All the robots are the inspiration of some natural things. In worms, Inchworm has some special features its walk quickly and its so cute. The dream about making inchworm robot is start when i am 15 years old in my school days, i never see the inchworm before. In a Camp when sitting on the ground at the first time i see inchworm. I like it very much. But now a days i see lakhs of inchworms in our factory, even though i like it very much. When i start making robots i think lot of ways to make a robot like inchworm. Now only i got a full structure and it also come out very beautiful.

I make a Arduino app to control the robot. It move in all directions and we also able to change the speed.

I cant able to make it to the real size of inchworm, that's the secret of God's creation.

Its very easy to build and it works very nice and kids like it very much, Only hard work is to compact the circuit with in the worm and correct the wiring, but when complete it looks so good. Its take me more than 20 days from design to my table (because daily done some changes to make it work properly as per my expectation because last robot work very slowly and need some help).

Lets start the Story of the Inchworm.

3D Design and Print

I use Tinker cad for design and print it in a Online 3d Prining service. Files are uploaded in the below links.

Correct the 3D Parts

Once the 3d parts are received we want to check and rotating joints and correct it, because i only order to print in 0.2mm so the rotating surface is not smooth. I already create the rotating joint and the holder with same dimension to make it smooth after printing. Use emery sheet and smooth file to smooth the rotating joint and joint holder. In the body side a small square piece is provided correctly in the middle of the screw holes, use smooth file polish the sides to fit with the arm square hole. Correct all the body and arms. Now take the plan and start fixing.

Join Magnet in the Leg

First step is to fix the electromagnet in the leg. In the leg already have a path for wire connection so it fitted correctly, only 0.2 mm on both sides given. Screw from the top, I don't use the screw cone with electromagnet, i use a flat head screw.

Prepare Servo Horn and Fix With Arm

When design the arm i make a mistake for horn size, I first design for two side horn and then remove one side. But when fitted found one side horn is bigger then two side horn in both length and width. So I take all the 5 two side horn and cut one side to make it one side horn(if you want to fit one side horn directly kindly change the design). Use File polish the cutting edge. In the last picture you able to see the size difference.

Use the screws come with the servo to fix the horn to the arm, Be careful while screwing because the screw end is sharp and the screw driver is small so it also sharp (I puncture my fingers). Also take care of the arm its only 3mm so if give extra force it broken. Connect all the Five arms and horns.

Prepare Body to Connect Arm

Like i already said correct the small square in the body and make it fit tight with the arm square hole. and check the connection in both directions.

Connect Body With Leg and Head and Tail

Now start join the worm

First step is to connect the body and the leg. Already holes are provided, use 10 X 2mm screws and nut to join.

Then connect the head and tail piece. This take some time because i never provide hole in the head and tail tallow screw driver to enter, so I use nose plier to tight the nut. First correct the head square hole with the body square piece and put a screw through head and use node plier tight the nut. Like wise connect the tail, actually both are same design consider one as head and another as tail.

 Connect All the Links and Check the Plan

Arrange and check the links are ok as per our plan.

Connect Servo With Home Degree

Now the time to fit the servo. As per plan arrange the servos with the parts, Name the servos as per program. Set the servo angle with the test the program and fitted with the body. Pass the wire through the back hole provided for the connector to come out. Names and servo position as follows from back

1) Tail - 35 degree

2) Tail2 - 125 degree

3) Center - 90 degree

4) Head2 - 90 degree

One by one set the servo degree and connect. First insert the arm in the holder and make it straight with the body and then put the servo on the body and insert the horn in to the servo connector. Screw the horn with the servo. Use 10 X 2mm screw and nut to connect the screw servo with the body. Connect all the 5 servos now the basic part is ready. Careful when tight all the parts with screw driver, dont broke any parts. Now move with hands to check the working.

Circuit Plan

The picture is self Self explanatory, Which pins are connected with which servos and for control magnet use ULN2803 IC. Make the circuit as small as possible because the circuit must fit inside that small head and tail.

Prepare and Connect Circuit

Solder the circuits using thin wires because lot of connection in this project is use normal wire the wire become a big bundle. Check the circuit with the worm arrangement. For that first want to complete the program.

