This version of a four degree of freedom pick and place robot will allow you to pick objects using gripper and re-orient picked objects.
Step 1: Assembly of the Robot
- Mount servo horn on top inner bearing disc using self-threading M2 (“M2” represents a diameter of 2mm) screws of 8mm length. These screws can be found in servo accessories. Be careful about holes you are mounting the horn on (use holes closer to disk centre).
- Place 30 mm stand-offs on the base. Fasten using M3 bolts of 8mm length.
- Take the bottom outer bearing disc and slide it over standoffs.
- Mount bottom inner bearing disc on stand-offs. Align the disc such that smaller holes are in line with the stand-offs.
- Put the bearing on top of bottom inner bearing disc. Observe how disc supports the bearing from beneath.
- Next, place the two middle inner bearing discs. These will perfectly fit inside the bearing.
- Seat the “servo horn & top inner bearing disc” assembly on top of bearing as shown. Make sure all smaller holes in these discs are aligned since we will fasten them all together using 20mm M3 bolts.
Note1: Do understand that it was necessary to slide down the bottom outer bearing disc earlier. You won’t be able to do it now due to diameter differences.
Note2: Observe how the bearing has been clamped between the top and bottom inner bearing discs.
- Place the middle outer bearing discs first and then top outer bearing disc as shown. The middle discs will have a larger inner diameter compared to the top and bottom ones. The inner diameters of the middle discs will be equal to the bearing’s outermost diameter.
- Slide up the bottom outer bearing disc, align the holes in the discs and stack them.
Again, see how the bearing is sandwiched because the top and bottom bearing discs have a smaller inner diameter compared to the bearing’s outermost diameter.
- Place 20 mm stand-offs on the top and fasten the M3 bolts of 20mm length from the bottom. Your base is completed now.
The base assembly should look like this upon completion.
- Place servo motor into the slot available on racquet-shaped link 1. Be careful about the positioning and the orientation of the servo. Have a careful look at the illustrations.
- Fasten the servo to the link using M4 bolts of 16mm length and nuts.
- In the figures, you see head of servo pointing upwards. Don’t let this confuse you; the head actually goes into the slot in the horn. We will come to this again, for now attach M3 bolts of 8mm length and 20mm standoffs to the link as shown in the illustrations below.
This is the orientation in which we will place the completed link upon our base. Note the free holes through which we will drive the screws to fix it to the base.
- Place this assembly on the base as shown & fasten using M3 bolts of 8mm length.
Keep in mind that you’ve set servo at 90 degrees before assembling (connect servo to evive, go to control > servo and set servo at 90 degrees).
- Observe how head of the servo goes into the servo horn. We have to ensure proper locking between servo head and servo horn. To do this, drive a bolt into centre of the horn (find this in servo accessories) through the bottom of the base (through the large hole) and fasten it.
It is important to ensure that your servo motor does not move vertically and exhibits only rotary motion while in operation.
Step 2: Circuitry of the RObot
Note: Ensure that all the servos are properly connected and there are no loose wires, this might otherwise effect performance of the arm during operaton. Use cable tes for wire management.
Step 3: Arduino Code
In this program we are controlling the robotic arm using potentiomters and slide switch.
- Base Servo is controlled using potentiometer 1
- Link 1 Servo is controlled using potentiometer 2
- Link 2 Servo is controlled using slide switch 1
- Gripper Servo is controlled using slide switch 2
This program also shows the variable voltage on the screen.
Caution: The robotic arm should operate at 6V using a 2A power supply.
Connect four motors according to the following:
- Base Servo – Channel 1;
- Link 1 Servo – Channel 2;
- Gripper Servo – Digital Pin 10;
- Link 2 Servo – Digital Pin 9.