DESIGN PROJECT MECHANISM FOR ROTATING A SICK LADAR EML 2023 COMPUTER AIDED GRAPHICS AND DESIGN FALL 2016 ARIEL GUTIERREZ HIMAL PATEL

Transcription

1 EML 2023 COMPUTER AIDED GRAPHICS AND DESIGN FALL 2016 DESIGN PROJECT MECHANISM FOR ROTATING A SICK LADAR ARIEL GUTIERREZ HIMAL PATEL 0

2 A. Table of Contents A. Table of Contents 1 B. Introduction 2 C. Design Specifications 2 D. Background Information 3 E. Design Concept 4 1) Design Concept 1 4 2) Design Concept 2 4 3) Design Concept 3 5 F. Selection of Design Approach 6 G. Design Description 6 1) Sub-Assembly 1 7 2) Sub-Assembly 2 9 3) Sub-Assembly ) Final Assembly 12 H. Cost Analysis 14 I. Appendix 15 1) Drawing of Primary Base (CAD-MP-0001) 16 2) Drawing of Secondary Base (CAD-MP-0002) 17 3) Drawing of Tertiary Base (CAD-MP-0003) 18 4) Shaft Adaptor (CAD-MP-0004) 19 5) Shaft (CAD-MP-0006) 20 1

3 B. Introduction The purpose of this project is to design a device that can rotate a Sick Ladar model LMS 291 around an axis that goes through the sensor. The axis of rotation will be held by supports on both sides of the sensor, which will be driven by a Denso DC motor. This design allows for the sensor to rotate a full 360 degrees around the axis, with minimal obstruction from the device. C. Design Specifications Figure 1. Sick Ladar The mechanism used to rotate the Ladar must follow these constraints: a. The actuators must be either the 135 RPM 12 VDC Buehler Gearmotor or the Denso DC Motor. b. Every actuator will have a Honeywell / Clarostat CBL Optical Encoder in order to have the ability to use the closed loop feedback control. c. Every actuator must have a homing switch d. Every actuator must have motion limit switches if there are limits to the actuator's rotation e. If a solenoid is needed, use the 12 V DC solenoid available from McMaster Carr (part number 70155K49), 2

4 f. The design must include one Device Craft Motor Driver for each motor g. The design must include one National Instruments (NI) 6009 DAQ for each motor h. The device must fit within a 36"x36"x36" volume, i. The cost of building one prototype device must be identified j. The weight of the device, must not exceed 100 lbs. k. Rotation angle must be at least 240 degrees. l. Speed of rotation must be at least 90 degrees per second. m. The total cost cannot exceed $2000. D. Background There are few other devices in the market that have similar mechanism to Lidar. Tilt cameras are good examples because they use this mechanism. Tilt cameras are used to take pictures and videos in diagonal fashion. A camera is set at a certain angle, and it rotates on an axis. Tilt cameras were researched because they pan, a mechanism where a camera rotates in horizontal direction either left or right resulting in a sharp subject but blurry background. Another example of the devices is solar panels. Solar panels are designed in a way that it absorbs sun s rays as a source of energy. In order optimize the absorption of the sunlight mechanisms are used to rotate the solar panels corresponding to the direction of the light. Both of these devices have mechanism that rotates them around an axis. Figure 2. Tilt Camera 3

5 E. Design Concepts 1) This was the first concept developed for the mechanism used to rotate the Ladar. In this concept the Ladar is fixed on a plate. This plate has two rods attached to each side. One Denso DC motor is attached to the right side of Figure 3. First Concept Sketch the design as shown in Figure 2. The mechanism will use a motion limit switch because it will only be able to rotate 300 degrees. The homing switch will be placed next to the motion switch. The encoder is attached in the other end of the rod with two gears of the same ratio in order to capture the same revolutions as the shaft. Lastly, in the base the DAQ and device craft motor driver are placed. 2) This is the second design concept for the mechanism of the Ladar. The design is different from the first because it will be rotating along the z axis and the Ladar will be placed horizontally on a plate. The plate is connected to a shaft that is rotated by a Denso DC motor. Four spacers will be used to connect a secondary plate and the base. The DAQ and Figure 4. Second Concept Sketch the device craft motor driver will be placed on the base. In addition, the middle plate will have three gears. The motor and the main shaft will have one to one ratio and motor and the gear attached to the encoder will have 4

