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Jim posted a topic in LEGO Mindstorms and RoboticsMINDSTORMS EV3 OMNIDIRECTIONAL ROBOT INTRODUCTION The reason you are stuck with me as Moderator/Admin is actually caused by Mindstorms EV3. I proposed an Index for Mindstorms and Bonaparte figured I could make one myself. Resulting in me making one, and one thing lead to another. In 2013 TLG released a brand new edition of LEGO Mindstorms. Owning two NXT sets, which I had hardly used to build something cool, I was determined to change that when I bought the EV3 sets. I first bought the 45544 - EV3 Education Core Set set, and shortly after that I added the 31313 - Mindstorms EV3 (Retail) set to my collection. After some initial experiments both unit had been turned on approximately the same number of times as the NXT. This being a terrible waste of potential, I recently decided to start building the robot I have been planning in my mind for a long time. My goal is to build a fairly big humanoid(-ish) robot. Does that sound familiar? Of course it does, since my good mate Simon Burfield (Burf2000) has built a super cool humanoid robot recently. We also know him of the Wheelchair and Segway. And yes, he is a big inspiration to me. What I am aiming at is a Omnidirectional Robot with one or two arms and a Wall-e like head. The height of the robot will be approximately the size of a child, let's say around 120cm. Omnidirectional means allowing movement in all directions (more on that in the next chapter). Since I have no idea where this will end, I have created a WIP topic, in review style. I will add chapters along the way. When I add a new chapter I will post that new chapter and edit the original post. Feel free to comment, hint, tip, suggest, mock and ridicule Before we continue I'd like to give my man Burf and the guys at Rotacaster a big thank you! OMNIDIRECTIONAL WHEELS Here's the wikipedia description for Omni wheels: Omni wheels or poly wheels, similar to Mecanum wheels, are wheels with small discs around the circumference which are perpendicular to the turning direction. The effect is that the wheel can be driven with full force, but will also slide laterally with great ease. These wheels are often employed in holonomic drive systems. A platform employing three omni wheels in a triangular configuration is generally called Kiwi Drive. The Killough platform is similar; so named after Stephen Killough's work with omnidirectional platforms at Oak Ridge National Laboratory. Killough's 1994 design used pairs of wheels mounted in cages at right angles to each other and thereby achieved holonomic movement without using true omni wheels. They are often used in small autonomous robots in intelligent robots research in the academia. In projects such as VEX Robotics, Robocup and FIRST Robotics, many robots use these wheels to have the ability to move in all directions. Omni wheels are also sometimes employed as powered casters for differential drive robots to make turning faster. However, this design is not commonly used as it leads to fishtailing. LINKS Some interesting links: Omniwheels Mecanum wheels Ball transfer unit Holonomic Festo After 15 seconds you can see the Kiwi Drive in action: Control using gamepad ROTACASTER Here's the complete lineup for Rotacaster wheels with LEGO hubs. From left to right: 125mm 48mm 35mm As you can imagine the 125mm version are for heavy duty applications. Since the robot will probably by quite heavy, I figured the bigger the better. There's also a 125mm version with 3 wheels instead of 2. However, this will probably suffice for my robot. The diameter of the 125mm is slightly larger than a 15L liftarm and the width is slightly less than 6L. CONCEPT Here's a simple concept sketch. And an artist impression of how the robot should look like. The end result will probably look nothing like this one, but it's nice to have an idea. PROTOTYPE I have started building the prototype. The idea was to buil in a modular fashion, but this early concept failed miserably. VERSION 2 The triangular shape poses quite a few challenges. Not that I hate a challenge, but I am contemplating on making a four wheeled version. The idea is to create 4 standalone wheel units, which can be attached to a center hub, possibly with shock absorbers. The red liftarms underneath need to be removed, because they will prevent the wheels to be mounted. This is just a simple LDD setup I drew, since we discussed Bob's problem with turntables. That made me rethink my setup. Some turntables and dog bones for the new setup. When using the modular setup for the wheels, I could easily switch between different setups, three or four wheels. My progress is what you see in the pictures. Now let's have fun discussing and mocking. Alasdair mocking in ...3....2....
This is something I made quite a while ago but I never finished it. It worked really well as a unit but the axles let it down. They were based off of someones concept car who I can't remember the name of.Like Nkubate's hurricane it has differentials between the left and right wheels instead of the front and back. This allows it to be slightly easier to control. I have an LDD of it which is mostly complete. Finally here is a video: