JPH1039927A - Position calculation method for automatic guided vehicle operation - Google Patents

Abstract

(57) [Problem] To restrict conditions for an arithmetic method for measuring a posture angle using a gyro and calculating a position from an amount of rotation of a wheel of a carrier in an area where guidance control of the automatic guided vehicle cannot be performed. The present invention provides a position calculation method at the time of autonomous operation of an automatic guided vehicle, which can calculate at high speed. SOLUTION: In the position calculation method of the automatic guided vehicle 1 which performs the autonomous operation based on the attitude angle of the gyro 4 mounted on the automatic guided vehicle 1 and the moving distance, the calculation of the measured value of the attitude angle is performed by the attitude angle. Sine and cosine are calculated at high speed by referring to a table.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for calculating the position of an automatic guided vehicle during autonomous driving.
The present invention relates to a position calculation method for an autonomous guided vehicle in which autonomous driving is performed at high speed and with high accuracy by measuring the position of the guided vehicle using a gyro and an encoder in a portion where optical guidance cannot be performed.

[0002]

2. Description of the Related Art Conventionally, as a method of unmannedly transferring and transporting articles along a predetermined course in a factory or a warehouse, a guideway is formed on a floor surface of a factory or the like along a traveling course, and the guideway is formed. The automatic guided vehicle travels by detecting the road with a sensor mounted on the automatic guided vehicle, stops at the station position,
It is designed to transfer goods. As the guide path, a magnetic guide using a magnetic tape and an optical guide using a reflective tape are generally employed. Parts such as corners where a taxiway cannot be laid on the floor are driven by an autonomous driving device mounted on an automatic guided vehicle.

[0003]

As described above, the position calculation at the time of autonomous operation in the conventional automatic guided vehicle is performed by MPU (MicroP
Integer operation is performed by using a rocessing unit. However, in general, the time of integer operation is longer than that of floating point operation.
The operation can be performed at high speed, and the processing time of addition and subtraction in integer operation is shorter than that of multiplication. Further, in multiplication and division, the processing time of multiplication is shorter. Therefore, in order to execute the operation at a high speed, it is necessary to reduce the number of time-consuming division and multiplication operations, to carefully select an algorithm, to reduce the number of repetition operations and the like, and to shorten the operation time. Further, in real-time control for machine control, even when the calculation time is critical, the calculation must be performed within a fixed time during which the system operates stably and output as a control output.
Therefore, there is a demand for an operation method in which the operation time is short and the operation time is determined even under the worst conditions. The present invention solves the problems of the position calculation method of the conventional automatic guided vehicle during autonomous driving described above, and measures an attitude angle using a gyro, an area in which guidance control of the automatic guided vehicle cannot be performed, and a wheel of the guided vehicle. It is an object of the present invention to provide a position calculating method for autonomous operation of an automatic guided vehicle, which can calculate a position from an amount of rotation of the automatic guided vehicle at a high speed by limiting conditions.

[0004]

In order to achieve the above object, a position calculation method of an automatic guided vehicle according to the present invention at the time of autonomous driving is provided. In the position calculation method performed during autonomous operation of the automatic guided vehicle, the measurement of the posture angle is calculated at high speed by referring to a table with the sine and cosine of the posture angle.

[0005] In the position calculation method of the present invention having the above configuration during autonomous operation of the automatic guided vehicle, autonomous operation can be performed even in an area where guidance control cannot be performed.

In addition, the method of calculating the position of an automatic guided vehicle during autonomous operation according to the present invention is a method of calculating the position of an automatic guided vehicle that performs autonomous operation based on the attitude angle of a gyro mounted on the automatic guided vehicle and the moving distance. The method is characterized in that the calculation is performed while limiting the range of autonomous driving.

In the position calculation method for the automatic guided vehicle of the present invention having the above-described configuration, the calculation can be performed without causing the calculation overflow.

