"Final Report - Interdisciplinary Capstone Design"
To: Jeff Young CC: Ryan Adams, Steve Beyerlein From: Adrian Gomez, Brian Chamberlin, and Cristy Izatt Date: 6/8/2012 The contents of this report are in connection with the test fixtures for the antenna anechoic chamber in the University of Idaho department of Electrical and Computer Engineering. This report is a final report of the design and manufacturing of two positioning fixtures for antenna testing purposes. For additional information you may find our website to be helpful (http://seniordesign.engr.uidaho.edu/2005_2006/calibratethis). If you have any questions regarding this report, please feel free to contact the team at firstname.lastname@example.org. Team Calibrate This would like to thank you for providing funding for this project, as it has been a great learning experience and exciting challenge. Sincerely, Calibrate This Prepared for: Prepared for: Proff.. Jeffffery L.. Young Pro Je ery L Young Mr.. Ryan Adams (Seniior RA) Mr Ryan Adams (Sen or RA) Departtmentt off Ellecttriicall and Computter Engiineeriing Depar men o E ec r ca and Compu er Eng neer ng Prepared by: Prepared by: Team “Calliibratte Thiis: A Feedhorn” Team “Ca bra e Th s: A Feedhorn” Adriian Gomez Adr an Gomez Briian Chamberlliin Br an Chamber n Criistty Izatttt Cr s y Iza December 9tth,, 2005 December 9 h 2005 Executive Summary This report details the design and manufacturing of two test fixtures for aligning test equipment in an antenna anechoic chamber used by Professor Jeffery L. Young and his graduate students. One test fixture allows for height adjustment of the antenna being tested, while the second test fixture provides five degrees of freedom in aligning a feedhorn that broadcasts to the antenna. Each test fixture has been designed and built separately and will be installed in the anechoic chamber in Buchanan Engineering Laboratory, room 206 at the University of Idaho. Deliverables for this project include two user-friendly alignment fixtures, which meet all of the customers’ specifications, as well as a users manual describing proper use and operation of the fixtures. Table of Contents 1.0 Background…………………………………………………………….. 1 2.0 Problem Definition……………………………………………………. 2 2.1 Deliverables…………………………………………………….... 2 2.2 Specifications…………………………………………………..... 3 3.0 Concept Development………………………………………………....3 3.1 UUT Base Positioner…………………………………………... 3 3.2 Feedhorn Linear adjustment………………………………… 4 3.3 Feedhorn Angular Adjustment……………………………… 6 3.4 Alignment Verification………………………………………... 8 4.0 System Architecture…………………………………………………... 9 4.1 System Level Review…………………………………………… 9 4.2 Detail Description of Each Component……………………. 10 4.2.1 Feedhorn Linear Adjustment Fixture………………... 10 4.2.2 Feedhorn Angular Adjustment Fixture………………11 4.2.3 UUT Height Adjustment Fixture……………………...12 5.0 Design Evaluation……………………………………………………...13 6.0 Future Work……………………………………………………………. 14 7.0 Appendix………………………………………………………………….15 1.0 Background The Advanced Microwave Ferrite Research (AMFeR) program at the University of Idaho is preparing to build an antenna anechoic chamber in which they will test antenna power patterns generated associated with any polarization or polarization plane. This chamber will measure approximately 13 feet in length, 9 feet in width, 9 feet in height and be located in the Buchanan Engineering Laboratory at the University of Idaho (Fig.1). Figure 1: Sample Antenna Anechoic Chamber as seen from the feed fixture. AMFeR has decided to fund a team of mechanical engineering students to build a set of positioning test fixtures that will be installed in their chamber. These fixtures consist of a) a height-positioning unit for the unit under test (UUT) and b) a five degree-positioning unit for the feed antenna. At the beginning of each test, the relative positions of the UUT and feed antenna are critical. The key consideration in the design of both test fixtures is the availability of enough degrees of freedom to assure that the feed antenna face and UUT face are parallel and that the two antennas are axially aligned. Once alignment is verified, the prototype antenna will move in different directions. As the antenna moves, data will be taken to observe power patterns. With this data, the AMFeR program will be able to improve antenna design to better receive reception. 