Identification of Flexible Joints in Vehicle Structures

A method for identification of flexible joints in vehicle structures is presented. The method identifies the most important parameters of a joint model and estimates their values by using displacement measurements of the overall structure. Thus, the method can be used to develop simple, design-oriented joint models that are suitable for preliminary structural design. The viability of the proposed method is demonstrated by applying it to plane frame structures with flexible joints. Nomenclature b = vector of parameter estimates bj = vector of parameter estimates obtained by using the y'th data subset C — covariance matrix Cjb — covariance matrix of parameters obtained by the jth data subset / = force vector K = global stiffness matrix Kj = stiffness matrix of a joint KR = stiffness matrix of the vehicle structure without joints u = vector of displacements um = vector of measured displacements u = vector of estimated displacements jc = vector of regressor variables Z = matrix of sensitivity derivatives of the displacements with respect to the parameters of the joints j8 = vector of parameters of a joint model y = the vector of transformed joint parameters in principal direction analysis e = vector of measurement errors (n) = combinations of n objects taken m at a time Subscripts b = vector of parameter estimates s = vector of measurement errors