Introduction

The quadcopters (Micro Air Vehicles (MAV)) that I own have an organic ability to perform an automated landing, either on command or programmed as a waypoint.  Whilst the speed of descent is quite carefully controlled, the accuracy (i.e., the difference in position between the actual touchdown point and the desired touchdown point) can be (ahem) ‘variable’.

RTL

Current performance

 A quick set of measurements taken on the beach at low tide on a still day. Takeoff, fly around a bit and select RTL.

Aims

Platform agnostic
- Not dependent upon the functionality of any one specific set of flight control hardware, software or sensors.
Minimal effect on performance of quadcopter
- Low weight
- Low power demand
- Small space envelope
- No changes to autopilot / flight controller
Portable
- Low weight
- Low power demand
- Small space envelope
- Able to use available power sources
No impact on telemetry
- No changes to autopilot / flight controller
- No new messages
- Air-to-ground messaging unaffected
- Compatible with existing messages
Achievable
- Appreciable effect on accuracy
- No novel technologies
- No difficult mathematics [key requirement]
Usable.
- In bright sunlight
- In light to medium winds
- Gust-free conditions
Effective from 30m to ground level
Testable
Ability to record/replay information is very desirable.

Jumping Straight into Solution Space...

The camera of a Nintendo™ Wii-mote is able to identify and report the position of up to four ‘blobs’ that are sources of IR light within the frustrum of the camera sensor. This information is available at a rate of several hundred Hertz via an I2C interface. Within the Parallax Obex can be found objects for use of Wii-mote data. These were created by user Graham Stabler and his application of the data is shown in this video - clever stuff:

Progress

The first stage was the creation of a set of fixed-position IR markers: four IR LEDs:

IRLED

First Tests

The Wii-mote sensor was connectoted to a Parallax Propeller and the ‘Prop represented the data points on a VGA monitor.

Setup%20%281%29

The ‘system’ was expanded to include a R/C receiver and a servo.  The video below shows the servo responding to the movement of the IR LEDs across the field of view of the sensor.


Adding a second sensor ("stereo vision”) reduced the jitter.