Bias estimation device, forklift, bias estimation method, and program

A bias estimation device, comprising:

• a determination unit configured to determine whether a forklift is stationary based on a measurement value from a first sensor configured to detect information regarding movement of the forklift and a measurement value from a second sensor configured to detect information regarding a cargo handling device included in the forklift;
• an accumulation unit configured to accumulate an IMU measurement value that is a measurement value from an inertial measurement unit included in the forklift when the determination unit determines that the forklift is stationary and stop accumulation of the IMU measurement value when the determination unit determines that the forklift is not stationary;
• and
• a calculation unit configured to calculate a bias of the IMU measurement value based on the IMU measurement value accumulated in the accumulation unit,
• wherein the determination unit determines that the forklift is stationary when a first condition that a measurement value from the first sensor does not indicate that the forklift is moving and that a measurement value from the second sensor does not indicate that the forklift is in cargo handling operation is satisfied and determines that the forklift is not stationary when the first condition is not satisfied,
• wherein the determination unit acquires information on whether the inertial measurement unit is activated, determines that the forklift is stationary when the inertial measurement unit is activated and the first condition is satisfied, and determines that the forklift is not stationary otherwise,
• wherein the calculation unit outputs the bias of the IMU measurement value which is calculated.

A bias estimation device, comprising:

• a determination unit configured to acquire information on whether a forklift is being charged, determine that the forklift is stationary when the forklift is being charged, and determine that the forklift is not stationary when the forklift is not being charged;
• an accumulation unit configured to accumulate an IMU measurement value that is a measurement value from an inertial measurement unit included in the forklift when the determination unit determines that the forklift is stationary and stop accumulation of the IMU measurement value when the determination unit determines that the forklift is not stationary;
• an accumulated sample number monitoring unit configured to determine that a sufficient number of samples for estimating the bias of the IMU measurement values have been obtained when the number of accumulated IMU measurement values becomes equal to or greater than a threshold;
• a calculation unit configured to calculate a bias of the IMU measurement value based on the IMU measurement value accumulated in the accumulation unit in response to being determined that a sufficient number of samples for estimating the bias of the IMU measurement values have been obtained;
• and
• an end determination unit configured to delete the IMU measurement values accumulated so far when the calculation unit ends the calculation of the bias or the determination unit determines the forklift is not stationary,
• wherein the calculation unit outputs the bias of the IMU measurement value which is calculated.

A bias estimation method, comprising:

• a step of repeatedly determining whether a forklift is stationary based on a measurement value from a first sensor configured to detect information regarding movement of the forklift and a measurement value from a second sensor configured to detect information regarding a cargo handling device included in the forklift;
• a step of accumulating an IMU measurement value that is a measurement value from an inertial measurement unit included in the forklift when the forklift is determined to be stationary in the step of determining;
• a step of stopping accumulation of the IMU measurement value and deleting the IMU measurement value when the forklift is determined to be not stationary in the step of determining;
• a step of determining that a sufficient number of samples for estimating the bias of the IMU measurement values have been obtained when the number of accumulated IMU measurement values becomes equal to or greater than a threshold;
• a step of calculating a bias of the IMU measurement value based on the IMU measurement value accumulated in response to being determined, in the step of determining, that a sufficient number of samples for estimating the bias of the IMU measurement values have been obtained;
• and
• a step of deleting the IMU measurement values accumulated when the calculation of the bias is ended,
• wherein, in the step of calculating, outputting the bias of the IMU measurement value which is calculated.

A non-transitory computer readable storage medium storing a program that causes a computer to execute:

• a step of repeatedly determining whether a forklift is stationary based on a measurement value from a first sensor configured to detect information regarding movement of the forklift and a measurement value from a second sensor configured to detect information regarding a cargo handling device included in the forklift;
• a step of accumulating an IMU measurement value that is a measurement value from an inertial measurement unit included in the forklift when the forklift is determined to be stationary in the step of determining;
• a step of stopping accumulation of the IMU measurement value and deleting the IMU measurement value when the forklift is determined to be not stationary in the step of determining;
• a step of determining that a sufficient number of samples for estimating the bias of the IMU measurement values have been obtained when the number of accumulated IMU measurement values becomes equal to or greater than a threshold;
• a step of calculating a bias of the IMU measurement value based on the IMU measurement value accumulated in response to being determined, in the step of determining, that a sufficient number of samples for estimating the bias of the IMU measurement values have been obtained;
• and
• a step of deleting the IMU measurement values accumulated when the calculation of the bias is ended,
• wherein, in the step of calculating, outputting the bias of the IMU measurement value which is calculated.