Mechanical Design and Analysis of a Discrete Variable Transmission System for Transmission-Based Actuators

Over the past few years, replacing the hydraulic servo actuators with their electrical counter parts for robotics and remote handling systems has been an active field of research. These systems are of particular interest for tasks involved with the US Department of Energy, where the level of radiation exposure is high and the tasks are highly repetitive. With the hydraulic servo actuators, one is concerned with the issues like the high complexity, cost of the system and the difficulty of maintenance of the system. For high payload operations, the hydraulic systems provide an order of magnitude increase in the power density, which is almost impossible to achieve using the electrical servo actuators. Hence, for the electrical servo actuators to be used for high payload operations, the fundamental issue concerning the power and torque density must be addressed. Previous research conducted on this front suggested the use of a variable speed transmission system to spread the servomotor’s torque-speed characteristics across a wider output speed range. This has the effect of allowing smaller high power motors to also deliver high torques at low speeds. By using a variable speed transmission, the motor size can be reduced dramatically while increasing the overall actuator power density in the process. This work goes further into the detailed design of the discrete variable transmission system. A three-stage planetary gear transmission system is considered for the analysis and design. With the use of the three-stage planetary gear transmission, there are a complex and varied design issues involved. Selecting a configuration for the transmission is the first question to be answered. With the given configuration, and the ratios required the individual gears have to be sized accordingly. Other design elements involve the design of the shafting, achieving the desired configuration, bearings, housing and the design of a gear shifting mechanism. A detailed kinematic and dynamic analysis of the entire gear system is required for the design of the various components mentioned above. Analytical results are presented along with a computer-aided analysis of the work using the Pro-Engineer design and analysis software. Future work on this will be to turn this into a commercially available system, which comes down to optimizing the current design. Possibilities of optimization for the current design will be identified. A discussion on the prototype evaluation of the transmission system along with a sample test result is presented

Design and Development of a Planetary Gearbox for Electromechanical Actuator Test Bench through Additive Manufacturing

The development and validation of prognostic algorithms and digital twins for Electromechanical Actuators (EMAs) requires datasets of operating parameters that are not commonly available. In this context, we are assembling a test bench able to simulate different operating scenarios and environmental conditions for an EMA in order to collect the operating parameters of the actuator both in nominal conditions and under the effect of incipient progressive faults. This paper presents the design and manufacturing of a planetary gearbox for the EMA test bench. Mechanical components were conceived making extensive use of Fused Deposition Modelling (FDM) additive manufacturing and off-the-shelf hardware in order to limit the costs and time involved in prototyping. Given the poor mechanical properties of the materials commonly employed for FDM, the gears were not sized for the maximum torque of the electric motor, and a secondary torque path was placed in parallel of the planetary gearbox to load the motor through a disc brake. The architecture of the gearbox allowed a high gear ratio within a small form factor, and a bearingless construction with a very low number of moving parts

Towards High Performance Robotic Actuation

The main objective of this thesis is to enable development of high performance actuation for legged, limbed and mobile robots. Due to the fact that such robots need to support their own weight, their actuators need to be light weight, compact and efficient. Furthermore, a dynamics analysis, shows that the actuators' design may have significant impact on a robot's dynamics sensitivity. These consideration motivate improvements in all actuator design aspects. First, the application-specific design of outer rotor motors with concentrated windings is considered. It is shown that an intrinsic design trade-off exists between a motor's copper loss, core loss and mass, which allows development of motors with superior performance for a particular application. The three main application categories of interest are: electric vehicles, drones and robotic joints. Due to their outstanding torque density, high pole count outer rotor motors are analysed in terms of their design and optimization for robotic applications. Motor design scaling modes are also described in order to outline the main challenges in the implementation of high torque motors. Next, the design of gearboxes for robotic actuation is discussed. A novel type of high reduction Bearingless Planetary Gearbox is introduced which allows large range of reduction ratios to be achieved in a compound planetary stage. In this concept, all gear components float in an unconstrained manner as the planet carrier is substituted with a secondary sun gear. The advantages of the Bearingless Planetary Gearbox over current approaches in terms of improved robustness, load distribution, manufacturability, and assembly are outlined. Finally, analysis, design, and prototyping of rotary planar springs for rotary series elastic actuators is described. A mathematical model, based on curved beam theory, that allows rapid design, analysis, and comparison of rotary springs is developed. Mass reduction techniques based on composite arm structures are introduced and internal arm contact modeling is presented. Motivated by strain energy density analysis, an optimization based spring design approach is developed that allows significant increase in the torque and torque density.</p

