Review of Group B Final Design: Remote Sensory Vehicle
Jeremy Coriell
Ha Le
Jeff Phillips
Overall Design
The team has done a good job of finalizing design specifications and integrating components for this ambitious project. They have made great progress in the design and layout of the various portions of the project, and it appears that they will achieve most of their goals. There are still a few final obstacles the team must overcome; however, and we will examine these areas of concern below. As in the preliminary design review, we will break up the design into the functional areas of movement, sensors, wireless communications and video.
Much more design and testing has been put into the movement systems of this project since the time of our preliminary review. The group has addressed all of the previous issues that came about, and appears to have overcome them. The transitions between autonomous and user control and the source-reallocation algorithm are now better defined, and they look like they will work. The team has also ensured that motor damage cannot occur, by using relays and control logic to disallow simultaneous conflicting signals to the servos. The XSV board has been proven to create good control signals in manual user mode, and functions correctly for this purpose.
The only remaining concern that we have with this area of the project is in simple user-friendliness. At the current time, the group is not displaying any information to the user about the camera orientation, and we believe that this could prove cumbersome to new users. For example, if the camera were pointed 90 degrees from the direction of travel, the scene would appear to move sideways when the user pushed the up key to go forward. This is certainly a minor detail that was not in the original system requirements, but we believe it may add a small degree of usability to the system.
Our previous concerns regarding the communications protocol between the vehicle sensors have mostly been responded to. The group has put a lot of thought into this portion of the project, and we believe that their synchronization setup will work. They have a clear idea of how fast their system needs to run, and the numbers show that they will have plenty of time to do the necessary tasks. The system is more complicated than the I2C protocol, but this is superceded by the additional control that they have gained over the system’s timing. The power consumption issues have been resolved with capacitors, and thus the rest of the system will not be disrupted by power supply surges. The data format used by the sensors also seems to provide a simple, neat package for their system data; however, it may have been easier for conversion purposes to run the numbers in metric.
Although the group has overcome most of the obstacles in this area, we still believe that sensor interference may still be a problem. The synchronization between sensors on the same bank is very well defined; however, no control is currently provided to prevent sensors on opposite banks form firing simultaneously. This generally shouldn’t be a problem, but it could cause false readings in tight areas where reflections could occur. The sonar has a 30-degree cone of “sight,” and could thus catch bouncing signals from the opposite end of the tank. Although this is a minor detail, it seems to need consideration since false signals can cause the vehicle to behave improperly.
The group has made a lot of progress in this area of the design as well. As suggested, they have removed the line-powered transceivers from the system, and are using simple logic levels for communication. This allows for a much simpler communication scheme. They have also taken package collision into consideration in their system requirements, allowing them a proper time frame for the vehicle. All of the concerns we had in this area seem to have been corrected, and it appears that this portion of the system will work.
The choice to switch from a VGA monitor to a simple NTSC television has greatly simplified this portion of the project. The data is already in the proper format in the camera, relieving the need for complicated conversion algorithms and floating point math. This solution also avoids the necessity of double buffering in the system, so ram contention issues will no longer be a problem.
The only data displayed on the VGA monitor in the new design will consist of the sensor data from the vehicle, and some vehicle state data. We believe that the data format used for this display is very good; however, the group could avoid some redundancy on the display be simply highlighting the rangefinder data for the nearest obstacle, rather than giving it its own display. Also, users of the system would most likely benefit from on-screen camera orientation information. Again, these are simple usability issues that could possibly be considered as further system additions.
Overall, group B has made very good progress on their design. This project was very ambitious, but the group seems to have met all of their system requirements. They have paid close attention to the electrical and timing constraints of the system, and have taken these into account. We believe that this well-planned design should be successful, as long as the system integration does not bring about any unforeseen issues.