Nonlinear nominal modelling of proportional valves with unknown spool displacements

The paper discusses a new nonlinear nominal modelling for a proportional valve for which the spool displacement is unknown. First, we introduce a nonlinear nominal model of the hydraulic cylinder dynamics. Next, we propose a new nonlinear nominal modelling consisting of two procedures. In the first procedure, by applying a previous estimation method using a servo valve, several physical parameters of the valve, such as the damping, are identified. In the second procedure, by applying the previous estimation method using the hydraulic cylinder as a flow rate sensor and also multiplying the spool motion equation by the unknown flow gains, the unknown parameters are identified by the projection theorem. The effectiveness of the proposed method is confirmed by an experimental proportional valve, which is an electronic control modulation valve (ECMV). The identified nominal model outputs and the experimental outputs are sufficiently similar.