This paper describes the calibration of the measuring system of a rigid positioning system with h... more This paper describes the calibration of the measuring system of a rigid positioning system with high resolution based on piezostepper technology. The measuring system measures all six degrees of freedom of the position of the stage with respect to an independent reference frame. This enables the drive system to correct the drive co-ordinates as well as the bearing co-ordinates. This reference is a true metrological reference in the sense that is independent suspended from either the world or the tool. The accuracy of calibration is estimated to be within 100 nm.
Proceedings of the 16th IFAC World Congress, 2005, 2005
Friction modeling and identification is a prerequisite for the accurate control of electromechani... more Friction modeling and identification is a prerequisite for the accurate control of electromechanical systems. This paper considers the identification and control of friction in a high load torque DC motor to the end of achieving accurate tracking. Model-based friction compensation in the feedforward part of the controller is considered. For this purpose, friction model structures ranging from the simple Coulomb model through the recently developed Generalized Maxwell Slip (GMS) model are employed. The performance of those models is compared and contrasted in regard both to identification and to compensation. It turns out that the performance depends on the prevailing range of speeds and displacements, but that in all cases, the GMS model scores the best.
Proceedings of the Fourth International Conference on Computer Integrated Manufacturing and Automation Technology, 1994
Flexible manufacturing systems (FMS) are typical examples of asynchronous concurrent systems. Pet... more Flexible manufacturing systems (FMS) are typical examples of asynchronous concurrent systems. Petri nets have evolved into a powerful tool for analysing asynchronous concurrent systems. This paper demonstrates a new approach that integrates the modelling, simulation and control of FMS by using Petri nets. It is an implementation of requirements driven scheduling (ReDS). By using least commitment planning and some heuristics,
Proceedings of the 2000 American Control Conference. ACC (IEEE Cat. No.00CH36334), 2000
This paper treats the problem of modelling and identification of the various elements of a pneuma... more This paper treats the problem of modelling and identification of the various elements of a pneumatic servo positioning system to the end of constructing a complete and effective model that can be used for simulation and accurate control of such systems. Particular attention is paid to two important elements that manifest a strong nonlinear behaviour, viz. air flow and friction. In the first instance, an empirical model connecting the pneumatic valve's driving voltage, the pressures upstream and downstream, and the flow is hypothesised based on the nozzle formula. With this model, the flow function is then systematically identified. As regards friction, the Leuven model structure is used as basis for identification. Here, the two basic friction regimes, viz. presliding, with its hysteresis behaviour, and gross sliding are well exposed and their essential parameters identified.
International Journal of Non-Linear Mechanics, 2011
Bearings, friction wheels, cams, etc. are widely employed elements in machine construction. The m... more Bearings, friction wheels, cams, etc. are widely employed elements in machine construction. The modeling of the dynamics of rolling friction plays therefore a crucial role in the simulation and optimization of such systems. This paper describes a recently developed transient-rolling-friction model with its application to different generic dynamical systems, to simulate the effects of rolling friction or traction on the dynamics of mechanical systems. The results, which are expressed in terms of the complex stiffness arising in the rolling-contact patches, show that the behavior depends on both the amplitude and the frequency of oscillation. For low amplitudes and frequencies, the behavior is quasilinear. For increasing amplitudes and frequencies, however, strong non-linearities appear, leading to complex behavior.
Bounded Environment Passivity, presented in this paper, allows one to de-sign teleoperation syste... more Bounded Environment Passivity, presented in this paper, allows one to de-sign teleoperation systems that behave passive provided that the environment with which interaction takes place, belongs to an a-priori defined range of environ-ments. The use of such a-priori knowledge on the environment reduces conser-vativeness with respect to classical design approaches. An additional advantage lies in its capability to get a clearer insight on which type of environments are problematic for the specific controller under investigation. On the basis of a case study, i.e. the well-known Position-Force controller, this paper describes and compares different passivity-based methods. First, the tra-ditional methods of two-port passivity and absolute stability are applied. The restrictions of these methods to come up with useful design rules are explic-itly demonstrated. Then, the Bounded Environment Passivity conditions of the Position-Force controller are derived. These conditions describe the r...
