Steering Input Research Articles

Handling Capabilities of Vehicles in Emergencies Using Coordinated AFS and ARMC Systems

In this paper, an advanced control technique that can be implemented in hard emergency situations of vehicles is introduced. This technique suggests integration between Active Front Steering (AFS) and Active Roll Moment Control (ARMC) systems in order to enhance the vehicle controllability. For this purpose, the AFS system applies a robust sliding mode controller (SMC) that is designed to influence the steering input of the driver by adding a correction steering angle for maintaining the vehicle yaw rate under control all the time. The AFS system is then called active-correction steering control. The ARMC system is designed to differentiate the front and rear axles' vertical suspension forces in order to alter the vehicle yaw rate and to eliminate the vehicle roll motion as well. Moreover, the operation of the SMC is based on tracking the behavior of a nonlinear 2-wheel model of 2-DOF used as a reference model. The 2-wheel model incorporates real tire characteristics, which can be inferred by the use of trained neural networks. The results clearly demonstrate the enhanced characteristics of the proposed control technique. The SMC with the assistance of the ARMC provides less correction of the steering angle and accordingly reduces the possibility of occurrence of the saturation phenomenon that is likely to take place in the operation of the SMC systems.

Influences of Braking System Faults on the Vehicle Dynamics

From a safety point of view the braking system is, besides the driver, one of the key subsystems in a car. The driver, as an adaptive control system, might not notice small faults in the hydraulic part of the braking system and sooner or later critical braking situations, e.g. due to a brake-circuit failure, may occur. Most of the drivers are not capable to deal with such critical situations. Therefore this paper investigates the influence of faults in the braking system on the dynamic vehicle behavior and the steering inputs of the driver to keep the vehicle on the desired course.

Effects of Tank Shape on the Roll Dynamic Response of a Partly Filled Tank Vehicle

The directional response and roll stability characteristics of a partly filled tractor-semitrailer vehicle, equipped with various cross-section tanks, are investigated as functions of fill volume and steer inputs. The tank-vehicle combination is analytically modeled upon integrating a quasi-static roll plane model of a partly filled tank of generic cross-section with a three-dimensional directional dynamic model of a five-axle tractor-semitrailer vehicle, assuming constant forward speed. The vehicle model is analyzed for different cross-sections of partly filled tanks, including circular, modified-oval and two optimal cross-sections. The directional response characteristics of the vehicle are evaluated to study the influence of partial-fill condition, steering maneuver, and vehicle speed on the roll dynamic performance of the tank cross-section and the vehicle. A comparison of the response characteristics, in terms of variations in cargo c.g. shift and roll mass moment of inertia, roll angle, lateral acceleration and yaw rate of the trailer sprung mass, revealed that the optimal tank geometry yields considerably less variations in the cargo c.g. coordinates and can thus significantly enhance the directional response and roll stability characteristics of partly-filled tank vehicles.

Using µ Feedforward for Vehicle Stability Enhancement

A differential braking control strategy using yaw rate feedback, coupled with µ feedforward is introduced for a vehicle cornering on different µ roads. A nonlinear 4-wheel car model is developed. A desired yaw rate is calculated from the reference model based on the driver steering input. It is shown that knowledge of µ offers significant improvement of the vehicle desired trajectory over that of a yaw rate controller alone. Uncertainties and time delay in estimating µ are shown to still yield a system that is superior to using no µ information at all.

Some properties of the general n-trailer

If some of the trailers of the so-called n-trailer system are connected via a kingpin hitch, the kinematic model of the system is more complicated that in the standard case. However, something can still be said about the structural properties of the system, like controllability. The more complicated equations can be interpreted in terms of virtual steering wheels placed on the off-axle joints with steering angle which is a non-linear feedback from the original configuration state. Quite remarkably, the extra singularities of the system have an explanation in terms of these virtual steering wheels. This is also sufficient to assert that the general n-trailer problem can be embedded into the corresponding multisteering n-trailer system. The multi-chained form available for this last system can be recovered also for the general n-trailer if we replace the extra steering inputs with the aforementioned feedback loops.

MODELING AND VERIFICATION OF SUPERSTEER STEERING SYSTEM

A steering model that used fourbar linkage mechanisms to describe its geometry and accounted for the spatialorientation of the kingpin was developed. A narrow orchard tractor equipped with a commercial SuperSteer steering systemwas operated in a Yolo loam soil and on an asphalt surface at the University of California, Davis, to obtain turning radii.Steering tests were conducted at two input steering angles, two forward speeds, and two drawbar load levels on two distinctsurfaces. Results showed welldefined turning radii on an asphalt surface and understeering in a tilled soil. Turning radiiwere obtained by solving a nonlinear system of equations based on Fromms drifting tire equations, camber trust equations,and parameters obtained from geometric equations. The model was evaluated using existing data. The predicted radii werein reasonable agreement with the experimental results in both the tilled soil and on the asphalt surface.

