desiggn of an advanced cruise control system

DM309
Mechatronic Design and Applications
Design of an advanced cruise control system
Introduction:
Cruise control systems are fairly common place within modern cars. They operate by varying the throttle position, and either increasing or decreasing the amount of fuel or energy that is supplied to the engine in response to either a decrease or an increase in speed respectively. In conventional cruise control systems, the driver accelerates up to a desired speed and activates the cruise control which is then responsible for maintaining this speed. The cruise control is generally overridden and disengaged when the driver either accelerates, brakes or manually disengages. Generally speaking, cruise control systems are only capable of altering the throttle position, and are not linked to the braking system or the gear train of the car. A simplified block diagram is illustrated below.

Simplified block diagram
The challenge that you are faced with is to develop a more advanced, intelligent cruise control system suitable for hybrid automobiles. You are free to use any type of sensory technology available in order to make the system safer, more responsive, and more intelligent. You can for example consider the different types of road that the car will be driven on (motorways, a-roads, country roads); different countries (UK, Europe, etc); other road users; and increasing fuel efficiency, or making use of the additional features of hybrid vehicles. The aim of this advanced cruise control system will be to assume overall responsibility of the control of the speed of the car and ensure safety, with the user concentrating on pointing the car in the right direction.
The Tasks:
Individually, you are required to address each of the following:
1. Week 1: State how the cruise control could be made more intelligent. What new features could be included to improve the driving experience and make the journey more comfortable, economic and enjoyable for the driver? Using the "generalised mechatronic system" concept, identify the actuators and sensors within the energetic domain, and the processors within the information domain for the cruise control to achieve this advanced level of intelligence. Starting with the basic block diagram above, illustrate these sensors and actuators within a block diagram and state the nature (type) of the information or energy that will be flowing between them.
2. Week 2: The different roles associated with the development of the cruise control system may be designer, production engineer and user. Using these three roles establish the different functions for the cruise control, and separate these functions into bounding and defining viewpoints. Create a function-means tree of the defining viewpoints for the cruise control system with several levels. Use the standard information flow chart elements to create an example flow chart with reasonable complexity for one aspect of the operation of the cruise control system.
3. Week 3: Considering that the source of energy is a combination of either petrol or diesel, and a battery, (i.e. chemical-thermal and chemical-electrical) create a bond graph to illustrate how the power is transferred across the different energy domains. Start with a word bond graph of all components and then incorporate the appropriate standard bond graph elements. The source of energy on your bond graph should be the fuel and battery, with the energy being delivered to at least both the cruise control system, and the driven wheels, and any added mechatronic systems you identify. Include all relevant energy losses for each domain. Ignore other systems within the car not related to driving (e.g. the climate control or entertainment systems).
4. Week 4: First and Second Order Control Systems (see below).
First-Order Systems: World strongest and most responsive person championship — Pushing a weight along a flat surface.
As part of the world strongest and most responsive person competition, each competitor is required to push a dead weight along a designated surface to test their strength and responding speed. As a game organiser and designer, your task is to design a set of fair competition rules to test both the strength and responsiveness of each competitors. This simple system can be regarded as a first order system, and can be expressed as a first order system as below:
m out
dt out
The first term of the above equation represents the required force to accelerate the weight and the second term represents the friction force from the ground, which each competitor has to overcome. The friction force is linearly proportionate to the speed that the object travels. The term on the right hand side represents the external force exerted by a competitor.
For your analysis, the following data are provided for your consideration.
First set of scenarios: you have options to change the weight for competitors to push, assuming the rest stays constant:
Case Force applied on the Resistance coefficient Dead weight (kg)
system by the competitor (N) - R (N/(m/s))
1 IOOON 100 200
2 IOOON 100 400
3 IOOON 100 600
Constant force and resistance scenarios.
Second set of scenarios: you have options to change the frictions from the ground, e.g. you may choose to design and use different surfaces for the pushing track or different surfaces of the object to be pushed, assuming the rest stays constant:
Case Force applied on the Resistance coefficient Dead weight (kg) system by the - R (N/(m/s)) competitor (N)
1 IOOON 100 500 2 IOOON 120 500 3 IOOON 150 500
Constant force and dead weight scenarios.
Answer the Following Questions:
1. For each of the cases in the two scenarios, work out the following system performance measurement parameters:
• Find the time constant
• Calculate the steady state speed each competitor can reach
• Find the speed after one time constant (t=t)
• Linearly extrapolate the time required to reach full speed
2. Based on your understanding of the competition, draw a set of competition rules to test the competitor"s strength and response fairly by making the competitors as equal as possible regarding their individual weights, strengths etc.
Second Order Systems: Automobile suspension selection/design.
As a design team, you have been asked to select a spring and shock for the front suspension for a new car. Your task is to choose a suspension that will provide the best response to varying road conditions. Since many manufacturers specify their products in Imperial Units, your design team has agreed to use Imperial units as the starting point for the calculations.
After preliminary analyses and meetings with other design teams, your suspension team has narrowed your choices down to three alternative suspension designs. The three alternatives are characterised by the following spring stiffness k & damping coefficient c:
Case k (lbf/in) c (lbf sec/in)
1 160 12
2 115 31
3 90 60
Spring stiffness and damping coefficient cases.
Your team may decide on a single degree of freedom system that models only a single wheel and neglects the response of the other wheels. This therefore results in a second order system as introduced in class. The weight of the entire vehicle is 1500 kg; therefore the sprung mass supported by a single wheel is to be 1/4 of the total mass: M = 375 kg.

Mass spring damper system.
For conversion purposes: lib = 0.454kg lin = 25.4mm
Answer the Following Question:
1. Work out the undamped natural frequency (On) and the damping constant for the above cases. Your answer must be in Sl Units (meters, kilograms, etc.). Given the three cases, decide which has the best performance & state why.
Submission:
Individual solutions should be submitted to the DMEM departmental office by Tuesday 7th March (week 8) at 12pm. Late submissions will be subject to the standard departmental penalty of 5% off per day late unless suitable documentary evidence is provided. Include a statement of academic honesty — Appendix A.
Appendix A: Statement of Academic Honesty
I declare that this submission is entirely my own original work.
I declare that, except where fully referenced direct quotations have been included, no aspect of this submission has been copied from any other source.
I declare that all other works cited in this submission have been appropriately referenced.
I understand that any act of Academic Dishonesty such as plagiarism or collusion may result in

the non-award of my degree.
Signed Dated