Steering Input Research Articles

Performance Enhancement of Road Vehicles Using Active Independent Front Steering (AIFS)

Technological developments in road vehicles over the last two decades have received considerable attention towards pushing the safe performance limits to their ultimate levels. Towards this goal, Active Front Steering (AFS) and Direct Yaw-moment Control (DYC) systems have been widely investigated. AFS systems introduce corrective steering angles to conventional system in order to realize target handling response for a given speed and steering input. It is thus expected that such an action under severe maneuvers may cause one tire to reach saturation while the other tire may be capable of developing more force. This study, therefore, proposes an Active Independent Front Steering (AIFS) system capable of controlling a wheel independently. At low speeds, the proposed AIFS system will modify the steer angle with speeds while maintaining pro-ackerman geometry similar to an AFS system. In doing so, it will realize a target response defined as one provided by a neutral steer system. However, in a severe maneuver, as the inner tire approaches the saturation limit, the AIFS system controller will only increase the angle of the outer tire, effectively introducing an anti-ackerman geometry. The study is carried out using a comprehensive 4-wheel handling model with AIFS capability. A PI controller with ability to detect and control the outer wheel independently is incorporated to examine the handling performances of an understeer vehicle under a ramp-step and sinusoidal steering inputs. In general, the results demonstrate that AIFS can perform as well as AFS in realizing target response while AIFS can provide performance enhancement beyond the limits of AFS. The control approach of AIFS is also shown to be effective for split-μ condition. Language: en

An optimal preview driver model applied to a non-linear vehicle and an impaired driver

This paper proposes an improved driver model based on the one introduced by MacAdam in 1981 where optimal preview control is applied. The details of the optimal preview driver model are derived. The modified model incorporating the steering angle into the performance index is used to compute the steering input. The parameters associated with reaction time and preview time characterize the adaptation of the driver to the changes of the vehicle, the road and the environment. The modified model exhibits better performance and its parameters are well related to the performance of the driver. The driver model is then coupled with a non-linear vehicle. Initial tests are performed to identify the driver’s parameters. The coupling of the driver and the non-linear vehicle introduces enhanced path-following. An impaired driver model can be obtained by reducing the optimal parameters. When the safety criteria are chosen, the threshold for safe driving is identified.

Simultaneous vehicle-handling and path-tracking improvement using adaptive dynamic surface control via a steer-by-wire system

This paper deals with the simultaneous vehicle-handling and path-tracking improvement through a steer-by-wire system, using non-linear adaptive dynamic surface sliding control. The designed adaptive dynamic surface controller, which is insensitive to system uncertainties, offers an adaptive sliding gain to eliminate the precise determination of the bound of uncertainties. The sliding-gain value is obtained using a simple adaptation law that does not require an extensive computational load. Achieving the improved vehicle-handling and path-tracking characteristics requires both accurate state estimation and well-controlled steering inputs from the steer-by-wire system. A second-order sliding-mode observer provides accurate estimation of the lateral and longitudinal velocities while the yaw rate is available from the angular rate sensor. A driver control model is also presented according to the preview or look-ahead strategy to generate appropriate steering angles using the vehicle state feedback and future information about the path to be followed. Moreover, because of the inertia and viscous damping of the steering mechanism, and the effects of the Coulomb friction and self-aligning moment of the front tyres, the steering-system controller is designed based on the proposed adaptive dynamic surface scheme, to control the front steering angle. A complete stability analysis based on the Lyapunov theory is presented to guarantee closed-loop stability. The simulation results confirmed that the proposed adaptive robust controller not only improves the vehicle-handling and path-tracking performance but also reduces the chattering problem in the presence of uncertainties in the tyres’ cornering stiffnesses.

