Assignment Cover Sheet
Maximum 3000 wordsfor the assignment
Where to submit assignment reports: Electronically in Brightspace
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In submitting this assignment, students should be aware of the following:
- Unless there are extenuating circumstances, work handed in after the hand-in date will receive a mark no greater than 40%; if handed in after the cut-off date (1 week after the hand-in date) the mark will be 0%.
- Student Handbook of Regulations: including the procedures for students wishing to claim extenuating circumstances and the definition of plagiarism and the procedures and penalties for dealing with it.
- You are advised to keep copies of all your assignments in case of difficulties.
This assignment will NOT be marked unless the following section is completed
Student name: |
Student number: |
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Module title: |
Module number: |
Module tutor: |
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| DYNAMIC ANALYSIS & CONTROL | |||
Assignment title: |
Weighting: |
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| DESIGN & ANALYSIS OF A CAR SUSPENSION | 50% OF MODULE | ||
Date due: |
Date submited: |
Word count (approx.): |
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| 21/03/19 | |||
PERFORMANCE FEEDBACK (to be completed by the module tutor)
Feedback due date:24/04/19
| Assessment criteria (See assignment spec.) | % Weight | Grade | Summary Comments: |
| 1 | 20 | ||
| 2 | 20 | ||
| 3 | 20 | ||
| 4 | 20 | ||
| 5 | 20 |
Overall Grade: …………….
Tutor’s Signature:
Design and analysis of a car suspension
Background
Figure 1 shows basic design of the double wishbone suspension, which is widely used in sport car design and manufacturing. In this type of suspension, the wheel is suspended by a shortupper arm and a long lower swing arms combined with springs and dampers. Double wishbone suspension allows to provide an optimum compromise between handling and comfort.
Figure 1: Double wish bone suspension
Tasks
This is an individual assignment which comprises of five sections:
- The first element is to conduct research into the geometry of a typical double wishbone suspension and specify a typical wheel diameter and sprung mass.
- The second element of the task is to model, calculateand drawdisplacementtransmissibility ratio diagramfor a car with mass 1000 kg, the spring constant is 100000 N/m, but varying damping constantto be 1000, 2000, 3000, 5000 and 10000 N.s/m.
(Tips: you can use a quart car model as shown in Figure 2. The transmissibility ratio diagram should look like Figure 3)
Figure 2 A quart car model
Figure 3
- The third element of the task is to use Adam/view to simulate and validate your suspension with the same conditions as above.
- The fourth element of the task is to compare both results in term of relative and absolute errors if there are any, and discuss your results. You may analyse it by varying your specified values. You may optimise your design and consider other issues like contact problems between tire and road.
- The fifth element of your task is to analyse the behaviour of the suspension under motorway conditions. If the suspension can be modelled as a spring-mass-damper system with an equivalent weight, stiffness, and damping constant of 10000 N, 400,000 N/m, and 10000 N-s/m, respectively. The differential setting of the concrete blocks on the road caused the level surface to decrease suddenly, as indicated in Fig. 4. If the speed of the car is 5 m/s (18 km/hr), draw the displacement of the car in the vertical direction when it travels from t=0 to t=3s. Assume that the car is free of vertical vibration before encountering the step change in the vertical displacement.
Figure 4
If you are required to modify the spring and damping constants for the suspension, what values could you recommend? You should try to ensure that the suspension you have designed will provide aproper comfort for the rider in term of suspension vertical displacement, velocity and acceleration.
Scope
Some tasks may be suitable for hand calculations, whilst others may be suitable for multi-body software analysis. An integral part of this assignment is being able to choose the most appropriate analysis methods. You should justify your choices, and state any consequent compromises that result. You should accompany your simulations with hand calculations where possible using either MATLAB or EXCEL to plot appropriate graphs.
Marking criteria
The brief is deliberately quite open, and you will receive higher marks if you support and justify your design with appropriate research. Higher marks will also be given for novel solutions, as long as those solutions are valid and justified. Higher marks will be awarded for models with an appropriate level of complexity. Over complex models that add little to the accuracy of the solution will not attract higher marks, nor will over simplified models that sacrifice accuracy.
Module outcomes addressed
This assignment allows you demonstrate the outcomes (1), (2), (4) and (5) of the module:
1) Have a systematic understanding of how to model and analyse vibrating systems.
2) Be able to deploy accurately established techniques in order to analyse and synthesise planar and spatial mechanisms.
4) Apply vibration reduction methods to solve problems involving mechanical vibrating systems.
5) Use computer software packages to critically evaluate mechanisms and vibrating systems.
Time required
You should expect to spend approximately 48 hours on the computer to complete the modelling element in addition to the 12 hours of timetabled laboratory time. The final write up should take 12 hours.
Deliverables
- An electronic copy of your ADAMS (.bin) model delivered to the Brightspace assignment submission folder before midnight on the hand in date.
- An electronic PDF copy of your report delivered to Turn-it-in in Brightspace before midnight on the hand in date. Please convert your report to PDF and ensure that it has converted properly beforesubmitting to Brightspace. Please note the report will automatically be checked for plagiarism, therefore ensure that all of your sources are correctly referenced.
Marking scheme and assessment criteria:
Research: ——————————————————————————————————– 20%
A pass mark will be awarded where basic research into the geometry of suspension has been completed including identifying the wheel diameter and sprung mass. Higher marks will be awarded for in-depth research, critical analysis of designs and consideration and investigation into the influence of the tyre on the system dynamics.
Suspension modelling and calculation: —————————————————————- 20%
A pass mark will be awarded where the proper formulas have been used tocalculate with minor modifications. Higher marks will be awarded where the correct, accurate and multiple degree model has been used. Comparisons should be made between the design and your research.
Validation by Adams view simulation: —————————————————————– 20%
A pass mark will be awarded where the springs and dampers have been selected to satisfy the design criteria using hand calculations combined with justification. Higher marks will be awarded for a detailed systematic analysis which results in a considered design choice.
Road excitation drawing and selection k and c values——————————————- 20%
A pass mark will be awarded where an appropriate drawing has been made and there has been an attempt to investigate the response with differing speeds. Higher marks will be awarded where there has been a detailed analysis of the suspension response and the optimised k and c values have been recommended. The results should be compared to theory with appropriate discussion.
Presentation: ————————————————————— ———————————— 20%
You will obtain a pass mark if you submit a neat report divided into appropriate sections. For higher marks your report must be well structured and written. A professional level of engineering prowess has been demonstrated.
