This document discusses key parameters and specifications for industrial robots. It describes six key parameters: (i) number of axes, (ii) load carrying capacity, (iii) maximum speed, (iv) reach and stroke, (v) tool orientation, and (vi) precision and accuracy. It provides details on each parameter, including defining major and minor axes, how load capacity depends on weight of the end effector, how speed is measured, differences between reach and stroke, and how tool orientation is determined by the robot's axes.

1. DH- Parameters Robotics
BY: Mahmoud Hussein

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17. Robot specification
But in addition to classification, there are several additional characteristics :
(i)Number of axes
(ii)Load carrying capacity (kg)
(iii)Maximum speed (mm/sec)
(iv)Reach and stroke (mm)
(v)Tool orientation (deg)
(vi)Precision, accuracy and Repeatability of movement (mm)
(viii) Operating environment
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18. Number of Axes
The industrial robots have got a number of axes about which its various links
rotate or translate.
the first three axes of the robot called major axes are used to establish the
position of the wrist.
The remaining axes of the robot are used to establish the orientation of the
robots wrist, called minor axes .
Thus a six axes robot is a general manipulator which can move its end effector
to both an arbitrary location and an arbitrary orientation with in its work volume.
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19. Some industrial robots have more than six axes, termed as the redundant
axes , which are generally used to avoid certain obstacle in the robots work
volume.
The mechanism to activate the robot tool (end effector), or the opening and
closing of the robots gripper, is not considered as the independent robot
axis, as this mechanism (axis) do not contribute to acquire either the
position or the orientation of the end effector in robots working space.
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20. Load Carrying Capacity:
The load carrying capacity is mainly determined by various factors : robot’s
size, configuration, type of drive system and the type of application for which it
is designed.
A very wide range: from few grams to several thousand of kilograms.
The maximum load carrying capacity should be specified for the condition that it
is in its weakest position.
It is the position when the robots arm is at maximum horizontal extension.
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21. The specification provided by manipulator manufacturers is actually the
gross weight capacity that can be put at the robotic wrist.
Thus to use this specification the user must know weight of the end
effector.
E.g., if the gross load carrying capacity of a robot is 10.0 kg and it’s end
effector weigh 3.0 kg, then the net load carrying capacity of the robot would
be only 7.0 kg.
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22. The maximum tool tip speed of the robots is from a few mm per
second to several meters per second.
The speed of the robot is measured at robot’s wrist.
Thus the highest speeds can be achieved with maximum
horizontal extension of arm away from the base of the robot.
Also the type of the drive system affects the joint speeds,
e.g. the hydraulic robots are having faster joint motions than the
electrical drive robots.
Maximum Speed of Motion
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23. A meaningful measure of the robot speed is the cycle time,
which is the time required to perform several periodic
motions of robot.
As it is desirable for any production operation to minimize
the cycle time of task, most of robots have the provision to
regulate or adjust the speed.
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24. Reach and Stroke:
Reach and stroke of the robot are the measure of the work volume of
the robot.
The horizontal reach: it is the maximum radial distance at which the
robotic wrist can be positioned away from the vertical axis about
which the robot rotates, or the base of the robot.
The horizontal stroke: it is the total radial distance the wrist can move.
There is always a certain minimum distance the robot’s wrist will
remain away from the base axis.
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25. Thus, the horizontal stroke is always less than equal to the horizontal
reach.
For a cylindrical coordinate robot the horizontal reach is the outer
cylinder of the workspace, while the horizontal stroke is the difference
between the radii of the concentric outer cylinder and the inner
cylinder, as shown in figure 1.10
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r

26. The vertical reach:
is the maximum vertical distance above the working surface
that can be reached by the robot’s wrist.
The vertical stroke:
is the total vertical distance that the wrist can move.
the vertical stroke is also always less than equal to the
vertical reach.
articulated robot have full work envelope means stroke equal to
reach
But necessary to program to avoid collision with itself or work
surface.
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27. Tool Orientation
The three major axes of the robot determine the work
volume, while remaining additional axes of the robot
determine the orientation of the robot’s end effector.
If three independent minor axes are present then the end
effector will able to achieve any arbitrary orientation in the
three dimensional work volume of the robot.
the three axes associated with the wrist are called as yaw-
pitch and roll which are used to define the orientation of end
effector of robot.
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