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313 lines
29 KiB
Markdown
313 lines
29 KiB
Markdown
# Offboard 模式
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<img src="../../assets/site/position_fixed.svg" title="Position fix required (e.g. GPS)" width="30px" />
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飞行器根据飞行控制栈外部（如机载计算机）提供的设定值控制位置、速度、加速度、姿态以及推力/力矩。
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The setpoints may be provided using MAVLink (or a MAVLink API such as [MAVSDK](https://mavsdk.mavlink.io/)) or by [ROS 2](../ros2/index.md).
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PX4 requires that the external controller provides a continuous 2Hz "proof of life" signal, by streaming any of the supported MAVLink setpoint messages or the ROS 2 [OffboardControlMode](../msg_docs/OffboardControlMode.md) message.
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PX4只有在收到该种信号超过1秒后才有效，如果该种信号停止飞行控制栈将重新获得控制权（脱离Offboard模式）。
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::: info
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- 此模式需要位置或位/姿信息 - 例如 GPS、光流、视觉惯性里程计、mocap 等。
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- RC control is disabled except to change modes (you can also fly without any manual controller at all by setting the parameter [COM_RC_IN_MODE](../advanced_config/parameter_reference.md#COM_RC_IN_MODE) to 4: Stick input disabled).
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- The vehicle must be already be receiving a stream of MAVLink setpoint messages or ROS 2 [OffboardControlMode](../msg_docs/OffboardControlMode.md) messages before arming in offboard mode or switching to offboard mode when flying.
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- The vehicle will exit offboard mode if MAVLink setpoint messages or `OffboardControlMode` are not received at a rate of > 2Hz.
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- 并非所有 MAVLink 支持的坐标系和字段值都被设定值消息和飞行器支持。
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Read the sections below _carefully_ to ensure only supported values are used.
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:::
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## 描述
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Offboard模式通过设置位置、速度、加速、姿态、姿态角速率或力/扭矩设定值来控制飞行器的位置和姿态。
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PX4 must receive a stream of MAVLink setpoint messages or the ROS 2 [OffboardControlMode](../msg_docs/OffboardControlMode.md) at 2 Hz as proof that the external controller is healthy.
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该消息必须持续发送1秒以上PX4才能在Offboard模式下解锁或在飞行中切换至Offboard模式。
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If the rate falls below 2Hz while under external control PX4 will switch out of offboard mode after a timeout ([COM_OF_LOSS_T](#COM_OF_LOSS_T)), and attempt to land or perform some other failsafe action.
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The action depends on whether or not RC control is available, and is defined in the parameter [COM_OBL_RC_ACT](#COM_OBL_RC_ACT).
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当使用 MAVLink 时，设定值消息既传达了外部控制器"正常运行"的信号也传达了设定值本身。
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Offboard模式下要保持位置，飞行器必须接收到一个包含当前位置设定值的消息指令。
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When using ROS 2 the proof that the external source is alive is provided by a stream of [OffboardControlMode](../msg_docs/OffboardControlMode.md) messages, while the actual setpoint is provided by publishing to one of the setpoint uORB topics, such as [TrajectorySetpoint](../msg_docs/TrajectorySetpoint.md).
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In order to hold position in this case the vehicle must receive a stream of `OffboardControlMode` but would only need the `TrajectorySetpoint` once.
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请注意，Offboard模式只支持比较有限的 MAVLink 指令和消息。
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其他操作如起飞、降落、返航，最好使用适当的模式来处理。
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像上传、下载任务这样的操作可以在任何模式下执行。
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## ROS 2 消息
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以下 ROS 2 消息及其特定字段和字段值在特定的框架下是允许的。
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In addition to providing heartbeat functionality, `OffboardControlMode` has two other main purposes:
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1. Controls the level of the [PX4 control architecture](../flight_stack/controller_diagrams.md) at which offboard setpoints must be injected, and disables the bypassed controllers.
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2. 确定需要哪种有效估计(位置或速度)，以及应该使用哪种设定值消息。
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The `OffboardControlMode` message is defined as shown.
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```sh
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# Off-board control mode
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uint64 timestamp # time since system start (microseconds)
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bool position
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bool velocity
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bool acceleration
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bool attitude
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bool body_rate
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bool thrust_and_torque
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bool direct_actuator
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```
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:::warning
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The following list shows the `OffboardControlMode` options for copter, fixed-wing, and VTOL.
