WO2022131050A1

WO2022131050A1 - Automatic steering system

Info

Publication number: WO2022131050A1
Application number: PCT/JP2021/044710
Authority: WO
Inventors: 亮亮楊; 洋平星野
Original assignee: 国立大学法人北見工業大学
Priority date: 2020-12-18
Filing date: 2021-12-06
Publication date: 2022-06-23
Also published as: JPWO2022131050A1

Abstract

An automatic steering system comprising: an angular velocity measuring means for detecting the turning angular velocity of a moving body; a distance calculating means for calculating a distance between the current position of the moving body and a target path; a target angular velocity calculating means for calculating, on the basis of the distance calculated by the distance calculating means, a target angular velocity necessary for a turn by the moving body; a turning velocity calculating means for calculating, from the difference between the target angular velocity calculated by the target angular velocity calculating means and the turning angular velocity of the moving body measured by the angular velocity measuring means, an angular velocity at which a steering wheel of the moving body is to turn; and a steering controlling means for transmitting the angular velocity at which the steering wheel of the moving body is to turn, which was calculated by the turning velocity calculating means, to a steering actuator and executing steering control.

Description

Automatic steering system

The present invention relates to an automatic steering system that controls steering so as to travel according to a target route prepared in advance without depending on an orientation sensor such as an inertial measurement unit when automatically driving a moving body.

It is necessary to automatically control the steering wheels in order to automatically drive a moving object such as a trackless vehicle, and as a method for that, a technique for automatically controlling the steering wheels using an azimuth sensor is known. In this autopilot technique, for example, as shown in FIG. 7, when the vehicle 1'is driven while being steered according to a target path R prepared in advance, the steering angle of the steering wheels is determined by the following steps. Was. (1) Step to prepare the target route R in advance, (2) The current direction and target route of the vehicle 1'using the inertial measurement unit IMU (Inertial satellite unit) that detects the three-dimensional angular velocity and acceleration as the orientation sensor. Step to calculate the difference (θ) between directions, (3) Calculate the distance difference (d) between the current position of the vehicle 1'and the target route R using the global positioning system GNSS (Global Navigation Satellite System). Step, (4) Step to calculate the angle (α) of the steering wheel (front wheel) 4 using the difference between these two, (5) Send the calculated angle (α) of the steering wheel 4 to the steering actuator, and the steering wheel It was decided using the step of maneuvering.

However, the method of determining the vehicle direction in the above-mentioned conventional automatic control technique is expensive because the measurement is performed by using the inertial measurement unit IMU which is an azimuth sensor and using the sensor fusion (the inertial measurement unit IMU is hundreds of thousands). There was a problem that the manufacturing cost was high because it was (yen to several million yen).

In addition, when the above-mentioned azimuth sensor is used, the accuracy of the measured azimuth is low (about ± 1 degree at the highest), and since it is measured by sensor fusion, it outputs accurately if the wheels do not move (that is, if the vehicle does not start moving). There were problems such as not being able to output and it took time to output at the correct angle.

Further, the method of determining the vehicle direction in the conventional automatic control technique requires mounting a wheel angle sensor in order to correctly control the angle of the steering wheel, and it is not possible to make the mounting of this angle sensor on the vehicle error-free. It was difficult and there was always a gap. Therefore, there is a problem that the control accuracy of the steering wheel is not improved even though the high cost angle sensor is used.

In addition, the control method in the conventional automatic control technique is generally control in which the steering angle target value is given to the steering motor as a command signal. However, the motor driver that drives the actual steering motor can basically control the angular velocity with high accuracy and without delay, but the tracking to the target angle is usually a time delay that cannot be ignored. There was a problem that it occurred.

Therefore, an object of the present invention is to provide an automatic steering system capable of low-cost and high-precision steering control without depending on an orientation sensor such as an inertial measurement unit.

According to the present invention, there is provided an automatic steering system that controls steering so as to travel according to a target route prepared in advance. This automatic steering system is based on an angular velocity measuring means for detecting the turning angular velocity of the moving body, a distance calculating means for calculating the distance between the current position of the moving body and the target path, and a distance calculated by the distance calculating means. , The steering handle of the moving body is based on the difference between the target angular velocity calculating means for calculating the target angular velocity required for turning the moving body, the target angular velocity calculated by the target angular velocity calculating means, and the turning angular velocity of the moving body measured by the angular velocity measuring means. It includes a turning speed calculating means for calculating the angular velocity to be turned, and a steering control means for transmitting the angular velocity to be turned by the steering handle calculated by the turning speed calculating means to the steering actuator to perform steering control.

