The estimation of the friction torque in joints transmissions is a crucial task in the robotics f... more The estimation of the friction torque in joints transmissions is a crucial task in the robotics field. This work presents a model that describes the variations on friction that occur during the operations of an industrial robot due to thermal effects. The proposed technique is simple to implement and economically convenient. Possible applications are the improvement of the friction compensation algorithms used in control systems, the prediction of energy consumption and predictive maintenance
This paper describes different intelligent active modes to control an exoskeleton robotic device,... more This paper describes different intelligent active modes to control an exoskeleton robotic device, devoted to the hand rehabilitation. A position-based control with EMG signals and mirroring technique has been implemented, with two different possibilities: triggered ON_OFF control and proportional control. The developed control permits to perform robotic aided exercises for the hand rehabilitation, leveraging the mirroring effect so as to obtain a better neuron-motor recovery. A preliminary study for a force based control has been conducted. The close correlation between the EMG signal and the pressure inside a bottle, grasped by the hand, allows to demonstrate the correlation between the EMG signal and the force exerted. The structure of the possible force-control mode is than presented.
2021 24th International Conference on Mechatronics Technology (ICMT), 2021
Objective: The sit-to-stand transition is an important task for the evaluation of physical indepe... more Objective: The sit-to-stand transition is an important task for the evaluation of physical independence, especially in fragile subjects like elderly patients, to monitor and reduce the risk of falls or damage. This study aims at assessing the kinematic characteristics of the sit-to-stand transition from a quantitative perspective, using a wireless IMU sensor, and describes a set of parameters suitable for evaluating the movement performance in everyday practice. Methods: An acquisition campaign was designed and carried out on 20 healthy subjects and 13 patients to evaluate acceleration and angular velocity generated during a sit-to-stand task. For each subject, at least four acquisitions were performed, to create a final dataset of 173 acquisitions. The values of the proposed parameters were computed, and results were analyzed with descriptive statistics. Results: According to the proposed parameters definitions and the analyzed dataset, acceleration-and angular velocity-related parameters present statistically significant differences between healthy and pathological data samples, unlike total time TT.
Monitoring vibrations in rotating machinery allows effective diagnostics, as abnormal functioning... more Monitoring vibrations in rotating machinery allows effective diagnostics, as abnormal functioning states are related to specific patterns that can be extracted from vibration signals. Extensively studied issues concern the different methodologies used for carrying out the main phases (signal measurements, pre-processing and processing, feature selection, and fault diagnosis) of a malfunction automatic diagnosis. In addition, vibration-based condition monitoring has been applied to a number of different mechanical systems or components. In this review, a systematic study of the works related to the topic was carried out. A preliminary phase involved the analysis of the publication distribution, to understand what was the interest in studying the application of the method to the various rotating machineries, to identify the interest in the investigation of the main phases of the diagnostic process, and to identify the techniques mainly used for each single phase of the process. Subseq...
Cam follower mechanisms are widely used in automated manufacturing machinery to transform a rotar... more Cam follower mechanisms are widely used in automated manufacturing machinery to transform a rotary stationary motion into a more general required movement. Reverse engineering of cams has been studied, and some solutions based on different approaches have been identified in the literature. This article proposes an innovative method based on the use of an evolutionary algorithm for the identification of a law of motion that allows for approximating in the best way the motion or the sampled profile on the physical device. Starting from the acquired data, through a genetic algorithm, a representation of the movement (and therefore of the cam profile) is identified based on a type of motion law traditionally used for this purpose, i.e., the modified trapezoidal (better known as modified seven segments). With this method it is possible to estimate the coefficients of the parametric motion law, thus allowing the designer to further manipulate them according to the usual motion planning te...
