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An example of distortion of a rotating ventilator observed with a Rolling Shutter camera: static object (right image) and moving object (left image).
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This paper proposes an original and novel vision sensing method to be used in vision-based dynamic identification of parallel robots. Indeed, it is shown that in the latter problem one requires to estimate (to the least) or measure (to the best) the end-effector pose and its time derivatives. The sensor we propose, based on a clever modelling of CM...
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... To overcome the impact of high temperatures, non-contact methods are a good choice. There are various non-contact speed measurement systems, such as the Global Positioning System (GPS) [5,6], laser Doppler velocimetry [7], radar velocimetry [8], and stereo-vision techniques [9][10][11][12][13]. However, when GPS is used indoors, the signal can be disturbed by the building, which ultimately affects its measurement accuracy. ...
The ram speed of a steam hammer is an important parameter that directly affects the forming performance of forgers. This parameter must be monitored regularly in practical applications in industry. Because of the complex and dangerous industrial environment of forging equipment, non-contact measurement methods, such as stereo vision, might be optimal. However, in actual application, the field of view (FOV) required to measure the steam hammer is extremely large, with a value of 2–3 m, and heavy steam hammer, at high-speed, usually causes a strong vibration. These two factors combine to sacrifice the accuracy of measurements, and can even cause the failure of measurements. To solve these issues, a bundle-adjustment-principle-based system calibration method is proposed to realize high-accuracy calibration for a large FOV, which can obtain accurate calibration results when the calibration target is not precisely manufactured. To decrease the influence of strong vibration, a stationary world coordinate system was built, and the external parameters were recalibrated during the entire measurement process. The accuracy and effectiveness of the proposed technique were verified by an experiment to measure the ram speed of a counterblow steam hammer in a die forging device.
... Indeed, it allows to directly measure the Cartesian pose of the parallel robot while traditional proprioceptive measure requires the calculation of the forward kinematic model. This idea was adopted in [30,1] using vision system for motion tracking purposes. To our knowledge, the use of cameras as position sensor in addition to the force sensor has never been suggested in the literature for the force control and motion tracking of parallel structures, whereas, it has been widely invoked in the case of serial manipulators. ...
... Notice that even the end effector velocity measurement can be available from vision according to [1]. A more recent work developed in our laboratory [9] uses a strategy based on an acquisition of selected regions of interest which decreases the density of the transmitted data. ...
In this paper, force and position control of parallel kinematic machines are discussed. Cartesian space computed torque control is applied to achieve force and position servoing directly in the task space within a sensor-based control architecture. The originality of the approach resides in the use of a vision system as an exteroceptive pose measurement of a parallel machine tool for force control purposes. Three different mechanical structures with different degrees of freedom are considered to validate the approach.
... As mentioned in Sect. 1, this solution was early depicted as convenient for serial robots to achieve force and position control regarding the complementarity between the force and vision sensors; whereas, in the case of parallel robots, coupling vision and force is indeed more than convenient since it additionally avoids the Forward Kinematic problem and allows to compensate for the kinematic errors due to presence of several chains and passive joints in the parallel structures. Notice that even the end effector velocity measurement can be available from vision according to a recent work developed in our laboratory [1,9] and, therefore, no numerical differentiation may appear in the motion control loop. As far as stability and robustness are concerned, the proposed control algorithm should Fig. 3 The proposed parallel force/vision control be superior to the one proposed by Callegari since it is a pure state feedback control. ...
The aim of this paper is to study force and position control of kinematic parallel machines. Relying on a recent work showing
that computed torque control in Cartesian space is suitable for parallel structures, we propose a parallel force position
control scheme of a parallel robot based on the visual servoing of the end effector pose. Simulation results show the efficiency
of the proposed approach.
KeywordsParallel robots–Force control–Parallel control–Visual servoing
... Dans cette optique, la vision artificielle est une solution très attrayante. L'idée d'élaborer une commande référencée vision pour le suivi de trajectoires dans l'espace cartésien par un robot parallèle a été adoptée dans (Paccot et al., 2007) ; (Ait-Aider et al., 2006 ). Le couplage d'une commande référencée vision avec un retour d'effort pour un robot parallèle n'as pas été évoqué dans la littérature. ...
... Il est important de noter qu'un système de vision peut également fournir une mesure de la vitesse cartésienne (Ait-Aider et al., 2006). Des travaux plus récents dans notre laboratoire (Dahmouche et al., 2008Pashkevich et al., 2006) qui s'écrit, sous l'hypothèse de perpendicularité des trois axes moteur : ...
position/force des machines à cinématique parallèle est étudiée dans cet article. Une architecture de commande référencée capteurs est présentée. Celle-ci est ba-sée sur une commande par couple calculé dans l'espace cartésien permettant l'asservissement simultané de la pose cartésienne et des efforts de contact effecteur/environnement directement dans l'espace de la tâche. L'originalité de l'approche réside dans l'integration d'un système de vision comme outil de mesure de pose à une commande en effort d'un robot parallèle. ABSTRACT. In this paper, force and position control of parallel kinematic machines is discussed. Cartesian space computed torque control is applied to achieve force and position servoing directly in the task space within a sensor based control architecture. The originality of the ap-proach resides in the use of a vision system as an exteroceptive pose measurement of a parallel machine tool for force control purposes. MOTS-CLÉS : Robots parallèles, commande en effort, commande parallèle, asservissement visuel.
