Dynamics control of autonomous vehicle at driving limits and experiment on an autonomous formula racing car

In order to improve handling performance of a hybrid 8-Wheel-Drive vehicle, the handling performance control strategy was proposed. For armoured vehicle, besides handling stability in high speed, the minimum steer radius in low speed is also a key tactical and technical index. Based on that, the proposed handling performance control strategy includes ‘Handling Stability’ and ‘Radius Minimization’ control modes. In ‘Handling Stability’ control mode, ‘Neutralsteer Radio’ is defined to adjust the steering characteristics to satisfy different demand in different speed range. In ‘Radius Minimization’ control mode, the independent motors are controlled to provide an additional yaw moment to decrease the minimum steer radius. In order to verify the strategy, a simulation platform was built including engine and continuously variable transmission systems, generator and battery systems, independent motors and controllers systems, vehicle dynamic and tyre mechanical systems. The simulation results show that ...

Handling performance control for hybrid 8-wheel-drive vehicle and simulation verification

The pivotal steering ability of a skid-steered vehicle is an important advantage compared with the steering ability of an Ackermann steered vehicle. In the pivotal steering condition, the strong non-linearity of the properties of the tyres makes prediction of the dynamic modelling and the performance difficult. For this purpose, this paper proposes an experimentally validated dynamic model to describe the motion of a skid-steered vehicle in the pivotal steering condition. The mechanical analytical model of the tyres was constructed on the assumption of an ‘elliptical parabolic’ contact pressure distribution. The dynamic model has nine degrees of freedom, including the longitudinal motion, the lateral motion and the yaw motion of the body and also the rotation of the wheels; the motor saturation is also considered. The analysis and experiments were based on a specific 6 × 6 unmanned skid-steered vehicle which is driven by six independent in-wheel motors, and the driving control algorithm of the vehicle was...

https://journals.sagepub.com/doi/pdf/10.1177/0954407016652760

Dynamic modelling and experimental validation of a skid-steered vehicle in the pivotal steering condition

Multibody dynamics (MBD) covers a system of many bodies linked together via kinematic constraints. Thus, EOM (equations of motion) of a multibody system basically contain constraint equations between bodies, which are non-linear equations. Also, the forces acting on the system, such as contact force between bodies or damping forces etc., are usually highly non-linear. In this paper, several MBD applications in design were introduced based on researches carried out in the NRL (National Research Laboratory) of CAE in Korea. ANCF (Absolute nodal coordinate formulation) simulations and experiments, unwinding mechanism of cables, AutoDyn7 (Automobile Dynamics in G7 project) program, PNU (Pusan National University) driving simulator, air-cell seat for passenger cars, optimum speed decision of an unmanned autonomous vehicle, MBD modeling of a drum type washing machine and circuit breaker were introduced. And non-linear mechanics involved in MBD modelings of those systems were also explained.

MBD applications in design

Skid-steering technology has been widely used for wheeled vehicles, because a skid-steered vehicle has great mobility so that it is able to pivot steer a larger internal hull volume. In this paper, an 8 × 8 skid-steered all-terrain vehicle equipped with a double-stream hydromechanical transmission was introduced. In order to discuss the handling performance and to obtain general conclusions, an analytical lateral dynamic model of a skid-steered vehicle was proposed and verified experimentally. Furthermore, the handling performance of the skid-steered vehicle was compared with an Ackermann steered vehicle of the same dimensions. The results show that the skid-steered vehicle has a lower ‘stability factor’ and a totally different motion attitude, that the turn centre of the skid-steered vehicle will move forwards during acceleration at a constant radius and that the transient handling performance of the skid-steered vehicle is better than that of the Ackermann steered vehicle. Furthermore, from an analysis ...

Dynamic modelling, validation and handling performance analysis of a skid-steered vehicle

For an autonomous vehicle that travels off-road, the driving speed is limited by the driving circumstances. To decide on a stable manoeuvring speed, the driving system should consider road conditions such as the height of an obstacle and road roughness. In general, an autonomous vehicle has many sensors to preview road conditions, and the information gathered by these sensors can be used to find the proper path for the vehicle to avoid unavoidable obstacles. However, sensor data are insufficient for determining the optimal vehicle speed, which could be obtained from the dynamic response of the vehicle. This paper suggests an algorithm that can determine the optimal vehicle speed running over irregular rough terrains such as when travelling off-road. In the determination of the manoeuvring speed, the vehicle dynamic simulation is employed to decide whether the vehicle response is within or beyond the prescribed limits. To determine the manoeuvring speed in real time, the dynamic simulation should b...

Manoeuvring speed of a 6×6 autonomous vehicle using a database obtained from multi-body dynamic simulation

In multibody dynamic analysis, one of the most important problems is to reduce computation times for real-time simulation. This paper presents the derivation procedure of equations of motion of a 6x6 autonomous vehicle in terms of chassis local coordinates which do not require coordinates transformation matrix to enhance efficiency for real-time dynamic analysis. Also, equations of motion are derived using the VT(velocity transformation) technique and symbolic computation method coded by MATLAB. The Jacobian matrix of the equations of motion of a system is derived from symbolic operations to apply the implicit integration method. The analysis results were compared with ADAMS results to verify the accuracy and approve the feasibility of real time analysis.

A Study on the Real-Time Analysis of a 6×6 Autonomous Vehicle

: A driver-vehicle model means the integrated dynamic model that is able to estimate the steering wheel angle from the driver's desired path based on the dynamic characteristics of the driver and vehicle. Autonomous driving robot for factory automation has individual four-wheels which are driven by electronic motors. In this paper, the dynamic characteristics of several four-wheel steering systems with the simultaneously steerable front and rear wheels are investigated and compared by means of the driver-vehicle model. A diver- vehicle model is proposed by using the PID control to velocity and trajectory of control autonomous driving robot. To determine the optimum speed of a autonomous driving robot, steady-state circle simulation is carried out with the ADAMS program and MATLAB control model . Key words : Four-wheel steering system(4륜조향시스템) Desired path(요구경로), PID controller(비례-적분-미분 제어기), Steady-state conering( 정상원선회 ) 1. 서 론 1) 지능형로봇이란 외부환경을 인식하고 스스로 상황을 판단하여 자율적으로 동작하는 로봇을 말한다. 이러한 지능형 로봇은 사무실이나 공장 그리고 국방산업분야에서 무인화의 일환으로 많이 사용되고 있다. 공장의 경우 일정단위의 제품을 한 장소에서 다른 장소로 운반하는 무인운반 시스템을 통해 생산단가증가 문제를 극복하고 생산성 향상을 위해활용 된다. 이에 자율주행이 가능한 공장용 지능 형 주행로봇에 대한 연구가 활발히 진행되고 있다. 특히 고령화와 노동력 부족에 따라 지능형 로봇에 대

Jung-Han Lee

Papers

Manoeuvring speed of a 6×6 autonomous vehicle using a database obtained from multi-body dynamic simulation

A Study on the Real-Time Analysis of a 6×6 Autonomous Vehicle

A Study on the Optimum Velocity of a Four Wheel Steering Autonomous Robot