1 2.0 Problem Definition To make a precise measurement, it is imperative that the UUT and the feed antenna are bore-sight aligned and true relative to plumb and the horizontal plane. In order to achieve this calibration, the fixtures must provide five degrees of freedom (Fig.2). Once the UUT and feedhorn are attached to the fixtures, they must be adjustable in the x, y, z, tilt and swivel directions and provide enough movement to ensure that their faces are parallel. Roll, azimuth, and polarization adjustments will be made using equipment purchased by the AMFeR program (Fig.2). The fixture must also be able to accommodate the different shapes and sizes of both feed and receive antennas. Once built and installed the fixtures must be relatively easy to use and adjust by the client, Jeff Young, as well as all graduate and undergraduate students in Jeff’s lab. Figure 2: Degrees of Freedom 2.1 Deliverables As a final product, a set of fixtures will be constructed and installed to allow for any circumstantial alignment of the UUT and feedhorn. The UUT fixture will allow for height and coarse leveling adjustment of the existing antenna fixture, while the feed fixture will allow for coarse and fine adjustments of five different degrees of freedom. The feed fixture will also be able to accommodate all feedhorns specified by the customer and provide verification of alignment between the feedhorn and UUT. In addition to these fixtures, an easy to follow instructional video or instruction manual must be 2 provided so that any non-mechanical engineer can align the system whenever it is deemed necessary. 2.2 Specifications After the first few customer meetings, as list of specifications for the final product was generated. This list was then organized into two sections, “musts” and “shoulds”. On the “musts” list are specifications that the product must satisfy in order to accomplish the needs of the customer, and on the “shoulds” list are specifications that the product should achieve in order to exceed the customers’ expectations. These lists are as follows: Product must satisfy the following: Feedhorn must have 5 degrees of freedom X, Y, tilt, and swivel must have fine adjustments Coarse adjustment in all 5 degrees of freedom Locking mechanisms for all 5 degrees of freedom Horn and antenna must sit 4.5 feet above floor of anechoic chamber Horn must extend into room at least 5 inches but no more than 17 inches Feedhorn fixture must support at least 50 pounds Feedhorn fixture must be adaptable to all specified horn sizes Fixtures must be designed separately from chamber Fixtures must provide alignment verification All fixtures must be safe for customers to use Antenna fixture must sit at least 12 inches above chamber floor Fixture material must not interact in any manor with the testing instrumentation Product should satisfy the following: Degrees of freedom should be adjustable by hand Fixture should be resistant to getting bumped out of alignment Total project should cost less than $1500.00 Fixtures should require no maintenance Fixtures should last 10 or more years 3.0 Concept Development 3.1 UUT Base Positioner Because this fixture only needed to provide adjustment in the z-direction with very small tilt adjustments, its design involved only one concept, with one minor change. Originally we designed two rectangular plates joined by four all thread screws, one on each corner. The bottom plate would be mounted to the floor of the chamber and the top plate would be mounted to the bottom of the azimuth positioner at the base of the existing UUT 3 fixture (Fig.4). After reviewing this design with the customer, it was determined that the adjustments would be more easily made with the two plates joined by only 3 all-thread screws, in a triangular pattern. After making this minor change as well as some aesthetic details, this fixture concept was complete (Fig.3). Bubble Levels Top Plate Figure 3: UUT height positioning fixture Figure 4: Assembly of UUT height positioning fixture 3.2 Feedhorn Linear Adjustment The system that would be making the linear adjustments of the feedhorn had only a couple iterations. The overall design had only one major change, while there were a few changes to the components within the design. 