The dynamic behaviour of high-performance mechanical systems such as robots is strongly influence... more The dynamic behaviour of high-performance mechanical systems such as robots is strongly influenced by the characteristics of the link joints. Joint backlash as a result of wear due to severe stress imposed on the transmission system degrades the robot performance. This paper presents a systematic methodology to diagnose the joint-backlash of a robot by monitoring its vibration response during normal operations. To indicate the reversal of motion of a robot link, and to characterise the spectral patterns of vibration signatures, non-stationary time–frequency analysis algorithms have been employed, which illustrate the signature in a simultaneous time–frequency plane. Significant features are extracted from time domain analysis (probability density moments), and from time–frequency domain analysis (local energy calculations). Artificial neural networks are used as tools for pattern recognition. Experimental results show that the proposed techniques can analyse single-joint backlash quantitatively. Moreover, the described methods also allow to single out backlash in the individual joints in case of multiple-joint backlash.
Proceedings First International Symposium on Environmentally Conscious Design and Inverse Manufacturing, 1999
This paper describes a study on the environmental impact of a Bosch windshield wiper. The first p... more This paper describes a study on the environmental impact of a Bosch windshield wiper. The first part of the project consisted of comparing the windshield wiper with known ecodesign examples, in order to put red flags at apparently the most important environmental impacts of the product's life cycle (including production, use, and disposal). In a second part of the project
Despite critical components, very little attention has been paid for wet friction clutches in the... more Despite critical components, very little attention has been paid for wet friction clutches in the monitoring and prognostics research field. This paper presents and discusses an overall methodology for assessing the health (performance) and predicting the remaining useful life (RUL) of wet friction clutches. Three principle features extracted from relative velocity signal measured between the input and output shaft of the clutch, namely (i) the normalized engagement duration, (ii) the normalized Euclidean distance and (iii) the Spectral Angle Mapper (SAM) distance are fused with a logistic regression technique into a single value called the health index. In logistic regression analysis, the output of the logistic model (i.e. the health index) is restricted between 0 and 1. Accordingly, the logistic model can guide the users to assess the state of a wet friction clutch either in healthy state (e.g. health index value of (close to) 1) or in failed state (e.g. health index value of (cl...
This paper considers the problem for condition monitoring of robot joints employing measured acce... more This paper considers the problem for condition monitoring of robot joints employing measured acceleration signals. The study aims at (1) Determining features, to be extracted directly from the measured acceleration signals, to detect defects in robot joints and at (2) Finding features dependent on the size of the fault in order to quantify the present defects. The signals coming from intact robot joints and from joints containing backlash or clearance are analyzed using nonlinear dynamics as well as statistical tools. A method for defect detection that employs nonlinear autoregressive (AR) modeling of the acceleration signals is successfully applied to detect backlash and clearance in robot joints. Two procedures for defect quantification are considered -one of them based on the AR modeling and the other employing nonlinear dynamics and statistical features. The problems are considered in the context of a pattern recognition paradigm.
13th IFAC Symposium on Information Control Problems in Manufacturing, 2009
A supply network comprises a set of production entities. Each production entity is both specific ... more A supply network comprises a set of production entities. Each production entity is both specific and autonomous. Yet the production entities are collectively responsible for procurement, manufacturing and distribution activities associated with one or more families of related products. Controlling the supply network requires integration rather than governance of the different production entities. To this aim, the intelligent product concept is introduced. Intelligent products, composed of an intelligent agent and an intelligent being, focuses on the suitability for integration. Intelligent products are robust towards disturbances or in general unreliabilities. However, intelligent products don't provide explicit support for dealing with unreliabilities. Taking decisions in an unreliable environment requires a trust relationship between the different entities. The paper elaborates trust and proposes an architecture where decisions are based on trust. Essential are expectations about the environment and the confidence in the correctness of the expectation.
Estimation of modal parameters of mechanical structures is usually carried out by utilising the F... more Estimation of modal parameters of mechanical structures is usually carried out by utilising the Frequency Response Function (FRF) for linear systems, skeleton identification such as Hilbert transform, or describing function method for nonlinear systems. However, these techniques could be applied only when the output of a system is periodic for a periodic input. However, under certain excitation conditions in nonlinear systems, chaotic behaviour might occur so that the response is aperiodic. In that case, chaos quantification techniques, such as Lyapunov exponent, are proposed in the literature. For experimental validation of this phenomenon, a robot joint mechanism developed at KULeuven/PMA was used. In this setup, backlash was introduced in the connection of the harmonic drive to the shaft. Chaotic response, which appears under certain excitation conditions and could be used as backlash signature, is dealt with both by a simulation study and by experimental signal analysis after application of appropriate filtration techniques.