Fuzzy Control Strategy Applied to Adjustment of Front Steering Angle of a 4WSD Agricultural Mobile Robot

This paper presents the preliminary studies of the control strategy based in fuzzy logic, projected for the steering system of AGRIBOT project that consist of a wheeled autonomous mobile robotic in real scale endowed with four independent steering and driven wheels (4WSD). In this work we present a preliminary fuzzy controller design applied to front steering angle, using a multivariable plant which incorporates simplified linear model of lateral dynamics of a vehicle whose input are linear combination of rear and front steering angles. The fuzzy control strategy was decided because provides flexible way to deploy with embedded systems. Simulations are used to illustrate the designed controller performance. We use Ackerman geometry to trace front steering angle that allows the vehicle to perform correctly a given maneuver preserving a minimum level of stability and maneuverability. The goal is to establish a relationship between steering input commands and the control commands to the actuators so that it is possible to adjust the attitude of the actuators over the movement axis, as the trajectory change.

Dependencies of driver steering control parameters

Path tracking driver models assume the observed path deviation ahead of the vehicle to be proportionally transferred to a corrective steering input. The most simple version of such a model includes three parameters, a single preview distance, a steering gain and a delay time, being examined in this paper, in dependency of vehicle properties, driver characteristics, velocity and path. It is shown that, for different and bounded preview lengths, a driver can follow any path with almost the same minimum path error, if the gain is adapted appropriately. The upper boundary is path-dependent but driver and path characteristics have only a minor effect on the resulting relationship between preview length and gain. Consequently, gain and preview length may well vary along some path. This has been examined, experimentally, for different drivers. A too small preview length conflicts with closed-loop stability, explicitly described in terms of vehicle parameters, vehicle speed and driver delay time. The results of this paper provide a basis for enhanced understanding of human driver behaviour.

Modelling, Simulation and Validation of 9 DOF Vehicles Model for Automatic Steering System

Autonomous vehicle have recently arouse great interest and attention in the academic worldwide because of their great potential. As the new features for driver assistance and active safety systems are growing rapidly in vehicles, the simulation within a virtual environment has become a necessity. A vehicle model is required to represent the vehicle behaviour as close as real vehicle in simulation software. This paper presents 9 DOF vehicle models which consist of handling and Calspan tire model develop in Matlab Simulink environment to study the vehicle behaviour for double lane change (DLC) and step steer input test. Those criteria will be compared with validated vehicle software namely CarsimEd to evaluated the performance of the vehicle model involving lateral acceleration, yaw angle and yaw rate from both output. Results show the 9 DOF vehicle closely follows the CarsimEd trends with acceptable error at both conditions.

능동전륜조향장치를 채택한 사륜조향차량의 횡방향 안정성 강화에 대한 연구

This study is to propose and develop an integrated dynamics control system to improve and enhance the lateral stability and handling performance. To achieve this target, we integrate an AFS and a 4WS systems with a fuzzy logic controller. The IDCS determines active additional steering angle of front wheel and controls the steering angle of rear wheel. The results show that the IDCS improves the lateral stability and controllability on dry asphalt and snow paved road when double lane change and step steering inputs are applied. Yaw rate of the IDCS vehicle tracks reference yaw rate very well and body slip angle is reduced about by 50%. Response time of the IDCS vehicle is also decreased.

A Robust Steering Assistance System for Road Departure Avoidance

A driver-assistance system (DAS) that combines an automatic road departure avoidance (RDA) system with the driver's steering input is presented. The system is based on a closed-loop driver decision estimator (DDE), which establishes the risk of road departure. If a road departure is likely to occur, the RDA system intervenes by correcting the steering angle. Robustness is guaranteed by an <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">inf</sub> controller designed to take into consideration the main uncertainties affecting the dynamics. Driver-in-the-loop tests evaluate the performance of the system in terms of robustness, risk of road departure, and driving experience. Experiments show that the system is effective in reducing the risk of road departure without impeding maneuverability.

Field tests and validation of dynamical models of tank vehicles Part II: experimental tests and results

This paper focuses on the description of standard and repeatable tests performed at the Nardo Technical Center (NTC) in Nardo (Lecce – Italy) to investigate the side dynamics of an articulated vehicle carrying liquid. Comparisons between three different kinds of mechanical models and test results are presented. Results show that the dynamical interaction between liquid and rigid cargo is considerably influenced by the type of manoeuvre performed and the sharpness of the steering inputs applied.