... For medical application, Deblaise and Maurine, (2005) presented an effective and simple calibration method based on 1D and 3D measurements of a low cost artifact and validated on the Surgiscope, which is a structure based on a Delta robot used in neurosurgery. In addition, Ait-Aider et al. (2006) sets out a method to be applied in the dynamic identification. A camera is used to simultaneously measure the pose of the end-effector of the visual pattern calibrated and its Cartesian speed by using a single view. ...
Some of the main investigations on calibration methods of parallel mechanisms are briefly discussed in this work. Initially, the identification of errors in these structures applied to machine tools is presented, later the kinematics and the concept of parallel mechanisms calibration is introduced. Additionally, the main characteristics of the existing methods of calibration are discussed, such as the parametrical approaches, the calibration methods with internal/external measuring devices, innovative calibration methods and works that provide assistance to this aim.
... For medical application, Deblaise and Maurine, (2005) presented an effective and simple calibration method based on 1D and 3D measurements of a low cost artifact and validated on the Surgiscope, which is a structure based on a Delta robot used in neurosurgery. In addition, Ait-Aider et al. (2006) sets out a method to be applied in the dynamic identification. A camera is used to simultaneously measure the pose of the end-effector of the visual pattern calibrated and its Cartesian speed by using a single view. ...
This paper shows the applicability of a neurofuzzy method applied to a tomato plant (Lycopersicon esculentum, Mill), in order to obtain a model of the instantaneous evapotranspiration. Two operational dynamics (diurnal and nocturnal) are defined in a hierarchical fuzzy model by a TakagiSugeno (TS) type with linear consequents. The fuzzy selector of the two dynamics is the solar radiation measure. The fuzzy Cmeans algorithm is used to identify the fuzzy rules premises. The hierarchical fuzzy modelling is used to obtain a multimodel of the evapotranspiration cycles. In order to simplify the model structure, the variable of vapour pressure deficit (VPD) is introduced, and thus, a physical interpretation of the interior climate is obtained. VPD helps to preserve the quality and production level in the greenhouse crop.
... For medical application, Deblaise and Maurine, (2005) presented an effective and simple calibration method based on 1D and 3D measurements of a low cost artifact and validated on the Surgiscope, which is a structure based on a Delta robot used in neurosurgery. In addition, Ait-Aider et al. (2006) sets out a method to be applied in the dynamic identification. A camera is used to simultaneously measure the pose of the end-effector of the visual pattern calibrated and its Cartesian speed by using a single view. ...
... Third, since the control is essentially based on the direction of each leg, one may think of extracting the latter from the image of a generally shaped leg. Finally, we plan to extend this framework to any parallel mechanism, and we started to put effort into the development of high-speed vision tools to cope with the high velocities of parallel mechanisms [52]. ...
In this paper, it is shown that computer vision, used as an exteroceptive redundant metrology mean, simplifies the control of a Gough-Stewart parallel robot. Indeed, contrary to the usual methodology, where the robot is modeled independently from the control law which will be implemented, we take into account that vision will be used for control, from the early modeling stage. Hence, kinematic modeling and projective geometry are fused into a control-devoted projective kinematic model. Thus, a novel vision-based kinematic modeling of such a robot is proposed through the observation of its legs. Inspired by the geometry of lines, this model unifies and simplifies both identification and control. Indeed, it has a reduced parameter set, and allows us to propose a linear solution to its calibration. Using the same model, a visual servoing scheme is presented, where the attitudes of the nonrigidly linked legs are servoed, rather than the end-effector pose. Finally, theoretical results concerning the stability of this control law are provided
Cameras offer a unique capability of collecting high density spatial data from a distant scene of interest. They can be employed as remote monitoring or inspection sensors to measure vibrating objects because of their commonplace availability, simplicity, and potentially low cost. A defect of vibrating measurement with the camera is to process the massive data generated by camera. In order to reduce the data collected from the camera, the camera using electronic rolling shutter (ERS) is applied to measure the frequency of one-dimensional vibration, whose frequency is much higher than the speed of the camera. Every row in the image captured by the ERS camera records the vibrating displacement at different times. Those displacements that form the vibration could be extracted by local analysis with sliding windows. This methodology is demonstrated on vibrating structures, a cantilever beam, and an air compressor to identify the validity of the proposed algorithm. Suggestions for applications of this methodology and challenges in real-world implementation are given at last. © 2018 Society of Photo-Optical Instrumentation Engineers (SPIE).
