Search

A general predictive controller based on the subspace model identification method is proposed for vehicle stabilization. Traditional predictive controllers are always developed based on the principle model of vehicles, which inevitably suffers from parameter uncertainty and poor adaptability. In contrast to that, the proposed subspace-based general predictive controller is realized by a data-driven process and presents good adaptability in vehicle stability control. Inspired by subspace-based predictor construction, the keys of the predictive controller are as follows: (1) system model identification according to the model structure of the control object by input and output data; (2) output prediction of the system by the identified model; and (3) optimal control law designed by combining the linear–quadratic–Gaussian index with the predictive output. The main problem in the controller development lies in the recursive estimation of relevant matrices, which is limited by the subspace model identification theory. The implementation of the vector autoregressive with exogenous input model and the propagator method in subspace identification algorithm effectively solves the problem of estimation accuracy and calculation efficiency. Combined with a linear–quadratic–Gaussian index function, the predictive law for vehicle stability control is derived in detail. Finally, based on the vehicle model validated by standard road test, the effectiveness and robustness of the predictive controller are proved through the numerical simulations of various maneuvers under different road adhesive conditions. [ABSTRACT FROM AUTHOR]

In this article, a robust H ∞ observer-based static state-feedback controller is designed for the path following of autonomous ground vehicles. The Takagi–Sugeno fuzzy modeling technique is used for modeling of vehicle dynamics with varying longitudinal velocity first. Then considering the high cost of direct lateral velocity measurement, an observer is designed to estimate the value of lateral velocity. Meanwhile, a robust controller is proposed to deal with the parameter uncertainties and external disturbances simultaneously, including the variation of the tire-cornering stiffness of both front and rear tires. Afterward, the condition of designing such an observer-based controller is transformed into the feasible problem of linear matrix inequalities. Numerical simulations using a high-fidelity and full vehicle model are performed based on a Carsim–Simulink joint platform. Simulation results under different conditions and comparison with other controller show that the proposed controller is effective irrespective of the variation in the road condition, the change in the vehicle longitudinal velocity and the external disturbances. [ABSTRACT FROM AUTHOR]

It is an effective method to explore the full spectrum responsive photocatalysts for enhancing their photocatalytic activity. Herein, we have combined the upconversion phosphor with semiconductor to design the full‐spectrum light responsive photocatalyst. A facile approach has been developed for synthesis of NaYF4:Yb,Tm@TiO2 core‐shell structured composite. The morphologies, crystal phases, chemical compositions, optical performance, and photoelectric properties were characterized. Based on SEM and TEM observation, the formation mechanism of NaYF4:Yb,Tm@TiO2 composite was discussed in detail. The results of photodegradation experiment showed that 22% of Rhodamine B dye in the solution was photodegradated by NaYF4:Yb,Tm@TiO2 composite under NIR light irradiation within 150 min, suggesting that the NaYF4:Yb,Tm@TiO2 core‐shell structured composite displayed photocatalytic activity under NIR light irradiation. Furthermore, the photocatalytic ability of NaYF4:Yb,Tm@TiO2 is obvious superior to that of TiO2 under the full‐spectrum light irradiation. [ABSTRACT FROM AUTHOR]

Non-linear system control has always been a difficult point for vehicle stabilization. To improve the vehicle handling performance, a comprehensive active-steering control method is proposed and derived. Different from traditional strategy, this new controller is based on a piecewise tyre modelling ideology combined with feedback linearization controlling method. In the linear region of wheel–terrain contact, vehicle dynamic system turns to be a linear system, an optimal control is designed for the sake of rapid response in tracking desired values. In the non-linear region, where the controlling difficulty always lies in, the tyre lateral force is described by a new polynomial formula model, which is simpler than magic formula model and more accurate than linear model. This new tyre modelling ideology ensures the feasibility of feedback linearization method in non-linear system control. To verify the proposed controller, a numerical seven-degrees-of-freedom vehicle model is built and validated by standard input simulation. Then, simulation under limit conditions, including high friction case and low friction case, are conducted and results are presented and discussed. Compared with optimal controller and free-control method, comprehensive controller has a much more desirable applicability in both cases and greatly improves the vehicle handling performance. [ABSTRACT FROM AUTHOR]

NaYF 4 :Yb,Tm upconversion nanocrystals with hexagonal structure possess excellent photoluminescence emission characteristics. Under near infrared (NIR) light irradiation, the Yb 3+ ions act as sensitizers to absorb the NIR light and transform NIR light into ultraviolet (UV) and visible (Vis) light continuously. Hybrid NIR-activated photocatalysts can be fabricated by combining upconversion nanocrystals with various semiconductor nanocrystals. In this paper, NaYF 4 :Yb,Tm micro-rods were hydrothermally synthesized with oleic acid as capping ligand. The NaYF 4 :Yb,Tm@CdS composite was fabricated by in situ generation of CdS nanoclusters on the surface of NaYF 4 :Yb,Tm micro-rods. The morphologies and structures of NaY 4 :Yb,Tm and NaYF 4 :Yb,Tm@CdS were characterized by XRD, SEM, TEM, XPS, UV-Vis and PL spectroscopy. The results of photocatalytic experiments indicated that the NaYF 4 :Yb,Tm@CdS composite displayed photocatalytic activity under NIR irradiation. In comparison with pure CdS, the photocatalytic ability of NaYF 4 :Yb,Tm@CdS composite under Vis-NIR irradiation was obviously enhanced. 82% of RhB was degraded by NaYF 4 :Yb,Tm@CdS catalyst within 75 min under Vis-NIR irradiation, which was more effective than pure CdS (65% degradation of RhB)., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)