Centre of gravity:-
Center of gravity
Centre of gravity is a point where whole mass of the body lies, we can say its centre of whole mass, there is a formula to find centre of gravity of any given object.
Consider a object A whose centre of gravity lies at (x, y)
So to get (x, y)
Where
Xcm=Centre of mass at x
Ycm= Centre of mass at y
m1, m2, m3, are masses at x1,x2,x3 distance & y1,y2.y3 distance, it's a graphical representation of masses with respect to their distances.
- Why centre of gravity is important in robot designing?
- When robots are working they should not toppel, centre of gravity shows whether the object is stable or unstable.
- When robot is on inclination it's centre of gravity changes if you want it didn't topple make sure that centre of gravity always remain between the wheels.
- Some diagrams to explain where centre of gravity should lie in robots.
- Note:- Wheels near centre of gravity should be Gripped.
Friction Analysis
In this blog you will learn about Friction and its analysis, derivation of coefficient of friction.
Types of friction:
- Dry Friction
- Fluid Friction
Further dry friction is divided into two types:
- Static Friction
- Kinetic Friction
How to calculate value of friction?
How friction helps us in our daily life?
Daily life examples of friction.
— Friction is
the force resisting the relative motion of solid surfaces, fluid layers, and
material elements sliding against each other.
— A
resistance encountered when one body moves relative to another.
— A
force on objects or substances in contact with each other.
Note: - Forces of action reaction between contacting
surface act normal to the surface.
Examples of friction in our daily life
— Rubbing
both hands together to generate heat.
— Iron
being pushed across material
— Car
roaming on the streets.
— Turning
of bikes on curves.
— Skies
sliding on snow.
— Pulling
a trolley.
— Books
sliding.
— Walking
& many more…
Desired & Undesired friction forces
— Desired
friction forces are forces that help us in work.
Example: Friction help us in walking.
— Undesired
friction forces are forces that oppose our work, create resistance in our work.
It’s a loss of
energy.
Example, Friction between Gears
Fluid flow through pipes
Types of frictions
Dry Friction
Occurs between no lubricated surfaces of two solids
Fluid Friction
— Occurs
when adjacent layer in a fluid move at different velocities.
— Static
Friction
— When
applied force is less than or equal to the friction force & object doesn't
move is called static friction.
— F(r)≥F(a)
Where,
F(r) = friction force
F (a) = force applied
Kinetic Friction
— When
applied force is greater than friction force & object starts moving is
called kinetic friction.
- — F(r) <F(a)
Static
Friction
— Formula
F(r) = µs (N)
Where F(r) = Frictional Force
µs = Coefficient of static friction.
N = Normal force on the object.
Kinetic
Friction
— Formula
F(r) = µk (N)
Where, F(r) = Frictional force value.
µk = coefficient of kinetic friction
N = Normal force on object.
Coefficient
of friction (µ)
Object is in static Equllibrium.
F = F(r)
F(r) = µ mg cosα
F = mg sinα
Mgsinα = µ mgcosα
µ= mgsinα
/ mgcosα
µ= tanα
Tanα ≤ 1
µ ≤ 1
Friction
in Robotics,
- Robots on inclination slides back on track.
- For this problem friction should be increased in wheels, grips should be applied.
- Friction between gear is loss of energy implies to decrease in efficiency of robots.
- Friction must be reduced for reducing friction grease to be applied on gears.
- Friction between gears scrapes the gear teeth, and it destroys gear motors.
- For heavy work high torque motor to be used
These are basics of friction we will further learn about frictional analysis, point of application of friction force.
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