The project is intended to emphasize proper project management and team skills to produce a complex engineering system from concept to completion.
Cranes are used to move large loads in industrial environments. To do this they normally lift a load and then move it to a new position. At the end of the motion the load is put down. If the load is swaying, the operator may have to pause before putting down the load. This delay is undesirable because it increases the total cycle time for the crane.
This design project will endeavor to build a proof-of-concept prototype for an anti-sway system for a gantry crane as shown in Figure 33.1 The equipment. The crane will ride on a wooden beam constructed with 2x4 lumber (actually smaller). An electric motor will drive the cart left or right. The mass will hang below the cart.
Figure 33.1 The equipment
The system will use active compensation to move the cart between positions, and to move the cart to compensate for swaying of the suspended mass. The overall system performance will be evaluated on how quickly the crane can move the load, and then eliminate sway. Additional factors used in assessment of performance will be the mass, cost and overall design quality.
The design will be mounted on 2x4 lumber and controlled through a wire harness to external electronics and power supplies. The apparatus must be easily mounted and removed without damaging the experimental setup. It will be expected to carry a 1Kg mass, suspended 40cm below the top of the 2x4. The 2x4 will be oriented so that the longer dimension is vertical. The mass will be mounted with a carriage bolt that is at least 3 inches long, with a 1/4" diameter. The arm must be able to swing freely, as it is meant to be equivalent to a cable suspending the mass. The mass will be provided with a rod that will be between 1/4" and 1/2". The mass will be a cylinder that is free to rotate to reduce dynamic effects rotation. The width of the mass will be less than or equal to the width of the 2x4. None of the cart, except for the arms, should be less than 2cm below the bottom of the 2x4.
The objectives for the design are itemized below. The following equation will be used to assess the overall score for the design.
- The equipment cost should be minimized. The goal of $150 or less has been specified as very important.
- Mass should be minimized, the target value is 0.2Kg.
- A clearly justified and supported design process. This will be judged before the competition.
- The settling time, ts, to less than a +/- 0.5 inch margin around the commanded position. This time will be determined using the best ts/d for two arbitrary target motions.
- The test will start with the mass stationary at one position. The gantry system must move the mass to another position once started. The total movement range will be 2 to 20 inches in 2 inch increments.
The management details for the project are outlined below. These may evolve as the semester progresses.
Sept 12 - Teams assigned
Sept 12 - Teams matched with EGR 101 students
Sept 14 - EGR 345 Teams visit EGR 101 lab - EC616 (6pm) to formalize contracts
Sept 16 - Contract submitted
Oct 4 - Preliminary design concept submitted with specifications
materials list estimate
budget estimate
Gantt charts
Oct 13 - Design concept approved
Oct 24 - Proposal submitted
detailed drawings (CAD)
materials list
budget
calculations/simulations
Oct 29 - Proposals approved, 345/101 building begins
Nov 12 - First test
Nov 19 - Second test
Nov 20 - First draft of report posted to the web used to determine the score for competition
Nov 25 - Competition and judging
Dec 4 - Final report draft posted to the web
The teams are composed of up to 4 students from EGR 345 and one student from EGR 101. The EGR 345 teams are grouped using the skills survey attached in the appendices.
Teams are expected to divided tasks for members to work in parallel. It is also expected that team members will review the work of others to ensure accuracy and completeness. This is particularly true of calculations, materials lists drawings and budgets.
All team members are expected to work in a professional manner. The general rules of conduct in a team are,
- treat others as you want to be treated
- communicate expectations and problems clearly
- be polite and accommodating
- when problems arise, help to solve them, even if they are not your fault. Don't lay the blame for problems on others.
Personal conflicts must be resolved by team members in a professional manner. The performance of the team will be assessed using peer evaluations on a regular basis and may impact individual grades. In the case of non-participation the penalty may be up to 100% of the project grade.
In the event that team members cannot resolve differences with a team member, the team may 'fire' the team member by a vote (it must be unanimous, except for the member in question). In this case the 'fired' student is responsible for finding another team that will accept (or 'hire') them. In the event they cannot find another team to join, they will be expected to perform all of the work themself. The firing mechanism is intended to deal with individuals who 'harm' the progress of the team, not for non-participants.
