JPH0836054A - Safety system of working machine - Google Patents

Abstract

PURPOSE:To avoid radio interference among transceivers and to prevent an accident due to collision at a site where a plurality of working machines and workers are mixedly exist, by transmitting a microwave frequency-modulated by the variable pattern of the graph of a broken line to a transponder. CONSTITUTION:A function-generating ROM 31 memorizes various variable patterns in addition to the variable pattern of the graph of a broken line for connecting to a control voltage-generating circuit 11. An MPU 32 selects and reads the variable pattern from the ROM 31 FOR D/A conversion 11a. The variable pattern is then applied to a VCO 12 to change the frequency of a transmitting signal along a straight line. After a predetermined period of time, a transmitting wave sweeped to successively change the decline of the straight line is generated to be transmitted to a trasponder 20 (worker). Thus, mutual radio interference is avoided from the difference in the timing of transmission starting even if a plurality of transceivers (working machines) selects the same transmitting pattern. Each transceiver exactly detects the distance to the transponder 20 to prevent collision.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a work machine safety system. More specifically, a plurality of construction machines are working in a transponder type microwave distance sensor mounted on a construction machine as a safety system. The present invention relates to a safety system for a construction machine that can measure the distance to the worker without interference with other construction machines and can ensure higher safety.

[0002]

2. Description of the Related Art At construction sites, road pavement sites, civil engineering work sites, etc., there are many work modes in which construction machines and workers cross each other. In addition, depending on the location, general people also visit or carry in and carry out various machines used in association with work, and also obstacles. If these workers, ordinary people, obstacles, etc. are in a construction method or in a direction that obstructs the field of view of a driver of a work vehicle or the like, the risk of an accident is extremely high. Therefore,
Therefore, ensuring safety is important. Therefore, various sensors for detecting the position of the other party have been studied, and one of them is a construction machine equipped with a distance sensor using a transponder type microwave.

However, this type of microwave distance sensor mounted on a construction machine is in full-scale application and practical use. On the other hand, taking a hydraulic excavator at a construction site as an example, an operator who operates the hydraulic excavator and a worker who performs auxiliary work around the machine jointly perform construction work. In such a case, it is necessary to secure sufficient safety for work by using the microwave distance sensor. For example, in a hydraulic excavator, a microwave transceiver (transceiver) is mounted on the shovel side, and an operator wears the transponder by attaching it to a helmet or the like. Transmission and reception are performed between these, and the position of the worker is monitored. This informs the operator of the hydraulic excavator that the operator has approached the dangerous area of the hydraulic excavator, and automatically stops the machine as necessary in order to prevent a contact accident between the machine and the operator.

A transponder type distance sensor utilizing microwaves is a system in which information is exchanged by transmitting and receiving microwaves between a main station (transceiver) on the working machine side and a slave station (transponder) on the worker side. In this method, the slave station receives a transmission signal of the microwave transmitted from the master station, and transmits a microwave obtained by applying processing such as amplification and modulation to the reception signal of the microwave as a reply signal. The master station receives the reply signal by the microwave from the slave station, obtains the distance to the slave station, and monitors the worker based on this distance.

The method for measuring the distance between the master station and the slave station is
There are a pulse radar method and a phase difference method. The pulse radar method
This is a general method, which is a method for obtaining the distance based on the elapsed time until the pulse transmitted from the master station is returned by the slave station and returns. On the other hand, the phase difference method is a method for obtaining the distance based on the phase transition of the signal transmitted from the master station and returned by the slave station, and has high measurement accuracy.

A distance measuring device for measuring the distance between a master station and a slave station by the phase difference method under the transponder system and a distance calculation formula are described in Japanese Patent Publication No. 63-501981.
This will be summarized and described with an example applied to a hydraulic excavator. In FIG. 6, the main station 100 is provided at the rear of the hydraulic excavator 1, and the slave station 200 of the worker's helmet is attached.
FIG. 6 is a block diagram of a distance measuring circuit of a master station 100 and a circuit of a slave station 200 when measuring a distance d0 (see d0 in FIG. 5) between them. FIG. 7 is a waveform diagram illustrating a transmission signal and a signal having a phase difference. In the block diagram of FIG. 6, the receiving circuit and the transmitting circuit are omitted for simplification.

