JP4264399B2 - Automated guided vehicle - Google Patents

Description

  The present invention relates to an automatic guided vehicle that steers front wheels and rear wheels and is driven to travel along a travel line set in advance on a road surface, and more particularly to an automatic guided vehicle that has improved follow-up controllability.

In a site such as a factory, an automatic guided vehicle that automatically travels along a travel line set in advance on a road surface has attracted attention as a means for realizing labor saving of transport work for heavy objects.
This type of automated guided vehicle includes, for example, a travel distance sensor, a steering angle sensor, and an attitude angle sensor (gyro). From the travel position data of the own vehicle detected by each of these sensors and the travel line data, A target posture angle for traveling along the traveling line is obtained to perform steering control. At this time, until the calculated target posture angle is reached, steering angle control is performed by obtaining a posture angle command in which the angle gradually changes for each predetermined travel distance, thereby realizing stable traveling regardless of the loaded weight. Has been proposed (see, for example, Patent Document 1).

In addition, a magnetic derivative is previously laid on the road surface as a travel line (magnetic line), and the travel line (magnetic derivative) is detected by a magnetic sensor provided in the automatic guided vehicle, and a deviation amount (deviation) from the travel line. It is also proposed that the automatic guided vehicle automatically travels along the travel line by steering control based on the amount of deviation and the attitude of the vehicle body (the direction of the vehicle) detected using a gyroscope or the like. (See, for example, Patent Document 2).
JP 2003-22132 A JP 2002-351545 A

By the way, the automatic guided vehicle capable of steering the front wheels and the rear wheels can travel in various ways by independently controlling the steering angle on the front wheel side and the steering angle on the rear wheel side. However, it cannot be denied that the steering control is complicated. For example, when reverse steering angles δ _f and δ _r are given to the front wheels and the rear wheels, the automatic guided vehicle turns at a turning radius defined by the sum of these steering angles δ _f and δ _r . When the steering angles δ _f , δ _r in the same direction are given to the front wheels and the rear wheels, the automatic guided vehicle turns at a turning radius defined by the difference between these steering angles δ _f , δ _r , and laterally A displacement in the direction also occurs. In particular, when the same steering angles δ _f and δ _r are given to the front wheels and the rear wheels in the same direction, the automatic guided vehicle travels obliquely while maintaining its posture without turning.

  Therefore, in order for the automatic guided vehicle to travel along the above-described traveling line, considering the behavior of the vehicle body described above, for example, the amount of deviation of the automatic guided vehicle from the traveling line, the direction with respect to the traveling line, and further It is necessary to optimally steer the front and rear wheels according to the traveling speed. Specifically, for example, after determining the steering angle of the front wheels according to the deviation amount (lateral deviation) of the vehicle body with respect to the travel line, the steering angle of the front wheels is taken into account according to the attitude of the vehicle body (yaw angle deviation) However, complicated control such as determining the steering angle of the rear wheels is required.

  The present invention has been made in consideration of such circumstances, and its purpose is an automatic guided vehicle that can travel with good followability along a travel line set in advance on a road surface without requiring complicated control. Is to provide.

In order to achieve the above-described object, the automatic guided vehicle according to the present invention is configured such that the vehicle main body is designated along a traveling line set in advance on a road surface while steering front wheels and rear wheels provided on the vehicle main body. been made to travel driven at the target speed,
(a) A sensor mounted on the vehicle main body for detecting a traveling speed V of the vehicle main body, and a sensor mounted on the front wheel side and the rear wheel side of the vehicle main body on the side of the front wheel side of the vehicle main body with respect to the travel line. a sensor for determining the respective lateral deviation amount e _r rear wheel side in the direction of the deviation amount e _f and the vehicle body, the vehicle relative to the traveling line each lateral deviation amount e _f, based on the e _r Detection means for respectively obtaining a lateral deviation y _e indicating the lateral deviation amount of the main body and a yaw angle deviation φ _e indicating a deviation angle of the direction of the vehicle main body with respect to the direction of the travel line ;
(b) the traveling line of the vehicle body by a projection operation to said detected lateral deviation y _e and the running line on the running speed V of the vehicle body based on the yaw angle difference phi _e by the detecting means Projection means for determining the moving speed V _L above,
(c) the longitudinal direction deviation x _e of the said vehicle body in the traveling line direction from the difference between the integral value of the moving velocity V _L of the integrated value of the designated the target speed u _d and the vehicle body relative to the vehicle body Distance difference detecting means for obtaining
(d) lateral deviation y _e of the vehicle _body, yaw angle difference phi _e, on the basis of the longitudinal direction deviation x _e, and said target speed u _d, the vehicle body to the traveling line according to the preset calculation formula a command value calculating means for calculating each traveling speed command value u _r, the rotation speed command value gamma _r, and the traverse speed command value [nu _r required to travel at the target speed u _d along,
(e) when the traveling speed command value said to speed control of the vehicle body on the basis of u _r, phase between the front and rear wheels necessary to obtain the transverse velocity of the vehicle body indicated by the traverse speed instruction value [nu _r Steering angle component δ _p of the vehicle body, and a steering angle component δ _y of the reverse phase between the front and rear wheels necessary for obtaining the turning speed γ of the vehicle body indicated by the turning speed command value γ _r , The steering angles δ _f and δ _r of the front and rear wheels are determined according to the steering angle components δ _p and δ _y of
δ _r = 0.5 δ _p + δ _y
δ _r = −0.5 δ _p + δ _y
And steering control means for steering the front wheels and the rear wheels, respectively .