4 The only overall design change was to the X and Y adjustment box support. Because the first set of feedhorns specified by the customer were of substantial weight and length differences, a movable support arm was considered so that the box could be correctly supported for each horn. For this concept, the support arm would be positioned behind the box for smaller horns, then removed and re-positioned in front of the box for larger horns. However, a new set of feedhorns was specified by the customer, which eliminated the need for this extensive box support, as the new feedhorns are much smaller. The final design consists of two support arms rigidly attached to the back of the box (Fig.5). There were three changes to the internal components of the overall design. These changes had to do with the X, Y, and Z-direction rails, as well as the X and Y-direction screws. For the Z-direction rails, the first proposal was to use two solid rods, which would be attached to a table at both ends. The potential problem with this equipment was that the weight of the box could possibly cause these rails to bend in the middle where they were unsupported and sitting approximately one inch off the table. To solve this problem, a set of rails was chosen which would mount directly to the table along their entire length, eliminating any possible bending stresses. For the X and Y-direction rails, the design originally called for only one rail for each direction of movement. Upon closer assessment, it was decided that two rails in each direction would provide better support and reduce any binding or bending that could result from the weight of the feedhorn and stepper motor assembly that would be supported by these rails. And finally, for the X and Y-direction screws, a set of all-threads was originally thought to be sufficient. However, after discussing this with the University of Idaho Machinist, Russ Porter, it was determined that using an ACME threaded screw would eliminate any binding, while providing smooth adjustments. To turn these screws, cranks were attached to the end of each. Upon request from the customer, these cranks were 5 eliminated and the end of each rod was machined into a square cross-section to allow for crescent wrench adjustments only. Y- Direction Crank X-Direction Crank X Y Z Back view Front view Figure 5: Feedhorn X and Y adjustment fixture Z Figure 6: Feedhorn Z-direction adjustment rails on Aluminum plate 3.3 Feedhorn Angular Adjustment The system that would be making the tilt and swivel adjustments for the feedhorn had several different iterations before the single turnbuckle and bevel gear approach was adopted. The first consideration was to employ a screw jack to increase and decrease the tilt angle of the feedhorn and to use a turntable-type approach for the swivel adjustment. 6 After speaking with Machinist, Russ Porter, we determined that alignment of the horn would be easier if the tilt and swivel adjustments shared a common axis of rotation. In order to accomplish this, Russ suggested that we use a universal joint for those adjustments. This universal joint method was abandoned after it was determined that the implementation of a U-joint would require a large amount of space, as well as result in failure to satisfy the functional requirements of the project. Reevaluation of the original screw jack and turntable approach resulted in the design of a system that used turnbuckles to make the tilt adjustment and bevel gears controlling a turntable to make the swivel adjustment (Fig.7). At first, two turnbuckles were to be installed to make the tilt adjustment. This plan was discarded after consideration of having two sources of input for only one motion. This setup would result in one turnbuckle “fighting” against the other. Alternatively, a single turnbuckle system was developed in order to obtain an adjustor that kept the horn level and didn’t have a tendency to bind when adjusted. Upon inspection of turnbuckles that could be purchased, it was determined that a custom turnbuckle would need to be designed and created in order to achieve the fine adjustments required, as purchased turnbuckles have very coarse threads. This custom turnbuckle consists of several custom-machined steel parts so as to avoid any binding or loading issues associated with the use of aluminum. The turnbuckle is threaded at only one end in order to allow for a more controlled fine tilt adjustment. To compensate for having a turnbuckle on only one side of the tilt fixture, a lock-down mechanism was designed for the opposite side to avoid any binding. This lock-down features consists of two slotted pieces of steel which will slide past each other as the turnbuckle is adjusted and lock by tightening a nut which would clamp the two pieces together. This mechanism is to insure that no unnecessary movement occurs once the unit is calibrated to a desire state. 