JPS6351643B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an automatic steering device for a transplanting machine, and more specifically, the present invention relates to an automatic steering device for a transplanting machine, and more specifically, the present invention uses a seedling sensor that detects the relative positional relationship between a planted seedling and the machine body, which is basic information for steering control, by contacting a planted seedling and emitting a predetermined signal. In addition, we have proposed an automatic steering system in which the seedling sensors are arranged in the same way on the left and right sides of the aircraft, and the row alignment can be performed automatically. The present invention will be explained in detail below based on drawings showing embodiments thereof. FIG. 1 is a left side view of a rice transplanter equipped with an automatic steering device according to the present invention, in which traveling drive and speed change are performed by a hydrostatic drive device, and steering is performed from left to right. This is done by cutting off the pressure oil supply to one of the hydraulic motors attached to each of the front wheels, and the pressure oil supply can be stopped manually by rotating the steering wheel 101 or by using a solenoid valve. This can be done automatically by energizing the solenoids 2l and 2r (see Figure 8). The planting section 103 is connected to the front of the fuselage body by one top link 104 and a pair of left and right lower links 105 (only the left one is shown in the figure).
Further, the lift arm 106 (only the left one is shown in the figure) connected to the left and right lower links 105 is moved up and down by vertical movement. Four sets of seedling sensors are attached to the left and right lower links 105, respectively. That is, lower link 1 is connected to the left seedling sensor as shown in FIG.
A sensor box 108 is attached to the tip of an arm 107 made of a pipe that extends outward from the fuselage. It is set up. The touch rods 81 to 84 are made of thin conductors,
The front and rear ends are curved upward, and the middle straight section is about 150 mm, and the front end is fixed within the sensor box 108 and connected to the internal electronic circuit, respectively. The touch rods 81 to 84 are spaced approximately 50 mm apart in the left and right directions of the aircraft.
They are arranged in the order of 2, 83, 84 from left to right,
In order to ensure this distance, the front curved portion of the straight portion and the rear end portion are fixed to horizontal rods 109, 109 made of electrical insulators by an appropriate method, so that the overall structure is shaped like a sled. The group of four contact rods 81 to 84 forms the row of planted seedlings that is closest to the aircraft among the group of planted seedlings when the planting section 103 is lowered and its float 110 lands on the water. The length of the arm 107 and the length of the touch rod itself are determined so that the top of the seedling can be contacted. FIG. 3 is an electronic circuit diagram of the main part of the device of the present invention.
To explain the structure of the seedling sensor 81l shown in detail in this figure, the touch rod 81 is connected to the - input terminal of the comparator 11 via the protective resistor 15, and a bias voltage is connected between the + and - input terminals of the comparator. Resistor 14 and two protection diodes 1 in antiparallel
6 and 16 are connected in parallel. The bias resistor 14 has a high resistance value of about 10 MΩ, and biases the potential of the - input terminal of the comparator 11 to be slightly higher than the potential of the + input terminal. Now, the surface resistance value of the planted seedling Z from the base to the tip that comes into contact with the touch rod 81 is in the range of approximately 50MΩ to 100MΩ, although it depends on its moisture absorption state or moisture adhesion state, and the value is generally around 80MΩ. It is becoming. The plant base of the already planted seedling Z is in water in the field, and its potential is the same as the body ground, so when its tip comes into contact with the contact rod 81, the contact rod is grounded through the high resistance of the already planted seedling Z. Therefore, the potential of the - input terminal of the comparator 11 is slightly lower than the potential of the + input terminal, and the output terminal OUT of the comparator 11 is connected to the planted seedling Z.
will change from a low level in the case of non-contact to a high level. In this way, one seedling sensor has 1
It consists of a book touch stick and electronic circuits connected to it, such as a comparator 11 and a bias resistor 14. In Figure 3, the touch stick group installed on the left side of the fuselage is 8l, and the touch stick group installed on the right side is 8r. , the seedling sensors 81l, 82l, 83l, 84l are respectively associated with the contacting rods 81, 82, 83, and 84 constituting the left-hand contacting rod group 8l.
It is expressed as On the other hand, the configuration of the right hand group 8r is similar to the one on the left, with each contact rod being arranged from left to right.
1, 82, 83, and 84 are arranged in parallel in this order. Then, the seedling sensors 81r, 82r, 83r, and 84r associated with the right touch rods 81, 82, 83, and 84 are respectively attached.
