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1  Using Arduino / Sensors / Pan-Tilt-Roll Compensator - Help on IMU! on: March 09, 2012, 09:13:52 pm
Hi

My current project involves using an 6DOF IMU (http://www.sparkfun.com/products/10121) to compensate for movements in the pan, tilt and roll axis. My project comprises of 2 platforms, top and bottom platform. The top platform is stationary, while the bottom platform is allowed to move in the pan, tilt and roll axis.

Initially the IMU is located on the bottom platform, and it moves together with the bottom platform as it rotates around the pan axis. Thus the axis of the IMU is always aligned with the bottom platform, and I can fixed use the x-axis of the IMU for tilt compensation and y-axis for roll compensation. I have no problems with the tilt and roll compensation, except the pan compensation. When the IMU detects a movement(noise) in the pan axis, it attempts to compensate the noise by moving in the opposite direction, however at this point the IMU detects the compensation as a movement, and will try to "compensate the initial compensation". Thus it rocks back and forth continuously on the pan axis.

Thus, I decided to move the IMU to the top platform, which is stationary throughout. At this point, the pan axis compensation has no problem as the IMU does not move when the bottom platform is moving. However, there is now a problem with the tilt and roll axis. Since the IMU on the top patform does not move when the bottom platform moves, its axis is never aligned with the bottom platform. For example, at one instance I'll use the x-axis of the IMU to compensate for tilt, but when the bottom platform moves 90 degrees, I'll have to use the y-axis of the IMU to compensate for the tilt. Similar for roll as well.

Thus, as a summary my problems are as follows:
1) Pan axis compensation when my IMU is located on the movable bottom platform.
2) TIlt/Roll axis compensation when my IMU is located on the fixed top platform.

Any ideas on how to solve either of the 2 problems? Thank you so much!
2  Using Arduino / Project Guidance / Pan-Tilt-Roll Compensator - Help! on: March 09, 2012, 01:21:09 pm
Hi

My current project involves using an 6DOF IMU (http://www.sparkfun.com/products/10121) to compensate for movements in the pan, tilt and roll axis. My project comprises of 2 platforms, top and bottom platform. The top platform is stationary, while the bottom platform is allowed to move in the pan, tilt and roll axis.

Initially the IMU is located on the bottom platform, and it moves together with the bottom platform as it rotates around the pan axis. Thus the axis of the IMU is always aligned with the bottom platform, and I can fixed use the x-axis of the IMU for tilt compensation and y-axis for roll compensation. I have no problems with the tilt and roll compensation, except the pan compensation. When the IMU detects a movement(noise) in the pan axis, it attempts to compensate the noise by moving in the opposite direction, however at this point the IMU detects the compensation as a movement, and will try to "compensate the initial compensation". Thus it rocks back and forth continuously on the pan axis.

Thus, I decided to move the IMU to the top platform, which is stationary throughout. At this point, the pan axis compensation has no problem as the IMU does not move when the bottom platform is moving. However, there is now a problem with the tilt and roll axis. Since the IMU on the top patform does not move when the bottom platform moves, its axis is never aligned with the bottom platform. For example, at one instance I'll use the x-axis of the IMU to compensate for tilt, but when the bottom platform moves 90 degrees, I'll have to use the y-axis of the IMU to compensate for the tilt. Similar for roll as well.

Thus, as a summary my problems are as follows:
1) Pan axis compensation when my IMU is located on the movable bottom platform.
2) TIlt/Roll axis compensation when my IMU is located on the fixed top platform.

Any ideas on how to solve either of the 2 problems? Thank you so much!
3  Using Arduino / Sensors / Problems with angle estimation using ADXL345 on: March 07, 2012, 05:02:25 am
Hi

I'm currently using the ADXL345 3-axis accelerometer (part of the 6DOF IMU, incl ITG-3200 Gyro) to sense the pitch and roll angles.

Syntax:

acc_angle[0] = atan2(acc_g[0],acc_g[2]) * 180 / PI;
acc_angle[1] = atan2(acc_g[1],acc_g[2]) * 180 / PI;

where acc_g[0] = x-axis gravitational reading (g)
         acc_g[1] = y-axis gravitational reading (g)
         acc_g[2] = z-axis gravitational reading (g)

The above code makes use of the gravitational readings (g) of the accelerometer to measure the angular tilt. It works fine, however when the z-axis of the accelerometer goes parallel with the ground (ie. acc_g[2]=0), the readings goes bonkers. I figured it's because of the trigo mathematics using atan2 then causes it when acc_g[2]=0.

Any ideas on how to solve this problem?
4  Using Arduino / Networking, Protocols, and Devices / Re: Difference between USB Modem and USB Dongle on: October 27, 2011, 12:01:00 pm
Well i did see that the bluesmirf modem is a class 1 BT able to communicate at 100 metre range. But i wonder if that's really true? The environment which I am communicating is kinda open, from the ground to the air. Has anyone achieved 100m with bluesmirf or any bluetooth modems before?
5  Using Arduino / Networking, Protocols, and Devices / Re: Difference between USB Modem and USB Dongle on: October 27, 2011, 07:23:36 am
Thanks for the reply.

Well my plan was to save some $$$ by using cheap USB Dongles, as compared to buying a Bluesmirf Modem or Xbees (incl 2 Xbee radios, Xbee Shield, Xbee Explorer Dongle).

Are there currently any libraries already written that allows USB dongles to be used on the USB Host Shield? I did manage to find one on http://www.circuitsathome.com/mcu/bluetooth-code-for-arduino-usb-host, but that seems still like a work in progress.