Preferably, when the travel line is a magnetic line laid on the road surface, a lateral deviation y _e and a yaw angle deviation φ _e of the vehicle body are a pair of front and rear line type magnetic sensors provided on the vehicle body. the width direction of the deviation amount e _f from the magnetic lines in the front wheel side and rear wheel side of the vehicle body, configured to determine from each e _r detected respectively by (claim 2). Also, the projection means, the running speed V _L of the vehicle body on the running line on the basis of the running speed V and the yaw angle difference phi _e of the vehicle body
V _L = V · cosφ _e
As or when said vehicle turning speed of the body γ is demanded, and a running speed V and the lateral deviation y _e of the vehicle body
V _L = V−y _e · γ
As described above, the moving speed V _L of the vehicle main body on the travel line is obtained .

Further, the steering control means includes a traversing speed estimating means for estimating a traverse speed ν of the vehicle body toward the traveling line from a change in the lateral deviation y _e, the vehicle determined from the steering angle of the front wheels and rear wheels and a turning speed estimating means for estimating a turning radius R ₀ and the turning speed of said vehicle body and a running speed V of the vehicle body γ of the main body, the transverse velocity traverse speed ν and estimated by said traverse speed estimating unit The first steering angle δ _y with the difference from the command value ν _r as [0] is obtained, and the difference between the turning speed γ estimated by the turning speed estimation means and the turning speed command value γ _r is determined as [0]. determine a second steering angle [delta] _p to, these first and second steering angle [delta] _y, the steering angle of the front wheels and rear wheels from [delta] _p [delta] _f, is configured to determine [delta] _r (Claim 4).

Preferably, the calculation means for obtaining the first and second steering angles δ _y and δ _p respectively controls the first and second steering angles δ _y and δ _p according to the traveling speed V of the vehicle body. The gain is changed, and particularly when the traveling speed V of the vehicle body is equal to or less than a preset constant traveling speed V ₀ , the first and second steering angles are set under a certain control gain. δ _y and δ _p are obtained, respectively, and when the traveling speed V of the vehicle body exceeds the constant traveling speed V ₀ , the control unit is set under a control gain that is set to be smaller as the traveling speed V increases. The first and second steering angles δ _y and δ _p are obtained respectively (Claim 5).

That is, the automatic guided vehicle according to the present invention has a lateral deviation y _e and a yaw angle deviation φ _e with respect to the travel line of the vehicle body, and a travel speed V of the vehicle body, as shown in FIG. Each of them is detected (detection means a), and the traveling speed V of the vehicle body is projected onto the traveling line based on the lateral deviation y _e and the yaw angle deviation φ _e, and the traveling speed V of the vehicle body is projected on the traveling line. with obtaining the moving speed of the (projection means b), determining the longitudinal direction deviation x _e from the difference between the integrated value of the integrated value and the target speed u _d of the moving speed in the traveling line direction of the vehicle body (distance difference detection Means c).

The lateral deviation y _e , the yaw angle deviation φ _e , the longitudinal deviation x _e obtained as described above, and the target travel speed u _d for the vehicle body are used for the follow-up travel for the travel line. traveling control command value of the vehicle body, traveling in particular the speed command value u _r, turning speed value gamma _r, and the traverse speed command value [nu _r, for example, _{u r = u d · cosφ e} + K x · x e
ν _r = K _y · u _d · y _e
γ _r = K _p · u _d · sinφ _e
However, K _x , K _y , and K _p are uniquely obtained as positive control gains (command value calculation means d).

Then, the transverse speed of the vehicle body with respect to the travel line is estimated from the lateral deviation y _{e (} cruising speed estimation means e), and the front wheel and the rear wheel are determined from the estimated transverse speed and the turning speed γ of the vehicle body. It is characterized in that the steering angles δ _f and δ _r of the wheels are determined (steering control means f).
Note that the turning speed γ of the vehicle body is estimated from the turning radius R _{0 of the} vehicle body obtained from the steering angles of the front wheels and the rear wheels and the traveling speed V of the vehicle body (turning speed estimation means g). You can do that. When the steering angles δ _f and δ _r are determined from the traverse speed and the turning speed γ, for example, the first steering angle δ _y with the difference between the traverse speed and the traverse speed command value ν _r as [0] is set to [0]. determined with (first arithmetic means h), the difference between the turning speed gamma and the rotation speed command value gamma _r seek second steering angle [delta] _p to [0] (second arithmetic means i), these From the first and second steering angles δ _y and δφ, the steering angles δ _f and δ _r of the front and rear wheels are
δ _f = 0.5 δ _p + δ _y , δ _r = −0.5 δ _p + δ _y
As long as they are required. And each of these steering angle [delta] _f, as well as steer the front wheels and rear wheels respectively according to [delta] _r, in accordance with the traveling speed command value u _r may be to control the running speed V of the vehicle body.

According to the automatic guided vehicle having the above-described configuration, the lateral deviation y _e , the yaw angle deviation φ _e , and the longitudinal deviation x _e with respect to the travel line of the vehicle main body are obtained, according to the target travel speed u _d with respect to the vehicle main body. The traveling speed command value u _r , the turning speed command value γ _r , and the transverse speed command value ν _r for the traveling line that are necessary for the traveling control of the vehicle body can be calculated together. In addition, according to the lateral speed and the turning speed estimated from the behavior of the vehicle body, a lateral displacement control system and a turning control in which the deviations from the transverse speed command value ν _r and the turning speed command value γ _r are set to [0], respectively. By simply determining the steering angles δ _f and δ _r of the front and rear wheels that can satisfy these control systems, a stable follow-up control of the vehicle body along the travel line is possible. It becomes.

  Therefore, there is no need to determine the steering angle and the steering direction of the front wheels and the rear wheels while dividing the case according to the positional relationship with the travel line of the vehicle body and the behavior thereof as in the prior art. Simplification can be achieved. In particular, after determining the steering angle of the front wheels according to, for example, the amount of deviation (lateral deviation) of the vehicle body from the travel line, the rear wheel while taking into account the steering angle of the front wheels according to the attitude of the vehicle body (yaw angle deviation) There are practically significant effects such as no inconvenience of determining the steering angle of the wheel.

