Indoor localization

Hexapod Robots

Indoor localization

Postby pem » Sat Feb 20, 2010 6:23 pm

My time with the MSR-H01 has been very limited the last 6-8 months, but I hope to be able to spend more time in the near future.

Navigation is one of my main interests, and recently I stumbled upon the Stargazer system by Hagisonic (http://www.robotshop.ca/hagisonic-stargazer-localization-system.html). The system is able to provide indoor localization information with a 2 cm accuracy.

Unfortunately it is quite expensive (approx. $900), but I'm very tempted. Should anybody have any experiences, I would be happy to learn about them. Also if any similar systems are available?

Stargazer requires 5V and 300mA, and according to the p.Brain-ds24 specs, CN17 pin 9 is only able to deliver 200 mA. What would be necessary in order to get 300 mA out of the batteries?

Even if the power problem is solved, the next obstacle would be to communicate with the Stargazer. I would prefer to channel the communication through the Bluetooth link, much in the same way that I2C devices do. Stargazer uses TTL serial communication, and I guess it should be possible to use UART2 for this, since UART1 is reserved for locomotion and configuration communication through Bluetooth.

Would it be possible to connect UART2 with the Stargazer and (presumably with a firmware update) to communicate with it through Bluetooth?
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Re: Indoor localization

Postby marcel.kanter » Sun Feb 21, 2010 6:20 pm

First thing i thought when i've read the product specs: the key thing in this is the software reading the code printed onto the stickers you have to glue onto the ceiling. if you already have an cam on your robot this may can be integrated into the existing software.
Then the next thought: How does accuracy depend of tilt of the body and would i stick these stickers onto my ceiling? What is when the stickers cannot be sseen by the cam (robot moves under an table or so)?

Btw. The 300mA @ 5v is the power consumption. If you drive it from a 5v source it will draw 300mA. You just need an regulator to use this thing, driving it from an µC pin will burn the µC (or the pin only)
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Re: Indoor localization

Postby pem » Mon Feb 22, 2010 7:26 pm

Thank you for your reply.

It is correct that a camera could also detect the stickers in the ceiling, but I'll then have to do the localization calculation myself, which I dont think is an easy task. With Stargazer, the position is returned with a 2cm accuracy. But of course, the hex need to be leveled when the sticker is read. Luckily there is a balanced mode, which hopefully will help.

Somehow the power problem must be dealt with, but my biggest concern is to handle the serial communication with the Stargazer. The goal is to route the commands and responses through the Parani Bluetooth dongle connected to UART1. This means, that UART2 on the p.Brain-ds24 must be connected to the Stargazer. In the p.Brain-ds24 User Guide (CN17), it says
U2TX Pin 3 can drive the RS-232 transceiver and other external TTL uarts simultaneously.
What exactly this means I dont know, but as previously mentioned, perhaps an updated firmware would enable this?
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Re: Indoor localization

Postby Matt Denton » Tue Feb 23, 2010 2:03 pm

pem wrote: U2TX Pin 3 can drive the RS-232 transceiver and other external TTL uarts simultaneously.

What exactly this means I dont know, but as previously mentioned, perhaps an updated firmware would enable this?


Ok, so on the p.Brain-ds24 there are two UARTS, both of which are TTL, one of which has an RS232 transceiver attached to it UART2.

The RS232 transceiver is tied to UART pins TX and RX, TX is an output pin, RX is an input pin. You can only drive the RX input pin from one TTL source, which is currently the RS232 transceiver, however, the TX output pin can drive multiple devices, currently tied to the TX pin on the RS232 transceiver, this pin could also be tied to say the TX pin on an RS485 transmitter, so you would have the transmitted TTL data being sent to two level converters. Having said this, you can also disable the RS232 transceiver, and thus drive the RX input of UART2 with your own TTL source.

This does of course assume that you are writing your own code for the ds24?
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Re: Indoor localization

Postby pem » Wed Feb 24, 2010 9:16 pm

Obviously a lot of careful thought has gone into the design, which opens for many possibilities. But as you mention, to utilize this, you'll have to do your own programming of the ds24, which is out of my league.

Regarding the Stargazer, the best would be, if it could act as an I2C slave instead of the provided serial interface. But it is so expensive anyway, that I'm not going to buy it right away.

Instead I have bought a CMPS03 compass and an SRF08 distance sensor, and the plan is that it will keep me busy for a while.
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Re: Indoor localization

Postby arnoldarever » Fri Mar 19, 2010 5:42 am

Talking about indoor systems I think the following stated features make it all the more necessary and important.....
- Analyses the image obtained when an infrared ray is reflected from a passive landmark with characteristic ID.
- Consists an IR Projector and a CMOS camera for turning the reflected infrared rays into image.
- High resolution and high speed localization of position and heading angle.
- Low cost passive landmarks are attached to the ceiling. No battery or energy supply for landmark.
- Easy expansion for larger area by adding more landmarks to the ceiling.
- Not necessary to synchronize or communicate between a robot and a landmark.
- Distinguish each room by using different IDs.
- Automatic measurement and automatic calibration of distance between landmarks and ceiling height.
- Negligible cost for extension of landmarks.
- Negligibly affected by environmental lights and sunshine.
- Worlds best in resolution, convenience and cost.
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