Simulation Analysis of an Off-road SUV for Steady state

Performance

Shujun Yang, Youxiang Zhou, Yang Liu, DandanLiu

College of Vehicle and Energy, Yanshan University, Qinhuangdao 066004

Phone: 15031462566; E-mail: 15931772766@163.com

Abstract - Steady-state performance is an important part of vehicle handling stability, and is significant to steering safe ty. In this paper, a steady-state simulation model of an off-road SUV is established in ADAMS/CAR. The curve of steering wheel angle changing with lateral acceleration on a constant radius turn, coincides with the result of the bicycle model. According to GB/T 6323.6-94, steady-state cornering simulation analysis is carried out by this model, and the result shows that the vehicle has good steady-state performance.

Index Terms - Off-road SUV; Handling Stability; Steady-state Cornering; Simulation Analysis

I.INTRODUCTION

With the rapid development of automotive industry, consumers requirements on vehicles performance are also gradually improved, not only should the vehicle have good dynamic performance and fuel economy, but also have good handling stability. Steady-state performance is an important part of vehicle handling stability [1-4]. Vehicles simulation analysis can be carried out quickly by using virtual prototype technology, and it can forecast vehicles handling stability [5-8]. However, it is difficult to guarantee the accuracy of simulation analysis. Road test can reflect handling stability accurately, but the research period is long and the cost is high. In this paper, a steady-state simulation model of an off-road SUV is established in ADAMS/CAR. The curve of steering wheel angle changing with lateral acceleration on a consatnt radius, coincides with the result of bicycle model. According to GB/T 6323.6-94, steady-state cornering simulation analysis is carried out by this model [9-10].

I I. CONTENTS

A Monorail Linear Biaxial Modeling

In order to study the steady-state performance of vehicle, firstly, the relationship between steering wheel angle and lateral acceleration [11] will be deduced theoretically.

Fig. 1 is the force model of bicycle model.

Fxv and FxH laid in the wheel direction are front and rear tangential force, Fyv and FyH perpendicular to the wheel force are lateral force, air lateral force FLy and air resistance

FLx are in the center of the wind pressure DP, the distance between DP and SP is esp

If the quality of vehicle is m, the moment of inertia bypass the vertical axis(SP ) is Jz, the front wheel steering angle is Ii v, balance equation can be written:

Balance equation of vehicle longitudinal axis:

Balance equation of the perpendicular direction to the longitudinal axis of the vehicle:

Balance equation of the direction bypass the vertical axis(SP):

Simplified formulation:

The above three equations are kinematics differential equations for bibycle model.

When the vehicle runs at a constant speed (v=O), formula (5) and (6) can be simplified as follows:

Where

When the vehicle drives on the circumference with a radius p at a constant speed V, it can be concluded:

According to:

This formula(7) and (8) can be simplified:

According to formula (9), (10) and (11), the input of steering wheel can be counted:

Formula (12) shows that the steering wheel input 0 sw change with V2/ P for a linear in the linear range (lateral acceleration is less than 0.3 g ), when the vehicle runs on the steady state circumference.

The total transmission ratio of steering system for reference vehicle is:

ir=540/33.6=16.1, 1=2790mm, m=2418kg, IH=1350mm,

1v=1350m, Cav=1 000/(1 1000 X 29/3/5695)=379(N/(deg)),

CaH=1OOO(N/(deg)).

When p = 100 m, the above datas are taken into (12): °sw=25.7 29.6 bull; // p

B Establishment of Vehicle Simulation Model

For the convenience of model establishment and modification, the vehicle breaks down into multiple subsystems: front suspension system, rear suspension system, steering system, body system, tires and power train system.

Each subsystem is established and debugged separately. Finally, vehicle model is assembled. Fig. 2 is the vehicle simulation analysis model.

C Simulation Analysis of Steady-state Circular with Set Radius

The process of steady circular drive test on a constant radius is that the vehicle runs at a given speed on the circumference with a set radius and increases speed gradully: FirstIy,the speed is very low and the centrifugal force is close to zero; Then the speed is raised to maximum centripetal acceleration under steady-state conditions. In this simulation, the vehicle runs on the radius of 100m when lateral acceleration changes from O.Olg to 0.67g. The curve of steering wheel input changing with the lateral acceleration is shown in Fig. 3.

According to the result of simulation analysis, when the lateral acceleration is less than 0.3 g and vehicle runs at steady-state circular with set radius , the steering wheel input /i sw change with V2/ P for a linear (as shown in Fig. 3 blue dotted line), the simulation results (as shown in Fig. 3 red solid line)are consistent with the theoretical analysis results. When the lateral acceleration of vehicle is larger than 0.3 g, the tire side-slip angle and lateral force are not linear relationship. Although the tire has slipped partly, the lateral force will continue to increase and the tire side-slip angle increases sharply. If the original radius of vehicle is constant, the steering wheel angle also increases sharply [12].