Hereinafter, a four-wheel steering equipped with a pair of left and right front wheels W _FL , W _FR and a pair of left and right rear wheels W _RL , W _{RR so as} to be steerable for an automatic guided vehicle according to an embodiment of the present invention with reference to the drawings. A type vehicle will be described as an example.
In addition, there is a so-called multi-shaft wheel type vehicle in which front wheels and / or rear wheels are arranged in tandem in the front-rear direction of heavy vehicles for conveying heavy objects. However, since the wheels arranged in tandem can be equivalently regarded as one wheel (one axis), it will be described here as a four-wheel steering type vehicle including a multi-axis wheel type vehicle. The pair of left and right front wheels W _FL and W _FR and / or the pair of left and right rear wheels W _RL and W _RR may be realized as a so-called double tire in which a plurality of wheels are coaxially mounted on the axle. These multiple mounted wheels can also be regarded as one wheel equivalently, and therefore, here, the multiple wheels mounted will be described as front wheels and rear wheels.

As shown in FIG. 2, the automatic guided vehicle includes a pair of left and right front wheels W _FL and W _FR and a pair of left and right rear wheels W _RL and W _RR before and after the vehicle body 1. The motor is driven by using a motor (electric motor) driven by a battery as a power source, and is configured to automatically travel along a preset travel line L in a site such as a factory. In particular, the wheels W _FL , W _FR , W _RL , and W _RR are basically driven to run under the control of the rotational speed under the control of the speed control unit 2, and under the control of the steering control unit 3. Each steering angle is controlled.

Incidentally, the travel line L is realized as a white line drawn in advance on the road surface or a magnetic line formed by a plurality of magnetic elements laid on the road surface. The automatic guided vehicle uses a pair of front and rear sensors 4 _f and 4 _r provided on the front wheel side and the rear wheel side of the vehicle main body 1 in the width direction of the vehicle main body 1 with respect to the travel line L as will be described later. The shift amount e is detected, and the traveling speed and the steering angle are controlled so that the own vehicle (vehicle main body) is positioned on the traveling line L based on the detection results.

Specifically, each of the sensors 4 _f and 4 _r includes a plurality of magnetic sensing elements that detect the magnetic force from the magnetic line L as shown in FIG. 3, for example, when the travel line L is formed as a magnetic line. This is realized as a line type magnetic sensor array arranged linearly at a predetermined pitch p in the width direction of the vehicle body 1. Each of these sensors 4 _f and 4 _r determines on which position of the sensor array in the sensor array the magnetic force from the travel line L can be detected on the front wheel side and the rear wheel side of the vehicle body 1. Thus, the vehicle body 1 plays a role of detecting a lateral shift amount e from the travel line L. The lateral shift amount e _f, e _r from the running line L in the front-wheel side and rear wheel side of the vehicle body 1 respectively detected by each of these line sensors 4 _f, 4 _r is mainly composed of a microcomputer or the like It is input to the traveling control unit 5 and used for the rotational speed control and steering angle control of the wheels W _FL , W _FR , W _RL , W _RR described above.
<Overall configuration of control system>
FIG. 4 shows an overall control system configuration of the unmanned traveling vehicle constructed by the traveling control unit 5.

The travel control unit (control system) 5 shift amount e _f from the running line L in the front-wheel side and rear wheel side of the vehicle body 1 respectively detected by each of the line sensors 4 _f, 4 _r, according to e _r A sensor processing unit 10 is provided for determining a lateral deviation (lateral deviation amount) y _e and a yaw angle deviation (direction deviation angle) φ _e of the vehicle body 1 with respect to the travel line L. Also the travel control unit (control system) 5, moves from said vehicle running speed (actual speed) detected from the body 1 V and the target speed u _d for said vehicle body 1 of the vehicle body 1 in the traveling on the line L obtain a speed V _L, it comprises a dead-reckoning processor 20 for monitoring the further movement distance along from the moving speed to the travel line L of the vehicle body 1. The sensor processing unit 10 and the dead reckoning processing unit 20 implement the detection means a, projection means b, and distance difference detection means c in the present invention described with reference to FIG.

The control system (cruise control unit 5) is the lateral difference y _e determined as described above, the orientation deviation (the yaw angle deviation) phi _e, and in accordance with the target speed u _d, required for the driving control following the running line L comprising a trajectory tracking speed command generator 30 for determining the a Do traveling speed command u _r a turning velocity command gamma _r. The trajectory tracking speed command generator 30 corresponds to the command value calculation means d described above. In particular, in the trajectory following speed command generator 30, the turning speed command γ _r is divided into a transverse component ν and a turning component γ, so that the control command value is _{expressed as} ur = u _d · cos φ _e + K _x · x _e
ν _r = K _y · u _d · y _e
γ _r = K _p · u _d · sinφ _e
It is comprised so that each may be calculated | required collectively.

In addition the control system (cruise control unit 5), the control command value u _r of the trajectory tracking speed command generator 30 described above is generated, [nu _r, gamma _r in accordance, in particular satisfy the control command value [nu _r, the gamma _r simultaneously steering command value [delta] _y to obtain the [delta] _p, respectively, provided with a speed controller 40 further determines these steering command [delta] _y, the steering angle [delta] _f for the front and rear wheels satisfy the [delta] _p at the same time, [delta] _r, respectively. And this speed controller 40 outputs the speed control command value u _r mentioned above the speed control unit 2 described above as a motor command to control the running speed V of the vehicle body 1, the steering angle [delta] _f determined as described above , δ _r are output to the steering control unit 3 described above.

