reward_updated.py

def reward_function(params):
    '''
    Example of penalize steering, which helps mitigate zig-zag behaviors
    '''
    
    # Read input parameters
    distance_from_center = params['distance_from_center']
    track_width = params['track_width']
    steering = abs(params['steering_angle']) # Only need the absolute steering angle
    progress = abs(params['progress'])
    waypoints = params['waypoints']

    # Calculate 3 markers that are at varying distances away from the center line
    marker_1 = 0.1 * track_width
    marker_2 = 0.25 * track_width
    marker_3 = 0.5 * track_width

    ## Give higher reward if the agent is closer to center line and vice versa
    # future improvement: add an exception to the rule where the car can reach near the edge
    # at certain waypoints (corners) but reduces speed so that it doesn't cross border
    if distance_from_center <= marker_1:
        reward = 1
    elif distance_from_center <= marker_2:
        reward = 0.5
    elif distance_from_center <= marker_3:
        reward = 0.1
    else:
        reward = 1e-3  # likely crashed/ close to off track
        
    # penalize for getting off centre during big turns   
    for i, point in enumerate(waypoints):
        waypoint = (point[2], point[3])

    # Steering penality threshold, change the number based on your action space setting
    ABS_STEERING_THRESHOLD = 15

    # Penalize reward if the agent is steering too much
    if steering > ABS_STEERING_THRESHOLD:
        reward *= 0.5
        
    # reward for finishing the track
    if progress == 100:
        reward = 1000
        
    # print waypoints for local plotting
    print(*waypoints, sep=',')
    
    return float(reward)