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”.

Warning 本指南适用于高级用户/专家。

Tip 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。

Tip 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.

Tip 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.