Abstract
The active suspension system of a vehicle manipulated using electro-hydraulic actuators is a challenging nonlinear control problem. In this research work, a novel Linear Parameter Varying (LPV) State-Space (SS) model with a fictional input is proposed to represent a nonlinear half-car active suspension system. Four different scheduling parameters are used to embed the nonlinearities of both the suspension and the electro hydraulic actuators to represent its nonlinear behavior. A recursive least squares (RLS) algorithm is used to predict the future behavior of the scheduling parameters along the prediction horizon. A Model Predictive Control-Linear Quadratic Regulator (MPC-LQR) is implemented as the control strategy and, to ensure stability, Quadratic Stability conditions are imposed as Linear Matrix Inequalities (LMI) constraints. Furthermore, the inclusion of attraction sets to overcome the conservative performance imposed by the Quadratic Stability conditions is included, as well as a terminal set were the switching between the MPC and the LQR controller is made. Simulations results for the half-car active suspension model over a typical road disturbance are tested to show the effectiveness of the proposed MPC-LQR-LPV controller with quadratic stability conditions in terms of comfort and road-holding.
Highlights
Published: 15 February 2022Security and comfort are two of the most relevant aspects when designing a car.Vehicles should be able to attenuate road disturbances to ensure comfort for the passengers while maintaining road-handling adequate in order to allow proper driving conditions.Previously, suspensions have been designed by using passive elements such as springs and dampers, selected depending on vehicle mass and geometry
Instead of the MPC law, an Linear Parameter Varying (LPV)-LQR gain can be computed based on the actual values of the scheduling parameter in order to cope with the small deviation of the states around the origin without the conservatism of the MPC algorithm with quadratic stability conditions and reducing the execution time of the optimization problem
To prove the efficiency of the proposed Model Predictive Control-Linear Quadratic Regulator (MPC-LQR)-LPV control strategy described in Section 7 the following simulation of the half-car active suspension system against a typical road disturbance is presented
Summary
Security and comfort are two of the most relevant aspects when designing a car. Vehicles should be able to attenuate road disturbances to ensure comfort for the passengers while maintaining road-handling adequate in order to allow proper driving conditions. These conditions are not always possible and as the angle increases, the model differs more from reality In this approach, a novel LPV state-space model representation of a half-car model using four different scheduling parameters and a fictional input will be used to embed the nonlinearities of the two hydraulic actuators and the trigonometric relations of the pitch angle while preserving the nonlinear behavior of the system. Attraction sets and terminal sets are included in the approach in order to switch the MPC controller to an LQR controller near the equilibrium point This allows the proposed control strategy to solve a nonlinear control problem by LPV techniques while ensuring stability conditions and optimal performance.
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