The Influence of Heat Exchanges on Friction in Robotic Joints: Theoretical Modelling, Identification and Experiments

2020 ◽  
Author(s):  
Roberto Pagani ◽  
Giovanni Legnani ◽  
Giovanni Incerti ◽  
Manuel Beschi ◽  
Monica Tiboni
Keyword(s):  
Thermal Effects ◽  
Rotation Speed ◽  
Industrial Robot ◽  
Experimental Tests ◽  
Theoretical Modelling ◽  
Degree Polynomial ◽  
Identification Procedure ◽  
Good Reliability ◽  
Robotic Joints ◽  
Heat Exchanges

Abstract 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.

The Influence of Heat Exchanges on Friction in Robotic Joints: Theoretical Modelling, Identification and Experiments

2021 ◽  
Author(s):  
Roberto Pagani ◽  
Giovanni Legnani ◽  
Giovanni Incerti ◽  
Manuel Beschi ◽  
Monica Tiboni
Keyword(s):  
Theoretical Modelling ◽  
Robotic Joints ◽  
Heat Exchanges

Estimation of Damping for Turbine Blades in Non-Stationary Working Conditions

2015 ◽  
Author(s):  
Luigi Carassale ◽  
Michela Marrè-Brunenghi ◽  
Stefano Patrone
Keyword(s):  
Power Plants ◽  
Rotation Speed ◽  
Thermal Power ◽  
Turbine Blades ◽  
Experimental Tests ◽  
Strain Gauges ◽  
Identification Procedure ◽  
Time Frequency ◽  
Run Up ◽  
Critical Components

Turbine blades are critical components in thermal power plants and their design process usually includes experimental tests in order to tune or confirm numerical analyses. These tests are generally carried out on full-scale rotors having some blades instrumented with strain gauges and usually involve a run-up and/or a run-down phase. The quantification of damping in these conditions is rather complicated, since the finite sweep velocity produces a distortion of the vibration amplitude in contrast to the Frequency-Response Function that would be expected for an infinitely slow crossing of the resonance. In this work, we show through a numerical simulation that the usual identification procedures lead to a systematic overestimation of damping due both to the finite sweep velocity, as well as to the variation of the blade natural frequency with the rotation speed. An identification procedure based on the time-frequency analysis is proposed and validated through numerical simulations.

Modelling and Evaluation of the Friction in Robotic Joints Considering Thermal Effects

2019 ◽  
Author(s):  
Giovanni Legnani ◽  
Giovanni Incerti ◽  
Roberto Pagani ◽  
Matteo Gheza
Keyword(s):  
Industrial Robot ◽  
Low Cost ◽  
Experimental Tests ◽  
Industrial Applications ◽  
Friction Model ◽  
Friction Torque ◽  
Working Cycle ◽  
Robotic Joints ◽  
Increasing Temperature ◽  
The Mathematical Model

Abstract The paper presents a second order friction model for the joints of industrial robot manipulators that takes into account temperature effects. A solution based on a polynomial description of the friction is proposed. The theoretical analysis and the experimental measurements have shown that friction decreases with increasing temperature, which in turn depends on the working cycle of the manipulator. The mathematical model here proposed allows to foresee the friction variation during extensive working cycles and it does not require the use of a transducer for the measurement of the joint internal temperature; therefore it is well suitable for low-cost industrial applications, to improve the control performance or to predict the energy consumption. Experimental tests performed on a commercial 6 DOF manipulator show that the model is effective in estimating the joint temperature and the friction torque during the robot operations.