Android Program

This is my 14th app in MIT App Inventor.

Letters transmit as per key press in the app

Front - F

Left Back - H

Left - L

Left Front - I

Back - U

Right Front - J

Right - R

Right Back - K

Speed Up - U

Speed Down - D

Download the App from the Link Given below. Install the app in your Android mobile. Enable the Bluetooth in the mobile and pair with HC05. Open the Inchworm Robot App in the mobile pick the HC05 bluetooth when connected the joy stick open use buttons move the robot also increase and decrease the speed.

Arduino Program

As per the command received from the android change the position of the servo. For speed control smoothmove function is inside the program increase and decrease the speed by change the smoothdelay in program as per the command receive from android app. Main thing want to check is while magnet hold that leg want to be straight in with the floor.

Download the code from the below link and upload it to the arduino mini pro. Now the worm is ready for test.

Test Run

Its a test run with only forward and backward with circuits outside. I test it with the very low speed delay 50 between each single point servo move. It also look so cute. I use my table its a steel but small in size.

Boxing the Circuits

Divide the circuit in two sides for head put the microcontroller and the bluetooth module. For tail Power supply board and the ULN2803 ic board.

I cant able to insert the connector and all the wire through the holes in the head and tail. So unscrew it from the body and pass the wires through the hole in the bottom and pass it through leg, divide the wires for two sides. Put the circuit inside the head and tail. Cant able to put the head program pin inside so it peeping from the head. Hot glue and tape with insulation tape before put in side the head to avoid short circuit.

Now we want to correct the wires and make it neat.

Correct the Wiring and Finishing

Use Cable ties to correct the wiring. Check the wire is enough for servo movement from 0 to 180 degree before tie with the cable.

Cover With Lids

Covers are already printed with three sides for screwing in body, but one side already arm screw nut peeping so cut that side and put the lids and screw it. For tail the half round cover fitted correctly, but for head due to circuit program pin and HC05 connector pin peeing out, we not able to put the cover, So i have some balls for kids cut the bottom side and screw it with the head, color the ball with black color. Now all work finish the worm is ready.

Worm in Action

See the action of the Worm in my grandma steel cot it is a double bed cot, control using mobile app. Play with balls also.

This project teach me lot of patience, especially while completion. Please read this also what are the hurdles while develop this project so you plan according to that while start develop project

1) I have only 1 MG90S servo in hand so for this project i order 5 nos, it take up to a week to receive servo, on receive check and found one servo not working. So think no problem use the spare one in my hand.

Then all are going well up to the finishing of the project.

At each step i check the test run

a) After Hot glue the circuit.

b) After extend the wires and connect the circuits.

c) After Put the circuit inside the head and tail.

d) After wire tie the Circuits.

2) Once complete up to this stage magnet head magnet not working. Remove the circuit and found control wire from mini to ULN2803 unsoldered from the minipro. So reverse the work and do it again. Then check and found all ok.

3) Once Close the covers and check found the tail servo not working, feeling so bad test that servo alone and its dead open servo and check the power is received but the servo not working, No MG90S is in hand.

4) Check SG90 servo and it fitted in that place correctly, thank god and try to fit MG90s horn not match with the SG90 servo. So remove that horn and change the MG90 horn, while tight the screw on the arm the arm broken. At that time i feels very very very bad at the same time at night 1.00 power gone and home ups problem. Use mobile light, fix the arm using feviquick and sit alone. At 1.30 power come but the arm not fix. Use soldering ion weld the broken joint and its fix again thank the god. Thats why check the final videos tail arm horn is white.

5) Rewiring done and close all the boxes its time 3.00am this time also power gone, so cant able to check, wait for few minutes and go to bed, in the morning when check and found ok feel free its working as like expected.

So what you want to do before start the project is

a) Have extra servos in hand.

b) Print extra arms before start assembling

c) Mainly don't work at night

But its a nice experience to develop this project. Feel very very happy when see the robot moving. Let join with me in happiness develop robots and feel happy like parents seeing baby's first walking.