你的方法存在至少一个问题。
我猜测你将磁力计对应的三维向量与平均低通滤波器相结合以平滑数据。虽然这种方法对于传感器值没有不连续性变化的情况非常有效,例如从加速度计中获取的原始数据,但它并不能直接很好地处理从磁力计中获取的角度变量。为什么呢?
因为这些角度变量(方位角、俯仰角、翻转角)有一个上限和一个下限,这意味着任何高于180度的值,比如181度,都会环绕到181-360=-179度,而任何低于-180度的变量都会在另一个方向上环绕。所以当其中一个角度变量接近这些阈值(180或-180)时,该变量 tend to oscillate to values close to those 2 extremes。当你盲目地将低通滤波器应用于这些值时,你要么得到从180度向-180度平滑减少的结果,要么得到从-180度向180度平滑增加的结果。无论哪种情况,结果看起来都很像你上面的视频......只要将平均缓冲区直接应用于getOrientation(...)的原始角度数据上,这个问题就会存在(不仅在手机直立的情况下存在,也应该存在于存在方位角环绕的情况下......也许你还可以测试这些bug......)。
你说你用缓冲区大小为1来测试了这个方法。理论上,如果根本没有平均,问题就不应该存在,尽管在我过去看到的某些循环缓冲区实现中,这可能意味着仍然至少有一个过去的值进行平均,而不是完全没有平均。如果是这种情况,我们已经找到了错误的根源。
不幸的是,如果要坚持使用标准平均滤波器,就没有太多优雅的解决方案。在这种情况下,我通常会切换到另一种类型的低通滤波器,它不需要任何深度缓存来操作:一个简单的IIR滤波器(一阶):
diff = x[n] - y[n-1]
y[n] - y[n-1] = alpha * (x[n] - y[n-1]) = alpha * diff
...其中y是过滤后的角度,x是原始角度,alpha<1类似于时间常数,因为alpha=1对应于没有滤波的情况,随着alpha接近零,低通滤波器的截止频率降低。一个敏锐的眼睛可能已经注意到这对应于一个简单的比例控制器。
这样的滤波器允许补偿角度值的环绕,因为我们可以添加或减去360到diff,以确保abs(diff)<=180,这反过来确保了过滤后的角度值始终以最佳方向增加/减少以达到其“设定点”。
一个例子是一个周期性调用的函数调用,该函数为给定的原始角度值x计算过滤后的角度值y,可能是这
private float restrictAngle(float tmpAngle){
while(tmpAngle>=180) tmpAngle-=360;
while(tmpAngle<-180) tmpAngle+=360;
return tmpAngle;
}
private float calculateFilteredAngle(float x, float y){
final float alpha = 0.1f;
float diff = x-y;
diff = restrictAngle(diff);
y += alpha*diff;
y = restrictAngle(y);
return y;
}
接下来可以定期使用类似以下代码(以getOrientation(...)