Evaluation and Modeling of the Friction in Robotic Joints Considering Thermal Effects

2020 ◽  
Vol 12 (2) ◽  
Author(s):  
Roberto Pagani ◽  
Giovanni Legnani ◽  
Giovanni Incerti ◽  
Matteo Gheza
Keyword(s):  
Degrees Of Freedom ◽  
Industrial Robot ◽  
Low Cost ◽  
Experimental Tests ◽  
Industrial Applications ◽  
Friction Model ◽  
Friction Torque ◽  
Working Cycle ◽  
Robotic Joints ◽  
Increasing Temperature

Abstract The paper presents a second-order friction model for the joints of industrial robot manipulators that takes into account temperature effects. A solution based on a polynomial description of the friction is proposed. The theoretical analysis and the experimental measurements have shown that friction decreases with increasing temperature, which in turn depends on the working cycle of the manipulator. The mathematical model here proposed allows to foresee the friction variation during extensive working cycles and it does not require the use of a transducer for the measurement of the joint internal temperature; therefore it is well suitable for low-cost industrial applications, to improve the control performance or to predict the energy consumption. Experimental tests performed on a commercial six degrees-of-freedom (6 DOF) manipulator show that the model is effective in estimating the joint temperature and the friction torque during the robot operations.

Optimization of performance in multi-cell beams with different surface slopes for use in vehicle structure using a multi-objective evolutionary algorithm based on decomposition

2021 ◽  
pp. 146442072199784
Author(s):  
S Chahardoli ◽  
Mohammad Sheikh Ahmadi ◽  
TN Tran ◽  
Afrasyab Khan
Keyword(s):  
Decomposition Method ◽  
Experimental Tests ◽  
Surface Slope ◽  
Optimal Model ◽  
Degree Polynomial ◽  
Numerical Tests ◽  
Numerical Studies ◽  
Surface Slopes ◽  
Vehicle Structure ◽  
Number Of Cells

This study examined the effect of the upper surface slope and the number of cells in the side beams on the collapse properties using experimental and numerical tests. The numerical studies were conducted with LS-DYNA software, and the accuracy of numerical results was investigated by experimental tests. Using MATLAB software, the second-degree polynomial functions were obtained for the collapse properties of the specimens. Also, after the optimization by the decomposition method, the best mode was introduced for the specimens. The studies on collapse properties showed that increasing the number of cells leads to a decrease in all collapse properties, and increasing the upper surface slope leads to an increase in the collapse properties. Moreover, the optimization results by decomposition method showed that this method could suggest the most optimal model for multi-cell and sloping beams.

scholarly journals Human–Robot Interaction through Eye Tracking for Artistic Drawing

Robotics ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 54
Author(s):  
Lorenzo Scalera ◽  
Stefano Seriani ◽  
Paolo Gallina ◽  
Mattia Lentini ◽  
Alessandro Gasparetto
Keyword(s):  
Eye Tracking ◽  
Assistive Technology ◽  
Movement Disorders ◽  
Industrial Robot ◽  
Experimental Tests ◽  
Human Robot Interaction ◽  
Eye Tracker ◽  
Robot Interaction ◽  
Eye Motion ◽  
Artistic Images

In this paper, authors present a novel architecture for controlling an industrial robot via an eye tracking interface for artistic purposes. Humans and robots interact thanks to an acquisition system based on an eye tracker device that allows the user to control the motion of a robotic manipulator with his gaze. The feasibility of the robotic system is evaluated with experimental tests in which the robot is teleoperated to draw artistic images. The tool can be used by artists to investigate novel forms of art and by amputees or people with movement disorders or muscular paralysis, as an assistive technology for artistic drawing and painting, since, in these cases, eye motion is usually preserved.

Identification of Tire Model Parameters Through Full Vehicle Experimental Tests

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Francesco Braghin ◽  
Federico Cheli ◽  
Edoardo Sabbioni
Keyword(s):  
Laboratory Tests ◽  
Experimental Tests ◽  
Contact Forces ◽  
Lateral Acceleration ◽  
Design Stage ◽  
Model Parameters ◽  
Tire Model ◽  
Identification Procedure ◽  
Sideslip Angle ◽  
Tyre Model

