Closed-loop Driver-vehicle System Research Articles

Variable steering ratio control of steer-by-wire vehicle to improve handling performance

To improve vehicle handling performance, a variable steering ratio characteristic for steer-by-wire system is designed. The steering ratio is adjusted by a compensating coefficient according to vehicle longitudinal speed and steering wheel angle. To evaluate the performance of vehicle with variable steering ratio, simulations are conducted based on an objective evaluation index, which consists of quadratic cost functions of vehicle lateral deviation, steering angular speed, vehicle lateral acceleration and roll angle. By using the optimized data from the simulation results, a Takagi-Sugeno fuzzy neural network is designed for the steering ratio control. In order to test and validate the proposed controller, a series of comparison experiments are conducted on a closed-loop driver-vehicle system, including lemniscate curve test and double lane-change test. The results demonstrate that compared with a conventional steering system with fixed steering ratio, the proposed system can not only improve steering agility at low speed and steering stability at high speed, but also reduce driver’s workload in critical driving conditions.

Fault-Tolerant Control of Electric Ground Vehicles Using a Triple-Step Nonlinear Approach

This paper investigates a triple-step approach-based fault-tolerant control (FTC) strategy for in-wheel motor electric ground vehicles, whose purpose is to preserve stability, improve handling with in-wheel motors and/or steering system faults. The proposed scheme is divided into two levels. The first level is the integrated vehicle motion control with model uncertainties, disturbances and the possible actuator faults, in which a triple-step nonlinear controller with on-line updating laws is designed. The second level is the driving reference signal generation, where the triple-step feedback law is used to provide a quantitative driving guidance and a residual signal with threshold for monitoring and evaluating drivers. The proposed FTC scheme not only achieves the vehicle safety but also the high-availability of the closed-loop driver-vehicle system. Simulation results show the effectiveness of the proposed scheme.

Robust Integrated Control of Wheel Slip and Direct Yaw Moment for Stabilizing the Dynamics of Skid-Steering Vehicles

This paper presents a robust integrated control system to improve the stability and the handling performance of skid-steering vehicles. The control strategy is based on two layers: direct yaw moment control and wheel slip control. In the first layer, the direct yaw moment is obtained based on the nonlinear sliding mode control theory using the exact second order yaw rate response of the conventional steering vehicle. In the second layer, the direct yaw moment is optimally distributed to the four wheels in order to calculate the torque command needed at each wheel individually. Then, the sliding mode control theory is used again to control the torque command at each wheel individually and maintain the wheel slip at the desired value. A closed-loop driver-vehicle system subjected to a turning maneuver accompanied with braking at different surface conditions is simulated in Matlab/SIMULINK to validate the effectiveness of the proposed integrated control system. The simulation results show that the combination of wheel slip control and direct yaw moment is essential for stabilizing the motion of skid-steering vehicles. Moreover, the proposed control system is robust against uncertainty in the adhesion between the road surface and the wheel.

A Gain-Scheduling Driver Assistance Trajectory-Following Algorithm Considering Different Driver Steering Characteristics

In this paper, a gain-scheduling, robust, and shared controller is proposed to assist drivers in tracking vehicle reference trajectory. In the controller, the driver steering parameters such as delay time, preview time, and steering gain are assumed to be varying with respect to the different characteristics of drivers, vehicle states, and driving scenarios. Meanwhile, the modeling errors and uncertainties in the tire cornering stiffness are also considered in the driver–vehicle system model and the controller design. A global objective function, considering the tracking error, the driver's physical and mental workloads, and the control effort, is designed to optimize the overall performance of the driver–vehicle system. Constraint on eigenvalue placement is added to the controller design to improve the performance of the closed-loop driver–vehicle system. Simulation results under different maneuvers show that the controller can significantly improve the system performance and reduce the driver's workloads. The controller can reduce the delay time of the driver–vehicle system in emergency maneuvers, particularly for inexperienced drivers.