7 Turnbuckle for tilt adjustment Turntable for swivel adjustment Swivel Knob for swivel adjustment Tilt Bottom piece of L-Bracket the L-bracket Figure 7: Feedhorn tilt and swivel adjustment system 3.4 Alignment Verification In order to verify that the faces of the UUT and feedhorn are perfectly aligned, it was determined that a laser and mirror system would be the most precise. This system would consist of a laser being fed through the center axis of the feedhorn fixture and reflecting off a mirror attached to the face of the UUT. Once the two fixtures are perfectly aligned, the laser beam would reflect off the mirror and trace directly back onto itself. The alternative concept was a system of bubble levels mounted in key spots on each fixture. However, it was determined that this method would make alignment difficult and time consuming, and it would not yield the precise alignment verification needed. Therefore, our final concept involves a laser and mirror system with a few bubble levels for quick visual alignment verification. To analyze this laser and mirror system, a test fixture was developed (Fig.8). This fixture consists of a sample feedhorn provided by the customer, a custom stand to allow for tilt adjustment, and a machined aluminum block used to house the laser and mount the feedhorn to the stand. 8 Figure 8: Test fixture for the laser and mirror system The mirror was to be placed eight feet from the stand to simulate the actual conditions in the chamber. Testing with this fixture provided proof of this systems ability to provide accurate alignment verification. 4.0 System Architecture 4.1 System Level View The proposed system would consist of two fixtures; the feedhorn positioning fixture, and the UUT height-positioning fixture. The feedhorn fixture will be mounted to a rigid aluminum plate and positioned outside of the chamber on a platform provided and installed by the customer. The feedhorn will extend into the chamber by adjustment of the positioning fixture in the Z-direction through an existing hole in the wall of the chamber. The UUT fixture will be centrally located inside of the chamber (Fig.9) where it will receive signals from the feedhorn. Antenna Anechoic Chamber Positioning unit for feedhorn UUT height positioning fixture Figure 9: Full system design installed in Antenna Anechoic Chamber 9 4.2 Detailed Description of Each Component 4.2.1 Feedhorn Linear Adjustment Fixture The feedhorn fixture consists of an aluminum box containing linear rails for X and Y movement, which sits on a set of rails mounted to an aluminum plate for movement in the Z direction. Figure 10: Feedhorn linear adjustment fixture. Triangular pieces of aluminum are attached to the inside corners of the box to assure rigidity. Two separate rods control the X and Y movements. These rods are ½” ACME threaded rods, which provide an adjustment of 10 turns per inch. To prevent any undesired movement of the threaded rods, two lock nuts were installed at the top and bottom of each rod. Using a standard crescent wrench to turn the rods, the feedhorn moves along two parallel linear rails in the X direction and/or Y direction. Linear bearings gliding along these rails allow for smooth and consistent motion. A brake is attached to the system, which has a clamping effect on the linear rail to prevent movement once the system has been aligned. Four additional linear bearings are attached to the bottom corner of the box. These bearings glide along the Z direction rails to allow movement of the feedhorn in and out of the chamber. Adjustments in the Z direction can be made by simply pushing or pulling the box along a set of rails mounted to a solid piece of ¼” aluminum. A hand lock is attached to two of the bearings, preventing movement once aligned. 