The outputs of these eight left and right seedling sensors, that is, the output terminals OUT of each comparator 11
The signals obtained from 81l and 81r, 82l and 8
2r, 83l and 83r, and 84l and 84r are respectively input into pairs as a pair to the input ports P ₁₀ to _{P 13} of the data processing device 1 which is the control center of the device of the present invention. The sensor unit 80l consisting of the seedling sensors 81l and 84l and the sensor unit 80r consisting of the seedling sensors 81r to 84r are respectively attached to the left and right lower links 105 as described above, but the data processing device 1 is attached to the machine body. It is stored in a suitable place in the main body, for example, in the operation column 111. The seedling sensor is highly sensitive and detects the presence of high-resistance planted seedlings when they come into contact with the touch rod, so the end of the touch rod on the sensor box side has a structure with a covering and a grounding external conductor, like a shielded wire. and comparator 1
1. It is best to use shielded wires for the conductors used to connect to the bias resistor 14, etc., to prevent malfunctions due to external interference, and for the same purpose, shorten the distance between the touch rod and the comparator 11. However, since the output impedance of the comparator 11 is low, the wiring from the comparator 11 to the data processing device 1 (two for power supply per sensor unit, one for output per seedling sensor) is There is no need for shielding or the like for the wiring, and even if it is long, there is no need for any support. A pipe-shaped arm 107 is used for this wiring. Note that the sensor unit mounting position is not limited to the lower link mentioned above, but also in the planting area 1 in front of it.
The side part of the bumper 103' of the 03 may be configured to obtain steering information more quickly. The data processing device 1 is a so-called microcomputer, and in this embodiment, a one-chip microcomputer 8748-8 manufactured by Intel Corporation in the United States, which is also equipped with a memory device, is used. The data processing device 1 is programmed to recognize the relative positional relationship between the planted seedlings and the machine body in the following manner. That is, depending on the planting process, the planted seedlings Z will come into contact with the contact rod group 8l or 8r of either the left or right sensor unit 80l or 80r, but in any case, only the leftmost contact rod 81 will come into contact with it. If the seedling comes into contact with the robot (that is, if only the output of the comparator 11 connected to the touch rod 81 is reversed and this is detected by the data processing device 1), it is recognized that the aircraft is largely biased to the right. . In other words, if the row of already planted seedlings is to the left (or right) of the aircraft, it is recognized that the aircraft is too far away from (or too close to) the row of already planted seedlings. Next, when the touch rods 81 and 82 come into contact with the planted seedlings, it is recognized that the aircraft is slightly biased to the right. Further, if the touch rods 82 and 83 are in contact with the planted seedlings, the machine maintains a desired distance from the row of planted seedlings and recognizes that the machine's position is normal. Furthermore, if a planted seedling comes into contact with the touch rods 83 and 84, the aircraft will be slightly biased to the right, and if a planted seedling comes into contact only with the touch lever 84, the aircraft will be greatly biased to the left. Recognize that there is. In this way, in the device of the present invention, the corresponding seedling sensors of the left and right sensor units, that is, the leftmost seedling sensor 81l of the left sensor unit 80l and the leftmost seedling sensor 81r of the right sensor unit 80r, are connected to each other.
The second seedling sensor 82l from the left of the sensor unit 80l and the same seedling sensor 82r of the sensor unit 80r are connected, and the third seedling sensor 83l from the left of the sensor unit 80l and the same seedling sensor 83r of the sensor unit 80r are connected. unit 8
Seedling sensor 84l and sensor unit 8 on the right side of 0l
Since the seedling sensors 84r and 0r are individually input to predetermined ports of the data processing device 1, the data processing device 1 can identify which of the left and right sensor units the seedling sensor is receiving a signal from. Although it is impossible to
Since it is possible to accurately detect the degree to which the steering wheel is biased to the right, automatic steering can be performed without any problems, as will be described later. Conventional devices of this type (however, unlike the device of the present invention, optical sensors are often used as seedling sensors) have sensor units on each side, but the planting process Each time a change is made, it is necessary to know whether the row of planted seedlings is on the left or right side of the aircraft during that process, and if the row of planted seedlings is on the left (or right) side of the aircraft, use the changeover switch to change the row to the left. (or on the right) and selectively input the output of that seedling sensor to the data processing device, or input the output of each seedling sensor of both sensor units individually,
A method has been adopted in which software is used to enable only the input from one of the sensor units and disable the other. Therefore, in any case, the hardware and software are more complicated than those of the present invention, and especially when input selection is performed manually using a change-over switch, etc., this change-over switch is difficult to use during circuits that require various operations. Although there was a problem that it was troublesome to operate without forgetting, this problem has been solved by the device of the present invention. Now, as mentioned above, once we have recognized the relative positional relationship between the row of planted seedlings and the aircraft, we can calculate the steering angle required to follow the row of planted seedlings according to each situation, as shown in Table 1. Decide accordingly.

