Reference no: EM131763897
Project: Single degree of freedom systems
Details
Your project is to analyse the performance of the monster truck shown in Figure 1. For this project your analysis is to be limited to treating the monster truck as dynamic system with a single degree of freedom. You will be asked to analyse this same system in following projects using more complex models with increased degrees of freedom and other design/analysis issues as they arise.
Some data for this project is shown below (you will need to clearly specify any other data/ assumptions you make).
Total monster truck mass: 5000 kg; Axle mass (alone): 250 kg; Wheel mass (alone): 400 kg
The centres of masses in Figure 1 refer to each mass separately. The centre of mass of the truck body does not include consideration of the axle and wheel assemblies.
Analysis
Your analysis will include:
- An evaluation of suspension performance, vibrations and transients.
Minimum scope
As a starting point you will need to design/specify the suspension stiffness, damping and suspension travel based on initial research and speculations of stunts required. The design should also be informed by an interative process based on your analysis.
Your requirement here is to analyse the monster truck as a mechanical system using mathematical modelling and single degree of freedom vibration analysis. Your analysis will include:
Draw a mathematical model schematic of the monster truck.
Simplify the model to be a single degree of freedom system (vertical motion only - Assume there is no roll or pitch.). Draw the 1 DOF free body diagram and write the modelling equation.
Free vibration response.
Forced vibration. (Excited by the engine, assume a possible engine unbalance. The engine will run at speeds up to 5000 rpm.
Road surface induced vibration. Assume road speeds up to 60 kph. Assume a simplified corrugation shape (e.g. a sine wave) and a set of realistic road corrugation depths and wavelengths.
Describe resonance and determine when it will occur.
Produce plots of magnification factor and transmissibility factor.
The Laplace transform of the modelling equation. From this equation develop a transfer function describing the system. Also examine Stability criteria and produce a Bode plot for the system
Model the system in Simulink.
Add non-linearities to the spring mass model in Simulink to make it more reflective of the real situation [Keep the model as a single DOF].
Instrumentation:- Design an accelerometer based on a spring mass system that could be used to measure the vertical motion of the truck. Assume the expected road surface input functions.
Report
Your report will include:
- A draft design of a suitable suspension specifying the suspension stiffness and damping
- An evaluation of suspension performance, vibrations and transients.
- Addressing all the Reflection and Discussion points below
- also see the feedback sheet points to check you have included everything you need in the report
Reflection and Discussion
Present and discuss the differences between real and idealised models.
Compare with your Bode diagram with plots of magnification factor and transmissibility factor.
Reflect on the differences, advantages and disadvantages of frequency domain analysis (Laplace, frequency response etc) verses time domain (simulation, time series output etc).
Reflect on your final suspension design. i.e. Do you think the spring - damper combination selected is suitable? How could it be improved? What method/steps would you do to improve it? Would you have done anything different if you were to redo the design/analysis?