Chassis
Designing
Chassis designing is the very first thing we should get in
mind while we make the robot, chassis is the main part of any vehicle robot or
anything, so how to make chassis? While selecting a chassis the very first
thing that should be in our mind is for what purpose we are designing chassis?
Fir heavy purpose chassis should be strong mechanical
properties should be great, like if I want to make pick and place robots then I
have to place an arm on that and pick and place robot are used in industry so
it is used to pick very heavy objects and put them into another place so chassis
should be hard & tough, and for light purpose of robot, like making a
detector robot, like line following robot they do not acquire so much weight so
their chassis can be made with light material like aluminum sheet plywood of
3mm thickness.
As we can see in vehicles their chassis are skeleton type
it's better chassis because it's hard and material, wastage of material is
minimum, if we create both body and the Chassis together, load increases on the
motors and shaft of the motor starts bending, bending of the shaft is harmful for
the gear motors, teeth of the gear start cutting, and this leads to the motor not
working.
If we want to do something good we have to remember
everything, where we are doing wrong.
This is all about chassis designing of a robot before we
read, our purpose of designing a robot
should be clear.
Building a chassis
for non-steering type robot or skid tank steering –
- Advantages for skid steering:
-Easy to control
-Easy to make
- Skid steering further divided into two types
1. 4 wheels,
2. Two wheels + 1 caster wheels.
- For chassis design, your center of gravity must be between your wheels, whether a robot is at an inclination or not.
Material Used for making chassis depends on the robot you
are making like for making pick and place robot arm is to be fitted in robot to
pick an object arm is further divided into two parts first one is holding an
object the second one is for up and down movement for placing an object, so the material used for making the object should be strong or (in terms of mechanical
engineering) we can say when pure bending is applied then material or chassis
it shouldn’t break.
Chassis can be of two types 1st one is simple
plate chassis & 2nd one is skeleton chassis.
- Properties of chassis-
-Stable
-Strong
-Lightweight
-Affordable
-Compact
-Maneuverable
A/c to Properties material used for making chassis should
be:-
- For Plate type structure:-
Plywood (3-5mm), Aluminum plate (3mm), Mica Sheets (3mm), Metal
sheet (5mm), Fiber sheets (3mm)
- For Skeleton type structure:-
Aluminum tubes (2-5mm) thickness, PVC pipes, Iron Pipes,
Steel Pipes.
For building steering type there should be a balance rod
that will provide you a steering in front 2 wheels steering type cannot be
created in 2 wheels robot because caster wheel doesn’t allow you steering
because it’s movement is in 360’.
The maximum four-wheel structure is used because of its
compatibility 2 wheel structure is only used in programmed robots, like Line
following robot.
Wheels selection:
Wheels are correlated with the speed of a robot plus a combination of your motor, speed of a robot also depends on the rpm of motor i.e. which rpm motor you choose and which wheel you choose.
Speed of Robot = 2πr × rpm (motor) ÷ 60
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The speed of the robot is given by this equation.
1. If we use wheels with the greater diameter and greater rpm it will increase the speed of a robot.
2. If we use big wheels and less rpm motor it will decrease the speed of the robot.
3. If we use small wheels and greater rpm motor speed will be greater than 2nd point.
The formulae given above will describe the three points.
- Grip vs. Slick
We should you grips in our wheels grips increases friction and allow robot to run on inclinations.
For four wheels robot we can use grips in back 2 wheels & slicks in front two wheels.
- Width of wheels
Width of the robot should be increased with respect to the weight of a robot.
For light weighted robot (500gm-1kg) width of wheels can lay b/w 5mm to 10mm.
For light weighted robot (500gm-1kg) width of wheels can lay b/w 5mm to 10mm.
For Heavy robot (2kg-5kg) width of wheel should not be less than 30mm.
For more than 15 kg robot width of wheels should be 40mm and more,
And diameter should be more than 90mm.
Omni wheel
Chain wheel
Chain wheel
Suggestions:
- It doesn’t matter how many wheels you have, as long as they all are driven.
- If you plan to turn, you should only have two “grippy” tires
- Pneumatic Tires, Soft Rubber Tires.
- Remaining wheels should be slick
- Hard rubber & plastic.
Wheels selection and wheel gripping are very much important in making robot it also depends on which type of robot we are making that will be discussed further.
BO Motors- Motors which are widely used for making robots these are also geared motors, small in size, in engineering field these are used for making obstacle avoiding robot, line following robot and many more.
Motor selection is very much important in making of robots, discussing about motors, there are many type of motors used in making robots.
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Tiny pager motors – A small tiny motors of 4mm, 6mm which are used for making robots which is not much expensive and available on internet.
DC geared Motors- geared motor are used where we want to operate the speed of a robot obviously we don’t want to make our robot uncontrollable, for making a controlled robot we have to control the speed of robot and we use geared motor.
Simple geared motor are of , 10 rpm, 30rpm, 60rpm,100, 150,200, 300, 500. For making different types of robot we use different types of motors as per their selection, these are not so much expensive lies in the range of 150-200 Indian Rupee.
Johnson geared motor: these motors are best for higher torque plus higher speed these are expensive motors not used by everyone, it is used for powerful work, Torque in these motors are high (5 kg-cm to 7 kg-cm).
Servo Motors- There are some special types of application of electric motor where rotation of the motor is required for just a certain angle, not continuously for long period of time. Servo motors have many more applications than robotics they are used in RC plane also. They are not so much expensive motors.
Stepper Motors- A stepper motor or step motor or stepping motor is a brushless dc motor that divides a full rotation into a number of equal steps. They are expensive motors.
Planetary geared motors: planetary gearing is a gear system consisting of one or more outer gears, or planet gears, revolving about a central, or sun gear. These motors are highly powerful motors with greater torque (36 kg- cm) these motors are also used in winch machine.
Simple DC Motor- Simple toy motors which are used in making toys and in some parts of robot its is also used for making BO motors.
These motors are available in single & double shaft both as per their requirements we use these motors.
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