A large part of this week was spent reviewing previous reports from the summer 2016 group, and trying to come up with clear design specifications. From the reports completed prior, it doesn't seem like there are clear requires for components such as time for steering to switch or weight values for cabin and suspension. These are important values because they dictate the strength requirements for the members. This Wednesday will be used to come up with clear design requirements. From there, the work load will be split between us to complete the goal.
In addition, to reviewing the old design, I had to complete some tasks as president of Superway. I completed the recognition application as well as looking into funding for the project. I wanted to get a polo shirt design together in order to have something for people to wear to events such as maker fair.
Design work that was complete this week was a discussion of how to model the steering system in order to come up with the equations that will define the input speed requirements for our actuators. The discussion of what kind of actuators also took place. Currently, the debate is between a linear actuator and a high-torque servo. There are advantages and disadvantages to both, but the defining variable that will more than likely determine it will be the speed requirements for steering changes. Linear actuators are in general slower with the faster ones have a much large volumetric footprint. This could be a problem for us. The solution could reside in a servo motor to actuate the movement. We are also currently planning to have two actuators running with one a slave to other to actuate the upper and lower steering mechanisms. The distance between the two is too great and would a require a complex linkage system that would have long members that would either need a lot of mass to be structurally sound or be quite thin and may buckle.
Another design decision that has been made is to create a three wheel system for the lower rail. Currently, there are two wheels lying in a vertical plane with each other. This allows for rotation to occur about the rail which is causing binding in the upper guide wheels. The three wheel system would counteract this rotation and in conjunction to a 2 DOF of freedom jointed bar between the two bogies, would allow both bogies to be perpendicular to the rail, but independently of each other. This is an additional solution to the current binding issue.
A redesign for the steering system is currently in talks as well. The lower steering arm was dropper down relative to the rail in the previous design, without being modified. The previous teams solution was to place the wheels of the steering arm on long rods in order to put them in the right position. A redesign of the arm could extend them and have a cut out for the lower wheels and place the wheels in the right position without the long rod. All the wheels should be on bearings or at least shoulder bolts that have shoulders with the right length for the wheels to rotate freely. The current design doesn't allow for some of the wheels to rotate freely.
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