from one end of its stroke to the other compressed air consumption is limited to the amount of air used for performing the stroke once the actuator reaches its desired end point no additional air is being consumed such pick and place operation is too limited for the actuation of joints in serpentine robots more advanced methods which allow the proportional control of pneumatic actuators were introduced in recent years common to these proportional control methods is their continuing consumption of compressed air both during motion and while remaining stationary this is not a particular concern in conventional i e industrial pneumatic systems where there is usually a local source of compressed air that can provide an unlimited supply of compressed air at little cost however for mobile robots requiring pneumatic actuation these proportional control methods are not suitable another conventional method of implementing proportional control pneumatic is based on the use of servo valves while pneumatic servo valves can be very precise they also tend to be heavy and bulky they are thus more suitable for stationary manipulators than for mobile robots for smaller mobile robots much lighter and compact on off valves are a more applicable solution earlier solutions using on off valves.