Carbon Fibre shell for BFRMR1 mobile robot

As mentioned in my last post, I have been hoping to have a custom carbon fibre shell made for my robot for a while now, to replace the aluminium shell. That time has come! I have a friend who has been making carbon fibre parts for a while now and he kindly offered to make a part for my robot. The first step was to create a model of the part I wanted, which I did myself. I used styrofoam (blue) to create a model of the shell of the exact size required. I used hot glue to stick several bits of styrofoam together to give me a rough shape.

Rough shape styrofoam model of robot shell

Rough shape styrofoam model of robot shell

This was then shaped by hand using sandpaper to leave the final shape required. The shaping involved rounding the corners and ensuring the top of the shell was as smooth as possible.

The finished styrofoam model of the robot shell

The finished styrofoam model of the robot shell

At this point the styrofoam model was given to my friend who spent quite a bit of time getting it ready to use to make a mould. This process included sealing the part with epoxy resin, covering it with body filler and sanding it to shape and several coats of a special resin designed for pattern making that can be sanded and finished to a high standard. A mould of the part was then made that could be used to make the carbon fibre part. The carbon fibre part was made and given to me ready for fitting to the robot.

I completely dismantled the robot to allow the new shell to be fitted. I had to round the corners of the base plate to match the rounded corners of the shell. I fabricated some angled brackets to attach the shell to the robot, which were fixed to the shell with epoxy resin. I had to cut the carbon fibre shell to accommodate the head servo, the TFT screen and an access panel at the front and rear. I fabricated some additional brackets to hold the access panels on to the shell, and also attached these with epoxy resin. To protect the lovely shiny surface of the carbon fibre shell, I cocooned it in masking tape before any cutting or drilling took place. With the shell finished I rebuilt the robot, mounted all the parts to the shell and fitted the shell to the robot base. Take a look at the finished product!

BFRMR1 with custom carbon fibre shell

BFRMR1 with custom carbon fibre shell

Close up of the carbon fibre shell

Close up of the carbon fibre shell

Side View of BFRMR1 with  carbon fibre shell

Side View of BFRMR1 with carbon fibre shell

Switch array mounted to new shell

Switch array mounted to new shell

I am very pleased with the look of the robot with the carbon fibre shell and it is very tough. The other advantage is that the shell is now very light. I weighed all of the aluminium parts of the old shell that I took off and they weighed 750g. The carbon fibre shell weighs in at 260g. This is a considerable weight saving, especially for a robot driven by modified servo motors and should reduce load on the servos and extend battery life.

I have also been working on the software for the robot. I have modified the way the Arduino and the Raspberry pi interact and I have tried to move some of the real time processing to the Arduino. As such, the Raspberry pi now sends commands to the Arduino, via serial, to instruct the robot to carry out a particular movement. This could be move the head to a given position or drive forward/turn a certain distance. When the move is complete the Arduino then returns a packet of data containing up to date sensor readings. On top of this the Arduino is also monitoring the sensors as the robot moves, detecting potential collisions and stopping the robot if necessary. The Raspberry pi can inspect the returned data packet to check if the robot moved the required distance and if not, check which sensor triggered and act accordingly. This allows much more accurate control of distances moved and sensor thresholds to stop the robot and frees up the pi to do other tasks if required.

I have also been playing with the TFT display, nothing particularly special at the moment but I can switch between modes and start and stop the robot using the buttons, and display the status on the screen. Some pictures below.

Mode select displayed on the TFT screen

Mode select displayed on the TFT screen

IMG_1534

Status displayed on the TFT screen

I am currently improving the obstacle avoidance code and working on some basic behaviours for the robot. One of which, as shown above, is finding food mode. My idea is that the robot will search out objects of a certain colour which it will identify as food. It will then navigate to the object to satisfy its hunger. Other modes such as play may involve the robot looking for a ball or similar object. When I am happy with the obstacle avoidance mode of the robot I will make a video, stay tuned!

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