The angular velocity measuring means detects the actual turning angular velocity of the moving body, and the steering handle of the moving body turns from the difference between the target angular velocity required for the moving body to turn and the actual turning angular velocity of the moving body measured by the angular velocity measuring means. By calculating the angular velocity to be calculated and transmitting the calculated angular velocity to the steering actuator to perform steering control, the calculated angular velocity is low cost and highly accurate without depending on the orientation sensor such as an inertial measurement unit. Steering control is possible.

The target angular velocity calculation means is configured to calculate the target angular velocity required for turning the moving body using the formula: γ = g (d) (in the formula, d is the current position and target path of the moving body). The distance between, g is preferably the control function related to the control gain).

The turning speed calculation means is configured to calculate the angular velocity at which the steering handle should turn using the formula: μ = h (γ-ω) (in the formula, γ is the target angular velocity required for turning the moving body). , Ω is the turning angular velocity of the moving body measured by the angular velocity measuring means, and h is a control function related to the control gain).

The moving object is a vehicle, and the angular velocity measuring means is one of image processing by a gyroscope, an acceleration sensor or a camera, or a combination of two or more image processing by a gyroscope, an acceleration sensor and a camera, and is a gyroscope. When using, it is also preferable that the gyroscope is provided on the main body of the vehicle.

It is also preferable to further include a receiving means for receiving the positioning signal from the satellite positioning system and a current position acquisition means for acquiring the current position of the moving object based on the positioning signal.

According to the present invention, the actual turning angular velocity of the moving body is detected by the angular velocity measuring means (for example, a gyroscope), the target angular velocity required for the moving body to turn, and the actual turning angular velocity of the moving body measured by the angular velocity measuring means. The angular velocity at which the steering handle of the moving body should turn is calculated from the difference between the two, and the calculated angular velocity at which the steering handle should turn is transmitted to the steering actuator to perform steering control, thereby relying on an orientation sensor such as an inertial measurement unit. Since an inexpensive gyroscope is used, low cost and high precision steering control is possible.

It is a figure which shows roughly the structure of the automatic steering system which concerns on one Embodiment of this invention. FIG. 3 is a block diagram schematically showing a configuration example of an automatic steering system in FIG. 1. It is an image diagram which shows the control method of the automatic steering system of this invention. It is a figure which shows the relational model of a steering wheel turning angle and a turning radius. It is a flow chart which shows the processing process of the steering control in the automatic steering system of FIG. 1 schematically. It is a figure which shows the running test result using the steering control method of the automatic steering system of this invention. It is an image diagram which shows the control method of the conventional automatic steering system.

Hereinafter, embodiments of the automatic steering system according to the present invention will be described with reference to the drawings.

FIG. 1 schematically shows an autonomous driving vehicle 1 provided with an automatic steering system 100 according to an embodiment of the present invention, FIG. 2 shows a configuration of the automatic steering system 100 of FIG. 1, and FIG. 3 shows a configuration. The steering control method of the automatic steering system 100 is shown as an image.

As shown in FIG. 1, the automatic steering system 100 is provided in the main body of the vehicle (mobile body) 1 and is configured to be able to communicate with the satellite positioning system and the reference station. The vehicle 1 includes a steering actuator 2, a steering mechanism 3 having a steering handle, front wheels 4 steered by the steering mechanism 3, and rear wheels 5. In this embodiment, the vehicle 1 is a tractor. The steering actuator 2 is connected to the steering mechanism 3 and is configured to be able to operate the steering mechanism 3 in response to an operation signal from the automatic steering system 100.

Further, as shown in FIG. 2, the automatic steering system 100 includes a gyroscope 10, a receiving unit 20, an input unit 30, an output means 40, a data bus 50, a storage unit 60, and a control unit 70. I have.

The gyroscope 10 is provided as an angular velocity measuring means at substantially the center of the vehicle 1 (center of gravity position G), and is used to detect the direction (traveling direction) and the angular velocity of the vehicle 1. Here, the gyroscope 10 is configured to detect the direction of the vehicle 1 and the actual turning angular velocity. The gyroscope 10 detects the direction of the vehicle 1 by accumulating the direction changes from the initial direction.

