Active control of payload direction

By changing the set-point of the payload stabilizer the direction of the payload can be actively controlled. This could be useful for panning on-board cameras etc.
In this experiment set point was commanded to sweep between +90 and - 90 degrees with the following profile:

Red=yaw(roll), green=command, 20mS/div.

In the video the payload section vibrates a bit. This is a result of the loop-filter not being properly re-tuned after the motor driver was changed.

More payload stabilizer

After playing a bit with the stabilizer i got annoyed with the motor controller I had used. It was the circuit board from an old analog servo. It regulated the motor with 50Hz PWM, had a limited output range and an annoying dead-band. All this led to noisy regulation and oscillation caused by the dead-band.

1st. set-up

The micro controller has the capability to output the motor command as a 8kHz PWM- and a direction signal. Using these signals to drive a simple MOSFET H-bridge i was able to get a much smoother and quieter regulation.

2nd. Driver.

Payload roll-stabilizer for spinning rocket

Rather than trying to roll stabilize a rocket it is sometimes desirable to let the rocket rotate around its length axis and then counter-rotate the payload section.
This device is a quick'n dirty prototype to explore this.

New IMU

I am now using the ArduIMU V3 for my flying/guidance experiments. The AHRS firmware for this device has not yet been released but I have managed to get some preliminary firmware together.
The performance of this device seem promising but I have encountered some electrical problems. It is extremely sensitive to noise when powered on external 5V power supply. It can not be powered by the same 5V bus as e.g. servos. It does however have its own on-board voltage regulator that works well when supplied directly from a higher voltage.
There will be much more about this IMU on this blog.

Pitch and roll tuning end in pain...

After the initial success i went on to tuning the PID controllers for pitch and yaw. After 20 fairly sucessfull minutes i accidently hit the throttle while holding on to the elastic ribbon and WHACK ... the rotor cut deeply into two of my fingers sending blood everywhere.
Bad times. Experiment now suspended until i have all my digits back...

Moments of robot tuning

After completeing the RCTP hardware the flight controller needed to be adjusted for stability. I am using a simple PID controller for now.
Starting with YAW I suspended the RCTP from an elastic ribbon so that it was able to yaw freely.

Throttle and YAW tuning parameters was supplied from the RC-controller via wirerless. Measurement data was received via. cable.

I chose some conservative initial settings for the PID controller (Blue: Integral=0, Green: Proportional=30, Yellow: Derivative=35-ish). And commanded (via the RC controller) a yaw angle of 0.
When starting the rotor the system was oscillating around the YAW axis as suspected. Increasing the D-term (again via. a slider on the RC controller) cancelled the oscillation. A push on the RCTP confirmed that the regulation loop worked.

After some testing it was confirmed that the YAW angle of the RCTP was not zero (zero angle is currently the compass angle in which the flight contrroller is power up). Increasing the I-term fixed that problem.
Yaw is now stable regardless of the rotor speed.

Gimballed high pressure nozzle

IMAG0441, a photo by geekphysical on Flickr.

I have made this nozzle for a future extreme high pressure guided water rocket.

Guidance system

IMAG0434, a photo by geekphysical on Flickr.

The brain of the rocket