thebalancefilter-外文文獻(xiàn)-資料下載頁
2025-05-11 12:33本頁面
【導(dǎo)讀】X-axisreads0g,Y-axisreads-1g.Probablynot:. Reads“zero”whenstationary.signed*int-typevariable(orconstant).x_acc=(float)(x_acc_ADC–x_acc_offset)*x_acc_scale;gyro=(float)(gyro_ADC–gyro_offset)*gyro_scale;horizontally).Thisworkswell(within5%)uptoθ=±π/6=±30º.x_acc=(float)(x_acc_ADC–x_acc_offset)*x_acc_scale;
【正文】 f a second, the gyroscope integration takes precedence and the noisy horizontal accelerations are filtered out. For time periods longer than half a second, the accelerometer average is given more weighting than the gyroscope, which may have drifted by this point. sec 49 . 002 . 0sec 01 . 0 98 . 01??????adt a?A Closer Look at the Angle Complementary FilterFor the most part, designing the filter usually goes the other way. First, you pick a time constant and then use that to calculate filter coefficients. Picking the time constant is the place where you can tweak the response. If your gyroscope drifts on average 2186。 per second (probably a worstcase estimate), you probably want a time constant less than one second so that you can be guaranteed never to have drifted more than a couple degrees in either direction. But the lower the time constant, the more horizontal acceleration noise will be allowed to pass through. Like many other control situations, there is a tradeoff and the only way to really tweak it is to experiment.Remember that the sample rate is very important to choosing the right coefficients. If you change your program, adding a lot more floating point calculations, and your sample rate goes down by a factor of two, your time constant will go up by a factor of two unless you recalculate your filter terms.As an example, consider using the msec radio update as your control loop (generally a slow idea, but it does work). If you want a time constant of sec, the filter term would be:So, angle = ()*(angle + gyro*) + ()*(x_acc)。.The second filter coefficient, , is just (1 ).966 . 0sec 0262 . 0 sec 75 . 0sec 75 . 0?????dta??A Closer Look at the Angle Complementary FilterIt’s also worthwhile to think about what happens to the gyroscope bias in this filter. It definitely doesn’t cause the drifting problem, but it can still effect the angle calculation. Say, for example, we mistakenly chose the wrong offset and our gyroscope reports a rate of 5 186。/sec rotation when it is stationary. It can be proven mathematically (I won’t here) that the effect of this on the angle estimate is just the offset rate multiplied by the time constant. So if we have a sec time constant, this will give a constant angle offset of .Besides the fact that this is probably a worstcase scenario (the gyro should never be that far offset), a constant angle offset is much easier to deal with than a drifting angle offset. You could, for example, just rotate the accelerometer in the opposite direction to acmodate for it.
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