Redesigned SPM with RPI control system

thingiverse

This Spherical Parallel Manipulator was originally printed with all of the parts from the original model by plusalphaDesigns (See the second last photo). From there changes and alterations were made to improve the build to make it more efficient and suited to my needs, as well as a whole new control system using a Raspberry Pi. What was kept the same: The central gears and all three sets of links were kept the same from the initial build, as no real big changes could be made for these parts without massively changing the designs to put in bearings to help reduce friction. As well as this all of the pins were kept the same. These parts from the original plusalphaDesign build were: - Gear Level 1 - Gear Level 2 - Gear Level 3 - 90deg Link : 3ea - Link Level 1 - Link Level 2 - Link Level 3 - Link Pin : 3ea - Stack Pin - Stage Pin : 3ea Changes The main mechanical changes in the new build were: - The use of Nylock nuts to stop the nuts on the joints coming loose that seemed to happen often. - The Top Stage was redesigned by measuring the 3D print and 3D modelling one exactly the same size as it to allow it to fit onto the original links. Then a cut was made into it the same size as the camera used in the build to allow it to sit in nicely, with a hole in the bottom to allow the camera to be screwed in. The camera used can be found here - https://www.amazon.co.uk/gp/product/B07RXYG295/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1 - The original build had a 1:1 gear ratio, in this build this was changed to a 2:1 ratio to improve the torque in the system and allow it to comfortably carry more load. By keeping the central gears the same size and then reducing the diameter of the servo gears from the original 40mm down to 20mm this gear ratio was achieved. - With the newly designed base, this made room for some more changes. The large triangular base made the design more sturdy and unlikely to tip, as well as allowing for an arrow on one corner to be made to show which way the base and the system should face. With the new smaller servo gears, the servo mount brackets had to be moved closer to the central gear shaft to allow for this smaller diameter. Some calibration markers also were added, this allowed the servo gears to be set at a zero point and then give an easy visual aid as to where the gear has moved. As well as this, all links that touched eachother had metal washers added to them and were sanded down to try and reduce friction and make the system as smooth as possible. Certain parts such as the motor brackets and gears heights were slightly lowered to make the gears all line up more flush to stop any gears getting caught. Electronics All of the electronics were controlled by a Raspberry Pi 4, however a Raspberry Pi 2 or 3 should work perfectly fine for this purpose. The 3 servos were powered from an external power supply. An app on Tkinter was created to control the servos directions and movements as well as relay back real time data on the servo positions. To get this data back into the RPI, an MCP3008 ADC was used to convert the signal from the analog feedback pin of the servo to a digital signal for the RPI to take in. This data was then presented in number format as well as graphically for each servo. The electrical schematic can be seen in the last photo. A video of the system working with the app at the same time can be found here: https://vimeo.com/726521642 The python code for the Raspberry Pi has been included, a number of libraries seen at the top of the code have to be downloaded. What to print: As well as the things mentioned above from the original build that need printed off, you will also need. - Redesigned Base - Redesigned Top Platform - Calibration Marker : 3ea - Smaller Gear : 3ea