DYNAMIC ANALYSES AND ROBUST STEERING CONTROLLER DESIGN FOR AUTOMATED LANE GUIDANCE OF HEAVY‐DUTY VEHICLES

ABSTRACTIn this paper, we present various linear analyses of the linearized lateral dynamics of heavy‐duty vehicles (HDVs) (tractor‐semitrailer type), which include time domain, frequency domain and pole/zero analyses. These analyses are conducted to examine the vehicle response to the steering input subjected to variations of speed, road adhesion coefficient, cargo load in the trailer, and look‐ahead distance for the lateral deviation sensor. These parameters (uncertainties) have significant influence on vehicle dynamics. It has been shown that redefining the look‐ahead lateral error as the controlled output has a favorable impact on the lateral control problem. Based on these analyses, a robust steering controller using H∞ loop‐shaping procedure is designed for a tractor semitrailer combination to follow the road center line on both curved and straight highway sections. The proposed controller ensures the robust performance under model uncertainties which include varying vehicle longitudinal speed, road adhesion coefficient, and cargo load in the trailer. The performance of the designed controller is evaluated by simulations and validated by experiments.

Synthesis and analysis of the two loop translational input steering mechanism

A kinematic model of a rack-and-pinion type steering linkage is developed, on the basis of which the synthesis of the mechanism is performed using the criteria of correct turning of the wheels and good transmissibility of the motion. The kinematic analysis of the mechanism is also carried out and output diagrams are presented for the case of a four-wheel-drive light tractor.

Multivariable Bilinear Vehicle Control Using Steering and Individual Wheel Torques

The focus of this paper is the stabilization of vehicle motion to a prescribed path while integrating an increased subset of vehicle inputs than was previously attempted. The integration of the steering inputs and the wheel torque inputs is achieved within the context of bilinear feedback control. The bilinear terms in the model formulation are used to describe the effect of wheel steer angles on the effective moment arm associated with brake or drive torques applied at the relevant wheels. The wheel torques may assume both positive or negative values. A nonlinear state feedback controller which attempts to minimize a quadratic performance index is developed and simulations are used to evaluate the performance of the vehicle in an AHS lane tracking scenario. The simulations are performed on a previously developed nonlinear vehicle model.

Controllability and singularities in the n-trailer system with kingpin hitching

When one or more trailers of the so-called n-trailer mobile robot present kingpin hitching i.e. they are not hooked directly on the midpoint of the axle of the preceding trailer, the system has a more complicated dynamics than in the standard case. These off-axle hitches can be substituted by a passive steering wheel with the steering input calculated via nonlinear feedback from the configuration state. The new singularities associated with this general n-trailer system can be physically interpreted in terms of the virtual steering wheels. Furthermore, in the regular points controllability can be deducted from the existing results for the standard n-trailer system.

Analysis of Driver's Steering and Speed Control Strategies in Curve Negotiation

SUMMARYThe paper discusses some of the common speed and steering control strategies of drivers for negotiating curved roads under normal, obstacle-free driving conditions. An analysis is given of the dynamic behaviour of the driver-vehicle system for two typical strategies. A driver model is developed to take into account the application of steering and speed control before approaching a curve and during driving on curved roads. The driver's anticipatory speed-control is based on the desired lateral acceleration and estimated maximum curvature of the road ahead. The well-known two-level model is adapted for describing the steering activity of the driver. The primary control of steering is anticipatory tracking of the road-curvature previewed at a look-ahead distance. It is assumed that the driver's mental model for anticipatory steering is based on a simple, linear and non-adaptive vehicle model assuming a vehicle driving with constant forward speed. A non-linear model with variable forward speed represents the actual vehicle. When both steering input and speed control using brake/throttle are applied simultaneously the driver's anticipatory steering estimate leads to tracking errors. The driver's compensatory steering input for reducing tracking errors uses feedback of error in lateral displacement at a near-field viewpoint of the driver. The results of analysis of the driver-vehicle system demonstrate the significant influence of the driver's internal model and control strategies on the overall performance of the driver-vehicle system.

On The Dynamics of Actively Steered Railway Vehicles

Two active steering systems and an active guidance system for a vehicle with two wheel-pairs are described and analysed. A wheel-pair has independently rotating wheels pin-jointed to a carrying frame. The wheels are mounted on stub-axles and have hub-mounted traction motors. Differential torques are applied to the wheels to generate a steering input. The equations defining the systems are presented The two active steering systems use either the body yaw velocity and train speed or knowledge of the route data and position to steer the wheels to be radial on a curve. The active guidance system uses a lateral displacement transducer to measure the lateral position of the wheels in the track to generate an error signal. All the controllers perform well on the steady curve. On the “virtual” transition into the curve, the active guidance controller performs much better than the steering controllers, benefitting from preview of the track.

Experimental study on autonomous mobile robot acquiring optimal action to avoid moving obstacles

The principal aim of this study was to show how an autonomous mobile robot can acquire the optimal action to avoid moving multiobstacles through interaction with the real world. In this paper, we propose a new architecture using hierarchical fuzzy rules, a fuzzy evaluation system, and learning automata. By using our proposed method, the robot autonomously acquires finely tuned behavior which allows it to move to its goal and avoid moving obstacles by using the steering and velocity control inputs simultaneously. We also show experimental results which confirm the feasibility of our method.