10 4.2.2 Feedhorn Angular Adjustment Fixture Attached to the X and Y linear rails, is a system which will provide adjustment in the tilt and swivel directions (Fig.11). Figure 11: Feedhorn tilt and swivel adjustment system This system is composed of an L-bracket type angle adjustment coupled with a turntable. The back of the L-bracket mounts directly to linear bearings, which glide along X- direction rails in the X-Y adjustment box. The L-bracket is hinged by means of two dowel pins. The pins are kept in place with setscrews located on the bottom piece. The tilt adjustment is made with the turn of a custom made turnbuckle located on the side of the L-bracket. Adjusting this turnbuckle increases or decreases the angle of the L- bracket, thus changing the angle of the feedhorn. Due to its placement, this custom turnbuckle will increase the rigidity of the L-bracket. The turnbuckle will mount to the edge of both the bottom and back piece through custom made spacers. The spacer on the bottom will serve to redistribute the load from the edge of the bottom piece to the middle. This will reduce any binding in the tilt adjustment. This assembly will allow for a total of 20 degrees of movement in the tilt direction. The swivel adjustment is made through a gear system, which rotates a turntable on which the stepper motor and feedhorn assembly mounts. The turntable will mount to the bottom piece of the L-bracket by means of a dowel that will pass through the bottom piece and connect to a gear on the underside of the bottom piece. Turning the knob mounted on the 11 edge of the bottom piece, directly under the turnbuckle, will turn the pinion of the gear set and thus, the turntable. The turntable rests on three ball rollers that are mounted to the top side of the bottom piece. These rollers allow for smooth swivel movement of the turntable. This assembly will allow for a total of 20 degrees of movement in the swivel direction. 4.2.3 UUT Height Adjustment Fixture The UUT height-positioning fixture consists of two plates joined by three all-thread screws for Y-direction adjustments (Fig.12). Figure 12: UUT height positioning fixture The bottom plate will be mounted to the floor of the chamber and the top plate will be mounted to the bottom of the existing azimuth positioner (Fig.13). Existing Fixture Existing azimuth positioner Figure 13: Assembly of UUT height positioning fixture 12 Tightening and loosening nuts on three separate all-thread screws allows for height adjustment of the UUT. Because of the triangular placement of the screws, this fixture also provides small adjustments for leveling, by adjusting only one nut at a time. Visual verification of this is provided by two bubble levels mounted to the top plate of the positioning fixture. The bottom plate is made of a ¼” thick steel plate to ensure rigid attachment of the fixture to the floor of the chamber. Blocks shown are welded for the purpose of building material up to support the all thread studs. The studs are 6-inch ¾”- 10 thread. The top plate is ½” aluminum containing through-holes for the attachment of the positioner purchased by the customer. The system shown allows for a total of 2 vertical inches of movement, between 11 and 13 inches from the floor of the chamber. 5.0 Design Evaluation The deliverables of this project have been tested and confirmed to satisfy all needs and specifications of the customers to date, considering the future work scheduled for the spring semester. The total costs of the project came in approximately $350 under budget and all the deliverables were completed when scheduled. The expenses of this project have been broken down into two categories, labor and materials. Each of these categories has been separated into specific operations and components within the project. The labor costs are total estimated costs of machine time, concept development, design, as well as assembly. These costs were estimated at approximately $20/hr for student labor and approximately $30/hr for machining. Costs of materials are costs incurred throughout the project, broken down into eight different categories. The total costs incurred throughout the duration of this project are $1,141.07(Table1). 