Poly(dimethylsiloxane) (PDMS) is usually considered as a dielectric material and the PDMS microch... more Poly(dimethylsiloxane) (PDMS) is usually considered as a dielectric material and the PDMS microchannel wall can be treated as an electrically insulated boundary in an applied electric field. However, in certain layouts of microfluidic networks, electrical leakage through the PDMS microfluidic channel walls may not be negligible, which must be carefully considered in the microfluidic circuit design. In this paper, we report on the experimental characterization of the electrical leakage current through PDMS microfluidic channel walls of different configurations. Our numerical and experimental studies indicate that for tens of microns thick PDMS channel walls, electrical leakage through the PDMS wall could significantly alter the electrical field in the main channel. We further show that we can use the electrical leakage through the PDMS microfluidic channel wall to control the electrolyte flow inside the microfluidic channel and manipulate the particle motion inside the microfluidic channel. More specifically, we can trap individual particles at different locations inside the microfluidic channel by balancing the electroosmotic flow and the electrophoretic migration of the particle.
Exoskeletons are robots that closely interact with humans and that are increasingly used for diff... more Exoskeletons are robots that closely interact with humans and that are increasingly used for different purposes, such as rehabilitation, assistance in the activities of daily living (ADLs), performance augmentation or as haptic devices. In the last few decades, the research activity on these robots has grown exponentially, and sensors and actuation technologies are two fundamental research themes for their development. In this review, an in-depth study of the works related to exoskeletons and specifically to these two main aspects is carried out. A preliminary phase investigates the temporal distribution of scientific publications to capture the interest in studying and developing novel ideas, methods or solutions for exoskeleton design, actuation and sensors. The distribution of the works is also analyzed with respect to the device purpose, body part to which the device is dedicated, operation mode and design methods. Subsequently, actuation and sensing solutions for the exoskeleto...
This paper presents a model that describes the effect of heat exchange on dynamic friction in the... more This paper presents a model that describes the effect of heat exchange on dynamic friction in the joints of an industrial robot. As concern the modeling of friction as a function of the rotation speed of the joint, a third degree polynomial is used. The coefficients of the polynomial, which depends on the temperature, are estimated by means of a suitable identification procedure. The proposed technique is simple to implement and economically convenient. Experimental tests have shown that the method here proposed, despite its simplicity, can estimate with good reliability the variations of friction that occur during the operation of an industrial robot due to thermal effects. Possible fields of application are the improvement of the friction compensation algorithms used for robot control systems and the prediction of energy consumption.
L’articolo presenta il programma di ricerca svolto dall’Università di Brescia nell’ambito del pro... more L’articolo presenta il programma di ricerca svolto dall’Università di Brescia nell’ambito del progetto PRIN (Progetto di Ricerca di Interesse Nazionale) dedicato allo studio di trasmissioni a camma. L’attività di ricerca, finanziata dal MIUR e dall’Università degli Studi di Brescia, si è articolata su studi a carattere sia teorico che sperimentale, entrambi finalizzati all’analisi dinamica e all’ottimizzazione del funzionamento di intermittori a camma. L’obiettivo finale riguarda lo sviluppo di nuove procedure assistite dal calcolatore, che consentano di migliorare le metodologie di progetto di questa particolare classe di meccanismi.
The paper presents a preliminary study on the feasibility of a Neural Networks based methodology ... more The paper presents a preliminary study on the feasibility of a Neural Networks based methodology for the calibration of Industrial Manipulators to improve their accuracy. A Neural Network is used to predict the pose inaccuracy due to general sources of error in the robot (e.g. geometrical inaccuracy, load deflection, stiffness and backlash of the mechanical members, etc ...) . The network is trained comparing the ideal model of the robot with measures of the actual poses reached by the robot. A back-propagation learning algorithm is applied. The Neural Network out- put can be used by the robot controller to compensate for the errors in the pose. The proposed calibration technique appears extremely simple. It does not need any information on the pose er- rors nature, but only the ideal robot kinematics and a set of experimental pose measures. Different schemes of calibration procedures are applied to a simulated SCARA robot and to a Stewart Plat- form and compared, in order to select...
