Design of Silent, Miniature, High Torque Actuators by John Henry Heyer III Bachelor of Science in Mechanical Engineering University of Rochester, 1995 SUBMITTED TO THE DEPARTMENT OF MECHANICAL ENGINEERING IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN MECHANICAL ENGINEERING AT THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY MAY 1999 © 1999 Massachusetts Institute of Technology. All Rights Reserved. A uth o r ............................................... , ,.,v .... ... ............ De~p~9nIf Mechanic ygineering / ~May 7,1999 Certified by ............. Woodie C. Flowers Pappalardo Professor of Mechanical Engineering The supervisor C ertified by ...................................... ................ ....... David R. Wallace Ester and Harold Edgerton Assistant Professor of Mechanical Engineering .,- )Thesis Supervisor A ccepted by .............................................. .. ........................ Ain A. Sonin Professor of Mechanical Engineering Chairman, Department Committee for Graduate Students MASSACHUSETTS INSTITUTE MASSACHUSETTS INSTITUTE OF TECHNOLOGY OF TECHNOLOGY LIRLIBRARIES E 1LIBRARIES Design of Silent, Miniature, High Torque Actuators by John Henry Heyer III Submitted to the Department of Mechanical Engineering on May 7, 1999 in partial fulfillment of the requirements for the degree of Master of Science in Mechanical Engineering Abstract Specifications are given for an actuator for tubular home and office products. A survey of silent, miniature, low cost, low-speed-high-torque actuators and transmissions is performed. Three prototype actuators, including an in-line spur gear actuator, a differential cycloidal cam actuator, and a novel actuator concept, all driven by direct current motors, are designed, built, and tested. A fourth actuator, an ultrasonic motor, is purchased off-the-shelf and tested. The prototypes are ranked according to noise, torque, efficiency, and estimated cost, among other criteria. Thesis Supervisor: Woodie C. Flowers Title: Pappalardo Professor of Mechanical Engineering Thesis Supervisor: David R. Wallace Title: Ester and Harold Edgerton Assistant Professor of Mechanical Engineering 3 Acknowledgements Mr. Joel Spira, Chairman and Director of Research, Lutron Electronics Co., is gratefully acknowledged for sponsoring this work, and providing an excellent educational opportunity. Professors Woodie Flowers and David Wallace are gratefully acknowledged for their advice, patience, and clever ideas. In addition, the following people are respectfully acknowledged: e Tony Caloggero of the MIT Edgerton Center for use of the high-speed photography equipment. e Roman of the MIT Machine Shop for machining services. * Nathan, John, Jeff, and Greg of Technique Applied Science for machining and assembly services. * Tim Glenn of the MIT Department of Aeronautics and Astronautics for ultrasonic motor information. e K. Tuchiya of Shinsei Corporation for the ultrasonic motor and information. " Robert Pighetti of Igarashi Motor for the DC motors and information. * Ken Heiting of Heiting Tool and Die for rapid machining services. e William Rouverol of Axicon Gear for differential crowning information. e Donald Houser, Lynn Faulkner, and Rod Kleiss for gear noise information. " Scott Hoffman of Accu-Prompt for manufacturing information. * Gary Rawding of G&D Enterprises for rubber and urethane molding information. e Lawrence Van Epps of Meridian Laboratory for prompt provision of molded parts. e John Carver of the Gleason Works for information on nutating gears. e Tom Mifflin of Arrow Gear for gear information. e Jim Lombara and Jason Killo of Lutron for helpful correspondence. * Matt, Ben, John, and Julie for use of the computer and room. e Joel Spira for the candy bars. * All others who contributed information and services. 4 Table of Contents Abstract .................................................................................................................................. 3 List of Figures......................................................................................................................10 List of Tables ....................................................................................................................... 12 Chapter 1...............................................................................................................................13 Introduction ........................................................................................................................... 13 1.1 Purpose.......................................................................................................................13 1.2 A ssumptions...............................................................................................................13 Chapter 2..............................................................................................................................14 Design Specifications and Approach ................................................................................. 14 2.1 Specifications ............................................................................................................. 14 2.1.1 Power Source................................................................................................... 14 2.1.2 N oise ................................................................................................................... 14 2.1.3 Sizecr ..... r....p. c................................................................................................ 15 2.1.4 Torque and Speed Ovd........... .............................. ................................. 15 2.1.5 Back-Driving and Shock Overload .................................................... 16 2.1.6 Efficiency ............................................................................................................ 16 2.1.7 Life ........tioni........................................................................................... 17 2.1.8 Positioning Accuracy........................................................................................... 17 2.1.9 Installation ............................................................ ............................................... 19 2.1. 1 Cost 1............................................................................................................ 19 2.1.11 Sum m ary........................................................................................................ 20 2.2 Design Approach .................................................................................................. 20 2.2.1 Actuator Level................... ....................................................... 20 2.2.2 System s Level................................................................................................... 21 2.2.3 Design Architecture and Relation to Noise ....................................................... 21 2.3 Discussion on Sim ulation........................................................................................ 22 2.4 Background and Discussion on Noise ...................................................................... 23 2.4.1 Design Goals................................................................................................... 24 5 2.4.2 N oise Standards and M easurement.................................................................... 24 2.4.3 Further N oise Considerations.......................................................................... 26 Chap ter 3 ............................................................................................................................. 28 Survey and Selection of Concepts ..................................................................................... 28 3.1 Electromagnetic Motors with Speed Reducing Transmissions ................................ 28 3.1.1 Com m on Com ponents ..................................................................................... 28 3.1.1.1 Electrom agnetic M otors ................................................................................ 28 3.1.1.2 Shafts............................................................................................................ 29 3.1.1.3 Bearings........................................................................................................ 30 3.1.1.4 Gears ............................................................................................................ 31 3.1.2 Transm ission Concepts ..................................................................................... 37 3.1.2.1 In-Line Involute Spur or Helical Gear ........................................................ 37 3.1.2.2 Planetary Involute Spur or Helical Gear .................................................... 39 3.1.2.3 Planetary Ball Bearing .............................................................................. 41 3.1.2.4 Planocentric ............................................................................................. 41 3.1.2.5 Differential Involute Spur or Helical Gear.................................................. 42 3.1.2.6 Differential Cycloidal Cam ........................................................................ 44 3.1.2.7 Three-Gear Differential............................................................................ 45 3.1.2.8 W orm and Bevel Gear............................................................................... 45 3.1.2.9 Nutating Bevel or Spiral Bevel Gear .......................................................