Added IMUKittExample
Luca Carlone
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close all
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clc
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import gtsam.*;
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IMU_data = dmlread('IMU.txt');
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VO_data = dmlread('VO.txt');
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GPS_data = dmlread('GPS.txt');
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SummaryTemplate = gtsam.ImuFactorPreintegratedMeasurements( ...
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gtsam.imuBias.ConstantBias([0;0;0], [0;0;0]), ...
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1e-3 * eye(3), 1e-3 * eye(3), 1e-3 * eye(3));
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%% Set initial conditions for the estimated trajectory
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disp('TODO: we have GPS so this initialization is not right')
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currentPoseGlobal = Pose3; % initial pose is the reference frame (navigation frame)
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currentVelocityGlobal = [0;0;0]; % the vehicle is stationary at the beginning
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bias_acc = [0;0;0]; % we initialize accelerometer biases to zero
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bias_omega = [0;0;0]; % we initialize gyro biases to zero
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%% Solver object
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isamParams = ISAM2Params;
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isamParams.setRelinearizeSkip(1);
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isam = gtsam.ISAM2(isamParams);
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%% create nonlinear factor graph
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factors = NonlinearFactorGraph;
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values = Values;
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%% Create prior on initial pose, velocity, and biases
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sigma_init_x = 1.0
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sigma_init_v = 1.0
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sigma_init_b = 1.0
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values.insert(symbol('x',0), currentPoseGlobal);
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values.insert(symbol('v',0), LieVector(currentVelocityGlobal) );
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values.insert(symbol('b',0), imuBias.ConstantBias(bias_acc,bias_omega) );
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% Prior on initial pose
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factors.add(PriorFactorPose3(symbol('x',0), ...
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currentPoseGlobal, noiseModel.Isotropic.Sigma(6, sigma_init_x)));
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% Prior on initial velocity
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factors.add(PriorFactorLieVector(symbol('v',0), ...
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LieVector(currentVelocityGlobal), noiseModel.Isotropic.Sigma(3, sigma_init_v)));
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% Prior on initial bias
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factors.add(PriorFactorConstantBias(symbol('b',0), ...
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imuBias.ConstantBias(bias_acc,bias_omega), noiseModel.Isotropic.Sigma(6, sigma_init_b)));
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%% Main loop:
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% (1) we read the measurements
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% (2) we create the corresponding factors in the graph
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% (3) we solve the graph to obtain and optimal estimate of robot trajectory
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i = 2;
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lastTime = 0;
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lastIndex = 0;
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currentSummarizedMeasurement = ImuFactorPreintegratedMeasurements(summaryTemplate);
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times = sort([VO_data(:,1); GPS_data(:,1)]); % this are the time-stamps at which we want to initialize a new node in the graph
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IMU_times = IMU_data(:,1);
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disp('TODO: still needed to take care of the initial time')
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for t = times
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% At each non=IMU measurement we initialize a new node in the graph
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currentIndex = find( times == t );
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currentPoseKey = symbol('x',currentIndex);
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currentVelKey = symbol('v',currentIndex);
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currentBiasKey = symbol('b',currentIndex);
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%% add preintegrated IMU factor between previous state and current state
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% =======================================================================
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IMUbetweenTimesIndices = find( IMU_times>+t_previous & IMU_times<= t);
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% all imu measurements occurred between t_previous and t
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% we assume that each row of the IMU.txt file has the following structure:
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% timestamp delta_t acc_x acc_y acc_z omega_x omega_y omega_z
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disp('TODO: We want don t want to preintegrate with zero bias, but to use the most recent estimate')
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currentSummarizedMeasurement = ImuFactorPreintegratedMeasurements(summaryTemplate);
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for i=1:length(IMUbetweenTimesIndices)
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index = IMUbetweenTimesIndices(i); % the row of the IMU_data matrix that we have to integrate
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deltaT = IMU_data(index,2);
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accMeas = IMU_data(index,3:5);
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omegaMeas = IMU_data(index,6:8);
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% Accumulate preintegrated measurement
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currentSummarizedMeasurement.integrateMeasurement(accMeas, omegaMeas, deltaT);
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end
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disp('TODO: is the imu noise right?')
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% Create IMU factor
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factors.add(ImuFactor( ...
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previousPoseKey, previousVelKey, ...
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currentPoseKey, currentVelKey, ...
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currentBiasKey, currentSummarizedMeasurement, g, cor_v, ...
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noiseModel.Isotropic.Sigma(9, 1e-6)));
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% =======================================================================
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%% add factor corresponding to GPS measurements (if available at the current time)
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% =======================================================================
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if isempty( find(GPS_data(:,1) == t ) ) == 0 % it is a GPS measurement
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if length( find(GPS_data(:,1)) ) > 1
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error('more GPS measurements at the same time stamp: it should be an error')
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end
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index = find(GPS_data(:,1) == t ); % the row of the IMU_data matrix that we have to integrate
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GPSmeas = GPS_data(index,2:4);
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noiseModelGPS = ???; % noiseModelGPS.Isotropic.Sigma(6, sigma_init_x))
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% add factor
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disp('TODO: is the GPS noise right?')
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factors.add(PriorFactor???(currentPoseKey, GPSmeas, noiseModelGPS) );
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end
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% =======================================================================
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%% add factor corresponding to VO measurements (if available at the current time)
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% =======================================================================
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if isempty( find(VO_data(:,1) == t ) )== 0 % it is a GPS measurement
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if length( find(VO_data(:,1)) ) > 1
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error('more VO measurements at the same time stamp: it should be an error')
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end
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index = find( VO_data(:,1) == t ); % the row of the IMU_data matrix that we have to integrate
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VOmeas_pos = VO_data(index,2:4)';
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VOmeas_ang = VO_data(index,5:7)';
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VOpose = Pose3( Rot3(VOmeas_ang) , Point3(VOmeas_pos) );
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noiseModelVO = ???; % noiseModelGPS.Isotropic.Sigma(6, sigma_init_x))
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% add factor
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disp('TODO: is the VO noise right?')
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factors.add(BetweenFactorPose3(lastVOPoseKey, currentPoseKey, VOpose, noiseModelVO));
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lastVOPoseKey = currentPoseKey;
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end
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% =======================================================================
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disp('TODO: add values')
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% values.insert(, initialPose);
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% values.insert(symbol('v',lastIndex+1), initialVel);
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%% Update solver
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% =======================================================================
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isam.update(factors, values);
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factors = NonlinearFactorGraph;
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values = Values;
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isam.calculateEstimate(currentPoseKey);
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% M = isam.marginalCovariance(key_pose);
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% =======================================================================
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previousPoseKey = currentPoseKey;
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previousVelKey = currentVelKey;
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t_previous = t;
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end
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disp('TODO: display results')
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% figure(1)
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% hold on;
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% plot(positions(1,:), positions(2,:), '-b');
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% plot3DTrajectory(isam.calculateEstimate, 'g-');
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% axis equal;
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% legend('true trajectory', 'traj integrated in body', 'traj integrated in nav')
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