Kanghyun Nam

Lateral Stability Control of In-Wheel-Motor-Driven Electric Vehicles Based on Sideslip Angle Estimation Using Lateral Tire Force Sensors

This paper presents a method for using lateral tire force sensors to estimate vehicle sideslip angle and to improve vehicle stability of in-wheel-motor-driven electric vehicles (IWM-EVs). Considering that the vehicle motion is governed by tire forces, lateral tire force measurements give practical benefits in estimation and motion control. To estimate the vehicle sideslip angle, a state observer derived from the extended-Kalman-filtering (EKF) method is proposed and evaluated through field tests on an experimental IWM-EV. Experimental results show the ability of a proposed observer to provide accurate estimation. Moreover, using the estimated sideslip angle and tire cornering stiffness, the vehicle stability control system, making best use of the advantages of IMW-EVs with a steer-by-wire system, is proposed. Computer simulation using Matlab/Simulink-Carsim and experiments are carried out to demonstrate the effectiveness of the proposed stability control system. Practical application of lateral tire force sensors to vehicle control systems is discussed for future personal electric vehicles.

Estimation of Sideslip and Roll Angles of Electric Vehicles Using Lateral Tire Force Sensors Through RLS and Kalman Filter Approaches

Robust estimation of vehicle states (e.g., vehicle sideslip angle and roll angle) is essential for vehicle stability control applications such as yaw stability control and roll stability control. This paper proposes novel methods for estimating sideslip angle and roll angle using real-time lateral tire force measurements, obtained from the multisensing hub units, for practical applications to vehicle control systems of in-wheel-motor-driven electric vehicles. In vehicle sideslip estimation, a recursive least squares (RLS) algorithm with a forgetting factor is utilized based on a linear vehicle model and sensor measurements. In roll angle estimation, the Kalman filter is designed by integrating available sensor measurements and roll dynamics. The proposed estimation methods, RLS-based sideslip angle estimator, and the Kalman filter are evaluated through field tests on an experimental electric vehicle. The experimental results show that the proposed estimator can accurately estimate the vehicle sideslip angle and roll angle. It is experimentally confirmed that the estimation accuracy is improved by more than 50% comparing to conventional methods one (see rms error shown in Fig. 4). Moreover, the feasibility of practical applications of the lateral tire force sensors to vehicle state estimation is verified through various test results.

Vehicle state estimation for advanced vehicle motion control using novel lateral tire force sensors

In this paper, new real-time methods for the lateral vehicle velocity and roll angle estimation are presented. Lateral tire forces, obtained from a multi-sensing hub (MSHub) unit, are used to estimate lateral vehicle velocity and a roll angle. In order to estimate lateral vehicle velocity, the recursive least square (RLS) algorithm is utilized based on a linear vehicle model and sensor measurements. In the roll angle estimation, the Kalman filter is designed for real-time estimation. The proposed estimation methods, RLS-based estimator and the Kalman filter, were verified by field tests on an experimental electric vehicle. Test results show that the proposed estimation methods provide better estimation performances and these methods are robust to road conditions.

Design of an adaptive sliding mode controller for robust yaw stabilisation of in–wheel–motor–driven electric vehicles

A robust yaw stability control system is designed to stabilise the vehicle yaw motion. Vehicles undergo changes in parameters and disturbances with respect to the wide range of driving conditions, e.g., tyre–road conditions. Therefore, a robust control design technique is required to guarantee system stability and enhance the robustness. In this paper, a sliding mode control methodology is applied to make vehicle yaw rate to track its reference with robustness against model uncertainties and disturbances. In addition, a parameter adaptation law is also applied to estimate varying vehicle parameters with respect to road conditions and is incorporated into sliding mode control framework. The control performance of the proposed control system was evaluated through field tests.

