Hassan Shraim

Sliding Mode Based Analysis and Identification of Vehicle Dynamics

Vehicles are complex mechanical systems with strong nonlinear characteristics and which can present some uncertainties due to their dynamic parameters such as masses, inertias, suspension springs, tires side slip coefficients, etc. A vehicle is composed of many parts, namely the unsprung mass, the sprung mass, the suspension which makes the link between these two masses and therefore ensures passenger comfort, and also the pneumatic which absorbs the energy coming from the road and ensures contact between the vehicle and the road. In addition to its complexity and the presence of many nonlinearities and uncertainties, the presence of some external perturbations, such as the wind and the road inputs with its own characteristics (radius of curvature, longitudinal and lateral slop, road profile and skid resistance) can cause risks not only to the vehicle but also to passengers and other road users. Many methods have been developed in order to understand the behavior of a vehicle, control it and assist the driver in order to avoid possible lane departures, rollover or jackknifing risks, to ensure a better passenger comfort by means of a suspension control and/or to estimate a safety speed and trajectory. The present book is an attempt to show how the sliding mode based observation, uncertainties identification and parameter estimation may be applied in the control of vehicle dynamics as well as for parameter and perturbations estimation. This book is the first of long series of books in the field of variable structure system in automotive application. Some other results and tools will be proposed and explained in the next publications

Fault diagnosis and fault-tolerant control strategy for rotor failure in an octorotor

This paper presents a fault tolerant approach for a coaxial octorotor regarding rotor failures. A complete architecture including error detection, fault isolation and system recovery is presented. The diagnosis system is designed with a nonlinear observer to generate residuals and an inference model to evaluate them and isolate the faulty motor. Once the motor failure is diagnosed, a recovery algorithm is applied. It uses the built-in hardware redundancy of the octorotor and compensates the loss of the failing motor by controlling its dual to keep a stable flight that allows the multirotor to continue its mission. This architecture is validated on real flights.

Vehicle Parameter Estimation and Stability Enhancement using the Principles of Sliding Mode

In this paper, tires longitudinal forces, vehicle side slip angle and velocity are identified and estimated using sliding modes (SM) observers. Longitudinal forces are estimated using high order SM observers, while for the estimation of the vehicle side slip angle and vehicle velocity, a SM observer based on the hierarchical super twisting algorithm. Validations with the simulator VE-DYNA pointed out the good performance and the robustness of the proposed observers. After validating these observers, controller design for the braking is accomplished using a reduced state space model representing the movement of the vehicle centre of gravity in the (X, Y) plane. Drivers reactions are taken into account. The performance of the closed loop system is carried out by means of simulation tests.

Vehicle parameter estimation and stability enhancement using sliding modes techniques

In this paper, tyres longitudinal forces, vehicle side slip angle and velocity are identified and estimated using sliding modes observers. Longitudinal forces are identified using higher order sliding mode observers. In the estimation of the vehicle side slip angle and vehicle velocity, an observer based on the broken super-twisting algorithm is proposed. Validations with the simulator VE-DYNA pointed out the good performance and the robustness of the proposed observers. After validating these observers, controller design for the braking is accomplished using a reduced state space model representing the movement of the vehicle centre of gravity in the (X, Y) plane. Drivers reactions are taken into account. The performance of the closed loop system is carried out by means of simulation tests.

Sliding mode observers to replace vehicles expensive sensors and to preview driving critical situations

In this paper, tyre longitudinal forces, vehicle side-slip angle and velocity are identified and estimated using a sliding mode observer. For this purpose and in order to insure the observability of the system, the model is decoupled in two parts. In the first part, longitudinal forces are identified using a second order sliding mode observer based on a modified super-twisting algorithm, while in the second part, vehicle velocity and side-slip angle are estimated using a classical sliding mode observer. Validations with the simulator VE-DYNA pointed out the good performance and the robustness of the proposed observers.

Actuator fault diagnosis in an octorotor UAV using sliding modes technique: Theory and experimentation

This paper presents a fault diagnosis strategy for actuators faults in an octorotor unmanned aerial vehicle (UAV) using sliding modes techniques. First, system states are estimated using a second order sliding-mode observer (SOSMO) based on the modified super-twisting algorithm. Second, faults are estimated by considering the system control as an unknown input. After the convergence of the observer, the equivalent output injection is used to estimate the unknown input and thus to identify losses in the actuators. The effectiveness of this approach is illustrated by numerical simulations on Matlab/Simulink, and also a real experimental application on a coaxial octorotor UAV.

Fault tolerant control for multiple successive failures in an octorotor: Architecture and experiments

This paper presents a fault tolerant control strategy based on an offline control mixing for an octorotor unmanned aerial vehicle (UAV) regarding several rotor failures. This strategy consists of a set of explicit laws, computed offline, each one dedicated to a fault situation. The corresponding law is selected according to the output of a fault detection and isolation (FDI) module. This module is designed with a non-linear sliding mode observer. The main advantage of this architecture is the deterministic character of the solution, its fast operation and the low computational load. The effectiveness of this approach is illustrated through real experimental application to a coaxial octorotor, where up to four motor failures are considered.

Vehicle Parameter and States Estimation Via Sliding Mode Observers

Preliminaries and motivations. In the recent years, important research has been undertaken to investigate safe driving conditions in both normal and critical situations. But due to the fact that safe driving requires the driver to react extremely quickly in dangerous situations, which is generally very difficult unless for experts, then this reaction may influence the stability of the system. Consequently, the improvement of the vehicle dynamics by active chassis control is necessary for such catastrophic situations. Increasingly, commercial vehicles are being fitted with micro processor based systems to enhance the safety and to improve driving comfort, increase traffic circulation, and reduce environmental pollution associated with vehicles.

Controllability analysis and motors failures symmetry in a coaxial octorotor

This paper presents a fault tolerant control strategy for a coaxial octorotor regarding one motor failure. A controllability study, based on the construction of the attainable control set method, is presented for a coaxial octorotor with one or more failing motors. The fault is diagnosed using a non linear Super-Twisting sliding mode observer. The octorotor is recovered after a motor failure by controlling its dual motor. The effectiveness of this approach is illustrated by numerical simulations on an octorotor simulator.

Coordinated control strategies for active steering, differential braking and active suspension for vehicle stability, handling and safety improvement

ABSTRACT In this paper, a coordinated control strategy is proposed to provide an effective improvement in handling stability of the vehicle, safety, and comfortable ride for passengers. This control strategy is based on the coordination among active steering, differential braking, and active suspension systems. Two families of controllers are used for this purpose, which are the high order sliding mode and the backstepping controllers. The control strategy was tested on a full nonlinear vehicle model in the environment of MATLAB/Simulink. Rollover avoidance and yaw stability control constraints have been considered. The control system mainly focuses on yaw stability control. When rollover risk is detected, the proposed strategy controls the roll dynamics to decrease rollover propensity. Simulation results for two different critical driving scenarios, the first one is a double lane change and the other one is a J-turn manoeuvre, show the effectiveness of the coordination strategy in stabilising the vehicle, enhancing handling and reducing rollover propensity.