JP2018026047A - Mobile device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that, in a travel device capable of performing all azimuthal movements, a velocity command value exceeds a capacity of the driving system and may show an operation different from the assumed operation.SOLUTION: A mobile device includes: a trolley having a driving wheel and a follower wheel; a cargo bed mounted on the trolley; a pivot driver for pivotally driving the cargo bed for the trolley; and a control part. The control part converts a velocity command value given as a first velocity and a second velocity in a travel surface direction, and an angular velocity around an orthogonal axis into a first drive angular velocity, a second drive angular velocity which are rotational angular velocity of two driving wheels respectively, and a rotation angular velocity of the pivot driver. When any of these angular velocities exceed the driving capacity, these angular velocities are modified so as to be accommodated within the driving capacity without changing the mutual ratio of the first velocity, the second velocity and the angular velocity given as the velocity command value, then the two driving wheels and the pivot driver are controlled.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a mobile device.

  2. Description of the Related Art An omnidirectional vehicle having a pair of driving wheels and driven wheels on a cart is known. For example, according to Patent Document 1, an omnidirectional vehicle is applied to an electric wheelchair, and the vehicle body can be moved in any direction without changing the posture of the seating portion.

Japanese Patent Laid-Open No. 2007-152019

Even if a moving vehicle has a mechanism that can move in all directions, the speed command value generated to realize the movement exceeds the capacity of the drive system, and may show an operation different from the expected operation. there were. In addition, if the speed command value generated based on the drive system capability is limited, it may operate only at a very low speed.
The present invention has been made to solve such problems, and provides a technique for realizing omnidirectional movement which is safe and suppresses a decrease in speed.

  A moving device according to an aspect of the present invention includes a cart unit having two drive wheels and at least one driven wheel that are rotationally driven independently of each other, a cargo bed unit that is rotatably mounted on the cart unit, A turning drive unit for turning the cargo bed unit with respect to the carriage unit, and a control unit for controlling the two drive wheels and the turning drive unit, wherein the control unit has a first speed in the first axial direction of the traveling surface direction, A speed command value given as a second speed in the second axis direction different from the first axis in the traveling plane direction and an angular velocity for the traveling plane around the third axis orthogonal to the first axis and the second axis is 2 The first driving angular velocity, the second driving angular velocity, and the turning angular velocity of the turning drive unit, which are rotational angular velocities of the two driving wheels, are converted into at least one of the converted first driving angular velocity, second driving angular velocity, and turning angular velocity. But two drive wheels and When exceeding the drive capability of the turning drive unit, the first drive angular velocity, so that each of them falls within the drive capability without changing the ratio of the first speed, the second speed, and the angular velocity in the speed command value, The second driving angular velocity and the turning angular velocity are corrected to control the two driving wheels and the turning drive unit.

  With such control, the omnidirectional movement can be performed at high speed and safely without moving the driving system in an operating posture similar to that assumed by the original speed command value without excessively limiting the driving capability of the driving system. Can be realized.

  According to the present invention, it is possible to provide a mobile device that realizes safe and high-speed omnidirectional movement.

It is an external appearance perspective view which decomposes | disassembles and shows a part of mobile robot which concerns on this embodiment. It is a control block diagram of a mobile robot. It is explanatory drawing explaining omnidirectional movement control. It is explanatory drawing explaining the concept which corrects the angular velocity of a drive system. It is a functional block diagram which shows the flow of control.

  Hereinafter, the present invention will be described through embodiments of the invention, but the invention according to the claims is not limited to the following embodiments. In addition, all of the configurations described in the embodiments are not necessarily essential as means for solving the problem.

  FIG. 1 is an external perspective view showing a part of the mobile robot 100 according to this embodiment in an exploded manner. A mobile robot 100 as an example of a mobile device is roughly composed of a cart unit 110 and a cargo bed unit 120. The figure shows a state where the loading platform 120 is slightly lifted from the cart 110.

