What adjustments are needed to PID controller settings when switching from a light to a heavier payload?

When switching from a light to a heavier payload on a UAV, adjustments to the PID (Proportional, Integral, Derivative) controller settings are generally necessary to maintain stable and responsive flight. The addition of a heavier payload increases the UAV's inertia and reduces its responsiveness to control inputs. Inertia is the resistance of an object to changes in its motion. To compensate for this, the PID gains typically need to be adjusted as follows. The Proportional (P) gain often needs to be increased. The P gain provides immediate corrective action based on the current error. With a heavier payload, the UAV will respond more slowly to control commands, so a higher P gain is needed to provide a stronger corrective force to achieve the same level of responsiveness. However, increasing the P gain too much can lead to oscillations, so it should be adjusted carefully. The Integral (I) gain may also need to be increased. The I gain addresses accumulated error over time, helping to eliminate steady-state errors. With a heavier payload, the UAV might struggle to maintain its desired altitude or position, especially in the presence of disturbances like wind. A higher I gain can help the system overcome this and achieve the desired state. However, as with the P gain, increasing the I gain too much can cause instability or windup. The Derivative (D) gain may need to be decreased, or remain unchanged. The D gain adds damping to the system, preventing oscillations. With a heavier payload, the system is already more sluggish, so less damping may be required. In some cases, the D gain may need to be slightly decreased to avoid making the system too slow to respond. However, the optimal D gain setting will depend on the specific characteristics of the UAV and payload. The amount of adjustment needed for each gain will depend on the magnitude of the payload increase and the specific characteristics of the UAV. It's important to adjust the gains iteratively, monitoring the UAV's performance after each adjustment to ensure stability and responsiveness. For example, if a UAV starts to oscillate after adding a heavier payload, the D gain should be increased to provide more damping or the P gain should be reduced. If it struggles to maintain altitude, the I gain should be increased. Autotune features, where available in flight controllers, can assist with this process.