More Electric Landing Gear Actuation Study

This report addresses the problem of landing gear actuation system design on more-electric aircraft (MEA). Firstly, information about more-electric aircraft and more-electric actuators was gathered and sorted. Current more-electric landing actuation system applications and researches were also summarized. Then several possible more-electric landing gear actuation concepts were identified. To evaluate these concepts, the case study method has been used. A concept aircraft “MRT7-T”, which has similar maximum takeoff weight to that of Boeing 787, has been chosen as the design case. Systems of different configurations and architectures were designed for this aircraft. In the end of this study, a comparison between different more-electric landing gear actuation systems, and also with traditional central hydraulic system was made. The best concept was proposed. More-electric actuation technology has made considerable progress in the last two decades. However, most of the applications and researches have focused on flight control actuation and brakes. Using more-electric drives for landing gear actuation has been well known to be difficult, for the reason of massive power needs and difficulties in achieving redundancy levels. Famous more-electric research projects like POA and Power-By-Wire only gave recommendation of using electro-hydrostatic actuators (EHA) in landing gear actuation. And no further information is available to the public. In this study, DHS (distributed hydraulic system), EHA (electro-hydrostatic actuator) and EMA (electro-mechanical actuator) were identified as candidate solutions. Design requirements such as retraction time, load and redundancy levels were derived through analysis. As a unique feature, landing gear kinematics concepts were also subject to optimization. Various kinematics concepts were proposed and analyzed in detail, to provide favorable loading and geometrical conditions for the systems. Kinematics design guidelines were built through discussion. Different motors such as AC induction motor, BDCM (brushless DC motor) and PMSM (permanent magnetic synchronous motor) were evaluated for use. Different system architectures were also explored. The multi-discipline optimization method has been extensively used in the design process of the systems. Firstly, each node of the actuation systems was optimized. Then optimizations were made to the systems. Performances of each system were analyzed in several aspects such as weight, power, reliability and maintenance. Comparison of different systems was made through scoring method. The results suggested that DHS, EHA and EMA are all applicable for landing gear actuation. And isolated EHA is the best

MODELING AND HARDWARE-IN-THE-LOOP SIMULATION OF POWER-SPLIT HYBRID ELECTRIC VEHICLES

Conventional vehicles are creating pollution problems, global warming and the extinction of high density fuels. To address these problems, automotive companies and universities are researching on hybrid electric vehicles where two different power devices are used to propel a vehicle. This research studies the development and testing of a dynamic model for Prius 2010 Hybrid Synergy Drive (HSD), a power-split device. The device was modeled and integrated with a hybrid vehicle model. To add an electric only mode for vehicle propulsion, the hybrid synergy drive was modified by adding a clutch to carrier 1. The performance of the integrated vehicle model was tested with UDDS drive cycle using rule-based control strategy. The dSPACE Hardware-In-the-Loop (HIL) simulator was used for HIL simulation test. The HIL simulation result shows that the integration of developed HSD dynamic model with a hybrid vehicle model was successful. The HSD model was able to split power and isolate engine speed from vehicle speed in hybrid mode

Power transmission systems: from traditional to magnetic gearboxes

L'abstract è presente nell'allegato / the abstract is in the attachmen

Advances of Italian Machine Design

This 2028 Special Issue presents recent developments and achievements in the field of Mechanism and Machine Science coming from the Italian community with international collaborations and ranging from theoretical contributions to experimental and practical applications. It contains selected contributions that were accepted for presentation at the Second International Conference of IFToMM Italy, IFIT2018, that has been held in Cassino on 29 and 30 November 2018. This IFIT conference is the second event of a series that was established in 2016 by IFToMM Italy in Vicenza. IFIT was established to bring together researchers, industry professionals and students, from the Italian and the international community in an intimate, collegial and stimulating environment

Design of silent, miniature, high torque actuators

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999.Includes bibliographical references (p. 132-139).by John HEnry Heyer, III.S.M