Design of an adaptive sliding mode controller for robust yaw stabilisation of in-wheel-motor-driven electric vehicles

A robust yaw stability control system is designed to stabilize the vehicle yaw motion. Since the vehicles undergo changes in parameters and disturbances with respect to the wide range of driving condition, e.g., tire-road conditions, a robust control design technique is required to guarantee system stability. In this paper, a sliding mode control methodology is applied to make vehicle yaw rate to track its reference with robustness against model uncertainties and disturbances. A parameter adaptation law is applied to estimate varying vehicle parameters with respect to road conditions and is incorporated into sliding mode control framework. The control performance of the proposed control system is evaluated through computer simulation using CarSim vehicle model which proved to give a good description of the dynamics of an experimental in-wheel-motor-driven electric vehicle. Moreover, field tests were carried out to verify the effectiveness of the proposed adaptive sliding mode controller

Two-dimensional assist control for power-assisted wheelchair considering straight and rotational motion decomposition

There are many types of wheelchairs. Users are able to choose suitable wheelchair for their purposes. Power-assisted wheelchairs are one type of wheelchairs, which use both propelling torque from human and output torque from motors for their driving force. To improve assist performance, many assist control systems were proposed. One of conventional assist control, proposed by Seki et al., is designed for motion of traveling in straight line. However, it is difficult for wheelchair users to rotate using conventional assist control. In this paper, a novel two-dimensional assist control for power-assisted wheelchairs is proposed. The proposed assist control system is designed for both straight and rotational motion of wheelchair, therefore, power assist performance in rotating motion is improved compared to conventional system.

Yaw motion control of power-assisted wheelchairs under lateral disturbance environment

Wheelchairs are important devices for people with leg disabilities. There are many kinds of wheelchairs being developed to minimize injury while improve ease of operation. Power-assisted wheelchairs were developed for the same reason. However, due to effects of gravity, power assist alone is not sufficient to make movement on slopes easy. Lateral disturbances make the wheelchairs speed as well as direction unable to manage, which can cause accidents leading to injury. To overcome this problem, we propose yaw motion control of power-assisted wheelchairs. Using yaw motion control, a wheelchair would not be subjected to influence from lateral disturbance, and hence overall performance of the wheelchair would improve. To demonstrate the effectiveness of the yaw motion control, two kinds of experiments have been performed: going straight on the slope, and turning on the slope. Effectiveness of the proposed control system has been verified by experiments.

Steering Angle-Disturbance Observer (SA-DOB) based yaw stability control for electric vehicles with in-wheel motors

In this paper, a robust yaw stability control design based on active steering control is proposed for electric vehicles. The control system consists of an inner-loop controller (i.e., in this paper, called as a Steering Angle-Disturbance Observer(SA-DOB) which rejects an input steering disturbance and an output yaw disturbance simultaneously by feeding a compensation steering angle) and an outer-loop controller (i.e., PI-type Tracking Controller) to achieve the control performances. The control performance of the proposed yaw stability control system is verified through computer simulations and experiments.

Motion control of electric vehicles based on robust lateral tire force control using lateral tire force sensors

This paper proposes a new motion control method based on robust lateral tire force control. Since the lateral tire force measurements are available by using multi-sensing hub (MSHub) units which are invented by NSK Ltd, direct lateral tire force control is realizable via active front steering. In control design, robust control method, e.g., 2-degree-of-freedom control (2-DOF) with disturbance observer (DOB), is used for improving the lateral tire force tracking. The proposed motion controller is implemented on an experimental in-wheel-motor-driven electric vehicle and its control performance and effectiveness are verified through experimental results. Finally, practical applications of lateral tire force sensors to vehicle motion control systems are discussed.

Development of a camless engine valve actuator system for robust engine valve timing control

In this paper, a camless engine valve actuator (CEVA) system for robust engine valve timing control is presented. A particularly challenging control obstacle, shown in hydraulic actuation system for camless engine valve actuators, is the sluggish response of valve actuators at a cold operating condition. This is mainly due to the characteristics of oil viscosity with respect to temperature changes. At a low temperature condition, CEVA shows the very sluggish response. The retarded valve opening and closing timing, by CEVA’s slow response at low temperature, causes an increase in pollutant emission and cylinder temperature during engine operation. In order to avoid these adverse effects by retarded timing, the new valve timing controller is proposed to control opening timing and closing timing, which is robust against temperature variations. A proposed valve timing controller is for guaranteeing the valve timing repeatability without using expensive position sensors. Experimental results indicate the feasibility of a fully variable valve timing control and CEVA system which can be constructed at a low cost.