Flat Approach Research Articles

Hybrid Terrestrial and Aerial Quadrotor Control

A recent breakthrough in aerial mobile robotics appears with the quadrotor platform. It is particularly suitable for indoor exploration because of its high stability, manoeuvrability and because of the possibility to hover. However quadrotors suffer from their energy consumption and can only fly about 15 minutes. A new design of quadrotor is then proposed in this paper and allows it to move on the ground for energy saving purposes. This paper only focuses on the terrestrial control. A 3DOF non linear dynamic modeling of the terrestrial displacement is firstly obtained and then control laws for trajectory tracking and point stabilization are designed. A flatness approach is used for tracking purpose and a non linear time-varying control law is proposed for point stabilization. The second approach is justified by the fact that the system does not satisfy Brockett's theorem. Simulation results also underline the similar dynamic behaviour of our system with hovercrafts.

Optimal Sizing Design and Energy Management of Stand-alone Photovoltaic/Wind Generator Systems

Presently, the photovoltaic (PV) and the wind energies are the most important energetic alternative resources. So far, a lot of researches are developed and conducted concerning the cost-optimally design and energy management for the stand-alone hybrid PV-wind generator (WG) systems. In this study, a methodology for optimal sizing design and strategy control based on differential flatness approach is applied to the hybrid stand-alone PV-WG systems. The purpose is to find the optimal number of units ensuring that the 20 years round total system cost is minimized subject to the constraint that the load energy requirements are completely covered. The optimization methodology, using the genetic algorithm and the formulation of the problem are detailed. Finally, an optimal configuration is obtained with a lifetime of 20 years; also the results of the control algorithm based on the flatness properties obtained under Matlab/Simulink are given.

Control of PEMFC system air group using differential flatness approach: Validation by a dynamic fuel cell system model

In this paper, a non linear control strategy is applied to the air supply subsystem of a polymer electrode membrane fuel cell (PEMFC). Based on a simplified control model and using the differential flatness control theory, a controller is designed in order to regulate the most important variables in the air supply subsystem: the oxygen stoechiometry and the cathode pressure. Simulations are made using a very detailed model validated experimentally, which allows the evolution of different state variables in the stack to be observed during the power deliver operation. The simulation results show that the controller gives a good response in terms of performance, robustness and durability of the system, despite the dynamics power profiles demanded, the approximations made and the disturbances.

Real-Time Cooperative Trajectory Planning Using Differential Flatness Approach and B-Splines

This paper proposed a cooperative receding horizon optimal control framework, based on differential flatness and B-splines, which was used to solve the real-time cooperative trajectory planning for multi-UCAV performing cooperative air-to-ground target attack missions. The planning problem was formulated as a cooperative receding horizon optimal control problem (CRHC-OCP), and then the differential flatness and B-splines were introduced to lower the dimension of the planning space and parameterize the spatial trajectories. Moreover, for the dynamic and uncertainty of the battlefield environment, the cooperative receding horizon control was introduced. Finally, the proposed approach is demonstrated, and the results show that this approach is feasible and effective.

Null controllability of the 1D heat equation using flatness

We derive in a straightforward way the null controllability of a 1-D heat equation with boundary control. We use the so-called flatness approach, which consists in parameterizing the solution and the control by the derivatives of a “flat output”. This provides an explicit control law achieving the exact steering to zero. We also give accurate error estimates when the various series involved are replaced by their partial sums, which is paramount for an actual numerical scheme. Numerical experiments illustrate the interest of the approach.

Backstepping and flatness approaches for stabilization of the stick-slip phenomenon for drilling

In this article, we propose control solutions to suppress undesirable torsional oscillations of the drill string in oil well drilling systems. Two feedback control laws are derived from Partial Differential Equations (PDE) models capturing the main features of the so-called stick-slip phenomenon. Comparative simulations highlight the merits of the two approaches.

Comparative study on control concepts of a robot manipulator with multiple‐link/joint flexibilities

AbstractIf one is dealing with active vibration suppression on a highly nonlinear flexible system, various techniques are needed. On the one hand a suitable dynamic model of the system is required. And on the other hand intelligent model based control concepts are necessary for active vibration damping. We deal with a basic model, where the flexibilities are approximated with linear springs and dampers, a so called lumped element model (LEM). For the control design we propose a control structure with two degrees of freedom (2DoF) for solving the tracking problem, based on the LEM. Such an approach allows designing the feedforward part independently of the feedback part. Hereby the feedforward control is based on the flatness approach, while for the feedback control several strategies are studied using acceleration‐ and gyrosensor‐measurements. The contribution is completed with a validation by measurements from a very fast trajectory on an articulated robot with two flexible links and three elastic joints. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

State estimation on flexible robots using accelerometers and angular rate sensors

Fast moving robots with elastic joints and/or elastic links require vibration suppression to achieve accuracy. We introduce a two-degrees-of-freedom control scheme (2DoF) consisting of a feedforward component based on the flatness approach and a classic feedback component, such as a PD motor joint control with additional link position error or joint torque error feedback. Such a control scheme requires knowledge of the full system state. We present an approach for state estimation using angular rate-and acceleration-sensors-mounted on each robot link-that can be used for any kind of elastic robot manipulator. We validate our theory by measuring a very fast trajectory and the influence of an external disturbance on an articulated robot with two flexible links and three joints.

