In this article, a practical terminal sliding mode control (TSMC) framework based on an adaptive disturbance observer (ADO) is presented for the active suspension systems. The proposed controller requires no exact feedback linearization about the suspension dynamics. The ADO is designed to estimate the unknown dynamics and control errors produced by the motor actuator. To guarantee the fast convergence and high control accuracy, a TSMC-type surface and a continuous sliding mode reaching law are designed. The finite-time convergence of the controlled system is guaranteed based on the Lyapunov stability theory. To evaluate the performance improvement of the proposed control framework, a detailed comparison with the active disturbance rejection method has been provided. Finally, a practical hardware-in-loop experiment is implemented to validate the effectiveness of the proposed control scheme.

Practical Terminal Sliding Mode Control of Nonlinear Uncertain Active Suspension Systems With Adaptive Disturbance Observer

Long rides on irregular roads and infrastructure problems like uncomfortable seating have a very bad impact on human body. The passengers suffer not only physical pain but also stress related problems. Airsprings gain more popularity in passenger vehicles with an increase in demand for ride comfort. Ride comfort and vehicle handling, being the two critical factors of a suspension system often contradict each other. This led to an extensive research on active automobile suspension systems. The authors of this article propose an innovative design of adaptive air suspension system with LQR control strategy. The proposed LQR controller is tuned by Particle Swarm Optimization. A dynamic model of an air suspension system used in passenger vehicles was designed and simulated for both passive and adaptive systems in MATLAB. An experimental evaluation was done to check the performance of the adaptive air suspension system on a vibration shaker table. Air suspension is a non-linear system and thus the authors have derived a stiffness equation for the same with minimal assumptions. A comparative analysis between the most commonly used PID controller and proposed LQR controller was performed over bumps, potholes and ISO standard random roads in MATLAB. Simulation results showed that adaptive air suspension system improves the ride comfort by reducing the maximum displacement amplitude of the vehicle over random roads by 31% while ensuring the stability of the vehicle by reducing the settling time by 85%. The experimental results of an adaptive air suspension system subjected to random vibrations of frequencies between 5 Hz to 20 Hz, exhibited a reduction of sprung mass acceleration by about 30% demonstrating that the proposed controller is effective for random vibration inputs.

A contemporary adaptive air suspension using LQR control for passenger vehicles.

Ride Comfort-Road Holding Trade-off Improvement of Full Vehicle Active Suspension System by Interval Type-2 Fuzzy Control

Adaptive sliding mode control based nonlinear disturbance observer for active suspension with pneumatic spring

This work proposes an optimal fuzzy adaptive robust proportional-integral-derivative (PID) controller for a quarter-car model with an active suspension system. To this end, at first, the errors of ...

Optimal fuzzy adaptive robust PID control for an active suspension system

Linear disturbance observer based sliding mode control for active suspension systems with non-ideal actuator

The application of extremum seeking control (ESC) algorithm to antilock braking systems (ABSs) is attractive for maximizing the longitudinal frictional force. Most currently reported results suffer from the drawback of steady state oscillations around the extremum or the need to have the gradient information. In this paper, a new ESC algorithm is proposed for application to ABSs to overcome these two drawbacks. The proposed algorithm is based on a novel dynamic nonlinear gradient observer (DNGO) and a longitudinal frictional force estimator. The performance and the ultimate boundedness of the proposed ESC, DNGO and the force estimator are analysed. The proposed method is validated by simulation for dry and wet road surfaces and compared with two established results. The method is further validated on an experimental setup in the laboratory for dry and oily surfaces.

Dynamic Nonlinear Gradient Observer based Extremum Seeking Control for Optimum Braking

This article analyzes a recent result on tracking control of nonlinear, mismatched interconnected systems and points out its drawback with regard to noise amplification that originates from numerical differentiation of tracking error. One of the objectives of the article is to propose two remedial measures and show their improvements by analysis for performance and stability. In the first remedy, the derivative of the tracking error is obtained without recourse to numerical differentiation while the second remedy offers a solution that does not need the derivative of the tracking error. Another objective of the article is to propose an extension to decentralized sliding mode control of interconnected systems. Unlike other published results, the extension can assure local sliding in each subsystem. The proposed remedies are validated by numerical simulation, and experimentation on a laboratory coupled tank system. A discussion with a generalized extended state observer based method and comparative simulations with other well-known methods are carried out.

Disturbance Observer Based Controller Under Noisy Measurement for Tracking of nDOF Uncertain Mismatched Nonlinear Interconnected Systems

This article is motivated by an interesting recent result on antilock braking system (ABS) design using two-time scale (TTS)-based estimation. In this article, the basic method of TTS is extended to estimate not only the disturbances but also their derivatives, improving the accuracy of estimation by an order of magnitude. Further, the problem of ABS is extended to an eight-DOF vehicle model to include the effects of load transfer, steering dynamics, and actuator dynamics. Since analysis showed that the use of basic TTS to ABS design results in a poor transient in the estimation error dynamics, this article proposes a new formulation of the TTS method specifically for ABS. Two new ABS-specific sliding surfaces are proposed to compensate the actuator dynamics where the second sliding surface is proposed as an improvement over the first one. The stability, and convergence of estimation, and tracking errors are analyzed. The proposed methods are validated on MATLAB/Simulink, and CarSim platforms for a D-class sedan car. The results are also validated on an experimental ABS platform in the laboratory.

Extended Nonlinear Two-Time Scale Estimation Approach for Antilock Braking Systems

In this paper, performance limitations of the conventional front wheel steering (FWS) system is analyzed in order to design the controller that can improve the vehicle handling and stability. By adding steering input at the rear wheels, four wheel steering model under the influence of external crosswind disturbance acting on the vehicle is obtained. The disturbance observer (DO) based model following sliding mode controller is designed for modified steering model to achieve ideal vehicle handling. A simulation is carried out to prove the effectiveness of the proposed controller in tracking the dynamics of the system to the desired reference model. Robustness of the proposed controller is also verified against external disturbances and in tracking different steering inputs.

Sushant Chaudhari

Papers

Linear disturbance observer based sliding mode control for active suspension systems with non-ideal actuator

Dynamic Nonlinear Gradient Observer based Extremum Seeking Control for Optimum Braking

Disturbance Observer Based Controller Under Noisy Measurement for Tracking of nDOF Uncertain Mismatched Nonlinear Interconnected Systems

Extended Nonlinear Two-Time Scale Estimation Approach for Antilock Braking Systems

Disturbance observer based model following controller for four wheel steering vehicles