[Table] However, the sign of the steering angle is positive, indicating steering to the left.
Let it be negative to indicate steering to the right, and let θ ₂ > θ ₁ . In addition, in order to prevent hunting in the control system and deterioration of riding comfort due to unnecessary steering, contact conditions between the seedling and the touch rod that do not apply to each of the cases 1 to 5 in Table 1. If this occurs, the steering angle is determined to be smaller (if there are four levers as in the embodiment, the steering angle is 0). For example, if only the touch rods 82 or 83 are touched, the value is 0, and if three of them, 81, 82, 83, or 82, 83, 84 are touched, the value is 0. In this way, seedling sensors 81l to 84l or 81r
When the steering angle is determined based on the combination of the outputs 84r, that is, the output pattern, the data processing device 1 issues steering control signals from the output ports P ₁₄ and P ₁₅ to realize this steering angle. The electronic circuit connected to these output ports P ₁₄ and P ₁₅ is the solenoid valve 2 in the hydraulic circuit for steering drive shown in Fig. 4.
This is a drive circuit for controlling the energization of the solenoids 2ls, 2rs, and 2cs of the respective solenoids 2ls, 2r, and 2c, and includes comparators 21l, 21r, and two PNP transistors 2 connected to Darlington, respectively.
It consists of 2l, 23l, 22r, 23r, etc. Output port P ₁₄ or P ₁₅ is at a high level when the determined steering angle is 0, and when the steering angle is +θ ₂ , +
When it becomes θ ₁ , −θ ₂ , −θ ₁ , it becomes low level. The steering control signal issued from this output port P ₁₄ or P ₁₅ is applied to the + input terminal of the comparator 21l or 21r, and a signal corresponding to the high/low level of the output port is output from the output terminal. will be issued. This signal is transmitted to one of the transistors 22 connected to Darlington.
It is designed to be input to the base of 1 or 22r. While the signal is at a high level, the transistor 22l or 22r is off, but when it changes to a low level, it is turned on, and accordingly, the other transistor 23l or 23r is also turned on. In this way, the transistor 23 turns on when the output port _P14 or _P15 becomes low level.
The emitter of 1 or 23r is at a positive potential +Vcc, and the collector is grounded to the body via solenoid 2ls or 2rs. On the other hand, one end of the solenoid 2cs is grounded to the body, and the other end is connected to the diode 24,
It is connected to the cathode of 25 and the anode of diode 26. The anodes of diodes 24 and 25 are connected to the collectors of transistors 23l and 23r, respectively, and the cathode of diode 26 is connected to the +Vcc line. Furthermore, connect the cathode of another diode 27 to the +Vcc line,
Further, the anode is connected to the collector of the transistor 23l. Therefore, the transistor 23l or 2
When 3r is turned on, solenoid 2ls, 2
Current is applied to both cs, 2rs, and 2cs. Next, the hydraulic circuit shown in FIG. 4 will be explained. 30
is a variable displacement hydraulic pump, and has a solenoid valve 2c.
and the left and right front wheels 3 through 2l and 2r, respectively.
Hydraulic motor 31l mounted directly on each of 2l and 32n
and 31r, and to the hydraulic motors 31'l and 31'r directly mounted on the left and right rear wheels 32'l and 32'r via the solenoid valve 2c to rotate them. Depending on the left front and rear wheels 32l, 32'
A hydraulic pump 3 is adapted to drive the right front and rear wheels 32r and 32'r, and whose oil flow direction and pressure oil supply amount are linked to a speed change lever 112 (see Fig. 1).