Flatness Approach to Fault Parametric Detection of Systems

In this paper a flatness approach to fault parameter detection is proposed. Our main contribution in this work consists in the synthesis of a flat moving horizon estimator for a supervision industrial process. The effectiveness of the proposed method is shown through the supervise of a series DC motor. The obtained results are very satisfactory in terms of detection rapidity and precision relatively to the case where the classic state estimator is adopted.

Control of a Three-Level Boost Converter Based on a Differential Flatness Approach for Fuel Cell Vehicle Applications

This paper presents a high-gain boost converter (three-level converter and transformerless converter) for fuel cell (FC) vehicle applications. An original nonlinear control law based on the flatness principle for distributed dc generation is studied. Utilizing the flatness property, we propose simple solutions to the system performance and stabilization problems. The design controller parameters are straightforward and autonomous at the operating point. To validate the proposed method, a prototype FC power converter (1.2-kW three-level boost converter) is developed in the laboratory. The proposed control law is implemented with a digital estimate in a dSPACE 1104 controller card. The experimental results from the laboratory using a 1200-W and 46-A polymer electrolyte membrane FC (PEMFC) verify that this is a good control scheme.

Design and Fabrication of the First Tribometer in Pakistan

Tribometer is an instrument that offers precise and repeatable wear/friction measurement of a surface. The coefficient of friction is a dimensionless scalar value which describes the ratio of the force of friction between two bodies. It is an empirical measurement; it has to be measured experimentally, and cannot be found through calculations. This tribometer measures coefficient of friction between any two materials in dry test scenario using flat bed approach; moreover it measures both kinetic and dynamic coefficient of friction. As emphasized in the title it is first of its kind being fabricated in Pakistan, which is a huge achievement considering the fact that not much research work is being done in this field in Pakistan. This tribometer is designed to prioritize accuracy and manufacturing cost.

Intentionality in a Creative Art Curriculum

Abstract This paper highlights inadequacies of a creative arts curriculum that claimed to have been informed by postmodern theories, without careful consideration of how these might or should impact on teaching and learning interactions. In particular, the relationship between intentionality and interpretation addressed in this case study is of concern for educationalists in a postmodern world. At issue is how assessors’ interpretations are responsive to or balanced with student meaning making. Drawing from research conducted at a South African fine art department, the author considers whether a transfer of Barthes’s notion of author to student intentionality and reader to lecturer interpretation is a constructive framework for student learning. In the case studied, flat approaches to the poststructuralist “intentionality fallacy” were found to further exacerbate unequal power dynamics, with detrimental effects on student learning. An argument is made for more ethically aware approaches to the balance between interpretation and intentionality by recognizing that it echoes the relationship between self and other.

A Flatness‐Based Controller for the Stabilization of the Inverted Pendulum

We propose a flatness based approach for controlling the inverted pendulum cart system, under the assumption that the pendulum state is always located on a vicinity of its unstable equilibrium point. This is achieved by representing the original system, as a chain of integrators with an additive nonlinear state dependent perturbation. After discarding the small nonlinear perturbation, we may directly use design tools provided by the the flatness approach. The effectiveness and robustness of the obtained control law, which turned out to have a large domain of attraction, were numerically assessed in the context of stabilization and, also, for a reference oscillatory trajectory tracking task.

Design of Digital Filters for Si Wafer Surface Profile Measurement - Noise Reduction by Wavelet Transform -

Recently in semiconductor industry, production of ever flatter, thinner and larger silicon wafers are required to fulfill the demands of high-density packaging and cost reduction. In geometric evaluation of Si wafers, according to SEMI (Semiconductor Equipment and Materials International) standards, the required wafer flatness approaches to the 22 nanometers by year 2016 [1]. For such application, uncertainty of measured data is encountered as a severe problem because high resolution instrument always incorporate a certain degree of noise. In order to precisely evaluate the wafer profile, it is essential to remove the noise from the measured data. Described in this paper is design and development of digital filters for denoising. Compared to the conventional low-pass filters, the developed filter by use of wavelet transform not only provides better performance of decomposition in the spatial frequency domain, but also offers the new capability of denoising in amplitude domain.

Design of Digital Filters for Si Wafer Surface Profile Measurement – Noise Reduction by Lifting Scheme Wavelet Transform

Recently in semiconductor industry, production of ever flatter, thinner and larger silicon wafers are required to fulfill the demands of high-density packaging and cost reduction. In geometric evaluation of Si wafers, according to SEMI (Semiconductor Equipment and Materials International) standards, the required wafer flatness approaches to the 22 nanometers by year 2016 [1]. For such application, uncertainty of measured data is encountered as a severe problem because the requirement has met the limit of available instrument in terms of resolution and reliability. In order to precisely evaluate the wafer profile, it is essential to remove the noise from the measured data. Described in this paper is design and development of digital filters for denoising. In previous paper, digital filters for denoising with Haar wavelet transform are described. In this paper, the new filters by use of 2nd generation wavelet transform (lifting scheme) are proposed and show better performance of decomposition in the spatial frequency domain and amplitude domain.

