Benzothiazol-β-amino esters, acted as β-amino acids derivatives, perform excellent bioactivity in antibacterial and antivirus. To gain highly and purely optical single enantioisomer of benzothiazol-β-amino esters with simple organocatalyst, recently, the development for a classic Mannich reaction of diethyl malonate (Nu) with benzothiazol imine (EI) in the presence of cinchona alkaloid derivatives as organocatalyst has been made. The study for mechanism of applying unmodified cinchona alkaloid-chiral quinidine as potent organocatalyst to asymmetric Mannich reaction of benzothiazol-β-amino esters plays a vital role in asymmetric synthesis. In this work, the mechanism for Mannich reaction of benzothiazol-β-amino esters catalyzed by simple chiral quinidine organocatalyst was investigated through a combination of experiment with theoretical approaches (DFT). All geometry structures of reactants (Nu and EI), intermediates and product were optimized completely with the moderate approach M06-2X/6-311G (d,p) basis set in the gas phase. Afterward, the effect of solvent for DCM was took into consideration, and CPCM was used as polarization continuum model. Frequency calculations were performed at the same level of 6-311G (d,p) basis set as the geometry optimizations to confirm stable transition state (TS), which was verified further by means of IR vibrating frequency calculations (zero and only one imaginary frequency respectively). As comparison of (R)TS pathway with (S)TS pathway in potential energy profile, it enables to elaborate that (S)TS pathway executes to afford unique enatioisomer (S). The calculating results indicate that (1) Active sites of quinidine have been confirmed, that are 9-hydroxyl and tertiary amine; (2) The product exhibits S enantiomer as major configuration; (3) Moreover, the results of DFT calculation indicated that the stereo selectivity of the reaction could be improved by lower reaction temperature. The lower temperature is, the more distereoselectivity is upgraded. The calculation demonstrated that all of results are able to be in agreement with experimental data that β-amino acid esters derivatives carrying S as major configuration could arrive to range of 81%～95% ee.

Aiming at the issues of slow convergence, phase delay, and chattering in the sensorless vector control system of permanent magnet synchronous motor (PMSM) controlled by sliding mode observer (SMO), a fuzzy adaptive super-twisting (ST) SMO sensorless control algorithm is proposed. The fuzzy adaptive algorithm is used to estimate the uncertain boundary and adaptively adjust sliding mode gain, which is used in the ST algorithm to accelerate the convergence speed of sliding mode gain, and eliminate the system delay caused by phase locked loop and phase compensation, and improve the estimation accuracy of speed and rotor position. In this algorithm, the sigmoid function is used instead of the signum function in the traditional SMO to suppress system chattering. Lyapunov stability theorem is used to obtain the stable conditions of position and speed observer at motoring mode. The saturated ST-SMO algorithm is verified by Matlab/Simulink. The simulation results show that compared with the traditional SMO, the fuzzy ST-SMO algorithm proposed in this paper has faster convergence speed in the variable speed and the variable load of PMSM sensorless control system, which has significantly reduced chattering, obtained more accurate speed and rotor position and has better dynamic response and robustness.Recently, the application of permanent magnet synchronous machine (PMSM) is increasing rapidly in aerospace, electric vehicles, intelligent machinery, medical equipment, household appliances, or other fields due to its small size, lightweight, fast response, high efficiency, and wide speed range. However, its drive performance is susceptible to system parameters and load disturbances because of strong coupling, multivariable, nonlinear, and time-varying characteristics. At present, both fieldoriented control (FOC) and direct torque control (DTC) of PMSM can achieve higher dynamic performance; FOC is very sensitive to parameter changes, resulting in poor robustness and anti-interference of the system; DTC torque response is fast, but the torque ripple is significant during startup or low-speed oper-This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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An optimized sliding-mode observer control algorithm for permanent magnet synchronous motor (PMSM) is proposed to solve the problems in the conventional sliding-mode observer control algorithms (e.g., system chattering and phase delay). The proposed algorithm adopts a new piecewise function as a switching function to reduce system chattering. The low pass filter in the conventional sliding-mode observer is substituted with a complex coefficient filter in the proposed algorithm to solve the phase delay caused by the low pass filter. Moreover, the counter emf back obtained using the filtering of the complex coefficient filter is reintroduced into the sliding-mode observer to decrease the sliding-mode gain coefficient and reduce chattering in the system. the simulation results suggest that the proposed algorithm outperforms the conventional sliding-mode observer control algorithm in reducing chattering, increasing the convergence speed, reducing torque pulsation, increasing speed estimation accuracy and coping with speed and load mutation. JEL CLASSIFICATION Control engineering and robotics INTRODUCTIONPMSM has been extensively used in new energy vehicles for its rapid dynamic response, high torque density, high reliability and high efficiency [1,2]. Conventional PMSM for vehicles should acquire rotor position and magnetic field direction information in real time using a position sensor for the excellent driving performance of vehicles. However, a more significant rotor position error is generated, the control accuracy is reduced, and the torque output ability of the motor is weakened due to the zero-installation deviation of the position sensor and the distortion of the signal under complex operating conditions. Compared with the control system with a position sensor, the control system without a position sensor exhibits a wider speed range and a faster response speed, and it is capable of accurately acquiring rotor position information under harsh conditions (e.g., high temperature, high humidity, high pressure and strong magnetism), which leads to the maximal reliability of the electric drive system [3,4].

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