Incorporated into the vehicle body 1 speed controller 2 consisting of an inverter device for controlling the rotational speed of the motor, it controls the travel speed V of the vehicle body 1 in accordance with the speed control command value u _r. The steering control unit 3 that drives a cylinder that is incorporated in the vehicle body 1 and determines the steering angle of each wheel steers the front wheels and the rear wheels according to the steering angles δ _f and δ _r . The speed control unit 2 and the steering control unit 3 cooperate to realize automatic follow-up travel along the travel line L of the vehicle body 1.

Next, the estimation process of the vehicle posture (lateral deviation y _e , yaw angle deviation φ _e ) in the sensor processing unit 10 in the control system described above, and the movement distance (movement speed V _L ) in the dead reckoning processing unit 20 are described. The estimation processing, the generation processing of the speed control command values u _r , ν _r , γ _{r in} the trajectory following speed command generator 30 and the determination processing of the steering angles δ _f , δ _{r in} the speed controller 40 are specifically described. Explained.
<Vehicle attitude estimation processing>
The pair of front and rear sensors 4 _f and 4 _r provided on the vehicle body 1 is composed of a plurality of magnetic sensing elements arranged linearly at a predetermined pitch p in the width direction of the vehicle body 1 as described above. Of these magnetic sensing elements, only the magnetic sensing element positioned at a portion facing the traveling line (magnetic line) L as shown in FIG. 3 receives the magnetic force from the traveling line L and changes its output. . Therefore, if each output of the plurality of magnetic sensing elements constituting the sensors 4 _f and 4 _r is discriminated by a predetermined threshold, only the magnetic sensing element positioned on the traveling line (magnetic line) L outputs the traveling line detection signal. Will do.

Accordingly, when the traveling line L is detected from the i _L th magnetic sensing element from the left to the i _R th magnetic sensing element among the N magnetic sensing elements arranged at the pitch p, as shown in FIG. The position e of the center line of the line L is expressed as e = {(i _L + i _R ) − (N + 1)} · p / 2
Can be calculated as That is, the position e of the center line of the travel line L can be detected with a resolution that is half the arrangement pitch p of the magnetic sensing elements. If the sensors 4 _f and 4 _r are provided symmetrically about the central axis of the vehicle body 1, the position e of the center line of the travel line L detected as described above is straightforward. The amount of deviation of the vehicle body 1 from the travel line L in the lateral direction is indicated. As a result, the deviation amount e _f in the lateral direction from the running line L in the front-wheel side and rear wheel side of the vehicle body 1 at the front and rear pair of sensors 4 _f, 4 _r, e _r is obtained, respectively.

Here, it is assumed that the center (center of gravity) O of the vehicle body 1 is determined as the center position of the front wheels W _FL and W _FR and the rear wheels W _RL and W _RR . The pair of magnetic sensors 4 _f, 4 _r is the vehicle respectively distances in the longitudinal direction of said vehicle body 1 from the center O of the main body 1 (L _S / 2) at a, that is a pair of front and rear sensors 4 _f, 4 It is assumed that _r is provided symmetrically in the front-rear direction of the vehicle body 1 with respect to the center O with a distance L _S. Then shift amounts e _f of the in front-wheel side and rear-wheel side of the vehicle body 1 in the lateral direction from the running line L obtained respectively by each sensor 4 _f, 4 _r, from e _r, as shown in FIG. 5 The amount of lateral displacement y _e from the travel line L of the vehicle body 1 is represented by y _e = (e _f + _er ) / 2
Can be obtained geometrically.

In addition, the inclination angle (yaw angle deviation) φ _e of the vehicle body 1 with respect to the travel line L is a separation direction between the sensors 4 _f and 4 _{r with} respect to the travel line L as shown in FIG. Can be regarded as a tangent of a right triangle formed by the side defined by the above and the side defined by the lateral displacement direction (the width direction of the vehicle body 1) detected by the sensors 4 _f and 4 _r , respectively.
^{_{φ e = tan -1 {(e}} f -e r) / L S}
Can be obtained as

Thus the pair of front and rear sensors 4 _f, 4 at _r in the width direction of the front-wheel side and rear-wheel-side displacement amount e _f, if detects a e _r respectively, the vehicle body 1 these deviation amount e _f, according to e _r Can be detected as a lateral deviation y _e and a yaw angle deviation φ _e , respectively. Therefore, the relative orientation of the vehicle body 1 with respect to the travel line L is simply determined by the yaw in the vehicle coordinate system without obtaining the absolute orientation of the vehicle body 1 with respect to the ground coordinate system using an attitude angle sensor such as a gyro as in the prior art. The angle deviation φ _e can be easily obtained. In particular a pair of front and rear sensors 4 _f, 4 with _r in the width direction of the front-wheel side and rear-wheel-side displacement amount e _f, since the e _r need only detect, respectively, greatly simplifies the cost of the sensing system Therefore, there is a great practical advantage in incorporating it into an automatic guided vehicle.
<Estimation of travel distance>
By the way, when the vehicle body 1 is caused to travel while performing steering control according to the lateral deviation y _e and the yaw angle deviation φ _e obtained as described above, depending on the configuration of the control system, As shown in FIG. 6, the vehicle trajectory of the vehicle body 1 meanders with respect to the travel line L as shown by the broken line a, or understeer (two-dot chain line b) or over the curve of the travel line L. A steer (an alternate long and short dash line c) is generated, and the travel locus may deviate from the travel line L. When the vehicle main body 1 travels while causing such meandering or deviation with respect to the travel line L, for example, the travel distance of the vehicle main body 1 determined by the wheel diameter and the number of rotations thereof, and the vehicle main body 1 along the travel line L It cannot be denied that there is a deviation from the substantial moving distance. For this reason, if the stop position of the vehicle main body is controlled according to the travel distance of the vehicle main body 1, there arises a problem that the vehicle main body 1 stops before reaching the target stop position.