Adjustments are made using the movable swash plate 0, which allows selection of forward and backward movement and adjustment of travel speed. The solenoid valve 2c is a 3-port, 2-position switching type directional control valve, and when the solenoid 2cs is demagnetized, it is in the position shown in the figure, and is connected to the hydraulic motor 31l side and the planting part 1.
Pressure oil is supplied to the electromagnetic valve 2d for lifting and lowering control of 03. On the other hand, when the solenoid 2cs is energized, the supply of pressure oil to the electromagnetic valve 2d side is cut off, and the pressure oil is supplied to the hydraulic motor 31l, etc. side.
The solenoid valve 2d is a 3-port, 3-position switching type directional control valve, and when the solenoids 2ds ₁ and 2ds ₂ are demagnetized, it is in the position shown in the figure to seal off the pressure oil from the hydraulic pump 30 and to close off the pressure oil from the single-acting hydraulic cylinder 34. The oil chamber is sealed and the planted portion 103 connected to the piston rod of the hydraulic cylinder 34 is held at the current position.
On the other hand, when the solenoid 2ds ₁ is energized, the position is switched in the direction of the arrow, supplying pressure oil to the hydraulic cylinder 34, advancing the piston rod, and rotating the lift arm 106 upward to raise the planting section 103. let On the other hand, when the other solenoid _2ds2 is energized, the position is switched in the direction opposite to the arrow mark, so that the pressure oil in the oil chamber of the hydraulic cylinder 34 can be returned to the tank. As a result, the planting section 103 descends due to its own weight. On the other hand, the solenoid valve 2l or 2r is a two-position switching type stop valve, and when the solenoid 2ls or 2rs is demagnetized, the solenoid valve 2l or 2r is in the illustrated position.
Supply pressure oil to 1l or 31r and rotate it. On the other hand, when the solenoid 2ls or 2rs is energized, the position is changed and the supply of pressure oil to the hydraulic motor 31l or 31r is cut off, and its rotational drive is stopped and braking is applied. Therefore, when the solenoid 2ls or 2rs is energized, the left (or right) front wheel 32l or 32r stops rotating and the aircraft turns to the left (or right). When the solenoid 2rs is energized and excited, the solenoid 2cs is also energized, so the supply of pressure oil to the hydraulic system for raising and lowering the planting section 103, that is, the solenoid valve 2d side, is cut off, so that all the pressure oil is transferred to the hydraulic motor 31r. It is supplied to the side such as 31l or 31l and increases its rotational speed, resulting in a powerful turn to the left (or right). Note that while such steering is performed, pressure oil is not supplied to the hydraulic cylinder 34, so if the planting section 103 is being driven upward, the upward movement is temporarily stopped, but automatic steering is not performed. During this period, the planting is in progress, and there is no need to drive the planting section 103 upward, so there is virtually no problem. In addition, 35 is a pressure relief valve, and 36 is a charge pump. Now, returning to FIG. 3 again, comparators 21l, 21
Switches 28l and 28r are interposed between the output terminals of r and the body ground, respectively. The switch 28l or 28r is arranged so as to close the circuit when the steering wheel 101 is rotated to the left (or right) by an appropriate amount.
With the output terminal of 1l or 21r set to low level,
Transistor 22l, 23l or 22r, 23r
This turns on solenoid 2ls or 2
The rs has been energized and can now be operated manually. In this way, for manual steering, it is sufficient to simply close the switches 28l and 28r, so there is no need to provide the steering wheel 101, and the above-mentioned switch 2 can be operated as a push button switch on the operation column 111.
8l and 28r may be provided. Now, 41 is a steering sensor for detecting the actual steering angle of this rice transplanter. That is, the fuselage of this rice transplanter is of a folding type, and the front fuselage F relative to the rear fuselage R is rotated at the pivot joint 113 between the front fuselage F and the rear fuselage R.