Reference trajectory generation for control in single-unit heavy vehicle: focus on rollover prevention

The problem of reference trajectory generation for single unit heavy vehicle motion is investigated. The Reference Governor is integrated in the control structure with control allocation. This nonlinear block filters the driver steering inputs in order to modify the reference trajectories in such a manner that if followed by the vehicle the wheels keep contact with the road. The simulation results for a vehicle represented by an 8 DOF nonlinear model and controlled by front active steering and braking systems are performed for fishhook manoeuvre. They demonstrate the effectiveness of the proposed scheme.

Steering Wheel Angle Pulse Input Simulation and Evaluation of a Car Based on ADAMS

Vehicle’s steering wheel angle pulse input performance was an representative test of handling and stability, it characterizes vehicle’s handling and stability by the transient response of the steering wheel angle pulse input. Taking a car for example, in the ADAMS software, vehicle dynamics model was established. According to GB/T6323.3—94 standards, the steering wheel angle pulse input virtual test was carried out, and then applied the QC/T 480—1999 limit vehicle handling and stability indices and assessment methods to evaluate the results of the simulation, the result is 66.2247 points, among that, the resonant peak level is 36.0973 points, indicating the vehicle's steering transient response ability is poor, should be improved.

Design of a Preview Controller for Vehicle Rollover Prevention

This paper presents a method for designing a preview controller for vehicle rollover prevention. It is assumed that a driver's steering input is previewable with a Global Positioning System (GPS) and an inertial measurement unit (IMU), or with an automatic steering system for collision avoidance. Based on a linear vehicle model, a linear optimal preview controller is designed. To avoid the full-state measurement of a linear quadratic regulator (LQR), linear quadratic static output feedback (LQ SOF) control is adopted. To compare with several types of controllers such as LQR or LQ SOF with respect to rollover prevention capabilities, Bode plot analysis based on a linear vehicle model is performed. To show the effectiveness of the proposed controller, simulations are performed on a vehicle simulation package CarSim.

Optimization of Suspension Roll Center Height for Vehicle Handling Stability

Suspension roll characteristics are investigated using multi-body dynamic simulation software to analyze the handling stability of a coach air suspension system. Sensitivity analysis is applied to reveal the relationship between the guide mechanism geometry and roll center height of the suspension. The locations of V-pole mounts are adjusted to obtain a lower roll center position. The results of the steering wheel angle step input and steady-state circular tests are compared. To verify the effectiveness of vehicle model. Results indicate considerable improvement in handling stability, made possible by the low roll center height of the rear suspension.

Development of a tilt control method for a narrow-track three-wheeled vehicle

The space and weight savings provided by narrow tilting vehicles could make them a solution to the pollution and congestion problems seen in urban environments. The success of this new type of vehicle relies heavily on the control method used to balance the vehicle in corners. A tilting three-wheeled vehicle was developed at the University of Bath as part of an EU-funded project. The original direct tilt control method implemented on the prototype was shown to perform well in steady state, but rapid transients were shown to potentially lead to instability. A new type of controller was therefore required to reduce the load transfer across the rear axle during transient state manoeuvres. This paper presents a linearized model of the tilting vehicle system which is used to optimize a new tilt controller in the frequency domain. The controller, which uses combined steer and tilt control inputs, is shown to significantly reduce transient roll moments compared to the previous control method. This results in a much safer and more predictable handling characteristic.

Development of a hardware in the loop simulation system for electric power steering in vehicles

In this paper, a hardware-in-the-loop simulation (HILS) system was developed before the development of an electric power steering (EPS) system in a vehicle. This study was focused on the establishment of the HILS system. Driving conditions are simulated with the HILS system. The actual steering input parameters are confirmed on the monitor while driving the HILS system. The steering forces observed in the simulation with the developed HILS system are similar to those in real vehicle tests. The developed HILS system can be applied in the development of various types of EPS systems.