Therefore, the dead reckoning processing unit 20 projects the traveling speed V of the vehicle main body 1 on the traveling line L according to the lateral deviation y _e and the yaw angle deviation φ _e , whereby the vehicle on the traveling line L is projected. The moving speed V _L of the main body 1 is estimated. Then, by integrating the moving speed V _L , the moving distance on the travel line L is obtained, thereby realizing the accurate follow-up traveling to the target stop position described above.

For example, the meandering with respect to the travel line L described above can be regarded as travel in the yaw angle direction of the vehicle body 1 depending on the yaw angle deviation φ _e in a minute time. Accordingly, in this case, if the traveling speed V of the vehicle body 1 in a direction that forms an angle (yaw angle) φ _e with respect to the traveling line L is projected onto the traveling line L as shown in FIG. The substantial movement speed V _L of the vehicle body 1 on the line L is expressed as V _L = V · cosφ _e
Can be obtained as

Further, when turning along the travel line L, it can be considered that the vehicle is traveling along the travel line L while producing a lateral deviation y _e with respect to the travel line L due to over / under steer. . In particular, when the turning speed of the vehicle body 1 is γ, the distance ΔS traveled by the vehicle body 1 in the minute time Δt is:
ΔS = (R + y _e ) · γ · Δt
Can be expressed as Further, since the amount of movement by the turning motion in the minute time Δt can be considered to be equal to the amount of movement by the straight movement, the distance ΔS traveled by the vehicle body 1 in the minute time Δt is ΔS = V · Δt.
It can also be expressed as Therefore, as shown in FIG. 8, by projecting the traveling speed V of the vehicle main body 1 turning with a deviation ye from the traveling line L onto the traveling line L, the moving speed V _L on the traveling line L is obtained.
V _L = R · γ = V−y _e · γ
It is possible to estimate that.

Such turning traveling may occur while having the yaw angle deviation φ _e described above. Therefore, in this case, the travel speed V of the vehicle body 1 parallel to the running line L, and after temporarily projected onto the parallel line having a lateral deviation y _e relative to the running line L, in the parallel lines The projected speed may be projected onto the travel line _L to obtain the moving speed V _L.

In this way, the traveling speed V of the vehicle body 1 is projected onto the traveling line L according to the lateral deviation y _e and the yaw angle deviation φ _e with respect to the traveling line L, and thereby the substantial movement on the traveling line L. If the speed V _L is obtained, it is possible to accurately evaluate the moving distance of the vehicle main body 1 on the travel line L by integrating the moving speed V _L. Accordingly, even when the travel distance of the vehicle main body 1 is controlled using the dead reckoning technique, the travel distance can be accurately evaluated, so that the vehicle main body 1 is accurately stopped at the target stop position. It becomes possible to make it.

Particularly just simple method called projecting the lateral deviation y _e and the running speed V of the vehicle body 1 according to the yaw angle difference phi _e on the travel line L with respect to the travel line L of the vehicle body 1, substantially in the running line L The moving speed V _L can be accurately evaluated. Therefore, it becomes possible to grasp the moving distance of the vehicle main body 1 with high accuracy without being concerned with the problem of meandering with respect to the travel line L caused by the steering control delay or the like.
<Follow-up control command>
Meanwhile in driving the vehicle body 1 along a traveling line L indicates the lateral deviation y _e showing the lateral deviation of the vehicle body 1 with respect to the running line L mentioned above, the shift amount of orientation (angle) of the vehicle body 1 accordance with yaw angle difference phi _e, these lateral deviation y _e and yaw angle difference phi _e, respectively by using the speed controller 2 and the steering control unit 3 so that the [0] and the running speed and steering angle It is necessary to control each of them.

Incidentally, the trajectory tracking control by the non-holonomic control method that has been proposed in the past is mainly based on the position and direction of the target trajectory on the travel line L in the absolute coordinate system at a certain time [x _d , y _d , φ _d ], and the absolute position and direction at the center of gravity of the vehicle body 1 are [x, y, φ],

Since the holds, and a turning velocity command gamma _r a traveling speed command u _r necessary to follow the track _{u r = u d · cosφ e} + K x · x e
γ _r = γ _d + u _d (K _y · y _e + K _p · sinφ _e )
Asking. Where u _d is the target traveling speed, and γ _d is the target turning speed. K _x , K _y , and K _p are control gains, respectively. However, in order to obtain the absolute position and orientation of the vehicle body 1 [x, y, φ], for example, an azimuth sensor such as a gyro and a position detection sensor such as GPS (omnidirectional positioning system) are required. Cannot be denied.

In this respect, in the automatic guided vehicle according to this embodiment, as described above, the lateral deviation y _e and the direction deviation (yaw angle deviation) φ _e in the vehicle coordinate system are obtained. Also it can be obtained as the difference between the integrated value and the integral value of the target traveling velocity u _d of the moving velocity V _L on the running line L as described above for the longitudinal direction deviation x _e. Further, considering the skew of the vehicle main body 1 with respect to the travel line L, the above-described turning speed command γ _r can be grasped separately for the transverse and the turning. Therefore, from these viewpoints, control commands (traveling speed command value u _r , traverse speed command value ν _r , and turning speed command value γ _r ) necessary to travel following the travel line L are _expressed as u _r = u _d・ cosφ _e + K _x・ x _e
ν _r = K _y · u _d · y _e
γ _r = K _p · u _d · sinφ _e
As a result, it is possible to obtain them all together.
<Determination of steering angle>
By the way, in order to control the traverse speed and the turning speed based on the traverse command ν _r and the turning speed command γ _r described above, it is necessary to control the steering angle. In other words, it is obvious that if the vehicle is steered while traveling at a certain speed, a transverse speed and a turning speed corresponding to the traveling speed are generated. Conversely, the desired transverse speed and turning speed can be obtained. It is necessary to determine the steering angle.

