Robotics Introductory Laboratory Session (MECH 4002Y)1) What are the dimensions (centre to centre) of the different links of the mechanical structure of the robot? ELBOW

SHOULDER

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Robotics Introductory Laboratory Session (MECH 4002Y)WAIST

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

Belt drive is best suited when the centre distance is large (i.e in the shoulder and elbow part), and over small distances gears are more practical (that connect the gripper with the elbow). For precise performance and accurate timing over a large distance flat belt are required, which will tend to slip and will not prove satisfactorily. So, as solution to this, the belt is used and fitted to the toothed flywheel (found in the elbow and shoulder).achieve smoother movements. 2

Robotics Introductory Laboratory Session (MECH 4002Y)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. It 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 Axis 0

Range Angular movement 2700 Axis centre from top of base 185mm Axis 1 axle to column centre 50mm Angular movement 1650 Arm length between axle centers 225mm Angular movement 3000 Arm length between axle canters 225mm

Axis 1

Axis2

3

Robotics Introductory Laboratory Session (MECH 4002Y)Axis3 Axis 4 Angular movement 2900 Angular movement 2900

4) Plot accurately the minimum and maximum working envelope of the robot. The diagrams below show the working envelope

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Robotics Introductory Laboratory Session (MECH 4002Y)

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. By measuring rotation your robot can do things such as determine displacement, velocity, acceleration, or the angle of a rotating sensor.

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Robotics Introductory Laboratory Session (MECH 4002Y)

Light sensor

Encoder disk

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.

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Robotics Introductory Laboratory Session (MECH 4002Y)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). y y Compressed air is a fast working medium. Air can be easily transported in pipelines over long distances. 7

Robotics Introductory Laboratory Session (MECH 4002Y)Limitations y y When pneumatic equipments are on, they are noisy. No variation of speed and strength of 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) Calculate the applied load to raise the payload.

Payload = 1kg Applied load (Fx) = ? For Equilibrium (ref to above diag) Moment on left hand side = Moment on right hand side 9.81 x 0.44 Fx = = Fx x 0.26 16.60N

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Robotics Introductory Laboratory Session (MECH 4002Y)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 PNP output and is designed as a normally-open contact. A yellow LED indicates the status. The switch is protected against polarity reversal, overload and short 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. 9

Robotics Introductory Laboratory Session (MECH 4002Y)11) Briefly explain the functioning of the WALLI software. WALLI :- Work-cell Amalgamated Logical Linguistic Instructions WALLI is a software that enable the user to interact with the Gryphon Ec 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

Inserting and activating peripherals can be done through the program. When the data is selected by clicking on it, it may be incremented by the scroll bar. Alternatively 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. Each 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 y y y y Quick and direct interaction with the robot Must monitor the robot closely to avoid from hitting with obstacles in the surrounding Speed can be control It can be used to delicate and hazardous environments 10

Robotics Introductory Laboratory Session (MECH 4002Y)Limitations y y Positioning of the robot to a specific location is quite a difficult task No repeatability

Simulator Advantages y y Easy to manipulate No predefine movement (where the user position the simulator, the robot also follows the exact sequence) Limitations y y Cannot use the gripper No repeatability (irreversible)

Computer (WALLI software) Advantages y y Once the sequence is programmed in the software, the robot can perform alone Can add various devices (conveyor, sensors, and indexing table) and can make them to operate in order of preference. y y y High degree of accuracy and repeatability Work can be stopped and saved to continue later Speed can be varied

Limitations y y Careful inputs must be typed to avoid from hitting obstacles To use WALLI software alone to reach a specific spot is a difficult task 11

Robotics Introductory Laboratory Session (MECH 4002Y)13) Explain the safety aspects to be taken into consideration when working with a robotic system. y y y y y y Always switch of the system when not in use Assure that only personnel working with the robot must have access in the working zone Assure that proper configurations are made before switching the robot on Never remain below the gripper if it is holding load Regular maintenance must be made Immediately switch off the robot on hearing abnormal sound and case must be reported immediately.

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