22 research outputs found
A behavioral approach to inversion-based control
No full textA new simplified behavior theory is proposed to address inversion-based control for linear, nonminimum-phase SISO systems. The chosen space of signals is the set of piecewise C∞-functions and input–output pairs (as weak solutions) satisfy a differential–integral equation with additional smoothness requirements. A related key result is the output–input (or inverse) representation of the behavior set that leads to the solution of a general stable inversion problem where polynomially unbounded, noncausal desired outputs are allowed. It is shown that this problem has a solution if and only if the smoothness degree of the desired output is greater than or equal to the system relative degree minus one. When this straightforward condition is satisfied, a closed-form expression provides the inverse input. Then, an analysis on preaction and postaction control follows. Two examples are included showing the relevance of output signal design in control applications
Induced connections on virtual holonomic constraints
No full textA virtual holonomic constraint is a relation among the coordinates of a mechanical system that can be made invariant via feedback control. This paper frames virtual holonomic constraints in an affine geometry setting, describing the dynamics on the constraint as the geodesics of a connection (the induced connection) derived from the Levi-Civita connection of the mechanical system. It also presents conditions for the constraint dynamics to be Lagrangian, based on the metrizability properties of the induced connection
Inverse Feedforward Control with Output Polynomial Smoothing
No full textA method of polynomial smoothing is presented for the inverse feedforward control of continuous-time, linear, nonminimum-phase SISO (single-input single-output) systems. Starting from an arbitrarily given output signal, a smoothing procedure is devised to obtain a delayed smoothed output for which stable input-output inversion can be applied. This procedure requires to solve a polynomial interpolating problem whose solution is given by a polynomial parameterized by the smoothing time parameter. Detailed expressions of the deduced inverse input are provided. The minimization of the smoothing time is also pursued in order to reduce the delay in the smoothed output. Examples highlight the proposed method. The aim of the presented approach is to achieve high-performances in a variety of possible control applications such as, e.g., those in process automation and mechatronics
A coordinate-free theory of virtual holonomic constraints
No full textThis paper presents a coordinate-free formulation of virtual holonomic constraints for underactuated Lagrangian control systems on Riemannian manifolds. It is shown that when a virtual constraint enjoys a regularity property, the constrained dynamics are described by an affine connection dynamical system. The affine connection of the constrained system has an elegant relationship to the Riemannian connection of the original Lagrangian control system. Necessary and sufficient conditions are given for the constrained dynamics to be Lagrangian. A key condition is that the affine connection of the constrained dynamics be metrizable. Basic results on metrizability of affine connections are first reviewed, then employed in three examples in order of increasing complexity. The last example is a double pendulum on a cart with two different actuator configurations. For this control system, a virtual constraint is employed which confines the second pendulum to within the upper half-plane
Minimum-time feedforward control of an open liquid container
No full textThe paper considers a minimum-time feedforward motion control problem for an open container carrying a liquid. The proposed solution is a time-continuous acceleration planning that avoids liquid spilling and satisfies amplitude constraints on jerk, acceleration, and velocity of the container moving on a linear guide of an automation line. This solution is based on linear programming and can provide rest-to-rest liquid motion planning or, alternatively, a rest-to-disequilibrium planning with bounded post-motion liquid oscillations. Experimental results on a test bench prototype show the effectiveness of the presented approach
Pressure matching with optimized target phase for personal sound zone systems
No full textPressure matching (PM) is an advanced digital signal processing technique aimed at designing loudspeaker filters to achieve a target acoustic field in a desired sound region. This enables to establish personal sound zones (PSZs) in a desired environment. The target sound field is chosen during
the design stage and influences the performance of the system in terms of acoustic contrast (AC) between bright and dark zones, as well as fidelity of the reproduced audio. The sound regions are represented by groups of control points (microphones) properly placed in the considered environment. With more than one control point in the bright region, the same target sound field is usually considered for all the microphones. This paper investigates the optimization of the phase of the target acoustic field required by the PM algorithm in terms of AC. The achievable performance is analyzed in a realistic automotive environment with two sound zones and two control points per zone. The numerical results show a potential improvement of the achievable AC at the cost of some spatial effects and possibly non constant group delay in the reproduced sound, which should nonetheless be tolerable in voice applications
Optimisation of the target sound fields for the generation of independent listening zones in a reverberant environment
No full textThe Pressure Matching Method (PMM) has been widely used in individual listening zones (ILZ) systems to create multiple independent sound zones in the same environment. This method aims to reproduce a set of target acoustic fields in several control zones, using one or more loudspeaker arrays. These target fields are parameters of the ILZ algorithm that are defined at the design stage. In this work, we compare the effects of several target sound field alternatives on the sound field control system performance and robustness. The proposed target fields prevent the ILZ system from focusing its effort on unessential tasks such as the dereverberation of the acoustic environment. More specifically, we compare target acoustic fields of a single active loudspeaker, of several active and in-phase loudspeakers or of a set of loudspeakers acting as a beamformer steered towards one of the zones to be controlled. Results of simulations and experiments obtained with one compact loudspeaker array in the interior of a real car are presented as well as a study on the robustness to perturbations of the solutions obtained with the various choices of target acoustic fields
Performance Analysis of Feedback MIMO ANC in Experimental Automotive Environment
No full textIn this paper, a performance analysis of FeedBack (FB) Active Noise Cancellation (ANC) systems for automotive applications is presented. Since the performance of FB ANC systems is strongly impaired by the delay induced by the physical distance between microphones and loudspeakers, an experimental setup representative of a car seat headrest has been developed. In this setup, the loudspeaker-microphone distance is on the order of few centimeters. An experimentally acquired band-limited noise source is obtained from an idling car. Noise reduction is performed by using a Filtered-x Least Mean Square (FxLMS) algorithm. Two 2×2 Multiple Input - Multiple Output (MIMO) schemes are considered—standard one and Filtered-Error (FE) based. Our experimental results show that the proposed MIMO systems enable improved performance and are able to control the perceived noise at two listening positions in a realistic automotive application
