1,721,059 research outputs found
Diego de Silva y Velázquez, copia da, Ritratto di papa Innocenzo X Pamphilj, scheda in Ritratto di una collezione. Pannini e la Galleria del Cardinale Silvio Valenti Gonzaga, a cura di R. Morselli, R. Vodret, catalogo della mostra, Mantova, Palazzo Te, 6 marzo-15 maggio 2005, Milano, Skira, 2005, p. 232
No full textNella scheda si analizza una copia da Diego de Silva y Velázquez del Ritratto di papa Innocenzo X Pamphil
Third order trajectory generator satisfying velocity, acceleration and jerk constraints
No full textA third order continuous-time trajectory generator useful in motion control systems is presented. The proposed non linear system receives as input a standard reference signal r(t) (step, ramp, etc.) and provides as output a smooth signal x(t) satisfying the following constraints on velocity, acceleration and jerk: Vmin ≤ ẋ(t) ≤ Vmax, Ami ≤ ẍ(t) ≤ Amax and |x| ≤ U. The generated trajectory tracks the reference signal in minimum time compatible with the constraints on the time-derivatives. The performance of the presented trajectory generator is tested in simulation
Positioning trajectory generator with nonlinear constraints
No full textA smooth trajectory generator useful in motion control systems is presented. The considered generator is a second order nonlinear system which receives as input a step reference signal and provides as output a smooth reference signal satisfying proper nonlinear constraints on the state variables as, for example, bounds on the first time-derivative ẋ of the output x, or bounds expressed in the form |ẍ| ≤ UM(x). The imposed constraints can also be changed during system operation without modifying the system stability. Moreover, almost minimum time response is ensured with guaranteed no overshoot. Finally, the performance of the the nonlinear generator is tested through simulation
Generation of acceleration profiles for smooth gear shift operations
No full textThe main goal of the engine-gear-clutch electronic control system is to improve the performance of the vehicle even in terms of passenger's comfort. Based on trajectory generation techniques, this paper proposes a nonlinear filter for the generation of comfortable car acceleration profiles during automatic gear shift operations. The passenger's head oscillations are evaluated by means of a head-neck dynamic model validated by experimental measurements. The on-line generation of the acceleration profiles ensures the required flexibility. The paper proposes also a methodology that can easily be extended either to fit with different comfort specifications or to match driveline constraints
Second order smooth trajectory generator with nonlinear constraints
No full textA smooth trajectory generator useful in motion control systems is presented. The considered generator is a second order nonlinear system which receives as input a standard reference signal (step, ramp, etc.) and provides as output a smooth reference signal satisfying proper nonlinear constraints on the state variables as, for example, bounds on the first time-derivative x of the output x, or bounds expressed in the form x ≤ U(x). The imposed constraints can also be changed during system operation without modifying the system stability. Moreover, almost minimum time response is ensured with guaranteed no overshoot. Only the second order continuous-time case is considered. Finally, the performance of the the nonlinear generator is tested through simulation experiments
Modeling of Automotive Control Systems Using Power Oriented Graphs
No full textThe basic idea of the Power-Oriented Graphs (POG) modeling technique is to use the power interaction between subsystems as basic concept for modeling. This approach is theoretically supported by the definition and the properties of the port-controlled Hamiltonian systems and allows the modeling of a wide variety of systems involving different energetic domains. Differently from the Bond Graphs technique, based on the same concept, the POG modeling technique solves explicitly the causality problem. By this way, the POG schemes are easily readable, close to the computer implementation and allow reliable simulations using every computer simulator. This paper introduces the properties of the POG technique and presents some examples related to automotive control systems. © 2006 IEEE
CONTROL OF PORT HAMILTONIAN SYSTEMS BY DISSIPATIVE DEVICES AND ITS APPLICATION TO IMPROVE THE SEMI-ACTIVE SUSPENSION BEHAVIOUR
No full textThe port Hamiltonian framework is a powerful tool for modeling a wide class of nonlinear systems such as robots and, more generally, mechatronic systems. A wide variety of mechatronic systems are controlled by operating dissipative components and the standard approaches for the control of port Hamiltonian systems are not applicable. Facing the limitation that the controlled devices can only dissipate power, the issue is to find a proper control law to satisfy the control requirements. This paper proposes to choose the control inputs to lead the input power of a subsystem in oder to satisfy the requirements by controlling the energy stored or the power dissipated in that subsystem. A slight extension of the definition of port Hamiltonian system is proposed to allow the description of a larger set of mechatronic systems. Although some important issues remain open, the example of the semi-active suspension shows that some positive results can be achieved by applying the proposed approach. Copyright © 2006 IFAC
Simulation of variable dynamic dimension systems: The clutch example
No full textDue to the presence of strong non-linearities (i.e. coulomb friction) some systems change their dynamic dimension while functioning. Such systems can be found in many application fields, such as in automotive and robotics. This paper proposes a simulation model for this type of systems that we will call as 'Variable Dynamic Dimension Systems' (VDDS). Particularly, a VDDS system composed by n masses which slip and interact together by means of the coulomb friction is analyzed. A congruent state space transformation is used to obtain a simple and effective simulation model for the system. The performances of the model are tested through simulation experiments applied to an interesting automotive application: A clutch with torsional damper-spring
Performance study of dispatching algorithms in multi-tier Web architectures
No full textThe number and heterogeneity of requests to Web sites are increasing also because the Web technology is becoming the preferred interface for information systems. Many systems hosting current Web sites are complex architectures composed by multiple server layers with strong scalability and reliability issues. In this paper we compare the performance of several combinations of centralized and distributed dispatching algorithms working at the first and second layer, and using different levels of state information. We confirm some known results about load sharing in distributed systems and give new insights to the problem of dispatching requests in multi-tier cluster-based Web systems
Self-tuning control strategy for antilock braking systems
No full textOne of the main issue of any control strategy for braking systems is to face the many uncertainties due to the strong spread of the system's parameters: road conditions, hydraulic actuators, tire behaviour, etc. Moreover, the need for cheap components limits both the number of sensors and the quality of the actuators. This paper proposes a self-tuning control strategy for braking systems. The proposed control strategy is based on two light assumptions: 1) the tire longitudinal force as a function of the tire slip has always a unique minimum; 2) the hydraulic actuators can increase, decrease and hold the braking pressure within a limited delay. Only the measure of the wheel rotational speed and the estimate of the wheel angular acceleration are required. The control strategy is tested by simulation experiments. © 2006 IEEE
- …