L’articolo descrive l’attività di progettazione svolta da tre gruppi di ricerca dell’Università d... more L’articolo descrive l’attività di progettazione svolta da tre gruppi di ricerca dell’Università di Brescia, operanti nei settori disciplinari della Meccanica applicata alle macchine, delle Tecnologie e sistemi di lavorazione e del Disegno e metodi dell’Ingegneria industriale. Tale collaborazione rientra nell’attività di ricerca svolta nell'ambito del progetto REMS, finanziato dalla Regione Lombardia e coordinato dal CSMT (Centro Servizi Multisettoriale Tecnologico) di Brescia, il cui scopo primario è quello di realizzare una rete di eccellenza per la meccanica strumentale. Oltre all’Università di Brescia, il progetto vede coinvolti l’Istituto di Tecnologie Industriali e Automazione di Milano (ITIA-CNR), l’Università degli Studi di Bergamo e il Politecnico di Milano. Obiettivo finale della ricerca è la realizzazione di un sistema automatizzato per l’esecuzione di lavorazioni meccaniche con elevatissimo grado di precisione.
2019 23rd International Conference on Mechatronics Technology (ICMT), 2019
Objective: this paper presents an experimental study of the vibration phenomena in the dynamic we... more Objective: this paper presents an experimental study of the vibration phenomena in the dynamic weighing system of an automatic rotary filling machine for fluids. The study aims at the sensitivity analysis of the environmental vibrations when the operating conditions of the machine vary and at the identification of the principal causes of excitation. Methods: numerous experimental tests have been carried out on a dedicated test bench and on a complete machine with sixteen stations. For a filling station the load cell signal and the acceleration of the plate that supports the bottle have been acquired and studied. A one-degree of freedom model with varying mass has been implemented in a dedicated software in Delphi language for the vibration modelling. Results: a detailed sensitivity analysis has been developed. The model has allowed a deeper understanding of the phenomena that occur. It also showed the potentiality to be used for the vibration prediction in a compensation process.
2019 23rd International Conference on Mechatronics Technology (ICMT), 2019
This work presents an iterative methodology for reliability design of production equipment based ... more This work presents an iterative methodology for reliability design of production equipment based on the diagnostic and prognostic approach. The proposed method starts with the FMECA analysis in order to identify the main critical components of mechanical systems (e.g. robotic cells, robots, automatic machines). The mitigation actions are selected evaluating a design review of the project or imposing a maintenance strategy by critical component. This selection is defined by the calculated risk (e.g. risk priority number) and the life cycle cost assessment of the production equipment. The analysis of failure causes may support in evaluating preventive or predictive techniques focused on physical or data driven models. The use of a general database that collects and shares information from systems/components already installed in the field permits to analyse life and performance data in real time in an integrated closed loop. This research is a part of PROGRAMS: PROGnostics based Reliab...
Il lavoro riguarda l’analisi teorica delle vibrazioni meccaniche che si verificano in una partico... more Il lavoro riguarda l’analisi teorica delle vibrazioni meccaniche che si verificano in una particolare classe di dispositivi a camma, gli intermittori, utilizzati nelle macchine automatiche per generare moti intermittenti. L’attenzione `e rivolta in particolare ai casi in cui si utilizzano, come presa di moto, azionamenti a velocità variabile, oggi largamente utilizzati in ambito industriale grazie all’elevata diffusione di servomotori controllati. I punti essenziali dell’articolo sono i seguenti: a) descrizione di un modello matematico per meccanismi intermittori; b) definizione di metodologie di controllo per servomotori a velocità variabile, al fine di ridurre le vibrazioni degli organi meccanici; c) analisi e discussione dei risultati ottenuti dalle simulazioni numeriche.
Modeless industrial robot calibration plays an important role in the increasing employment of rob... more Modeless industrial robot calibration plays an important role in the increasing employment of robots in industry. This approach allows to develop a procedure able to compensate the pose errors without complex parametric model. The paper presents a study aimed at comparing neural-kinematic (N-K) architectures for a modeless non-parametric robotic calibration. A multilayer perceptron feed-forward neural network, trained in a supervised manner with the back-propagation learning technique, is coupled in different modes with the ideal kinematic model of the robot. A comparative performance analysis of different neural-kinematic architectures was executed on a two degrees of freedom SCARA manipulator, for direct and inverse kinematics. Afterward the optimal schemes have been identified and further tested on a three degrees of freedom full SCARA robot and on a Stewart platform. The analysis on simulated data shows that the accuracy of the robot pose can be improved by an order of magnitude...