The following items are to be submitted at various stages of the project.
Concepts are normally communicated with sketches that make the overall design clear. Components that would be expected for this type of design are,
- Sketches should be done using normal drafting practices. A good set of sketches will include 2-D, isometric and pictorial views.
- Calculations should be provided that support the design concept.
- Electrical schematics to describe the control system.
- Block diagram to describe the control system.
- Lists of components and budgets to indicate the major parts of the system.
- Other items, such as flowcharts, are often required to clarify the design concept.
This project involves participants from EGR 101 and 345. Although the students are at different points in their academic careers they are all considered peers, and should have equal voices in the team. To help clarify issues of differences between the EGR 101 and 345 students, a 'contract' will be written that formalizes the responsibilities of the students in EGR 101. As with most contracts, it outlines a process that is mutually beneficial. In this case both parties are expected to benefit in an educational sense. The contract will be written in such a manner that if all requirements are satisfied work will be marked 'as-is'. In the event of a failure, marks will be deducted to hold the responsible party(s) accountable.
Teams are expected to submit progress reports on a weekly basis. These reports will include the following elements divided into sections with a heading for each. Point form is preferred, but complete sentences must be used. (Note: 'Parts purchased' should be 'Parts were purchased for the cart assembly.') Each section should include items completed since the last report, and current action items. If there is nothing to be said about a category use 'no changes', 'nothing done', or 'complete' as appropriate.
Cover Page - a cover sheet indicating the course, project and tema numbers. The names of all team members should be listed on the cover, including the EGR 101 team members.
Gantt chart - updated on a weekly basis and included each time.
Budget - when changes are made, include an updated budget.
Mass Table - when changes are made, include an updated mass table.
Design - Design changes should be indicated. Appropriate drawings, schematics, or equivalent should be included. When appropriate, these should normally be accompanied by a new set of models, calculations and/or simulations to verify the new design.
Software - The current status of software development should be indicated, including major accomplishments and issues.
Fabrication - The status of items being built/assembled should be indicated.
Purchasing - The status of ordered items should be indicated.
Testing - The testing progress should be indicated, including any numerical results when available.
Other Issues - Items that may impact the success of the team should be indicated.
Performance - A prediction of performance, including the overall performance equation.
Early in the semester, other items will be requested, such as a combined timetable for all team members, and a skills inventory. These should only be included in the reports the weeks they are requested.
The design proposal is used to present all of the design details in a single document. The focus of this document is a MINIMAL AMOUNT OF TEXT, but a thorough presentation of the design details. Typical elements are listed below in a typical sequence;
- a cover page indicating all of the team members and all other pertinent information.
- a table of contents
- three view drawings of each significant part
- block diagram of the control system
- block diagrams showing the system architecture
- circuit schematic
- if a motion profile will be used, it should be documented
- an assembly drawing of the mechanism, including a BOM
- a budget listing each of the parts that must be purchased/acquired. Catalog pages and quotes can be used to validate the budget. In the final report, copies of receipts, or catalog pages will be required.
- a weight inventory, itemized by each part of the design
- additional calculations for mechanical design issues, such as stress that may result in failure. Normally these result in a factor of safety.
- the equations of motion for the system
- a Scilab program that verifies the operation of the system using the equations of motion.
- a C program that implements the controller as designed.
The final design will follow the same structure as the Design Proposal, with the addition of the following elements.
- test results
- the drawings, calculations, etc. should be based upon the final design. It is reasonable to write a page or less about the modifications that were required, but it is a minimal/optional part of the report.
The report should concisely and clearly describe the design, as shown in the diagrams, drawings, calculations, etc. In general the format of the report is as outlined below. Sections and subsections should be numbered.
Cover page
Executive summary - one page or less that summarizes the design and results.