The distance measuring circuit of the main station (transceiver) 100 generates a transmission signal B whose frequency increases and decreases in the range of Δf (= 30 MHz) according to the triangular wave A (see (a) of FIG. 7), and transmits the transmission signal. B is transmitted from the transmission antenna 103 by microwaves. The slave station (transponder) 200 receives the transmitted microwave with the receiving antenna 201, and uses the received signal C as the oscillation signal P from the oscillation circuit 202 of 100 kHz.
Signal D mixed and modulated by the mixing circuit 202
Is transmitted from the transmission antenna 204 as a microwave. The modulation frequency here is not limited to 100 kHz, and is selected from the frequency range of about 100 kHz to 800 kHz.

Further, the distance measuring circuit of the master station 100 receives the microwave from the slave station 200 at the receiving antenna 104, mixes the received signal E with the transmitted signal B, and then 95 to 10
A separation signal F is separated and generated by a 5 kHz band pass filter (BPF) 106. On the other hand, the reference oscillation signal Q of 100 kHz is independently generated, and the phase difference between the reference oscillation signal Q and the separation signal F is taken to be the phase difference signal G (see FIG. 7B). Here, the amount of change (slope) of the phase difference G is detected.
This change amount, in other words, the slope for the phase difference G is
It represents the distance d0 between the transponder 200 and the master station 100. This slope is a function of the current sweep frequency of the VCO 102 and the sweep frequency at the time of transmission, and corresponds to the round-trip propagation time of the microwave to the transponder 200. Therefore, when the amount of change Δφ 0 of the phase difference signal G corresponding to the increase / decrease of the transmission signal B is obtained, the distance calculation formula d 0 = ((c × Δφ 0) /
(2 × 2π × Δf)), from the master station 100 to the slave station 2
The distance d0 to 00 is obtained.

Here, c is the speed of light, and this distance calculation formula is a function (2π ×) in which the phase transition amount φ of the oscillation signal P accompanying microwave propagation includes the frequency f and the distance d from the basic equation of wave propagation. f × 2 × d / c). That is, the basic distance calculation formula is d = ((c × φ) / (2 × 2π
Xf)). However, only with this, since the absolute phase of the oscillation signal P in the slave station 200 located at a position distant from the master station 100 cannot be grasped on the master station 100 side even if the frequency f is known, the distance cannot be immediately obtained. . In addition, the directly detectable phase has an uncertainty with a period of 2π. Therefore, the equation is modified so that the absolute phase is unnecessary and a deterministic distance is obtained. That is, the frequency f
The frequency difference Δf and the phase difference Δφ at two points.
The following distance calculation formula (1) using is used. d = ((c × Δφ) / (2 × 2π × Δf)) ………… (1)

In addition, the ratio (Δφ 0 /
When the portion of Δf) is replaced with the ratio of the rate of change of the phase difference signal G and the rate of change of the transmission signal B at the moment, the distance calculation formula for obtaining the distance at the moment is established. Also by this formula, the distance from the master station 100 to the slave station 200 is continuously obtained, and the distance can be obtained with high accuracy by averaging this (FIG. 7 (c)). By measuring the distance between the master station and the slave station via the microwave as described above, the worker wearing the slave station can be monitored while being distinguished from other obstacles.

[0011]

[Problems to be Solved by the Invention] At a work site, a plurality of working machines such as a hydraulic excavator and a crane work simultaneously,
Work is common. In such a case, if multiple work machines perform distance measurement in the same frequency band, workers with the same transponder (slave station) will be simultaneously accessed from multiple master stations and receive transmitted waves. As a result, interference may occur internally and an accurate transmission signal may not be sent out from the transponder. In such a case, the main station cannot measure the distance accurately, and there is a high risk that the safety of the worker cannot be ensured.