As shown in FIG. 1, the receiving unit 20 is configured to communicate with a satellite positioning system (for example, a GPS satellite or the like) and a reference station and receive a positioning signal. The positioning data acquired by the receiving unit 20 is stored in the storage unit 60.

The input unit 30 is composed of a keyboard, a touch panel, or the like, and is for inputting registration information such as a target route, a transmission / reception address, a processing operation start command, and other necessary information. The input unit 30 may be connected and installed only when necessary.

The output means 40 constitutes the transmission unit of the present embodiment, and is configured to transmit an output signal such as steering control processed by the control unit 70 to the steering actuator 2 via a wired or wireless communication network. ing.

The data bus 50 is connected between the gyroscope 10, the receiving unit 20, the input unit 30, the output means 40, the storage unit 60, and the control unit 70, and is provided to enable data transfer between them according to a control program. ing.

The storage unit 60 is mainly composed of, for example, a storage medium such as a hard disk drive (HDD) or a solid state drive (SSD), a volatile memory such as RAM, and a non-volatile memory such as ROM or Flash memory. The storage unit 60 is provided with a control program storage unit 60a, a positioning data storage unit 60b, a direction data storage unit 60c, and a target route storage unit 60d. The control program storage unit 60a stores a program for controlling the operation of the automatic steering system 100. The positioning data storage unit 60b stores the data of the current position of the vehicle 1 received from the satellite positioning system. The direction data storage unit 60c stores the direction and angular velocity of the vehicle 1 detected by the gyroscope 10. The target route storage unit 60d stores data of the target route prepared in advance.

The control unit 70 is mainly composed of a microcomputer, includes a CPU (Central Processing Unit), controls the entire operation of the automatic steering system 100 according to a control program, and uses this control program to control the current position acquisition means 70a and the current position acquisition means 70a. The distance calculation means 70b, the target angular velocity calculation means 70c, the turning speed calculation means 70d, and the steering control means 70e are configured to be constructed. The current position acquisition means 70a is configured to receive data on the current position of the vehicle 1 from the satellite positioning system. The distance calculating means 70b is configured to calculate the distance d between the current position acquired by the current position acquiring means 70a and the target path R prepared in advance. The target angular velocity calculating means 70c is configured to calculate the target angular velocity γ required for the vehicle 1 to turn based on the distance d calculated by the distance calculating means 70b. The turning speed calculating means 70d is an angular velocity μ that the steering handle of the vehicle 1 should turn from the difference between the target angular velocity γ calculated by the target angular velocity calculating means 70c and the actual turning angular velocity ω of the vehicle 1 measured by the gyroscope 10. Is configured to calculate. The steering control means 70e is configured to transmit the angular velocity μ to be turned by the steering handle calculated by the turning speed calculating means 70d to the steering actuator 2 to perform steering control. In the present invention, an example using PID control is shown, but it is not limited to PID control, and it is desirable to use a control system with higher robustness (for example, a sliding mode control system).

Hereinafter, the steering control model of the present invention will be described with reference to FIG. FIG. 4 shows the relationship between the steering wheel turning angle and the turning radius. In the present specification, the dot (.) Attached above the symbol represents the first-order time derivative d / dt.

As shown in FIG. 4, the relationship between the steering wheel turning angle δ and the turning radius ρ of the moving body is expressed by the equation (1). Here, when the steering wheel turning angle δ is small,

Is.

In the formula, L is the distance (constant) between the front wheels and the rear wheels. Therefore, once the required turning radius ρ is determined, the steering wheel turning angle δ can be calculated. If the forward speed v is 0, the vehicle itself does not move, so that the vehicle 1

Is also 0. In order to turn the vehicle 1, it is necessary that both the forward speed v and the steering wheel turning angle δ are not 0. As shown in FIG. 4, the vehicle 1

And the forward speed v and the turning radius ρ are related to the equation (2).

Substituting the above equation (1) into the equation (2) yields the equation (3).

From this formula (3), the vehicle 1

Is proportional to the forward speed v and the steering wheel turning angle δ.

The formula (3) can be rearranged into the formula (4).

Substituting equation (4) into equation (1) yields equation (5).

From equation (5), vehicle 1

If is determined, it can be seen that the turning radius ρ is uniquely determined. Therefore, when performing automatic steering control, the vehicle 1

If is controlled, the turning radius ρ of the vehicle 1 can be controlled.