In order to capture the angle of horizontal rotation, that is, the steering angle,
It is composed of a potentiometer that changes the output voltage according to the amount of horizontal rotation of the front body F. The output voltage of this steering sensor 41 is a timer IC (555 type)
The signal is inputted to a V/F (voltage/frequency) converter 42, and the signal subjected to V/F conversion is inputted to the input port _T1 of the data processing device. With this input signal, the data processing device 1 can detect the actual steering state based on the steering control signals from the output ports P ₁₄ and P ₁₅ . Then, the data of the steering angles ±θ ₁ and ±θ ₂ determined as described above and stored in appropriate registers and the actual steering angle inputted from the steering sensor 41 via the V/F converter 42 are used. If the data of the angle of entry match, the output port P ₁₄ ,
The output of P ₁₅ is returned to high level, and the state of straight-line driving is restored. The operation column 111 is provided with a switch for switching between manual and automatic steering modes and a condition adjustment mode selection switch 85. When the former switch is set to automatic mode, data processing device 1
The signal AUTO is input to the solenoid _2ds2 , and predetermined initial operations are performed, including the lowering of the planting section 103 by energizing the solenoid 2ds2, and then the automatic steering as described above is performed. Since the automatic steering is performed by following the rows of already planted seedlings, the first step is of course performed in manual mode, and the automatic mode is selected in the subsequent steps. Now, when moving on to the next step, the steering wheel 101 is what turns the aircraft around.
This is done by rotating the During this time, the manual-automatic mode selector switch may be left in automatic mode. The touch rod of the seedling sensor does not touch the seedling, and its output signal connects the output ports P ₁₄ and P _15.
does not fall to a low level, so automatic steering is not performed.However, when the switch 28l or 28r closes as the steering wheel 101 rotates, the solenoid 2ls or 2rs is energized and the aircraft can turn in the desired direction. It is from. Now, after completing this rounding operation, in order to perform automatic steering that follows the row of seedlings planted in the previous step, it is necessary to align the rows by positioning the left or right touch rod group 8l or 8r in this row of seedlings. . Since the width of the group of touch rods is about 150 mm, it is possible to adjust the alignment by manual steering, but in order to reduce the burden on the driver, the device of the present invention is designed to automatically adjust the alignment. As shown in Fig. 5, the machine is now in a position in front of the right hand side of the group of already planted seedlings, and the touch rod group 8l of the left sensor unit 80l is aligned from the left side of the machine with the row of planted seedlings Y closest to the untransplanted area. shall be. At this point, the row matching mode selection switch 85 is turned on to input a signal for commanding row matching. Then, a short-time condition matching command signal JCS is input to the interrupt terminal of the data processing device 1, and the data processing device 1 enters the process routine of the condition condition mode. In this mode, the data processing device 1 detects seedling sensors 81l and 82l of the sensor unit 80l on the left and 83 on the right.
1 and 84l, and the signals from the seedling sensors 81l and 82l recognized as being on the left, that is, the signals input to ports P ₁₀ and P ₁₁ , are invalidated at least for steering control. shall be. In other words, steering control is prohibited. After the seedling sensors 83l and 84l classified as those on the right side detect the presence of already planted seedlings, the row alignment is completed and the outputs from all the seedling sensors 81l to 84l are made valid, that is, the steering control is performed. It is designed to work to remove the ban. In other words, when the aircraft approaches the group of already planted seedlings from the right front, the seedling sensor 81l will first detect the nearest seedling _Y1 in the row of already planted seedlings Y, and the automatic steering will take place according to this situation. If it is decided to allow this, it will not only be impossible to align the rows by turning to the left as shown by the two-dot chain line in Figure 5 according to Table 1, but it will also damage the already planted seedlings. However, in the device of the present invention, the signals from the seedling sensors 81l and 82l are disabled, so the aircraft will continue to go straight for a while. Therefore, the seedling sensors 83l and 84l will detect any of the seedlings in the already planted seedling row Y at a relatively early point in time, and after this point of detection, the row alignment mode will return to the normal automatic steering mode, so the aircraft is then turned to the right as shown by the solid line in FIG. 2, and travels with the group of touch rods 8l aligned with the rows of seedlings Y, making it possible to align the rows without difficulty. By the way, in the above embodiment, the sensor unit 80
1 and the sensor unit 80r which emits a seedling detection signal when the rows are joined from the front left of a group of already planted seedlings, the seedling sensor whose output should be disabled is reversed. That is, it is necessary to initially disable the seedling sensor output on the outside of the body. Therefore, only in the case of row alignment, it is necessary to give a signal to distinguish and indicate whether the planted seedlings are on the left or right side of the machine. However, in the embodiment to be described next, this is not necessary, and identification and recognition of the sensor units 80l and 80r is not required as in the case of steering. That is, in the second method, when the data processing device 1 is in the row combining mode, the two (or one is fine) seedling sensors 82l and 83 in the center of the sensor unit are activated.
