015
This paper presents the control of a master-slave system for teleoperated needle insertion under ... more This paper presents the control of a master-slave system for teleoperated needle insertion under guidance by Magnetic Resonance Imaging (MRI). The primary aim of our research is the robot-assisted laser ablation of liver tumors. The master-slave system consists of a master unit that sits next to the operator, outside the scanner room, and of a slave unit located inside the cylindrical MRI scanner. The needle insertion force is measured with a specially designed fiber optic force sensor mounted on the slave unit. Pneumatic actuation is employed in both master and slave in order to minimize the interference with the MRI environment. Accurate position control of the slave unit is achieved with a Time Delay Control scheme (TDC). Differently from previous designs, the force feedback on the master unit is provided by an adaptive controller that compensates the friction of the pneumatic actuator. The advantages over a baseline force controller are demonstrated with experiments on silicone rubber phantoms.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2017
A normal conducting 805 MHz test cavity with an in built button shaped sample is used to conduct ... more A normal conducting 805 MHz test cavity with an in built button shaped sample is used to conduct a series of surface treatment experiments. The button enhances the local fields and influences the likelihood of an RF breakdown event. Because of their smaller sizes, compared to the whole cavity surface, they allow practical investigations of the effects of cavity surface preparation in relation to RF breakdown. Manufacturing techniques and steps for preparing the buttons to improve the surface quality are described in detail. It was observed that even after the final stage of the surface treatment, defects on the surface of the cavities still could be found.
Applications in engineering manufacture, such as dimensional inspection, often require triangulat... more Applications in engineering manufacture, such as dimensional inspection, often require triangulation of large sets of measured 3D data. The CAD models of relevant complex parts are usually defined using trimmed NURBS (non-uniform rational B-spline). With such situations in mind, the paper proposes a new triangulation procedure which achieves high efficiency and robustness by utilising the CAD model as an available
Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 1997
Accurate dimensional inspection and error analysis of free-form surfaces requires accurate regist... more Accurate dimensional inspection and error analysis of free-form surfaces requires accurate registration of the component in hand. Registration of surfaces defined as non-uniform rational B-splines (NURBS) has been realized through an implementation of the iterative closest point method (ICP). The paper presents performance analysis of the ICP registration method using Monte Carlo simulation. A large number of simulations were performed on an example of a precision engineering component, an aero-engine turbine blade, which was judged to possess a useful combination of geometric characteristics such that the results of the analysis had generic significance. Data sets were obtained through CAD (computer aided design)-based inspection. Confidence intervals for estimated transformation parameters, maximum error between a measured point and the nominal surface (which is extremely important for inspection) mean error and several other performance criteria are presented. The influence of sh...
International Journal of Biomechatronics and Biomedical Robotics, 2015
This article presents the design and control of a pneumatic needle positioner for laser ablation ... more This article presents the design and control of a pneumatic needle positioner for laser ablation of liver tumours under guidance by Magnetic Resonance Imaging (MRI). The prototype was developed to provide accurate point-to-point remote positioning of a needle guide inside an MR scanner with the aim of evaluating the potential advantages over the manual procedure. In order to minimize alterations to the MR environment the system employs plastic pneumatic actuators and 9 m long supply lines connecting with the control hardware located outside the magnet room. An improved Sliding Mode Control (SMC) scheme was designed for the position control of the device. Wireless micro-coil fiducials are used for automatic registration in the reference frame of the MR scanner. The MRI-compatibility and the accuracy of the prototype are demonstrated with experiments in the MR scanner.
International Conference on Shape Modeling and Applications 2005 (SMI' 05), 2005
We present an algorithm for computing the thickness of a trimmed Non-Uniform Rational B-Spline (N... more We present an algorithm for computing the thickness of a trimmed Non-Uniform Rational B-Spline (NURBS) model, by finding the radius of maximal spheres contained within the modelled object. This information can then be visualised as a colour coded thickness map on the object's surface, allowing intuitive interpretation by designers and engineers. By making use of surface normal information the task of finding maximal spheres can be reduced to a simple minimisation problem, avoiding the calculation of Delaunay tetrahedra or Voronoi diagrams. Also our method allows the thickness to be evaluated one point at a time, so computation can be focused on a localised region of the model. The simplicity of this method makes implementation straightforward allowing it to be rapidly integrated into existing CAD/CAM packages.
Proceedings of 3rd IEEE International Conference on Image Processing, 1996
Registration of a rigid body is an essential step in many machine vision tasks. This paper presen... more Registration of a rigid body is an essential step in many machine vision tasks. This paper presents performance analysis of the iterative closest point method implemented for dimensional inspection of free form surfaces where the set of measured points is registered to a NURBS model. The results were obtained through Monte Carlo simulation. A large number of experiments were performed
Today's manufacturing industry is characterised by strong interdependencies between companies ope... more Today's manufacturing industry is characterised by strong interdependencies between companies operating in globally distributed production networks. The operation of such value-added chains has been enabled by recent developments in information and communication technologies (ICT) and computer networking. To gain competitive advantages and efficiency improvements such as reduced inventory and higher delivery reliability, companies are introducing information exchange systems that communicate demand to suppliers and production progress information to customers in the network. This article proposes a system that supports cooperation in complex production networks by enabling companies to determine and exchange supply information with their customers. The requirements for such a system are analysed and it is embedded in a framework of supply chain management business processes. The system facilitates the determination and exchange of meaningful, reliable and upto-date order status information from the supplier to the customer. Based on comparing the progress of an internal production order with a pre-defined milestone model for each product, the status of the customer order is determined and-in case of lateness-communicated to the customer together with an early warning. To demonstrate the developed supply information concepts and processes, the business process is implemented as a pilot system and evaluated by the user companies participating in the 5th Framework IST project CoOPERATE .
Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2001
Probe radius compensation is necessary in metrology applications that employ contact probes, but ... more Probe radius compensation is necessary in metrology applications that employ contact probes, but it can be a significant source of systematic measurement errors when dealing with free-form part geometry. The paper presents implementation and performance analysis of a proposed new compensation technique based on the nominal computer aided design (CAD) model, which is assumed to be defined using non-uniform rational B-splines (NURBS). Errors associated with the conventional compensation approach are assessed on the basis of experiments using a modern coordinate measuring machine (CMM), providing clear motivation for this work. The proposed method consists of a number of steps, including measurement, generation of offset nominal surfaces, registration, surface fitting, data smoothing and calculation of compensating offsets. Critical steps include registration and NURBS surface fitting and their implementation is presented. Simulation studies are used to analyse the registration accurac...
The paper proposes a new method for efficient triangulation of large, unordered sets of 3D points... more The paper proposes a new method for efficient triangulation of large, unordered sets of 3D points using a CAD model comprising NURBS entities. It is primarily aimed at engineering applications involving analysis and visualisation of measured data, such as inspection, where a model of the object in question is available. Registration of the data to the model is the necessary first step, enabling the triangulation to be efficiently performed in 2D, on the projections of the measured points onto the model entities. The derived connectivity is then applied to the original 3D data. Improvement of the generated 3D mesh is often necessary, involving mesh smoothing, constraint-based elimination of redundant triangles and merging of mesh patches. Examples involving random measurements on aerospace and automotive free-form components are presented.
International Journal of Computer Integrated Manufacturing, 2004
Manufacturing industries, especially the aerospace and the automotive, require updating of CAD mo... more Manufacturing industries, especially the aerospace and the automotive, require updating of CAD models so that the manufactured geometry is accurately represented. Often, additional constraints such as continuity are imposed on the model. The updated model may be employed to provide a more realistic analysis of the part's in-service performance. The necessary tools for realizing this task included dimensional measurement and geometric modelling. This paper discussed how this was achieved in the case of an aeroengine gas turbine blade. Measurement was performed using a coordinate measuring machine equipped with a touch trigger probe. Measurement path plan is based on the pre-processed CAD model. The accuracy was improved using our method for probe radius compensation. The remodelling steps include preparation of the base surface, registration and least squares surface fitting. The surface preparation is needed in order to maintain prescribed continuity. Also, special attention was paid to cure ill-conditioning, which occurs when fitting trimmed surfaces. The adopted novel solution involves regularization and introduces two additional terms in the fitting functional. Two weighting coefficients are introduced to improve flexibility of the solution and they represent the user's confidence in the measurements and quality of the initial model.
The International Journal of Advanced Manufacturing Technology, 2000
... can be seen that no direct connection between global applications and the LIM is allowed. ...... more ... can be seen that no direct connection between global applications and the LIM is allowed. ... So all these distributed data can arrive at the GIM for the application before being ... all distributed applications with IDL interfaces regardless of their platforms and program-ming languages ...
The International Journal of Advanced Manufacturing Technology, 1998
The paper presents an implementation of a methodolgy for reliable and feasible dimensional measur... more The paper presents an implementation of a methodolgy for reliable and feasible dimensional measurement of engineering components containing free-form surfaces. Two main requirements had to be satisfied. First, a large number of points had to be accurately measured. Secondly, the set of corresponding points on the nominal model had to be compuIed within a reasonable time. The first aspect was satisfied by adopting a non-contact measurement technique based on laser triangulation. High accuracy was achieved through software prealignment for precise component localisation and through appropriate measurement planning, both based on the CAD model Detem~ination of the corresponding nominal points was solved by best-fitting. Significant speed improvements were achieved through an implementation of the iterative closest point algorithm, based on a dual representation of the surface. The nominal surface is defined using NURBS entities and its approximation is determined as a polyhedral mesh. A sampling criterion for complex surfaces was derived and implemented, producing encouraging results. Validity of the proposed approach is supported by experiments and by simulation studies involving real engineering components'.
The paper presents an implementation of free-form surface registration in relation to inspection ... more The paper presents an implementation of free-form surface registration in relation to inspection of engineering components, defined as NURBS. Registration is principally performed through the Iterative Closest Point (ICP) method. The time-critical step in ICP was found to be the determination of the closest points on NURBS to a given point in space. Significant speed improvements were achieved through the
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Papers by Mihailo Ristic