The target angular velocity γ can be calculated by the equation (6). That is, the goal of automatic steering is to bring d closer to zero. When d is large, a high turning angular velocity is required, and when d is small, a slow turning angular velocity is required.

In the equation, d is the distance between the current position and the target path, and k _p1 , _{ki 1} , and k _{d 1} are control gains (feedback gains), which are constants adjusted in the experiment.

The angular velocity μ to be turned by the steering wheel can be calculated by using the equation (7).

In the equation, γ is the result calculated by the equation (6), and ω is the actual turning angular velocity of the vehicle 1 measured by the gyroscope 10. Further, k _p2 , _ki2 , and k _d2 are control gains (feedback gains), which are constants adjusted in the experiment. It is desirable to use a control system with higher robustness instead of this equation (7).

As described above, in the steering in the automatic steering system 100 of the present invention, the target angular velocity γ (γ = g (d), where g is a control function) required for turning by the vehicle itself, not the steering wheels, is used. calculate. As a result, it is not necessary to attach an angle sensor to the steering wheel, and the cost can be reduced. Further, it can be mounted on a vehicle other than the wheel type, for example, a caterpillar type vehicle.

Next, the steering operation of the automatic steering system 100 of the present invention will be described with reference to FIG. The automatic steering system 100 needs to set a target route in advance. Steering control is performed so as to travel along this target route.

In the steering control of the automatic steering system 100, first, the gyroscope 10 detects the actual turning angular velocity ω of the vehicle 1 (step S1). Next, the data of the current position of the vehicle 1 is received using the satellite positioning system (step S2). Next, the distance d between the current position of the vehicle 1 and the target route is calculated (step S3). Based on the distance calculated in step S3, the target angular velocity γ (γ = g (d)) required for the vehicle 1 to turn is calculated (step S4) (see equation (6)). Next, the angular velocity μ to be turned by the steering handle of the vehicle 1 is calculated from the difference (γ-ω) between the target angular velocity γ calculated in step S4 and the actual turning angular velocity ω of the vehicle 1 measured by the gyroscope 10 (γ-ω). Step S5). The angular velocity of the steering wheel to be turned is calculated by μ = h (γ-ω) (see equation (7)). Here, h is a control function. Next, the angular velocity μ of the steering wheel to be turned calculated in step S5 is transmitted to the steering actuator 2, and steering control of the vehicle 1 is performed (step S6).

FIG. 6 shows the results of a running experiment of the vehicle 1 using the automatic steering system 100 of the present invention. As shown in FIG. 6, when the traveling speed of the vehicle 1 using the automatic steering system 100 is 1 m / s, the lateral deviation immediately converges within 0.02 m from −0.04 m at the start. After that, it was confirmed that the vehicle could run stably within 0.02 m in the lateral deviation.

As described above, in the present embodiment, the automatic steering system 100 is provided in the main body of the vehicle 1 and is configured to be able to communicate with the satellite positioning system and the reference station. The automatic steering system 100 includes a gyroscope 10, a receiving unit 20, an input unit 30, an output means 40, a data bus 50, a storage unit 60, and a control unit 70. Further, the vehicle 1 includes a steering actuator 2, a steering mechanism 3 having a steering handle, front wheels 4 steered by the steering mechanism 3, and rear wheels 5.

The actual turning angular velocity ω of the vehicle 1 is detected by the gyroscope 10 provided in the vehicle 1, and the difference between the target angular velocity γ required for the vehicle 1 to turn and the actual turning angular velocity ω of the vehicle 1 measured by the gyroscope 10. The angular velocity μ of the steering handle of the vehicle 1 to be turned is calculated from, and the calculated angular velocity of the steering handle to be turned is transmitted to the steering actuator 2 to perform steering control. Therefore, an inexpensive gyroscope is used, so that an inertial measurement unit is used. It is possible to perform low-cost and high-precision steering control that does not depend on the orientation sensor such as.

Further, since the automatic steering system 100 of the present invention is not measured by sensor fusion, the angle representing the direction of the vehicle cannot be accurately output unless the vehicle moves as in the conventional case, and it takes time to output the correct angle. You can solve the problem.

Further, in the automatic steering system 100 of the present invention, the angular speed at which the steering handle should turn is used as a control signal for the command signal to the motor driver of the steering actuator 2, and the motor driver is considerably accurate by the steering angular speed signal commanded to the motor driver. The steering angle speed dδ / dt can be controlled.