Further, the method of calculating the position of an automatic guided vehicle during autonomous operation according to the present invention is a method of calculating the position of an automatic guided vehicle that performs autonomous operation based on the attitude angle of a gyro mounted on the automatic guided vehicle and the moving distance. The method is characterized in that the operation is a high-speed operation in a binary representation in a microcomputer.

In the position calculation method for the automatic guided vehicle of the present invention having the above configuration, the position of the automatic guided vehicle is measured by an encoder and a gyro, and the measured value is calculated at a high speed by a microcomputer. Therefore, the autonomous operation of the automatic guided vehicle can be performed accurately and at high speed.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an automatic guided vehicle position calculating method according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes an automatic guided vehicle that automatically travels along a guideway laid on the floor in advance. The automatic guided vehicle 1 is provided with traveling wheels W and a driving device 10 as in the conventional case. And a power supply and a control device. In addition, magnetic tapes 5 and 6 are laid on the floor along a traveling path on which magnetic tapes 5 and 6 are set. In the illustrated embodiment, this tape is a magnetic tape, but it may be a reflective tape.

The magnetic tapes 5 and 6 are laid on a floor along a predetermined traveling path, and are generally attached to the floor. In this case, a portion where the magnetic tapes 5 and 6 cannot be attached, for example, a curved road or the like as shown in FIG. An autonomous device mounted on the automatic guided vehicle 1 automatically travels along the determined autonomous driving locus 7.

As a sensor for autonomously driving an area where guidance control of the automatic guided vehicle 1 cannot be performed, an optical fiber gyro utilizing the Sagnac effect at the center of the body of the automatic guided vehicle 1 or a Coriolis force acting on a piezoelectric element Gyro 4 that measures the attitude angle of a vehicle body such as a piezoelectric gyro using
And encoders 2 and 3 are arranged on the wheels W in order to measure the amount of movement of the vehicle body of the automatic guided vehicle 1.

The gyro 4 detects the angular velocity of rotation and obtains an angle by integrating the detected value, and the encoder provided on the wheel W is disposed on two different wheels, as shown in the figure. It is disposed on the front and rear wheels or on the left and right two wheels when the automatic guided vehicle 1 is steered by the speed difference between the left and right two wheels. An arithmetic unit (microcomputer) using a general-purpose MPU is provided to determine the moving distance of the automatic guided vehicle 1 by averaging the pulses generated by the two encoders 2 and 3, and to calculate the position of the automatic guided vehicle 1. Is what you do.

Further, an autonomous operation start mark 8 is provided on the floor surface along the end position of the magnetic tape 5, and the autonomous operation start mark 8 is formed of a permanent magnet, an iron plate, or the like, and is embedded in the floor surface. At the same time, a sensor 9 is provided on the automatic guided vehicle side at a position where the automatic guided vehicle 1 traveling along the magnetic tape 5 can detect when the automatic guided vehicle start mark 8 is reached.

Next, the automatic guided vehicle 1 constructed as described above
Will be described. In the section where the guidance control of the automatic guided vehicle 1 can be performed, guidance control (magnetic guidance) using the magnetic tapes 5 and 6 is performed. The automatic guided vehicle 1 is a driving device 1 such as a motor.
When both the front wheels and the rear wheels are driven at 0, the encoders 2 and 3 are attached to the front and rear wheels W, so that the wheels W are rotated by the movement of the automatic guided vehicle 1, and the encoders are rotated by the rotation of the wheels. The amount of movement is measured, and the gyro 4 attached to the center of the vehicle body measures the attitude angle at a predetermined constant cycle.

In this way, the generated pulse value generated by the encoder in accordance with the amount of movement of the automatic guided vehicle 1 and the attitude angle by the gyro 4 are measured at predetermined fixed cycles, respectively. The vehicle 1 travels along the guide path formed by the magnetic tape 5 and eventually reaches the end of the magnetic tape 5 to detect the autonomous operation start marker 8 with the sensor 9. From this marker detection position, the automatic guided vehicle 1 starts autonomous operation. After the start, the operation is performed according to the autonomous operation locus 7 set in advance, and the operation is performed so as to reach the next magnetic tape 6. Automatic guided vehicle 1
Reaches the position of the magnetic tape 6 and thereafter travels along the magnetic tape 6 again under the guidance control by the magnetic tape 6.

