Here is a new sensor which could improve stabilisation of our drones.It is purely a Geomagnetic Sensor however it can output rotation rate just like a gyro. It might even be possible to create an IMU type module using only this sensor and an accelerometer. That would be economical!
Features- Angular velocity detection and electronic compass functions in a single component made compatible by utilizing ALPS’s proprietary software.- Achieves high resistance to external interference with its proprietary shield structure."By processing data detected on three-directional geomagnetic axes using proprietary software developed by ALPS, the HSCD Series realizes an angular velocity detection function through triangulation, namely a gyro function. Combining these angular velocity detection and electronic compass functions in a single package reduces the size of the mounting area, as fewer components need to be installed "" resistance to external interference has been improved by building ALPS’ proprietary shield structure into its sensor element. As the number of functioning components increases in such products as mobile phones, and as progress continues in making circuit boards more compact, it is becoming easier for geomagnetic sensors to be affected by parts that generate magnetic fields, such as speakers. The proprietary shield, however, minimizes the effects of the magnetic fields emanating from other components."
For PNI Micromag, there is a trade-off between precision(gain) and update-rate. A good compromise seems to be with "Period select" set to 1024 which leads to 15 msec measurement time per axis => about 50 msec for a 3-axis measurement.
" there exists a method by which a 3-axis magnetometer and 3-axis accelerometer can be used to obtain full attitude that is not subject to centripetal acceleration errors."
That sounds promising. I wonder what the maximum update rate would be that you could get out of this sensor.
Combining it with an accelerometer and you have quite a small, cheap IMU module. The only remaining obstacle would be to minimise the effect of unwanted magnetic fields/ferromagnetic materials on the sensor. Perhaps a way to do this is by selecting motors and parts with a low interference potential and combine this with clever positioning of the sensor. Or use multiple sensors in locations around the airframe and average the result.
Most quadcopter designs use magnetometers very well for heading detection but is this because it is only interpolating into one axis(yaw)?
I have done some testing on an EZstar with a PNI Micromag 3-axis mag. When putting the sensor in the nose, the engine perturbation is hardly noticeable. It is not very good for crashes, but it works. For Quadcopters, i agree it is probably a different story.
@Michael Zaffuto: A mag can drift as much as 60° if improperly shielded. Or if it's surrounded by strong EM emitters, like motors or RF gear. It's a serious issue especially on small multicopters, where the EMI density goes up to insane levels.
From what I've seen of magnetometers, I dont think you'd get steady enough readings for it to replace a gyro if it's anywhere near a motor. Neat idea though...
Sweet. Google says 1,000 yen is $10.80 US. It looks like it is identical to a sensor they announced a year and a half ago, but with the addition of rate info. I can find lots of press, but no silicon for the predecessor. (The new one isn't out til March.) Is this vaporware? Hope not...
Planned Release
Sample price 1,000 yen (including tax)
Planned monthly production 1 million units (March 2010)
Development Mechatronics, Materials & Process (MMP) Division,
Nagaoka Plant (Nagaoka City, Niigata Prefecture)
Production Mechatronics, Materials & Process (MMP) Division,
Nagaoka Plant (Nagaoka City, Niigata Prefecture)
Specifications
Product name HSCD Series
Dimensions (W × D × H) 2.5mm × 2.5mm × 0.7mm
Magnetic field measurement range ±0.6mT
Output resolution 0.5μT / LSB
Operating temperature -20°C to +85°C
Supply voltage (analog) 2.5V type
Supply voltage (digital) 1.8V type
Average current consumption (when active) Max. 200 μA
Average current consumption (when on standby) Max. 5 μA
Comments
That sounds promising. I wonder what the maximum update rate would be that you could get out of this sensor.
Combining it with an accelerometer and you have quite a small, cheap IMU module. The only remaining obstacle would be to minimise the effect of unwanted magnetic fields/ferromagnetic materials on the sensor. Perhaps a way to do this is by selecting motors and parts with a low interference potential and combine this with clever positioning of the sensor. Or use multiple sensors in locations around the airframe and average the result.
Most quadcopter designs use magnetometers very well for heading detection but is this because it is only interpolating into one axis(yaw)?
Planned Release
Sample price 1,000 yen (including tax)
Planned monthly production 1 million units (March 2010)
Development Mechatronics, Materials & Process (MMP) Division,
Nagaoka Plant (Nagaoka City, Niigata Prefecture)
Production Mechatronics, Materials & Process (MMP) Division,
Nagaoka Plant (Nagaoka City, Niigata Prefecture)
Specifications
Product name HSCD Series
Dimensions (W × D × H) 2.5mm × 2.5mm × 0.7mm
Magnetic field measurement range ±0.6mT
Output resolution 0.5μT / LSB
Operating temperature -20°C to +85°C
Supply voltage (analog) 2.5V type
Supply voltage (digital) 1.8V type
Average current consumption (when active) Max. 200 μA
Average current consumption (when on standby) Max. 5 μA