EV3 - Toy Quadruped

[oracid]

This kind of quadruped walker has his legs mechanically synchronized and phase shifted.

This walker is simple and effective. Unfortunately, it does not fit to turn.

The difficulty lies in changing the phase shift, to turn, then reset the phase shift to go straight.

To solve this difficulty, I had the idea to use torsion bars fixed between each side motor. In my example, I use 2 symmetrical torsion bars parallel to the motors axis to balance the stresses.

By blocking one wheel and rotating the other wheel, the torsion bars forming an helix, the phase shift is changed, the walker rotates. Then, releasing the constraint, the torsion bars automatically return to their original position and the walker goes straight from his new position.

 

 

[BusterHaus]

I'm not sure why a mechanical solution is required here, despite the fact that it works.  You can physically align two independent motors before starting the program and shift phases as necessary inside the program. You can also track the position of each motor and synchronize them again to walk in a straight line.  The use of a torsion bar seems redundant - I'd like to know more details, I have the feeling that I'm missing something obvious... 

[oracid]

2 hours ago, BusterHaus said:

I'm not sure why a mechanical solution is required here, despite the fact that it works.  You can physically align two independent motors before starting the program and shift phases as necessary inside the program. You can also track the position of each motor and synchronize them again to walk in a straight line.  The use of a torsion bar seems redundant - I'd like to know more details, I have the feeling that I'm missing something obvious... 

The torsion bar solution can be use in simple version without an EV3, like with a Buwizz.

My goal was to make something even bigger than this one with 4 servos. As it worked with 2 servos, I decided to make a new video. The previous one is here, https://www.eurobricks.com/forum/index.php?/forums/topic/162059-little-toy-my-first-quadruped-buwizz/&tab=comments#comment-2974337

I hope to make a new one with 4 servos.

I am not very good at programming, but I have try to do something like you are talking about. The program was far more complicated and it did not work because in this program I had to use the Block Motor with the Brake parameter on Set position. If you look at my program, you can see I always use the Brake parameter at False.

You can't control the servo position without the Brake parameter on Set. Unfortunately, servo has difficulties to reach and to maintain the position. You must know that each leg is 9cm length witch make a big torque.

Anyway, I will be very interested if you do something in this way. Please, show me.

Edited July 31, 2018 by oracid