D Steady circular simulation analysis in national standards

According to GB/T6323.6-94, the whole vehicle

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Simulation Analysis of an Off-road SUV for Steadyshy; state

Performance

Shujun Yang, Youxiang Zhou, Yang Liu, DandanLiu

College of Vehicle and Energy, Yanshan University, Qinhuangdao 066004

Phone: 15031462566; E-mail: 15931772766@163.com

Abstract - Steady-state performance is an important part of vehicle handling stability, and is significant to steering safe ty. In this paper, a steady-state simulation model of an off-road SUV is established in ADAMS/CAR. The curve of steering wheel angle changing with lateral acceleration on a constant radius turn, coincides with the result of the bicycle model. According to GB/T 6323.6-94, steady-state cornering simulation analysis is carried out by this model, and the result shows that the vehicle has good steady-state performance.

Index Terms - Off-road SUV; Handling Stability; Steady-state Cornering; Simulation Analysis

I.INTRODUCTION

With the rapid development of automotive industry, consumers requirements on vehicles performance are also gradually improved, not only should the vehicle have good dynamic performance and fuel economy, but also have good handling stability. Steady-state performance is an important part of vehicle handling stability [1-4]. Vehicles simulation analysis can be carried out quickly by using virtual prototype technology, and it can forecast vehicles handling stability [5-8]. However, it is difficult to guarantee the accuracy of simulation analysis. Road test can reflect handling stability accurately, but the research period is long and the cost is high. In this paper, a steady-state simulation model of an off-road SUV is established in ADAMS/CAR. The curve of steering wheel angle changing with lateral acceleration on a consatnt radius, coincides with the result of bicycle model. According to GB/T 6323.6-94, steady-state cornering simulation analysis is carried out by this model [9-10].

I I. CONTENTS

A Monorail Linear Biaxial Modeling

In order to study the steady-state performance of vehicle, firstly, the relationship between steering wheel angle and lateral acceleration [11] will be deduced theoretically.

Fig. 1 is the force model of bicycle model.

Fxv and FxH laid in the wheel direction are front and rear tangential force, Fyv and FyH perpendicular to the wheel force are lateral force, air lateral force FLy and air resistance

FLx are in the center of the wind pressure DP, the distance between DP and SP is esp

If the quality of vehicle is m, the moment of inertia bypass the vertical axis(SP ) is Jz, the front wheel steering angle is Ii v, balance equation can be written:

Balance equation of vehicle longitudinal axis:

Balance equation of the perpendicular direction to the longitudinal axis of the vehicle:

Balance equation of the direction bypass the vertical axis(SP):

Simplified formulation:

The above three equations are kinematics differential equations for bibycle model.

When the vehicle runs at a constant speed (v=O), formula (5) and (6) can be simplified as follows:

Where

When the vehicle drives on the circumference with a radius p at a constant speed V, it can be concluded:

According to:

This formula(7) and (8) can be simplified:

According to formula (9), (10) and (11), the input of steering wheel can be counted:

Formula (12) shows that the steering wheel input 0 sw change with V2/ P for a linear in the linear range (lateral acceleration is less than 0.3 g ), when the vehicle runs on the steady state circumference.

The total transmission ratio of steering system for reference vehicle is:

ir=540/33.6=16.1, 1=2790mm, m=2418kg, IH=1350mm,

1v=1350m, Cav=1 000/(1 1000 X 29/3/5695)=379(N/(deg)),

CaH=1OOO(N/(deg)).

When p = 100 m, the above datas are taken into (12): °sw=25.7 29.6 bull; // p

B Establishment of Vehicle Simulation Model

For the convenience of model establishment and modification, the vehicle breaks down into multiple subsystems: front suspension system, rear suspension system, steering system, body system, tires and power train system.

Each subsystem is established and debugged separately. Finally, vehicle model is assembled. Fig. 2 is the vehicle simulation analysis model.

C Simulation Analysis of Steady-state Circular with Set Radius

The process of steady circular drive test on a constant radius is that the vehicle runs at a given speed on the circumference with a set radius and increases speed gradully: FirstIy,the speed is very low and the centrifugal force is close to zero; Then the speed is raised to maximum centripetal acceleration under steady-state conditions. In this simulation, the vehicle runs on the radius of 100m when lateral acceleration changes from O.Olg to 0.67g. The curve of steering wheel input changing with the lateral acceleration is shown in Fig. 3.

According to the result of simulation analysis, when the lateral acceleration is less than 0.3 g and vehicle runs at steady-state circular with set radius , the steering wheel input /i sw change with V2/ P for a linear (as shown in Fig. 3 blue dotted line), the simulation results (as shown in Fig. 3 red solid line)are consistent with the theoretical analysis results. When the lateral acceleration of vehicle is larger than 0.3 g, the tire side-slip angle and lateral force are not linear relationship. Although the tire has slipped partly, the lateral force will continue to increase and the tire side-slip angle increases sharply. If the original radius of vehicle is constant, the steering wheel angle also increases sharply [12].

D Steady circular simulation analysis in national standards

According to GB/T6323.6-94, the w

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