implementing

Author: AtsushiSakai

Localization/extended_kalman_filter/extended_kalman_filter.py

@@ -1,15 +1,272 @@
 """
 
-Extended kalman filter localization sample
+Extended kalman filter (EKF) localization sample
 
 author: Atsushi Sakai (@Atsushi_twi)
 
 """
 
+import numpy as np
+import math
+import matplotlib.pyplot as plt
+
+
+#  Covariance Matrix for motion
+#  Q=diag([0.1 0.1 toRadian(1) 0.05]).^2;
+
+#  % Covariance Matrix for observation
+#  R=diag([1.5 1.5 toRadian(3) 0.05]).^2;
+
+#  % Simulation parameter
+#  global Qsigma
+#  Qsigma=diag([0.1 toRadian(20)]).^2; %[v yawrate]
+
+#  global Rsigma
+#  Rsigma=diag([1.5 1.5 toRadian(3) 0.05]).^2;%[x y z yaw v]
+
+#  PEst = eye(4);
+
+#  u=doControl(time);
+#  % Observation
+#  [z,xTrue,xd,u]=Observation(xTrue, xd, u);
+
+#  % ------ Kalman Filter --------
+#  % Predict
+#  xPred = f(xEst, u);
+#  F=jacobF(xPred, u);
+#  PPred= F*PEst*F' + Q;
+
+#  % Update
+#  H=jacobH(xPred);
+#  y = z - h(xPred);
+#  S = H*PPred*H' + R;
+#  K = PPred*H'*inv(S);
+#  xEst = xPred + K*y;
+#  PEst = (eye(size(xEst,1)) - K*H)*PPred;
+
+#  % Simulation Result
+#  result.time=[result.time; time];
+#  result.xTrue=[result.xTrue; xTrue'];
+#  result.xd=[result.xd; xd'];
+#  result.xEst=[result.xEst;xEst'];
+#  result.z=[result.z; z'];
+#  result.PEst=[result.PEst; diag(PEst)'];
+#  result.u=[result.u; u'];
+
+#  %Animation (remove some flames)
+#  if rem(i,5)==0
+#  %hold off;
+#  plot(result.xTrue(:,1),result.xTrue(:,2),'.b');hold on;
+#  plot(result.z(:,1),result.z(:,2),'.g');hold on;
+#  plot(result.xd(:,1),result.xd(:,2),'.k');hold on;
+#  plot(result.xEst(:,1),result.xEst(:,2),'.r');hold on;
+#  ShowErrorEllipse(xEst,PEst);
+#  axis equal;
+#  grid on;
+#  drawnow;
+#  %movcount=movcount+1;
+#  %mov(movcount) = getframe(gcf);% アニメーションのフレームをゲットする
+#  end
+#  end
+#  toc
+#  %アニメーション保存
+#  %movie2avi(mov,'movie.avi');
+
+#  DrawGraph(result);
+
+#  function ShowErrorEllipse(xEst,PEst)
+#  %誤差分散円を計算し、表示する関数
+#  Pxy=PEst(1:2,1:2);%x,yの共分散を取得
+#  [eigvec, eigval]=eig(Pxy);%固有値と固有ベクトルの計算
+#  %固有値の大きい方のインデックスを探す
+#  if eigval(1,1)>=eigval(2,2)
+#  bigind=1;
+#  smallind=2;
+#  else
+#  bigind=2;
+#  smallind=1;
+#  end
+
+#  chi=9.21;%誤差楕円のカイの二乗分布値　99%
+
+#  %楕円描写
+#  t=0:10:360;
+#  a=sqrt(eigval(bigind,bigind)*chi);
+#  b=sqrt(eigval(smallind,smallind)*chi);
+#  x=[a*cosd(t);
+#  b*sind(t)];
+#  %誤差楕円の角度を計算
+#  angle = atan2(eigvec(bigind,2),eigvec(bigind,1));
+#  if(angle < 0)
+#  angle = angle + 2*pi;
+#  end
+
+#  %誤差楕円の回転
+#  R=[cos(angle) sin(angle);
+#  -sin(angle) cos(angle)];
+#  x=R*x;
+#  plot(x(1,:)+xEst(1),x(2,:)+xEst(2))
+
+
+#  function x = f(x, u)
+#  % Motion Model
+#  global dt;
+
+#  F = [1 0 0 0
+#  0 1 0 0
+#  0 0 1 0
+#  0 0 0 0];
+
+#  B = [
+#  dt*cos(x(3)) 0
+#  dt*sin(x(3)) 0
+#  0 dt
+#  1 0];
+
+#  x= F*x+B*u;
+
+#  function jF = jacobF(x, u)
+#  % Jacobian of Motion Model
+#  global dt;
+
+#  jF=[
+#  1 0 0 0
+#  0 1 0 0
+#  -dt*u(1)*sin(x(3)) dt*u(1)*cos(x(3)) 1 0
+#  dt*cos(x(3)) dt*sin(x(3)) 0 1];