In order to avoid such a situation, it is conceivable to assign or change each frequency band according to each work machine, but this requires frequency management, and the band to which the frequency is assigned is limited. Therefore, there is a limit to the number of frequencies that can be managed. An object of the present invention is to solve the above-mentioned problems of the prior art. Even in a work environment where a plurality of work machines work at the same time, distance measurement can be performed without mutual influence, and safety can be improved. To provide a safety system for work machines that can secure

[0013]

The features of the safety system of the working machine of the present invention for achieving the above object are as follows.
The transmitter transmits a transmission signal whose frequency increases or decreases sequentially within a prescribed frequency range, and the transponder that receives this modulates the received signal with the prescribed signal and transmits it to the transmitter side. By mixing the transmission signal with the reception signal from the transponder, the distance from the transmitter to the transponder is calculated by detecting the rate of change of the phase of a predetermined signal, and an alarm etc. is generated according to the position of the transponder. In a work machine having a system, a control circuit that continuously increases or decreases the frequency of a transmission signal along a straight line and sequentially changes the slope of the straight line after a predetermined time, and a detection circuit that detects a rate of change in phase And a distance calculating means for calculating the distance based on the output of the detection circuit and the inclination of the straight line when the output is obtained.

[0014]

As described above, if a transmission wave having a frequency modulated according to a linear function having a different slope is generated and transmitted to the transponder, the transponder simultaneously transmits the transmission waves from a plurality of work machines. Even if received, the respective working machines do not operate in synchronization with each other, and therefore transmission waves of the same frequency are hardly generated at the same timing at the same time. Therefore, the transponder can simultaneously receive transmission waves of independent frequencies and send back to each, and the transceiver (each work machine) side can independently measure the distance to the transponder. Note that even if the frequencies of the transmitted waves from multiple work machines are instantaneously or temporarily in the same state, the main station side of each work machine calculates the distance based on the rate of change in phase, which causes a problem. Does not occur. By the way, a straight line having each inclination set after the predetermined time is stored in a plurality of tables as pattern data composed of a series of straight lines and the inclination, and one of the pattern data may be selected. In this case, it is not necessary to select the same control pattern for each work machine, so it is possible to more surely avoid overlapping of frequencies of transmitted waves. As a result, the safety of the worker can be ensured even in a work environment in which a plurality of work machines work simultaneously.

[0015]

1 is a system configuration diagram of a microwave distance sensor mounted on a construction machine to which a work machine safety system of the present invention is applied, and FIG. 2 stores a modulation pattern for increasing or decreasing a transmission frequency. Explanatory drawing of table, FIG. 3
FIG. 4 is an explanatory diagram of a relationship such as an increase / decrease function of a transmission frequency and a rate of change of phase, FIG. 4 is an explanatory diagram of transmission signals from a plurality of work machines, and FIG. 5 is an explanatory diagram of a relationship between a transceiver and a transponder. . As shown in FIG. 5, the transceiver 10 is attached to the rear portion of the hydraulic excavator 1, while the transponder 20 is attached to the helmet of the worker 2. Incidentally, 1a is another hydraulic excavator. Transceiver 1
0 has an arithmetic circuit for measuring the distance d0 from the transponder 20, and sends the calculated distance d0 to the control device 4 of the cab 3. The control device 4 compares the distance d0 with a predetermined reference value and determines that the transponder 20 has a distance greater than a predetermined value.
When the (worker) is approaching, an alarm device in the driver's cab 3 of the hydraulic excavator 1 in which the operator is present is driven to display a danger display on the display provided in the driver's cab 3.

As shown in FIG. 1, the transceiver 10 is provided with a transmitting antenna 10a and a receiving antenna 10b, and a frequency control oscillator (VCO) 12 has a frequency within a predetermined frequency range as time passes. A signal A ′ having a so-called swept frequency (which will be described later) that sequentially increases or decreases with (here, microwave) is generated and sent to the transmission circuit 13 to transmit the signal.
A microwave is transmitted from 0a, and the receiving antenna 10
b receives the same microwave signal. The radio wave from the transceiver 10 is received by the antenna 20a of the transponder 20, and the radio wave signal entered therein is amplified by the receiving circuit 21 and mixed with the output of the oscillation circuit 22 of 100 kHz and the mixing circuit 23 to be transmitted by the transmitting circuit 2
Then, the signal is transmitted from the antenna 20b to the transceiver 10 via No.4.

