基于大疆MSDK实现的无人机视觉引导自适应降落功能

基于大疆MSDK实现的无人机视觉引导自适应降落功能

概述

最初需求：想要无人机在执行完航线任务后，一键落到一个指定的位置，简化人工控制。

实现一套完整的无人机自主降落功能,通过虚拟摇杆控制使无人机飞向指定位置，再利用视觉识别引导无人机精确降落到具体位置。本文中采用自适应降落策略,根据高度动态调整精度要求和下降速度,以实现安全、精确的降落。

核心点:

• 虚拟摇杆导航替代FlyTo功能
• 双轴(X/Y)位置偏移实时调整
• 高度自适应降落策略
• 视觉识别引导定位
• 智能避障管理

系统架构

整体流程

技术实现思路

第一步:让无人机飞到目标位置?

问题分析

遥控器控制的无人机在执行完航线任务之后，飞到给定降落点（汽车或其他载具上）。最初的想法是使用DJI SDK提供的FlyTo功能,直接指定目标GPS坐标让无人机飞过去。但在实际测试中，发现部分机型（如M3E）并不支持FlyTo功能。

机型是否支持FlyTo功能参考文档：https://developer.dji.com/doc/mobile-sdk-tutorial/cn/tutorials/intelligent-flight.html

解决方案:虚拟摇杆导航

既然FlyTo功能不可用,那就用虚拟摇杆功能进行模拟。

思路:

1. 计算当前位置到目标位置的方位角(bearing)
2. 将方位角转换为速度分量(南北/东西)
3. 持续发送虚拟摇杆指令,让无人机朝目标飞行
4. 实时监测距离,接近目标时停止

方位角计算:

/* by 01022.hk - online tools website : 01022.hk/zh/browserinfo.html */ private fun calculateBearing(latA: Double, lonA: Double, latB: Double, lonB: Double): Double { val lat1 = Math.toRadians(latA) val lat2 = Math.toRadians(latB) val dLon = Math.toRadians(lonB - lonA) val y = Math.sin(dLon) * Math.cos(lat2) val x = Math.cos(lat1) * Math.sin(lat2) - Math.sin(lat1) * Math.cos(lat2) * Math.cos(dLon) var bearing = Math.toDegrees(Math.atan2(y, x)) bearing = (bearing + 360) % 360 // 归一化到0-360度 return bearing // 0°=正北, 90°=正东, 180°=正南, 270°=正西 }

速度分量计算:

/* by 01022.hk - online tools website : 01022.hk/zh/browserinfo.html */ val bearing = calculateBearing(currentLat, currentLon, targetLat, targetLon) val bearingRad = Math.toRadians(bearing) // 使用GROUND坐标系(地面坐标系) val navParam = VirtualStickFlightControlParam().apply { rollPitchCoordinateSystem = FlightCoordinateSystem.GROUND verticalControlMode = VerticalControlMode.POSITION yawControlMode = YawControlMode.ANGLE rollPitchControlMode = RollPitchControlMode.VELOCITY // 将速度分解为南北和东西分量 pitch = NAVIGATION_SPEED * Math.cos(bearingRad) // 南北分量(5m/s) roll = NAVIGATION_SPEED * Math.sin(bearingRad) // 东西分量(5m/s) yaw = bearing // 让机头指向目标 verticalThrottle = targetAlt }

• GROUND坐标系是绝对方向,不受无人机朝向影响
• pitch控制南北,roll控制东西。

虚拟摇杆参数含义：https://developer.dji.com/doc/mobile-sdk-tutorial/cn/basic-introduction/basic-concepts/flight-controller.html#虚拟摇杆

第二步:判断何时到达目标点上方附近

持续监测距离

每100ms检查一次当前位置与目标的距离，距离小于预期值ARRIVAL_THRESHOLD,就认为无人机已到达目标点上方附近，停止导航，开始降落:

val navTask = object : Runnable { override fun run() { val currentLoc = getAircraftLocation() val remainingDistance = calculateDistance( currentLoc.latitude, currentLoc.longitude, targetLat, targetLon ) if (remainingDistance < ARRIVAL_THRESHOLD) { // 10米内 // 到达目标,停止导航,开始降落 isNavigating = false startDynamicAdjustment() } else { // 继续飞行 sendNavigationCommand() virtualStickHandler?.postDelayed(this, 100) } } }

