the outlet valve 28 thus by controlling the voltage level of the power supply and modulating its frequency through the powertrain control unit the diaphragm motion can be accurately controlled achieving the desired level of oil flow rate and pressure the power requirement varies depending on the specification of the piezoelectric stack 32 operating conditions and duty cycles the actuator 11 of fig2 consumes electrical energy only during a gear ratio change called a shift event which typically lasts for 1 sec and intermittently thereafter if required to make up the effects of oil leakage if any its peak power consumption is expected to be below 100 watts during the short engagement interval in contrast an engine driven oil pump runs constantly in a typical automatic transmission system continuously consuming from 700 watts 1 hp to over 2000 watts 3 hp of engine output depending on pump capacity and operating conditions the piezoelectric pump 13 has no rotating elements unlike a conventional electrical pump attaining a superior hydraulic response time required for directly controlling pressure applied to a friction component during its engagement however the pumping capacity of the piezoelectric pump is generally insufficient by itself for stroking a friction component servo within 0 5 second or less when friction component engagement is commanded fig4 a 4 b and 4 c illustrate the unique operating principles of the actuator 11 based on the arrangement of sub systems shown in fig2 the actuator 11 is illustrated with a band brake 12 as an example fig4 a shows the state.