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For rovers see the [rover section](#rover).
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:::
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The fields are ordered in terms of priority such that `position` takes precedence over `velocity` and later fields, `velocity` takes precedence over `acceleration`, and so on.
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第一个非零字段(从上到下) 定义了Offboard模式所需的有效估计以及可用的设定值消息。
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For example, if the `acceleration` field is the first non-zero value, then PX4 requires a valid `velocity estimate`, and the setpoint must be specified using the `TrajectorySetpoint` message.
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| 期望控制对象 | 位置 | 速度 | 加速度 | 姿态 | 姿态角速率 | 执行器字段 | 直接给电机 | 所需状态估计 | 所需消息 |
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| ------------------------------ | --------------------------- | --------------------------- | --------------------------- | --------------------------- | --------------------------- | --------------------------- | --------------------------- | ------ | ------------------------------------------------------------------------------------------------------------------------------- |
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| 位置 (NED) | ✓ | - | - | - | - | - | - | 位置 | [TrajectorySetpoint](../msg_docs/TrajectorySetpoint.md) |
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| 速度 (NED) | ✗ | ✓ | - | - | - | - | - | 速度 | [TrajectorySetpoint](../msg_docs/TrajectorySetpoint.md) |
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| 加速度（NED） | ✗ | ✗ | ✓ | - | - | - | - | 速度 | [TrajectorySetpoint](../msg_docs/TrajectorySetpoint.md) |
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| 姿态(FRD) | ✗ | ✗ | ✗ | ✓ | - | - | - | 无 | [VehicleAttitudeSetpoint](../msg_docs/VehicleAttitudeSetpoint.md) |
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| 体轴角速率 (FRD) | ✗ | ✗ | ✗ | ✗ | ✓ | - | - | 无 | [VehicleRatesSetpoint](../msg_docs/VehicleRatesSetpoint.md) |
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| 推力和力矩(FRD) | ✗ | ✗ | ✗ | ✗ | ✗ | ✓ | - | 无 | [VehicleThrustSetpoint](../msg_docs/VehicleThrustSetpoint.md) and [VehicleTorqueSetpoint](../msg_docs/VehicleTorqueSetpoint.md) |
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| 直接给电机和舵机 | ✗ | ✗ | ✗ | ✗ | ✗ | ✗ | ✓ | 无 | [ActuatorMotors](../msg_docs/ActuatorMotors.md) and [ActuatorServos](../msg_docs/ActuatorServos.md) |
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where ✓ means that the bit is set, ✘ means that the bit is not set and `-` means that the bit is value is irrelevant.
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:::info
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Before using offboard mode with ROS 2, please spend a few minutes understanding the different [frame conventions](../ros2/user_guide.md#ros-2-px4-frame-conventions) that PX4 and ROS 2 use.
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:::
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### 旋翼机
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- [px4_msgs::msg::TrajectorySetpoint](https://github.com/PX4/PX4-Autopilot/blob/main/msg/versioned/TrajectorySetpoint.msg)
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- 支持以下输入组合：
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- Position setpoint (`position` different from `NaN`). Non-`NaN` values of velocity and acceleration are used as feedforward terms for the inner loop controllers.
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- Velocity setpoint (`velocity` different from `NaN` and `position` set to `NaN`). Non-`NaN` values acceleration are used as feedforward terms for the inner loop controllers.
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- Acceleration setpoint (`acceleration` different from `NaN` and `position` and `velocity` set to `NaN`)
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- All values are interpreted in NED (Nord, East, Down) coordinate system and the units are `[m]`, `[m/s]` and `[m/s^2]` for position, velocity and acceleration, respectively.
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- [px4_msgs::msg::VehicleAttitudeSetpoint](https://github.com/PX4/PX4-Autopilot/blob/main/msg/versioned/VehicleAttitudeSetpoint.msg)
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- 支持以下输入组合：
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- quaternion `q_d` + thrust setpoint `thrust_body`.
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Non-`NaN` values of `yaw_sp_move_rate` are used as feedforward terms expressed in Earth frame and in `[rad/s]`.
