DroneKit教程（七）：遙控信道覆蓋

DroneKit教程（七）：遙控信道覆蓋

MAVLink支持一項有用卻又非常危險的功能：遙控信道覆蓋（Channel Override）。遙控信道覆蓋可以將任一至全部通道的遙控輸入信號改寫爲任意值。當前，DroneKit的開發者已經建議不再使用此功能。

在使用時，需要維持輸出值在上下限之間、飛控與指令發送端的連接穩定可靠、有完備的故障保護手段。遙控信道覆蓋可以用作虛擬搖桿操控、或者以最“直觀”的方式執行一些自動化任務。但是一般情況下，我們還是建議使用MAVLink指令。

預先準備

根據“使用從源碼編譯的SITL測試DroneKit代碼”中的要求，運行SITL和MAVProxy：

1. 打開Cygwin Terminal，依次輸入

   cd ~/ardupilot/ArduCopter/
   ./ArduCopter.elf --home -35,149,584,270 --model quad

2. 新開一個cmd，運行

   mavproxy.py --master tcp:127.0.0.1:5760 --sitl 127.0.0.1:5501 --out 127.0.0.1:14550 --out 127.0.0.1:14551

3. （可選）使用MissionPlanner地面站監控無人機的狀態。運行MissionPlanner地面站，右上角選擇UDP，點擊connect連接。端口填寫14550

在測試過程中，請保持SITL和MAVProxy運行。

編程示例

本示例改寫自DroneKit的官方示例。

#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""
© Copyright 2015-2016, 3D Robotics.
channel_overrides.py: 
Demonstrates how set and clear channel-override information.
# NOTE: 
Channel overrides (a.k.a "RC overrides") are highly discommended (they are primarily implemented 
for simulating user input and when implementing certain types of joystick control).
"""
from dronekit import connect

# 連接到SITL
connection_string = '127.0.0.1:14551'
print 'Connecting to vehicle on: %s' % connection_string
vehicle = connect(connection_string, wait_ready=True)


# 顯示全部通道的讀數
print "Read channels individually:"
print " Ch1: %s" % vehicle.channels['1']
print " Ch2: %s" % vehicle.channels['2']
print " Ch3: %s" % vehicle.channels['3']
print " Ch4: %s" % vehicle.channels['4']
print " Ch5: %s" % vehicle.channels['5']
print " Ch6: %s" % vehicle.channels['6']
print " Ch7: %s" % vehicle.channels['7']
print " Ch8: %s" % vehicle.channels['8']
print "Number of channels: %s" % len(vehicle.channels)


# 開始遙控信道覆蓋
print "\nChannel overrides: %s" % vehicle.channels.overrides

# 將通道2的值設置爲200（鍵值訪問）
print "Set Ch2 override to 200 (indexing syntax)"
vehicle.channels.overrides['2'] = 200
print " Channel overrides: %s" % vehicle.channels.overrides
print " Ch2 override: %s" % vehicle.channels.overrides['2']

# 將通道3的值設置爲300（字典訪問，同時會清除通道2的設置）
print "Set Ch3 override to 300 (dictionary syntax)"
vehicle.channels.overrides = {'3':300}
print " Channel overrides: %s" % vehicle.channels.overrides

# 分別設置通道1-8爲110-810（字典訪問）
print "Set Ch1-Ch8 overrides to 110-810 respectively"
vehicle.channels.overrides = {'1': 110, '2': 210,'3': 310,'4':4100, '5':510,'6':610,'7':710,'8':810}
print " Channel overrides: %s" % vehicle.channels.overrides 


# 清除2通道的信道覆蓋（通過鍵值將相應元素賦值None）
print "\nCancel Ch2 override (indexing syntax)"
vehicle.channels.overrides['2'] = None
print " Channel overrides: %s" % vehicle.channels.overrides 

# 清除3通道的信道覆蓋（使用del語句）
print "Clear Ch3 override (del syntax)"
del vehicle.channels.overrides['3']
print " Channel overrides: %s" % vehicle.channels.overrides 

# 清除全部的信道覆蓋（設置空字典）
print "Clear all overrides"
vehicle.channels.overrides = {}
print " Channel overrides: %s" % vehicle.channels.overrides 


# 關閉vehicle對象
print "\nClose vehicle object"
vehicle.close()

print("Completed")

讀取和設置信道

使用vehicle.channels讀取信道

vehicle.channels將返回一個字典元素，鍵值爲通道的序數。

# 獲取當前通道2的輸入值
vehicle.channels['2']

# 當前所有通道的輸入值
vehicle.channels

使用vehicle.channels.overrides覆蓋信道

vehicle.channels.overrides與vehicle.channels類似，也是一個字典。它將對其中存在的元素進行信道覆蓋，不存在的元素保留現有輸入。

# 覆蓋通道2的輸入值，設置爲500
vehicle.channels.overrides['2'] = 500

# 清除通道2的信道覆蓋
vehicle.channels.overrides['2'] = None
# 或
del vehicle.channels.overrides['2']

# 一次設置多個通道
vehicle.channels.overrides = {'1': 500, '2': 500, '3': 1000, '4': 500}

# 清除全部通道
vehicle.channels.overrides = {}
# 或
vehicle.channels.overrides = None

版本信息

1.0 20170916 initial commit

本作品採用知識共享署名-相同方式共享 3.0 未本地化版本許可協議進行許可。