A gantry configuration for a combined mobile radiation inspection system, comprising: a first arm frame configured to be movable along a first rail ; a second arm frame , opposite to the first arm frame , configured to be movable along a second rail parallel to the first rail ; and a horizontal third arm frame connecting the first and second arm frames , so as to move with the first and second arm frames , wherein the first, second and third arm frames together define a scanning channel to allow an inspected object to pass therethrough, wherein the gantry configuration for the combined mobile radiation inspection system further comprising: a position sensing device configured to detect a position error (e) between the first arm frame and the second arm frame ; a radiation source mounted on one of the first arm frame and the second arm frame and configured to emit a ray onto the inspected object passing through the scanning channel, and a radiation detector mounted on the other of the first arm frame and the second arm frame and configured to receive the ray emitted from the radiation source; and a controller configured to control a moving speed of at least one of the first arm frame and the second arm frame based on the position error (e) detected by the position sensing device , so that the position error (e) between the first arm frame and the second arm frame is equal to zero, characterised in that the position sensing device comprises a deformation sensor configured for detecting a deformation of the horizontal third arm frame so as to determine the position error between the first arm frame and the second arm frame based on the deformation. a first arm frame configured to be movable along a first rail ; a second arm frame , opposite to the first arm frame , configured to be movable along a second rail parallel to the first rail ; and a horizontal third arm frame connecting the first and second arm frames , so as to move with the first and second arm frames , wherein the first, second and third arm frames together define a scanning channel to allow an inspected object to pass therethrough, wherein the gantry configuration for the combined mobile radiation inspection system further comprising: a position sensing device configured to detect a position error (e) between the first arm frame and the second arm frame ; a radiation source mounted on one of the first arm frame and the second arm frame and configured to emit a ray onto the inspected object passing through the scanning channel, and a radiation detector mounted on the other of the first arm frame and the second arm frame and configured to receive the ray emitted from the radiation source; and a position sensing device configured to detect a position error (e) between the first arm frame and the second arm frame ; a radiation source mounted on one of the first arm frame and the second arm frame and configured to emit a ray onto the inspected object passing through the scanning channel, and a radiation detector mounted on the other of the first arm frame and the second arm frame and configured to receive the ray emitted from the radiation source; and a controller configured to control a moving speed of at least one of the first arm frame and the second arm frame based on the position error (e) detected by the position sensing device , so that the position error (e) between the first arm frame and the second arm frame is equal to zero, characterised in that the position sensing device comprises a deformation sensor configured for detecting a deformation of the horizontal third arm frame so as to determine the position error between the first arm frame and the second arm frame based on the deformation. <EOS>