函数返回的方位角为例)调用函数calculateFilteredAngle(float x, float y)
filteredAzimuth = calculateFilteredAngle(azimuth, filteredAzimuth);
使用该方法,过滤器不会像OP提到的平均过滤器那样出现问题。
由于无法加载OP上传的.apk文件,我决定实现自己的测试项目以查看更正是否有效。以下是完整代码(未使用XML作为主要布局,因此没有包含它)。将其复制到测试项目中以查看是否在特定设备上正常运行(在HTC Desire w/ Android v. 2.1上测试功能):
文件1:Compass3DActivity.java:
package com.epichorns.compass3D;
import android.app.Activity;
import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.TextView;
public class Compass3DActivity extends Activity {
TextView mTextView_azimuth;
TextView mTextView_pitch;
TextView mTextView_roll;
TextView mTextView_filtered_azimuth;
TextView mTextView_filtered_pitch;
TextView mTextView_filtered_roll;
float mAngle0_azimuth=0;
float mAngle1_pitch=0;
float mAngle2_roll=0;
float mAngle0_filtered_azimuth=0;
float mAngle1_filtered_pitch=0;
float mAngle2_filtered_roll=0;
private Compass3DView mCompassView;
private SensorManager sensorManager;
float[] mGravity = null;
float[] mGeomagnetic = null;
float Rmat[] = new float[9];
float Imat[] = new float[9];
float orientation[] = new float[3];
SensorEventListener mAccelerometerListener = new SensorEventListener(){
public void onAccuracyChanged(Sensor sensor, int accuracy) {}
public void onSensorChanged(SensorEvent event) {
if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER){
mGravity = event.values.clone();
processSensorData();
}
}
};
SensorEventListener mMagnetometerListener = new SensorEventListener(){
public void onAccuracyChanged(Sensor sensor, int accuracy) {}
public void onSensorChanged(SensorEvent event) {
if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD){
mGeomagnetic = event.values.clone();
processSensorData();
update();
}
}
};
private float restrictAngle(float tmpAngle){
while(tmpAngle>=180) tmpAngle-=360;
while(tmpAngle<-180) tmpAngle+=360;
return tmpAngle;
}
private float calculateFilteredAngle(float x, float y){
final float alpha = 0.3f;
float diff = x-y;
diff = restrictAngle(diff);
y += alpha*diff;
y = restrictAngle(y);
return y;
}
public void processSensorData(){
if (mGravity != null && mGeomagnetic != null) {
boolean success = SensorManager.getRotationMatrix(Rmat, Imat, mGravity, mGeomagnetic);
if (success) {
SensorManager.getOrientation(Rmat, orientation);
mAngle0_azimuth = (float)Math.toDegrees((double)orientation[0]);
mAngle1_pitch = (float)Math.toDegrees((double)orientation[1]);
mAngle2_roll = -(float)Math.toDegrees((double)orientation[2]);
mAngle0_filtered_azimuth = calculateFilteredAngle(mAngle0_azimuth, mAngle0_filtered_azimuth);
mAngle1_filtered_pitch = calculateFilteredAngle(mAngle1_pitch, mAngle1_filtered_pitch);
mAngle2_filtered_roll = calculateFilteredAngle(mAngle2_roll, mAngle2_filtered_roll);
}
mGravity=null;
mGeomagnetic=null;
}
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
LinearLayout ll = new LinearLayout(this);
LinearLayout.LayoutParams llParams = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.FILL_PARENT, LinearLayout.LayoutParams.FILL_PARENT);
ll.setLayoutParams(llParams);
ll.setOrientation(LinearLayout.VERTICAL);
ViewGroup.LayoutParams txtParams = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
mTextView_azimuth = new TextView(this);
mTextView_azimuth.setLayoutParams(txtParams);
mTextView_pitch = new TextView(this);
mTextView_pitch.setLayoutParams(txtParams);
mTextView_roll = new TextView(this);
mTextView_roll.setLayoutParams(txtParams);
mTextView_filtered_azimuth = new TextView(this);
mTextView_filtered_azimuth.setLayoutParams(txtParams);
