KGCOE MSD Technical Review Agenda P11213: Land Vehicle for Education: Modular Student Attachment

Transcription

1 KGCOE MSD Technical Review Agenda P11213: Land Vehicle for Education: Modular Student Attachment Meeting Purpose: 1. Introduction and review of the project 2. Design project recap 3. Mechanical design and analysis 4. Control design and analysis 5. Electrical design and analysis 6. Bill of materials Materials to be Reviewed 1. Project description 2. Torque analysis 3. Power consumption analysis 4. Feasibility analysis 5. Design layouts and schematics 6. Part drawings 7. Preliminary Test Plans Meeting Date: February 11, 2011 Meeting Location: Meeting time: 3:00 5:00 pm

2 Project # Project Name Project Track Project Family LVE : Modular Student Attachment Vehicle Systems Land Vehicle For Education Start Term Team Guide Project Sponsor Doc Rev Phil Bryan Dr. Hensel 1 Project Description Project Background: The land vehicle for education, or LVE, is a vehicle designed specifically for use by first year mechanical engineering students. The objective for those students is to design a system to complete a certain task. By using the LVE and specifically designing portions of the Modular Student Attachment, or MSA, students will gain valuable design, CAD and machining experience. Problem Statement: To develop a small robotic vehicle used by freshmen as a portion of a project as part of a first year course. This course emphasizes the design aspect of mechanical engineering. Specifically for the MSA: To develop a platform/system that will be the focus of the design for the first year students. Objectives/Scope: Ensure MSA compatibility with the overall design of the LVE Design an example MSA to exhibit a possible outcome of student design Deliverables: Instruction for MSA design/use Development of possible future uses Example MSA Implementation Expected Project Benefits: The LVE, and more specifically the MSA, will help mechanical engineering professors teach first year students the basic principles of design and fabrication. The LVE and MSA should be designed in such a manor to cause others to emulate its design. Core Team Members: Dylan Rider Oyetunde (Dan) Jolaoye Andrew Komendat Jared Wolff Strategy and Approach Assumptions & Constraints: The team should have a good understanding of the first year course that this project will be ultimately used in. The team must also be cognizant of the budget constraints imposed upon the project. Above all, this project must be completed and be ready to be used by Fall Issues & Risks: Open ended design that must accommodate future possible projects. The interface (mechanical and electrical) between the LVE chassis and controls Ensuring that the design of the MSA can be altered by first year ME students.

3 Design Project: The goal for the students in the class will be design of a 4-bar linkage system with an end effector to manipulate and locate objects for a given height. The students will be responsible for geometric analysis, creating CAD models to interface with components provided for the project (servos, mounting devices, end effector, etc ), and manufacturing the components they produce to at the end make an operating device. Figure 1: MSA Concept Sketch Figure 2: Preliminary MSA CAD Model Mounting Platform: The selection of the MSA platform was selected based on provided mounting locations from the LVE chassis team. A flat platform with four bolt holes was selected. The MSA mounting board uses ¼-20 thru holes and bolts for mounting components to it. The holes are not threaded

4 because the material (Acrylic) does not favorable support tapped holes. Standoffs were selected to allow this added height, and ¼-20 bolts were used in the mounting to the LVE chassis. Figure 3: MSA Mounting Plate Figure 4: Mounting Plate Stress Analysis

5 Figure 5: Mounting Plate Deflection Analysis Plate material was chosen to be sheet Acrylic (plastic), 0.25 thick. This was based off hand calculations for bending and shear stress as well as finite element analysis in ANSYS, with a load of 25 pounds, a load 5 times anything expected on the MSA current design. Servo Mounting: The servos will be mounted to the plate using an L bracket piece. The bracket will have a punched hole through which the servo will feed, and mounting thru holes for both mounting to the plate and servo. Servo Selection: The selection of a servo was the most critical parts of this design. A servo with too small of power will not sufficiently operate in real application. As a result, careful torque calculations over the specified range were obtained using Matlab code. Detailed analysis will be provided and explained during the presentation, but the analysis really focuses to show that a range of geometric orientations can be incorporated to student designs. It also indicated design limitations the students will encounter in their designs which they will have to account for.

