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After a few quadrupeds, I try an intrusion towards the bipedal mechanism. Not easy ! But, I hope to bring my brick to the building.

Here, you can see my last quadruped. But, yes, I guess it is possible to make a quadruped with flex-leg. The goal is to move servos on the chassis for more than 2 DOF without any heavy mechanical transmission. Another way is the "Spherical Parallel Joint". They are many examples in YouTube. I don't know if I will be successful myself, but if someone does, I would also be very satisfied.

Thank you all. I use an Arduino Uno and a Sensor Shield V5.0.

Thank you. Lego pieces are amazing and I have used them for a very long time. For me, these are pieces of plastic that I do not hesitate to cut, sand or glue and to associate with other technologies such as radio control servos and microcontrollers such as Arduino. All this gives me exceptional design options that I invite you to share.

Thank you. Happy new year to every body.

This time, I show you a flexible robot leg. I believe this linkage is very new. I hope, one day I will make this biped walking with this movement.

Here is my last video where I show a quadruped running at 1m/s speed.

FourBarQuad525 is a quadruped that weighs 525g. Unlike my previous quadruped, https://www.eurobricks.com/forum/index.php?/forums/topic/181228-fourbarquad550-light-and-speed-quadruped/, it is equipped with the MG92B servo which has a torque of 3.5kg.cm against 2.2kg.cm for the MG90S. This allowed me to increase the size of the femur, the rudder, by 8mm, or 1L (Lego unit). It may seem ridiculous, but on this scale, it is not negligible. In this video, I show that this quadruped goes at a speed of 15s for 8m, or less than 20s for 10m. For comparison, the last TRR (Toulouse Robot Race), I have prevailed with over 40s to 10m. I think less than 10s for 10m is accessible, but with faster servos. Because there, from a programming point of view, I can go much faster, but the servo does not have time to reach the setpoint.

The goal here is to make a very light and very fast quadruped robot.

Here is a shoulder study for a quadruped. Here I used 2 MG90S servos. The volume of the mechanism is very compact and its weight is around 40g. I have to say that I am quite happy with the result. As can be seen in the video, the shoulder can lift around 250g. To be tested therefore with a 1kg quadruped. The mechanism looks like a 5 bar, but it is not. It allows the coupling of 2 servos without worrying about the alignment of the axes of the servos, the position of the axis of rotation and the position of the axis of the mechanical coupling with the leg. This seemed essential to me because of the alignment problems of the servos with the Lego mechanics. I would be very surprised if my mechanism was original, there are so many of them, but I would like to know what mechanism it is.

Thank you. The tail is to charge the battery. Lego is a great tool for creativity. Nothing else for me !

In this new video, you can see my last quadruped. The novelty is the big size of this quadruped. Nevertheless, I managed to get a light weight thanks to the use of large plates that I cut to the right size. This technique makes it possible to obtain very large and very rigid structures for a very reduced weight.

Very good movement control !

It is not easy to find the good gaits. In my quadrupeds I use to draw a rectangle. In my last video the rectangles are not symmetrical. The rectangles of the back legs are a bit on the back. In addition, in your quadruped the masses are not symmetrical. So you have to compensate. At the end of the legs, I sticked chair leg pads. At the moment I think that is the best.

This is very good ! I would like to see more walking. When turning, try to make one side legs forward and the other side backward, like a tank. Why the end of the legs are so complicated ? Rubber is not needed.

So good !!!

Hello everybody. Here is my last video. In this video, I made a 4 bars linkage quadruped instead of 5 bars linkage in my previous quadrupeds. This is very important for acquiring more knowledge in this area.

Here is the final version of my 4BQ-1 project (FourBarQuad-1). I completely redesigned the servos block. I positioned the servos on the front and no longer head to tail. I replaced the ultrasonic rangefinder by a Laser rangefinder, the VL53L0X, it is the very small black rectangle on the front panel. The weight is 860g, which, in my opinion, is the extreme limit that can support SG90 servos. The video is coming soon. In the meantime, here are 2 photos.

I hope this will inspire you.

This looks very interesting ! But as far as I can see the wheels motors are not yet on board. Do you intend to use SG90 servos with continuous rotation ? If you are interested about mixed technos, Lego, Arduino, RC, 3D Printer, please have a look at my YouTube channel.

What about this ? These do not work, but I will soon present one that works in this thread, https://www.eurobricks.com/forum/index.php?/forums/topic/175266-fourbarquad-1-4bq-1-quadruped/

You can do this.

Here is a new mechanism that looks more like a real quadruped leg. In this video, I show that a parallelogram with an extension can be considered as a simple parallelogram. This greatly simplifies the calculations.

In this video, I show a quadruped leg based on parallelogram linkage. Usually, a 4 bars linkage has 2 sides consecutively egal , and the 2 opposit sides egal too. You can see it here : https://www.eurobricks.com/forum/index.php?/forums/topic/175138-4-bars-linkage-with-parallelograms-actuators-for-quadruped/ This is too a 4 bars linkage, but with parallelogram frame.

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