The radio wave signal received by the receiving antenna 10b of the transceiver 10 is amplified by the receiving circuit 14 and mixed with the signal of the VCO 12 by the mixing circuit 15, and a bandpass filter (BPF) 16 having a center frequency of 100 kHz ± 5 kHz is used. After that, it is input to the phase difference detection circuit 18 (see signal F). The phase difference detection circuit 18 receives the 100 kHz reference signal (see the signal Q) from the 100 kHz oscillation circuit 17 at one input, and this and the BPF 1
A phase comparison is made with the signal passed through 6.

The phase difference G detected by the phase difference detection circuit 18
Is added to the phase change amount detection circuit 19, and the change amount (slope) of the phase difference G is detected here. The output of the phase change amount detection circuit 19 is sent to the distance calculation means 30, where
Distance d0 between transceiver 10 and transponder 20
Is calculated. The distance calculating means 30 uses the control voltage generating circuit 11 to change rate data M of the transmission signal of the table currently used in the function generating ROM 31 (the rate of change of the frequency of the pattern PA of the pattern PA in FIG. 2 (the slope of the straight line) M1, M2, .. Mn reference, M is the rate of change in the frequency of the current transmission signal (the slope of the straight line), which is one of M1, M2, ... Mn), and the detected variation and the transmission signal The distance d0 is calculated according to the equation (1) by the ratio with the change rate M at that time. Here, the calculated distance d0 is sent to the microprocessor (MPU) 32 mounted on the control device 4. In addition,
33 is a display in the cab 3, and 34 is an alarm device.

The control voltage generating circuit 11 is a circuit for generating a voltage value for controlling the oscillation frequency of the VCO 12, and D
A / A conversion circuit (D / A) 11a and a read control circuit 11b, and the read control circuit 11b refers to the table of the function generating ROM 31 in response to a control signal from the MPU 32 and selects one of the patterns therein. Then, the function data is read therefrom, converted into a linear digital value, and added to the A / D conversion circuit 11a. Then, the A / D conversion circuit 11a is
A / D according to the clock CLK sent from the PU 32
The conversion is performed and the output is sent to the VCO 12.

In the table stored in the function generation ROM 31, as shown in FIG. 2, a straight line L1 and its generation time data T are formed as a pattern sequence of straight lines whose slopes change sequentially.
1 as the head (L1 + T1) and L2 + T2, ...
Data of Ln + Tn are provided and sequentially read, so that a voltage for generating a transmission signal B'as shown in FIG. 3 (a) is applied to the VCO 12. Therefore, the voltage signal A ′ of the control voltage generation circuit 11 is also a voltage signal having a shape corresponding to the waveform of the transmission signal B ′.
Further, in this table, as described above, the straight lines L1 and L
2, ..., Ln are stored in the order in which the slopes of these straight lines correspond to each other, and the read control circuit 11b sequentially reads the straight line data and M1, M2, ... Mn and sends them to the distance calculating means 30. To do. As a result, the frequency (transmission signal B ') generated from the VCO 12 changes in the form of a line graph as shown in FIG. 3 (a), and this is transmitted to the transceiver 10.

Instead of the straight lines L1, L2, ..., Ln, L0 is set as a straight line having a reference slope K, and this is stored in the read control circuit 11b. on the other hand,
In the above table, the time values T and T1, T2, ..., Tn
And M1 and M2 as magnifications with respect to the slope K of the reference straight line L0
, ... Store the value of Mn. This allows VCO12
If a control voltage to be applied to is generated, for example,
When the straight line L1 of FIG. 3A is generated when M1 = 1, the straight line L1 can be set as the reference straight line L0.
Other straight lines can be freely generated in the same manner as above by selecting the values of M1, M2, ... Mn. As a result, the detected phase difference G is sent to the phase change amount detection circuit 19. The change of the phase difference G in this case is as shown in FIG.
It becomes something like.

