Bias estimation device, forklift, bias estimation method, and program
A bias estimation device includes 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.
1 . 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;
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.
2 . The bias estimation device according to claim 1 , 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.
3 . 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.
4 . The bias estimation device according to claim 1 , wherein the determination unit acquires information on whether the forklift is being charged, determines that the forklift is stationary when the forklift is being charged, and determines that the forklift is not stationary when the forklift is not being charged.
5 . The bias estimation device according to claim 1 , further comprising
a sudden change portion detection unit configured to detect a sudden change portion of the IMU measurement value accumulated in the accumulation unit, wherein
the accumulation unit deletes the IMU measurement value of the sudden change portion detected by the sudden change portion detection unit and the IMU measurement values of before and after the detected sudden change portion,
the calculation unit calculates the bias based on the IMU measurement value remaining after deletion, and
the sudden change portion detection unit specifies, as a sudden change portion, a section including data having a deviation of equal to or greater than a certain width from an average of the IMU measurement values in a temporally continuous section in the accumulated data.
6 . The bias estimation device according to claim 1 , further comprising:
a temperature value accumulation unit configured to accumulate time-series temperature data regarding an ambient temperature of the forklift; and
a temperature change detection unit configured to detect whether the ambient temperature has changed by equal to or greater than a reference based on the time-series temperature data accumulated in the temperature value accumulation unit, wherein
the accumulation unit accumulates the IMU measurement value when the temperature change detection unit determines that the ambient temperature has changed by equal to or greater than the reference and the determination unit determines that the forklift is stationary.
7 . The bias estimation device according to claim 1 , wherein
the first sensor is a sensor that detects a rotation speed and/or a change of steering angle of a tire included in the forklift, and
the second sensor is a sensor that detects a change of lifting height position of a fork included in the forklift and/or a change of weight of a cargo loaded on the fork.
8 . A forklift, comprising:
a traveling body;
a cargo handling device;
the bias estimation device according to claim 1 ; and
a positioning device configured to compensate the IMU measurement value by using the bias estimation device and determine a position of the forklift based on the IMU measurement value after compensation.
9 . The bias estimation device according to claim 1 , further comprising
a sudden change portion detection unit configured to apply a random sample consensus (RANSAC) algorithm to the accumulated IMU measurement value data accumulated in the accumulation unit to determine an outlier and a normal value, wherein
the accumulation unit deletes the IMU measurement value determined to be an outlier and the IMU measurement values before and after the determined IMU measurement value, and
the calculation unit calculates the bias based on the IMU measurement value remaining after deletion.
10 . The bias estimation device according to claim 9 , wherein
the sudden change portion detection unit learns the IMU measurement value not including the sudden change portion and the IMU measurement value deleted, and construct a model distinguishes them, and determines whether or not each of the IMU measurement values accumulated in the IMU measurement value accumulation unit belongs to the sudden change portion based on the learned model, and
the accumulation unit deletes the IMU measurement value determined to belong to the IMU measurement value deleted and the IMU measurement values before and after the determined IMU measurement value.
11 . 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.
12 . 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.
13 . 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.