Machine Control Design

In this project, students were divided into teams which were given different Vex V5 based machines that they must design, construct, and program within a given time constraint. The teams must do research to find inspiration for their design, determine the optimal design from their research, and then create their own design. From here the teams must begin to construct and program their designs with the provided Vex V5 parts and software. They then must test their builds in order to ensure functionality. The aim of the project was to provide the students with familiarity with teamwork in engineering, deal with deadlines and time management, learn to research and design solutions, and work with Vex V5 parts and code. 

My group consisted of myself, Lachlan Stapleton, Brady Kaiser, and Anirudh Bhat. We were given the surgical robot arm to design and build. The objective of the surgical arm was to create a remotely operated arm that had 3 degrees of freedom and could move opjects in a sterile environment. It must have a pivoting base, an arm that raises and lowers, and some sort of claw that can grasp objects. 

Research/Development

These two sketches are examples of sketches that we made with inspiration from our research. These ideas helped us determine what we wanted to incorporate into our final design. We also used these to show us what we didn't want to do. For example the fixed bases were something that we decided to stay away from and instead opted for a rotating base on top of which the robot arm would be held.  The sketch on the right feature sprocket and chain systems that we ended up incorporating into our final design. In addition we fixed our claw arm onto a gear in order to move it up and down, similar to the sketch on the right. 

Our psuedocode ideas were pretty similar as at this point we had determined what our inputs would be. We decided that we would have one potentiometer which would determine which motor was being activated along with two bumper switches which would determine if the motor would spin forwards or backwards.  For this reason they both scan for potentiometer angles within certain ranges. If the angle was within a certain range, it would activate the corresponding motor for each of the four motors present. The main difference in the code was that for the first idea, it was built more segmented and allowed for the motors to be activated as long as the bumper switch was pressed. On the other hand, pseudocode 2 made it so that the motors were activated for short durations of time when the bumper switch was pressed. 

Final Product

The potentiometer determines which motor will be activated by the bumper switch depending on the angle it is at. On the right end of the baseplate is where our main motor was kept. We used standoffs to elevate a plate over the motor. This motor spun the whole robot when activated. On top of it was a gear train that allowed the motor to spin the robot.  Further up and to the right is our first 2 wire motor. This motor controlled the sprocket-chain system which moved a pair of C-channels up and down. These C-channels have the second 2 wire motor which moves the claw arm up and down. These two joints can allow the claw to go up, down, forwards, and backwards. Finally we have the claw which was preassembled. The various large wheels were used as counterweights to keep the system balanced.  One major problem with the design was the weight. The joint that connected the sprocket-chain system to the claw arm was not strong enough to bend properly. The claw weighed it down and would cause the whole joint to drop. This was a big problem that we weren't able to fix. In addition the weight caused problems for our main motor that rotated the base. The weight of the whole robot arm was initially too much for the motor to rotate on its own and we ended up overloading a motor when testing. We countered this issue by using a gear train which provided a more favorable gear ratio, allowing the motor to spin the system.