Analysis and research on the man-machine dynamics behaviour coupling mechanism of the super miniature electric vehicle

Safety, energy saving and environmental protection are the three mainstream directions of current automobile industry research. The super miniature electric vehicles (SMEVs) with their lightweight, miniaturisation, electrification, energy saving and environmental protection characteristics will be developed rapidly and popularly in the city road traffic in future. But the mass and size are reduced in the super miniature electric vehicles, to a certain extent, which may affect the cars' performance handling, such as stability, security and comfort. In this paper, the SMEVs market prospect is analysed firstly, next the necessity of research on the vehicle man-machine dynamics behaviour coupling mechanism is discussed. Finally the paper puts forward that the driver-vehicle closed-loop system, driver's seat posture change dynamic system and virtual human body model research are important for the man-machine dynamics coupling research to improve the performances of the SMEVs.

Analysis and research on the man-machine dynamics behaviour coupling mechanism of the super miniature electric vehicle

Safety, energy saving and environmental protection are the three mainstream directions of current automobile industry research. The super miniature electric vehicles (SMEVs) with their lightweight, miniaturisation, electrification, energy saving and environmental protection characteristics will be developed rapidly and popularly in the city road traffic in future. But the mass and size are reduced in the super miniature electric vehicles, to a certain extent, which may affect the cars' performance handling, such as stability, security and comfort. In this paper, the SMEVs market prospect is analysed firstly, next the necessity of research on the vehicle man-machine dynamics behaviour coupling mechanism is discussed. Finally the paper puts forward that the driver-vehicle closed-loop system, driver's seat posture change dynamic system and virtual human body model research are important for the man-machine dynamics coupling research to improve the performances of the SMEVs.

Vehicle Sideslip Angle Estimation Based on General Regression Neural Network

Aiming at the accuracy of estimation of vehicle’s mass center sideslip angle, an estimation method of slip angle based on general regression neural network (GRNN) and driver-vehicle closed-loop system has been proposed: regarding vehicle’s sideslip angle as time series mapping of yaw speed and lateral acceleration; using homogeneous design project to optimize the training samples; building the mapping relationship among sideslip angle, yaw speed, and lateral acceleration; at the same time, using experimental method to measure vehicle’s sideslip angle to verify validity of this method. Estimation results of neural network and real vehicle experiment show the same changing tendency. The mean of error is within 10% of test result’s amplitude. Results show GRNN can estimate vehicle’s sideslip angle correctly. It can offer a reference to the application of vehicle’s stability control system on vehicle’s state estimation.

Driver Steering Control and Full Vehicle Dynamics Study Based on a Nonlinear Three-Directional Coupled Heavy-Duty Vehicle Model

Under complicated driving situations, such as cornering brake, lane change, or barrier avoidance, the vertical, lateral, and longitudinal dynamics of a vehicle are coupled and interacted obviously. This work aims to propose the suitable vehicle and driver models for researching full vehicle dynamics in complicated conditions. A nonlinear three-directional coupled lumped parameters (TCLP) model of a heavy-duty vehicle considering the nonlinearity of suspension damping and tire stiffness is built firstly. Then a modified preview driver model with nonlinear time delay is proposed and connected to the TCLP model to form a driver-vehicle closed-loop system. The presented driver-vehicle closed-loop system is evaluated during a double-lane change and compared with test data, traditional handling stability vehicle model, linear full vehicle model, and other driver models. The results show that the new driver model has better lane keeping performances than the other two driver models. In addition, the effects of driver model parameters on lane keeping performances, handling stability, ride comfort, and roll stability are discussed. The models and results of this paper are useful to enhance understanding the effects of driver behaviour on full vehicle dynamics.

Understanding and Modeling the Human Driver Behavior Based on MPC

Better understanding driver behavior is essential for autonomous vehicles, as well as simulation, evaluation and optimization of a driver-vehicle closed-loop system. In this paper, the human driver behavior is first discussed in the form of perception, decision, and execution. In the following, the modelling of the driver behavior is proposed based on the preview-follower theory. The driver model includes three parts which are perception module, decision making module and execution module. The decision making module contains longitudinal control using proportional-integral-derivative (PID) controller and lateral control using model predictive control (MPC) method. Moreover, the response of muscle and nerve is modelled in the form of execution module. Typical simulations are carried out using vehicle dynamics software veDYNA and indicate that the proposed driver model is suitable for representative path following at varying vehicle speed.

