Etsuo Katsuyama

Decoupled 3D moment control using in-wheel motors

Vehicles equipped with in-wheel motors are being studied and developed as a type of electric vehicle. Since these motors are attached to the suspension, a large vertical suspension reaction force is generated during driving. Based on this mechanism, this paper describes the development of a method for independently controlling roll and pitch as well as yaw using driving force distribution control at each wheel. It also details the theoretical calculation of a method for decoupling the dynamic motions. Finally, it describes the application of these 3D dynamic motion control methods to a test vehicle and the confirmation of the performance improvement.

Direct Yaw Moment Control and Power Consumption of In-Wheel Motor Vehicle in Steady-State Turning

ABSTRACT Driving force distribution control is one of the characteristic performance aspects of in-wheel motor vehicles and various methods have been developed to control direct yaw moment while turning. However, while these controls significantly enhance vehicle dynamic performance, the additional power required to control vehicle motion still remains to be clarified. This paper constructed new formulae of the mechanism by which direct yaw moment alters the cornering resistance and mechanical power of all wheels based on a simple bicycle model, including the electric loss of the motors and the inverters. These formulation results were validated by an actual test vehicle equipped with in-wheel motors in steady-state turning. The validated theory was also applied to a comparison of several different driving force distribution mechanisms from the standpoint of innate mechanical power.

Efficient direct yaw moment control: tyre slip power loss minimisation for four-independent wheel drive vehicle

ABSTRACT This paper proposes an efficient direct yaw moment control (DYC) capable of minimising tyre slip power loss on contact patches for a four-independent wheel drive vehicle. Simulations identified a significant power loss reduction with a direct yaw moment due to a change in steer characteristics during acceleration or deceleration while turning. Simultaneously, the vehicle motion can be stabilised. As a result, the proposed control method can ensure compatibility between vehicle dynamics performance and energy efficiency. This paper also describes the results of a full-vehicle simulation that was conducted to examine the effectiveness of the proposed DYC.

Control-oriented modelling and experimental modal analysis of Electric Vehicles with geared In-Wheel Motors

Electric Vehicles (EV) equipped with independent drives are capable of controlling the car body motion in multiple degrees-of-freedom with driving force distribution through the suspension reaction force. These electric powertrains could thus suppress primary (1 – 3Hz) and secondary (4 – 10Hz) resonant modes improving ride comfort, road holding and safety of passenger cars. On-Board-Motor (OBM) drivetrains can subdue primary vibrations including the heave, pitch and roll modes, but are limited by the torsional resonance of the half-shaft. In-Wheel-Motor (IWM) drivetrains alleviate the torsional restriction potentially reaching higher bandwidths and thereby improving road holding and passenger comfort. However, the additional unsprung mass aggravates the secondary vibration urging for an appropriate motion control design. This research proposes a dynamic model in multiple degrees-of-freedom for vibration suppression control and an experimental validation of both primary and secondary dynamics in EVs. In this work, the vibration performance of both powertrains are compared on a test vehicle in experimental and operational conditions. Moreover, the modal coupling between the torsional, longitudinal and vertical motions are analysed and the slip-ratio dependency assessed. The deterioration in dynamic behaviour using IWMs is demonstrated and a precise parametric model identified for vibration suppression control of geared In-Wheel-Motor drivetrains.

Model-based longitudinal vibration suppression control for electric vehicles with geared in-wheel motors

In vehicle motion control, it is important to improve both dynamic performance and ride comfort by vibration suppression. Vehicles with combustion engines or on-board motors can only suppress resonant modes in the low frequency band such as the heave, pitch, and roll modes due to the limitation in torque responsiveness. However, in the case of vehicles with in-wheel motors, it is possible to suppress vibration in the higher frequency range. In order to improve motion performance and ride comfort, we propose a two degrees of freedom control using an experimentally identified plant model of a geared in-wheel motor vehicle. Application of the proposed method improves the vehicle body longitudinal response characteristics while suppressing the vibration. In order to further improve the performance, a state observer that takes the delay of CAN communication into consideration is applied while securing stability margin. The effectiveness of the proposed method is evaluated by simulations and experiments.