05/07: Today we obtained more printed 3D parts and are now ready to start assembling some of them. However a crucial part we need to assemble them are M8 screws that are not available on accessible platforms such as shopee or Lazada. However we were able to find them in Jurong Point (Shout out to Kim Able Hardware Store) that have M8 screws in varying length.  We also decided to remove all use of brass inserts in our parts, and instead opt for a small gap in our models to insert a nut, for the screw to be secured in.

7/8: Soldering of PCA9685 and test soldering of the PCB was done! Some small changes was also made towards the 3D design of the seed disperser that was some problem with attaching the different parts during assembly.

Left: Combine the orange round part and black part, leave the hole for the middle m5 screw and change the screw hole size to M1 instead to fit metal servo motor coupler

Middle: The M3 screws initially used to secure the top and bottom piece together is not long enough (longest they have is M3x40). We needed to create a gap in the middle of this bottom red piece for us to insert the nut to hold the pieces together with a screw +Please combine the red top piece and green tubing together

Right: Create a hole on the black piece for us to put a screw and combine the green part together by putting a gap on the middle to insert a insert to secure the screw to

8~11/8: Use of Canva to do our A1 Poster: Including Title, Introduction, Function of & how different part works, as well as future opportunities & improvements. As space was limited, we have to pick and only include vital information and images in our poster. We decided to allocate the most space into the physical parts of the rocker bogie as it is the core of our idea.

 

2 & 3/8: Receive of PCB and soldering of it was done. 3D designing and printing of motor + servo housing to give it more support and make it longer so that it can navigate over rockier terrains. All of the motor was wired up and attached to PCB, and is able to run!

4/8: The hinge used to connect the legs have too much rotational force on it due to the compression on the metal hinge which causes the legs to bent in an outward angle when the wheels are rotating. We tried to use spacers such as nuts and washers to reduce the compression but it was ineffective. As such, further exploration on the types of hinges are available needs to be done to remove or reduce the rotational force.

 

3D printed ball bear hinge have insufficient clearance and space in the shaft area for the other part attached to the other aluminum profile to rotate smoothly. We made it tighter and thinner for clearance and was able to attached it to the legs.

Once everything was assembled and attached to the body, we realized that the overall angles of the aluminum connected to the motor and servo housing are not leveled so changes had to be made. As such, changes to the angle where the rocker joint and motor + servo housing is attached to the aluminum profile was adjusted so that all the pieces are leveled and stable We also designed a part that can fit into the groove of the wheel for the coupler to be attached to.

The changes made to the motor and servo housing allowed the legs to be leveled and stable. Upon attaching both legs and testing out the motion, we found out that the ball end joint is slightly angled and not parallel to the legs. This caused the right leg to be bent inwards if the left leg is tilted up, due to the pivoting of the differential bar. As such, the differential bar was made to be longer to fix this issue. Also the PCB was ordered 🙂

 

17/7: We continued exploring the fuse, voltage divider, PCB connector and Ina219

18/7: We had our 3rd presentation to showcase our progress and changes of our project to our professors

20/7: Abigail have returned to Singapore! so we had her look at her current and previous designs so that she can understand what went wrong and what was successful. As mentioned in other posts, one of our current challenges are applying the appropriate bearings to our design for the rocker bogie’s leg to rotate smoothly. As such, we explored the use of hinges and the use of shaft in ball bearings. The use of hinge requires a tapping screw that we do not have, while the ball bearing application requires us to design another 3D part to be attached to the AP.

21/7: Failed to connect to Dlink camera as they have their own server

 

10/7:  All the changes implemented into on our 3D models have been made and the second prototype parts were printed. First prototype was disassembled to reuse the aluminum profiles and we were able to assemble 1/4 of the rover. However, we failed the first trial the PCB and are still deciding what will be used for communication on the user level, a source for battery (drone?) and good voltage regulator (protection?). We will also be using a 24V battery, step down 3.3V for logic and 5V for power (giga, rpi, camera, router &servo).

12/7: We decided to throw away pi, use wifi direct to giga, decided on a one 5V step down regulator and decided to add imu

13/7 : Besides more printing and assembling, we finally got to cut the aluminum profiles today. We decided on linear bush bearings and metal rod for pivot and tested giga(blink) over wifi

14/7: The body of the rover and the remaining legs was fully assembled, however the legs cannot be attached to the body of the rover yet as we lack the necessary screws required. The rocker joint and rocker to chassis parts will be combined as putting them into 2 separate parts are not necessary and troublesome. We are still improving the pcb design and hope to purchase linear bearings and couplers soon.

We finally got all the material to put the legs of prototype 1 together and got to assembling but came across some unexpected issues a long to way. The use of deep-groove bearings was not applied correctly in parts that requires rotation as there is still not enough clearance between the pieces to rotate smoothly. As such we have to explore other options and ways to make the bearings work.

The size of the nuts that came with the M8 screws purchased previously was also too big for the nut grooves placed in the parts, so it requires amendments. We also decided to combine the servo housing with the motor housing leg pieces together, and turned the ap from the servo housing to be fully 3d printed instead of using aluminum profiles.

Additionally, a 3D printed mold was done to assist in the making of the seed pods and provide a consistent round shape of ~3.5cm

03/07:

We discovered that the aluminium profiles require a specific 20mm x 20mm aluminium bracket so the surface change of our 3d models have to be tweaked. The grooves on the back of the 20mm x 20mm aluminium bracket was measured and taken into consideration so it can fit on our 3d printed models

– Changed dev mode to 2

– Got the giga to control the motor (Pam too fast for motor)

– Got PCA9685 to control motor

– Tony suggested using PCA9685 to control all pins for DRV8874

04/07: We printed the 3D parts that connects the aluminium profiles on the side and the part that connects the wheels to the body (joint). We also printed the servo housing and legs We also that the 3D model of the differentiator is too big (40cm+) for the lab’s 3D printer as it can only print a dimension up to 20x20x20cm. As such we broke the differentiator model into 3 parts, using the tongue and groove method and screws to secure the pieces tightly together. We changes the 3D printed piece below the differentiator into an AP for more strength, it has its own 3D model design and print to connect those 2 pieces together.

Test motor strength & current, decided on servo min & max of 145 & 545, use pca9865, assembling of rocker bogie middle legs with aluminum profile

I2c board not working, tested motor with 1298 n to be working. We also set up a GitHub account & use motion study to test out the movements of our 3D design to prevent future errors and collision, especially the leg pieces