The phase change amount detection circuit 19 calculates the rate of change dφ / dt with respect to the phase difference G as shown in FIG. 3 (b) to obtain a value as shown in FIG. 3 (c). Distance calculation means 30
Is the change rate data M of the transmission signal of the table currently used in the function generation ROM 31 from the control voltage generation circuit 11.
(Refer to the rate of change of frequency M1, M2, ... Mn in FIG. 3, M is the rate of change of frequency of the current transmission signal, and M1, M2 ,.
... One of Mn. ) Is obtained, the distance d0 is obtained according to the equation (1) by the ratio of the detected change amount and the change rate M of the transmission signal at that time. The value of M at this time is shown in FIG. 3 (d) in correspondence with FIG. 3 (a). When the reference straight line L0 described above is set and M = 1,
A predetermined reference straight line L for the transmission signal B '
It gives a change according to 0.

Now, the MPU 32 obtains the calculation result of the distance from the distance calculating means 30 to the transponder 20. In this case, the change point from one straight line to another straight line (the broken line graph in FIG. 3A is broken). Since the value of point) changes rapidly, the MPU 32 excludes the calculation result of this rapidly changed distance and calculates the distance to the transponder 20 as an average value as shown in FIG. 7 (c). .

Here, the table stored in the function generating ROM 31 has various patterns in addition to the change pattern of the line graph as shown in FIG. Which of the patterns is selected can be selected via the MPU 32 by an input instruction from the operation panel. Therefore, when a plurality of work machines are working at the same site, as shown in Fig. 4, one work machine specifies the PA transmission pattern and sends a transmission signal, and the other work machine outputs PB.
By generating the transmission signal by specifying the transmission pattern of, each work machine can receive signals of frequencies modulated at 100 kHz corresponding to each transmission frequency from the same transponder by transmitting at different frequencies. it can.

Even if both construction machines select the same pattern, since the work machines are not synchronized with each other, the transmission start timings are different, so that the two transmission patterns have the same frequency. Almost no interference on the receiving side is prevented. Even if the content of the transmission pattern on the straight line is the same, if the transmission time of each pattern is different, a large number of different patterns can be generated at the same frequency displacement. The transmission pattern can be selected.

As described above, the ROM may store not the function of each straight line but the digital data string itself that directly generates the straight line of the line graph. Further, although the construction machine has been described in the embodiment, the present invention can be applied to a working machine in general.

[0027]

According to the present invention, since a transmission wave having a frequency which is modulated according to a linear function having a different inclination is generated and transmitted to the transponder, the transponder performs a plurality of operations. Even if the transmission waves are received from the machines at the same time, the respective working machines do not operate in synchronization with each other, and therefore transmission waves of the same frequency are rarely generated at the same timing. Therefore, the transponder can simultaneously receive transmission waves of independent frequencies and send back to each, and the transceiver (each work machine) side can independently measure the distance to the transponder. as a result,
The worker's safety can be secured even in a work environment in which a plurality of work machines work at the same time.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of a microwave distance sensor mounted on a construction machine to which a work machine safety system of the present invention is applied.

FIG. 2 is an explanatory diagram of a table that stores a modulation pattern that increases or decreases the transmission frequency.

FIG. 3 is an explanatory diagram of a relationship between a transmission frequency increasing / decreasing function and a phase change rate.

FIG. 4 is an explanatory diagram of transmission signals from a plurality of work machines.

FIG. 5 is an explanatory diagram of a relationship between a transceiver and a transponder.

FIG. 6 is a system configuration diagram of a microwave distance sensor when a conventional transponder system is applied as a safety system for a construction machine.