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- 姿态四元数表示无人机机体坐标系FRD(前、右、下) 与NED坐标系之间的旋转。
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这个推力是在无人机体轴FRD坐标系下，并归一化为 \[-1, 1\] 。
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- [px4_msgs::msg::VehicleRatesSetpoint](https://github.com/PX4/PX4-Autopilot/blob/main/msg/versioned/VehicleRatesSetpoint.msg)
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- 支持以下输入组合：
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- `roll`, `pitch`, `yaw` and `thrust_body`.
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- 所有值都表示在无人机体轴FRD坐标系下。
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The rates are in `[rad/s]` while thrust_body is normalized in `[-1, 1]`.
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### 无人车
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Rover modules must set the control mode using `OffboardControlMode` and use the appropriate messages to configure the corresponding setpoints.
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The approach is similar to other vehicle types, but the allowed control mode combinations and setpoints are different:
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| Category | 用法 | Setpoints |
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| -------------------------------------------------------------------------------------- | ----------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| (Recommended) [Rover Setpoints](#rover-setpoints) | General rover control | [RoverPositionSetpoint](../msg_docs/RoverPositionSetpoint.md), [RoverSpeedSetpoint](../msg_docs/RoverSpeedSetpoint.md), [RoverAttitudeSetpoint](../msg_docs/RoverAttitudeSetpoint.md), [RoverRateSetpoint](../msg_docs/RoverRateSetpoint.md), [RoverThrottleSetpoint](../msg_docs/RoverThrottleSetpoint.md), [RoverSteeringSetpoint](../msg_docs/RoverSteeringSetpoint.md) |
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| [Actuator Setpoints](#actuator-setpoints) | Direct actuator control | [ActuatorMotors](../msg_docs/ActuatorMotors.md), [ActuatorServos](../msg_docs/ActuatorServos.md) |
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| (Deprecated) [Trajectory Setpoint](#deprecated-trajectory-setpoint) | General vehicle control | [TrajectorySetpoint](../msg_docs/TrajectorySetpoint.md) |
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#### Rover 设置点
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滚动模块使用层次结构来传播设置点：
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The "highest" setpoint that is provided will be used within the PX4 rover modules to generate the setpoints that are below it (overriding them!).
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这个层次结构有提供有效控制输入的明确规则：
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- Provide a position setpoint **or**
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- “左”上的设置点之一(速度 **或** 节点) **和** “右”上的设置点之一(态度、速率 **或** 节点)。
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所有“左”和“右”设置点的组合都是有效的。
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The following are all valid setpoint combinations and their respective control flags that must be set through [OffboardControlMode](../msg_docs/OffboardControlMode.md) (set all others to _false_).
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Additionally, for some combinations we require certain setpoints to be published with `NAN` values so that the setpoints of interest are not overridden by the rover module (due to the hierarchy above).
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✓ are the relevant setpoints we publish, and ✗ are the setpoint that need to be published with `NAN` values.
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| Setpoint Combination | Control Flag | [RoverPositionSetpoint](../msg_docs/RoverPositionSetpoint.md) | [RoverSpeedSetpoint](../msg_docs/RoverSpeedSetpoint.md) | [RoverThrottleSetpoint](../msg_docs/RoverThrottleSetpoint.md) | [RoverAttitudeSetpoint](../msg_docs/RoverAttitudeSetpoint.md) | [RoverRateSetpoint](../msg_docs/RoverRateSetpoint.md) | [RoverSteeringSetpoint](../msg_docs/RoverSteeringSetpoint.md) |
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| -------------------- | ----------------------------------------------------------- | ------------------------------------------------------------- | ------------------------------------------------------- | ------------------------------------------------------------- | ------------------------------------------------------------- | ----------------------------------------------------- | ------------------------------------------------------------- |
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| 安装位置 | 位置 | ✓ | | | | | |
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| Speed + Attitude | 速度 | | ✓ | | ✓ | | |
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| Speed + Rate | 速度 | | ✓ | | ✗ | ✓ | |
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| Speed + Steering | 速度 | | ✓ | | ✗ | ✗ | ✓ |
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| Throttle + Attitude | attitude | | | ✓ | ✓ | | |
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| Throttle + Rate | body_rate | | | ✓ | | ✓ | |
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| Throttle + Steering | thrust_and_torque | | | ✓ | | | ✓ |
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:::info
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If you intend to use the rover setpoints, we recommend using the [PX4 ROS 2 Interface Library](../ros2/px4_ros2_interface_lib.md) instead since it simplifies the publishing of these setpoints.