13 Description Rate Time (hrs) Total Cost Student Labor: Concept Development $20.00/hr 70 $1,400.00 Design $20.00/hr 50 $1,000.00 Machining $30.00/hr 35 $1,050.00 Assembly $20.00/hr 10 $200.00 Total $3,650.00 Materials: X & Y Direction $408.62 Z-Direction $304.64 Angles $19.49 Swivel $123.36 Tilt $0.00 UUT Side $148.90 Alignment Verification $53.70 Miscellaneous $82.36 Total $1,141.07 Overall Total $4,791.07 Table1: Total costs of the project 6.0 Future Work As of the close of the Fall 2005 semester, issues that still need to be resolved with respect to the fixtures are the attachment of the laser mount to the stepper motor, as well as the design and implementation of a lock for the turntable. Once these tasks are completed, the team will install the fixtures in the chamber and create the users manual, detailing operation of the installed fixtures. 14 7.0 Appendix Appendix 1: Bill of Materials # of units Description Vendor Item # Used for Price/unit needed Total cost Remark Savings Purchased Done X & Y Direction Linear Bearings McMaster 6374K3 x and y movement $38.61 8 $308.88 Already have 4 -$154.44 4 X Precision Shafts (rails) McMaster 6061K43 x and y movement $11.45 4 $45.80 Already have 2 -$22.90 2 X Precision Threaded Rods McMaster 99030A705 x and y adjustment $48.26 1 $48.26 Already have 1 -$48.26 ~ X Set Screw Shaft Collar McMaster 6432K16 Threaded rod clamp $0.87 4 $3.48 4 X Flange Bearing McMaster 6362K216 For threaded rod $5.13 4 $20.52 4 X Precision nut McMaster 95072A750 Threaded rod guide $23.59 1 $23.59 1 X Precision nut McMaster 1343K14 Threaded rod guide $28.81 1 $28.81 WAITING X Aluminum Stock (20x7x3/8) Alcobra NA Top/bottom of box $30.71 2 $61.42 2 X Aluminum Stock (23x15.25x3/8) Alcobra NA left/right side of box $76.74 1 $76.74 1 X Aluminum Stock (3x15.75x3/8) Alcobra NA Back x-direction $8.92 1 $8.92 1 X Aluminum Stock (3x3x1/2) Alcobra NA corner supports for box $7.80 1 $7.80 1 X Aluminum Stock (3x3x1/2) Backstock NA corner supports for box $0.00 1 $0.00 ~ X Aluminum Stock (3.25x5.5x.75) Alcobra NA x-dir rail holder 1 $11.44 1 $11.44 1 X Aluminum Stock (3.25x5.5x.75) Backstock NA x-dir rail holder 2 $0.00 1 $0.00 ~ X Aluminum Stock (2x2x2.5) Backstock NA x/y-thread holder $0.00 1 $0.00 ~ X Aluminum Stock (4x1x.375) Backstock NA x and y brake $0.00 1 $0.00 ~ X Sub Total $634.22 Z Direction Aluminum Rails McMaster 60585K43 z movement $41.10 1 $41.10 1 X Rail end caps McMaster 60585K53 z movement stops $3.18 2 $6.36 2 X Plain-Bearing guide blocks McMaster 60585K13 z movement $56.42 4 $225.68 4 X Bearing hand brake McMaster 60585K32 z direction lock $15.75 2 $31.50 2 X Aluminum Stock (36x20x.25) Backstock NA plate to mount rails to $0.00 1 $0.00 ~ X Sub Total $304.64 Angle's Dowel Pins Backstock NA Angle adjustment $0.00 2 $0.00 Have ~ X Aluminum Stock (8.5x8.5x.5) Backstock NA Bottom Angle $0.00 1 $0.00 ~ X Aluminum Stock (8.5x8x.5) Alcobra NA Back Angle $19.49 1 $19.49 1 X Sub Total $19.49 Swivel Ball Transfers McMaster 2415T15 swivel movement $4.64 4 $18.56 4 X Aluminum Stock (7x8x.375) Backstock NA Turntable $0.00 1 $0.00 ~ X Miter Gears McMaster 6843K11 Turntabel movement $30.22 2 $60.44 2 X Hook Clamp McMaster 8954A12 swivel lock $22.18 2 $44.36 2 ??? Steel Stock Backstock Meiter Geer shaft $0.00 1 $0.00 Have ~ X Spring Backstock NA Coarse adjustment $0.00 1 $0.00 Have ~ X Steel rod Backstock NA Turntable rotation $0.00 1 $0.00 Have ~ X Steel stock (Various) Backstock NA Bevel gear mount $0.00 1 $0.00 Have ~ X Sub Total $123.36 Tilt Steel stock (Various) Backstock NA Turnbuckle $0.00 $0.00 Have ~ X Steel stock (various) Backstock NA Lock down $0.00 $0.00 Have ~ X Sub Total $0.00 Antenna Side Aluminum Stock (16.5x15x.375) Alcobra NA Top plate $54.19 1 $54.19 1 X Steel Stock (16.5x15x.25) Alcobra NA Bottom Plate $72.00 1 $72.00 1 X Nuts McMaster 95505A608 Locking $6.02 6 $6.02 Hardware Store -$2.02 6 X Paint ACE NA Color for UUT fixture $4.00 2 $8.00 2 X Screws McMaster 98758A625 Height Adjustment $2.57 3 $7.71 3 X Bubble level McMaster 2160A4 Alignment Verification $11.02 2 $22.04 Hardware Store -$19.04 2 X Sub Total $169.96 Alignment Verification Laser Office Depot 343483 Alignment Verification $10.74 6 $64.44 Already have 1 -$10.74 5 X Aluminum Stock Backstock NA Laser mounting $0.00 1 $0.00 Have ~ ? Mirror Backstock NA Alignment Verification $0.00 1 $0.00 Have ~ X Sub Total $64.44 Miscellaneous 10-24 Tap McMaster 26955A37 Tapping tool $3.85 3 $11.55 3 X Shipping McMaster NA All purchased items $33.50 1 ?? Miscellaneous McMaster NA All Applications $0.00 Sub Total $45.05 Total $1,361.16 Adjusted Total $1,103.76 15 Appendix 2: Drawing Package 16 Appendix 3: Project Schedule 17