The estimation of the friction torque in joints transmissions is a crucial task in the robotics f... more The estimation of the friction torque in joints transmissions is a crucial task in the robotics field. This work presents a model that describes the variations on friction that occur during the operations of an industrial robot due to thermal effects. The proposed technique is simple to implement and economically convenient. Possible applications are the improvement of the friction compensation algorithms used in control systems, the prediction of energy consumption and predictive maintenance
This paper describes different intelligent active modes to control an exoskeleton robotic device,... more This paper describes different intelligent active modes to control an exoskeleton robotic device, devoted to the hand rehabilitation. A position-based control with EMG signals and mirroring technique has been implemented, with two different possibilities: triggered ON_OFF control and proportional control. The developed control permits to perform robotic aided exercises for the hand rehabilitation, leveraging the mirroring effect so as to obtain a better neuron-motor recovery. A preliminary study for a force based control has been conducted. The close correlation between the EMG signal and the pressure inside a bottle, grasped by the hand, allows to demonstrate the correlation between the EMG signal and the force exerted. The structure of the possible force-control mode is than presented.
2021 24th International Conference on Mechatronics Technology (ICMT), 2021
Objective: The sit-to-stand transition is an important task for the evaluation of physical indepe... more Objective: The sit-to-stand transition is an important task for the evaluation of physical independence, especially in fragile subjects like elderly patients, to monitor and reduce the risk of falls or damage. This study aims at assessing the kinematic characteristics of the sit-to-stand transition from a quantitative perspective, using a wireless IMU sensor, and describes a set of parameters suitable for evaluating the movement performance in everyday practice. Methods: An acquisition campaign was designed and carried out on 20 healthy subjects and 13 patients to evaluate acceleration and angular velocity generated during a sit-to-stand task. For each subject, at least four acquisitions were performed, to create a final dataset of 173 acquisitions. The values of the proposed parameters were computed, and results were analyzed with descriptive statistics. Results: According to the proposed parameters definitions and the analyzed dataset, acceleration-and angular velocity-related parameters present statistically significant differences between healthy and pathological data samples, unlike total time TT.
Monitoring vibrations in rotating machinery allows effective diagnostics, as abnormal functioning... more Monitoring vibrations in rotating machinery allows effective diagnostics, as abnormal functioning states are related to specific patterns that can be extracted from vibration signals. Extensively studied issues concern the different methodologies used for carrying out the main phases (signal measurements, pre-processing and processing, feature selection, and fault diagnosis) of a malfunction automatic diagnosis. In addition, vibration-based condition monitoring has been applied to a number of different mechanical systems or components. In this review, a systematic study of the works related to the topic was carried out. A preliminary phase involved the analysis of the publication distribution, to understand what was the interest in studying the application of the method to the various rotating machineries, to identify the interest in the investigation of the main phases of the diagnostic process, and to identify the techniques mainly used for each single phase of the process. Subseq...
Cam follower mechanisms are widely used in automated manufacturing machinery to transform a rotar... more Cam follower mechanisms are widely used in automated manufacturing machinery to transform a rotary stationary motion into a more general required movement. Reverse engineering of cams has been studied, and some solutions based on different approaches have been identified in the literature. This article proposes an innovative method based on the use of an evolutionary algorithm for the identification of a law of motion that allows for approximating in the best way the motion or the sampled profile on the physical device. Starting from the acquired data, through a genetic algorithm, a representation of the movement (and therefore of the cam profile) is identified based on a type of motion law traditionally used for this purpose, i.e., the modified trapezoidal (better known as modified seven segments). With this method it is possible to estimate the coefficients of the parametric motion law, thus allowing the designer to further manipulate them according to the usual motion planning te...