  The carriage unit 110 is mainly composed of a carriage base 111 having a substantially rectangular shape when observed from above, two drive wheels 112 attached to the carriage base 111, and one caster 113. The carriage base 111 serves as a base of the carriage unit 110 and has, for example, a frame structure. The two drive wheels 112 are disposed on opposite sides of the carriage base 111 so that the rotation axis centers coincide with each other. Each drive wheel 112 is rotationally driven independently by a motor (not shown). The caster 113 is a driven wheel, and a turning shaft extending in the vertical direction from the carriage base 111 is provided so as to support the wheel away from the rotation axis of the wheel, and follows the movement direction of the carriage unit 110. Functions as a follower caster. The mobile robot 100, for example, goes straight if the two drive wheels 112 are rotated in the same direction at the same rotational speed, and turns around the vertical axis passing through the center of gravity if rotated in the opposite direction at the same rotational speed. That is, the mobile robot 100 can move forward, backward, and turn by controlling the rotational direction and rotational speed of the two drive wheels 112.

  The cart unit 110 is provided with various sensors for obstacle detection and surrounding environment recognition. The camera 114 is one of the sensors, and is disposed at the four corners of the carriage base 111. The camera 114 includes, for example, a CMOS image sensor, and transmits a captured image signal to a control unit described later. If two adjacent cameras 114 capture the same obstacle, a parallax image can be acquired, and the distance to the obstacle can also be calculated. Also, the size of the obstacle can be calculated using the ratio of the obstacle to the angle of view and the calculated distance.

  A turning mechanism 119 is provided at the center of the upper surface of the carriage base 111. A meshing portion (not shown) of the upper body base 125 constituting the loading platform 120 is fitted into the turning mechanism 119, and the upper body base 125 is placed on the carriage base 111. The upper body base 125 is swiveled around a vertical axis via a swivel mechanism 119 by a motor (not shown) provided on the carriage base 111.

  The loading platform 120 mainly includes a plurality of arms 121 and a hand 124 in addition to the upper body base 125. The plurality of arms 121 are connected to each other so as to rotate at their respective ends. The base end side of the series of arms 121 is fixed to the upper body base 125, and the distal end side rotatably supports the hand 124. The hand 124 includes a gripping mechanism so that the transported object can be gripped. The arm 121 and the hand 124 are driven via a motor (not shown) and take a predetermined posture or grip a conveyed product.

  FIG. 2 is a control block diagram of the mobile robot 100. The control unit 200 is a CPU, for example, and is provided in the cart unit 110. The drive wheel unit 210 includes a drive circuit and a motor for driving the drive wheels 112 and is provided in the carriage unit 110. The control unit 200 performs rotation control of the drive wheel 112 by sending a drive signal to the drive wheel unit 210. Specific drive signals will be described later in detail.

  The turning drive unit 212 includes a drive circuit and a motor for driving the upper body base 125 to turn, and is provided in the carriage unit 110. The control unit 200 performs turning control of the upper body base 125 by sending a drive signal to the turning drive unit 212. Note that when the upper body base 125 is turned, the entire loading platform 120 is turned around the vertical axis, including the conveyed product held by the hand 124. In addition, when the cart unit 110 turns with respect to the road surface by driving the drive wheels 112, if the control unit 200 synchronizes with the turning of the cart unit 110 and turns the body base 125 in the opposite direction, The entire loading platform 120 apparently does not rotate around the vertical axis with respect to the road surface, and can maintain its posture relatively. Specific drive signals will be described later in detail.

  The arm unit 220 includes a drive circuit and a motor for driving the arm 121 and the hand 124, and is provided on the loading platform 120. The control unit 200 performs posture control and gripping control of the loading platform 120 by sending a drive signal to the arm unit 220.

  The sensor unit 230 includes various sensors for searching the surrounding environment and monitoring the attitude of the loading platform 120, and is distributed in the cart 110 and the loading platform 120. The control unit 200 sends various control signals to the sensor unit 230 to drive various sensors and acquire their outputs. The camera 114 is included in the sensor unit 230 and executes a shooting operation according to a control signal.