+
+#  function z = h(x)
+#  %Observation Model
+
+#  H = [1 0 0 0
+#  0 1 0 0
+#  0 0 1 0
+#  0 0 0 1 ];
+
+#  z=H*x;
+
+#  function jH = jacobH(x)
+#  %Jacobian of Observation Model
+
+#  jH =[1 0 0 0
+#  0 1 0 0
+#  0 0 1 0
+#  0 0 0 1];
+
+
+#  function [z, x, xd, u] = Observation(x, xd, u)
+#  %Calc Observation from noise prameter
+#  global Qsigma;
+#  global Rsigma;
+
+#  x=f(x, u);% Ground Truth
+#  u=u+Qsigma*randn(2,1);%add Process Noise
+#  xd=f(xd, u);% Dead Reckoning
+#  z=h(x+Rsigma*randn(4,1));%Simulate Observation
+
+
+#  function []=DrawGraph(result)
+#  %Plot Result
+
+#  figure(1);
+#  x=[ result.xTrue(:,1:2) result.xEst(:,1:2) result.z(:,1:2)];
+#  set(gca, 'fontsize', 16, 'fontname', 'times');
+#  plot(x(:,5), x(:,6),'.g','linewidth', 4); hold on;
+#  plot(x(:,1), x(:,2),'-.b','linewidth', 4); hold on;
+#  plot(x(:,3), x(:,4),'r','linewidth', 4); hold on;
+#  plot(result.xd(:,1), result.xd(:,2),'--k','linewidth', 4); hold on;
+
+#  title('EKF Localization Result', 'fontsize', 16, 'fontname', 'times');
+#  xlabel('X (m)', 'fontsize', 16, 'fontname', 'times');
+#  ylabel('Y (m)', 'fontsize', 16, 'fontname', 'times');
+#  legend('Ground Truth','GPS','Dead Reckoning','EKF','Error Ellipse');
+#  grid on;
+#  axis equal;
+
+#  function angle=Pi2Pi(angle)
+#  %ロボットの角度を-pi~piの範囲に補正する関数
+#  angle = mod(angle, 2*pi);
+
+#  i = find(angle>pi);
+#  angle(i) = angle(i) - 2*pi;
+
+#  i = find(angle<-pi);
+#  angle(i) = angle(i) + 2*pi;
+
+
+#  function radian = toRadian(degree)
+#  % degree to radian
+#  radian = degree/180*pi;
+
+#  function degree = toDegree(radian)
+#  % radian to degree
+#  degree = radian/pi*180;
+
+DT = 0.1  # time tick [s]
+SIM_TIME = 60.0  # simulation time [s]
+
+
+def do_control():
+    v = 1.0  # [m/s]
+    yawrate = 0.1  # [rad/s]
+
+    u = np.matrix([v, yawrate]).T
+
+    return u
+
+
+#  z, xTrue, xd, u = Observation(xTrue, xd, u)
+def observation(xTrue, xd, u):
+
+    xTrue = motion_model(xTrue, u)
+
+    return xTrue
+
+
+def motion_model(x, u):
+
+    F = np.matrix([[1.0, 0, 0, 0],
+                   [0, 1.0, 0, 0],
+                   [0, 0, 1.0, 0],
+                   [0, 0, 0, 0]])
+
+    B = np.matrix([[DT * math.cos(x[2, 0]), 0],
+                   [DT * math.sin(x[2, 0]), 0],
+                   [0.0, DT],
+                   [1.0, 0.0]])
+
+    x = F * x + B * u
+
+    return x
+
 
 def main():
     print(__file__ + " start!!")
 
+    time = 0.0
+    # State Vector [x y yaw v]'
+    #  xEst = np.matrix(np.zeros((3, 1)))
+    xTrue = np.matrix(np.zeros((4, 1)))
+
+    # Dead Reckoning
+    xDR = np.matrix(np.zeros((4, 1)))
+
+    # Observation vector
+    #  z = np.matrix(np.zeros((2, 1)))
+
+    while SIM_TIME >= time:
+        #  print(time)
+        time += DT
+
+        u = do_control()
+
+        xTrue = observation(xTrue, xDR, u)
+
+        plt.plot(xTrue[0, 0], xTrue[1, 0], ".r")
+        plt.axis("equal")
+        plt.grid(True)
+        plt.pause(0.001)
+
 
 if __name__ == '__main__':
     main()