Motivation:
Tire pressure inflation system is finding its place in most of luxurious vehicles. This systems ensures the ride safety as accurate tire pressure plays an important role in increasing the safety and comfort of the ride. Improper inflation of tires increases tire wear rate drastically and reduces braking efficiency. Improper inflation also increases the stopping distance and hence involves the risk of the accidents.
Fact image reference: http://www.quincycompressor.com/the-importance-of-tire-inflation/
Concept:
To address the problems caused due to improper inflation, a semi-active tire inflation system can be implemented which monitors the road conditions indirectly with varying vehicle speed and maintains the required inflation within the tire. System will increase grip of the tires and enhance braking efficiency by regulating tire pressure with respect to vehicle speed.
Working Methodology:
In order to make a complete semi-active inflation system speed of the vehicle need to be checked continuously & required tire pressures need to be maintained accordingly. For an example the tire inflation should be less than or equals to 22 psi at the low vehicle speed where as inflation of 32 psi is maintained at higher vehicle speed in order to achieve good grip between tire and road. Hence the system will provide sufficient arrangements of various equipment to maintain required inflation in all the tires of vehicle.
Flowchart representation of the concept and working of the semi-active tire inflation system.
Pressure Vessel Design & Analysis:
Assuming efficiency of joint 100%
Factor of safety = N = σmax/ σworking
Where, taking N = 2 as the system shall work under dynamic conditions.
σsafe= σmax / N = σallowable for material ....... (1)
Where, taking N = 2 as the system shall work under dynamic conditions.
σsafe= σmax / N = σallowable for material ....... (1)
Choosing Polypropylene (PP) plastic material to store compressed air, which has following properties:
Elastic Modulus=179E7 Pa
Mass Density=933 kg/ m^3
Tensile Strength=33E6 Pa
Compressive Strength=393E5 Pa
(Source: Solid-works 2014 x64 student edition material library)
Elastic Modulus=179E7 Pa
Mass Density=933 kg/ m^3
Tensile Strength=33E6 Pa
Compressive Strength=393E5 Pa
(Source: Solid-works 2014 x64 student edition material library)
Calculating safe compressive stress for given material:
Thus, σsafe= 16.5 Mpa
Thus, σsafe= 16.5 Mpa
For internal pressure, ρ = 100 Psi
∴ ρ = 0.6894 MPa ,
ρatm = 1.01325 bar = 0.1013 MPa
∴ Δ ρ = ρ – ρatm=0.588075 MPa
∴ Taking, Internal diameter (di )=50 mm & Thickness (t) = 3 mm;
t/d = 0.05 < 0.1 (Hence thin cylinder)
∴ σh= Δpd / 2t = 4.2400625 MPa & σl=Δpd / 4t = 2.4503125 MPa
∴ ρ = 0.6894 MPa ,
ρatm = 1.01325 bar = 0.1013 MPa
∴ Δ ρ = ρ – ρatm=0.588075 MPa
∴ Taking, Internal diameter (di )=50 mm & Thickness (t) = 3 mm;
t/d = 0.05 < 0.1 (Hence thin cylinder)
∴ σh= Δpd / 2t = 4.2400625 MPa & σl=Δpd / 4t = 2.4503125 MPa
and shear Ʈmax= ( σh-σl)/2 = Δρd/8t = 0.894875 MPa
Here, σh , σl , & Ʈmax all are less than σsafe
∴ Design is safe.
Here, σh , σl , & Ʈmax all are less than σsafe
∴ Design is safe.
Flow simulation of the wheel:
In order to locate the proper mountings and to check the real time situations we can use the flow simulation shown here using CAD/CAE software, I have performed the following analysis which shows the pressure distribution over the tire as the air passes over the wheel while vehicle is running at speed of 50 Kmph in X direction (towards origin).
First figure shows streamline flow of air over the complete wheel with pressure distribution whereas the second figure represents the cut plot to visualise the pressure distribution at exactly mid plane.
This goal plots represents the detail of information that can be extracted using flow simulations. We can visualise some of the drastic changes within the normal forces and that can be very helpful in predicting the ride dynamics.
Use of Micro-controller:
A controller based actuation system is required to continuously read the variables such as speed and pressure and to interpret the action that need to be taken accordingly. I tried to use an open source micro controller Arduino UNO. It is probably the best to start with because of easiness of the Arduino IDE, and a worldwide helpful online community. Coding is easily done and the controller can be mounted on the vehicle with small kit, adding negligible weight at the vehicle level.
Use of other Hardware:
As a hardware kit one need to use several tools to work as a complete pneumatic system to supply and retrieve the air from source & the sink. I have used 3-way solenoid valve to control the air flow with the help of micro-controller along with the small air tubes to control air flow till it reaches where it needs to be delivered.
Conclusion:
The proposed method of using semi-active inflation system can help in monitoring and regulating tire pressure while vehicle is in running condition. As a result better ride comfort and higher braking efficiency can be achieved by maintaining proper inflation of the tires.
Also, I have interpreted the speed of the vehicle as the indirect indication of the road conditions. Say for an example, user will move slowly over bad road condition and will try to go fast on smooth roads. Thus by interpreting speed as an indirect measure of road condition, one can also achieve indirect suspension at wheel-road interface because under inflated tire at bumper impact will reduce the jerks experienced by suspension system and minimum vibrations will be transferred to the passengers.
Future Work:
One can still expand the idea to compress the hardware system for mounting purpose. Wireless modes can be developed between wheel mounted components and remotely located components to work in harsh environments.
Plagiarism Report:
A plagiarism report was generated for the work done using the facility available at VIT University, Chennai.
Thanks for your valuable time..!