Individual tire model parameters are traditionally derived from expensive component indoor laboratory tests as a result of an identification procedure minimizing the error with respect to force and slip measurements. These parameters are then transferred to vehicle models used at a design stage to simulate the vehicle handling behavior. A methodology aimed at identifying the Magic Formula-Tyre (MF-Tyre) model coefficients of each individual tire for pure cornering conditions based only on the measurements carried out on board vehicle (vehicle sideslip angle, yaw rate, lateral acceleration, speed and steer angle) during standard handling maneuvers (step-steers) is instead presented in this paper. The resulting tire model thus includes vertical load dependency and implicitly compensates for suspension geometry and compliance (i.e., scaling factors are included into the identified MF coefficients). The global number of tests (indoor and outdoor) needed for characterizing a tire for handling simulation purposes can thus be reduced. The proposed methodology is made in three subsequent steps. During the first phase, the average MF coefficients of the tires of an axle and the relaxation lengths are identified through an extended Kalman filter. Then the vertical loads and the slip angles at each tire are estimated. The results of these two steps are used as inputs to the last phase, where, the MF-Tyre model coefficients for each individual tire are identified through a constrained minimization approach. Results of the identification procedure have been compared with experimental data collected on a sport vehicle equipped with different tires for the front and the rear axles and instrumented with dynamometric hubs for tire contact forces measurement. Thus, a direct matching between the measured and the estimated contact forces could be performed, showing a successful tire model identification. As a further verification of the obtained results, the identified tire model has also been compared with laboratory tests on the same tire. A good agreement has been observed for the rear tire where suspension compliance is negligible, while front tire data are comparable only after including a suspension compliance compensation term into the identification procedure.

scholarly journals Blade Tip-timing Technology with Multiple Reference Phases for Online Monitoring of High-speed Blades under Variable-speed Operation

2018 ◽  
Vol 18 (6) ◽  
pp. 243-250 ◽  
Author(s):  
Zhang Ji-wang ◽  
Zhang Lai-bin ◽  
Ding Ke-Qin ◽  
Duan Li-xiang
Keyword(s):  
High Speed ◽  
Online Monitoring ◽  
Rotation Speed ◽  
Experimental Tests ◽  
Reference Points ◽  
Variable Speed ◽  
Rotating Shaft ◽  
Virtual Reference ◽  
Blade Tip ◽  
Multiple Reference

Abstract High-speed blades form core mechanical components in turbomachines. Research concerning online monitoring of operating states of such blades has drawn increased attention in recent years. To this end, various methods have been devised, of which, the blade tip-timing (BTT) technique is considered the most promising. However, the traditional BTT method is only suitable for constant-speed operations. But in practice, the rotational speed of turbomachine blades is constantly changing under the influence of external factors, which lead to unacceptable errors in measurement. To tackle this problem, a new BTT method based on multi-phases is proposed. A plurality of phases was arranged as evenly as possible on the rotating shaft to determine the rotation speed. Meanwhile, the corresponding virtual reference point was determined in accordance with the number of blades between consecutive phases. Based on these reference points, equations to measure displacement due to blade vibrations were deduced. Finally, mathematical modeling, numerical simulation and experimental tests were performed to verify the validity of the proposed method. Results demonstrate that the error in measurement induced when using the proposed method is less than 1.8 %, which is much lower compared to traditional methods utilized under variable-speed operation.

scholarly journals Waste heat recovery from Refrigeration machine

2019 ◽  
Vol 9 (2) ◽  
pp. 185-190
Keyword(s):  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Sea Water ◽  
Waste Heat ◽  
Experimental Tests ◽  
Air Conditioner ◽  
Heat Exchanges ◽  
Refrigeration Machine ◽  
New System ◽  
Good Agreement

With the aim of saving energy and to reduce global warming effect, our work focuses on the valorization of the waste heat evacuated by the condenser of a refrigeration machine (air-conditioner) for the desalination of sea water. In this paper, the conception of a new system combining airconditioning and desalination is realized. The modelling of the heat exchanges of each part of the system is realized. To improve the performance of the system, various experimental tests are represented and discussed. Comparison between simulation and experimental results shows a good agreement and present a courageous motive for the system application.

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