A. Mehmood

Pressure and Friction Observer-Based Backstepping Control for a VGT Pneumatic Actuator

In this paper, we design, analyze, and experimentally validate an observer-based backstepping controller for electropneumatic actuators. These actuators are commonly used in diesel engines for variable geometry turbochargers (VGT) control. They are preferred over other actuation techniques due to better force/weight ratio; however, their drawbacks, such as nonlinear air mass flow, friction, and aerodynamic forces make their control as a challenging problem. The aim of this paper is to achieve precise control of the actuator by compensating friction and aerodynamic VGT forces. A Lyapunov-based output feedback controller is developed using backstepping technique. As the actuator position is the only measured state, pressure and friction states are obtained from sliding mode-based observers. The exponential convergence of the controller-observer closed-loop system is proved using Lyapunov analysis. Experimental results are presented, which demonstrate the effectiveness of the proposed controller.

Nonlinear modeling of Electro-pneumatic actuator for Variable Nozzle Turbocharger control

In this paper, we have developed a detailed mathematical model for a Variable Nozzle Turbocharger (VNT) pneumatic actuator controlled by an Electro-pneumatic Pressure Converter (EPC). This model may require complex calculations for control purpose, therefore it has been simplified in two manners. In the first, the equation of flow dynamics has been replaced by a static equation based on pressure and EPC-position mapping. In the second, the dynamics of the EPC have been neglected and replaced by a static gain. These models have been simulated and compared with experimental data. The complete model as well as the simplified models have shown good accuracy.

Study of the nonlinear control techniques for single acting VGT pneumatic actuator

In this paper, we have developed a detailed mathematical model of a pneumatic actuator for a Variable Geometry Turbocharger (VGT) equipped with an Electro-pneumatic Pressure Converter (EPC). This model may require complex calculations for control purpose; therefore the dynamics of the EPC have been neglected and replaced by a static gain. These models incorporate friction and aerodynamic force related effects by using adaptive LuGre model. To compensate for parametric uncertainties, two single-input single-output nonlinear position control laws are designed using the second order sliding mode (SMC) and backstepping control. A comparative study with experiments shows the effectiveness of the proposed controllers.

Nonlinear Modeling of the VNT Pneumatic Actuator with Aero-dynamic Force

Abstract This paper describes a physical model of an industrial pneumatic actuator used to control variable nozzle turbocharger (VNT). Friction force, that causes hysteresis, is identified using Dahl friction model. Model is tested and compared with experimental results, provided by Honeywell Turbo Technologies (HTT), at different engine conditions. Aerodynamic force acting on the turbocharger is modeled and identified as a function of pressure ratio across turbine and vane angle of the VNT. Comparison between simulation results and experimental results shows the effectiveness of the proposed model.

Control of the Electro-pneumatic VGT Actuator with Friction Compensators

Abstract This paper describes friction compensation based control of an industrial pneumatic actuator used for the variable geometry turbocharger (VGT). Adaptive LuGre model for friction has been used in this work. Friction force that is responsible for hysteresis and hunting phenomenon in the position control is compensated with two different control strategies designed to improve low velocity position tracking. The first approach is related to the knocking the input signal to reduce position error. In the second approach, an adaptive LuGre model based friction observer is proposed for friction compensation. At the end both approaches are compared with the help of experiments on the actuator.

Simulation and design of 3-DOF eye mechanism using Listing’s law

This paper presents the simulation of an eye mechanism by implementing Listingpsilas law. Based on these results an eye model has been designed to produce all movements a human eye can have. Saccadic and smooth pursuit movements can be achieved by pan and tilt mechanism while roll movements are also important for VOR, vergence and optokinetic reflexes. Eye plant model has been created to produce all eye movements. Realization of listingpsilas law is necessary for saccadic and smooth pursuit movements. By simulation we show that position of insertion points on an eye ball and placement of pulleys on a tendon driven robot eye are important to mechanically implement listingpsilas law. Integration of roll movement is only important if saccadic and smooth pursuit movements obey listingpsilas law, without effected by this roll movement. The paper discusses constrains and simulation results of 3D rotational motion based on the conditions for listingpsilas law.

Sliding mode observer based adaptive control of a VGT single acting pneumatic actuator

In this paper, we have considered a novel sliding mode friction observer based control for a servo pneumatic actuator system. The model is obtained to incorporate friction and aerodynamic force related effects, such as hysteresis, using LuGre friction model. A sliding mode observer is proposed to estimate the internal friction state of the LuGre model. In order to compensate for parametric uncertainties and aerodynamic force effects, an adaptive control law for the VGT pneumatic actuator is also designed. The stability of the controller is analyzed with the Lyapunov candidate function. A comparative study with experimental results shows the effectiveness of the proposed controller.

Sensitivity analysis of LuGre friction model for pneumatic actuator control

This paper discusses the analytical model of a pneumatic actuator. Nonlinear hysteresis phenomenon resulting from the friction is also presented in this article. Hysteresis phenomenon governed by the friction in the actuator is modeled with dynamic friction (LuGre) model. Moreover, effects of friction model parameters on the over all model are also discussed. This new approach allows for the sensitivity analysis for the pneumatic actuator.

Position tracking of the VGT single acting pneumatic actuator with 2nd order SMC and backstepping control techniques

Precise control of a variable geometry turbocharger (VGT) is critical to fuel economy, efficiency and emission performance of the engine. This paper describes physical nonlinear modeling and control of a commercial pneumatic actuator used in the VGT system. This model incorporates friction and aerodynamic force related effects, such as hysteresis, using adaptive LuGre model. In order to compensate for parametric uncertainties, two novel nonlinear position control laws are designed for the single-input single-output system using the second order sliding mode (SMC) and backstepping control methods. A comparative study with experimental results shows the effectiveness of the proposed controllers.

Control of air pressure inside an inflatable textile pocket of an active backrest cushion

The objective of this paper is to propose a control strategy of air pressure inside an Inflatable Textile Pocket (ITP) in order to design an adjustable seat backrest for drivers comfort. For the said purpose, firstly a brief model of an Electro-pneumatic Pressure Converter (EPC) is presented along with the pressure dynamics inside an IFP. This nonlinear model is then linearized around an operating point and a control synthesis is performed using the classical linear control theory. The obtained PID controller is implemented on a developed experimental test bench. Furthermore, a comparative analysis, between the feedback reposes obtained with the help of the proposed control and an industrial pressure regulator, is also performed to show the effectiveness of the proposed controller.