Recently, to produce a large steering torque or ensure fault-tolerant control (FTC), dual motorized actuators for a steering system in automobiles have been emerged. In particular, the commercial vehicle requires an electrical-powered multiple motor based steering system generating large steering torque, which can replace the existing hydraulic steering one. However, the control of such system become more complicate than controlling of a single actuator and must deal with the unavoidable non-synchronous nature of multiple motors. In line with the trends and issues, many automobile manufacturers are currently paying attention to the robust and efficient motion controls of a dual-motor driving steer-by-wire (DSBW). Therefore, we proposed a novel synchronous motion control system of DSBW using passive decomposition and sliding mode control (SMC) techniques guaranteeing the passivity and robustness of the overall synchronized motion. Furthermore, the performance of proposed control system is validated through HILS of an actual DSBW using a developed vehicle model and an optimal finite preview control (OFPC) scheme tracking a specific test scenario, Double Lane Change (DLC). It is found that the motor-to-motor synchronization error and tracking one for the target reference trajectory are less than 1 degree, which sufficiently meets the requirement of automobiles manufacture company and is comparable to other existing approaches. We also investigated the tracking performance of the control system based on the different steering characteristics of OFPCs generated by the several preview times. Moreover, we investigated the tolerance level of proposed technique (without any additional FTC) against a partial fault condition in one of the motors and compared it with other control schemes in terms of tracking performance. This work will be valuable asset for those who wish to design the robust synchronous motion control of DSBW and construct the corresponding HILS of system considering different steering characteristics.

The advancement of electrical power steering system (EPSS) in a vehicle system has moved forward for decades. However, before the era of the complete autonomous vehicles comes, many investigations are still underway to improve EPSS characteristics and performance for the human driver interactions, while conducting both actual field tests and indoor HILS. Meanwhile, to replace the costly and time-consuming field tests, the indoor EPSS based HILS has been frequently used as an alternative to explore the characteristics of an actual EPSS and mimic the steering reaction torque created by a real car. However, the recent EPSS Hardware-In-the-Loop (HIL) simulators become computationally expensive, complicated as well as costly by integrating several software(s) with the hardware(s). This might be extravagant for those who wish to practically implement those systems within a limited budget. Therefore, we proposed a compact, cost-effective and minimum hardware-based EPSS HIL simulator interacting with a human driver. Specifically, the dynamic models of 3-D.O.F vehicle and EPSS are constructed on the virtual environment (MATLAB/Simulink), and the dynamic behavior of EPSS, generated by those virtual models, has been mimicked via an actual motor and delivered to actual test participants operating the simulator. The effectiveness and accuracy of the proposed simulator in conjunction with a human driver have been compared with the simulation results of certified Carsim software. In addition, for our future studies, the dynamic responses of the vehicle body and EPSS under the effect of cross-wind have been explored based on the proposed simulator and, the average of human driver's torque to compensate for the effect has been finally addressed.

The wind suddenly blown to the side of the car (i.e, cross-wind effect) is considered as one of the major lateral disturbances, which causes the unstable motion of the vehicle and the persistent driving fatigue for the driver who tracks the desired travel path. In particular, a commercial vehicle having a large side area is greatly affected by this effect. Therefore, many related automotive/car manufacturers still wish to equip their Advanced Driving Assistant System (ADAS) with the crosswind disturbance compensation control system. Meanwhile, in recent advanced vehicle systems, a rack-type motor-driven power steering (R-MDPS) system is more widely used than a column-type MDPS (C-MDPS) due to the structure advantage and the effective steering assistance. Recognizing those two issues, this paper investigates a novel anti-control and estimation strategy of crosswind disturbance for the R-MDPS system of vehicles with non-negligible side surfaces. Specifically, an adaptive disturbance observer (D.O.B) has been proposed to estimate the crosswind effect. Furthermore, using optimal control theory, the compensation control system is designed to assist the driver in two possible situations. One is for when the driver continues to steer the vehicle under the effect of the crosswind, and the other is for when the driver temporarily loses steering control due to the effect. In addition, the control mode selection conditions between two controls are clearly presented to maximize the efficiency and performance of the proposed control system. Finally, the effectiveness of the proposed control system has been evaluated based on the Simulink/Carsim Co-simulation and HILS environments.