Poly(dimethylsiloxane) (PDMS) is usually considered as a dielectric material and the PDMS microch... more Poly(dimethylsiloxane) (PDMS) is usually considered as a dielectric material and the PDMS microchannel wall can be treated as an electrically insulated boundary in an applied electric field. However, in certain layouts of microfluidic networks, electrical leakage through the PDMS microfluidic channel walls may not be negligible, which must be carefully considered in the microfluidic circuit design. In this paper, we report on the experimental characterization of the electrical leakage current through PDMS microfluidic channel walls of different configurations. Our numerical and experimental studies indicate that for tens of microns thick PDMS channel walls, electrical leakage through the PDMS wall could significantly alter the electrical field in the main channel. We further show that we can use the electrical leakage through the PDMS microfluidic channel wall to control the electrolyte flow inside the microfluidic channel and manipulate the particle motion inside the microfluidic channel. More specifically, we can trap individual particles at different locations inside the microfluidic channel by balancing the electroosmotic flow and the electrophoretic migration of the particle.
Exoskeletons are robots that closely interact with humans and that are increasingly used for diff... more Exoskeletons are robots that closely interact with humans and that are increasingly used for different purposes, such as rehabilitation, assistance in the activities of daily living (ADLs), performance augmentation or as haptic devices. In the last few decades, the research activity on these robots has grown exponentially, and sensors and actuation technologies are two fundamental research themes for their development. In this review, an in-depth study of the works related to exoskeletons and specifically to these two main aspects is carried out. A preliminary phase investigates the temporal distribution of scientific publications to capture the interest in studying and developing novel ideas, methods or solutions for exoskeleton design, actuation and sensors. The distribution of the works is also analyzed with respect to the device purpose, body part to which the device is dedicated, operation mode and design methods. Subsequently, actuation and sensing solutions for the exoskeleto...
This paper presents a model that describes the effect of heat exchange on dynamic friction in the... more This paper presents a model that describes the effect of heat exchange on dynamic friction in the joints of an industrial robot. As concern the modeling of friction as a function of the rotation speed of the joint, a third degree polynomial is used. The coefficients of the polynomial, which depends on the temperature, are estimated by means of a suitable identification procedure. The proposed technique is simple to implement and economically convenient. Experimental tests have shown that the method here proposed, despite its simplicity, can estimate with good reliability the variations of friction that occur during the operation of an industrial robot due to thermal effects. Possible fields of application are the improvement of the friction compensation algorithms used for robot control systems and the prediction of energy consumption.
L’articolo presenta il programma di ricerca svolto dall’Università di Brescia nell’ambito del pro... more L’articolo presenta il programma di ricerca svolto dall’Università di Brescia nell’ambito del progetto PRIN (Progetto di Ricerca di Interesse Nazionale) dedicato allo studio di trasmissioni a camma. L’attività di ricerca, finanziata dal MIUR e dall’Università degli Studi di Brescia, si è articolata su studi a carattere sia teorico che sperimentale, entrambi finalizzati all’analisi dinamica e all’ottimizzazione del funzionamento di intermittori a camma. L’obiettivo finale riguarda lo sviluppo di nuove procedure assistite dal calcolatore, che consentano di migliorare le metodologie di progetto di questa particolare classe di meccanismi.
The paper presents a preliminary study on the feasibility of a Neural Networks based methodology ... more The paper presents a preliminary study on the feasibility of a Neural Networks based methodology for the calibration of Industrial Manipulators to improve their accuracy. A Neural Network is used to predict the pose inaccuracy due to general sources of error in the robot (e.g. geometrical inaccuracy, load deflection, stiffness and backlash of the mechanical members, etc ...) . The network is trained comparing the ideal model of the robot with measures of the actual poses reached by the robot. A back-propagation learning algorithm is applied. The Neural Network out- put can be used by the robot controller to compensate for the errors in the pose. The proposed calibration technique appears extremely simple. It does not need any information on the pose er- rors nature, but only the ideal robot kinematics and a set of experimental pose measures. Different schemes of calibration procedures are applied to a simulated SCARA robot and to a Stewart Plat- form and compared, in order to select...
