Stepper Motor Basics – Stepper Motor Primer AMS 2014-4
There has been an unfortunate lack of standardization of the terms and components of stepper motor performance, requirements definition, application of torque margin and implementation of test methods. This paper will address these inconsistencies and discuss in detail the implications of performance parameters, affects of load inertia, control electronics, operational resonances and recommended test methods. Additionally, this paper will recommend parameters for defining and specifying stepper motor actuators. A useful description of terms as well as consolidated equations and recommended requirements is included. Presented at the 2014 NASA Aerospace Mechanism Symposium.
Velocity Compensated Eddy Current Dampers –
One of the challenging aspects of spring-loaded deployable systems is the ability to control the deployment velocities over a potentially wide range of operating conditions. Passive dampers are often used to control the rate of deployment and kinematic energy absorption. Fluid dampers have extremely non-linear characteristics and have high Temperature Coefficients of Damping (KBt). Eddy Current Dampers (ECDs) are much more reliable and provide superior linearity and KBt compared to Fluid Dampers, however, variations of operational temperature and input torques often require thermal regulation or complicated deployment structures to tailor deployment characteristics.
Using proven technologies, an internal Velocity Control Module used in conjunction with a shorted alternator type ECD provides near-constant velocity over torque and temperature. This ability may eliminate the need for thermal heaters or expensive cable linkages to control synchronous deployment of multi-hinged arrays. This paper discusses the concept of operation as well as examples of deployment benefits and qualification status. Presented at the 2015 European Space Mechanism and Tribology Symposium.
Implications of Driving High Load Inertia Systems and Reliability Analysis ESMATS_2017_STARIN_Paper_Final
Stepper motors have been used extensively in spacecraft mechanism and solar array drive applications. High Inertia Filter Wheel applications can be challenging with relatively high moment of inertia and high-velocity filter position response requirements. This paper will discuss the design implications and development efforts for a mechanism drive actuator used in geosynchronous weather and Earth-science instrumentation. There are several important aspects of the use of stepper motors in high load inertia systems that this paper addresses. Additionally, we introduce a methodology for MTBF and reliability calculations for mechanisms and actuators. This paper was published at the 2017 European Space Mechanism and Tribology Symposium.