Smoothing data from a sensor

Question

I have a 3D sensor which measures v(x,y,z) data. I\'m only using the x and y data. Smoothing only x and y would be enough.

If I use a log to show the data, it shows

Answer 1

Well there are many ways to smooth sensor data depends what kind of sensor it is and what analogy will suit. I have used these algorithms in my projects:

1. High Pass Filter[HPF] and Low Pass Filters[LPF]- as expressed in the selected answer.
2. Moving Average Algorithm -MAA
3. Gaely's Algorithmm[Better version for MAA]
4. Fast Fourier Transform -FFT

Code:

HPF-High Pass Filter

private float[] highPass(float x, float y, float z) {
    float[] filteredValues = new float[3];
    gravity[0] = ALPHA * gravity[0] + (1 – ALPHA) * x;
    gravity[1] = ALPHA * gravity[1] + (1 – ALPHA) * y;
    gravity[2] = ALPHA * gravity[2] + (1 – ALPHA) * z;
    filteredValues[0] = x – gravity[0];
    filteredValues[1] = y – gravity[1];
    filteredValues[2] = z – gravity[2];
    return filteredValues;   
    }

LPF-Low Pass Filter

private float[] lowPass(float x, float y, float z) {
    float[] filteredValues = new float[3];
    filteredValues[0] = x * a + filteredValues[0] * (1.0f – a);
    filteredValues[1] = y * a + filteredValues[1] * (1.0f – a);
    filteredValues[2] = z * a + filteredValues[2] * (1.0f – a);
    return filteredValues;
    }

MAA-Moving Average

     private final int SMOOTH_FACTOR_MAA = 2;//increase for better results   but hits cpu bad

     public ArrayList processWithMovingAverageGravity(ArrayList list, ArrayList gList) {
            int listSize = list.size();//input list
            int iterations = listSize / SMOOTH_FACTOR_MAA;
            if (!AppUtility.isNullOrEmpty(gList)) {
                gList.clear();
            }
            for (int i = 0, node = 0; i < iterations; i++) {
                float num = 0;
                for (int k = node; k < node + SMOOTH_FACTOR_MAA; k++) {
                    num = num + list.get(k);
                }
                node = node + SMOOTH_FACTOR_MAA;
                num = num / SMOOTH_FACTOR_MAA;
                gList.add(num);//out put list
            }
            return gList;
        }