第三步:精确降落到指定点

无人机虽然到了目标附近(10米内),但有以下问题：

1. GPS精度有限(±3米),不够精确。
2. 风力影响,有时候受风的影响，无人机会偏离。

解决方案:视觉识别+位置调整

工作原理:

1. 无人机摄像头识别地面的特定图像(如二维码、标记点)
2. 视觉算法计算偏移量(X轴左右,Y轴前后,Z轴距图像距离)
3. 将偏移量传给无人机
4. 无人机调整位置,边降落边对准

数据结构:

private var xOffset: Double = 0.0 // X轴偏移(米),正=右,负=左 private var yOffset: Double = 0.0 // Y轴偏移(米),正=前,负=后 private var zDistance: Double = 0.0 // Z轴距离(米),距降落点高度

外部接口:

// 视觉识别系统调用这些方法更新偏移量(~1Hz) fun setXOffset(offset: Double) { xOffset = offset } fun setYOffset(offset: Double) { yOffset = offset } fun setZDistance(distance: Double) { zDistance = distance }

采用自适应策略，一边降落一遍调整

关键点:
在不同的高度，我们允许的偏移量阈值不同的，高度较高的时候，偏移量就算比较大也可以下降，随着高度降低，我们允许的偏移量阈值会不断缩小（要求越来越向中间对齐）

真实偏移超出偏移量阈值的2倍就停止下降，只进行对齐调整；
真实偏移超出偏移量的1倍，就以0.1m/s的慢速一边降落一边调整；
在偏移量范围内，且高度> 20m，以0.5m/s的速度快速下降；
在偏移量范围内，且高度在5m-20m之间，以0.2m/s的速度下降；
在偏移量范围内，且高度< 5m，以0.2m/s速度下降；

实现:

// 1. 根据高度动态计算允许的误差 private fun getOffsetThreshold(altitude: Double): Double { return when { altitude > 50.0 -> 1.0 // 高空:允许1米偏移误差 altitude > 20.0 -> 0.5 // 中空:允许0.5米偏移误差 altitude > 5.0 -> 0.3 // 低空:允许0.3米偏移误差 else -> 0.2 // 极低空:要求0.2米精度 } } // 2. 根据高度和偏移量动态计算下降速度 private fun getDescentSpeed(altitude: Double, xOffset: Double, yOffset: Double): Double { val threshold = getOffsetThreshold(altitude) return when { xOffset > threshold * 2 || yOffset > threshold * 2 -> 0.0 // 偏移太大:停止下降 xOffset > threshold || yOffset > threshold -> 0.1 // 偏移较大:慢降 altitude > 20.0 -> 0.5 // 中高空:快降 altitude > 5.0 -> 0.2 // 低空:慢降 else -> 0.2 // 极低空:极慢降 } }

控制逻辑:

第四步:处理避障，降落后停桨。

问题:下视避障会阻止降落

无人机的下视避障系统会将地面识别为障碍物,在接近地面时自动停止下降，我们在高度为5m的时候关闭下视避障，落到地面后调用KeyStartAutoLanding进行停桨。
参考文档：https://sdk-forum.dji.net/hc/zh-cn/articles/14578693771033-如何使用虚拟摇杆降落

低空时关闭下视避障

var downwardObstacleDisabled = false //确保关闭下视避障操作只成功执行一次 // 高度<5m时关闭下视避障 if (currentAltitude <= 5.0 && !downwardObstacleDisabled) { downwardObstacleDisabled = true setObstacleAvoidanceEnable(false, PerceptionDirection.DOWNWARD) } //关闭下视避障调用方法 private fun setObstacleAvoidanceEnable(enabled: Boolean,direction: PerceptionDirection){ if (direction == null) { Log.e("Perception", "方向参数为空，无法设置避障") return } PerceptionManager.getInstance().setObstacleAvoidanceEnabled( //调用大疆MSDK方法关闭下视避障 enabled, direction, object : CommonCallbacks.CompletionCallback { override fun onSuccess() { toastResult?.postValue(DJIToastResult.success( "成功设置【${direction.name}】方向的避障为：${if (enabled) "开启" else "关闭"}") ) Log.i( "Perception", "成功设置【${direction.name}】方向的避障为：${if (enabled) "开启" else "关闭"}" ) } override fun onFailure(error: IDJIError) { downwardObstacleDisabled = false toastResult?.postValue(DJIToastResult.failed( "设置【${direction.name}】方向的避障失败：$error" )) Log.e( "Perception", "设置【${direction.name}】方向的避障失败：$error" ) } } ) }

