Please Crique

[Kevin Selavko]

Can you please give me your comments in this. It is one of the documents we would give to potential sponsors when we speak to them about providing money for a CAN system:


With encoders, the robot is able to determine the exact speed of its motors, the motor’s direction, and the exact position of the motor. The robot senses movement by monitoring changes in the pattern of the signals generated by the encoder. Each encoder generates two sine waves while it is active. Speed is calculated by the frequency of the signal, and direction can be determined by the offset of the two signal patterns. Exact position data is calculated by counting the number of pulses and the direction of the motor.

This is very useful, but it puts an extra strain on our main processor, the C-rio. The C-rio is a very advanced piece of hardware, it currently handles all of our visual tracking, sensor input, human input, running the main code, and giving out data to all of our digital and analog devices. This overworking of the main processor can lead to slow response times, unsafe operation, and failure of the whole system.

We would like to incorporate a CAN(Controller Area Network) system into our robot. CAN is commonly used in cars for many uses including: locking doors, transmissions, cruise control, and airbags. On our robot it would allow for two way communication between the C-rio and its motor controllers, in place of the one way communication we have now. With two way communication, our motor controllers would be able to process their own encoder data and act upon instructions given by the C-rio. This would allow for more accurate motor speeds with a faster response time of the robot. While the motor controllers would become more self sufficient, they will also send processed encoder data, such as the speed and position of the motor to the C-rio.

[Brandon_L]

Originally Posted by Kevin Selavko

With encoders, the robot is able to determine the exact speed of its motors, the motor’s direction, and the exact position of the motor. The robot senses movement by monitoring changes in the pattern of the signals generated by the encoder. Each encoder generates square waves while it is active. Speed is calculated by the frequency of the signal, and direction can be determined by the offset of the two signal patterns. Exact position data is calculated by counting the number of pulses and the direction of the motor.

Thats the only big thing that stuck out to me. The details you described are a bit fuzzy but It should be alright for a general description of how it works.

Is there an introduction paragraph? I seemed kinda just thrown into.

[jee7s]

I'm assuming you want a "critique"...

You make a lot of valid points, but the biggest thing I'm not seeing is the "ask". What is it that you need the money for and why do you need those things? Sure, most of us in FRC know you'll need a crimper, some 6 conductor cable, 6P6C connectors, terminations, and either a 2CAN or serial bridge. But, you donors probably don't know that. Make sure you explain that to them clearly.

[Kevin Selavko]

Is it square waves? No it does not does not have an introductory paragraph yet, I was planning on writing a team/what FRC is, page that would go in front of it. Also I did not want to go into extreme detail so that they would not get bored, is this acceptable or do you think I should be more precise in details?

[Kevin Selavko]

Ask is here:https://docs.google.com/spreadsheet/...LbkowNWhBd EE

[jee7s]

Originally Posted by Kevin Selavko

Is it square waves? ... is this acceptable or do you think I should be more precise in details?

It's actually a couple of digital signals that are toggling to the on and off states, but strictly speaking it's not a "square" wave with regular period and 50% duty cycle.

I'd say you generally have too much technical detail. Personally, I don't like the idea of a directed technical pitch as part of fundraising. Remember...as we hear time and again, "It's not just about the robot"!.

Most likely, you won't be talking to technical people. So, if you make it out to be something like "hey, we can make our robot better, do more stuff, and have more features with these tools" that should be proper messaging. If they later ask why, then drown them in technicalities.

[jee7s]

Originally Posted by Kevin Selavko

Ask is here:https://docs.google.com/spreadsheet/...LbkowNWhBd EE

Ah, now that ask is different than what you had above. Is your text from your original post part of a larger proposal? What you are asking for in that google doc is most of a control system.

Remember, you're going to need a cRIO regardless of whether or not you get this money, you're going to need Jaguars regardless...so those aren't part of your ask IF you are only asking for CAN. Then, you're looking at about a $250 ask, which is much more manageable than $770 ask.

Also, if you're really wanting to get CAN going and you aren't using the serial port, then your ask drops to less than $50 (using the serial-to-CAN bridge in a black Jaguar). Then, do you really need more money?

[couvillion]

I would suggest you think about it from another angle. Your sponsor likely doesn't care how well you robot performs, much less the technical details of encoders. I would suggest:

Our team is seeking to expand it's technical expertise to incorporate a CAN(Controller Area Network) system into our robot. CAN is commonly used in cars for many uses including: locking doors, transmissions, cruise control, and airbags. On our robot it would allow for two way communication between the C-RIO and its motor controllers, in place of the one way communication we have now. This will open up new possibilities of robot actions and give our students real world experience with a current practical embedded networking technology. However to do this we will need to invest in new equipment and tools. ... list things desired, prices and schedule to the detail warranted ... Also include how you would recognize the donor.