This paper describes the calibration of the measuring system of a rigid positioning system with h... more This paper describes the calibration of the measuring system of a rigid positioning system with high resolution based on piezostepper technology. The measuring system measures all six degrees of freedom of the position of the stage with respect to an independent reference frame. This enables the drive system to correct the drive co-ordinates as well as the bearing co-ordinates. This reference is a true metrological reference in the sense that is independent suspended from either the world or the tool. The accuracy of calibration is estimated to be within 100 nm.
Proceedings of the 16th IFAC World Congress, 2005, 2005
Friction modeling and identification is a prerequisite for the accurate control of electromechani... more Friction modeling and identification is a prerequisite for the accurate control of electromechanical systems. This paper considers the identification and control of friction in a high load torque DC motor to the end of achieving accurate tracking. Model-based friction compensation in the feedforward part of the controller is considered. For this purpose, friction model structures ranging from the simple Coulomb model through the recently developed Generalized Maxwell Slip (GMS) model are employed. The performance of those models is compared and contrasted in regard both to identification and to compensation. It turns out that the performance depends on the prevailing range of speeds and displacements, but that in all cases, the GMS model scores the best.
Proceedings of the Fourth International Conference on Computer Integrated Manufacturing and Automation Technology, 1994
Flexible manufacturing systems (FMS) are typical examples of asynchronous concurrent systems. Pet... more Flexible manufacturing systems (FMS) are typical examples of asynchronous concurrent systems. Petri nets have evolved into a powerful tool for analysing asynchronous concurrent systems. This paper demonstrates a new approach that integrates the modelling, simulation and control of FMS by using Petri nets. It is an implementation of requirements driven scheduling (ReDS). By using least commitment planning and some heuristics,
Proceedings of the 2000 American Control Conference. ACC (IEEE Cat. No.00CH36334), 2000
This paper treats the problem of modelling and identification of the various elements of a pneuma... more This paper treats the problem of modelling and identification of the various elements of a pneumatic servo positioning system to the end of constructing a complete and effective model that can be used for simulation and accurate control of such systems. Particular attention is paid to two important elements that manifest a strong nonlinear behaviour, viz. air flow and friction. In the first instance, an empirical model connecting the pneumatic valve's driving voltage, the pressures upstream and downstream, and the flow is hypothesised based on the nozzle formula. With this model, the flow function is then systematically identified. As regards friction, the Leuven model structure is used as basis for identification. Here, the two basic friction regimes, viz. presliding, with its hysteresis behaviour, and gross sliding are well exposed and their essential parameters identified.
International Journal of Non-Linear Mechanics, 2011
Bearings, friction wheels, cams, etc. are widely employed elements in machine construction. The m... more Bearings, friction wheels, cams, etc. are widely employed elements in machine construction. The modeling of the dynamics of rolling friction plays therefore a crucial role in the simulation and optimization of such systems. This paper describes a recently developed transient-rolling-friction model with its application to different generic dynamical systems, to simulate the effects of rolling friction or traction on the dynamics of mechanical systems. The results, which are expressed in terms of the complex stiffness arising in the rolling-contact patches, show that the behavior depends on both the amplitude and the frequency of oscillation. For low amplitudes and frequencies, the behavior is quasilinear. For increasing amplitudes and frequencies, however, strong non-linearities appear, leading to complex behavior.
Bounded Environment Passivity, presented in this paper, allows one to de-sign teleoperation syste... more Bounded Environment Passivity, presented in this paper, allows one to de-sign teleoperation systems that behave passive provided that the environment with which interaction takes place, belongs to an a-priori defined range of environ-ments. The use of such a-priori knowledge on the environment reduces conser-vativeness with respect to classical design approaches. An additional advantage lies in its capability to get a clearer insight on which type of environments are problematic for the specific controller under investigation. On the basis of a case study, i.e. the well-known Position-Force controller, this paper describes and compares different passivity-based methods. First, the tra-ditional methods of two-port passivity and absolute stability are applied. The restrictions of these methods to come up with useful design rules are explic-itly demonstrated. Then, the Bounded Environment Passivity conditions of the Position-Force controller are derived. These conditions describe the r...