第五步:降落循环完整逻辑

private fun startDynamicAdjustment() { isAdjusting = true virtualStickHandler = Handler(Looper.getMainLooper()) val adjustTask = object : Runnable { override fun run() { if (!isAdjusting) return // 1. 获取当前状态 val currentAltitude = FlightControllerKey.KeyAltitude.create().get(0.0) val currentXOffsetAbs = Math.abs(xOffset) val currentYOffsetAbs = Math.abs(yOffset) // 2. 检查是否着陆 if (currentAltitude <= 0.1) { stopLanding() return } // 3. 低空时关闭下视避障 if (currentAltitude <= 5.0 && !downwardObstacleDisabled) { downwardObstacleDisabled = true setObstacleAvoidanceEnable(false, PerceptionDirection.DOWNWARD) } // 4. 计算自适应参数 val offsetThreshold = getOffsetThreshold(currentAltitude) val descentSpeed = getDescentSpeed(currentAltitude, currentXOffsetAbs, currentYOffsetAbs) // 5. 构建虚拟摇杆指令 val adjustParam = VirtualStickFlightControlParam().apply { rollPitchCoordinateSystem = FlightCoordinateSystem.BODY verticalControlMode = VerticalControlMode.VELOCITY rollPitchControlMode = RollPitchControlMode.VELOCITY // 水平调整 roll = if (currentXOffsetAbs > offsetThreshold) { if (xOffset > 0) ADJUSTMENT_SPEED else -ADJUSTMENT_SPEED } else 0.0 pitch = if (currentYOffsetAbs > offsetThreshold) { if (yOffset > 0) ADJUSTMENT_SPEED else -ADJUSTMENT_SPEED } else 0.0 // 垂直下降 verticalThrottle = -descentSpeed } // 6. 发送指令 VirtualStickManager.getInstance().sendVirtualStickAdvancedParam(adjustParam) // 7. 100ms后再次执行(10Hz) virtualStickHandler?.postDelayed(this, 100) } } virtualStickHandler?.post(adjustTask) }