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:::
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#### Actuator Setpoints
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Instead of controlling the vehicle using position, speed, rate and other setpoints, you can directly control the motors and actuators using [ActuatorMotors](../msg_docs/ActuatorMotors.md) and [ActuatorServos](../msg_docs/ActuatorServos.md).
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In [OffboardControlMode](../msg_docs/OffboardControlMode.md) set `direct_actuator` to _true_ and all other flags to _false_.
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:::info
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This bypasses the rover modules including any limits on steering rates or accelerations and the inverse kinematics step.
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We recommend using [RoverSteeringSetpoint](../msg_docs/RoverSteeringSetpoint.md) and [RoverThrottleSetpoint](../msg_docs/RoverThrottleSetpoint.md) instead for low level control (see [Rover Setpoints](#rover-setpoints)).
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:::
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#### (Deprecated) Trajectory Setpoint
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:::warning
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The [Rover Setpoints](#rover-setpoints) are a replacement for the [TrajectorySetpoint](../msg_docs/TrajectorySetpoint.md) and we highly recommend using those instead as they have a well defined behaviour and offer more flexibility.
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:::
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The rover modules support the _position_, _velocity_ and _yaw_ fields of the [TrajectorySetpoint](../msg_docs/TrajectorySetpoint.md).
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However, only one of the fields is active at a time and is defined by the flags of [OffboardControlMode](../msg_docs/OffboardControlMode.md):
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| Control Mode Flag | Active Trajectory Setpoint Field |
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| ----------------- | -------------------------------- |
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| 位置 | 位置 |
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| 速度 | 速度 |
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| attitude | yaw |
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:::info
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Ackermann rovers do not support the yaw setpoint.
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:::
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### Generic Vehicle
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下面的offboard控制模式会绕过所有PX4内部的控制环，应当非常谨慎地使用。
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- [px4_msgs::msg::VehicleThrustSetpoint](https://github.com/PX4/PX4-Autopilot/blob/main/msg/VehicleThrustSetpoint.msg) + [px4_msgs::msg::VehicleTorqueSetpoint](https://github.com/PX4/PX4-Autopilot/blob/main/msg/VehicleTorqueSetpoint.msg)
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- 支持以下输入组合：
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- `xyz` for thrust and `xyz` for torque.
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- 所有值都在无人机体轴 FRD 坐标系中表示，并且归一化为\[-1, 1\]。
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- [px4_msgs::msg::ActuatorMotors](https://github.com/PX4/PX4-Autopilot/blob/main/msg/versioned/ActuatorMotors.msg) + [px4_msgs::msg::ActuatorServos](https://github.com/PX4/PX4-Autopilot/blob/main/msg/versioned/ActuatorServos.msg)
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- 直接控制电机输出和/或伺服系统（舵机）输出。
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- Currently works at lower level than then `control_allocator` module.
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Do not publish these messages when not in offboard mode.
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- All the values normalized in `[-1, 1]`.
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For outputs that do not support negative values, negative entries map to `NaN`.
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- `NaN` maps to disarmed.
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## MAVLink 消息
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下面的 MAVLink 消息及其特定字段和字段值在特定的帧下是允许的。
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### 直升机/垂直起降
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- [SET_POSITION_TARGET_LOCAL_NED](https://mavlink.io/en/messages/common.html#SET_POSITION_TARGET_LOCAL_NED)
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- The following input combinations are supported: <!-- https://github.com/PX4/PX4-Autopilot/blob/main/src/lib/FlightTasks/tasks/Offboard/FlightTaskOffboard.cpp#L166-L170 -->
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- Position setpoint (only `x`, `y`, `z`)
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- Velocity setpoint (only `vx`, `vy`, `vz`)
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- Acceleration setpoint (only `afx`, `afy`, `afz`)
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- Position setpoint **and** velocity setpoint (the velocity setpoint is used as feedforward; it is added to the output of the position controller and the result is used as the input to the velocity controller).
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- Position setpoint **and** velocity setpoint **and** acceleration (the velocity and the acceleration setpoints are used as feedforwards; the velocity setpoint is added to the output of the position controller and the result is used as the input to the velocity controller; the acceleration setpoint is added to the output of the velocity controller and the result used to compute the thrust vector).