mTextView_filtered_pitch = new TextView(this);
mTextView_filtered_pitch.setLayoutParams(txtParams);
mTextView_filtered_roll = new TextView(this);
mTextView_filtered_roll.setLayoutParams(txtParams);
mCompassView = new Compass3DView(this);
ViewGroup.LayoutParams compassParams = new ViewGroup.LayoutParams(200,200);
mCompassView.setLayoutParams(compassParams);
ll.addView(mCompassView);
ll.addView(mTextView_azimuth);
ll.addView(mTextView_pitch);
ll.addView(mTextView_roll);
ll.addView(mTextView_filtered_azimuth);
ll.addView(mTextView_filtered_pitch);
ll.addView(mTextView_filtered_roll);
setContentView(ll);
sensorManager = (SensorManager) this.getSystemService(Context.SENSOR_SERVICE);
sensorManager.registerListener(mAccelerometerListener, sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER), SensorManager.SENSOR_DELAY_UI);
sensorManager.registerListener(mMagnetometerListener, sensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD), SensorManager.SENSOR_DELAY_UI);
update();
}
@Override
public void onDestroy(){
super.onDestroy();
sensorManager.unregisterListener(mAccelerometerListener);
sensorManager.unregisterListener(mMagnetometerListener);
}
private void update(){
mCompassView.changeAngles(mAngle1_filtered_pitch, mAngle2_filtered_roll, mAngle0_filtered_azimuth);
mTextView_azimuth.setText("Azimuth: "+String.valueOf(mAngle0_azimuth));
mTextView_pitch.setText("Pitch: "+String.valueOf(mAngle1_pitch));
mTextView_roll.setText("Roll: "+String.valueOf(mAngle2_roll));
mTextView_filtered_azimuth.setText("Azimuth: "+String.valueOf(mAngle0_filtered_azimuth));
mTextView_filtered_pitch.setText("Pitch: "+String.valueOf(mAngle1_filtered_pitch));
mTextView_filtered_roll.setText("Roll: "+String.valueOf(mAngle2_filtered_roll));
}
}
文件2:Compass3DView.java:
package com.epichorns.compass3D;
import android.content.Context;
import android.opengl.GLSurfaceView;
public class Compass3DView extends GLSurfaceView {
private Compass3DRenderer mRenderer;
public Compass3DView(Context context) {
super(context);
mRenderer = new Compass3DRenderer(context);
setRenderer(mRenderer);
}
public void changeAngles(float angle0, float angle1, float angle2){
mRenderer.setAngleX(angle0);
mRenderer.setAngleY(angle1);
mRenderer.setAngleZ(angle2);
}
}
文件3:Compass3DRenderer.java:
package com.epichorns.compass3D;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
import java.nio.ShortBuffer;
import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.opengles.GL10;
import android.content.Context;
import android.opengl.GLSurfaceView;
public class Compass3DRenderer implements GLSurfaceView.Renderer {
Context mContext;
ShortBuffer _indexBuffer;
FloatBuffer _vertexBuffer0;
FloatBuffer _vertexBuffer1;
FloatBuffer _vertexBuffer2;
FloatBuffer _vertexBuffer3;
FloatBuffer _vertexBuffer4;
FloatBuffer _vertexBuffer5;
int _numVertices = 3;
FloatBuffer _textureBuffer0123;
float _light0Position[] = new float[]{10.0f, 10.0f, 10.0f, 0.0f};
float _light0Ambient[] = new float[]{0.05f, 0.05f, 0.05f, 1.0f};
float _light0Diffuse[] = new float[]{0.5f, 0.5f, 0.5f, 1.0f};
float _light0Specular[] = new float[]{0.7f, 0.7f, 0.7f, 1.0f};
float _matAmbient[] = new float[] { 0.6f, 0.6f, 0.6f, 1.0f };
float _matDiffuse[] = new float[] { 0.6f, 0.6f, 0.6f, 1.0f };
private float _angleX=0f;
private float _angleY=0f;
private float _angleZ=0f;
Compass3DRenderer(Context context){
super();
mContext = context;
}
public void setAngleX(float angle) {
_angleX = angle;
}
public void setAngleY(float angle) {
_angleY = angle;
