478 but most of them  were withdrawn in the frame of the design reviews. Part of the design to cost approach  was evaluation of the anticipated product cost in series production.  

Figure 4.  Future Actuator  concept drawing with planetary gear  

The design to cost was not only considered on mechanism level but also on system level where it was  ensured that instead of a dedicated electronics for each actuator , a central electronics for all actuators was  possible. At the end of the b readboard design loop,  the cost for the series standard was available and could  be compared with the programmatic requirements. It is import ant to mention that design to cost does not  necessarily mean that the cost of all components has to be driven down as much as possible. It is more the  correct balance between cheaper parts combined with high quality  ones . Or, in other words , the design  shall be optimized around performance and cost and not around requirements.  With the selection of high  quality parts where appropriate, saving s in different areas can be achieved. Therefore, the design to cost  approach is a weighing- up of the pros and cons of different parts always considering the top- level  requirements.  

Another aspect of the design to cost approach is a reduction of the number of parts. Therefore, specific  attention was paid on the number of parts in the actuator. Specific at tention was also paid on a compact  design, short load path, robustness and small mass. The goal was to design the actuator that it fits into the  volume and mass of the existing SARA21 but with improve d internal load path and high robustness.     The high gear ratio caused an additional and new design constraint. For the actuator development , the goal  was set to allow the actuator to run against the hard end stop. Therefore, the end stop was designed for an output torque of 300 Nm. Despite the high  torque,  the mechanical end stop had to be light and slim.  Therefore, the end stop geometry was optimized to achieve t he optimal contact geometry only under load  in order to avoid a punctual contact surface under high load. In addition,  the material coatin g was chosen  to avoid cold welding under high contact stress. However, an end stop has its disadvantages and if possible  should be avoided.   

Sensor Selection  The position sensor is a specific element  of the Future Actuator. The potentiometer used in the SARA21 is  a well proven and low price  solution but it cannot comply with the Future Actuator accuracy . Therefore,  the  goal was to replace the potentiometer with a contactless sensor which should be able to perform an  absolute position measurement directly at the output shaft.    With the position sensor , basically the same approach was followed as for the gearbox. Based on a  preliminary concept the supplier was contacted with goals instead of requirements. Together , the concept  was elaborated, refined, developed and implemented. Many sensor technologies were considered in the  trade- off and the decision was made to use a magneto resistive (MR) sensor which showed very promising  results in another project at RUAG . During the sensor evaluation process different MR sensor solutions