2. Design Example

8/14/2019 2. Design Example

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Dr. Tarek A. TutunjiEngineering Skills, Philadelphia University

Forward Design Example

Dr. Tarek A. Tutunji

Philadelphia University, Jordan


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1. Define the Problem The objective is to build a system that can translate a

weight in three dimensions by manual joystick.

Specifications:

Load = 5 kg

Speed = 0.11 m/s

Constraints Time 8 months

Budget: $800


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2. Gather Information Types of cranes

Tower

Truck Mounted Overhead

Travelling bridge

Gantry

Jib Monorail


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2. Gather information An overhead crane is a crane where the hook-and-line

mechanism runs along a horizontal beam that itself runsalong two widely separated rails.

Also a hoist is used to lift the items, the bridge, which spansthe area covered by the crane, and a trolley to move alongthe bridge.

Its purpose is to move objects automatically between twolocations in a factory


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2. Gather Information Main Components

Bridge

Rail Trolley

Beam

Hook


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2. Gather Information Electrical components

Motors

Electronics Controller

Sensor

Mechanical components Shafts

Gears


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3. Propose Solutions Type of crane

Tower

Overhead

Type of actuators

Electric: DC, AC, or

Stepper Pneumatic

Type of sensors

Optical

Limit Switches

Type of controller

PC

MicrocontrollerAnalog


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4. Study the Solutions Overhead crane works

better than Tower for ourpurpose

Microcontroller

Cheaper than PC

More accurate thananalog

DC Motor

Cheaper than AC andeasier to control

Easier than pneumatic

Sensors

Limit switch for linear

end position Optical encoder for

motor position


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4. Study the Solutions: Choose Single girder overhead crane with dimensions: 2 m

length, 1.2 m width, and 1 m height

Three DC motors for xyz-directions

PIC microcontroller

Limit switches, three positioning sensors, control and

drive circuits Keypad. The user can specify the desired position by

entering the coordinates on the keypad


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5. Analyze & Design: Block Diagram

ControllerPower Electronics

Interface

Limit Switch

Sensors

Crane Plant Electrical Motors


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Analysis: Weight Calculations Motors weight = 1.5kg 2 = 3kg

Shaft and bearing =4kg U- Shape steel bar and steel sheet = 2kg

Screws and roundels = 0.25kg

Teflon wheels = 0.25 kg Other parts = 0.5 kg

Total weight of Trolley = 10 kg


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Analysis: Power Calculations F = M g F = 5 kg 9.81 m/s = 49.05 N

T = F R T = 49.05 N 0.025 m = 1.23 N.m

Pm = T Pm = 1.23 N.m 4.7 rad/s = 5.8 watt. P actual = 5.8 watt 1.6 = 9.6 watt

Pe = 9.6Watt /0.8 = 12 Watt

Pe = I V We chose DC motor with V = 12 V, I = 3 A.


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Analysis and Design: Simulation


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Design: Mechanical Drawings


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Design: Flow Chart


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Design: Schematic Diagram


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Final Design The mechanical components were composed of the frame,

the girder, and the trolley.

The frame used bars of hot roll steel AISI 1020: two parallel

tracks of 2m length, six vertical columns of 1m length, andsixteen side holding bars.

The girder consisted of two parallel girder tracks of 1.2 mlength mounted to side rolling bases.

The trolley part had two 36 watt DC motors with internal worm gearassembly mounted to side rolling bases.


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Final Design Actuators:

Three DC motors as: Hook motor to lift the load, trolley motor to move thetrolley above the girder, and girder motor to move the girder above thebridges. Each dc motor (3 A, 12V) had internal gears in order to reduce the

speed and increase the torque with a gear ratio 1/140.

Sensors:

Two linear optical encoders were used as displacement sensors for the x-ypositioning with a resolution 1pulse/cm. The tracks were made from plastic

and fixed to the frame. For the z-direction, rotational optical encoders wereplaced on the shaft of the pulley with a resolution of 20pulse/revolution.


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6. Implement: PCB


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Implementation: Mechanical


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7. Evaluate The crane was tested in

the labs

Equipment used: Scopesand multi-meters

Different loads (up to 5Kg) were used

Speed of movement wasmeasured usingstopwatch

Microcontroller wasdamaged during testing.

Limit switches werecalibrated.

The load cable was re-packaged

Added support to theskeleton frame

Insulated the controllerusing the opto-coupler.


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Final Prototype


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Acknowledgement This work was the effort of two student design teams:

Team 1:

Abd Al-hafez Suleiman

Yosef Abo Hurira

Team 2: Hassan Abu Zahra

Moafeq Alkhateeb

Fadi Darweesh


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ConclusionA design example was provided to show the 7-

design steps

In this design project, students used the 7-stepdesign process to build an overhead crane model

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2. Design Example