Until one of the sensors 1, 82r, and 83r detects a planted seedling, all outputs from each seedling sensor are invalidated for steering control. In other words, if only the seedling sensors 81l, 84r, etc. at the ends are detecting seedlings, steering control is prohibited, and the seedling sensors 81l, 84r, etc. at the center
This prohibition is canceled when 1, 83l, 82r, and 83r detect a seedling. Therefore, it goes without saying that the steering of the aircraft during row alignment is performed in almost the same way as the first method described above, but it is completely unrelated to the fact that there are groups of already planted seedlings on either the left or right side of the aircraft. Data processing will be performed in advance, reducing the burden on the driver and saving on hardware and software. As described in detail above, according to the present invention, it is possible to accurately travel along the rows of already planted seedlings, and the row alignment can be performed automatically, and it is also possible to automatically follow the rows of already planted seedlings, regardless of whether the rows of already planted seedlings are on the left or right side of the machine. This has the advantage that steering control can be performed without the need for specific operations. In the case of using the second method, there is no need to perform any operation to identify the rows of already planted seedlings, regardless of whether they are on the left or right side of the machine, even when rows are being aligned, so there is no burden on the driver during transplanting work. The present invention has excellent effects, such as being able to significantly reduce the In the above-mentioned embodiment, the number of seedling sensors was four on one side, but it may be an appropriate number of two or more on one side.
In particular, if the row matching function is not considered, one on each side may be used. If there is only one rod, the relative positional relationship may be recognized based on the proportion of time that the seedling is in contact with the rod. In other words, this seedling sensor provides an output pattern of constant contact, intermittent contact, or non-contact, and in the case of an intermittent contact output pattern, it can be classified based on its duty ratio. Assuming that there is a row of planted seedlings on the left side of the aircraft, if you initially set the touch rod to approach the row of planted seedlings from the left, in the case of constant contact, it will be too far to the left, and in the case of intermittent contact, the duty For example, when the ratio is greater than 1/2, it is on the left;
If it is 1/2, it is appropriate, if it is smaller than 1/2, it is to the right, and if there is no contact, it is determined to be too far to the right.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a left side view of a rice transplanter equipped with the device of the present invention, FIG. 2 is a perspective view of a group of touch rods, and FIG. FIG. 4 is a block diagram schematically showing the main parts of the electronic circuit of the apparatus, FIG. 4 is a circuit diagram schematically showing the main parts of the hydraulic system, and FIG. 5 is an explanatory diagram of the arrangement. 1...Data processing device, 80l, 80r...Sensor unit, 81l-84l, 81r-84r
...Seedling sensor, 85...Row combination mode selection switch.

Claims (1)

[Scope of Claims] 1. In an automatic steering device for a transplanter that detects the relative positional relationship between the already planted seedlings and the machine body and causes the machine to travel following the rows of already planted seedlings, A sensor unit is provided in which a plurality of seedling sensors are arranged side by side in the left and right direction of the machine, and the outputs of the corresponding seedling sensors of the left and right sensor units are respectively The data processing device is configured to collectively input the output to a data processing device that performs steering control based on the output, and when the data processing device inputs a signal instructing the alignment, the left (or right) When aligning rows to already planted seedlings from the left (or right) side, the seedling sensors in the left (or right) sensor unit are classified into those on the left and those on the right, and ), the above-mentioned steering control is prohibited when only the output from the seedling sensors classified as An automatic steering device characterized in that it operates to cancel prohibition of control. 2. In an automatic steering device for a transplanter that detects the relative positional relationship between the planted seedlings and the machine body and causes the machine to travel in a manner that follows the rows of planted seedlings, by contacting the planted seedlings on the left and right sides of the machine body, A sensor unit is provided in which a plurality of seedling sensors that detect the presence and output a predetermined signal are arranged side by side in the left and right direction of the machine, and the outputs of the corresponding seedling sensors of the left and right sensor units are collectively sent to the The output is configured to be input to a data processing device that performs steering control, and when the data processing device receives a signal instructing row alignment, the data processing device inputs the seedlings at the left and right ends of each sensor unit. The steering control is prohibited when only the output from the sensor is obtained, and the prohibition of the steering control is canceled after one or two seedling sensors in the center detect the presence of already planted seedlings. An automatic steering device that is characterized by what it does to encourage people to do so.