6 1.41 ratio. The encoder will be capturing the revolutions from the shaft. This design will not use a motion limit switch because it will be able to rotate 360 degrees. Figure 5. Third Concept Sketch 3) In the third concept the Ladar is attached to two plates, rods connected to a shaft, and a Denso DC motor. This is very similar to the first concept; however, the mass in this concept will be distributed better. The encoder will be attached to the left plate and it will be moved by gears as well. The DAQ and motor driver will be placed in the base on the structure holding the Sick Ladar. This design will require a motion limit switch because it can only rotate 240 degrees. 5

7 F. Selection of Design Approach Using the constraints given by the supervisor and the various possibilities of rotating the Sick Ladar along the required axis several sketches and ideas were developed. In order to determine the best design, certain characteristics were checked from each idea. This includes weight, cost, and the position of the Sick Ladar. In all designs the same components will be used and these include the Sick Ladar, homing switch, motor driver, Denso DC motor, encoder, and gears; however, the positioning of the items would vary depending on the rotating mechanism of the Ladar. A major specification is that the design must not exceed 100 lbs. A design matrix table was developed to finalize the selection of the three concepts. There are four different areas considered including weight, visual range, cost, and support. The weighting factor was placed to each category and the parameters. Design Matrix Objective Weighting Factor Parameter Design 1 Design 2 Design 3 Mag. Score Value Mag. Score Value Mag. Score Value Weight 0.3 Pounds Visual 0.4 Degrees Range Cost 0.1 Dollars Support 0.2 Experience Good Good Very Poor Overall Value Based in the overall values above, the best decision is clearly design 2. G. Design Description Table 1. Design Matrix The mechanism will make it possible for the Sick Ladar to rotate about the specified axis. The main parts of this design include three bases which are made of aluminum. Aluminum was chosen as the material of the platforms because it is very light and strong. In addition, aluminum can easily be purchased as metal sheets or rods from online stores such as McMaster-Carr. Later, the metal sheets can be processed through subtractive prototyping. The assembly of this mechanism is divided into four sections, three sub-assemblies and a final assembly. 6

8 1) Sub-Assembly 1 Sub Assembly 1 (CAD-MA-0001) is composed of thirteen parts. The main parts in this collection include the primary base (CAD-MP-0001), motor (DENSO ), device craft motor driver (CAD-MP-0002), and shaft adaptor (CAD-MP-0004). Figure 6. Exploded View of Sub-Assembly 1 The motor (3) will be attached to the primary base (1) by using socket head cap screws (12), unthreaded spacers (6, 7), flat washers (11), and steel hex nuts (13). The device craft motor driver (2) will be mounted by using a din rail (4) and the din rail will be attached to the primary base by using pan head machine screws (5). Four aluminum female threaded standoffs (9) will be used to connect the primary base to the secondary base. The standoff is fastened by using flat head machine screws (8). A shaft adaptor (10) will be connected to the main shaft of the motor for the next assembly. The primary base will be manufactured by using subtractive prototyping and drawing sheet of this model can be found in the appendix. 7

