Pre- Grading Session Update

As of Wednesday, 5/29, all systems are fully functional and should be able to accomplish the tasks outlined for the grading session.

As an update after the last post, the connection LED and ROAMER select switch were implemented, and our POD and ROAMER successfully connect to and run with the PODs and ROAMERs of other teams. The castors (made from PVC) on the bottom of the ROAMER were decreased in height, allowing the ROAMER more flexibility to take bumps on the carpet, and friction problems were addressed in the drive trains; this fix appears to address the issue of difficulty driving on carpet. Gripper height was increased, which fixed the problem of losing the box when dragging it over the door threshold. SPECIAL mount was attached to the top of the ROAMER. The bottom of each castor was sanded. A nonlinear mapping was applied to the incoming voltage received by the ROAMER before outputting the PWM frequency in order to make for increased sensitivity/ turning ability at low voltages. Vinyl was applied. The POD and ROAMER can now drive on carpet, drag a box out of the larger box, and control/ be controlled by other teams' ROAMERs and PODs. POD and ROAMER are ready for grading.

Update 5/27

5/27/12 Update:

The POD and ROAMER have achieved basic functionality, with some adjustments still to be made.

Circuits have been in their final state since 5/23, with a final decision to implement an H-bridge in the gripper circuit to allow additional current to flow for greater grip strength.

Software is largely finished with some minor tweaks to be made. There are still occasional problems upon connection with the ROAMER: the POD does not always register a connection immediately, and the connection occasionally breaks. These issues were largely mitigated, however, in the last couple of days, and additional fixes targeting unwanted incoming signals will be implemented as well. A major bug involving the POD software getting stuck in a while loop during the AD conversion sequence was fixed, eliminating most of the break-mid-connection problems. Connection LED and ROAMER select input will be implemented in the next day or two.

The POD mechanical structure is in its final form. The ROAMER has been built, and minor adjustments outlined after initial testing remain: the ROAMER does not drive well on the carpet, has trouble going up hills, has trouble with fine gripper movements, and fails to drag the box over the door threshold because the gripper height is limited. Fixes will be designed and implemented in the next two days.

CADing the gripper and SPECIAL

Worked on CAD of top half of ROAMER

Have dropdown level from top to hold door lock motor
Currently, gripper is flush against top plate
  If we find that the pin that attaches the gripper to the motor likes to turn from vertical, we can drop the gripper down 1/4" and add a piece of loose Duron between the top plate and the gripper (with a hole in the Duron to stay on the pin/screw)

Discussion of Drive Train

Discussion of Drive Train Design Decisions:
Decided on wheels to be purchased - 4 in. diameter wheels from ServoCity
Clearance under drive train estimated at 1.25 in. - should allow for surface compression estimated at 1 in.
Decided to re-use 218b project components: brackets, wheel mounts, axles
Discussed advantages of two sliders versus one slider (i.e., three points of contact) - three sliders means no chance of full weight of ROAMER being placed only on sliding supports
Bottom-mounted drive trains will allow maximum clearance and additional room for electronics components resting on base