JP4449911B2 - Autonomous mobile device - Google Patents

Description

  The present invention relates to an autonomous mobile device that travels while performing self-position estimation.

  Conventionally, there is a self-propelled vehicle that realizes an autonomous movement function by independently controlling two drive wheels, that is, an autonomous mobile device. In order to estimate the self position of the self-propelled vehicle, travel distance information and rotation information of the self-propelled vehicle body are required. Two methods for obtaining rotation information are known. One is a method based on output information from a gyro mounted on the self-propelled vehicle main body, and the other is a rotation drive source of left and right drive wheels, for example, a rotation signal of an encoder attached to a motor and left and right drive. This is a method based on the dimensions and arrangement of the wheels. Both methods have the following advantages and disadvantages.

  The method using the gyro has an advantage that the estimation accuracy of the rotation angle is high, but there is a disadvantage that a dead zone needs to be provided due to the influence of noise below a certain angular velocity, and a minute rotation angle cannot be estimated. In addition, although the method using the encoder does not need to provide a dead zone, there is a drawback that the error becomes large when the rotation of the motor is not sufficiently reflected as the rotational motion of the self-propelled vehicle due to the presence of wheel slip or the like.

Therefore, in order to eliminate the above-mentioned drawbacks, both the gyro and the encoder are provided, and the estimation accuracy of the rotation information is increased by using the gyro and the encoder properly, and the control according to the magnitude of the disturbance of the driving wheel slip is performed. There is known a traveling control device intended to correct an appropriate direction. For example, as shown in FIG. 3, when the angular velocity ωg from the gyro is greater than a certain threshold value ωth, the gyro angular velocity ωg is used. Otherwise, the angular velocity ωm from the encoder is used. Some perform control (see, for example, Patent Document 1).
JP 05-66829 A

  However, when the travel control device as shown in Patent Document 1 described above is applied to an autonomous mobile device, the effect of slip or the effect of backlash that occurs when the autonomous mobile device starts moving from a stopped state is reflected in the rotation information. There is a problem that a self-position estimation error occurs.

  The present invention solves the above-mentioned problems, and with a simple configuration, suppresses the effects of slip and backlash, calculates the angular velocity of the autonomous mobile device body more accurately, and improves the accuracy of self-position estimation. It aims at providing the autonomous mobile device which can be realized.

In order to achieve the above object, an invention according to claim 1 is an autonomous mobile device that autonomously moves by performing self-position estimation using the rotation angle and the movement displacement of the autonomous mobile device body. Drive wheels, a rotation motor that rotationally drives each drive wheel, an encoder that outputs a rotation signal based on the rotation amount of each rotation motor, and an autonomous mobile device main body based on each rotation signal from the encoder An angular velocity calculation unit that calculates an angular velocity, a gyro that directly acquires the angular velocity of the autonomous mobile device body, an angular velocity calculated by the angular velocity calculation unit, and an angular velocity obtained from the gyro, A travel control unit that performs travel control of the autonomous mobile device main body by controlling rotation of the motor based on the estimated rotation angle and the movement displacement, and the travel Control unit, when the absolute value of the difference between the obtained angular velocity from the the calculated angular by the angular velocity calculating section gyro is greater than a predetermined value is carried out to estimate the rotation angle by using the angular velocity obtained from the gyro When the absolute value of the difference between the angular velocities is smaller than or equal to the predetermined amount, the rotation angle is estimated using the angular velocities calculated by the angular velocity calculation unit.

  According to the first aspect of the present invention, the self-position estimation can be performed using the gyro when the rotation of the motor whose encoder is measuring the rotation amount is not sufficiently utilized as the rotational motion of the driving wheel. High traveling control can be performed. For example, when slip or backlash occurs when the autonomous mobile device starts to move from a stopped state, the actual angular velocity ω is reduced although the angular velocity ωm obtained from the encoder is large. In this case, the angular velocity ωg from the gyro is closer to the actual value than the angular velocity ωm from the encoder, and more accurate traveling control can be performed.

