The team has been hard at work during April with the focus on preparing the robot for testing very soon. We made some great progress on the electrical system and the manipulators.
Having received the PCBs and the electronic components from Farnell, earlier in April, the electrical team started assembling the custom boards.
The first of these boards is the Communication Board, which is responsible for all interfacing between the Microcontroller and the Surface Computer, it has an Ethernet Controller to facilitate this communication. It is also responsible for interfacing between the Microcontroller and any low power ROV Manipulators, such as the Ultrasonic Transducer and Video Cameras. The ROV is controlled from the Surface Computer over Ethernet using UDP protocol, so this board is essential to ensure that we are sending and receiving data appropriately.
Avalon's Communication Board
The second board is the Surface Board. This board will be on the other end of the tether from the Communication Board and will act as breakout of the signal received from the Communication Board, including video. Because, we are using analogue cameras, the data is sent as a differential signal, and the Surface Board converts it back into a signal suitable for the DVR. As the data is sent down the same CAT5e cable that carries the ethernet link, the board also has to split the ethernet off to a second RJ-45 connector.
Avalon's Surface Board
The Mechanical Team has also been busy working on various manipulators and attachments. The first of which is a pneumatic gripper. The Gripper is designed to carry various objects and manipulate PVC pipes. It is comprised of a main gripping body and a double acting pneumatic cylinder that extends to provide an opening of up to 9.6mm, ensuring enough space to pick up the designated objects. The main body was designed to occupy minimal space whilst meeting the constraints of objects to be carried. The choice of using acrylic sheets for manufacturing was primarily due to their light nature, ease of laser cutting and wide availability. A rubber grip front was used to increase contact friction ensuring any object carried does not slip underwater. Here's a video of us testing the gripper:
A video of Avalon's pneumatic gripper
One of the missions this year involve attaching a lift bag to debris underwater and inflating the lift bag to move the debris away from a sunken aircraft engine, before releasing the lift bag to drop the debris in a different location. To achieve the highest score on this mission, teams have to release the lift bag wirelessly when it is moved away from the engine. In order to do this, the mechanical and electrical teams worked together to design the following hook, which can be used to easily attach the lift bag to the debris. Once the debris has been moved away, a push-pull action solenoid will be used to open the hook, thus releasing the bag.
Avalon's lift bag release mechanism
To activate the solenoid, the team designed the Release Board, which will be incorporated into the lift bag mechanism. It consists of a ultrasonic transducer (not in the picture) coupled to a series of op amps which detect the presence of an ultrasonic signal. This is fed into a microcontroller which searches for a unique pulse-train. On receiving this pulse-train the microcontroller will activate a MOSFET, actuating the solenoid that releases the airbag.
During the following two months, the team will be working on various technical documents to submit to the competition organisers. We will also be integrating all the different components, in time to start rigorous testing in June before the competition.