7 is an explanatory diagram of a relationship between a transmission signal and a detected phase difference in the case of distance measurement in FIG. 6, (a)
Is an explanatory diagram of a state of change in frequency of a transmission signal,
(b) is an explanatory view of a change rate of the detected phase difference.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Hydraulic excavator, 2 ... Worker, 3 ... Driver's cab, 4 ... Control device, 10 ... Transceiver, 10a, 20b ... Transmitting antenna, 10b, 20a ... Receiving antenna, 11 ... Control voltage generation circuit, 12 ... Voltage controlled oscillation Circuit (VCO), 13,
24 ... Transmission circuit, 14, 21 ... Reception circuit, 15, 23 ...
Mixing circuit, 16 ... Band pass filter (BP
F), 17, 22 ... 100 kHz oscillation circuit, 18 ... Phase difference detection circuit, 19 ... Phase change amount detection circuit, 20 ... Transponder, 30 ... Distance calculation circuit, 31 ... Function generation RO
M, 32 ... Microprocessor (MPU).

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[Procedure amendment]

[Submission date] November 14, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a system configuration diagram of a microwave distance sensor mounted on a construction machine to which a work machine safety system of the present invention is applied.

FIG. 2 is an explanatory diagram of a table that stores a modulation pattern that increases or decreases the transmission frequency.

FIG. 3 is an explanatory diagram of a relationship between a transmission frequency increasing / decreasing function and a phase change rate.

FIG. 4 is an explanatory diagram of transmission signals from a plurality of work machines.

FIG. 5 is an explanatory diagram of a relationship between a transceiver and a transponder.

FIG. 6 is a system configuration diagram of a microwave distance sensor when a conventional transponder system is applied as a safety system for a construction machine.

FIG. 7 is an explanatory diagram of a relationship between a transmission signal and a detected phase difference in the case of distance measurement in FIG. 6, (a).
Is an explanatory diagram of a state of change in frequency of a transmission signal,
(B) is explanatory drawing of the change rate of the detected phase difference, (C)
FIG. 6 is an explanatory diagram of averaging calculated distances.

[Explanation of Codes] 1 ... Hydraulic excavator, 2 ... Worker, 3 ... Driver's cab, 4 ... Control device, 10 ... Transceiver, 10a, 20b ... Transmit antenna, 10b, 20a ... Receive antenna, 11 ... Control voltage generation circuit, 12 ... Voltage controlled oscillator (VCO), 13,
24 ... Transmission circuit, 14, 21 ... Reception circuit, 15, 23 ...
Mixing circuit, 16 ... Band pass filter (BP
F), 17, 22 ... 100 kHz oscillation circuit, 18 ... Phase difference detection circuit, 19 ... Phase change amount detection circuit, 20 ... Transponder, 30 ... Distance calculation circuit, 31 ... Function generation RO
M, 32 ... Microprocessor (MPU).

Front page continuation (72) Inventor Shigenori Aoki, 650 Jinrachicho, Tsuchiura City, Ibaraki Prefecture Hitachi Construction Machinery Co., Ltd. Tsuchiura Factory

Claims (2)

[Claims] 1. A transmission signal whose frequency is sequentially increased or decreased in a predetermined frequency range is transmitted from a transmitter, and a transponder which receives the transmission signal modulates the reception signal with a predetermined signal and transmits it to the transmitter side. Calculating the distance from the transmitter to the transponder by detecting the rate of change of the phase of the predetermined signal by mixing the transmission signal and the reception signal from the transponder by the receiver on the transmitter side, In a work machine having a safety system that generates an alarm or the like according to the position of the transponder, the frequency of the transmission signal is continuously increased or decreased along a certain straight line, and the slope of the straight line is sequentially increased after a predetermined time. Based on a control circuit for changing, a detection circuit for detecting the rate of change of the phase, an output of the detection circuit and a slope of the straight line when the output is obtained. And a distance calculation unit that calculates the distance. 2. The frequency is microwave, and straight lines having respective slopes set after the predetermined time are stored as data indicating a control pattern composed of a series of straight lines and the slopes, and this data is stored. The work machine safety system according to claim 1, wherein a plurality of the data are stored in tabular form and one of the data is selected.