A Study on Effect of Phase Delay and High Frequency Gain of Vehicle Behavior Corresponding to Steering Angle Input on Ease of Driving

This paper describes an investigation of the nonlinear filter that can design for gain and phase independently. In the driver-vehicle closed-loop system, it is reported that the phase delay of vehicle has an optimal value and reduces vehicle maneuverability if too large or too small. However, there is a deep relationship between the gain and phase delay in a linear system. It is difficult to evaluate the gain and phase delay of vehicle response independently. In this investigation, we tried to design a non-linear filter that can resolve the deep relationships between the gain and phase delay. We investigate the each effect of the gain and phase delay corresponding to the steering angle input on the ease of driving by using driving simulator, and evaluate the sensory evaluation and control performance on the lane change task. We verified the improvement of ease of driving by reducing a phase delay and decreasing a high frequency gain.

Study on soft computing arithmetic for vehicle yaw rate based on ANFIS

A soft computing arithmetic based on Adaptive Neuro-Fuzzy Inference System (ANFIS) is proposed to estimate vehicle yaw rate in a driver-vehicle closed loop system, and vehicle yaw rate is considered as a nonlinear mapping of time series of rack displacement and lateral acceleration. Simulation study on soft computing of vehicle yaw rate in the driver-vehicle closed loop system is conducted, and the performance of the soft computing arithmetic based on ANFIS is evaluated with the help of actual vehicle test data. Results indicate that the generalisation of the soft computing arithmetic based on ANFIS is better than that based on Radial Basis Function (RBF) neural network.

Studies on improving vehicle handling and lane keeping performance of closed-loop driver–vehicle system with integrated chassis control

This study proposes a new integrated robust model matching chassis controller to improve vehicle handling performance and lane keep ability. The design framework of the H ∞ controller is based on linear matrix inequalities (LMIs), which integrates active rear wheel steering control, longitudinal force compensation and active yaw moment control. To comprehensively evaluate the performance of the integrated chassis control system, a closed-loop driver–vehicle system is used. The effectiveness of the integrated controller on handling performance improvement is tested by a vehicle without driver model under a crosswind disturbance. At the same time, both the handling and lane keeping improving performance of the closed-loop driver–vehicle system is evaluated by tracking an S shape winding road. The simulation results reveal that the integrated chassis controller not only achieves preferable handling performance and stability, but also improves the vehicle lane keep ability significantly, and can alleviate the working load of the driver.

3811 操舵力が人間-自動車系の特性に及ぼす影響(G18-2 交通・物流部門(2),G18 交通・物流)

This paper describes a study on the relationship between the steering characteristics and driver's steering operation in the driver-vehicle closed-loop system. So we developed a driving simulator controlled by a new algorithm, which can design steering torque and angle independently. In the paper, dumping and natural frequency of the transfer function of steering angle/steering torque have how effect on the driver's steering action and the feeling. The experiment showed that the driver's steering action was changing deeply related on the steering torque, haptic information, as well as visual information. At last, we proposed the directional character of the steering torque.

Simultaneous Optimal Distribution of Lateral and Longitudinal Tire Forces for the Model Following Control

This paper presents a proposed optimum tire force distribution method in order to optimize tire usage and find out how the tires should share longitudinal and lateral forces to achieve a target vehicle response under the assumption that all four wheels can be independently steered, driven, and braked. The inputs to the optimization process are the driver’s commands (steering wheel angle, accelerator pedal pressure, and foot brake pressure), while the outputs are lateral and longitudinal forces on all four wheels. Lateral and longitudinal tire forces cannot be chosen arbitrarily, they have to satisfy certain specified equality constraints. The equality constraints are related to the required total longitudinal force, total lateral force, and total yaw moment. The total lateral force and total moment required are introduced using the model responses of side-slip angle and yaw rate while the total longitudinal force is computed according to driver’s command (traction or braking). A computer simulation of a closed-loop driver-vehicle system subjected to evasive lane change with braking is used to prove the significant effects of the proposed optimal tire force distribution method on improving the limit handling performance. The robustness of the vehicle motion with the proposed control against the coefficient of friction variation as well as the effect of steering wheel angle amplitude is discussed.