L’articolo descrive l’attività di progettazione svolta da tre gruppi di ricerca dell’Università d... more L’articolo descrive l’attività di progettazione svolta da tre gruppi di ricerca dell’Università di Brescia, operanti nei settori disciplinari della Meccanica applicata alle macchine, delle Tecnologie e sistemi di lavorazione e del Disegno e metodi dell’Ingegneria industriale. Tale collaborazione rientra nell’attività di ricerca svolta nell'ambito del progetto REMS, finanziato dalla Regione Lombardia e coordinato dal CSMT (Centro Servizi Multisettoriale Tecnologico) di Brescia, il cui scopo primario è quello di realizzare una rete di eccellenza per la meccanica strumentale. Oltre all’Università di Brescia, il progetto vede coinvolti l’Istituto di Tecnologie Industriali e Automazione di Milano (ITIA-CNR), l’Università degli Studi di Bergamo e il Politecnico di Milano. Obiettivo finale della ricerca è la realizzazione di un sistema automatizzato per l’esecuzione di lavorazioni meccaniche con elevatissimo grado di precisione.
2019 23rd International Conference on Mechatronics Technology (ICMT), 2019
Objective: this paper presents an experimental study of the vibration phenomena in the dynamic we... more Objective: this paper presents an experimental study of the vibration phenomena in the dynamic weighing system of an automatic rotary filling machine for fluids. The study aims at the sensitivity analysis of the environmental vibrations when the operating conditions of the machine vary and at the identification of the principal causes of excitation. Methods: numerous experimental tests have been carried out on a dedicated test bench and on a complete machine with sixteen stations. For a filling station the load cell signal and the acceleration of the plate that supports the bottle have been acquired and studied. A one-degree of freedom model with varying mass has been implemented in a dedicated software in Delphi language for the vibration modelling. Results: a detailed sensitivity analysis has been developed. The model has allowed a deeper understanding of the phenomena that occur. It also showed the potentiality to be used for the vibration prediction in a compensation process.
2019 23rd International Conference on Mechatronics Technology (ICMT), 2019
This work presents an iterative methodology for reliability design of production equipment based ... more This work presents an iterative methodology for reliability design of production equipment based on the diagnostic and prognostic approach. The proposed method starts with the FMECA analysis in order to identify the main critical components of mechanical systems (e.g. robotic cells, robots, automatic machines). The mitigation actions are selected evaluating a design review of the project or imposing a maintenance strategy by critical component. This selection is defined by the calculated risk (e.g. risk priority number) and the life cycle cost assessment of the production equipment. The analysis of failure causes may support in evaluating preventive or predictive techniques focused on physical or data driven models. The use of a general database that collects and shares information from systems/components already installed in the field permits to analyse life and performance data in real time in an integrated closed loop. This research is a part of PROGRAMS: PROGnostics based Reliab...
Il lavoro riguarda l’analisi teorica delle vibrazioni meccaniche che si verificano in una partico... more Il lavoro riguarda l’analisi teorica delle vibrazioni meccaniche che si verificano in una particolare classe di dispositivi a camma, gli intermittori, utilizzati nelle macchine automatiche per generare moti intermittenti. L’attenzione `e rivolta in particolare ai casi in cui si utilizzano, come presa di moto, azionamenti a velocità variabile, oggi largamente utilizzati in ambito industriale grazie all’elevata diffusione di servomotori controllati. I punti essenziali dell’articolo sono i seguenti: a) descrizione di un modello matematico per meccanismi intermittori; b) definizione di metodologie di controllo per servomotori a velocità variabile, al fine di ridurre le vibrazioni degli organi meccanici; c) analisi e discussione dei risultati ottenuti dalle simulazioni numeriche.
Modeless industrial robot calibration plays an important role in the increasing employment of rob... more Modeless industrial robot calibration plays an important role in the increasing employment of robots in industry. This approach allows to develop a procedure able to compensate the pose errors without complex parametric model. The paper presents a study aimed at comparing neural-kinematic (N-K) architectures for a modeless non-parametric robotic calibration. A multilayer perceptron feed-forward neural network, trained in a supervised manner with the back-propagation learning technique, is coupled in different modes with the ideal kinematic model of the robot. A comparative performance analysis of different neural-kinematic architectures was executed on a two degrees of freedom SCARA manipulator, for direct and inverse kinematics. Afterward the optimal schemes have been identified and further tested on a three degrees of freedom full SCARA robot and on a Stewart platform. The analysis on simulated data shows that the accuracy of the robot pose can be improved by an order of magnitude...
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Papers by Monica Tiboni