This paper explores the new control strategy of an actively actuated eccentric mass system (AAEMS) for cancelling the rotor imbalance vibration. The AAEMS consists of an eccentric mass with an actuator that actively moves around the circular guided track attached to the rotating rotor thus can generate an effective centrifugal force perpendicular to any tangential direction of the guided circular trajectory. Therefore, once the magnitude and angular position of the inherited static imbalance of the rotor are identified, this actively controlled system can be dispatched to the target angular position(s) where the effective centrifugal force due to rotor imbalance is completely or partially removed. This novel device is currently available and widely used in the vibration isolation problem. However, the study of its control strategy is quite limited, thus, herein, we proposed a new possible control technique, guaranteeing both the robust vibration isolation performance and less control power consumption. To meet such needs, three primary functions of AAEMS are addressed here. First, two (Extended) Kalman filters were employed to sequentially estimate the unknown imbalance of the rotor and the unknown coulomb friction induced between the contact surface of the circular track and the counter-contacted parts of AAEMS. Second, the position control of the AAEMS is achieved by a linear quadratic regulator (LQR)-based optimal control law, simultaneously minimizing the imbalance vibration of the rotor as well as the power consumption of its own actuator. Third, for the situation where the estimation and control errors are presented, thus causing the failure to an acceptable threshold for imbalance vibration, the trial-error-based fine-tuning angular position control was proposed. The effectiveness of the proposed control strategy was evaluated via the simulations and this study shows the practical potential for addressing the AAEMS-based imbalance vibration elimination.

Although the various synchronous control techniques of a master-slave manipulator have been explored and developed over the decades, the investigations of the synchronous control for those systems with strong asymmetric dead-zone characteristics have been limited and not been fully considered. Hence, we proposed the robust and easy-to-implement estimation and control strategy to compensate for the actuator’s dead-zone effect and to guarantee synchronous performance. Specifically, we set up a two-step process called prior-estimation control to avoid the performance degradation due to the frequent failures of the desired estimation in a standard adaptive control. The first step is to adaptively estimate the asymmetric nonlinear dead-zone parameters via the Recursive Least Square (RLS) method. At the second stage, those estimated parameters via RLS are delivered to the main synchronous control system designed by a passivity-based sliding mode control technique along with inverse dead-zone control, and then the control is executed whenever a human operator interacts with the system. Finally, the effectiveness of the proposed approach has been validated by the actual 2-D.O.F master-slave manipulators equipped with cost-effective actuators with an inevitable asymmetric dead-zone. This work will be especially a valuable asset for those who wish to accurately control the master-slave systems with dead-zone characteristics such as the industrial construction multiple joints based fork cranes or lifts.

Due to inherent nonlinearity of the autobalancer, the potential for other, undesirable, nonsynchronous limit-cycle vibration exists. In such undesirable situations, the balancer masses do not reach their desired synchronous balanced steady-state positions resulting in increased rotor vibration. Such behavior has been widely studied and is well understood for rotor systems on idealized bearings with symmetric supports. However, a comprehensive study into this nonlinear behavior of an imbalanced planar-rigid rotor/autobalancing device (ABD) system mounted on a general bearing holding asymmetric damping and stiffness forces including nonconservative effects cross-coupling ones has not been fully conducted. Therefore, this research primarily focuses on the unstable nonsynchronous limit-cycle behavior and the synchronous balancing condition of system under the influence of the general bearing support. Here, solutions for rotor limit-cycle amplitudes and the corresponding whirl speeds are obtained via a harmonic balance approach. Furthermore, the limit-cycle stability is assessed via perturbation and Floquet analysis, and all the possible responses including undesirable coexistence for the bearing parameters and operating speeds have been thoroughly studied. It is found that, due to asymmetric behavior of bearing support, the multiple limit cycles are encountered in the range of supercritical speeds and more complicate coexistences are invited into the ABD–rotor system compared to the case with idealized symmetric bearing supports. The findings in this paper yield important insights for researchers wishing to utilize automatic balancing devices in more practical rotor systems mounted on a asymmetric general bearing support.