Underwater sailing body and method of controlling posture of underwater sailing body

An underwater sailing body comprising:

• a positioning device configured to detect positional information indicating a position of a hull of the underwater sailing body;
• a posture detecting sensor configured to detect posture information indicating a posture of the hull;
• an actuator configured to apply thrust to the hull in a front-rear direction of the hull, a left-right direction of the hull, and an upper-lower direction of the hull in water to change the position and posture of the hull;
• and
• a controller configured to control the actuator, wherein:
• in order to hold the hull at a target position based on the positional information detected by the positioning device, the controller calculates a controlling force in the front-rear direction of the hull, a controlling force in the left-right direction of the hull, a controlling force in the upper-lower direction of the hull, a turn controlling force of turning the hull in a roll direction of the hull, a turn controlling force of turning the hull in a yaw direction of the hull, and a turn controlling force of turning the hull in a pitch direction of the hull, and controls the actuator based on the calculated forces,
• when an external force is applied to the hull held at the target position, the controller updates target posture information such that each of the controlling force in the left-right direction and the controlling force in the upper-lower direction becomes zero, and controls the actuator such that the posture of the hull is changed to a posture corresponding to the updated posture information based on the posture information detected by the posture detecting sensor,
• the controller includes a controlling force calculating portion configured to calculate the controlling force in the front-rear direction, the controlling force in the left-right direction, the controlling force in the upper-lower direction, the turn controlling force in the roll direction, the turn controlling force in the yaw direction, and the turn controlling force in the pitch direction from a difference between target positional information and the positional information detected by the positioning device and a difference between the target posture information and the posture information detected by the posture detecting sensor,
• when the external force is applied to the hull held at the target position, the controller updates a command value of a yaw angle of the target posture information and a command value of a pitch angle of the target posture information such that each of the controlling force in the left-right direction and the controlling force in the upper-lower direction, which are calculated by the controlling force calculating portion, becomes zero,
• the controller includes:
• a yaw angle command value calculating portion configured to integrate a value of the controlling force in the left-right direction to calculate a target command value of the yaw angle;
• and
• a pitch angle command value calculating portion configured to integrate a value of the controlling force in the upper-lower direction to calculate a target command value of the pitch angle,
• until each of the controlling force in the left-right direction and the controlling force in the upper-lower direction becomes zero, the controller updates the command value of the yaw angle and the command value of the pitch angle by the command value calculated by the yaw angle command value calculating portion and the command value calculated by the pitch angle command value calculating portion,
• the yaw angle command value calculating portion calculates the target command value of the yaw angle from a value obtained by integrating a value obtained by multiplying the value of the controlling force in the left-right direction by a gain,
• the pitch angle command value calculating portion calculates the target command value of the pitch angle from a value obtained by integrating a value obtained by multiplying the value of the controlling force in the upper-lower direction by a gain, and
• the controller changes a value of the gain by which the yaw angle command value calculating portion multiplies the value of the controlling force in the left-right direction and a value of the gain by which the pitch angle command value calculating portion multiplies the value of the controlling force in the upper-lower direction, and updates the command value of the yaw angle and the command value of the pitch angle in this order, or the controller sets a speed of updating the command value of the pitch angle to be lower than a speed of updating the command value of the yaw angle.