The dynamic behaviour of high-performance mechanical systems such as robots is strongly influence... more The dynamic behaviour of high-performance mechanical systems such as robots is strongly influenced by the characteristics of the link joints. Joint backlash as a result of wear due to severe stress imposed on the transmission system degrades the robot performance. This paper presents a systematic methodology to diagnose the joint-backlash of a robot by monitoring its vibration response during normal operations. To indicate the reversal of motion of a robot link, and to characterise the spectral patterns of vibration signatures, non-stationary time–frequency analysis algorithms have been employed, which illustrate the signature in a simultaneous time–frequency plane. Significant features are extracted from time domain analysis (probability density moments), and from time–frequency domain analysis (local energy calculations). Artificial neural networks are used as tools for pattern recognition. Experimental results show that the proposed techniques can analyse single-joint backlash quantitatively. Moreover, the described methods also allow to single out backlash in the individual joints in case of multiple-joint backlash.
Proceedings First International Symposium on Environmentally Conscious Design and Inverse Manufacturing, 1999
This paper describes a study on the environmental impact of a Bosch windshield wiper. The first p... more This paper describes a study on the environmental impact of a Bosch windshield wiper. The first part of the project consisted of comparing the windshield wiper with known ecodesign examples, in order to put red flags at apparently the most important environmental impacts of the product's life cycle (including production, use, and disposal). In a second part of the project
Despite critical components, very little attention has been paid for wet friction clutches in the... more Despite critical components, very little attention has been paid for wet friction clutches in the monitoring and prognostics research field. This paper presents and discusses an overall methodology for assessing the health (performance) and predicting the remaining useful life (RUL) of wet friction clutches. Three principle features extracted from relative velocity signal measured between the input and output shaft of the clutch, namely (i) the normalized engagement duration, (ii) the normalized Euclidean distance and (iii) the Spectral Angle Mapper (SAM) distance are fused with a logistic regression technique into a single value called the health index. In logistic regression analysis, the output of the logistic model (i.e. the health index) is restricted between 0 and 1. Accordingly, the logistic model can guide the users to assess the state of a wet friction clutch either in healthy state (e.g. health index value of (close to) 1) or in failed state (e.g. health index value of (cl...
This paper considers the problem for condition monitoring of robot joints employing measured acce... more This paper considers the problem for condition monitoring of robot joints employing measured acceleration signals. The study aims at (1) Determining features, to be extracted directly from the measured acceleration signals, to detect defects in robot joints and at (2) Finding features dependent on the size of the fault in order to quantify the present defects. The signals coming from intact robot joints and from joints containing backlash or clearance are analyzed using nonlinear dynamics as well as statistical tools. A method for defect detection that employs nonlinear autoregressive (AR) modeling of the acceleration signals is successfully applied to detect backlash and clearance in robot joints. Two procedures for defect quantification are considered -one of them based on the AR modeling and the other employing nonlinear dynamics and statistical features. The problems are considered in the context of a pattern recognition paradigm.
13th IFAC Symposium on Information Control Problems in Manufacturing, 2009
A supply network comprises a set of production entities. Each production entity is both specific ... more A supply network comprises a set of production entities. Each production entity is both specific and autonomous. Yet the production entities are collectively responsible for procurement, manufacturing and distribution activities associated with one or more families of related products. Controlling the supply network requires integration rather than governance of the different production entities. To this aim, the intelligent product concept is introduced. Intelligent products, composed of an intelligent agent and an intelligent being, focuses on the suitability for integration. Intelligent products are robust towards disturbances or in general unreliabilities. However, intelligent products don't provide explicit support for dealing with unreliabilities. Taking decisions in an unreliable environment requires a trust relationship between the different entities. The paper elaborates trust and proposes an architecture where decisions are based on trust. Essential are expectations about the environment and the confidence in the correctness of the expectation.
Estimation of modal parameters of mechanical structures is usually carried out by utilising the F... more Estimation of modal parameters of mechanical structures is usually carried out by utilising the Frequency Response Function (FRF) for linear systems, skeleton identification such as Hilbert transform, or describing function method for nonlinear systems. However, these techniques could be applied only when the output of a system is periodic for a periodic input. However, under certain excitation conditions in nonlinear systems, chaotic behaviour might occur so that the response is aperiodic. In that case, chaos quantification techniques, such as Lyapunov exponent, are proposed in the literature. For experimental validation of this phenomenon, a robot joint mechanism developed at KULeuven/PMA was used. In this setup, backlash was introduced in the connection of the harmonic drive to the shaft. Chaotic response, which appears under certain excitation conditions and could be used as backlash signature, is dealt with both by a simulation study and by experimental signal analysis after application of appropriate filtration techniques.
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Papers by H. Van Brussel