steadiness

(control systems) Freedom of a robot arm or end effector from high-frequency vibrations and jerks.
(meteorology) persistence

The ability to maintain the body, or a part of the body, in a fixed position, or the ability to perform a smooth movement without any deviations from the desired course. Steadiness is adversely affected by muscle tremor and usually decreases as the strength of muscle contractions increase. It is an important component of skills requiring very controlled, steady movements (such as pistol marksmanship and snooker). The anxiety caused by competition sometimes results in the loss of steadiness, and a few marksmen and snooker players have resorted to taking drugs, such as beta-blockers, to reduce muscle tension.

noun

Reliability in withstanding pressure, force, or stress: fastness, firmness, hardness, security, soundness, stability, stableness, strength, sturdiness, sureness. See better/worse, change/persist, continue/stop/pause.

The ability to maintain the body or limb in a fixed position, or to execute smooth movements without any deviation from the desired direction. Steadiness is affected by muscle tremors and muscle tension. Generally, as the force of a muscle action increases, steadiness decreases. Steadiness is an important ability in target sports such as pistol marksmanship. See also beta blockers.

The noun has 2 meanings:

Meaning #1: the quality of being steady or securely and immovably fixed in place
  Synonym: firmness
  Antonym: unsteadiness (meaning #1)

Meaning #2: the quality of being steady--regular and unvarying
  Antonym: unsteadiness (meaning #2)