我是通过sudo apt-get install carla-simulator=0.9.13命令安装的Carla。

Carla版本是0.9.13
ROS2版本是Galactic

在使用./run_exploration_mode_ros2.sh命令进行仿真时，没有NPC车辆。

1、如果是通过源码下载的，直接运行：

cd $CARLA_ROOT
cd PythonAPI/examples/
python3 tm_spawn_npc.py -n 20
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运行指令会生成20辆车，最大限制为200。

2、如果是通过apt下载的，需要添加py文件：

cd $CARLA_ROOT
sudo gedit PythonAPI/examples/tm_spawn_npc.py  
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将以下内容复制到文件中:

#!/usr/bin/env python

# Copyright (c) 2019 Computer Vision Center (CVC) at the Universitat Autonoma de
# Barcelona (UAB).
#
# This work is licensed under the terms of the MIT license.
# For a copy, see .

"""Spawn NPCs into the simulation using the Traffic Manager interface"""

import time
import random
import glob
import argparse
import logging
import sys
import os
try:
    sys.path.append(glob.glob('../carla/dist/carla-*%d.%d-%s.egg' % (
        sys.version_info.major,
        sys.version_info.minor,
        'win-amd64' if os.name == 'nt' else 'linux-x86_64'))[0])
except IndexError:
    pass
import carla

def main():
    argparser = argparse.ArgumentParser(
        description=__doc__)
    argparser.add_argument(
        '--host',
        metavar='H',
        default='127.0.0.1',
        help='IP of the host server (default: 127.0.0.1)')
    argparser.add_argument(
        '-p', '--port',
        metavar='P',
        default=2000,
        type=int,
        help='TCP port to listen to (default: 2000)')
    argparser.add_argument(
        '-n', '--number-of-vehicles',
        metavar='N',
        default=10,
        type=int,
        help='number of vehicles (default: 10)')
    argparser.add_argument(
        '-w', '--number-of-walkers',
        metavar='W',
        default=50,
        type=int,
        help='number of walkers (default: 50)')
    argparser.add_argument(
        '--safe',
        action='store_true',
        help='avoid spawning vehicles prone to accidents')
    argparser.add_argument(
        '--filterv',
        metavar='PATTERN',
        default='vehicle.*',
        help='vehicles filter (default: "vehicle.*")')
    argparser.add_argument(
        '--filterw',
        metavar='PATTERN',
        default='walker.pedestrian.*',
        help='pedestrians filter (default: "walker.pedestrian.*")')

    args = argparser.parse_args()

    logging.basicConfig(format='%(levelname)s: %(message)s', level=logging.INFO)

    vehicles_list = []
    walkers_list = []
    all_id = []
    client = carla.Client(args.host, args.port)
    client.set_timeout(2.0)

    try:
        world = client.get_world()
        blueprints = world.get_blueprint_library().filter(args.filterv)
        blueprintsWalkers = world.get_blueprint_library().filter(args.filterw)

        if args.safe:
            blueprints = [x for x in blueprints if int(x.get_attribute('number_of_wheels')) == 4]
            blueprints = [x for x in blueprints if not x.id.endswith('isetta')]
            blueprints = [x for x in blueprints if not x.id.endswith('carlacola')]

        spawn_points = world.get_map().get_spawn_points()
        number_of_spawn_points = len(spawn_points)

        if args.number_of_vehicles < number_of_spawn_points:
            random.shuffle(spawn_points)
        elif args.number_of_vehicles > number_of_spawn_points:
            msg = 'Requested %d vehicles, but could only find %d spawn points'
            logging.warning(msg, args.number_of_vehicles, number_of_spawn_points)
            args.number_of_vehicles = number_of_spawn_points

        # @todo cannot import these directly.
        SpawnActor = carla.command.SpawnActor

        # --------------
        # Spawn vehicles
        # --------------

        for n, transform in enumerate(spawn_points):
            if n >= args.number_of_vehicles:
                break
            blueprint = random.choice(blueprints)
            if blueprint.has_attribute('color'):
                color = random.choice(blueprint.get_attribute('color').recommended_values)
                blueprint.set_attribute('color', color)
            if blueprint.has_attribute('driver_id'):
                driver_id = random.choice(blueprint.get_attribute('driver_id').recommended_values)
                blueprint.set_attribute('driver_id', driver_id)
            blueprint.set_attribute('role_name', 'autopilot')
            vehicle = world.try_spawn_actor(blueprint, transform)
            vehicles_list.append(vehicle)