以上，就实现了一整套视觉引导的自适应降落方案

安全注意事项

WARNING

1. 必须在空旷、安全环境测试
2. 建议先用DJI模拟器测试
3. 视觉识别必须持续更新(~1Hz)
4. 准备好随时手动接管

代码

/** * One-key return to vehicle function (using Virtual Stick instead of FlyTo) * 1. Get aircraft current location * 2. Calculate distance to vehicle using Haversine formula * 3. If distance > 500m, reject with error * 4. Use Virtual Stick to navigate to vehicle location * 5. Switch to precision adjustment when close enough */ fun returnToVehicle(callback: CommonCallbacks.CompletionCallback) { // Get aircraft current location val aircraftLocation = getAircraftLocation() if (aircraftLocation == null || !isLocationValid(aircraftLocation.latitude, aircraftLocation.longitude)) { callback.onFailure(DJICommonError.FACTORY.build("无法获取无人机位置信息")) return } // Vehicle coordinates (hardcoded for now, will be replaced with API later) // TODO: Replace with actual vehicle GPS coordinates from API val vehicleLatitude = 22.579 // Example coordinates val vehicleLongitude = 113.941 // Example coordinates // Calculate distance using Haversine formula val distance = calculateDistance( aircraftLocation.latitude, aircraftLocation.longitude, vehicleLatitude, vehicleLongitude ) // Distance validation: reject if > 500m if (distance > 500) { callback.onFailure(DJICommonError.FACTORY.build( "距离过远: ${String.format("%.2f", distance)}m, 超出 500m 限制" )) return } // Start virtual stick navigation to vehicle location toastResult?.postValue(DJIToastResult.success("开始飞向车辆位置")) //TODO 这个targetAlt需要后期经过计算算出来。 navigateToTarget(vehicleLatitude, vehicleLongitude, 100.0, callback) } /** * Navigate to target location using Virtual Stick */ private fun navigateToTarget( targetLat: Double, targetLon: Double, targetAlt: Double, callback: CommonCallbacks.CompletionCallback ) { VirtualStickManager.getInstance().enableVirtualStick(object : CommonCallbacks.CompletionCallback { override fun onSuccess() { VirtualStickManager.getInstance().setVirtualStickAdvancedModeEnabled(true) isNavigating = true startNavigation(targetLat, targetLon, targetAlt, callback) } override fun onFailure(error: IDJIError) { callback.onFailure(error) } }) } /** * Start navigation loop using Virtual Stick */ private fun startNavigation( targetLat: Double, targetLon: Double, targetAlt: Double, callback: CommonCallbacks.CompletionCallback ) { virtualStickHandler = Handler(Looper.getMainLooper()) val navTask = object : Runnable { override fun run() { if (!isNavigating) { return } val currentLoc = getAircraftLocation() if (currentLoc == null) { virtualStickHandler?.postDelayed(this, 100) return } // Calculate remaining distance val remainingDistance = calculateDistance( currentLoc.latitude, currentLoc.longitude, targetLat, targetLon ) println("targetLat:"+targetLat+" targetLon:"+targetLon+" currentLoc.latitude:"+currentLoc.latitude+" currentLoc.longitude:"+currentLoc.longitude+" remainingDistance:"+remainingDistance) // Check if arrived if (remainingDistance < ARRIVAL_THRESHOLD) { // Arrived at target, stop navigation isNavigating = false virtualStickHandler?.removeCallbacksAndMessages(null) callback.onSuccess() toastResult?.postValue(DJIToastResult.success("已到达车辆位置,开始精确定位")) //开始调节云台角度,俯仰角为-90°，旋转时间1s startGimbalAngleRotation(GimbalAngleRotationMode.ABSOLUTE_ANGLE,-90.0,0.0,0.0,1.0) // Start precision adjustment startDynamicAdjustment() } else { // Continue navigation val bearing = calculateBearing( currentLoc.latitude, currentLoc.longitude, targetLat, targetLon ) val navParam = VirtualStickFlightControlParam().apply { rollPitchCoordinateSystem = FlightCoordinateSystem.GROUND // Use ground coordinate system verticalControlMode = VerticalControlMode.POSITION yawControlMode = YawControlMode.ANGLE rollPitchControlMode = RollPitchControlMode.VELOCITY // Calculate velocity components based on bearing val bearingRad = Math.toRadians(bearing) pitch = NAVIGATION_SPEED * Math.sin(bearingRad) // North-South component roll = NAVIGATION_SPEED * Math.cos(bearingRad) // East-West component yaw = bearing // Point towards target verticalThrottle = targetAlt // Target altitude } VirtualStickManager.getInstance().sendVirtualStickAdvancedParam(navParam) virtualStickHandler?.postDelayed(this, 100) } } } virtualStickHandler?.post(navTask) } fun startGimbalAngleRotation(mode: GimbalAngleRotationMode,pitch: Double,yaw: Double,roll: Double,duration: Double){ val rotation = GimbalAngleRotation().apply { setMode(mode) setPitch(pitch) setYaw(yaw) setRoll(roll) setDuration(duration) } KeyManager.getInstance().performAction( KeyTools.createKey(GimbalKey.KeyRotateByAngle), rotation, object: CommonCallbacks.CompletionCallbackWithParam<EmptyMsg>{ override fun onSuccess(result: EmptyMsg?) { toastResult?.postValue(DJIToastResult.success("云台旋转成功")) Log.i("Gimbal","云台旋转成功：yaw:${rotation.yaw},pitch:${rotation.pitch},roll:${rotation.roll}") } override fun onFailure(error: IDJIError) { toastResult?.postValue(DJIToastResult.failed("云台旋转失败,$error")) Log.e("Gimbal","云台旋转失败，$error") } } ) } /** * Start dynamic position adjustment loop with adaptive descent * Adjusts position while descending, with stricter requirements at lower altitudes */ private fun startDynamicAdjustment() { isAdjusting = true virtualStickHandler = Handler(Looper.getMainLooper()) // Send adjustment commands at 10Hz val adjustTask = object : Runnable { override fun run() { if (!isAdjusting) { return } // TODO 获取脚本检测出的z轴距离 val currentAltitude = FlightControllerKey.KeyAltitude.create().get(0.0) val currentXOffsetAbs = Math.abs(xOffset) val currentYOffsetAbs = Math.abs(yOffset) //关闭降落保护，下视避障失效 if(currentAltitude <= 5 && !downwardObstacleDisabled){ downwardObstacleDisabled = true setObstacleAvoidanceEnable(false, PerceptionDirection.DOWNWARD) } // 检查是否落地 if (currentAltitude <= 0.1) { stopLanding() return } // Get adaptive thresholds based on altitude val offsetThreshold = getOffsetThreshold(currentAltitude) val descentSpeed = getDescentSpeed(currentAltitude, currentXOffsetAbs,currentYOffsetAbs) // Log for debugging println("自动调整 - 高度:%.2fm, x偏移:%.2fm,y偏移:%.2fm, 阈值:%.2fm, 下降速度:%.2fm/s".format( currentAltitude, currentXOffsetAbs,currentYOffsetAbs,offsetThreshold, descentSpeed )) // Calculate adjustment parameters val adjustParam = VirtualStickFlightControlParam().apply { rollPitchCoordinateSystem = FlightCoordinateSystem.BODY verticalControlMode = VerticalControlMode.VELOCITY yawControlMode = YawControlMode.ANGULAR_VELOCITY rollPitchControlMode = RollPitchControlMode.ANGLE // Calculate roll value based on offset // Positive offset (need to move forward) -> positive roll // Negative offset (need to move backward) -> negative roll if (currentXOffsetAbs > offsetThreshold) { // Need adjustment roll = if (xOffset > 0) ADJUSTMENT_SPEED else -ADJUSTMENT_SPEED } else { // Within threshold, no adjustment needed roll = 0.0 } if (currentYOffsetAbs > offsetThreshold) { pitch = if(yOffset > 0) ADJUSTMENT_SPEED else -ADJUSTMENT_SPEED } else { pitch = 0.0 } yaw = 0.0 verticalThrottle = -descentSpeed // Descend at adaptive speed } VirtualStickManager.getInstance().sendVirtualStickAdvancedParam(adjustParam) virtualStickHandler?.postDelayed(this, 100) } } virtualStickHandler?.post(adjustTask) toastResult?.postValue(DJIToastResult.success("开始动态位置调整")) } /** * Stop landing and cleanup */ private fun stopLanding() { virtualStickHandler?.removeCallbacksAndMessages(null) //调用KeyStartAutoLanding进行停桨 FlightControllerKey.KeyStartAutoLanding.create().action({ toastResult?.postValue(DJIToastResult.success("桨叶动力关闭")) Log.i("stopLanding","桨叶动力关闭成功") },{ toastResult?.postValue(DJIToastResult.failed("桨叶动力关闭失败")) Log.i("stopLanding","桨叶动力关闭失败！！") }) cleanupVirtualStick() toastResult?.postValue(DJIToastResult.success("降落完成")) } /** * Get offset threshold based on current altitude * Higher altitude allows larger offset, lower altitude requires stricter precision */ private fun getOffsetThreshold(altitude: Double): Double { return when { altitude > HIGH_ALTITUDE -> 1.0 // High altitude: allow 1m offset altitude > MID_ALTITUDE -> 0.5 // Mid altitude: allow 0.5m offset altitude > LOW_ALTITUDE -> 0.4 // Low altitude: allow 0.3m offset else -> 0.3 // Very low altitude: require 0.2m precision } } /** * Get descent speed based on current altitude and offset * Larger offset or lower altitude results in slower descent */ private fun getDescentSpeed(altitude: Double, xOffset: Double,yOffset: Double): Double { val threshold = getOffsetThreshold(altitude) return when { xOffset > threshold * 2 || yOffset > threshold * 2 -> 0.0 // Offset too large: stop descending xOffset > threshold || yOffset > threshold -> 0.1 // Offset large: slow descent altitude > MID_ALTITUDE -> 0.5 // Mid-high altitude: fast descent altitude > LOW_ALTITUDE -> 0.2 // Low altitude: slow descent else -> 0.1 // Very low altitude: very slow descent } }