}
public void setAngleZ(float angle) {
_angleZ = angle;
}
FloatBuffer InitFloatBuffer(float[] src){
ByteBuffer bb = ByteBuffer.allocateDirect(4*src.length);
bb.order(ByteOrder.nativeOrder());
FloatBuffer inBuf = bb.asFloatBuffer();
inBuf.put(src);
return inBuf;
}
ShortBuffer InitShortBuffer(short[] src){
ByteBuffer bb = ByteBuffer.allocateDirect(2*src.length);
bb.order(ByteOrder.nativeOrder());
ShortBuffer inBuf = bb.asShortBuffer();
inBuf.put(src);
return inBuf;
}
private void initTriangles() {
float[] coords = {
-0.25f, -0.5f, 0.25f,
0.25f, -0.5f, 0.25f,
0f, 0.5f, 0f
};
float[] coords1 = {
0.25f, -0.5f, 0.25f,
0.25f, -0.5f, -0.25f,
0f, 0.5f, 0f
};
float[] coords2 = {
0.25f, -0.5f, -0.25f,
-0.25f, -0.5f, -0.25f,
0f, 0.5f, 0f
};
float[] coords3 = {
-0.25f, -0.5f, -0.25f,
-0.25f, -0.5f, 0.25f,
0f, 0.5f, 0f
};
float[] coords4 = {
-0.25f, -0.5f, 0.25f,
0.25f, -0.5f, -0.25f,
0.25f, -0.5f, 0.25f
};
float[] coords5 = {
-0.25f, -0.5f, 0.25f,
-0.25f, -0.5f, -0.25f,
0.25f, -0.5f, -0.25f
};
float[] textures0123 = {
0.0f, 0.0f,
1.0f, 0.0f,
0.5f, 1.0f,
};
_vertexBuffer0 = InitFloatBuffer(coords);
_vertexBuffer0.position(0);
_vertexBuffer1 = InitFloatBuffer(coords1);
_vertexBuffer1.position(0);
_vertexBuffer2 = InitFloatBuffer(coords2);
_vertexBuffer2.position(0);
_vertexBuffer3 = InitFloatBuffer(coords3);
_vertexBuffer3.position(0);
_vertexBuffer4 = InitFloatBuffer(coords4);
_vertexBuffer4.position(0);
_vertexBuffer5 = InitFloatBuffer(coords5);
_vertexBuffer5.position(0);
_textureBuffer0123 = InitFloatBuffer(textures0123);
_textureBuffer0123.position(0);
short[] indices = {0, 1, 2};
_indexBuffer = InitShortBuffer(indices);
_indexBuffer.position(0);
}
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
gl.glEnable(GL10.GL_CULL_FACE);
gl.glShadeModel(GL10.GL_SMOOTH);
gl.glFrontFace(GL10.GL_CCW);
gl.glCullFace(GL10.GL_BACK);
initTriangles();
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
}
public void onDrawFrame(GL10 gl) {
gl.glPushMatrix();
gl.glClearColor(0, 0, 0, 1.0f);
gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
gl.glRotatef(_angleY, 0f, 1f, 0f);
gl.glRotatef(_angleX, 1f, 0f, 0f);
gl.glRotatef(_angleZ, 0f, 0f, 1f);
gl.glColor4f(0.5f, 0f, 0f, 0.5f);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, _vertexBuffer0);
gl.glDrawElements(GL10.GL_TRIANGLES, _numVertices, GL10.GL_UNSIGNED_SHORT, _indexBuffer);
gl.glColor4f(0.5f, 0.5f, 0f, 0.5f);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, _vertexBuffer1);
gl.glDrawElements(GL10.GL_TRIANGLES, _numVertices, GL10.GL_UNSIGNED_SHORT, _indexBuffer);
gl.glColor4f(0f, 0.5f, 0f, 0.5f);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, _vertexBuffer2);
gl.glDrawElements(GL10.GL_TRIANGLES, _numVertices, GL10.GL_UNSIGNED_SHORT, _indexBuffer);
gl.glColor4f(0f, 0.5f, 0.5f, 0.5f);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, _vertexBuffer3);
gl.glDrawElements(GL10.GL_TRIANGLES, _numVertices, GL10.GL_UNSIGNED_SHORT, _indexBuffer);
gl.glColor4f(0f, 0f, 0.5f, 0.5f);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, _vertexBuffer4);
gl.glDrawElements(GL10.GL_TRIANGLES, _numVertices, GL10.GL_UNSIGNED_SHORT, _indexBuffer);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, _vertexBuffer5);
gl.glDrawElements(GL10.GL_TRIANGLES, _numVertices, GL10.GL_UNSIGNED_SHORT, _indexBuffer);
gl.glPopMatrix();
}
public void onSurfaceChanged(GL10 gl, int w, int h) {
gl.glViewport(0, 0, w, h);
gl.glViewport(0, 0, w, h);
}
}
请注意,此代码未考虑平板电脑默认的横向方向,因此只能在手机上正常工作(我没有附近的平板电脑来测试任何修正代码)。