In robotics or machining, task quality is strongly linked to servo tuning. Indeed, geometrical an... more In robotics or machining, task quality is strongly linked to servo tuning. Indeed, geometrical and dynamic behavior of the mechanical structure could be degraded when a coarse tuning is achieved. Several P/PI or PID tuning methods can be used but generally uncorrelated with industrial context or mechanical considerations. In this paper, we propose a generic tuning method based on dynamic modeling of the mechanical structure and model parameters experimental identification. Therefore, the proposed tuning is adapted to the real dynamic behavior of the mechanical structure under task load while being sufficiently simple to be implemented in an industrial context. The method is illustrated on a vertical axis.
This article deals with the development of a simple model to evaluate the first natural frequenci... more This article deals with the development of a simple model to evaluate the first natural frequencies of over-constrained parallel kinematic machines (PKMs). The simplest elasto-dynamic models are based on multi-body approaches. However, these approaches require an expression of the Jacobian matrices that may be difficult to obtain for complex PKMs. Therefore, this paper focuses on the determination of the global mass and stiffness matrices of an over-constrained PKM in stationary configurations without the use of Jacobian matrices. The PKM legs are modeled by beams. Because the legs are connected to a moving platform and the mechanism is over-constrained, constraint equations between the parameters that model the deformation of each leg are determined according to screw theory. The first natural frequencies and associated modes can then be determined. It should be noted that the proposed method can be easily used at the conceptual design stage of PKMs. The Tripteor X7 machine is used...
The presence of flexibilities in rotational joints can limit the kinematic performances of manipu... more The presence of flexibilities in rotational joints can limit the kinematic performances of manipulators doing high speed tasks as Pick and Place. The problem addressed in this work concerns the vibration control of serial robots with flexible joints performing Pick and Place tasks in order to improve productivity. Based on a dynamic model of a robot with flexible joints, a model-based control law is proposed with its associated tuning methodology. The robot dynamic model is then the key point of our methodology. This dynamic model considers stiffness and damping of each flexible joint. To guarantee its accuracy, a geometrical and dynamic identification procedure is realized. The objective is to show the relevancy of the proposed approach which integrates joint flexibilities in the control law. Theoretical results based on a representative model are used to illustrate the benefit of this model-based control law compare to two other control strategies (Feedforward control and control ...
For the first time, a Nooru-Mohammed test was realized using a new kind of loading machine based ... more For the first time, a Nooru-Mohammed test was realized using a new kind of loading machine based on gough platform. However, it has been shown that boundary conditions on the concrete specimen are not respected. As a consequence, a new control strategy needs to be developed. This paper aims at applying a well-known control loop based on hybrid force/position law to a loading application. This new control algorithm has been developed according to the task and the structure specificities. Indeed, it permits to realize multi-axial test where the boundary conditions are controlled and respected by using the extra degrees of freedom.
In robotics or machining, task quality is strongly linked to servo tuning. Indeed, geometrical an... more In robotics or machining, task quality is strongly linked to servo tuning. Indeed, geometrical and dynamic behavior of the mechanical structure could be degraded when a coarse tuning is achieved. Several P/PI or PID tuning methods can be used but generally uncorrelated with industrial context or mechanical considerations. In this paper, we propose a generic tuning method based on dynamic modeling of the mechanical structure and model parameters experimental identification. Therefore, the proposed tuning is adapted to the real dynamic behavior of the mechanical structure under task load while being sufficiently simple to be implemented in an industrial context. The method is illustrated on a vertical axis.
This article deals with the development of a simple model to evaluate the first natural frequenci... more This article deals with the development of a simple model to evaluate the first natural frequencies of over-constrained parallel kinematic machines (PKMs). The simplest elasto-dynamic models are based on multi-body approaches. However, these approaches require an expression of the Jacobian matrices that may be difficult to obtain for complex PKMs. Therefore, this paper focuses on the determination of the global mass and stiffness matrices of an over-constrained PKM in stationary configurations without the use of Jacobian matrices. The PKM legs are modeled by beams. Because the legs are connected to a moving platform and the mechanism is over-constrained, constraint equations between the parameters that model the deformation of each leg are determined according to screw theory. The first natural frequencies and associated modes can then be determined. It should be noted that the proposed method can be easily used at the conceptual design stage of PKMs. The Tripteor X7 machine is used...
The presence of flexibilities in rotational joints can limit the kinematic performances of manipu... more The presence of flexibilities in rotational joints can limit the kinematic performances of manipulators doing high speed tasks as Pick and Place. The problem addressed in this work concerns the vibration control of serial robots with flexible joints performing Pick and Place tasks in order to improve productivity. Based on a dynamic model of a robot with flexible joints, a model-based control law is proposed with its associated tuning methodology. The robot dynamic model is then the key point of our methodology. This dynamic model considers stiffness and damping of each flexible joint. To guarantee its accuracy, a geometrical and dynamic identification procedure is realized. The objective is to show the relevancy of the proposed approach which integrates joint flexibilities in the control law. Theoretical results based on a representative model are used to illustrate the benefit of this model-based control law compare to two other control strategies (Feedforward control and control ...
For the first time, a Nooru-Mohammed test was realized using a new kind of loading machine based ... more For the first time, a Nooru-Mohammed test was realized using a new kind of loading machine based on gough platform. However, it has been shown that boundary conditions on the concrete specimen are not respected. As a consequence, a new control strategy needs to be developed. This paper aims at applying a well-known control loop based on hybrid force/position law to a loading application. This new control algorithm has been developed according to the task and the structure specificities. Indeed, it permits to realize multi-axial test where the boundary conditions are controlled and respected by using the extra degrees of freedom.
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Papers by Hélène Chanal