This paper presents a new systematic control and fail-safe design methodology for a four-corner closed-loop air suspension (CLAS) system. The proposed control algorithm consists of "system control" ...determining the target heights of the four corners of the vehicle body from driving conditions and from the driver's commands and "actuator control" achieving the target heights by controlling actuators. A sliding-mode control with phase-compensated feedback signal is applied as the main part of the system control. With the use of the sliding-mode control, the proposed system control can improve control accuracy and robustness against delays and disturbances as well as reduce the bounce oscillation of the vehicle body. This paper proposes a stepwise height control as the actuator control to overcome the limited power of the production CLAS system. The stepwise height control adjusts the front corners and the rear corners alternately until the four corners reach their corresponding target heights. A fail-safe algorithm (FA) is also proposed to provide the fault detection (FD), diagnosis, and management of the CLAS. In particular, a model-based FD method for the pressure sensor and the height sensors, which are critical components in the CLAS control system, has been proposed. A mathematical model of a CLAS system is developed for algorithm development and simulation. The proposed control algorithm and FA are verified by simulations and actual vehicle tests.
In this paper, we propose an analytic solution of state-constrained optimal tracking control problems for continuous-time linear time-invariant (CT-LTI) systems that are based on model-based ...prediction, the quadratic penalty function, and the variational approach. Model-based prediction is a concept taken from model-predictive control (MPC) and this is essential to change the direction of calculation for the solution from backward to forward. The quadratic penalty function plays an important role in deriving the analytic solution since it can transform the problem into a form that does not have inequality constraints. For computational convenience, we also propose a sub-optimal controller derived from the steady-state approximation of the analytic solution and show that the proposed controller satisfies the Lyapunov stability. The main advantage of the proposed controller is that it can be implemented in real time with a lower computational load compared to the implicit MPC. Finally, the simulation results for a DC motor servo system are shown and compared with the results of the direct multi-shooting method and the implicit MPC to verify the effectiveness of the proposed controller.
Transmission mounted electric drive type hybrid electric vehicles (HEVs) engage/disengage an engine clutch when EV↔HEV mode transitions occur. If this engine clutch is not adequately engaged or ...disengaged, driving power is not transmitted correctly. Therefore, it is required to verify whether engine clutch engagement/disengagement operates normally in the vehicle development process. This paper studied machine learning-based methods for detecting anomalies in the engine clutch engagement/disengagement process. We trained the various models based on multi-layer perceptron (MLP), long short-term memory (LSTM), convolutional neural network (CNN), and one-class support vector machine (one-class SVM) with the actual vehicle test data and compared their results. The test results showed the one-class SVM-based models have the highest anomaly detection performance. Additionally, we found that configuring the training architecture to determine normal/anomaly by data instance and conducting one-class classification is proper for detecting anomalies in the target data.
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•Anodized TiO2 nanotube was fabricated by controlling various voltage conditions.•The surface morphology and layer structures were investigated.•The “worm-like” surface structures on ...the nanotube layers were observed.•The voltage retention time induced the well-defined pore structure.
The morphology of TiO2 nanotube layers fabricated by electrochemical anodization in an ethylene glycol solution containing 0.5wt% NH4F was investigated as a function of several voltage conditions. The effects of voltage sweep rate, retention time, and initial sweep voltage on the surface pore structure and tube length were observed in detail by scanning electron microscopy (SEM). It was clearly seen that worm-like porous structures on the TiO2 nanotube layers were formed during the voltage sweep process. These porous structures changed to round-shaped individual pores with longer tubular layers under constant voltage conditions. The initial sweep voltage also affected the pore size, even when the same final voltage was applied. These findings indicate that voltage conditions are very important factors in determining the surface and layer structure of anodized TiO2 nanotubes.
This paper presents a practical approach using disturbance observer (DOB)-based longitudinal vehicle speed control in hybrid electric vehicles (HEVs). Speed control law is derived from a linearized ...nominal plant model obtained assuming that the vehicle is a lumped mass. The plant uncertainty and external disturbance are lumped into a disturbance term and compensated for by the DOB. In addition, a feedforward term is designed to improve tracking performance when a target trajectory varies during acceleration and deceleration. The proposed control algorithm is validated by simulations. Vehicle experiments are performed on C-segment HEVs and D-segment plug-in HEVs. The validation results from both simulations and vehicle experiments, comparing a proportional-integral (PI) controller, show that the proposed controller is more robust to model uncertainty and external disturbance.
This paper presents a practical approach designing a traction controller based on disturbance observer (DOB) in hybrid electric vehicles (HEVs). To conduct the traction control of HEVs, the proposed ...control scheme estimates disturbances in a specific frequency range caused by wheel-slips and reduces driving force in accordance with the estimated disturbance. A band pass filter is employed to the DOB to extract the disturbance in a specific frequency range causing wheel slip. In addition, a proportional-integral (PI) type regulator is applied to effectively reject the disturbances. To validate the proposed control algorithm, actual vehicle tests are performed using a C-segment HEV sport utility vehicle (SUV). The test results show that the proposed control algorithm achieved more enhanced energy efficiency as well as better ride comfort with maximizing traction force than the conventional control algorithm.
This paper presents a practical approach to developing a speed limiter using a disturbance observer (DOB) and a speed observer. A nominal plant model is designed assuming that the vehicle is a lumped ...mass. The plant uncertainty and external disturbance are lumped into a disturbance term and compensated for by the DOB. With the contribution of the DOB, the proposed controller can reduce overshoot and minimize steady-state error without feedforward and integrator control. In addition, the speed observer is also designed to reduce the overshoot due to noise such as offset, lag, and communication delay between the display speed and wheel speed, because the proposed controller operates according to the display speed. The proposed controller was validated by vehicle experiments performed on a C-segment hybrid electric vehicle (HEV) and achieved superior performance compared to conventional controllers.
This paper proposes a DC motor current control algorithm using a proportional-integral linear quadratic tracking (LQT) controller with a disturbance observer for the electronic stability control ...(ESC) brake system. Previously researched algorithms related to current control using disturbance rejection are robust control, adaptive control, LQT, or proportional-integral disturbance observer (PI-DOB); each of them has both advantages and disadvantages. The proposed algorithm uses a disturbance observer in order to improve disturbance rejection performance while avoiding the drawbacks of high gain property. Additionally, the proposed algorithm adds integral control in order to improve performance in the low frequency bands. In order to assess the performance of the proposed algorithm, simulations and experiments are performed in the time and frequency domains to compare the proposed algorithm with different algorithms which are actually implemented into the ESC. The proposed algorithm shows good characteristics near the cut-off frequency, which can be confirmed clearly by the time domain results.
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