MULTIBODY DYNAMICS 2009, ECCOMAS Thematic Conference K. Arczewski, J. Fr ˛ aczek, M. Wojtyra (eds.) Warsaw, Poland, 29 June–2 July 2009 SYMBOLIC CALCULATION OF THE BASE INERTIAL PARAMETERS OF ROBOTS THROUGH DIMENSIONAL ANALYSIS Xabier Iriarte , Javier Ros and Vicente Mata Mechanical, Energetic and Materials Engineering Department Public University of Navarra, Campus Arrosadia s/n, 31006 Pamplona, Navarra, Spain e-mails: xabier.iriarte@unavarra.es,jros@unavarra.es web page: http://www.imac.unavarra.es Mechanical Engineering Department Polytechnic University of Valencia, Camino de Vera s/n, 46022 Valencia, Spain e-mail: vmata@mcm.upv.es Keywords: Base Parameters, Inertial Parameters, Robots, Symbolic, Dimensional Analysis. Abstract. The inverse dynamic model of a multibody system is used for many applications in engineering. A very interesting property of these models is that they can be written in a linear form with respect to the inertial parameters of the solids, provided that some conditions hold. This property is very helpful in fields like dynamic parameter identification, design optimization, model reduction and others. Due to the movement constraints that the joints impose to the bodies of a system, the columns of the matrix that represents the equations of the inverse dynamic system, may appear as a linear combinations of each other, making the systems dynamics dependent, not on single inertial parameters but on linear combinations of them. These combinations are called Base Inertial Parameters. Knowing the symbolic expressions of these base parameters is a very interesting information in some disciplines. That is the reason why much effort was made in the 90’s to calculate them for open- and closed-loop systems. There have been two approches for the calculation of these parameters, the numeric and the symbolic ones. The numeric approches happened to be easier to implement and more system independent, while the symbolic approaches were more involved and not easily applicable to closed-loop systems. In this paper a new approach is presented for the calculation of the symbolic expressions of the base inertial parameters of robots. This approach is based on Dimensional Analysis applied to the base parameters expressions obtained by a numeric method, and also on the underlying structure of the coefficients of the expressions. This makes much easier to guess the hidden symbolic expressions, and makes the method much easier and faster than the previous approaches, specially when dealing with closed-loop mechanisms. 1