A method of calculating a section in which autonomous driving is performed after the detection of the marker will be described with reference to the coordinates shown in FIG. With the position and direction of the vehicle body when the autonomous driving start marker 8 is detected as an initial condition, this time is set to t0, and the position is set to p0. Thereafter, the attitude angle θ and the moving distance L are measured at intervals of a constant period Δt. Number of measurements
Assuming that the movement distance is ΔLn for n posture angles θn and Δt, the position Pn is given by the following equation.

[0019]

(Equation 1)

The traveling distance of the automatic guided vehicle 1 is determined by a front wheel W and a rear wheel W.
And the measured values of the front wheels W are Lfn,
Assuming that the measured value of the rear wheel W is Lrn, the moving distance ΔLn is given by the following equation.

[0021]

(Equation 2)

The measured value of the gyro angle is represented by a word length w1 bits expressed in two's complement and an effective precision w2 bits.
As an example, 2w1 = 16 bits, effective precision w2 = 15 bits, and position calculation is performed with a fixed decimal point having a word length of 32 bits. FIG. 3 shows the display of the gyro angle. This results in Equation 3.

[0023]

(Equation 3)

This equation shows that the range that can be expressed by positive and negative is different by one. Angle display resolution in this example
Ra is given by the following equation.

[0025]

(Equation 4)

The method of converting gyro data into 32-bit word length data is as shown in FIG. That is, w1 bits are copied as they are from the least significant bit to the most significant bit in the 32-bit data area. bitw1 to bit31
During the period, the value of bit w1 is copied for 31- (w1-1) bits.

In an assembly language of a general-purpose MPU, data conversion is generally performed from 8 bits to 16 bits, and from 16 bits to 32 bits.
Bit data conversion can be executed by a single instruction as a word length extension instruction. If w1 is not an integral multiple of 8 such as 8 or 16, the word length is extended according to the above method.

In calculating the position, the sine (sin) and the cosine (cos) of the angle data output from the gyro are required. To reduce the calculation time, a table is provided with each angle as an argument. Since the effective precision of the gyro is w2 bits, the size of the table ^only needs to be 2 ^{w2 + 1} . Gyro angle accuracy is w2 bits, while table accuracy is w3 bits (w2> w3)
It is possible to lower.

The sine table is sin_tbl [n], and the cosine table is cos_
tbl [n], and the subscript range is a value of n = 0, 1, 2,..., 2 ^{w2 + 1} −1. If w2 = 15 bits, n = 0,1,2 ,,, 65535. The precision that this table can represent is 2
^{When w2 + 1} , the operation precision is sufficient if it has w2 bit precision. The relationship between the trigonometric function value and the angle can be approximated as sin θ = θ and cos (π / 2 + θ) = θ when the angle θ is small, and the accuracy is most required in the vicinity of this, but the function value is larger than the angle used as the argument. This is because it cannot be. The function value stores the following value for the subscript n of the array as an argument. When compressing the precision of the table to w3 bits, w2 = w3
Becomes This table does not need to be created in real time, but is created in advance, stored in a non-volatile memory such as a ROM (Read Only Memory), and referred to as needed.

[0030]

(Equation 5)

When the gyro output data is An, the angle θ _n when the gyro data is sampled n times is as follows. The function value of the trigonometric function can be obtained in a very short time by referring to the table as a subscript of the array with a value obtained by adding a constant to the value of the output data of the gyro.

[0032]

(Equation 6)

Next, measurement of the moving distance by the encoder will be described. As an example, the radius of the wheel W of the automatic guided vehicle is r = 100 mm, and the traveling speed of the automatic guided vehicle is v = 1 m
/ S, the number of pulses generated per rotation of the encoder wheel is RP = 2000 pulses / rev, and the data sampling interval is Δt = 50 ms. The resolution R of the distance measurement of the encoder is as follows. The counting by the encoder can be performed at 90 ° or 180 ° of the generated pulse, and in this case, the resolution is doubled or quadrupled.

