Up for the next challenge...

Let's just replace the wall by... 2 walls!
and the challenge becomes:

"Getting a rover rolling along a straight line. When the rover hits a corner, it moves away from this corner."

Stay tuned, we're working on it!

Test and report on prototype V4

Here's what Trevor looks like:

Let's recap what the challenge is:
"Getting a rover rolling along a straight line. When the rover hits a wall, it moves away from the wall."

and we did it !

Here's the event as we recorded it:

Conclusions

• Trials and errors is crucial to finally get a prototype working. It allows to solve problems step by step.
• There's not a single way to solve the issues faced.
• Simple is better! It makes prototypes more reliable.
• Never give up!

Trevor V4's anti-block system: how it works?

The new anti-block system is made of 2 wheels positioned on each side of Trevor at the front.

The wheel #1 touches the wall first and forces a movement to the left. Then wheel #2 touches the wall. With the inertia and the speed of Trevor, the direction changes and Trevor moves away from the wall.

Here's how it should work... 

Let's try it now!

Prototype V4: A simplified version

With the learnings from previous versions of Trevor, we finally built a simplified, lighter version. Here is Trevor V4:

Trevor V4 has 3 wheels. The 2 rear wheels are directly connected to the motor and the front wheel is mobile (rotation).
The solar panel is mounted on top of Trevor in a dedicated frame.
The anti-block system can be seen at the front of Trevor and is made of 2 main wheels. We will describe it in a next post.

And as you can see, we are very proud of Trevor and we have installed Trevor's logo on the side of the main frame :-)

Test and report on prototype V3

The anti-block is now functioning very well. When activated, the right wheel is not driven anymore and the left wheel is then driven backward.
BUT... when we connect the motor, the torque generated is not strong enough to drive the gears and the wheels. So Trevor is not moving AT ALL! :-(

Conclusions:

• We have overestimated the power of the motor
• We have underestimated the weight of Trevor
• Trevor is too complex, we need to SIMPLIFY it !

Back to the drawing board... let's simplify Trevor and its anti-block system. On the way to Trevor V4...

Yet another prototype: Trevor V3

Here's Trevor V3!

We changed the anti-block system and added the solar panel on top. We also made the 2 rear wheels independent so that when the anti-block system is not activated, the motor drives the right wheel forward and when the anti-block system is activated, the motor then drives the left wheel backward.

Here's how the new anti-block system functions:

and the two wheels running independently:

Test and report on prototype V2

We made a series of tests without using the motor to validate the operation of the anti-block system. The various movements (translations and rotations) are transmitted. Nevertheless the system is quite complex and not really reliable.

We need to change the anti-block system.

A new prototype: Trevor V2

We built a new prototype made of Lego. We decided to equip Trevor with a new anti-block system that is reversing the rotation direction of one of the 2 rear wheels. The objective is to avoid to get Trevor blocked when hitting an obstacle.

We used gears and toothed racks to transform the translation of the front part when hitting the wall into a rotation that is transferred to the rear part where the rotation is transformed back to a translation perpendicular to the initial one. This final translation moves the back part of Trevor, aligning gears that reverse the rotation of the wheel.

Test and report on prototype V1

We equipped Trevor with a electric engine and a solar panel to get the energy. The electric engine is equipped with a gear that is driving the gear attached to the rear wheels axis. 

Results :

• Trevor is moving forward !
• The frame isn't rigid enough
• The front wheel doesn't rotate and is blocked
• The anti-block system isn't reliable

Conclusions :

• We need to change the frame from cardboard to a more serious material : we decided to try with Lego Technic ©. They will have the benefit to offer a variety of axis, wheels and gears that can be easily and reliably assembled together
• We have to find an other anti-block system : check next post...

From sketch to first prototype

We decided to use cardboard to build our first prototype of Trevor.

• Step 1 : We created the ovoid shape for the frame on a piece of paper.
• Step 2 : We cut this shape in a cardboard.
• Step 3 : We built the back wheels using cardboard too and fix them to the axis.
• Step 4 : We cut the frame to host the wheels and built the front wheel.
• Step 5 : We prepared axis binding.
• Step 6 : We tested our prototype. The wheels were too narrow.
• Step 7 : We enlarged the wheels.
• Step 8 : Our first prototype is ready.

1st Sketch

Here's our first sketch of Trevor.
We decided to equip Trevor with three wheels to ensure a good compromise between stability and connection to the ground.

V0.1 : the initial shape is a circle. There are two driving wheels at the back and one wheel at the front.
The front side and the back side can be swapped allowing Trevor to progress forward or backward.

V0.2 : we decided to change the shape of Trevor to an ovoid shape as an anti-block system. The anti-block system is supposed to allow Trevor to change direction when he will meet an obstacle. The anti.block system should not use any electric power.

Happy New Year 2014, TrevoR !