c++ - Interpretation of IMU-Data (ROS & XSens MTi) -

we have xsens mti , subscribe imu data via sensor_msgs::imu.

the output of linear_acceleration is:

x: 0.12 y: 0.02 z: 9.83

all changing in small range. data tell me? why robot apparently accelerating in z-direction. robot stands still.

orientation data good, linear acceleration confuse me.

the acceleration in z-direction caused gravity of earth 9.81 n/kg (or equivalently m/s²) small variation depending on actual location on earth. if object standing still, accelerated amount towards ground (this why things fall down, if there nothing hold them). if want know acceleration of robot relative surroundings have subtract value.

some implications of this:

1. if z-acceleration zero, means robot in free fall. robot late then, applications can useful detect , activate safety functions prevent damage.
2. you can use fact calculate orientation of sensor. example if have y = 9.81 , z = 0, means robot has fallen side. in case, small non-zero values of x , y indicate sensor not oriented absolutely horizontal.