Multicopter Setpoint Tuning (Trajectory Generator)

This document provides an overview of the multicopter tuning parameters that change the user experience: how fast the vehicle reacts to stick movements or direction changes in missions, the maximum allowed velocity, etc. (i.e. the parameters that affect the value of a desired setpoint rather than those that affect how well the vehicle tracks the setpoint). The algorithm that generates those setpoints is called a "trajectory generator".

本指南适用于高级用户/专家。

Follow the instructions in the Multicopter PID Tuning Guide before doing any of the tuning described here. Do not use these tuning parameters to fix bad tracking or vibration!

综述

P/PID控制器的输入是飞行器尝试跟踪的期望设定值PID调参 ("低级"调参) 的目标是减小设定值和估计值之间的误差。 较小的PID增益将导致飞行器的不稳定

传递给 P/PID 控制器的所需设定值本身是根据摇杆位置(在遥控模式下)或从任务指令的要求设定值计算的。 设定值(“更高级别”)调整用于指定所需设定值和所需设定值之间的映射。 较差的的设定值不会导致不稳定,但可能导致对设定值变化的响应速度变慢。

所要求的设定值可能会很快改变(例如, 如果用户一下子从零设置为到最大价值)。 如果缓慢调整相应的目标设定值, 飞行器的特性就会更好。

The setpoint-value tuning parameters can be split into two groups: tuning parameters for position mode and tuning parameters for mission mode. 某些参数将同时对两种模式产生影响。

Definitions

位置控制器 ( diagram here ) 由外环的 P 位置控制回路和内环的 PID 速度控制回路组成。 根据 飞行模式, 两个回路都是活动的, 或者只有速度控制回路是活动的。

对于本文档的其余部分, 位置控制 代表两个控制回路都有效的情况,而 速度控制 指的是仅使用速度控制回路的情况。

Implementations

Two different implementations are available for each mode and can be selected using the parameters MPC_POS_MODE and MPC_AUTO_MODE.

Click on the links below to learn more about those implementations and how to configure them:

  • Slew-rate (MPC_POS_MODE=1, MPC_POS_MODE=2, MPC_AUTO_MODE=0) - Used when quick response is more important than smooth motion (e.g.: inspection, aggressive flight with position hold, fast missions).

    • This is a simple implementation where the jerk and acceleration is limited using slew-rates.
    • In manual mode, it allows asymmetric profiles based on user intention (smooth acceleration and quick stop).
    • The jerk and acceleration limits are not hard constraints.
  • Jerk-limited (MPC_POS_MODE=3, MPC_AUTO_MODE=1) - Used when smooth motion is required (e.g.: filming, mapping, cargo).

    • Generates symmetric smooth S-curves where the jerk and acceleration limits are always guaranteed.

The jerk-limited (smooth) type is used by default for all frames in both manual and auto modes; this may not be suitable for vehicles/use-cases that require a faster response - e.g. racer quads.

© PX4 Dev Team. License: CC BY 4.0            Updated: 2019-11-12 03:58:31

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