An Inverse Dynamics Approach to Control Lyapunov Functions

With the goal of moving towards implementation of increasingly dynamic behaviors on underactuated systems, this paper presents an optimization-based approach for solving full-body dynamics based controllers on underactuated bipedal robots. The primary focus of this paper is on the development of an alternative approach to the implementation of controllers utilizing control Lyapunov function based quadratic programs. This approach utilizes many of the desirable aspects from successful inverse dynamics based controllers in the literature, while also incorporating a variant of control Lyapunov functions that renders better convergence in the context of tracking outputs. The principal benefits of this formulation include a greater ability to add costs which regulate the resulting behavior of the robot. In addition, the model error-prone inertia matrix is used only once, in a non-inverted form. The result is a successful demonstration of the controller for walking in simulation, and applied on hardware in real-time for dynamic crouching

La notion de hasard : Ses différentes définitions et leurs utilisations

Jusqu’à Blaise Pascal, le hasard désigne ce qui se produit en dehors de tout dessein humain ou divin et de tout ordre stable. Après lui, on cherche à préciser de façon constructive ces trois types d’exclusion, ce qui amène à définir les événements merveilleux, les événements aléatoires et les événements accidentels. Chacune de ces trois démarches a ses avantages et ses inconvénients. La première rend compte de tout ce qui étonne, mais écarte la liberté et le miracle et ne permet ni vérification, ni prévision, ni décision. La seconde permet des prévisions et des vérifications expérimentales, mais son emploi ne peut se généraliser sans entrer en conflit avec le déterminisme, qui la considère comme une illusion. La troisième explique beaucoup de choses par la rencontre de séries causales indépendantes, mais ce faisant elle exclut toute finalité. Il faut faire très attention à ne pas les confondre.Until Blaise Pascal, chance meant what happens outside any human or divine design or any stable order. Attempts are made, ever since, to set down in a constructive fashion those three types of exclusion : what it is that leads to define marvellous events, chance events and accidental events. Each of those three endeavours has its advantages and its drawbacks. The first accounts for everything that amazes, but it sets aside freedom and miracle, and does not allow any verification, prevision, or decision. The second permits previsions and experimental verifications, but its use cannot be generalized without entering into conflict with determinism, which considers it an illusion. The third explains a number of things through the encounter of independent causal series, but, while so doing, it excludes all finality. One must be very cautious not to confuse the three

The Main Determinants of Insurance Purchase: An Empirical Study on Crop Insurance Policies in France

Using data for 2002-2005 on a representative survey of French farms (FADN-RICA), we investigate the different factors that lead farmers to insure against crop risk. Our analysis takes into account a mix of both standard individual, financial and agricultural criteria. Cross-sectional and longitudinal analyses as well as logistic regressions underline the main differences between insured and non-insured farms. Compared to non-insured farms, we find that insured farms present greater financial and agricultural sizes, a more diversified production and have been motivated by the occurrence of recent catastrophic climatic events. Although essential in the cross-sectional analysis, the influence of financial parameters in the decision to insure is mitigated. On the other hand, the agricultural characteristics of the farms confirm their leading influence for the subscription of crop insurance policies.Insurance, Demand, Crop insurance, Catastrophe risk, Risk and Uncertainty,