JP5874618B2 - Mobile device - Google Patents

Description

  The present invention relates to a mobile device.

  2. Description of the Related Art There is known a mobile device that drives a plurality of wheels to run independently and grips and conveys an object with a gripping unit such as a manipulator. In such a mobile device, it is necessary to estimate the self position in order to control the travel position of the self device.

  The self-position estimation method includes dead reckoning, which is a relative self-position estimation method using a wheel encoder, an inertial sensor, etc., and the robot's position and posture by adding the initial state of the robot and sensor information such as the wheel encoder. Inertial navigation system, which is a method of sequentially calculating the amount of movement, and odometry, etc., which is a method for estimating the position of the robot from the cumulative calculation by calculating the amount of each movement from the calculation of the rotation angle of wheels and steering in a wheeled mobile robot There is.

  In Non-Patent Document 1, in a crawler type mobile robot that runs on rough terrain, the slip amount of the left and right crawlers is estimated from angular velocity information detected by a sensor mounted on the robot body, and the estimated position accuracy by dead reckoning of the crawler type robot is estimated. Techniques for improving the performance are described.

Daisuke Endo and two others, “Improvement of Dead-Reckoning Accuracy of Crawler-Type Mobile Robot by Considering its Slippage”, [online], 2006 September 14, 2012, Proceedings of the Robotics Society of Japan (CD-ROM), [Search on November 26, 2012], Internet (URL: http://www.astro.mech.tohoku.ac.jp) /~keiji/papers/pdf/2006-RSJ-Endo.pdf)

  In the technique described in Non-Patent Document 1, dead reckoning considering slip is formulated, and the position is estimated by measuring the slip with a gyro sensor.

  However, in the technique described in Non-Patent Document 1, it is assumed that the crawler type mobile robot travels on rough terrain, and the amount of slip must be measured sequentially, and a gyro sensor must be mounted on the mobile robot. There was a problem.

  Further, in the technique described in Non-Patent Document 1, there is a problem in that the side slip cannot be measured, and therefore, the side position is not taken into consideration in the estimation of the self-position and accurate correction cannot be performed.

  Furthermore, in a transport device equipped with a manipulator, the floor reaction force applied to the drive wheel changes depending on the weight of the transported object and the posture of the manipulator, so the frequency and degree of slipping change, and the accuracy of dead reckoning is increased. There was a problem of getting worse.

  The present invention has been made to solve such problems, and an object of the present invention is to provide a mobile device that estimates a self-position in consideration of a slip amount.

  The moving device according to the present invention includes a gripping unit that grips a conveyed product, an autonomous moving mechanism including a driving wheel, an arm unit that connects the gripping unit and the autonomous moving mechanism, a floor reaction force applied to the driving wheel, and driving. From the balance between the correction table storage unit that stores the correction coefficient for correcting the slip amount of the wheel and the weight of the gripping unit including the arm unit and the transported object and the weight of the autonomous moving mechanism, A position estimation processing unit that calculates the floor reaction force, reads a correction coefficient corresponding to the floor reaction force from the correction table storage unit, and performs position estimation processing.

  According to the present invention, it is possible to provide a mobile device that estimates a self-position in consideration of a slip amount.

It is a figure which shows the kinematic model of an opposing two-wheeled mobile robot. It is a figure which shows the kinematic model of the crawler type mobile robot described in the nonpatent literature 1. It is a figure which shows the moving body apparatus concerning this Embodiment. It is a figure which shows the correction table concerning embodiment. It is a figure which shows the structure at the time of creating the correction table concerning embodiment. It is a flowchart which shows the process of the dead reckoning of the mobile body device concerning an embodiment.

  The present invention relates to a moving device that includes a manipulator for gripping a conveyed product and moves independently. The main point of the present invention is the position estimation method of the moving device. In order to describe the position estimation method of the mobile device, first, the movement characteristics of the opposed two-wheeled mobile robot will be described.

FIG. 1 is a diagram illustrating a kinematic model of an opposed two-wheeled mobile robot. The circumferential speed of the left wheel 101 is v _l , the circumferential speed of the right wheel 102 is v _r , and the wheel interval is 2d. Also, the speed of the vehicle body center and V _c, the angular velocity of the body center and omega _c. 1 and 2, the vertical direction in the drawing is the y-axis, and the horizontal direction in the drawing is the x-axis.
At this time, the coordinates (x, y) and the azimuth θ of the vehicle body center satisfy the following expressions (1) to (3).

Odometry is a method of measuring the current position and posture with respect to the initial position by integrating the expressions (1) to (3) over time. Odometry can accurately measure the position under the condition that no slip occurs between the wheel and the ground.
However, in actuality, slip always occurs between the wheel and the ground. Therefore, when odometry is applied to position estimation, an error occurs between the estimated position and the actual position.