9 Figure 7. Transparent View of Sub-Assembly 1 Figure 8. Render of Sub-Assembly 1 8

10 2) Sub-Assembly 2 Sub-Assembly 2 (CAD-MA-0002) contains 18 parts in total. There are eight main parts in this assembly which include the optical encoder (HONEYWELL-600EN-128-CLB), ball bearing (MCMASTER-6661K230), sleeve bearing (MCMASTER-1688K140), National Instruments Data Acquisition (NI- USB ), switch (MCMASTER-7779K140), shaft (CAD- MP-0007), and two spur gears (RUSHGEAR-Y3232A, RUSHGEAR Customized Part). Figure 9. Exploded View of Sub-Assembly 2 The NI DAQ (5) will be mounted on the secondary base (1) by using an unthreaded spacer (12), washer (13), socket head cap screw (14), and hex nut (15). The optical encoder (6) will be attached from the bottom of the secondary base. The threads will pass through the hole in the base and it will be attached with the encoder nut (7). A spur gear (8) will be press-fitted on the encoder. Another spur gear (9) will be press-fitted on the main shaft (4) using a set screw (10). The main shaft will be supported by two bearings (a ball bearing and a sleeve bearing). The sleeve bearing (2) will support the shaft at the bottom. The assembly of the spur gear (9) and shaft (4) will be press-fitted on the ball bearing (3). A homing switch will be attached on the secondary base by using two steel socket head screws (17), nylon flat washers (16), and narrow hex nuts (18). A drawing sheet of the secondary base is available in the appendix. 9

11 Figure 10. Transparent View of Sub-Assembly 2 Figure 11. Render of Sub-Assembly 2 10

12 3) Sub-Assembly 3 Sub-Assembly 3 is composed of 4 different items. These include the tertiary base (CAD- MP-0008), Sick Ladar (LMS 291), flat head phil machine screws (MCMASTER-90273A151, and MCMASTER-90273A199). Figure 12. Exploded View of Sub-Assembly 3 The Ladar (2) will be mounted on the tertiary base (1). Two different kind of machines screws will be used to attach the Ladar to the base. Two flat head phil machine screws (4) will go through the bottom of the base and Ladar s threads. In addition, three flat head phil machine screws (3) will pass through the side walls of the base and into the Ladar s threads. Figure 13. Transparent View and Render of Sub-Assembly 3 11

13 4) Final Assembly The final assembly combines all the sub-assemblies and other items required to fasten the parts. It is composed of the primary base sub-assembly (CAD-MA-0001), secondary base subassembly (CAD-MA-0002), tertiary base sub-assembly (CAD-MA-0003), a spur gear (RUSHGEAR-TS3245), and flat head machine screws (MCMASTER-90273A833). Figure 14. Exploded View of Final Assembly The secondary base (2) will be placed on top of the primary base (1) and they will be attached by using flat head phil machine screws (5). Furthermore, a spur gear (4) will be pressfitted to the shaft adaptor from the secondary base sub-assembly. Finally, the tertiary base (3) will be placed and press-fitted on the main shaft from the secondary base sub-assembly. The gear ratio between the spur gear (4) and the spur gear in the main shaft is 1 because they both have the same amount of teeth. Also, the gear ratio between the spur gear (4) and the spur gear attached to the encoder is 45/32 = The gear attached to the shaft of the motor will make it possible for the encoder to capture the revolutions. It is important to consider the gear ratio (1.406) between the motor and the encoder because that will change the rotation of the encoder relative to the motor. Furthermore, the motor will be able to rotate the main shaft connected to sub-assembly 3, making it possible for the Ladar to rotate about the specified axis. 12

14 Figure 15. Render of Final Assembly 13

15 H. Cost Analysis The total cost for the production of the mechanism for rotating the Ladar is $ This includes all main parts such as the NI DAQ, Denso Motor, and Device Craft Motor Driver. The full cost analysis is shown below. The Ladar was not included in the cost analysis since it will be provided. Table 2. Cost Analysis 14

16 I. Appendix 1) Drawing of Primary Base (CAD-MP-0001) 16 2) Drawing of Secondary Base (CAD-MP-0002) 17 3) Drawing of Tertiary Base (CAD-MP-0003) 18 4) Shaft Adaptor (CAD-MP-0004) 19 5) Shaft (CAD-MP-0006) 20 15

17 1) Drawing of Primary Base (CAD-MP-0001) 16

18 2) Drawing of Secondary Base (CAD-MP-0002) 17

19 3) Drawing of Tertiary Base (CAD-MP-0003) 18

20 4) Shaft Adaptor (CAD-MP-0004) 19

21 5) Shaft (CAD-MP-0006) 20