It is important to consider the nominal characteristics of actuators. These include weight, power and power to weight ratio, operating pressure, operating voltage, temperatures, and other. For example , since in many robotics systems the actuators are placed directly at the joints, and therefore, move with them, the weight of the actuator acts as a load on the preceding actuators and must be accelerated and decelerated by them. A heavier actuator downstream requires more torque upstream, resulting in larger power requirements and heavier actuators. Consequently, it is very important to consider the weight and placement of actuators