Although the embodiment of steering control of a vehicle (tractor) as a moving body has been described in the above-described embodiment, the present invention is not limited to this. For example, it can be applied to a transfer robot, a caterpillar type vehicle, and the like.

Further, in the above-described embodiment, an example in which the gyroscope 10 is used as the angular velocity measuring means has been described, but the present invention is not limited thereto. For example, image processing by an accelerometer or a camera may be used. Alternatively, a combination of two or more of image processing by a gyroscope, an acceleration sensor, and a camera may be used.

The embodiments described above are illustrative and not limited to the present invention, and the present invention can be carried out in various other modifications and modifications. Therefore, the scope of the present invention is defined only by the scope of claims and the equivalent scope thereof.

The automatic steering system of the present invention can be used for the purpose of detecting the position and posture of a moving body and performing steering control according to a target path prepared in advance, which does not depend on the directional sensor.

1, 1'Vehicle (moving body)
2 Steering actuator 3 Steering mechanism 4 Front wheels 5 Rear wheels 10 Gyroscope (angular velocity measuring means)
20 Receiver 30 Input unit 40 Output means 50 Data bus 60 Storage unit 60a Control program storage unit 60b Positioning data storage unit 60c Directional data storage unit 60d Target route storage unit 70 Control unit 70a Current position acquisition means 70b Distance calculation means 70c Target Angular velocity calculation means 70d Turning speed calculation means 70e Steering control means 100 Automatic steering system G Center of gravity R Target path

Claims

It is an automatic steering system that controls steering so that the vehicle travels according to a target route prepared in advance.
An angular velocity measuring means that detects the turning angular velocity of a moving object,
A distance calculation means for calculating the distance between the current position of the moving body and the target path, and
A target angular velocity calculating means for calculating a target angular velocity required for turning the moving body based on the distance calculated by the distance calculating means, and a target angular velocity calculating means.
A turning speed calculating means for calculating the angular velocity at which the steering handle of the moving body should turn from the difference between the target angular velocity calculated by the target angular velocity calculating means and the turning angular velocity of the moving body measured by the angular velocity measuring means.
An automatic steering system comprising: a steering control means for transmitting an angular velocity to be turned by the steering handle calculated by the turning speed calculating means to a steering actuator to perform steering control.
The target angular velocity calculating means is configured to calculate the target angular velocity required for turning the moving body using the formula: γ = g (d) (in the formula, d is the current position of the moving body). The automatic steering system according to claim 1, wherein the distance to and from the target path, g is a control function related to the control gain).
The turning speed calculating means is configured to calculate the angular velocity at which the steering handle should turn using the formula: μ = h (γ—ω) (in the formula, γ is necessary for turning the moving body). The automatic steering system according to claim 1 or 2, wherein ω is a target angular velocity, ω is a turning angular velocity of the moving body measured by the angular velocity measuring means, and h is a control function related to a control gain).
The moving body is a vehicle, and the angular velocity measuring means is any one of image processing by a gyroscope, an acceleration sensor or a camera, or a combination of two or more image processing by a gyroscope, an acceleration sensor and a camera. The automatic steering system according to claim 1 or 2, wherein when the gyroscope is used, the gyroscope is provided on the main body of the vehicle.
The moving body is a vehicle, and the angular velocity measuring means is one of image processing by a gyroscope, an acceleration sensor or a camera, or a combination of two or more image processing by a gyroscope, an acceleration sensor and a camera. The automatic steering system according to claim 3, wherein when the gyroscope is used, the gyroscope is provided on the main body of the vehicle.
Claim 1 or 2 is further provided with a receiving means for receiving a positioning signal from the satellite positioning system and a current position acquisition means for acquiring the current position of the moving object based on the positioning signal. The automatic steering system described in.
3. The third aspect of the present invention is characterized in that it further includes a receiving means for receiving a positioning signal from the satellite positioning system and a current position acquisition means for acquiring the current position of the moving object based on the positioning signal. Automatic steering system.
4. The fourth aspect of the present invention is characterized in that it further includes a receiving means for receiving a positioning signal from the satellite positioning system and a current position acquisition means for acquiring the current position of the moving body based on the positioning signal. Automatic steering system.
5. The fifth aspect of the present invention is characterized in that it further includes a receiving means for receiving a positioning signal from the satellite positioning system and a current position acquisition means for acquiring the current position of the moving body based on the positioning signal. Automatic steering system.