GLOBAL OPTIMAL PATH PLANNING OF AN AUTONOMOUS VEHICLE FOR OVERTAKING A MOVING OBSTACLE

Abstract

IN THIS PAPER, THE GLOBAL OPTIMAL PATH PLANNING OF AN AUTONOMOUS VEHICLE FOR OVERTAKING A MOVING OBSTACLE IS PROPOSED. IN THIS STUDY, THE AUTONOMOUS VEHICLE OVERTAKES A MOVING VEHICLE BY PERFORMING A DOUBLE LANE-CHANGE MANEUVER AFTER DETECTING IT IN A PROPER DISTANCE AHEAD. THE OPTIMAL PATH OF VEHICLE FOR PERFORMING THE LANE-CHANGE MANEUVER IS GENERATED BY A PATH PLANNING PROGRAM IN WHICH THE SUM OF LATERAL DEVIATION OF THE VEHICLE FROM A REFERENCE PATH AND THE RATE OF STEERING ANGLE BECOME MINIMUM WHILE THE LATERAL ACCELERATION OF VEHICLE DOES NOT EXCEED A SAFE LIMIT VALUE. A NONLINEAR OPTIMAL CONTROL THEORY WITH THE LATERAL VEHICLE DYNAMICS EQUATIONS AND INEQUALITY CONSTRAINT OF LATERAL ACCELERATION ARE USED TO GENERATE THE PATH. THE INDIRECT APPROACH FOR SOLVING THE OPTIMAL CONTROL PROBLEM IS USED BY APPLYING THE CALCULUS OF VARIATION AND THE PONTRYAGINÂS MINIMUM PRINCIPLE TO OBTAIN FIRST-ORDER NECESSARY CONDITIONS FOR OPTIMALITY. THE OPTIMAL PATH IS GENERATED AS A GLOBAL OPTIMAL SOLUTION AND CAN BE USED AS THE BENCHMARK OF THE PATH GENERATED BY THE LOCAL MOTION PLANNING OF AUTONOMOUS VEHICLES. A FULL NONLINEAR VEHICLE MODEL IN CARSIM SOFTWARE IS USED FOR PATH FOLLOWING SIMULATION BY IMPORTING PATH DATA FROM THE MATLAB CODE. THE SIMULATION RESULTS SHOW THAT THE GENERATED PATH FOR THE AUTONOMOUS VEHICLE SATISFIES ALL VEHICLE DYNAMICS CONSTRAINTS AND HENCE IS A SUITABLE OVERTAKING PATH FOR THE FOLLOWING VEHICLE.