  The memory 240 is a non-volatile storage medium, and for example, a solid state drive is used. In addition to the control program for controlling the mobile robot 100, the memory 240 stores various parameter values, functions, lookup tables, and the like used for control. The memory 240 includes an environment map DB 241 that stores an environment map representing an environment in which the mobile robot 100 travels autonomously.

  The control unit 200 functions as a function calculation unit that performs various calculations related to control by transmitting and receiving information to and from the drive wheel unit 210, the turning drive unit 212, the arm unit 220, the sensor unit 230, and the memory 240. Also plays a role. The mobile robot 100 autonomously moves to the target position along the planned movement route, or moves while avoiding the obstacle autonomously while being given a moving direction as appropriate by the user. At this time, the mobile robot 100 generates a speed command for traveling along a planned movement route or for avoiding an obstacle captured by the camera 114.

  Next, the omnidirectional movement control of the mobile robot 100 will be described. The mobile robot 100 performs omnidirectional movement control that can move the cart unit 110 in all directions while maintaining the posture of the loading platform 120. FIG. 3 is a diagram for explaining the omnidirectional movement control. As shown in the figure, when the caster 113 is the front side, the right driving wheel is the right driving wheel 112a, and the left driving wheel is the left driving wheel 112b. In addition, the x axis is the first axis direction in the traveling plane direction, the y axis is the second axis direction that is the traveling plane direction direction and orthogonal to the x axis, and the third axis that is orthogonal to the x axis and the y axis is z. Determined as the axis. The example of the figure represents a state in which the upper body base 125 that is driven to turn in the loading platform 120 is oriented in the plus direction of the x axis (the turning angle θ with respect to the traveling surface around the z axis is 0 degree).

As shown in the figure, the angular velocity of the right driving wheel 112a is ω _R , the angular velocity of the left driving wheel 112b is ω _L , each radius is r (same), and the distance (tread) between the right driving wheel 112a and the left driving wheel 112b is W. The offset amount between the turning center and the drive wheel axle is s, the turning angle between the body base 125 and the carriage base 111 is θ _v , and the turning angular velocity of the body base 125 with respect to the carriage base 111 is ω _S.

  At this time, when the speed in the x-axis direction with respect to the traveling surface is represented by x dots, the speed in the y-axis direction with respect to the traveling surface is represented by y dots, and the angular velocity around the z-axis with respect to the traveling surface is represented by θ dots, the following relational expression (1) is obtained. To establish.

Here, although the transformation matrix J is a function of _θv , the inverse matrix J ⁻¹ can be calculated regardless of the value of this angle. From this, it can be seen that there is no singular point in this control, and forward and backward calculations are always possible. That is, it can be seen that the omnidirectional movement control is holonomic control.

The control unit 200 determines a target position to move next based on the environmental map acquired from the environmental map DB 241 and the acquired obstacle information. In order to move to the target position, a speed command value is generated in consideration of the current position and posture of the carriage unit 110. This speed command value is the above x dot, y dot, and θ dot. However, since the drive system of the mobile robot 100 is the right drive wheel 112a, the left drive wheel 112b, and the turning mechanism 119, the control unit 200 sends speed command values to these drive systems in order to actually drive the drive system. It is necessary to convert to each angular velocity. The conversion matrix for that is J ⁻¹ , and the angular velocities of the drive system obtained by the conversion are ω _R , ω _L , and ω _S described above.

The control unit 200 calculates the angular velocities (ω _R , ω _L , ω _S ) of the drive system using the target position to be moved as an initial value, but the drive capability of each motor of the drive system is limited. If the angular velocity exceeds the limit of the driving capability, the assumed control cannot be executed. If the control is performed as it is, the carriage unit 110 may deviate from the assumed route, or the loading unit 120 may not assume the posture. As a result, a part of the mobile robot 100 or a part of the grasped transported object may collide with a wall surface of the route or an obstacle. On the other hand, assuming all situations of omnidirectional movement, if the maximum value of the speed command value (x dot, y dot, θ dot) is limited in advance from the driving ability of each motor, it can move only at extremely low speed Can occur.

