Design and parameter identification of a discrete variable transmission system

by 1974- Brown, Kelley Parker

Complex and expensive electro-hydraulic systems have shouldered the workload for remote cleanup operations in radiological and toxicological areas in the past; the payload, reach and speed requirements of most applications have demanded their use. Electromechanically actuated systems (EAS) however offer an alternative that in comparison is much more reliable and maintainable. The problems faced in implementing the EAS are in high payload operations where the hydraulic systems hold a clear power density advantage. For the EAS to compete in the area of torque, very large DC motors have been implemented which make them obsolete in restricted work space areas and prove to be lacking in high-speed applications. New research suggests that this may be overcome by the use of a variable speed transmission or discrete variable transmission (DVT) system to spread the EAS torque-speed characteristics over a wider output speed range. This concept is called Transmission Based Actuators (TBA). This concept will facilitate the use of much smaller high speed motors which, when coupled with a DVT, can offer low speeds at high torques and high speed at low torques thereby matching the performance and size of the hydraulic systems [1]. The work here provides the detailed design of such a DVT comprised of three planetary gear stages. The full design process is discussed along with kinematic, dynamic and parameter identification analyses. The design process consists of determining the configuration, mechanical design for each element and selection of components such as bearings. snap rings and materials. The parameter iv identification portion attempts to quantify constants, such as damping and inertia, which affect the operation of the system. The Matlab System Identification Toolbox (SID) was utilized to accomplish this. This required the creation of a two-degree of freedom dynamic model and the capturing of operational data to estimate the parameters. v