  Hereinafter, an autonomous mobile device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of an autonomous mobile device 1 according to an embodiment of the present invention. The autonomous mobile device 1 is based on a pair of driving wheels 2 for movement, a pair of rotation motors 3 that respectively rotate and drive the respective driving wheels 2, and a rotation amount of the motor 3 provided corresponding to each motor 3. A pair of encoders 4 that output the rotation signals, an angular velocity calculation unit 5 that calculates an angular velocity of the autonomous mobile device body based on the rotation signals from each encoder 4, and a gyro 6 that directly acquires the angular velocity of the autonomous mobile device body; A movement displacement acquisition unit 7 that acquires the movement displacement of the autonomous mobile device main body based on each rotation signal from the encoder 4 and a travel control unit that controls the rotation of the motor 3 to control the traveling of the autonomous mobile device main body. 10. The travel control unit 10 estimates the rotation angle of the autonomous mobile device body using the angular velocity ωm calculated by the angular velocity calculation unit 5 and the angular velocity ωg obtained from the gyro 6 and acquires the estimated rotation angle and movement displacement. The self-position is estimated based on the movement displacement acquired by the unit 7. The traveling control unit 10 further performs traveling control of the autonomous mobile device body by controlling the rotation of the motor 3 based on the estimation of the self position. Here, the movement displacement is an xy coordinate value in an xy coordinate system that defines an area in which the autonomous mobile device 1 travels and moves. The self position of the autonomous mobile device 1 is determined by the movement displacement that is the xy coordinate value and the posture of the self at that position, that is, the rotation angle.

In addition, the traveling control unit 10 determines which of the two angular velocities ωm and ωg is used when estimating the rotation angle. That is, the traveling control unit 10 determines the angular velocity ωg obtained from the gyro 6 when the absolute value of the difference between the angular velocity ωm calculated by the angular velocity calculation unit 5 and the angular velocity ωg obtained from the gyro 6 is larger than a predetermined threshold ωth. Is used to estimate the rotation angle. When the absolute value of the difference between the angular velocities is smaller than the threshold ωth, the rotation angle is estimated using the angular velocity ωm calculated by the angular velocity calculation unit 5.

  The self-position estimation will be further described. The autonomous mobile device 1 assumes that the position of the autonomous mobile device 1 in the coordinate system that defines the space in which the autonomous mobile device 1 travels is known and the direction in which the autonomous mobile device 1 is facing, and determines the position of the autonomous mobile device 1 through dead reckoning from that point. And move autonomously while checking the direction. Dead reckoning calculates the amount of movement (rotation angle and movement displacement) based on the information obtained internally without obtaining information from the outside, and calculates the current self position by integrating the amount of movement from the initial position. This is the technology that we want.

  Since the change in the rotation angle described above is caused by the rotation of the autonomous mobile device 1, it is obtained using the angular velocity of the rotation of the autonomous mobile device body. In other words, the rotation angle is obtained by time-integrating the angular velocity, and the rotation angle determines its own posture, that is, the current moving direction. Moreover, when calculating | requiring angular velocity based on the rotation signal from the encoder 4, it calculates | requires as follows. That is, the rotation signal information is finally converted into the rotation amount per unit time of the left and right drive wheels 2 by the angular velocity calculation unit 5, and the rotation amount, the diameter of the drive wheel 2, and the two drive Based on the distance between the wheels 2, the angular velocity is determined. In other words, the angular velocity calculation unit 5 calculates the angular velocity based on the rotation signal of the encoder attached to the motor and the dimensions and arrangement shapes of the left and right drive wheels. The autonomous mobile device 1 moves forward when the left and right drive wheels 2 rotate forward, moves backward when reversed, and curves right or left when the left and right rotation amounts differ. Furthermore, if the left and right drive wheels 2 are reversed, the autonomous mobile device 1 rotates on the spot.

  When the angular velocity is directly obtained using a gyro, for example, a gyro sensor formed by a MEMS (micro electro mechanical systems) technique can be used.