  FIG. 2 is a diagram illustrating a kinematic model of the crawler type mobile robot described in Non-Patent Document 1. The crawler type mobile robot includes a main body 105 and crawlers 103 and 104 as driving wheels on the left and right sides of the main body 105.

In the kinematic model shown in FIG. 2, the lateral slip of the main body 105 and the longitudinal slip of the left and right crawlers 103 and 104 are considered independently.
Here, the slip ratio of the crawler 103 and a _l, a slip ratio of the crawler 104 and a _r, describing the slip angle as alpha.

The slip angle α is an angle formed by the orientation of the main body and the actual traveling direction, and α ≠ 0 when a side slip occurs. When performing a steady turn, if the outer peripheral speed of the left crawler in FIG. 1 is v _l and the speed of the right crawler is the speed v _r , the coordinates (x, y) and the direction θ of the vehicle body are as follows: The relationship of Formula (4)-(6) is materialized.

Here, in order to more accurately estimate the position of the moving device using the equations (4) to (6), the slip rate of the crawler 103 is a _l , the slip rate a _r of the crawler 104, and the slip angle α. Need to ask.

However, the slip rates a _l and a _r and the slip angle α of the left and right drive wheels change as the floor reaction force applied to the drive wheels changes. For this reason, in a mobile device that includes a manipulator and moves independently, the slip ratios a _l and a _r and the slip angle α of the left and right drive wheels change depending on the weight of the conveyed product and the attitude of the manipulator, It was difficult to estimate the position.

In the present embodiment, there is provided a method for setting dead reckoning more accurately by setting the slip ratios a _l and a _r and the slip angle α of the left and right drive wheels by a simpler method. Hereinafter, this embodiment will be described.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 3 is a diagram illustrating the mobile device 1 according to the embodiment. The mobile device 1 is a device that includes a gripping part 11, an arm part 12, a main body part 13, a pair of front wheels 15, and a pair of rear wheels 16, and transports a transported article by the gripping part 11. .

  The grip part 11 grips the conveyed product. The arm unit 12 connects the grip unit 11 to the main body unit 13. The arm unit 12 includes drive shafts 121 to 123 that are each driven by a motor (not shown), a first link 124, and a second link 125.

  The grip 11 is connected to the first link via the drive shaft 121. The first link 124 is connected to the second link 125 via the drive shaft 122. The second link 125 is connected to the main body 13 through the drive shaft 123. By driving the arm unit 12 drive shafts 121 to 123, the postures of the first link 124 and the second link 125 are changed, and the gripping unit 11 is moved with respect to the main body unit 13.

  The front wheel 15 and the rear wheel 16 are each composed of a pair of wheels and are connected to the main body 13. The front wheel 15 is a drive wheel, and left and right wheels are driven by a drive unit (not shown).

  The main body 13 includes a control unit 14 (not shown), a floor reaction force calculation unit 17, a correction table storage unit 18, and a position estimation unit 19. The control unit 14 controls the arm unit 12 and a drive unit that drives the front wheels 15.

The floor reaction force calculation unit 17 calculates the floor reaction force applied to the front wheel 15. Here, for simplicity, it is assumed that the floor reaction force calculation unit 17 obtains the floor reaction force applied to the front wheel 15 from the static balance of the grip portion 11 and the main body portion 13. The weight applied to the center of gravity of the grip portion 11 is mg, and the weight applied to the center of gravity of the main body portion 13 is Mg. The floor reaction force applied to the front wheel 15 is F ₁ , and the floor reaction force applied to the rear wheel 16 is F ₂ . The distance from the center of gravity of the grip portion 11 to the center of gravity of the main body 13 is L _arm , the distance from the center of gravity of the main body 13 to the center of the front wheel 15 is L _b , and the distance from the center of gravity of the main body 13 to the center of the rear wheel 16 is Let _Lb. In this case, the floor reaction force F ₁ can be obtained by Expression (7).

  The method for obtaining the floor reaction force applied to the front wheel 15 is not limited to the method shown in the equation (7). You may make it calculate the floor reaction force concerning the drive wheel 15 by kinematics and dynamics calculation from the state of the arm part 12, the holding part 11 including a conveyed product, and the autonomous moving mechanism 13. The floor reaction force applied to the front wheel 15 is at least one of the postures, speeds and accelerations of the links 124 and 125 of the arm unit 12 and at least one of the postures, speeds and accelerations of the transported object gripped by the gripping unit 11. From the above and at least one of the posture, speed, and acceleration of the main body 13, kinematics and / or dynamics may be calculated.