Incidentally, a four-wheel steering type vehicle (automated guided vehicle) is equivalently expressed as a two-wheel model having one front wheel and one rear wheel at each center of the front wheel side and the rear wheel side as shown in FIG. be able to. The steering angles δ _FL , δ _{FR of} the pair of left and right front wheels W _FL , W _FR in the four-wheel model and the steering angles δ _RL , δ _{RR of the} pair of left and right rear wheels W _RL , W _RR , and the front and rear wheels in the two-wheel model Between each wheel steering angle δ _f , δ _r δ _f = (δ _FL + δ _FR ) / 2
δ _r = (δ _RL + δ _RR ) / 2
This relationship is established. In other words, when the relationship between the steering angles is established, a four-wheel steering type vehicle (automatic guided vehicle) can be regarded as the above-described two-wheel model.

When the absolute values of the steering angles δ _f , δ _r on the front wheel side and the rear wheel side are equal, the vehicle body 1 turns if the steering direction is in the opposite phase, and the vehicle body 1 is turned in the same phase. Keep skew while keeping. Further, if the steering angles δ _f , δ _r on the front wheel side and the rear wheel side are different and the steering direction is opposite in phase, the vehicle body 1 turns according to the steering angle difference, and turns if the steering direction is in phase. Will be skewed.

Therefore, in order to obtain the required traverse speed and turning speed, for example, after obtaining the opposite phase steering angle component δ _p for obtaining the required turning speed, the in-phase steering for obtaining the next necessary traverse speed is obtained. The angle component δ _y is obtained, and each of these steering angle components δ _p and δ _y is _{expressed as} δ _p = δ _f −δ _r
δ _y = (δ _f + δ _r ) / 2
The steering angles δ _f and δ _r on the front wheel side and the rear wheel side may be determined so as to satisfy this relationship. Therefore, in the speed controller 40, if the steering angle components δ _p and δ _y for obtaining the traverse speed and the turning speed necessary to follow the travel line L are obtained, these respective steering components δ are obtained. _{According to p} and δ _y δ _f = 0.5 δ _p + δ _y
δ _r = −0.5 δ _p + δ _y
The steering angles δ _f and δ _r on the front wheel side and the rear wheel side are respectively determined.
<Estimation of turning speed>
By the way, the control system for obtaining the traverse speed and the turning speed required to follow the travel line L is generally constituted by a PI (proportional / integral) control system as shown in FIG. Specifically, if the command traversing speed (traversing command ν _r ) is determined, a deviation Δν from the actual traversing speed ν of the vehicle body 1 at that time is obtained, and the steering command value with this deviation Δν as [0]. (Control value) δ _y may be obtained. Similarly, when the command turning speed (turning speed command γ _r ) is determined, a deviation Δγ from the actual turning speed γ of the vehicle main body 1 at that time is obtained, and a steering command value (0) is set with this deviation Δγ as [0]. Control value) δ _p may be obtained.

Note that the traverse speed command [nu _r and the turning velocity command gamma _r, and a lateral difference y _e and yaw angle difference phi _e of the vehicle body 1 with respect to the running line L as described above, [nu accordance with the target traveling velocity u _{d r} = K _y · u _d · y _e
γ _r = K _p · u _d · sinφ _e
Can be obtained as Further, the actual transverse speed ν of the vehicle body 1 can be estimated from the change in the lateral deviation y _e of the vehicle body 1 with respect to the travel line L described above. However, it is difficult to measure the actual turning speed γ of the vehicle body 1 unless a yaw rate sensor is used, for example.

Therefore, the speed controller 40 estimates the actual turning speed γ of the vehicle body 1 as follows. That is, the absolute values of the steering angles δ _f and δ _r of the front wheels and the rear wheels are equal, the steering directions are opposite to each other, and the center of gravity of the vehicle body 1 and the center point O coincide with each other. Assuming that the distance from each wheel is equal, assuming that the steering angle of the inner wheel is δ, the turning radius R _{0 of the} center of gravity is R ₁ = W _f / sin δ as shown in FIG.
R ₀ = R ₁ cos δ = W _f · cos δ / sin δ
As shown. However, _Wf is the distance (half the wheelbase length) from the center point O to the front wheels in the longitudinal direction of the vehicle. In the above equation, the term to be divided by [sin δ] indicates that the smaller the steering angle δ, the larger the turning radius. If the steering angle δ is [0], the turning radius is infinite, that is, a straight motion. Show.

In a very short time, it can be considered that the speed due to the turning motion and the traveling speed coincide with each other, so the turning speed γ when the traveling speed of the vehicle body 1 is V is γ = V / R _0.
Can be estimated as When the turning speed γ is estimated in this way, the steering angle δ of the inner wheel is required. The steering angle δ may be obtained from, for example, the stroke length of the cylinder that steers the wheel, or may be obtained by adding an appropriate control delay element to the stroke length command. Alternatively, it goes without saying that the turning speed γ may be calculated from the outputs of the sensors 4 _f and 4 _r described above.

When the steering angle δ is obtained based on the cylinder stroke length described above, the steering angle is actually obtained for each of the left and right wheels. Therefore, the average value of the steering angles of the left and right wheels is obtained, and the turning speed γ is estimated according to the average value of the steering angles. Actually, there is a difference between the center of gravity position and the center position O, which may cause an estimation error. However, since a certain amount of estimation error can be appropriately dealt with by feedback control, it does not become a fatal problem in executing steering control.
<Adjustment of control gain>
Incidentally, the turning speed γ described above depends on the traveling speed V of the vehicle body 1. Specifically, the turning speed γ is faster at the same steering angle than at low speeds. That is, when it is clear that the vehicle main body 1 can turn at a certain steering angle and traveling speed per second, if the traveling speed doubles, the vehicle main body 1 naturally turns per second. The angle is also doubled.

