Analysis and control of chaos for lateral dynamics of electric vehicles

In this paper, the nonlinear dynamic model of the lateral system for electric vehicles (EVs) is proposed. Different from the traditional steering system, a driver’s reaction model is introduced and meanwhile the disturbance caused by irregularities of road surface is also considered in this paper. Based on the integrated nonlinear dynamic equations, it shows that the stability of lateral system of EVs is closely related to the heading speed of the vehicle. The lateral system has a Hopf bifurcation when the vehicle heading speed equals a critical value, and then enters into chaos domain along with the increment of the vehicle heading speed. The unstable behaviors may make EVs spin and even turn over, which are quite harmful to the safety of EVs. As for this issue, a control method is proposed and implemented to protect the vehicle from spinning and thus improve the safety of EVs. The computer simulation is utilized in this paper to analyze nonlinear dynamics, as well as to validate the existence of chaotic motions and the feasibility of the control scheme. From the simulation results, it shows that the chaotic motions existing in the EV lateral dynamics can be suppressed by the proposed control method, and thus the corresponding cornering performance and safety are improved.published_or_final_versio

Analysis and stabilization of chaos in electric-vehicle steering system

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Trends in vehicle motion control for automated driving on public roads

In this paper, we describe how vehicle systems and the vehicle motion control are affected by automated driving on public roads. We describe the redundancy needed for a road vehicle to meet certain safety goals. The concept of system safety as well as system solutions to fault tolerant actuation of steering and braking and the associated fault tolerant power supply is described. Notably restriction of the operational domain in case of reduced capability of the driving automation system is discussed. Further we consider path tracking, state estimation of vehicle motion control required for automated driving as well as an example of a minimum risk manoeuver and redundant steering by means of differential braking. The steering by differential braking could offer heterogeneous or dissimilar redundancy that complements the redundancy of described fault tolerant steering systems for driving automation equipped vehicles. Finally, the important topic of verification of driving automation systems is addressed

Nonlinear optimal control for aircraft ground manoeuvres

Despite recent advances in flight control systems, aircraft ground manoeuvres are still conducted manually. This thesis aims to improve the efficiency and safety of airport operations by developing a real-time optimal controller forground operations, especially high-speed runway turnoff. A reliable and robust controller is able to improve airport traffic capacity and reduce runway events of incursion, excursion, and confusion. A high-fidelity fully-parameterised aircraft model is developed to capture aircraft ground dynamics. The nonlinearities enter the system via sub-models of tyres and aerodynamics. A numerical continuation method is used to compute and track steady-state solutions under the variation of parameters, providing a global picture of the system stability within a typical operation envelop. Dynamic simulations are carried out to analyse transient behaviourswhich are not captured by the bifurcation analysis. Three controllers are employed to investigate the automation of aircraft runway exit manoeuvres. An Expert Pilot Model is developed to represent manoeuvres that are manually operated by pilots. To evaluate the optimality of the proposed Expert Pilot Model (EPM), Generalised Optimal Control (GOC) is employed to numerically investigate the optimal solutions for aircraft runway exit manoeuvres. A formal solution of real-time optimal steering control problem is desired in light of the gap between the Expert Pilot Modeland Generalised Optimal Control. Therefore, Predictive Steering Control is developed based on Linear Quadratic method with lookahead, which is able to deliver near-optimal manoeuvres.</div

On Steady-State Cornering Equilibria for Wheeled Vehicles with Drift

In this work we derive steady-state cornering conditions for a single-track vehicle model without restricting the operation of the tires to their linear region (i.e. allowing the vehicle to drift). For each steady-state equilibrium we calculate the corresponding tire friction forces at the front and rear tires, as well as the required front steering angle and front and rear wheel longitudinal slip, to maintain constant velocity, turning rate and vehicle sideslip angle. We design a linear controller that stabilizes the vehicle dynamics with respect to the steady-state cornering equilibria using longitudinal slip at the front and the rear wheels as the control inputs. The wheel torques necessary to maintain the given equilibria are calculated and a sliding-mode controller is proposed to stabilize the vehicle using only front and rear wheel torques as control inputs

Analysis of Vehicle Steering and Driving Bifurcation Characteristics

The typical method of vehicle steering bifurcation analysis is based on the nonlinear autonomous vehicle model deriving from the classic two degrees of freedom (2DOF) linear vehicle model. This method usually neglects the driving effect on steering bifurcation characteristics. However, in the steering and driving combined conditions, the tyre under different driving conditions can provide different lateral force. The steering bifurcation mechanism without the driving effect is not able to fully reveal the vehicle steering and driving bifurcation characteristics. Aiming at the aforementioned problem, this paper analyzed the vehicle steering and driving bifurcation characteristics with the consideration of driving effect. Based on the 5DOF vehicle system dynamics model with the consideration of driving effect, the 7DOF autonomous system model was established. The vehicle steering and driving bifurcation dynamic characteristics were analyzed with different driving mode and driving torque. Taking the front-wheel-drive system as an example, the dynamic evolution process of steering and driving bifurcation was analyzed by phase space, system state variables, power spectral density, and Lyapunov index. The numerical recognition results of chaos were also provided. The research results show that the driving mode and driving torque have the obvious effect on steering and driving bifurcation characteristics