Erratum to: Statistical condensation adsorption isotherms of gas molecules adsorbed on porous adsorbents, surface monolayer adsorption isotherms and hysteresis phenomena

Condensation adsorption isotherms of type IV (or V) according to BDDT classification on porous adsorbents composed of one or two groups of adsorption sites are derived statistically. When Βc1 (or Βc2) is less than unity, the isotherm becomes type IV, and when it is greater than unity, the isotherm becomes type V. It is understood that the negative sign(-) of the additional adsorption energy, q, in the nth layer in deriving those theoretical isotherms plays a decisive role on the horizontally flat approach to the axis of the isotherm near the saturation vapor pressure. The values of the surface area can be calculated easily. The pore radii of all the adsorbents which we have obtained by using the derived isotherms with respect to the appropriately selected experimental data agree with those obtained by using the Kelvin equation. Many surface mono-layer adsorption isotherms are obtained in the process of deriving the various adsorption isotherms. From them we can learn that the surface sites are not adsorbed completely even near the saturated vapor pressure, and we can find the range of error by comparing them with vms of the BET equation. We could mention through judging the results of a great deal of the experimental isotherm data of types IV and V that “the cause of hysteresis phenomena of the condensation adsorption-desorption of gases is originated from the deviation from the thermodynamically reversible adsorption-desorption process in the condensation adsorption-desorption of gases”.

An Improved Quadrilateral Flat Element with Drilling Degrees of Freedom for Shell Structural Analysis

This paper reports the development of a simple and efficient 4-node flat shell element with six degrees of freedom per node for the analysis of arbitrary shell structures. The element is developed by incorporating a strain smoothing technique into a flat shell finite element approach. The membrane part is formulated by applying the smoothing operation on a quadrilateral membrane element using Allman-type interpolation functions with drilling DOFs. The plate-bending component is established by a combination of the smoothed curvature and the substitute shear strain fields. As a result, the bending and a part of membrane stiffness matrices are computed on the boundaries of smoothing cells which leads to very accurate solutions, even with distorted meshes, and possible reduction in computational cost. The performance of the proposed element is validated and demonstrated through several numerical benchmark problems. Convergence studies and comparison with other existing solutions in the literature suggest that the present element is efficient, accurate and free of lockings.

Robust terminal area energy management guidance using flatness approach

This study deals with the design of a guidance scheme based on flatness theory and dedicated to the terminal area energy management phase of a reusable launch vehicle. The proposed guidance strategy is based on a non-linear dynamic inversion technique to handle the large flight envelope that characterises the reentry mission. This inversion takes advantage of a particular choice of linearising terms called flat outputs, that are used to perform an input-to-state linearisation. First, it is shown that the coupled in-plane and out-of-plane vehicle dynamics admits a set of flat outputs. The flatness property of this model is then used to compute the nominal control input profiles corresponding to a single reference trajectory computed off-line. Based on the linearised model obtained by dynamic inversion, a linear tracking controller is then designed so as to circumvent off-nominal flight conditions. Finally, robustness and performances of the proposed guidance scheme are assessed by performing Monte Carlo runs within an industrial simulation environment.

Coupled linear parameter varying and flatness-based approach for space re-entry vehicles guidance

An linear parameter varying guidance method for the hypersonic phase of a space re-entry vehicle is presented. The suggested guidance scheme, relying on flatness approach, is applied to the non-linear model of the European Atmospheric Re-entry Demonstrator. It is shown that the overall guidance scheme achieves robust stability and performance, even in the presence of entry point kinematics dispersions. The design problem is formulated and solved using a finite set of linear matrix inequalities. Finally, Monte Carlo simulation results are presented to demonstrate the effectiveness of the suggested approach.

Flatness-based hypersonic reentry guidance of a lifting-body vehicle

This paper deals with the design of a guidance algorithm for the hypersonic phase of a lifting-body vehicle. The guidance strategy is based on a particular kind of nonlinear dynamic inversion, the so-called flatness approach. The main advantage of this approach is that the longitudinal guidance law is in-flight self-adaptive to any feasible hypersonic trajectory and can be written in analytical form with a small set of design parameters. Therefore, the required on-board computational resources are limited, and a reduced off-line design effort is needed for the change of vehicle parameters. Moreover, the closed-loop longitudinal guidance commands are computed on-board in a coupled way without relying on an explicit deceleration profile. Consequently, the approach leads to an efficient management of the degree of freedom associated with the angle-of-attack. PID controllers are then designed based on the longitudinal flat model in order to circumvent uncertainties and parameters dispersions. The crossrange is controlled by a series of bank reversals determined by an azimuth error deadband. The robustness and performance of the proposed guidance law are assessed by performing Monte Carlo runs with various sets of dispersions.