On the other hand, the turning speed γ at which the vehicle body 1 can turn stably is naturally limited. Therefore, when the turning command γ _r is obtained as described above, for example, as shown in FIG. 12, the steering gain is changed according to the traveling speed V of the vehicle body 1, and the turning speed γ at the time of high speed traveling becomes the turning limit. It is desirable to control so as not to exceed. Specifically, the steering command value is obtained by multiplying the control gain of the PI control system shown in FIG. 10 described above by setting the steering gain as [1] from a slow driving at a low speed such as alignment to a normal traveling speed V ₀ . Find δ _p . If the traveling speed V of the vehicle body 1 exceeds the normal traveling speed V ₀ and enters the high speed traveling region, the steering gain is gradually reduced according to the increase in the traveling speed, thereby the steering command value δ _p It is sufficient to suppress this.

When traveling at an extremely low speed where the movement of the vehicle body 1 is hardly recognized, it is desirable to set the steering gain to [0] as shown in FIG. 12, thereby prohibiting the steering itself. In this way, if a restriction that prevents the turning command γ _r from being output until a low-speed alignment speed of, for example, about 3 m / min is reached, so-called stationary can be prevented. The effect that it becomes possible to prevent the deformation | transformation by an unnecessary wear etc. is produced.

Thus, according to the automatic guided vehicle having the control system as described above, the deviations e _f , e from the travel line L on the front wheel side and the rear wheel side of the vehicle body 1 using the pair of front and rear sensors 4 _f , 4 _r. The lateral deviation y _e and the yaw angle deviation φ _{e of} the vehicle body 1 are obtained based on _r , and the control necessary for the trajectory tracking control for the travel line L according to the lateral deviation y _e and the yaw angle deviation φ _e. Since the commands (traveling speed command u _r , traverse speed command ν _r , and turning speed command γ _r ) are uniquely determined, the control system can be greatly simplified.

Further, the side of the vehicle main body 1 with respect to the travel line L can be obtained without knowing all of the orientation (posture) of the vehicle main body 1, the bending state of the travel line L, and the steering directions of the front wheels and the rear wheels. The control command values u _r , ν _r , γ _r required to accurately follow the travel line L can be obtained by simply detecting the direction deviation y _e and the yaw angle deviation φ _e, and these control command values The traveling speed of the vehicle main body 1 and the steering angles δ _f and δ _r of the front and rear wheels can be controlled with high accuracy according to u _r , ν _r and γ _r . In addition, it is possible to achieve practically great effects such as that the steering angles δ _f and δ _r of the front wheels and the rear wheels can be uniquely determined by simple arithmetic processing and used for the steering control.
<Modification>
The present invention is not limited to the embodiment described above. For example, in this embodiment, the lateral deviation y _e and the yaw angle deviation φ _e of the vehicle body 1 with respect to the travel line L are determined by the front wheel side and rear wheel side deviations determined by the pair of front and rear magnetic sensors 4 _f and 4 _r . the amount e _f, has been to calculate the e _r, or calculated yaw angle deviation from the data representing the absolute angle to the direction of the traveling line L with respect to ground coordinates of the vehicle body 1 obtained by using a gyro, also GPS The lateral deviation may be calculated from the vehicle position in the ground surface coordinate system detected using and the coordinate data of the travel line L in the ground surface coordinate system .

Although the case where the travel line L is realized as a magnetic line has been described as an example here, when the travel line is formed with a white line, it is of course possible to optically detect this and control the travel. is there. Furthermore, various methods can be appropriately employed as a method for estimating the traverse speed and the turning speed of the vehicle body.
Further, when the front wheels W _FL , W _FR and the rear wheels W _RL , W _RR are steered in the same phase in a four-wheel steering type automatic guided vehicle, the vehicle body 1 travels obliquely with respect to the travel line L, and the front wheel side and One of the rear wheel side sensors 4 _f and 4 _r may derail from the travel line L. In this case, for example, the output of the derailed sensors 4 _f and 4 _r may be ignored, and the traveling may be controlled so that only the skew by in-phase steering is performed. Specifically, only the output of one sensor 4 _f (4 _r ) is used, and the other sensor 4 _r (4 _f ) outputs the same value (deviation amount) as the one sensor 4 _f (4 _r ). Therefore, it is sufficient that the yaw angle deviation φ _e does not exist and only the skew by in-phase steering is performed.

In this case, the timing at which the output of the other sensor 4 _f (4 _r ) is validated is controlled by monitoring the skew distance of the vehicle body 1, for example, even if the skew is carried out over a predetermined distance, the other If the travel line L cannot be detected from the sensor 4 _f (4 _r ), it is determined that the vehicle body 1 has deviated greatly from the travel line L, or the yaw angle deviation φ _e is large. It is desirable to stop the running. In addition, the present invention can be variously modified and implemented without departing from the scope of the invention.

The figure which shows the whole process concept for implement | achieving the follow-up control in the automatic guided vehicle which concerns on this invention. The figure which shows schematic structure of an automatic guided vehicle. The figure for demonstrating the principle of the deviation | shift amount detection by a magnetic sensor. The figure which shows the whole structure of the tracking travel control system with respect to the travel line of an automatic guided vehicle. Shift amount detected by the pair of front and rear sensors e _f, illustrates the principle of calculating the lateral deviation y _e and yaw angle difference phi _e of the vehicle body based on e _r. The figure which shows the following traveling locus of the vehicle main body with respect to a traveling line. The figure which shows the moving speed calculated | required by projecting the driving speed of the vehicle main body which drive | works with yaw angle deviation (phi) _e on a driving line. It shows the moving speed obtained by projecting the travel speed of the vehicle body for pivoting a lateral deviation y _e on the running line. The figure which shows the relationship between a 4-wheel model and a 2-wheel model. The figure which shows the general structure of the control system which each obtains the traverse speed and turning speed required in order to follow the driving | running | working line L. The figure which shows the relationship between the steering angle (delta) of a vehicle main body, and its turning radius _R0 . The figure which shows the example of the steering gain according to the running speed which determines turning speed.

