Maggie/Electronics/Gyro
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Sensor
The gyroscopic sensor is a piezo gyroscope, TOKIN CG16-D0. This has been unsoldered in an helicopter model gyro: a Robbe G-400. I did not find the complete datasheet of this obsolete component, so i did a bit of reverse engineeing on the G400 to find out the pinning, and some other useful info.
If you want to use a heli gyro, it is better to use a larger one. These ones are older, but cheaper. And the sensor is easier to unsolder and to connect, most time !!
Unsoldering such a sensor is very delicate. It must not be overheated, and any pull force on the pins can make them unsolder from the internal PCB. I had to open mine to resolder the connections!
Filters
The actual schematic of the gyro card is a reproduction of a part of schematic that was on the G400. schematic
The gyro gives a reference voltage, that is approx. t Vcc/2
- R2/C8 make a basic LPF (Low Pass Filter)
- U1B is a LPF and amplifier (removal of excitation frequency)
- U1C is sallen-key filter, probably for flattening the response curve, and making a sharper LPF
- U1D is not used, but was used in the G400, HW as integrator
I did not calculate any cutoff frequency, i just took the same design that in the G400
Acceleration problems
I had the surprise that this gyro seems to respond lot to some parasitics accelerations. This was especially true as the gyro card was supposed to be on the side of the robot. The fact is that, while turning, maggie had a hard time to maintain banlance. This is due to the acceleration at the mounting point of the gyro while turning !!
This could be compensated out by measuring accelerations and substracting them with coefficients to the gyro value. But on Maggie i did not do it this way. I simply monted the gyro at the point of the robot with the less possible acceleration, between the two motors.
This has another advantage : the gyro is mounted between 3 walls, and so it is very well protected, as it is a fragile component.
Vibration
To avoid vibration to influence too much the gyro, the whole gyro card is mounted on a flexible foam. This was in the original package of the G400.
