Hammerstein Model Based RLS Algorithm for Modeling the Intelligent Pneumatic Actuator (IPA) System

Abstract

An Intelligent Pneumatic Actuator (IPA) system is considered highly nonlinear and subject to nonlinearities which make the precise position control of this actuator is difficult to achieve. Thus, it is appropriate to model the system using nonlinear approach because the linear model sometimes not sufficient enough to represent the nonlinearity of the system in the real process. This study presents a new modeling of an IPA system using Hammerstein model based Recursive Least Square (RLS) algorithm. The Hammerstein model is one of the blocks structured nonlinear models often used to model a nonlinear system and it consists of a static nonlinear block followed by a linear block of dynamic element. In this study, the static nonlinear block was represented by a deadzone of the pneumatic valve, while the linear block was represented by a dynamic element of IPA system. A RLS has been employed as the main algorithm in order to estimate the parameters of the Hammerstein model. The validity of the proposed model has been verified by conducting a real-time experiment. All of the criteria as outlined in the system identification's procedures were successfully complied by the proposed Hammerstein model as it managed to provide a stable system, higher best fit, lower loss function and lower final prediction error than a linear model developed before. The performance of the proposed Hammerstein model in controlling the IPA's positioning system is also considered good. Thus, this new developed Hammerstein model is sufficient enough to represents the IPA system utilized in this study.

Metaheuristics algorithms to identify nonlinear Hammerstein model: a decade survey

“…This tuning step is iteratively performed until the last iteration. This section also explains the Hammerstein model that is widely used to identify real nonlinear plants and processes [16], [17], including Thermoelectric cooler [18], [19], amplified piezoelectric tube actuators [20], forecast of wind speed [21], giant magnetostrictive actuators (GMAs) [22], boiler superheated steam pressure [23], boost converter of DC/DC [24], intelligent pneumatic actuator (IPA) [25], hydraulic mini excavator [26], ultrasonic motor [27], proton exchange membrane fuel cell (PEMFC) [28], turntable servo system [29], valve Stiction [30] and electrically stimulated muscle [31]. The Hammerstein model can accurately model actuators to solve control issues and strengthen nonlinearity system identification.…”

“…The experimental verification of such plants and processes is displayed in Table 1. These process plants can be classified into several groups, such as chemical plants, mechanical plants, industrial plants and engineering plants such as amplified piezoelectric tube actuators [20], intelligent pneumatic actuator (IPA) [25], electrically stimulated muscle [31], ultrasonic motor [27], proton exchange membrane fuel cell (PEMFC) [28], turntable servo system [29], hydraulic mini excavator [26], twin rotor system (TRS) and flexible manipulator system (FMS) [72], and valve stiction [30].…”

“…For their identification, the Hammerstein model was applied. The IPA system that applied the Hammerstein model had been based on the RLS algorithm [25] and they use a discrete-time ARX model to represent the linear component of the Hammerstein model. The nonlinear Hammerstein model of the ultrasonic motor was reported in [27].…”