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.

Pre-checkoff Update

As of Wednesday, May 22, the POD successfully senses analog inputs and forwards the data to the ROAMER. An error in which the POD does not reconnect after a disconnect has been fixed; however, an error remains in which other teams' broadcast signals seem to break the connection.

The SPECIAL communication with the SPECIAL PIC and forwarding to the ROAMER brain was also successfully implemented. Transfer of all circuits to protoboards is nearly complete. Processing and output of commands by the ROAMER is next on the schedule and will be completed for the checkoff tomorrow.

Tuesday Checkoff Success

The team was successfully checked off late on Tuesday. Communication nodes were all successfully implemented with the exception of the SPECIAL PIC, which was tested the previous Thursday. In the state at which the project was in for checkoff, the following items were implemented and functioning:

- The POD brain could successfully sense and send digital inputs and send the state of these digital inputs via SPI to the POD radio PIC. This "command" was implemented using the framework of the communication protocol. The POD brain could also receive the "status" from the E128 (via SPI communication with the POD radio PIC) and successfully execute broadcast/ connect and disconnect actions. In situations where the ROAMER fails to reply, the POD disconnects and puts out its "connect status" light.

- The POD radio PIC could successfully receive the command from the POD brain and simultaneously send the status of the E128 to the POD brain. Upon receiving a command from the brain, the radio PIC would immediately build the data packet and forward to the POD XBee, which would transmit the command to the ROAMER XBee.

- The ROAMER XBee would successfully receive the command from the POD and forward the command to the E128/ brain. At the same time, it would receive the E128 status from the brain and send this information via asynchronous communication to the XBee radio, which would transmit it to the POD.

- At the time of checkoff, the SPECIAL communication was not implemented but was shown to work during the previous checkoff, in which the SPECIAL PIC communicated the status of the SPECIAL to the E128.

ROAMER Drive Test

Attempted driving over carpet (6.7V applied to TLE-5206 H-brdige)
Able to drive over hard ground
Unable to climb onto carpet
Very slow/sometimes stops moving while on carpet

Solution: Chain two batteries to apply 14.4V supply voltage

Making Circuits

Wired up perfboard with ROAMER circuit board
Put regulator, place for E128 ribbon cables, ROAMER select switch Molex
Wired up servo for turning SPECIAL

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