Method and system for integrated path planning and path tracking control of autonomous vehicle

A system for integrated path planning and path tracking control of an autonomous vehicle, comprising:

• a current-time parameter obtaining module, configured to obtain five input control variables and eleven system state variables of the autonomous vehicle at current time, wherein the five input control variables comprise a front wheel steering angle and four control moments at wheels;
• and the eleven system state variables comprise a lateral vehicle velocity, a yaw rate, four sideslip angles of the wheels, two relative velocities at the wheels, a horizontal coordinate of generalized vehicle coordinates, a vertical coordinate of the generalized vehicle coordinates, and a vehicle heading angle;
• a vehicle path planning-tracking integrated state model constructing module, configured to construct a vehicle path planning-tracking integrated state model according to the five input control variables and the eleven system state variables at the current time:
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• wherein, the front wheel steering angle and the four control moments at wheels are selected as a system control input u=[δ Tfl Tfr Trl Trr], and different control input combinations are adopted to achieve a same objective;
• system state variables are defined as x=[v r τf τr ur X Y ψ], including a lateral vehicle velocity v, a yaw rate r, wheel sideslip angles, relative velocities ur at wheels specifically including mapped velocities {dot over (u)}ij of four wheels, generalized vehicle coordinates (X,Y), and a vehicle heading angle Ψ, wherein τf is a front wheel sideslip angle, and τr is a rear wheel sideslip angle;
• an elliptical envelop curve determining module, configured to envelop external contours of two autonomous vehicles using elliptical envelope curves to determine elliptical vehicle envelope curves of the two autonomous vehicles, respectively;
• a time to collision (TTC) determining module, configured to determine a TTC between an autonomous vehicle and a vehicle having a distance smaller than a distance threshold away from the autonomous vehicle according to the elliptical vehicle envelope curves and driving states of the vehicles;
• an objective function establishing module, configured to establish an objective function of a model prediction controller (MPC) according to the vehicle path planning-tracking integrated state model, wherein, a system MPC planning-controller is built according to vehicle dynamic characteristics including various vehicle parameters in the vehicle dynamic model, and an objective function of the MPC planning-controller is defined as follows:
• J=½[Q·exp(−sp)+(up−up−)TH(up−up−)+upTMup], p=1, . . . Np
• wherein sp represents a distance between a position of a center-of-mass of a present vehicle and that of a neighboring vehicle at time p, uP is a control input at time p, uP is a control input at previous time, Q, H and M represent a relative distance between vehicles, smoothness of the control input and a weight matrix of the control input, respectively, and Np is a predicted time domain length of the MPC;
• and
• a next-time input control variable determining module, configured to solve the objective function based on the TTC and determine input control variables at next time, wherein the input control variables are used to increase a distance between the two autonomous vehicles with minimum control energy to control a motion trajectory of the autonomous vehicle in real time.