Therefore, the control unit 200 of the mobile robot 100 according to the present embodiment is such that at least one of the angular speeds (ω _R , ω _L , ω _S ) of the drive system converted from the speed command value is the right drive wheel 112a, the left drive wheel. 112b and the driving capability (ω _{R_MAX} , ω _{L_MAX} , ω _{S_MAX} ) of the turning mechanism 119, respectively, without changing the mutual ratio of the speed command values (x dots, y dots, θ dots) The angular velocities (ω _R , ω _L , ω _S ) are corrected so as to be within the driving capability, and the right driving wheel 112a, the left driving wheel 112b, and the turning mechanism 119 are controlled. This correction calculation will be described. FIG. 4 is an explanatory diagram for explaining the concept of correcting the angular velocity of the drive system converted from the speed command value. FIG. 4 represents the angular velocities (ω _R , ω _L , ω _S ) of the right driving wheel 112a, the left driving wheel 112b, and the turning mechanism 119 as a three-dimensional space, and the driving ability (ω _{R_MAX} , ω _{L_MAX} , _{ωS_MAX} ) are plotted.
When the speed command value is represented as a vector v in Expression (2), the vector ω of angular velocities (ω _R , ω _L , ω _S ) converted using the relational expression (1) is expressed in Expression (3). .

Here, the control unit 200 determines whether each of the converted (ω _R , ω _L , ω _S ) exceeds any one of the corresponding driving capabilities (ω _{R_MAX} , ω _{L_MAX} , ω _{S_MAX} ). Determine whether. If neither exceeds, the control unit 200 performs drive control with the vector ω. If any one exceeds, perform the following correction operation. A vector ω represented by a thick line in FIG. 4 shows an example in which ω _S exceeds ω _{S_MAX} .

The norm τ _d of the speed command value is expressed by Expression (4). When the vector of the speed command is converted into a unit vector using the norm τ _d , Expression (5) is obtained.

The speed safety coefficients for the driving ability (ω _{R_MAX} , ω _{L_MAX} , ω _{S_MAX} ) of the right driving wheel 112a, the left driving wheel 112b, and the turning mechanism 119 are τ _R , τ _L , and τ _S , respectively. Define.

そして、以下の式（７）により、速度安全係数の最小値をτ_ＳＡＦＥと定める。

And the minimum value of the speed safety coefficient is defined as τ _SAFE by the following equation (7).

すると、右駆動輪１１２ａ、左駆動輪１１２ｂ、および旋回機構１１９の修正された角速度（ベクトルω_ＳＡＦＥ）は、以下の式（８）により算出される。

Then, the corrected angular velocity (vector ω _SAFE ) of the right driving wheel 112a, the left driving wheel 112b, and the turning mechanism 119 is calculated by the following equation (8).

When such a correction operation is geometrically represented in the three-dimensional space of FIG. 4, in the example of the vector ω represented by a bold line, the vector ω has exceeded the driving capability so as not to change its direction. _The length is shortened until the component of _S becomes ω _{S_MAX} equal to the driving capability. According to such a correction calculation, since at least one component becomes the maximum value of the driving capability, the movement of the mobile robot 100 is not significantly reduced. Further, the ratio of each component of the vector ω _SAFE is equal to the ratio of each component of the vector ω calculated initially, that is, the ratio of each component of the speed command value (x dot, y dot, θ dot) is also maintained. Therefore, the operation of the mobile robot 100 controlled by ω _SAFE is only slightly slower than the assumed operation. In other words, except for the moving speed, it can be said that the robot moves in the same operating posture as that assumed by the original speed command value. Therefore, it is possible to reduce the possibility of deviating from the assumed route or colliding with an obstacle.

In the above description, (ω _R , ω _L , ω _S ) is once calculated, and the correction calculation is executed after determining whether these _exceed the driving ability (ω _{R_MAX} , ω _{L_MAX} , ω _{S_MAX} ). However, this judgment can be omitted. Specifically, the minimum value τ _SAFE of the speed safety coefficient is determined by the following equation (9) including τ _d as a target.

In this case, if all of (ω _R , ω _L , ω _S ) are lower than the corresponding (ω _{R_MAX} , ω _{L_MAX} , ω _{S_MAX} ), τ _d is selected as τ _SAFE , and the equation (8) The vector ω _SAFE calculated by is eventually equal to the vector ω.