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- PX4 supports the following `coordinate_frame` values (only): [MAV_FRAME_LOCAL_NED](https://mavlink.io/en/messages/common.html#MAV_FRAME_LOCAL_NED) and [MAV_FRAME_BODY_NED](https://mavlink.io/en/messages/common.html#MAV_FRAME_BODY_NED).
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- [SET_POSITION_TARGET_GLOBAL_INT](https://mavlink.io/en/messages/common.html#SET_POSITION_TARGET_GLOBAL_INT)
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- The following input combinations are supported: <!-- https://github.com/PX4/PX4-Autopilot/blob/main/src/lib/FlightTasks/tasks/Offboard/FlightTaskOffboard.cpp#L166-L170 -->
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- Position setpoint (only `lat_int`, `lon_int`, `alt`)
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- Velocity setpoint (only `vx`, `vy`, `vz`)
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- _Thrust_ setpoint (only `afx`, `afy`, `afz`)
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::: info
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Acceleration setpoint values are mapped to create a normalized thrust setpoint (i.e. acceleration setpoints are not "properly" supported).
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:::
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- Position setpoint **and** velocity setpoint (the velocity setpoint is used as feedforward; it is added to the output of the position controller and the result is used as the input to the velocity controller).
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- PX4 supports the following `coordinate_frame` values (only): [MAV_FRAME_GLOBAL](https://mavlink.io/en/messages/common.html#MAV_FRAME_GLOBAL).
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- [SET_ATTITUDE_TARGET](https://mavlink.io/en/messages/common.html#SET_ATTITUDE_TARGET)
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- 支持以下输入组合：
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- Attitude/orientation (`SET_ATTITUDE_TARGET.q`) with thrust setpoint (`SET_ATTITUDE_TARGET.thrust`).
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- Body rate (`SET_ATTITUDE_TARGET` `.body_roll_rate` ,`.body_pitch_rate`, `.body_yaw_rate`) with thrust setpoint (`SET_ATTITUDE_TARGET.thrust`).
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### Fixed-wing
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- [SET_POSITION_TARGET_LOCAL_NED](https://mavlink.io/en/messages/common.html#SET_POSITION_TARGET_LOCAL_NED)
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- The following input combinations are supported (via `type_mask`): <!-- https://github.com/PX4/PX4-Autopilot/blob/main/src/lib/FlightTasks/tasks/Offboard/FlightTaskOffboard.cpp#L166-L170 -->
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- Position setpoint (`x`, `y`, `z` only; velocity and acceleration setpoints are ignored).
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- Specify the _type_ of the setpoint in `type_mask` (if these bits are not set the vehicle will fly in a flower-like pattern):
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::: info
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Some of the _setpoint type_ values below are not part of the MAVLink standard for the `type_mask` field.
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:::
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值为：
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- 292：滑动设定值。
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这会将 TECS 配置为空速优先于高度，以便在没有推力时使无人机滑行（即控制俯仰以调节空速）。
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It is equivalent to setting `type_mask` as `POSITION_TARGET_TYPEMASK_Z_IGNORE`, `POSITION_TARGET_TYPEMASK_VZ_IGNORE`, `POSITION_TARGET_TYPEMASK_AZ_IGNORE`.
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- 4096：起飞设定值。
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- 8192：降落设定值。
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- 12288：悬停设定值（以设定值为中心绕圈飞行）。
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- 16384：空闲设定值（油门为0， 横滚 / 俯仰为0）。
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- PX4 supports the coordinate frames (`coordinate_frame` field): [MAV_FRAME_LOCAL_NED](https://mavlink.io/en/messages/common.html#MAV_FRAME_LOCAL_NED) and [MAV_FRAME_BODY_NED](https://mavlink.io/en/messages/common.html#MAV_FRAME_BODY_NED).