P.S. I'm trying to achieve a range of about 100 metres as well.
6  Using Arduino / Networking, Protocols, and Devices / Difference between USB Modem and USB Dongle on: October 26, 2011, 03:33:46 am
Hi

Was just trying to implement bluetooth to my little project. Was reading http://www.arduino.cc/playground/Learning/Tutorial01, and realise the tutorial uses a Bluesmirf bluetooth modem on the arduino side and a bluetooth dongle on the computer side. I have this question in mind which I can't really find the answers around: What is the difference between the modem and the dongle? Can I simply replace the Bluesmirf modem with a USB Host Shield + USB Dongle on the arduino?

And has anyone tried the actual range of class 1 Bluetooth (despite them being stated to be able to reach 100m)?

Many thanks!
7  Using Arduino / Project Guidance / Interfacing Laptop, Playstation 3 controller, Arduino (bluetooth in the future) on: October 25, 2011, 04:56:48 am
Hi!

I was searching on the net and have found numerous articles on how to interface a playstation controller DIRECTLY with an arduino. However, I don't really want to do that. Instead, I would like to connect both arduino and the playstation controller to my laptop, and ultimately using the playstation controller to control the servos on my arduino. Thus, the computer will receive the commands from the playstation controller and send it to the arduino via USB (the same one used to upload sketches). I am using a sixaxis playstation 3 controller.

In the future, I would hope to replace the USB cable with a bluetooth module (one on the laptop, the other to the USB Host shield on the arduino).

Right now, can anyhow advise me on how to do it via the USB (wired) method first?

Thanks very much!!
8  Using Arduino / Project Guidance / Re: Wireless Aerial Rig on: September 22, 2011, 12:07:38 pm
Just realised it's probably a servo issue since different servos have different angle/second.

One more question, i am trying to control the servos via a playstation 3 controller that is connected to a laptop. Thus, the laptop will take the inputs from the ps3 controller and send them wirelessly to the arduino to control the servos. Is that possible?
9  Using Arduino / Project Guidance / Re: Wireless Aerial Rig on: September 21, 2011, 06:15:37 am
Thanks! I'll check the webbies out. smiley

Also if I were to require the servos to react fast (for eg. to adjust the camera so that it goes back aiming at the target asap), is this a software (C code) or a hardware (microcontroller/servo) issue?
10  Using Arduino / Project Guidance / Wireless Aerial Rig on: September 21, 2011, 02:35:15 am
Hi!

I am trying to send a rig up to the air via a kite (similar to Kite Aerial Photography), bout 60m - 100m. It will be equipped with a wireless camera to send back images/video back. The rig will have 2 modes: manual and auto targeting. The manual mode is whereby the servos will be controlled using the signals from a PS3 controller, while the auto mode will be via the OpenCV platform on my laptop to send signals to the rig to control the servos. All of these are achieved wirelessly.

1) Are all these too much for the arduino to handle? I assume not since the arduino is only handling the wireless signals from the PS3 controller/OpenCV to control the servos?
2) Are there any cheap wireless cameras that has a decent resolution/fps?
3) What will be a suitable way to transmit wirelessly? Wifi/Zigbee? I'm ruling out Bluetooth cos I doubt even a class 1 will be able to transmit the distance required.
11  Using Arduino / Project Guidance / Re: Drivers for USB devices on: September 14, 2011, 02:45:36 am
I'm thinking of attaching a USB dongle and a webcam to the arduino. Correct me if im wrong, but does drivers = libraries in this case?

And also you mentioned in your sig that its not feasible to connect a camera to the arduino and send pictures wirelessly. Is the reason due to storage space of the Atmega chip? Do you have any recommendations for a microprocessor which is capable of controlling servos and sending pictures wirelessly?
12  Using Arduino / Project Guidance / Re: Drivers for USB devices on: September 14, 2011, 02:25:24 am
Um, that doesn't really help.
13  Using Arduino / Project Guidance / Re: Drivers for USB devices on: September 14, 2011, 02:12:34 am
If the drivers for a specific device is already present, how do I upload into the arduino to ensure that the device plugged in will work?
14  Using Arduino / Project Guidance / Drivers for USB devices on: September 13, 2011, 11:15:03 am
Hi.

When we plug in USB devices on our computers, the computers automatically searches and installs the appropriate drivers for the devices to enable you to use them. For the arduino board, if we plug in devices (eg. Bluetooth dongles, webcams) via the USB host shield, how are we going to upload the drivers into the arduino board? Are we suppose to write the drivers ourselves?

Thanks.
15  Using Arduino / Project Guidance / Bluetooth Controlled Camera Rig on: August 30, 2011, 11:30:24 pm
Hi. I got this idea off Kite Aerial Photography (KAP), but instead of using an actual digital camera, I was thinking of mounting a USB webcam and have it feed back real time video feed using bluetooth to my laptop. There will also be 2 servos for the pan/tilt of the camera rig, which I'm planning to control by hacking a PS3 SixAxis controller to send signals via bluetooth to the arduino as well. I am planning to use Arduino UNO as a platform to perform these functions. However, I've read that Arduino does not have the capabilities to project live video feed.

- Is there any way to modify a Arduino to achieve live video feed?
- Is it possible for Arduino to act as a host to multiple USB devices (webcam + bluetooth dongle)? Maybe connecting several USB shields to 1 board?
- Is it possible to achieve full duplex communication (transmitting live video feed + receiving PS3 controller signals at the same time) through 1 bluetooth dongle on the Arduino?
- Is there a way I can trigger the webcam through software/hardware to capture an image?

Thanks.
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