  When the above control is expressed by input / output of parameters to the functional block, it is expressed as shown in FIG. FIG. 5 is a functional block diagram showing the flow of control.

The control unit 200 mainly functions as a speed command generator 201 and a converter 202. When the speed command generator 201 acquires the target position and the attitude of the carriage unit 110, the speed command generator 201 generates a vector v as a speed command of the cargo bed unit 120 with respect to the traveling surface. The converter 202 acquires the vector v from the speed command generator 201 and also acquires the maximum angular speed (ω _{R_MAX} , ω _{L_MAX} , ω _{S_MAX} ) as the driving capability of each motor. The maximum angular velocities (ω _{R_MAX} , ω _{L_MAX} , ω _{S_MAX} ) are stored in the memory 240.

Moreover, the converter 202 acquires the angle θ _v of the loading platform 120 with respect to the current carriage unit 110 and the angle θ of the loading platform 120 with respect to the traveling surface from the turning drive unit 212. The converter 202 performs the above-described calculation based on the acquired information, and generates a vector ω _SAFE as an angular velocity command. Then, to the drive wheels unit 210 ω _{R_SAFE,} it sends omega _{L_SAFE} as a command signal, is to pivot the drive unit 212 to transmit a command signal ω _{S_SAFE.} When the correction calculation is not performed by the converter 202, the vector ω is adopted as the angular velocity command, ω _R and ω _L are transmitted as command signals to the drive wheel unit 210, and ω _S to the turning drive unit 212. Is transmitted as a command signal.

  In the above embodiment, the mobile robot 100 has been described as an example. However, the speed control described above can be applied to various mobile devices other than the mobile robot. For example, when the present invention is applied to an electric wheelchair in which a seat is provided in the loading platform, it can be applied to speed control that moves toward the position or direction instructed by the passenger without changing the orientation of the chair.

  Further, the definition of the coordinate system is not limited to the example described above. A three-dimensional space may be appropriately defined according to the environment in which the mobile device is used. For example, the x axis and the y axis defined in the traveling surface direction do not have to be orthogonal to each other.

  Moreover, the form of a follower caster is not restricted to the example mentioned above. As long as it is a driven wheel, it may be an omni wheel, a mecanum wheel, a ball caster, or the like. Moreover, the protrusion etc. which were formed with the low friction member etc. which contact a running surface and support the load of a part of moving apparatus may be sufficient.

DESCRIPTION OF SYMBOLS 100 Mobile robot, 110 trolley part, 111 trolley base, 112 drive wheel, 113 caster, 114 camera, 119 turning mechanism, 120 cargo bed part, 121 arm, 124 hand, 125 upper body base, 200 control part, 201 speed command generator , 202 converter, 210 drive wheel unit, 212 turning drive unit, 220 arm unit, 230 sensor unit, 240 memory, 241 environment map DB

Claims (1)

A carriage unit having two drive wheels and at least one driven wheel that are driven to rotate independently of each other;
A loading platform that is turnably mounted with respect to the cart,
A turning drive unit for turning the cargo bed unit with respect to the carriage unit;
A control unit for controlling the two drive wheels and the turning drive unit,
The controller is
A first speed in the first axis direction of the traveling surface direction, a second speed in the traveling surface direction and a second axis direction different from the first axis, and a first speed orthogonal to the first axis and the second axis. Converting a speed command value given as an angular speed with respect to a traveling surface around three axes into a first driving angular speed, a second driving angular speed, and a turning angular speed of the turning drive unit, which are rotational angular speeds of the two driving wheels,
When at least one of the converted first driving angular velocity, the second driving angular velocity, and the turning angular velocity exceeds the driving ability of the two driving wheels and the turning drive unit, the speed command value The first driving angular velocity, the second driving angular velocity, and the turning angular velocity are corrected so that they are within the driving capability without changing the ratio of the first speed, the second speed, and the angular speed. A moving device that controls the two drive wheels and the turning drive unit.

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