StasisV3

OVERVIEW

The Reshular Robot Arm is a 6 DOF robotic arm. It is operated over bluetooth so it can be operated remotely. 5 stepper motors, using the TMC2209 driver, and 1 servo motor is used to make this huge robotic arm.

Purpose

I made this because I've always been fascinated on how to use technology to make an impact on the physical world. I've seen small robotic arms powered with servo motors. But I noticed that scaling it up in size changes the materials I need and introduces (newish) problems like insufficient torque when using a servo motor. These robotic arms are also shorter ranged and can only hold very light and small items. Thats why I built this robotic arm. I can lift items that are impossible for small robotic arms like a big book. The most important thing is that I became way better at eda since this is my first project that uses a smd PCB.

Schematic

There are 5 tmc 2209 motor drivers. They are almost identical. Only their gpio assignments to dir and step changes and also their uart configuration.

So how did I configure it and how can you too?

The tmc2209 talks to the esp32 via UART. But four tmc 2209s share one uart line. Wait, there's 5 tmcs, not 4! How could that be? Well, the ID for uart is dictated by the whether your ms1 and ms2 are pulled high or low. Since there are 2 states and 2 pins, 2^2 is 4. So you get 4 combinations. To account for the 5th tmc 2209, I just used another set of gpios.

The ms1 and ms2 pins also happen to control microstepping, and thats pretty important if you have something like an EV or a robot arm like this. So I put the finer microstepping onto parts that actually matter, such as the elbow joint. You can find further details via the datasheet for the TMC2209 and the exact configuration in the PCB file that I have.

PCB

Now lets get into the PCB. The specs of the PCB isn't anything special. It is a 2 layer pcb, and thats exactly why this is good. It's theoretically not gonna perform as well as a four layer board (well not really because this is a 2 layer board thing). But since its only 2 layers, the cost decreases significantly. There are two layers of electrical protection. The first one is the NCP1117 (well not really? but if it dies the circuit becomes open so I guess it is protection), and the second one is the TVS diode. The TVS diode is a component that protects your circuit when the voltage/current reaches a certain threshold. For something like a robot arm, you will defininately one that.

Model

The purpose of the model is not to make it look good but to make it as light as possible to test in real life. It features 6 degrees of freedom, which could move (almost) ny item in any way you could think of. The base has an hexagonal pattern which maximizes strength, aesthetics, and filament efficiency.

Motor joints

Well, how does each joint work? Its actually quite simple. You can tell by the picture that the stepper motors are directly attached to each joint, so no special pullys or anything! This saves complexity and cost. For the gripper, its a little different.

The central gear meshes with the two side parts. When it spins, the two grippers come together and, well, grips. Spinning it the opposite way retracts it. You can try it out in this link. https://cad.onshape.com/documents/dfb7d85a38278a669fcebbb5/w/2d92252d034fc83197e6695c/e/ec9dc79179103d4b89a939a4?renderMode=0&uiState=6a322868ee269b265a1ceec7

As you can see, the motor is directly attached.

Testing

N/A (will include after getting parts)

Bill of Materials