Modeling, analysis and constrained control of wet cone clutch systems: A synchromesh case study

This paper addresses the problem of controlling the regime of lubrication in sliding lubricated surfaces with the purpose of wear reduction and the lifetime increase of the friction lining material. To this end, the hydrodynamic, mixed, and boundary lubrication regimes in a cone clutch system are experimentally investigated and a piecewise linear approximation of the Stribeck curve is presented. The friction-induced temperature rise and its effect on viscosity reduction, wear, and dynamic uncertainty are discussed. A modified wear model of the cone clutch is proposed by taking into account the contributions of both the mixed and boundary lubrication regimes. Using the obtained wear model, the necessity of the operation in the mixed lubrication regime is shown, and the duration of the operation is determined. The dynamical model of the system is constructed and the friction-induced instability of the system in the mixed lubrication regime is investigated and discussed. The operation in the mixed lubrication regime together with the friction-induced instability reveals the need for a closed-loop control system. Employing the obtained dynamical, frictional, and wear models, a controller design method is developed to meet the objectives and satisfy the constraints. The proposed controller design method results in a piecewise affine (PWA) feedback law obtained by solving a set of linear programming (LP) problems offline. The resulting controller is easily implementable in real time. The robust stability of the proposed closed-loop control system is proved considering the uncertainties of the dynamical system. The robust performance of the PWA closed-loop control system in the presence of various disturbances is assessed through simulation and confirmed by experiments conducted on a test rig. The case study here is the engagement process of a synchromesh system in a clutchless automated manual transmission of an electric vehicle.