Quantitative validation techniques a database. (I). Simple examples

This paper proposes the formulation of a database of validation examples. This initial contribution describes the problem of validation of the simulation of two real systems. These include a mechanical network and a thermal system with a transport delay. Data of the component values and measurements are reported here. The data from testing these systems will be made available at a later stage to enable other workers to compare other validation techniques with those presented here.The responses of a mechanical and a thermal system were measured with a laptop PC and Labview via a DAQCard^TM-700 data acquisition card. Simulations were made with ACSL and ACSL Math.The validation procedures implemented included a parameter variation with integral quadratic weighting and ITAE weighting together with a statistical matching technique using a correlation coefficient.These techniques illustrate the problem of achieving “good” validation to within a few percentage points. Correlation coefficients of over 98% were obtained for the fitting of linear models, with Theil indices of less than 0.075.     

Passive velocity field control (PVFC). Part I. Geometry androbustness

Passive velocity field control is a control methodology for fully actuated mechanical systems, in which the motion task is specified behaviorally in terms of a velocity field, and the closed-loop system is passive with respect to a supply rate given by the environment power input. The control law is derived geometrically and the geometric and robustness properties of the closed-loop system are analyzed. It is shown that the closed-loop unforced trajectories are geodesics of a closed-loop connection which is compatible with an inertia metric, and that the velocity of the system converges exponentially to a scaled multiple of the desired velocity field. The robustness property of the system exhibits some strong directional preference. In particular, disturbances that push in the direction of the desired momentum do not adversely affect the performance. Moreover, robustness property also improves with more energy in the system     

Passive velocity field control (PVFC). Part II. Application tocontour following

When the contour following task is represented by a velocity field on the configuration manifold of the system, the coordination aspect of the problem is made explicit. The PVFC scheme developed in the Part I (ibid. vol.29(9) (2001)) can then be applied to track the defined velocity field. However, for some contours, an encoding velocity held on the configuration manifold does not exist or is difficult to define and, as a consequence, the PVFC cannot be directly applied. For systems whose configuration manifolds are compact Lie groups and the desired contour is represented by a parameterized trajectory, a general methodology is developed, using a suspension technique, to define a velocity field on a manifold related to the configuration manifold of the system for which PVFC can be applied. With this strategy, timing along the contour can be naturally varied online by a self-pacing scheme so that the contour tracking performance can be improved. The experimental results for a 2-DOF robot following a Lissajous contour illustrates and verifies the convergence and robustness properties of the PVFC methodology