Next, with reference to FIG. 2, a description will be given of the travel control process focusing on the handling of the angular velocity used for estimating the rotation angle in the autonomous mobile device 1. When the autonomous mobile device 1 starts moving from the initial state where the self-position is fixed, the traveling control unit 10 acquires the angular velocity ωg from the gyro 6 and the angular velocity ωm from the angular velocity calculating unit 5 for each predetermined control period. The absolute value of the difference is obtained, and the absolute value of the difference is compared with a predetermined threshold value ωth (S1). Here, as the threshold value ωth, for example, a value of the gyro 6 that is normally set to the dead zone ωx is used. Here, the dead zone ωx of the angular velocity is a region where the value of the angular velocity is small and the signal-to-noise ratio (S / N ratio) is relatively poor. In the present invention, a dead zone is not provided, that is, even if the value of the angular velocity ωg is small, the value is adopted depending on conditions.

  As a result of the above comparison, when the absolute value of the difference between the angular velocity ωg of the gyro 6 and the angular velocity ωm of the angular velocity calculation unit 5 is larger than the threshold ωth, that is, | ωm−ωg |> ωth (Yes in S1), The traveling control unit 10 estimates the rotation angle using the gyro angular velocity ωg and performs self-position estimation (S2). Further, in the case of | ωm−ωg | ≦ ωth (No in S1), the traveling control unit 10 estimates the rotation angle using the angular velocity ωm of the angular velocity calculation unit 5 and performs self-position estimation (S3). The traveling control unit 10 repeats such self-position estimation at a predetermined control cycle until the control is completed (S4).

The case where the absolute value of the difference between the angular velocities is larger than the threshold ωth is, for example, when making a difference by rotating the left and right drive wheels 2 and turning left and right, or stopping one of them and turning. This is a case where both the drive wheels 2 or the drive wheel 2 on one side slips to increase the angular velocity ωm when the drive wheels 2 are idle, while the actual angular velocity of the autonomous mobile device body becomes substantially zero. In such a case, even if the angular velocity ωg from the gyro 6 is smaller than the value normally set as the dead zone ωx, the angular velocity ωg of the gyro 6 is more than the angular velocity ωm of the angular velocity calculator 5. Since it is considered to be closer to the actual angular velocity, more accurate traveling control can be realized.

  The present invention is not limited to the above-described configuration, and various modifications can be made. In the above, an example of the autonomous mobile device 1 provided with a pair of left and right drive wheels, a rotary motor, and an encoder has been shown, but there is no limit to the number and arrangement of these, and there is no limit to the pair of left and right, The present invention is applicable if the angular velocity ωm of the autonomous mobile device body is obtained based on the rotation signal from the encoder. Therefore, the present invention can also be applied to an autonomous mobile device in which drive wheels and steering wheels are different, an autonomous mobile device that includes three or four drive wheels and can move in all directions.

The schematic block block diagram of the autonomous mobile apparatus which concerns on one Embodiment of this invention. The flowchart of the traveling control in an autonomous mobile device same as the above. The flowchart of the traveling control of the conventional autonomous mobile device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Autonomous mobile device 2 Drive wheel 3 Motor 4 Encoder 5 Angular velocity calculation part 6 Gyro 7 Movement displacement acquisition part 10 Travel control part

Claims (1)

An autonomous mobile device that moves autonomously by performing self-position estimation using the rotation angle and movement displacement of the autonomous mobile device body,
A plurality of driving wheels for movement;
A rotation motor for rotating the drive wheels;
An encoder that outputs a rotation signal based on the rotation amount of each of the rotary motors;
An angular velocity calculation unit for calculating an angular velocity of the autonomous mobile device body based on each rotation signal from the encoder;
A gyro that directly acquires the angular velocity of the autonomous mobile device body,
By estimating the rotation angle using the angular velocity calculated by the angular velocity calculation unit and the angular velocity obtained from the gyro, and controlling the rotation of the motor based on the estimated rotation angle and the moving displacement. A traveling control unit that performs traveling control of the autonomous mobile device body,
The travel control unit estimates the rotation angle using the angular velocity obtained from the gyro when the absolute value of the difference between the angular velocity calculated by the angular velocity calculation unit and the angular velocity obtained from the gyro is larger than a predetermined value. An autonomous mobile device characterized in that when the absolute value of the difference between the angular velocities is smaller than or equal to the predetermined amount, the rotational angle is estimated using the angular velocities calculated by the angular velocity calculating unit.

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