The correction table storage unit 18 stores a correction table 181.
FIG. 4 is a diagram showing the correction table 181. The correction table 181 records the floor reaction force F ₁ received by the front wheel 15 that is the driving wheel, and the slip ratios a _l and a _r and the slip angle α of the left and right wheels as the correction coefficient in association with each other. .

The correction table 181 stores, for example, a correction coefficient obtained by measuring a position when the mobile device 1 is actually moved.
FIG. 5 is a diagram showing a configuration when a correction table is created. First, a motion capture 20 that receives reflected light from a reflective marker is installed on a ceiling parallel to the floor. The reflective markers 21 and 22 are installed on the upper surface of the main body 13. As for the main-body part 13, the weight 23 is mounted in the upper surface of the main-body part 13 instead of the weight of a conveyed product, the holding part 11, and the arm part 12. FIG.

  The correction parameter calculation process will be described. First, the floor reaction force applied to the front wheel 15 is calculated from the weight of the weight 23. Next, the main body 13 is caused to travel at the maximum speed and the maximum curvature assumed in the mobile device 1. Then, the dead reckoning value without correction and the true value that is the measurement value of motion capture are compared, the vertical slip amount and the side slip amount are calculated, the correction parameter is calculated, and stored in the correction table 181.

  When the value of the correction parameter is determined, the weight 23 is changed, that is, the floor reaction force applied to the front wheel 15 is changed, and the correction parameter calculation process is repeated. Thereby, the correction table 181 can be created.

  In the present embodiment, since the correction parameter is calculated from the measurement value of the motion capture 20, a more accurate correction coefficient can be set.

Based on the floor reaction force applied to the front wheel 15 calculated by the floor reaction force calculation unit 17, the position estimation unit 19 reads the slip ratios a _l and a _r and the slip angle α of the left and right wheels of the front wheel 15 from the correction table 181. The dead reckoning of the mobile device 1 is performed using the equations (4) to (6).

FIG. 6 is a flowchart showing the dead reckoning process of the mobile device 1 according to the present embodiment. First, the floor reaction force calculation unit 17 calculates the floor reaction force F ₁ using the equation (7) from each joint angle of the arm unit 12 and the weight of the transported object gripped by the grip unit 11 (step S1).

Next, referring to the correction table 181, based on the value of the floor reaction force F ₁ , the slip rates a _l and a _r and the slip angle α of the left and right wheels of the front wheel 15 that are correction coefficients are selected (step S <b _> 2). . Then, dead reckoning processing is performed using the correction coefficient selected in step S2 (step S3). Thereby, the correction coefficient according to the floor reaction force can be selected, and dead reckoning can be performed more accurately.

  The mobile device 1 according to the present embodiment includes a correction table 181 that records a correction coefficient corresponding to the floor reaction force applied to the front wheel 15, and performs dead reckoning using the correction coefficient corresponding to the floor reaction force. In addition, it is possible to perform position estimation in consideration of the amount of vertical slip and side slip of the front wheel 15.

  Further, in the mobile device 1 according to the present embodiment, since the slip amount is not measured, there is no need to provide a gyro sensor used for detecting the slip amount in the conventional mobile device, and the configuration can be simplified. can do.

  Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention. For example, in the above embodiment, the floor reaction force is estimated and calculated only from the balance of static forces, but the floor reaction force can be estimated more accurately by further calculating the dynamics during arm operation and the like. is there.

DESCRIPTION OF SYMBOLS 1 Mobile body apparatus 11 Grip part 12 Arm part 13 Main body part 14 Control part 15 Front wheel 16 Rear wheel 17 Floor reaction force calculation part 18 Correction table memory | storage part 181 Correction table 19 Position estimation part 20 Motion capture 21 Reflection marker 22 Reflection marker 23 Weight 121 Drive shaft 122 Drive shaft 123 Drive shaft 124 Link 125 Link 101 Wheel 102 Wheel 103 Crawler 104 Crawler 105 Main body

Claims (1)

A gripping part for gripping a conveyed product;
An autonomous movement mechanism with drive wheels;
An arm part connecting the grip part and the autonomous movement mechanism;
A correction table storage unit that stores a floor reaction force applied to the drive wheel and a correction coefficient for correcting the slip amount of the drive wheel in association with each other;
The floor reaction force applied to the drive wheel is calculated by kinematics and dynamics calculation from the states of the arm unit, the gripping unit including the transported object, and the autonomous moving mechanism, and the floor reaction force is calculated from the correction table storage unit. A position estimation processing unit that reads out a correction coefficient corresponding to the reaction force and performs position estimation processing by kinematics and dynamics calculation ;
A mobile device comprising:

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