Examination of different models following types of yaw moment control strategy for improving handling safety of a car-caravan combination

This paper examines the effect of two model responses on the performance of model following types of direct yaw control (DYC). The model responses are the side-slip angle and yaw rate vehicle response of two-degree-of-freedom vehicle motion (bicycle model). The controls aim primarily at stabilizing the handling behaviour of a car-caravan combination as well as making its handling characteristics close to those of a single vehicle. Sensing of the lateral force exerted on a hitch point is essential for the control systems proposed. The estimated side-slip angle using the model observer was compared with the real side-slip angle measured by optical side-slip sensors. The effect of the model response is proved by computer simulations of a closed-loop driver-vehicle system subjected to evasive lane change with braking. It is found that the influence of the model response has a significant effect on the control performance.

Active wheel steering and yaw moment control combination to maximize stability as well as vehicle responsiveness during quick lane change for active vehicle handling safety

The aim of this paper is not only to present various methods for combining lateral force and yaw moment control but also to find out how the mix between them should be applied to maximize the stability limit as well as vehicle responsiveness. Approximated two-degree-of-freedom (2DOF) vehicle model responses of side-slip angle and yaw rate are used to introduce the required total lateral force and yaw moment control. Three different cases of combining lateral force and direct yaw moment control have been investigated using computer simulations. A direct yaw moment control to follow the yaw rate response only is taken as a comparison case in order to show the effect of the combined control on vehicle stability and responsiveness. A computer simulation of a closedloop driver-vehicle system subjected to quick lane change with braking is used to prove the influence of the combined control. It is found that the influence of the combined control on vehicle stability and responsiveness is significant.

Handling Safety Simulation of Driver-Vehicle Closed-Loop System with Evolutionary Random Road Input

The response simulation is studied and the handling safety is evaluated using finer integration method for driver-vehicle closed-loop system with stationary random road input. This algorithm is not only precise, but can also shorten the evaluation period of handling safety and reduce the tremendous cost for real vehicle testing. The response simulation and the vehicle handling safety evaluation are also studied for the closed-loop system with evolutionary random road input. The study can more truly simulate vehicle handling quality for including the varying of vehicle velocity with time.

Active Safety Performance Analysis of Man-Vehicle System due to Driver's Maneuver in Emergency Avoidance.

Taking driver-vehicle closed loop system into account, active safety performances in emergency situation were analysed and the evaluation methods were proposed. Under such critical conditions, ordinary driver's avoiding maneuvers were examined using a motion-type driving simulator. According to the driver's maneuvers, a database of driving operational characteristics was constructed and a mathematical model of driver's operation was also derived. The performance of the driver-vehicle system was predicted by computational simulations. The agreements with the predicted performance by the simulation were verified from experimental results in emergency avoidance. Assuming the sudden change of road surface to slippery situation, the effect of an assistant control of steering was also estimated from both model simulations and experiments by the driving simulator.

A control theoretic model of driver steering behavior

Following well-established feedback control design principles, a control theoretic model of driver steering behavior is presented. While accounting for the inherent manual control limitations of the human, the compensation dynamics of the driver are chosen to produce a stable, robust, closed-loop driver-vehicle system with a bandwidth commensurate with the demands of the driving task being analyzed. A technique for selecting driver model parameters is a natural by-product of the control theoretic modeling approach. Experimental verification shows the ability of the model to produce driver-vehicle responses similar to those obtained in a simulated lane-keeping driving task on a curving road.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>