"fixed axis" is correct and usable in written English.
You can use it when referring to a line or reference point that is not changing or moving, such as a line of rotation or a point of reference. For example, "The robot's arm is attached to a fixed axis."
According to Euler's rotation theorem, any 3-D displacement of a rigid body whereby one point of the rigid body remains fixed, can be expressed as a single rotation around a fixed axis crossing the fixed point of the rigid body.
Figure 21: Rotation around a fixed axis.
The measured variables were compared with that at fixed axis.
Because of Hyperion's shape and eccentric orbit, it does not maintain a stable rotation about a fixed axis.
The rotating element of a centrifuge is usually driven about a fixed axis by an electric motor, or by an air turbine in some high-speed machines, and is known as a rotor, bowl, or drum.
The propulsor pitched about a fixed axis at its quarter chord, with a six-axis load cell measuring the forces and torques on the shaft.
Planetary gearboxes significantly differ from fixed-axis gearboxes and exhibit unique behaviors, which invalidate fault diagnosis methods working well for fixed-axis gearboxes.
Condition monitoring and fault diagnosis of epicyclic gearboxes using vibration signals are not as straightforward as that of fixed-axis gearboxes since epicyclic gearboxes behave quite differently from fixed-axis gearboxes in many aspects, like spectral structures.
The structures of a planetary gearbox as well as a fixed-axis one are briefly introduced and contrasted.
Much work has been done for condition monitoring and fault diagnosis of fixed-axis gearboxes, while studies on planetary gearboxes are not that many.
Therefore, planet bearing vibrations are highly intricate and their fault characteristics are completely different from those of fixed-axis case, making planet bearing fault diagnosis a difficult topic.