Most encoders do generate square waves.

[Kevin Selavko]

We are wanting to update our whole control system, but I really haven't looked at the specs on the new jags to see if they are any better, is the only improvement the coating or are there any new functionalities? Although we still want a new C-rio for its size. Also we are try to get new sponsors for this, we currently only have about three.

[jee7s]

Originally Posted by Kevin Selavko

We are wanting to update our whole control system, but I really haven't looked at the specs on the new jags to see if they are any better, is the only improvement the coating or are there any new functionalities? Although we still want a new C-rio for its size.

If by "new jag" you mean the black jaguar, the two main differences are that you can remove the screws without creating metal shavings and the serial-to-CAN bridge. (If I remember correctly...NI/TI guys, feel free to correct me.)

If you are pitching for a complete control system, that's quite the different bargain than for CAN. (I was trying to make the point earlier that you probably don't need significantly more money than you currently spend to use CAN.)

I'd suggest you rethink what your pitch is, since your ask isn't just for CAN. You also might want to double check the 2013 KoP information and the Product Donation Voucher information. You should be able to bring down that $770 a bit more after you go through what you can get just for registering this year.

[Kevin Selavko]

Originally Posted by jee7s

If by "new jag" you mean the black jaguar

I mean the IFI ones, I guess I was getting carried away with the new parts bug I get every year about this time

[Kevin Selavko]

Here is the simplified parts list that we will need: https://docs.google.com/spreadsheet/...zI3e Xc#gid=0

[apalrd]

Just a bit of sponsorship advice:

-Start by saying who you are. Make it reasonably personable

-Then describe your team. What does your team do? They are a robotics team, yes? They compete in FRC, what is special about your team? What good things do they do? Awards are always nice to add.

-Now tell them what you would like for them, and what you do in return. Be clear about this. For engineering companies, make sure to talk about how you're teaching STEM and inspiring students to become engineers (something they NEED).

-Finish it nicely

Nowhere in that is anything technical. You are trying to convince them that your organization is worth donating money into, because you will spread their name via your publicity, and you will assist in inspiring students to become engineers (both are things they usually like). Don't ask them for money so you can spend a few hundred $$ on a CAN system, ask them for money so they can invest up to few thousand $$ on your team.

In general, never ask for specific items unless you are asking the company that produces/sells them to give them to you directly.



Now, for the technical evaluation:
-Encoders add no extra load to the cRio. The crio contains a PowerPC processor running at 400mhz and an FPGA running at significantly slower speed (not quite sure). The FPGA deals directly with all IO. The FPGA is already running 8x counter (single-line edge detection) and 4x encoder (dual-line edge detection), because FPGA code describes logic, and dosen't execute like a normal processor. The only additional load to the PowerPC would be whatever control loop you're running.
-Encoders are square waves. Two of them, A and B. You need only one to determine speed, both to determine direction.

-CAN is used to send messages. It has no real specific purpose defined other than getting a message of an ID and 8 data bytes from point A to everyone else, and validating that the data arrived safely (no retransmission). Many cars use CAN to send messages from distant ECU's, to save wiring costs. Sometimes windows are on the bus, sometimes they aren't.

-Standard cruise control actually involves the CAN bus less than you would expect - Wheel speed data comes from the ABS module via the bus, and the button states come from the bus, but that's about it. The engine does everything else on it's own, except possibly sending gear requests to a separate transmission (sometimes the PCM handles engine and trans, sometimes there's a separate TCM for the trans).

-Due to the fault-intolerant nature of airbags, they rarely use the CAN bus. To my knowledge, the safety ECU communicates directly with everything it requires (although some satellite sensors use a dedicated sensor bus).

[Kevin Selavko]

[quote=apalrd;1201399
-Standard cruise control actually involves the CAN bus less than you would expect - Wheel speed data comes from the ABS module via the bus, and the button states come from the bus, but that's about it. The engine does everything else on it's own, except possibly sending gear requests to a separate transmission (sometimes the PCM handles engine and trans, sometimes there's a separate TCM for the trans).

-Due to the fault-intolerant nature of airbags, they rarely use the CAN bus. To my knowledge, the safety ECU communicates directly with everything it requires (although some satellite sensors use a dedicated sensor bus).[/QUOTE]

I suppose Wikipedia was not the best source for information.

[Ether]

Originally Posted by Kevin Selavko

This is very useful, but it puts an extra strain on our main processor, the C-rio.

To be clear: when an encoder is connected to the cRIO, the high-speed raw signal from the encoder is processed in the cRIO's FPGA, not the cRIO's Power PC processor. The FPGA is designed to handle these high-frequency signals.

The processor asks the FPGA for a speed and/or position, and uses that to do closed loop control. The processor is plenty fast for that task, if the software architecture is designed correctly.