Table of contents
Design description - this section should describe the mechanical, electrical and software design aspects. Subsections should focus on the following elements;
Drawing summary - selected isometric and assembly drawings
System block diagrams
Description of control scheme, such as the motion profile
Schematics
Calculations - FBDs and differential equations
Project budget and BOM
Weight inventory
Test results - this section should describe
Simulation results
The tests that were done to describe the overall performance. There should be a comparison of the device with and without sway compensation.
The results of formal tests should also be described.
A comparison of overall score estimates.
Conclusions - A brief description of the overall results indicating what the strengths and weaknesses of the design.
Reccomendations - Suggestions for improvement.
Appendix - Drawings
Appendix - Stress and other similar calculations
Appendix - Controller C program
Appendix - Simulation program
Appendix - Receipts and cost evidence
Final reports will be evaluated on numerous factors inculding the clarity for the design documentation (i.e., how clear is what has been done?), theory to backup the design (does the theory match the actual design?), did the theory and actual match?
Gantt charts are used to track major project tasks, including sequencing. a brief tutorial on project management with Microsoft Project is available at http://www.stylusinc.net/ms_project_tutorial/project_management.shtml. You may also download free project management software from http://www.smartworks.us/htm/downloads.htm. In general a Gantt chart should include,
- Most project parts should have a development, and then a review stage by another team member. For example, if one task is preparing mechanical drawings, this should be followed by a review task - done by another team member.
- Most tasks that stretch more than a week should be broken into smaller sub tasks.
- A Gantt chart should be presented on one single sheet. If it is small enough this can be one page, otherwise a larger sheet can be used.
- On a weekly basis a Gantt chart should be updated to include the completion of tasks.
All drawings will observe the standards used in EGR 101 (see the EGR 101 or 345 course pages). This includes dimensions and tolerances that can be produced using the available equipment and materials. Please note that 'sketch' means that it is done by hand, approximately, while drawing means it is done formally in a CAD package. Normally you should create solid models, and then generate multiview drawings. Note: All drawings must have a title block.
Shaded views have very little value and should be avoided, wireframe drawings are much more useful. If there is a definite need to include a shaded drawing, change the background to change the quantity of toner used.
Budgets should list all substantial components. Consumables, such as bolts are normally listed under a 'miscellaneous' heading. However, all other components should be listed, and prices provided. If the components have been drawn from the engineering stores, similar devices can be identified from catalogs and those prices may be used. If your design calls for parts not commonly issued to engineering students, you may be required to purchase these yourself. An excellent local source of small parts is hobby stores, such as Ryder's Hobbies on 28th St. The budget should also list the quantity of parts/material, price, source/supplier and status (eg., not ordered, received, due 2 weeks, late 1 week).
Don't forget to include cost of the controller and other components used. Assume the power supply is provided as part of the crane system and therefore has no cost is associated. Some of the commonly available components are listed below. List simple commodity items such as wires, bolts, etc., under a miscellaneous category with a general cost estimate.
68HC11 Axiom board $89
Grayhill encoder est. $8
Power Supply, list it but do not give a price
Gearhead motors assume $10
A Bill of Materials (BOM) lists all of the parts required to produce or assemble some other device. This is different from parts listed in a budget in that some of the parts will be work in process. In other words, the original material has been worked on to produce new parts. A BOM is normally found on assembly drawings.
Notes;
- there are different type of plastic, some are more brittle, others are tougher.
Calculations are required to justify the design work. These should follow the conventions used in EGR 345. When computer programs are written, they should be commented and included.
The example system in Figure 33.2 System Architecture is to control a cart with a hanging pendulum. The cart is driven by a motor. The motor has an attached encoder to measure the motor position. As the cart moves the mass underneath may sway. The position of the hanging mass is measured with a potentiometer.
Figure 33.2 System Architecture
A block diagram for the system is shown in Figure 33.3 System Block Diagram. A motion generator is used to generate a smooth path for the mass. There are two feedback control loops. The first loop adjusts the motor for general positioning of the system. The inner loop adjusts the output to reduce sway of the cart. The two control signals are added to produce a command signal the drives the load to the final position and then reduces vibrations.
