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
1
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
Range
Axis
Angular
Axis
0
1
Axis
centre from top of base 185 mm
Axis
1 axle to column centre 50mm
Angular Arm
Axis2
Arm
0
movement 165
length between axle centers 225mm
Angular
3
0
movement 270
movement 3000
length between axle canters 225mm
Robotics Introductory Laboratory Session (MECH 4002Y) Axis3
Angular
movement 2900
Axis
Angular
movement 290
4
4)
0
Plot accurately the minimum and maximum working envelope of the robot.
The diagrams below show the working envelope
4
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.
5
Robotics Introductory Laboratory Session (MECH 4002Y)
Light
sensor
Encoder
A
disk
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.
6
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
Compressed air is a fast working medium.
y
Air
can be easily transported in pipelines over long distances. 7
Robotics Introductory Laboratory Session (MECH 4002Y) Limitations
y
y
When
pneumatic equipments are o n, they are noisy.
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)
Calculate
the applied load to raise the payload.
Payload = 1kg A pplied
load (Fx) = ?
For Equilibrium (ref to above diag) Moment on left hand side = Moment on right hand side 9.81 x 0.44 Fx
8
=
Fx x 0.26
=
16.60 N
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 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 co nveyor or start. 9
Robotics Introductory Laboratory Session (MECH 4002Y) 11) Briefly explain the functioning of the WA LLI 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.
by clicking on it, it may be incremented by the scroll bar.
When
Alternatively
the data is selected
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
Quick and direct interaction with the robot
y
Must monitor the robot closely to avoid from hitting with obstacles in the surrounding
y
Speed can be control
y
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
Simul ator
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)
C om puter
(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
y
Speed can be varied
can be stopped and saved to continue later
Limitations
y
Careful inputs must be typed to avoid from hitting obstacles
y
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
Always
y
Assure
that only personnel working with the ro bot must have access in the working zone
y
Assure
that proper configurations are made be fore switching the robot on
y
switch of the system when not in use
Never remain below the gripper if it is holding load
y
R egular
maintenance must be made
y
I mmediately
immediately.
12
switch off the robot on hearing abnormal sound and case must be reported
