Vehicle path tracking by integrated chassis control

The control problem of trajectory based path following for passenger vehicles is studied. Comprehensive nonlinear vehicle model is utilized for simulation vehicle response during various maneuvers in MATLAB/Simulink. In order to follow desired path, a driver model is developed to enhance closed loop driver/vehicle model. Then, linear quadratic regulator(LQR) controller is developed which regulates direct yaw moment and corrective steering angle on wheels. Particle swam optimization(PSO) method is utilized to optimize the LQR controller for various dynamic conditions. Simulation results indicate that, over various maneuvers, side slip angle and lateral acceleration can be reduced by 10% and 15%, respectively, which sustain the vehicle stable. Also, anti-lock brake system is designed for longitudinal dynamics of vehicle to achieve desired slip during braking and accelerating. Proposed comprehensive controller demonstrates that vehicle steerability can increase by about 15% during severe braking by preventing wheel from locking and reducing stopping distance.

Electrons dynamics control by shaping femtosecond laser pulses in micro/nanofabrication: modeling, method, measurement and application

During femtosecond laser fabrication,photons are mainly absorbed by electrons,and the subsequent energy transfer from electrons to ions is of picosecond order.Hence,lattice motion is negligible within the femtosecond pulse duration,whereas femtosecond photon-electron interactions dominate the entire fabrication process.Therefore,femtosecond laser fabrication must be improved by controlling localized transient electron dynamics,which poses a challenge for measuring and controlling at the electron level during fabrication processes.Pump-probe spectroscopy presents a viable solution,which can be used to observe electron dynamics during a chemical reaction.In fact,femtosecond pulse durations are shorter than many physical/chemical characteristic times,which permits manipulating,adjusting,or interfering with electron dynamics.Hence,we proposed to control localized transient electron dynamics by temporally or spatially shaping femtosecond pulses,and further to modify localized transient materials properties,and then to adjust material phase change,and eventually to implement a novel fabrication method.This review covers our progresses over the past decade regarding electrons dynamics control(EDC)by shaping femtosecond laser pulses in micro/nanomanufacturing:(1)Theoretical models were developed to prove EDC feasibility and reveal its mechanisms;(2)on the basis of the theoretical predictions,many experiments are conducted to validate our EDC-based femtosecond laser fabrication method.Seven examples are reported,which proves that the proposed method can significantly improve fabrication precision,quality,throughput and repeatability and effectively control micro/nanoscale structures;(3)a multiscale measurement system was proposed and developed to study the fundamentals of EDC from the femtosecond scale to the nanosecond scale and to the millisecond scale;and(4)As an example of practical applications,our method was employed to fabricate some key structures in one of the 16 Chinese National S&T Major Projects,for which electron dynamics were measured using our multiscale measurement system.