6 Figure 6: Torque Requirements, Square Setup Figure 7: Torque Requirements, Alternate Geometry

7 Figure 8: Torque Requirements, Alternate Geometry Results from analysis indicate that the inflection point (point of maximum extension) will be a limiting factor for designs, and is difficult to account for, but is inherently taken care of by design expectations for preventing a locking up scenario. Figure 9: MSA Servo Selection The final servo selection was based off the cost limitations of the project. An increase in servo output would improve the speed of responses. Link Material: The links are expected to be made by students, using a common 6061 Aluminum Alloy. The pieces will be 0.25 thick by 0.75 in width for ease of machining during the manufacturing process. By observation these parts were determined to be sufficiently strong to handle any load supplied in this project.

8 Figure 10: Link Design Example Pins: Pins will be provided as clevis and cotter pins, measuring as 0.25 diameter thru holes. This was selected in place of screws and nuts to prevent nuts from unscrewing during operation. Spacers can again be used between links to prevent binding in the setup. If budget were to allow, eventually a press fit bushing or bearing would be an upgrade at this location. End Effector: The end effector selected is an entire end effector assembly that will be purchased online. The kit contains the servo, and opens and closes with two grippers in the horizontal plane. The range of motion allowed varies from 0 to 4 inches of range. Figure 11: End Effector Control Board: The controls for the MSA are located separate from the main control board. The board will contain onboard power regulation, serialized connection between the MSA and main control board, signal processing through the daughter board, and outputs.

9 Figure 12: Control Feasibility Figure 13: MSA Control Board Layout Top Figure 14: MSA Control Board Layout Bottom

10 Figure 15: MSA Control PCB Schematic A Figure 16: MSA Control PCB Schematic B Power Regulation: The MSA controls and servos operate on a lower voltage than nominally supplied to the control board. As such power regulation was examined and incorporated to the design. The following displays a test chip for observing the operation of the power regulator chip selected.

11 Figure 17: Power Regulation Test Board Figure 18: Regulator Thermal Analysis

12 I/O Interfacing: The Outputs from the control board will pass through the wall facing the MSA board using a 3D printed shroud and header pin locations. The typical servo interface has three pins and wires, and the board will be created to accommodate numerous inputs and outputs in the MSA. Figure 19: I/O Port Shroud Power Consumption Analysis: The MSA motor power consumption was analyzed as shown below. The minimum values of battery life are based off worst case scenarios for the MSA servo motors, which should not be expected under a normal operation. Figure 20: Power Consumption and Feasibility Serialization Interface Analysis: The transfer of control data from user input will be through headers using UART protocol. The protocol was selected based on ease of use and the range of capabilities for expansion.

13 Figure 21: Serial Interface Analysis Important Note: It s important to note that the MSA contains two distinctly different parts that can be obtained and used interchangeably. The internal components of the MSA (control board, power regulation, I/O pins, and control connections) can be purchased and used on a per LVE basis. The external components (servos, mounting components, links, and end effector) can be purchased and used separately. The same LVE can be used by several class sections by simply removing the MSA portion of the system. Bill of Materials: The materials selected include both the main components and materials for student design broken down by per MSA cost and by bulk cost.

14 Figure 22: Bill of Materials The only parts currently in question are proper bolt sizing for end effector mounting as schematics of patterns are unavailable, and servo mounting hardware if the included hardware appears insufficient. Preliminary Test Plan: The test plan will accommodate to assure that the components purchased operate in a manner that was expected of the MSA. This includes component tests to be performed before the complete MSA design is constructed.

15 Figure 23: Preliminary Test Plan Risk Mitigation: Throughout our designing steps were taken to minimize the risks of failure for the project. Shown is a list of the risks we deemed most in danger of preventing full functionality of the MSA.

16 Figure 24: Risk Analysis Closing Comments: We plan on continuing to put forth our best effort over the coming months to provide the Mechanical Engineering Department with a product for freshman engineers that stimulates thought of design aspects found in real world applications while allowing the introduction and growth of necessary skills