Explain the term 'actuator efficiency.'

Actuator efficiency refers to how effectively an actuator converts hydraulic energy into mechanical work. This concept is crucial in understanding the performance of hydraulic systems, as it directly influences how much of the energy supplied by the hydraulic fluid is utilized to produce the desired movement or force. High efficiency means that a greater portion of the hydraulic energy is transformed into useful mechanical output, while lower efficiency indicates that more energy is wasted, often as heat due to friction and other losses within the system.

In a hydraulic actuator, efficiency is influenced by factors such as friction, leakage, and the design of the components involved. Engineers aim to maximize this efficiency to ensure that systems operate economically and with minimal waste. By improving actuator efficiency, overall system performance can be enhanced, leading to better energy management and cost savings in industrial applications.

The other options, while relevant to actuators in some contexts, do not accurately define what actuator efficiency is. For instance, measuring the speed of an actuator does not relate to how much hydraulic energy is effectively converted to mechanical work, and lifespan or force output doesn't directly address the efficiency of energy conversion within the actuator.