Numerical Simulation of Vehicle Behavior during Straight Line Keeping on Undulating Road Surfaces

SUMMARY Numerical design of vehicles having optimal straight line stability on undulating road surfaces requires an accurate vehicle model based on knowledge of the relevant phenomena. Therefore, vehicle behavior on undulating straight roads has been analyzed and modeled. Measurements on a flat road surface have shown that the dedicated vehicle model yields accurate simulation results of the steering response to medium steering wheel angle inputs. In addition, the model has been validated by measuring two vehicle responses during normal driving on an undulating straight road: viz. the responses to the small steering wheel angle input and to the input by the global inclination of the road surface.

多段階学習による障害物回避のための行動獲得

Multistage learning applied to obstacles avoidance is studied in this paper. We propose a new learning system which consists of the hierarchical fuzzy rules, fuzzy evaluation system and 2-stage learning automata. Then we show how an autonomous mobile robot can acquire the optimal action and fine attentive behavior using multistage learning through the interaction with the real world. In other words, the robot acquires how to pay attention to moving obstacles and how to avoid them using the steering and velocity control inputs, simultaneously. We also show the experimental results to confirm the feasibility of our method.

The sensitivity analysis of yaw rate for a front wheel steering vehicle: In the frequency domain

In this paper, the sensitivity analysis of yaw rate for a front wheel steering vehicle is performed in the frequency domain. A two degree of freedom system is used to represent a simple vehicle model in order to derive the system transfer function. The transfer function is defined between a steering angle input and a yaw rate output. This model shows the simplest lateral dynamic effect and is useful for understanding of the dynamic characteristics and control aspect of the target system. Vehicle mass, inertia, cornering stiffiness, and wheel base are selected as design variables. Sensitivity functions of the transfer function with repect to design variables are derived, and the results show that the response of the yaw rate always has stable minimum phase characteristics. The objective of this paper is the proposition of a base for re-design and new-design of the vehicle by checking the yaw rate variations with respect to the design variable change in the frequency domain. Finally, dominant design variables can be selected based on the sensitivity analysis.

階層ファジィルールと学習オートマトンを用いた自律移動ロボットの障害物回避動作計画

We show how an autonomous mobile robot can acquire the optimal action through the interaction with the real world. We propose a new architecture using the hierarchical fuzzy rules, fuzzy evaluation system and learning automaton. By using our proposed method, the robot acquires how to approach the goal avoiding a moving obstacle, using the steering and velocity control inputs, simultaneously. We also show the experimental results to confirm the feasibility of our method.

Optimal Roll Control of a Single-Unit Lorry

Lateral acceleration control and linear quadratic regulator (LQR) theory are used to design active roll control systems for heavy goods vehicles. The suspension consists of a limited bandwidth hydraulic actuator in series with an anti-roll bar. The procedure used to determine suitable controller gains is described. The simulation results show that roll control of a single-unit lorry requires an actuator bandwidth of 6 Hz and mean power of approximately 17 kW for a ‘worst case’ random steering input. The static roll-over threshold of this vehicle is increased by 66 per cent when compared with the same vehicle with passive suspensions and the r.m.s. lateral load transfer is reduced by 34 per cent for a typical random steering input.

Influence of Tire Characteristic Properties on the Vehicle Lateral Transient Response

Abstract This paper summarizes results from a recent program of tire-vehicle system research, using simulation techniques to identify the influence of tire characteristics on the vehicle response functions of yaw rate and lateral acceleration. Tire characteristics such as cornering stiffness, cornering stiffness-wheel load dependency, self-aligning torque, and dynamic tire behavior were varied with respect to a control tire. Computer simulations of vehicles undergoing a steering wheel pulse input were carried out using ADAMS full vehicle models and the Magic Formula tire model. Frequency responses were obtained from these vehicle handling simulations. The Four Parameter Evaluation Method of Lateral Transient Response was used to judge the vehicle handling performance. The influences of tire characteristic properties on the vehicle lateral transient response are explained by this method.

Overturning Stability of Three Wheeled Motorized Vehicles

SUMMARY Three wheeled motorized vehicles are a major mode of public transport in many countries. These vehicles are prone to overturning even during normal turning and obstacle avoidance maneuvers. This paper presents a parametric analysis of a mathematical model of the vehicle and evolves guidelines for improving the overturning stability in terms of vehicle geometry and suspension properties. Differential equations governing the dynamic behavior of the vehicle are derived on the basis of a six degree of freedom model. The vehicle response to variations in steering, engine power and braking inputs is then numerically simulated. The effects of vehicle geometry and elasto-damping suspension coefficients on the vehicle stability are presented. The results indicate an optimum position of the center of gravity where the vehicle is most stable. While stiffer suspensions favour stability, there exists an optimum value of suspension damping for which the minimum wheel load is a maximum.