[0034]

Equation 7

The relationship between the pulse P generated by the encoder and the distance L is L = PR.

The time period during which the autonomous operation is performed is limited by limiting the area in which the autonomous operation is performed, and the number of pulses S generated by the encoder during this time is at most as follows.

[0037]

(Equation 8)

The number of pulses generated by the encoder is an integer value, and the table of trigonometric function values is a fixed-point expression with w2 bits below the decimal point. If the section of the autonomous driving is limited and the time is limited by T, overflow during calculation does not occur. This is, as shown in the following equation,

[0039]

[Equation 9]

This is because they fall within the range of numerical values that can be represented by data having a word length of 32 bits. The reason why the generated pulse is evaluated with a value twice the maximum number of generated pulses is to eliminate the division and shorten the calculation time, as described later.

In the position calculation, the x coordinate x _n and the y coordinate yn at the position where the number of times of sampling is _n are as follows.

[0042]

(Equation 10)

The position P _{0 at} which the autonomous driving starts is represented by P
₀ (0,0), comprising a change in position during autonomous operation as follows, if indicated by the form of 2P _n.

[0044]

[Equation 11]

The operation of this equation comprises addition and subtraction and multiplication of integers, and there is no division. General-purpose MPU
No need for time-consuming floating-point operations. Further, it is not necessary to verify the branch in the condition determination and the overflow in the operation process, and the operation can be performed at an extremely high speed.

[0046] In the case lower the accuracy of the calculation to w3 bits w2 bits, or when obtaining the position P _n rather than 2P _n, the bit arithmetic right shift instruction with the MPU 1
A bit in a word is moved from the upper bit to the lower bit by moving the bit while maintaining the value of the most significant bit.
, And the high-speed operation is not lost in this case.

[0047]

According to the position calculation method of the automatic guided vehicle of the present invention during autonomous operation, it is possible to operate autonomously even in an area where guidance control cannot be performed. According to the second aspect of the present invention, the calculation can be performed without causing the overflow of the calculation. According to the third aspect of the present invention, the position of the automatic guided vehicle is measured by the encoder and the gyro, and the measured value can be calculated at a high speed by the microcomputer, so that the autonomous operation of the automatic guided vehicle can be accurately performed. , And at high speed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an embodiment of a position calculation method for an automatic guided vehicle during autonomous operation according to the present invention.

FIG. 2 is an explanatory diagram illustrating a relationship between coordinates for calculating a position of a section in which autonomous driving is performed.

FIG. 3 is an explanatory diagram showing a display method of a gyro angle.

FIG. 4 is an explanatory diagram of an extended word length of gyro data.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Unmanned guided vehicle 2 Encoder 3 Encoder 4 Gyro 5 Magnetic tape 6 Magnetic tape 7 Autonomous operation locus 8 Autonomous operation start marker 9 Sensor 10 Motor W Wheel

Claims (3)

[Claims] 1. A method for calculating a position of an automatic guided vehicle that performs autonomous operation based on a posture angle of a gyro mounted on the automatic guided vehicle and a moving distance, the method includes calculating a measured value of the posture angle by using a sine of the posture angle. And calculating the cosine at high speed by referring to a table during autonomous operation of the automatic guided vehicle. 2. A method for calculating the position of an automatic guided vehicle that performs autonomous operation based on the attitude angle of a gyro mounted on the automatic guided vehicle and a moving distance, wherein the calculation is performed while limiting the range of the autonomous operation. A method for calculating the position of an automatic guided vehicle during autonomous driving. 3. A position calculating method for an autonomous guided vehicle that performs autonomous driving based on a posture angle of a gyro mounted on the automated guided vehicle and a moving distance, the calculation is performed by a microcomputer.
A position calculation method for autonomous operation of an automatic guided vehicle, wherein high-speed calculation is performed in a hexadecimal representation.