The software DCAP (Dynamic and Control Analysis Package) has been in development by ESA since the early 1980s, under several industrial contracts. The most recent version was issued by the ESA's Mechanisms section in cooperation with Thales Alenia Space Italy. The package is now in its eighth release, combining a number of state of the art features, among which a 'symbolic' formulation for the non-linear dynamics of multibody rigid and flexible systems, with time-varying mass characteristics. Suitable interfaces to MATLAB, Simulink, and GUI visualisation are provided. The package allows for alternative, independently-coded simulation with consistent I/O files, allowing for highly reliable cross-validation of results.
Activities performed in the Section in support to projects with DCAP are described in the Multibody General Applications page (see the right navigation).
DCAP Release 4.0 included a Lagrange formulation of multibody dynamics (dyns20), originally developed at Martin Marietta in the 1970s for the NASA program DISCOS (Frisch H.P. Goddard, Space Centre, “Dynamic Interaction Simulation of Controls and Structures (DISCOS)” 1979, GSC -12422) and oriented towards user-defined subroutines.
DCAP Release 5.0 included a set of generic elements to replace the user-defined software. Intermediate versions, under the name of Esa-MIDAS, were produced. Esa-MIDAS Release 6.0, embedding a minimal dimension formulation (dyns30), was made available to ESTEC but not released to users.
DCAP Release 7.0 reflected a fundamental change in the contents of the package. The most significant change was the replacement of the non-linear time history simulation programs (dyns20, and dyns30) with a new simulation program based on a minimum dimension Order(n) algorithm. The equations of motion are generated symbolically by a dedicated symbolic processor in the form of FORTRAN code, which is then compiled and linked to form a highly efficient simulation module. This program now functionally replaces dyns20 and dyns30 for most simulation cases but they are still in use for cross checking of results, and for multiple closed loop configuration cases that are not supported by the order-N formulation. Another major change was the addition of a GUI that included a graphical full-screen version of the old INCAP program as well as a sophisticated 3D graphics modelling and animation facility, running on Unix / Silicon Graphics workstations. Other changes included a substantial enhancement of the generic elements with additions such as manipulators, brakes, transitions and controller reconfiguration.
A complementary software program, DCAP-RT (Real Time simulator), was developed, having the main objective of allowing fast calculations for generic multibody dynamics. The code was also based on a minimal dimension order-N formulation and symbolic coding. DCAP-RT could generate C or FORTRAN code for the multi body system. The running shell was developed in C. DCAP-RT has features very similar to the DCAP-7, while additionally being interfaced to several modules describing in detail the typical functioning of sensors and actuators. DCAP-RT is able to interface with MATRIX-X and EUROSIM (real time simulation) code.
DCAP Release 8.0, only available for ESTEC related applications, is an enhancement to the DCAP software primarily addressing variable mass topologies, sensitivity analysis, interface to MATLABSimulink, and the development of a GUI based on JAVA and Open GL. This new release combines and enhances features of both DCAP7 and DCAP –RT, allowing the execution of either code set in a unified data and graphical user interface environment.
A file based interface between the multibody programs DCAP and SIMPACK was develepped in order to thank advantage of SIMPACK pre-processor for interactive graphical model set-up and postprocessor for plot and animation.
Work on implementing a new 'constraint' feature has started in order to solve multiple 'closed loops'-like problems.
Last update: 20 October 2014