Understanding Work Envelopes of Robots!

robots are designed based on the work envelope required the volume the end effector of this robot is able to reach is known as the work envelope for example for this robot shown the blue shade volume is the work envelope let's learn more about this crucial concept of robotics the work envelope is different for different robots a robot's work envelope depends on three physical characteristics the first one is the range of the robot's joints both the linear and angular range of a robot is illustrated here the second characteristic is the size of its body arm and wrist the last characteristic is the type of joints different work envelopes are created by modifying these three characteristics let's understand these concepts with the help of a robot design challenge suppose we have to collect some boxes from a conveyor belt and place them in this highlighted location the work envelope required for the robot is obviously rectangular in shape can you guess what type of robot configuration is the best fit to complete this task yes you'd need a robot with linear motions in all three directions inside this volume this robot has three linear joints to accomplish movement in the x y and z directions this robot's end effector can pick up the object anywhere inside this rectangular work envelope move in all three axes and place it as needed these kinds of robots are called cartesian robots now let's consider the same robot but this time it's using a different end effector a metal cutter here due to the nature of the work the operator has to be inside the work envelope we defined earlier which can be highly dangerous for safety purposes you won't want this new end effector to go near the operator's hand in short you have to block the robot's movement in the y direction after this red plane to achieve this end engineers often restrict the movement of the robot by using electro electromechanical limit switches which creates a border beyond which the bot cannot go in any given conditions in short even though the work envelope is huge this robot will be able to work only within this red volume this new red volume is called an operating envelope let's move to our next robot and study a different work envelope let's assume that the robot has to move these boxes from one conveyor belt to another the work envelope needed for this task is obviously cylindrical in nature can you suggest some design modifications to the previous robot to achieve the new work envelope to attain the cylindrical volume we need two linear movements and one rotary movement simply replace one linear joint from the cartesian robot with a rotary joint now the robot can rotate 360 degrees on its central axis these kinds of cylindrical robots are mainly used to work as mediators between two or three massive machines to transfer an object from one station to another if you observe carefully you can see that the work envelope here is not a solid cylinder it has a dead zone at the center can you tell why this dead zone is due to the robot body's physical limitation in this case you can see that the robot's arm can retract only up to its body and not beyond that thus a dead zone volume will always be inside the cylindrical robot's work envelope however such dead zones are not present inside the cartesian robot's work envelope with a simple design modification we can convert this cylindrical robot into a more versatile robot which does tasks like welding this car chassis together for this task the robot has to turn at different complicated angles the cylindrical robot cannot perform this task all you have to do to achieve it is replace one more linear joint with a rotary joint here this rotary joint can go from approximately positive 30 degrees to the bottom of the ground now using your visualization skill can you predict this robot's work envelope just revolve this shape 360 degrees in the z-axis what you get is a partially spherical work envelope these kinds of spherical robots can easily complete this welding task with an angle what you see in the central area is the dead zone of a partial spherical configuration this space can be an efficiency weakness if we replace the last linear joint from our bot with another rotary joint this will make it a revolute coordinate robot which should reduce the dead zone and give the bot more reach this robot looks similar to a human arm right now the new challenge let's deduce its work envelope first let's freeze the z-axis rotation and figure out the 2d work envelope which arises due to the robot's remaining two rotary arms when both the arms are fully stretched the end effector can draw a circle of 280 degrees you can observe from the top view why this joint cannot go beyond this 280 degree angular limit anyway this is the biggest circle this robot can draw now we need to figure out the smallest circle this robot can trace this robot traces the smallest circle possible when the arms are folded like this however after a certain movement the circle can't be traced further because the lower arm will touch the robot's body the trick to extend the circle tracing is simple just fold the arms the opposite way now you can trace the circle further this is the combined 2d shape these two arm rotations can trace now figuring out the final work envelope is easy the last rotary joint at the base can move the whole robot 360 degrees so just revolve the 2d shape 360 degrees there you go this robot has a spherical work envelope this fully spherical robot has a dead zone as well which is much smaller than the previous configuration in many industries advanced versions of these robots with more complex rotary joints are used for assembly lines welding spray painting etc knowing the work envelope helps you in many ways we hope you now understand robots work envelopes see you in the next advanced video on robotics don't forget to be a member of the lessex team thank you

Channel: Lesics

Views: 582,990

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Id: _canCYWZPsc

Length: 7min 47sec (467 seconds)

Published: Sat Oct 30 2021