Proposed Motorization Ratio Computation Method for Low Duty Cycle The Rotary Actuator shall have its powered output torque high enough to successfully operate without  adding or Iosing steps with a minimum motorization margin of 200%, i.e., the ratio of the powered output  torque to the total resistive torque at actuator output shaft level shall be greater than 3:1. To that extent,the following two complementary approaches are usually considered: /g120Either “mechanism design-oriented” approach:  motorization margin shall be sufficient during the  design phase considering all contributors – such as IL (internal losses) and customer needs (RT  and IT). This is relevant at Critical Design Review /g120Or “mechanism user-oriented” approach:  motorization margins shall be sufficient to cover  possible evolutions of internal properties (IL) and customer needs (RT and IT). This is particularly  relevant for mechanisms featuring significant heritage at Acceptance Testing As the pulse shape has a great influence on the powered output torque, the motorization margin shall be  determined in two phases; at Critical Design Review and at Acceptance Testing: Also, the motorization ratio computation shall properly reflect the two drive possibilities: • When driven at 100% duty cycle (see DMR formula hereafter);  • When driven at Iow duty cycle (see DMR & SMR formula hereafter) Motorization Ratio Calculations: i) When driven at 100 % duty cycle, the so called dynamic motorization ratio (DMR) shall be determined  as follows:  ART 100- 0.5 x IL DMR = ------------------------   >3      ( I T  +  R T ) where: • ART 100: minimum actuator running torque when driven by pulses at 100% duty cycle under any  operational conditions. /g36/g87/g3/g38/g39/g53/g15/g3/g36/g53/g55 /g20/g19/g19/g3/g76/g86/g3/g68/g3/g83/g85/g72/g71/g76/g70/g87/g72/g71/g3/g89/g68/g79/g88/g72/g3/g69/g92/g3/g68/g81/g68/g79/g92/g86/g76/g86/g15/g3/g68/g81/g71/g3/g71/g88/g85/g76/g81/g74/g3/g55/g72/g86/g87/g3 /g36/g53/g55/g20/g19/g19/g3/g76/g86/g3/g68/g3/g80/g72/g68/g86/g88/g85/g72/g71/g3/g89/g68/g79/g88/g72/g17 • IL: internal Iosses due to friction • IT: inertial torque• RT: resistive torque Concerning the DMR, it could be noticed that:  /g120The formula is relevant during the ON time when the pulse is applied – so not only for the 100%  duty cycle case. However, the most reliable way to measure the DMR is to drive the actuator at 100% duty cycle /g120The ART 100is obtained with nominal values as per manufacturing (i.e., 1 x IL). In order to  anticipate any detrimental evolution, an uncertainty factor of 1.5 on IL is considered as per ESA Table 1. The difference corresponds to the term “0.5 x IL” subtracted in DMR formula numerator. /g120The minimum DMR value corresponds to the motor location/step featuring the highest detent  torque. So it shall be measured at least over a complete motor revolution – and preferably 2 revs. ii) When driven at Iow duty cycle, the rotary actuator is holding during the unpowered time of pulses on  its motor detent torque. The unpowered portion of the pulse is the static part of the actuator torque  holding capability. The internal loss should not be considered when the actuator is unpowered since it  is a result of actuator stepping. Both resistive and inertial torques should use the static motorization  ratio (SMR) formula and should be as follows:                  357