How to Construct a Robot Part 2: Gripper Copyright © Texas Education Agency, All rights reserved. 1

Basic Robot  We are going to construct a robot part by part.  The size and speed will be determined by its part.  Later in the instruction, the size and speed will be determined by the controller.  We will learn how to use a Plan Sheet, gather information, select the right part, and construct that part. Copyright © Texas Education Agency, All rights reserved. 2

 With Plan Sheet, either as one sheet or two sheets, lay out or draw a gripper for your robot. Start gathering information to construct the robot gripper you want. You can also draw the part on regular drawing paper. Copyright © Texas Education Agency, All rights reserved. 3

1. Draw one or as many drawings as needed. 2. Refine or select the part that is best for the robot. 3. The material might have a reaction on the robot, so a redraw may be in order. 4. Keep in mind all the features that are needed (construction strength, speed, function, purpose, weight). 5. Choose the best one, not necessarily the best drawing. 6. Choose the best person and the right tool to make the part. Copyright © Texas Education Agency, All rights reserved. 4

The GRIPPER should be your main consideration to perform your task. We will try three challenges to come up with the best possible gripper for the task. The main consideration of the gripper should be: 1. Time 2. Effectiveness (easy, no wasted motion) 3. Strength (construction should not be shaky, but well balanced) 4. Requires one step to pick up, hold, and place Record your work and come up with a suitable conclusion. Copyright © Texas Education Agency, All rights reserved. 5

 Overview By looking at a human hand, we can tell that years of evolution have developed quite a sophisticated gripper, but a gripper simply means a device used to “grip” objects in order to pick them up. In this first challenge, you will need to construct some sort of gripper to best pick up marbles. Copyright © Texas Education Agency, All rights reserved. 6

 Having difficulty creating a gripper that works to pick up marbles? If you have created a gripper that works effectively, try using it to pick up differently shaped objects. Does it work?  Using your own gripper, see how many marbles you can pick up in one minute. Copyright © Texas Education Agency, All rights reserved. 7

 Now pick up the marbles and objects using your own hand.  Was it easy? It should have been.  Can we conclude that the human hand is one of the best types of grippers to pick up objects?  Let’s test this hypothesis.  First let’s construct your own robot hand. Copyright © Texas Education Agency, All rights reserved. 8

 Record how many marbles you can pick up in one minute with your first gripper and then how many you can pick up with your hand. Which one was more efficient? Copyright © Texas Education Agency, All rights reserved. 9

1.Place your hand on a piece of cardboard and trace it. 2.Mark the points of your joints on the cardboard. 3.Cut out traced hand and fold at the joint marks (three folds per finger except thumb). See Figure 1. 4.If necessary (depending on the type of cardboard used), reinforce the cardboard hand with duct tape or insulating tape. This will allow for more control over the hand’s motion. 5.Cut up a straw(s) into several one centimeter (or slightly less) long pieces. 6.Glue the cut up straw pieces between fold/joint marks on the top and bottom of each finger. Copyright © Texas Education Agency, All rights reserved. Figure 1 10

7.Glue the remaining straw pieces on only one side of the of the hand as seen below. 8.Attach rubber bands (red lines in Figure 2) to the side of the hand that only has straws on the fingers. Slide the rubber bands through the straws and either glue them down or staple them down so that they are stretched out ever so slightly. The hand should still be flat as seen in the picture. 9. Attach string (green lines) to the tips of each finger and slide the rest of the string through the remaining straws (Figure 2). Figure 2 Copyright © Texas Education Agency, All rights reserved. 11

10.Attach hand to some kind of base (i.e., ruler, PVC pipe, etc.). See Figures 3 and 3.1. Figure 3.1 Copyright © Texas Education Agency, All rights reserved. Figure 3 12

 Now, using your newly constructed hand, pull on the strings in order to contract the fingers to make a fist.  Try picking up the marbles and objects and placing them into a bowl. See Figures 4 and 5. Figure 4 Figure 5 Copyright © Texas Education Agency, All rights reserved. 13

Using your gripper hand, try stacking up some type of blocks as seen in Figure 6.  Does it work effectively?  If not, construct a type of gripper that will. Figure 6 Copyright © Texas Education Agency, All rights reserved. 14

Do you think the hand gripper is the best type of gripper for all objects? Copyright © Texas Education Agency, All rights reserved. 15

Now that you have come up with a conclusion, sketch your gripper and make a Plan Sheet. Make a three-view drawing of the gripper, and start gathering information to construct your gripper, part by part. 1. Draw one or as many drawings as needed. 2. Refine or select the part that is best for gripper and robot. 3. The material might have a reaction on the gripper, so a redraw may be in order. Copyright © Texas Education Agency, All rights reserved. 16

4. Keep in mind all the features that are needed (construction strength, speed, function, purpose, weight). 5. Choose the best one, not necessarily the best drawing. 6. Choose the best person and the right tool to make the part. Copyright © Texas Education Agency, All rights reserved. 17

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Copyright © Texas Education Agency, All rights reserved. Is it doing what you want it to do? 20

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EXAMPLE - to stay inside of perimeter, balance, and ease of applications. Move gripper, wheels, body, column, arm, to find balance and ease of performance. Copyright © Texas Education Agency, All rights reserved. 23

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