Explanation of symbols

a Detection means (sensor)
b Projection means c Distance difference detection means d Command value calculation means e Traverse speed estimation means f Steering control means g Turning speed estimation means h First calculation means (first steering angle δ _y )
i Second computing means (second steering angle δ _p )
L traveling line 1 vehicle body 2 speed control unit 3 steering control unit 4 _f and 4 _r sensors (magnetic sensors)
5 Travel Control Unit 10 Sensor Processing Unit 20 Dead Reckoning Processing Unit 30 Trajectory Tracking Speed Command Generator 40 Speed Controller

Claims (5)

An automatic guided vehicle that drives the vehicle body at a specified target speed along a travel line set in advance on a road surface while steering front wheels and rear wheels provided on the vehicle body ,
A sensor mounted on the vehicle main body for detecting the traveling speed V of the vehicle main body, and a lateral displacement of the front wheel side of the vehicle main body with respect to the travel line mounted on the front wheel side and the rear wheel side of the vehicle main body, respectively. a sensor for determining the respective lateral deviation amount e _r quantity e _f and the rear wheel side of the vehicle body, the lateral displacement of the vehicle body relative to the running line on the basis of the lateral displacement amount e _f, e _r Detecting means for respectively obtaining a lateral deviation y _e indicating a quantity and a yaw angle deviation φ _e indicating a deviation angle of the direction of the vehicle body with respect to the direction of the travel line ;
The projection operation to the running line on the running speed V of the vehicle body based on the detected lateral deviation y _e and the yaw angle deviation phi _e at the detecting means on the traveling line of the vehicle body A projecting means for obtaining a moving speed _VL ;
Distance determining the longitudinal direction deviation x _e of the vehicle body in the traveling line direction from the difference between the integral value of the moving velocity V _L of the integrated value of the designated the target speed u _d and the vehicle body relative to the vehicle body Difference detection means;
Lateral deviation y _e of the vehicle _body, yaw angle difference phi _e, on the basis of the longitudinal direction deviation x _e, and said target speed u _d, along the vehicle body according to a preset arithmetic expression on the running line a command value calculating means for calculating the traveling speed command value required to travel at a desired velocity u _d u _r, the rotation speed command value gamma _r, and the traverse speed command value [nu _r respectively,
In the control the speed of the vehicle body on the basis of the traveling speed command value u _r, the steering angle of the phase between the front and rear wheels necessary to obtain the transverse velocity of the vehicle body in which the traverse speed instruction value [nu _r indicates with obtaining the component [delta] _p, obtaining the steering angle component [delta] _y reversed phase between the rotation speed command value gamma _r the front and rear wheels necessary to obtain a rotation speed gamma of the vehicle body shown, these steering angle The steering angles δ _f and δ _r of the front wheels and the rear wheels are determined according to the components δ _p and δ _y.
δ _r = 0.5 δ _p + δ _y
δ _r = −0.5 δ _p + δ _y
And a steering control means for steering the front wheels and the rear wheels, respectively . The travel line is a magnetic line laid on the road surface,
The lateral deviation y _e and the yaw angle deviation φ _e of the vehicle body are detected by a pair of front and rear line-type magnetic sensors provided on the vehicle body, respectively, and the magnetism on the front wheel side and the rear wheel side of the vehicle body. shift amount in the width direction from the line e _f, AGV of claim 1 are those obtained from each e _r. It said projection means, the running speed V _L of the vehicle body on the running line on the basis of the running speed V and the yaw angle difference phi _e of the vehicle body
V _L = V · cosφ _e
As or when said vehicle turning speed of the body γ is demanded, and a running speed V and the lateral deviation y _e of the vehicle body
V _L = V−y _e · γ
The automatic guided vehicle according to claim 1 , wherein a moving speed _VL of the vehicle body on the travel line is obtained . Said steering control means includes a traversing speed estimating means for estimating a traverse speed ν of the vehicle body toward the traveling line from a change in the lateral deviation y _e, the vehicle body obtained from the steering angle of the front wheels and rear wheels provided from the turning radius R ₀ and the running speed V of the vehicle body and the turning speed estimating means for estimating a rotation speed γ of said vehicle body,
A first steering angle δ _y is obtained with the difference between the traverse speed ν estimated by the traverse speed estimation means and the traverse speed command value ν _r as [0], and the turning estimated by the turning speed estimation means A second steering angle δ _p with a difference between the speed γ and the turning speed command value γ _r as [0] is obtained;
2. The front and rear wheels are respectively steered by determining the steering angles δ _f and δ _r of the front and rear wheels from the first and second steering angles δ _y and δ _p. The automatic guided vehicle described. The computing means for obtaining the first and second steering angles δ _y and δ _p respectively change the control gain for the first and second steering angles δ _y and δ _p according to the traveling speed V of the vehicle body. To do,
When the traveling speed V of the vehicle body is equal to or lower than a preset constant traveling speed V ₀ , the first and second steering angles δ _y and δ _p are respectively obtained under a certain control gain,
When the traveling speed V of the vehicle body exceeds the constant traveling speed V ₀ , the first and second steering angles δ _y , under a control gain that is set smaller as the traveling speed V increases. AGV of claim 4 [delta] _p and requests respectively.

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