        # -------------
        # Spawn Walkers
        # -------------
        # some settings
        percentagePedestriansRunning = 0.0      # how many pedestrians will run
        percentagePedestriansCrossing = 0.0     # how many pedestrians will walk through the road
        # 1. take all the random locations to spawn
        spawn_points = []
        for i in range(args.number_of_walkers):
            spawn_point = carla.Transform()
            loc = world.get_random_location_from_navigation()
            if (loc != None):
                spawn_point.location = loc
                spawn_points.append(spawn_point)
        # 2. we spawn the walker object
        batch = []
        walker_speed = []
        for spawn_point in spawn_points:
            walker_bp = random.choice(blueprintsWalkers)
            # set as not invencible
            if walker_bp.has_attribute('is_invincible'):
                walker_bp.set_attribute('is_invincible', 'false')
            # set the max speed
            if walker_bp.has_attribute('speed'):
                if (random.random() > percentagePedestriansRunning):
                    # walking
                    walker_speed.append(walker_bp.get_attribute('speed').recommended_values[1])
                else:
                    # running
                    walker_speed.append(walker_bp.get_attribute('speed').recommended_values[2])
            else:
                print("Walker has no speed")
                walker_speed.append(0.0)
            batch.append(SpawnActor(walker_bp, spawn_point))
        results = client.apply_batch_sync(batch, True)
        walker_speed2 = []
        for i in range(len(results)):
            if results[i].error:
                logging.error(results[i].error)
            else:
                walkers_list.append({"id": results[i].actor_id})
                walker_speed2.append(walker_speed[i])
        walker_speed = walker_speed2
        # 3. we spawn the walker controller
        batch = []
        walker_controller_bp = world.get_blueprint_library().find('controller.ai.walker')
        for i in range(len(walkers_list)):
            batch.append(SpawnActor(walker_controller_bp, carla.Transform(), walkers_list[i]["id"]))
        results = client.apply_batch_sync(batch, True)
        for i in range(len(results)):
            if results[i].error:
                logging.error(results[i].error)
            else:
                walkers_list[i]["con"] = results[i].actor_id
        # 4. we put altogether the walkers and controllers id to get the objects from their id
        for i in range(len(walkers_list)):
            all_id.append(walkers_list[i]["con"])
            all_id.append(walkers_list[i]["id"])
        all_actors = world.get_actors(all_id)

        # wait for a tick to ensure client receives the last transform of the walkers we have just created
        world.wait_for_tick()

        # 5. initialize each controller and set target to walk to (list is [controler, actor, controller, actor ...])
        # set how many pedestrians can cross the road
        world.set_pedestrians_cross_factor(percentagePedestriansCrossing)
        for i in range(0, len(all_id), 2):
            # start walker
            all_actors[i].start()
            # set walk to random point
            all_actors[i].go_to_location(world.get_random_location_from_navigation())
            # max speed
            all_actors[i].set_max_speed(float(walker_speed[int(i/2)]))

        print('Spawned %d vehicles and %d walkers, press Ctrl+C to exit.' % (len(vehicles_list), len(walkers_list)))

        time.sleep(1)

        for v in vehicles_list:
            v.set_autopilot(True)

        while True:
            time.sleep(1)

    finally:

        print('Destroying %d vehicles.
' % len(vehicles_list))
        client.apply_batch([carla.command.DestroyActor(x) for x in vehicles_list])

        # stop walker controllers (list is [controller, actor, controller, actor ...])
        for i in range(0, len(all_id), 2):
            all_actors[i].stop()

        print('
destroying %d walkers' % len(walkers_list))
        client.apply_batch([carla.command.DestroyActor(x) for x in all_id])


if __name__ == '__main__':

    try:
        main()
    except KeyboardInterrupt:
        pass
    finally:
        print('Done.
')
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运行指令：

cd $CARLA_ROOT
cd PythonAPI/examples/
python3 tm_spawn_npc.py -n 20
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