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- [SET_POSITION_TARGET_GLOBAL_INT](https://mavlink.io/en/messages/common.html#SET_POSITION_TARGET_GLOBAL_INT)
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- The following input combinations are supported (via `type_mask`): <!-- https://github.com/PX4/PX4-Autopilot/blob/main/src/lib/FlightTasks/tasks/Offboard/FlightTaskOffboard.cpp#L166-L170 -->
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- Position setpoint (only `lat_int`, `lon_int`, `alt`)
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- Specify the _type_ of the setpoint in `type_mask` (if these bits are not set the vehicle will fly in a flower-like pattern):
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::: info
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The _setpoint type_ values below are not part of the MAVLink standard for the `type_mask` field.
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:::
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值为：
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||
- 4096：起飞设定值。
|
||
- 8192：降落设定值。
|
||
- 12288：悬停设定值（以设定值为中心绕圈飞行）。
|
||
- 16384：空闲设定值（油门为0， 横滚 / 俯仰为0）。
|
||
|
||
- PX4 supports the following `coordinate_frame` values (only): [MAV_FRAME_GLOBAL](https://mavlink.io/en/messages/common.html#MAV_FRAME_GLOBAL).
|
||
|
||
- [SET_ATTITUDE_TARGET](https://mavlink.io/en/messages/common.html#SET_ATTITUDE_TARGET)
|
||
- 支持以下输入组合：
|
||
- Attitude/orientation (`SET_ATTITUDE_TARGET.q`) with thrust setpoint (`SET_ATTITUDE_TARGET.thrust`).
|
||
- Body rate (`SET_ATTITUDE_TARGET` `.body_roll_rate` ,`.body_pitch_rate`, `.body_yaw_rate`) with thrust setpoint (`SET_ATTITUDE_TARGET.thrust`).
|
||
|
||
### 无人车
|
||
|
||
Rover does not support a MAVLink offboard API (ROS2 is supported).
|
||
|
||
## Offboard参数
|
||
|
||
_Offboard mode_ is affected by the following parameters:
|
||
|
||
| 参数 | 描述 |
|
||
| ----------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
|
||
| <a id="COM_OF_LOSS_T"></a>[COM_OF_LOSS_T](../advanced_config/parameter_reference.md#COM_OF_LOSS_T) | Time-out (in seconds) to wait when offboard connection is lost before triggering offboard lost failsafe (`COM_OBL_RC_ACT`) |
|
||
| <a id="COM_OBL_RC_ACT"></a>[COM_OBL_RC_ACT](../advanced_config/parameter_reference.md#COM_OBL_RC_ACT) | Flight mode to switch to if offboard control is lost (Values are - `0`: _Position_, `1`: _Altitude_, `2`: _Manual_, `3`: \*Return, `4`: \*Land\*). |
|
||
| <a id="COM_RC_OVERRIDE"></a>[COM_RC_OVERRIDE](../advanced_config/parameter_reference.md#COM_RC_OVERRIDE) | Controls whether stick movement on a multicopter (or VTOL in MC mode) causes a mode change to [Position mode](../flight_modes_mc/position.md). 默认情况下未启用此功能。 |
|
||
| <a id="COM_RC_STICK_OV"></a>[COM_RC_STICK_OV](../advanced_config/parameter_reference.md#COM_RC_STICK_OV) | The amount of stick movement that causes a transition to [Position mode](../flight_modes_mc/position.md) (if [COM_RC_OVERRIDE](#COM_RC_OVERRIDE) is enabled). |
|
||
| <a id="COM_RCL_EXCEPT"></a>[COM_RCL_EXCEPT](../advanced_config/parameter_reference.md#COM_RCL_EXCEPT) | 该参数指定一种模式，在该模式下将忽略RC丢失及不会触发RC丢失的失效保护动作。 Set bit `2` to ignore RC loss in Offboard mode. |
|
||
|
||
## 开发者资源
|
||
|
||
Typically developers do not directly work at the MAVLink layer, but instead use a robotics API like [MAVSDK](https://mavsdk.mavlink.io/) or [ROS](https://www.ros.org/) (these provide a developer friendly API, and take care of managing and maintaining connections, sending messages and monitoring responses - the minutiae of working with _Offboard mode_ and MAVLink).
|
||
|
||
以下资源可能对开发者有用：
|
||
|
||
- [Offboard Control from Linux](../ros/offboard_control.md)
|
||
- [ROS/MAVROS Offboard Example (C++)](../ros/mavros_offboard_cpp.md)
|
||
- [ROS/MAVROS Offboard Example (Python)](../ros/mavros_offboard_python.md)
|