Design of a rollover prevention controller with differential game theory and a coevolutionary genetic algorithm

This paper presents a method for designing a rollover prevention controller with differential game theory and a coevolutionary genetic algorithm. In rollover situations, a driver’s steering input tends to make vehicles roll over. On the other hand, an active anti-roll bar can prevent the rollover. This situation can be modeled as a non-cooperative zero-sum two-player differential game. If an equilibrium solution to the differential game is obtained, it is guaranteed that the active anti-roll bar can prevent the rollover, even with the worst-case steering input. To obtain an equilibrium solution, this study presents a coevolutionary genetic algorithm. To show the effectiveness of this solution, simulations are performed on a vehicle simulation package, CarSim®.

Parameter estimation and validation of a tractor and single axle towed implement dynamic system model

Developing models and estimating model parameters for a tractor and implement system is important for rapid development and improvement of precision implement guidance systems. A dynamic model for a tractor with a towed implement was developed. This model contained a tire lateral force model with several parameters that are varying and difficult to measure accurately. Several field experiments were conducted to collect trajectory data for a tractor with a single axle grain cart. Data from these experiments were used to estimate the tire lateral force model parameters. Three different replicates of the experimental trajectories were collected with each of the step, random and chirp steering inputs. The data was collected at 4.5 m/s forward velocity in two different fields. A two-step optimization process was used to estimate the tire model parameters. First, the experimental data and a set of steady state model equations were used to estimate cornering stiffness parameters. Second, a prediction error minimization method and a dynamic model were used to estimate relaxation length parameters. The parameter estimation process was repeated with each replicate of the experimental data, and the individual estimates were combined using a weighted averaging method. The vehicle model responses with estimated parameters represented the system responses with reasonable accuracy. With the parameters estimated from three different trajectories, the RMSEs for trajectories of tractor and implement CGs varied from 0.05 to 0.83 m. The model-based frequency responses also closely matched with the experimental frequency responses.

Steering and Handling Performance During a Full Tire Tread Belt Separation

In this study, tests were performed with modified tires at the various front and rear positions on seventeen different vehicles to determine the effect of a full tire tread belt separation on a vehicle at highway speeds. The driver's steering and braking inputs were measured along with the vehicle responses during the event. The results show that the forces of a full tread belt separation generally do not force a vehicle out of a driver's control and that only small steering corrections are required to remain in the original lane of travel during the tread belt separation event. Additionally, forces due to the separating tires do not result in violent hop or tramp suspension responses during the separation event. 2011 SAE International.

InSt: An Integrated Steering Framework for Critical Weather Applications

Online remote visualization and steering of critical weather applications like cyclone tracking are essential for effective and timely analysis by geographically distributed climate science community. A steering framework for controlling the high-performance simulations of critical weather events needs to take into account both the steering inputs of the scientists and the criticality needs of the application including minimum progress rate of simulations and continuous visualization of significant events. In this work, we have developed an integrated user-driven and automated steering framework InSt for simulations, online remote visualization, and analysis for critical weather applications. InSt provides the user control over various application parameters including region of interest, resolution of simulation, and frequency of data for visualization. Unlike existing efforts, our framework considers both the steering inputs and the criticality of the application, namely, the minimum progress rate needed for the application, and various resource constraints including storage space and network bandwidth to decide the best possible parameter values for simulations and visualization.

Collision Avoidance System for Motorcycles (Automated Steering Control Using Model Predictive Control)

This study examines a collision avoidance system for motorcycles by automated steering control. The Model Predictive Control (MPC) is applied to the automated steering control with constraints on the motorcycle rolling motion by considering the rider's body movement in emergency avoidance. Two types of MPC controllers are designed and evaluated by the simple computer simulation of obstacle avoidance. One is a controller with a constraint on the rolling angle. The other is a controller with a constraint on the roll rate. Both controllers improve obstacle avoidance performance in comparison with the Liner Quadratic (LQ) controllers as conventional control theory. The MPC controller with the constraint on the roll rate decreases the roll rate under the permissible rolling angle. The controller with constraints on not only the roll rate but also the steering torque suppresses the large steering torque input. The improved avoidance performance by the MPC controller is observed at other vehicle velocities.