Macroscopic simulation of the liner honing process

The form quality, the roughness and the surface appearance produced by honing minimizes the friction of the piston in the liner. The process is however mechanically complex and the selection of the process parameters is currently based on empirical methods. The aim of this paper is thus to develop a macroscopic simulation environment of complete real honing cycles, which will help end-users during the setting-up. This virtual tool is based on a space-time discretization and a macroscopic cutting model taking into account local contacts between the workpiece and the abrasive tool. The space-time discretization allows representing the machine environment with the tool, the workpiece and the kinematics. Simulation results are finally validated by comparison with industrial experiments.Thèse CIFRe Renault SAS / MSMP PôleProcess ECO

Simulation of Roughness and Surface Texture Evolution at Macroscopic Scale During Cylinder Honing Process

The honing process produces surface liners with specific functional properties. Engine performances and life expectancy are directly impacted by the quality of honed surface. The form quality, the roughness and the surface appearance manufactured by honing determine the friction of the piston in the liner. The process is however mechanically complex and the selection of the process parameters is currently based on empirical methods. The aim of this paper is thus to develop a macroscopic simulation environment which will help end-users during this setting-up stage. The development of this virtual tool is based on a space-time discretization and a macroscopic cutting model taking into account local contacts between the workpiece and the abrasive stones. The space-time discretization allows representing the machine environment including the tool, the workpiece and the machine kinematics. The cutting model allows converting kinematics and abrasive contacts in dynamic data and material removal rate by calculation. The cutting model is initially adjusted based on simple experiments. The stock removal equation is then extrapolated to the whole range of stone cutting conditions. This approximation allows simulating the real process and a whole honing cycle. Results are validated by comparison with industrial context experiments. The simulation of the whole honing cycle allows predicting the form quality, one of the roughness criteria and the surface appearance. Moreover, simulation results are represented by means of maps that allow looking at quality criteria for each point of the surface

Model-based versus model-free control designs for improving microalgae growth in a closed photobioreactor: Some preliminary comparisons

Controlling microalgae cultivation, i.e., a crucial industrial topic today, is a challenging task since the corresponding modeling is complex, highly uncertain and time-varying. A model-free control setting is therefore introduced in order to ensure a high growth of microalgae in a continuous closed photobioreactor. Computer simulations are displayed in order to compare this design to an input-output feedback linearizing control strategy, which is widely used in the academic literature on photobioreactors. They assess the superiority of the model-free standpoint both in terms of performances and implementation simplicity.Comment: The 24th Mediterranean Conference on Control and Automation (MED'16), Athens, Greece (June 21-24, 2016

Flexible right sized honing technology for fast engine finishing

The paper discusses a flexible honing technology by describing the new prototype machine with its specificity. Three original methods produced by the flexible honing prototype have been studied. A path combines the two contemporary methods of industrial honing: the helical slide honing at 135 ° at the bottom of the cylinder and the conventional honing at 45 ° on the upper part. This method of honing shows the effectiveness of specific motion tracking to remove traces of inversions. Circular trajectories with large radii can be traveled quickly without consuming too much energy. The high cutting speed promotes the removal of material thus saving time. Finally, the multi-circle paths can get original textures thus proving the feasibility of all patterns

Explicit predictive control laws. On the geometry of feasible domains and the presence of nonlinearities.

International audienceThis paper is dealing with the receding horizon optimal control techniques having as main goal the reduction of the computational effort inherent to the use of on-line optimization routines. The off-line construction of the explicit solution for the associated multiparametric optimization problems is advocated with a special interest in the presence of nonlinearities in the constraints description. The proposed approach is a geometrical one, based on the topology of the feasible domain. The resulting piecewise linear state feedback control law has to accept a certain degree of suboptimality, as it is the case for local linearizations or decompositions over families of parametric functions. In the presented techniques, this is directly related to the distribution of the extreme points on the frontier of the feasible domain

Explicit predictive control laws with a nonlinear constraints handling mechanism

International audienceThis paper is dealing with the receding horizon optimal control techniques having as main goal the reduction of the computational effort inherent to the use of on-line optimization routines. The off-line construction of the explicit solution for the associated multiparametric optimization problems is advocated with a special interest in the presence of nonlinearities in the constraints description. The proposed approach is a geometrical one, based on the topology of the feasible domain. The resulting piecewise linear state feedback control law has to accept a certain degree of suboptimality, as it is the case for local linearizations or decompositions over families of parametric functions. In the presented techniques, this is directly related to the distribution of the extreme points on the frontier of the feasible domain

Axis control using model predictive control: identification and friction effect reduction

International audienceThis paper treats the identification and control of a machining center by means of predictive control, specifically focusing on the aspect of reducing friction effect. The machine tool is a five-axis CNC Mikron machine, in the context of HSM "High Speed Machining", with open control architecture. The axes are internally controlled by current and speed PI controllers in a classical cascade framework. In an external position loop, a predictive controller is considered instead of a classical position proportional controller with a feed forward action. The novelties stressed in the paper are the identification and the tuning of the predictive controller in order to reduce the impact of the frictions. The two-degree of freedom controller obtained using predictive strategy permits to adjust separately the tracking performance and the disturbance rejection. The tracking performance is tuned to reduce the contour error and the disturbance rejection is tuned by means of a disturbance model in order to reduce the friction impact. First, based on a nonlinear simulation model considering the frictions in the axis, a numerical model is derived by least square identification. Afterwards this numerical model is used to synthetize a predictive GPC controller reducing the impact of the friction. The benefit of the proposed structure is analyzed by means of experimental tests and a comparison with the classical position loop control with speed feed-forward. The experimental results are obtained for a two-axis trajectory, showing that the resulting experimental contour errors are smaller using the predictive controller. As perspective the paper proposes to use a control structure including only an internal current controller and external predictive position loop, without velocity loop

High-performance NC for high-speed machining by means of polynomial trajectories

International audienceThis paper summarises works carried out for defining tool trajectory formats well adapted to High Speed Machining (HSM). Advantages in using native polynomial formats, calculated directly from the CAD model, are highlighted. In particular, polynomial surface formats are presented as a generic format for tool trajectory. Illustrations show that surface formats represent a good compromise between smoothness machining time, and surface quality

Tractable Predictive Control Strategies For Heating Systems In Buildings

International audienceModel Predictive control is an advanced control tech-nique that has been used to optimize thermal comfort in buildings. Nowadays, the new buildings are char-acterized by an important inertia as well as low power heating systems. Since the thermal losses are very low, taking into account the intermittent occupancies in the control strategy is questionable. More precisely, in this paper, two model predictive controllers are devel-oped to reduce energy consumption while preserving the thermal comfort. These strategies keep using the local controllers and they are adapted for being imple-mented in embedded systems. The simulation results show lower energy consumptions and higher comfort levels in comparison with non-predictive strategies