Figure 33.3 System Block Diagram
- for a stationary cart
Figure 33.4 FBDs for the suspended mass and the compensator
Figure 33.5 Adding the differential equation for the motor
Figure 33.6 State equations for the system
A Scilab program that simulates the given system is given in Figure 33.7 A Scilab program to simulate the swaying mass on the crane.
Figure 33.7 A Scilab program to simulate the swaying mass on the crane
Figure 33.8 A Scilab program to simulate the swaying mass on the crane
Figure 33.9 A Scilab program to simulate the swaying mass on the crane
The text below outlines the general form of a contract between students in EGR 101 and 345.
This contract has been entered into this date by the parties of the first part Joe Junior, Pete Zaa, Anne Nyther and Robert Sochs, to be referred to as '345 students', with Virve Meurte, to be referred to as '101 student(s)'.
Articles:
1. The 101 student is to participate in the design and construction of a cart as outlined below. The 345 students are to prepare a design and construct a multicomponent system that uses the cart as described below. The result must be a fully functional systems that meets the published design objectives.
2. The 345 students are expected to prepare a functional design for an anti-sway system for a crane. This design will include a cart that is designed in coordination with the 101 student. The 345 students will be required to do all calculation including system dynamics and strength of materials. The 101 student will be responsible for all other design details related to the cart including the geometry, mass, budget bill of materials and construction. This design will be documented fully by the 101 student using accepted CAD practices and ProE. The design work will result in the submission of a Formal Proposal, as shown on the Schedule of Actions.
3. Dr. Jack and/or Farris will comment on the Formal Proposal. Based upon these comments the 101 and 345 students will revise the design and agree upon a design for the cart. This will be labelled Cart Build Approval. This will be signed by all parties and submitted to Dr. Farris by the Scheduled date.
4. The cart will be build according to the Cart Build Approval before the date specified on the Schedule of Actions. At the end of this period the design must be fully documented in ProE and be ready for inclusion in the Design Report Draft.
5. Both the 101 and 345 students will participate in the first tests to verify the operation of the system and develop a First List of Deficiencies. This list will be finalized and signed, according to the date on the Schedule of Actions. The First List of Deficiencies will include a list of remedies to be performed by the 101 and 345 students.
6. The 345 students will prepare the Design Report Draft using the ProE drawing submitted by the 101 student. They are responsible for submitting the report by the date in the Schedule of Actions.
7. Both the 101 and 345 students will participate in the final tests to verify the operation of the system and develop a Final List of Deficiencies. This list will be finalized and signed, according to the date on the Schedule of Actions. The Final List of Deficiencies will include a list of remedies to be performed by the 101 and 345 students. Any changes made to the design must be updated and submitted to the 345 students for inclusion in the Design Report.
8. Both the 101 and 345 students will participate in the Competition listed in the Schedule of Actions.
9. The 345 students are to submit the final report with all necessary changes by the date listed in the Schedule of Actions.
10. The 101 student is expected to produce a cart that is built to professional standards. All drawings are expected to observe professional standards. When communicating drawings, generally accessible files formats should be used.
11. The 345 students are to, at all times, maintain a functional design concept. They must ensure that this will lead to a system that functions within the rules of the competition.
12. In the event of a dispute, 101 and 345 students are expected to resolve any conflicts informally and mitigate any losses. In the event that one or both parties fundamentally breach the contract Dr. Farris and Dr. Jack will acts as arbiters. If this occurs, one or both of the parties will be penalized. This may involve actions as severe as receiving a failing grade in the project.
Exhibits:
1. Schedule of Actions
Oct 15-24 - Cart designs are developed by 101 and 345 students
resulting in submission of the Formal Proposal
Oct 30, 2003 - Cart Build Approval submitted
Nov 11 - Initial build completed
Nov 12 - First test completed and First List of Deficiencies submitted
Nov 15 - Design Report Draft submitted for review
Nov 19 - Final test completed and Final List of Deficiencies submitted
Nov 25 - Competition
Dec 4 - Submit Final Report
Skills Self Evaluation
Peer Evaluations