Servo Endurance and Failure

The main steering servo that has been used in Voyager 2 has been the Hitec HS-322HD.

Several of these servos have been used in the life of the Voyager 2.

The original steering servo used in lake conditions, from 2016 was being retired in late 2019, prior to commencing ocean voyages, and stored away for possible use in less critical projects.

Hitec HS-322HD

A few years later in January 2023 this servo tested for its endurance by exercising without load until it failed.

It completed around 4 million movements before failure.

The failure occurred in the brushes of the DC motor .

The image below shows two motors from HS-322HD servos where the brushes had failed.

In both cases the filed brushes lead to a failure of FET drivers in the H-Bridge.

The brush housing on the left is from the motor tested to failure without load, to 4 million operations.

The one on the right failed at sea, leading to the stranding of the Voyager near Cape Schank in April 2024.

Failed DC Motor Brushes

Servo Driver board showing burnt-out FET drivers.

The steering servo on board Voyager for the 6th voyage in Bass Strait, failed in April 2024.

It failed after an estimated 280,000 operations. This is well short of the anticipated 4 million operations from the previous no load endurance testing.

The plan moving forward is to investigate the availability and suitability of servos that utilize brushless motors.

The Hitec HS-322HD has a toque rating of 3kg at 1cm.

The smallest brushless servos seem be rated at 20kg at 1cm.