Gryphon EC Final Report

1)

1) What are the dimensions (centre to centre) of the different links of the mechanicalWhat are the dimensions (centre to centre) of the different links of the mechanical structure of the robot?

structure of the robot?

ELBOW ELBOW

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WAI_ST

2) What is the drive mechanism used for each link? Explain the relevancy of the type(s) of mechanism on the Gryphon robot.

The driving mechanism used are the belt and gear 

B_{elt drive is best suited when the centre distance is large (i.e in the shoulder and elbow part), and}

The stepper motor can divide a full rotation into a large number of steps, thus position can be controlled precisely without and small displacement can be achieved which the stepper motor.

The gearing system use is a bevel gear, which found at the connection of the elbow and the end effector. I_{t is used for smooth transmission at high rotational speed.}

3) What are the types of degree of freedom as used on the Robot, and what is the range of each degree of freedom?

The degrees of freedom are linear and rotary. These comprises the 5 axis as describe in the diagram below

Degree of freedom Range

A_{xis 0} A_{ngular movement 270}0

A_{xis centre from top of base 185 mm} A_{xis 1 axle to column centre 50mm}

A_{xis 1} A_{ngular movement 165}0

A_{rm length between axle centers 225mm}

A_xis2 A_{ngular movement 300}0

A_xis3 A_{ngular movement 290}0

A_{xis 4} A_{ngular movement 290}0

4_{) Plot accurately the minimum and maximum working envelope of the robot.}

5) What are the internal sensors used to monitor the displacement and/or velocity of  the robot? Explain the importance of these sensors.

The internal sensors used are encoders.

The encoder is a sensor attached to a rotating object (such as a wheel or motor) to measure rotation. B_{y measuring rotation your robot can do things such as determine displacement,}

A_{typical encoder uses optical sensor(s), a moving mechanical component, and a special reflector} 

to provide a series of electrical pulses to your microcontroller. These pulses can be used as part of a PID _{feedback control system to determine translation distance, rotational velocity, and/or} 

angle of a moving robot or robot part.

E_{ncoder disk}  L_{ight sensor} 

6_{) Draw a schematic diagram to show the mechanical structure of the end effector.}

7) What drive mechanism is used to actuate the end effector? Explain its advantages and limitations.

The drive mechanism to actuate the end effector is pneumatic.

Advantages

y Pneumatics components are relatively inexpensive and the medium (air) is free (unlimited quantity).

L_imitations

y When pneumatic equipments are o n, they are noisy. y  No variation of speed and strength o f the gripper.

8) What is the maximum payload that can be safely held by the end effector?

The maximum payload for the end effecter is 1 Kg.

9) C_{alculate the applied load to raise the payload.}

Payload = 1kg

A _{pplied load (Fx) = ?}

For E_{quilibrium (ref to above diag)}

Moment on left hand side = Moment on right hand side

9.81 x 0.44 = Fx x 0.26

10) Describe the external sensors available for interfacing the robot and the other peripheral devices such as the indexing table, and the conveyor.

The external sensors are optical proximity sensor and limit switch.

Optical Proximity Sensor 

Proximity switch that responds to light signals and delivers an electrical signal. The switching distance can be adjusted by means of a potentiometer. The proximity switch has a P NP output and is designed as a normally-open contact. A _yellow LED _{indicates the status. The switch is}

 protected against polarity reversal, overload and sho rt circuit.´

 Limit switch

The limit switch has two mode of operation, the normally close and the normally open mode. For  the normally open mode, a 5V signal is sent when the switch closes while a 5V signal is sent when the switch opens. The limit switch has a spring mounted contact with which a small strip of  metal makes contact.

These sensors are used to detect the presence of objects, send the signal to the control which will in turn process it and execute the proper requirements such as stopping the conveyor or start.

11) Briefly explain the functioning of the WALLI _software. WALLI _:- W_ork-cellA_malgamatedL_ogical L_inguisticI_nstructions

WALLI _{is a software that enable the user to interact with the Gryphon} E_{c robot and number of} 

 peripheral devices such as conveyor, indexing tables, and sensors via a PC.

The screen below shows an example of data which is being sent to the robot

I_{nserting and activating peripherals can be done through the program.} W_{hen the data is selected}

 by clicking on it, it may be incremented by the scroll bar. A_{lternatively new data may be simply}

typed in as part of the work-cell when a simulator, teach pendant or control panel is being used the data on the screen is updated to the new position. E_{ach device can be control precisely and}

 perform to specific position desired.

12) What are the different modes of programming the robot? Outline the advantages and limitations of each mode of programming.

Teach pendant  Advantages

L_imitations

y Positioning of the robot to a specific location is quite a difficult task  y  No repeatability

 Simul _ator 

Advantages

y Easy to manipulate

y  No predefine movement (where the user position the simulator, the robot also follows the exact sequence)

L_imitations

y Cannot use the gripper 

y  No repeatability (irreversible)

C _om _pu_{ter (WALLI software)}

Advantages

y Once the sequence is programmed in the software, the robot can p erform alone

y Can add various devices (conveyor, sensors, and indexing table) and can make them to operate in order of preference.

y High degree of accuracy and repeatability

y Work can be stopped and saved to continue later  y Speed can be varied

L_imitations

13) Explain the safety aspects to be taken into consideration when working with a robotic system.

y Always switch of the system when not in use

y Assure that only personnel working with the ro bot must have access in the working zone y Assure that proper configurations are made before switching the robot on

y  Never remain below the gripper if it is holding load y R egular maintenance must be made

y Immediately switch off the robot on hearing abnormal sound and case must be reported immediately.