CA2367161A1 - Remote acoustic detonator system - Google Patents
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- CA2367161A1 CA2367161A1 CA 2367161 CA2367161A CA2367161A1 CA 2367161 A1 CA2367161 A1 CA 2367161A1 CA 2367161 CA2367161 CA 2367161 CA 2367161 A CA2367161 A CA 2367161A CA 2367161 A1 CA2367161 A1 CA 2367161A1
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Abstract
An acoustic detonator system wherein a blast initiation signal emanating from a programmable controller is acoustically transmitted to individual, remote programmable detonators associated with specific explosive charges. The controller communicates with a programmable acoustic detonator transmitter. Upon interpreting the blast initiation signal, the acoustic detonator transmitter generates an acoustic sound wave including instructions to the acoustic detonators. By assigning a single sacrificial acoustic detonator to a single charge, a timed blast sequence may be created without the need for time consuming and expensive hand wiring of the charges.
Description
r The instant invention relates to explosive detonator systems in general, and more particularly, to acoustically activated detonators.
BACKGROUND ~,T
Explosives have been a necessary evil in the mining, demolition, tunneling, quarrying, oil, gas, construction and related industries for years. Over time, explosives technology has advanced arm-in-arm with safety considerations. The current state of the art generally consists of, in simplified fashion, a detonator, fuse, primer, and explosive.
The detonator is usually energized via a hardwired clectrical signal. By activating the detonator, the fuse is blown which sets offthe primer. As the primer ignites, the charge subsequently explodes. For safety and efficiency reasons, the long daisy chain of firing components are strung together to (1) ensure no inadvertent firing and (2) affirmatively place and sequentially time the explosives for full effect.
Current blasting practice in most underground mines utilizes the non-electric shock tube system. This system involves the sequencing of the blast as it is loaded and/or following a pre-planned sequence pattern. A novel is inserted into the explosive column of the hole being loaded. The novel's end is attached to a length of detonating cord. All novel detonators involved in the blast are attached to the detonating cord trunkline. The trunkline in turn has an instantaneous electric detonator attached. The electric detonator is attached to a length of lead wire that runs back to the blasting box. The blasting box may be part of the mine's central blasting system.
Novels come in two separate timing sequences. Long delay periods (LP) and short period delays (SP). Both delay s~uences have a color code on the connector because the timing of the sequences is not compatible. Problems anise when people have visual impairments, are hurried or have not been properly trained to differentiate between the two sequences. Hole lengths can vary greatly which requires novels to have many different lengths. Insuring that the proper length of shock tube an the detonator for the application is a must. Too long and the expensive shock tube is being wasted;
and too short does not allow for proper detonator placement which results in the shock tube remaining inside the hole collar.
Packaging and transportation of detonators with shock tubes is bulky and expensive. Multiple trips down a shaft are required to deliver the detonators.
When placed into underground storage or finally used at the stops or face, the packaging must be removed, cleaned and returned to the surface. Inventory and storage requires large inefficient storage capacity because of the bulkiness of the product.
In production blasts where long lead novels are used, the spent shock tube must be cleaned up and removed after the blast. This is time consuming and costly.
Portions of spent shock tube that are left after the blast get into the muck circuit.
The shock tubes end up in the subsequent milling process because most of the existing scrap manipulator systems are designed for the removal of steel, not plastic.
Hardwired systems suffer from the need to tie numerous detonators together and connect the entire array to a remote initiator site. It is often difficult, labor intensive, expensive and time consuming to run long lengths of electrical wires from the blast site to the remotely situated initiation site. This is particularly true in underground mining applications using sequential blast patterns.
BACKGROUND ~,T
Explosives have been a necessary evil in the mining, demolition, tunneling, quarrying, oil, gas, construction and related industries for years. Over time, explosives technology has advanced arm-in-arm with safety considerations. The current state of the art generally consists of, in simplified fashion, a detonator, fuse, primer, and explosive.
The detonator is usually energized via a hardwired clectrical signal. By activating the detonator, the fuse is blown which sets offthe primer. As the primer ignites, the charge subsequently explodes. For safety and efficiency reasons, the long daisy chain of firing components are strung together to (1) ensure no inadvertent firing and (2) affirmatively place and sequentially time the explosives for full effect.
Current blasting practice in most underground mines utilizes the non-electric shock tube system. This system involves the sequencing of the blast as it is loaded and/or following a pre-planned sequence pattern. A novel is inserted into the explosive column of the hole being loaded. The novel's end is attached to a length of detonating cord. All novel detonators involved in the blast are attached to the detonating cord trunkline. The trunkline in turn has an instantaneous electric detonator attached. The electric detonator is attached to a length of lead wire that runs back to the blasting box. The blasting box may be part of the mine's central blasting system.
Novels come in two separate timing sequences. Long delay periods (LP) and short period delays (SP). Both delay s~uences have a color code on the connector because the timing of the sequences is not compatible. Problems anise when people have visual impairments, are hurried or have not been properly trained to differentiate between the two sequences. Hole lengths can vary greatly which requires novels to have many different lengths. Insuring that the proper length of shock tube an the detonator for the application is a must. Too long and the expensive shock tube is being wasted;
and too short does not allow for proper detonator placement which results in the shock tube remaining inside the hole collar.
Packaging and transportation of detonators with shock tubes is bulky and expensive. Multiple trips down a shaft are required to deliver the detonators.
When placed into underground storage or finally used at the stops or face, the packaging must be removed, cleaned and returned to the surface. Inventory and storage requires large inefficient storage capacity because of the bulkiness of the product.
In production blasts where long lead novels are used, the spent shock tube must be cleaned up and removed after the blast. This is time consuming and costly.
Portions of spent shock tube that are left after the blast get into the muck circuit.
The shock tubes end up in the subsequent milling process because most of the existing scrap manipulator systems are designed for the removal of steel, not plastic.
Hardwired systems suffer from the need to tie numerous detonators together and connect the entire array to a remote initiator site. It is often difficult, labor intensive, expensive and time consuming to run long lengths of electrical wires from the blast site to the remotely situated initiation site. This is particularly true in underground mining applications using sequential blast patterns.
There have been attempts to remotely activate blasting systems.
U.S. patent 5,159,149 to Marsden discloses a remote detonator system employing untethered radio frequency (1tF) transmitters and receivers. Each detonator must be physically coupled and uncoupled with a combined charging energy storage means and a programmable delay time means prior to shot initiation.
Canadian patent 1,309,299 to Beattie et al., discloses a wireless system including detonation means capable of receiving ItF signals from a remote source hardwired to a fuse via connecting wires.
Canadian patent 1,298,899 to Beattie et al., discloses a dual detonation system employing RF and a steerable laser beam.
Wired designs include U.S. patent 5,295,438 to Hill et al, and U.S. patent 5,520,114 to Guimard et al. The former patent discloses a transportable programming tool and a control loop. Each detonator is affixed to a split core which is hooked to the loop. The latter patent discloses a feedback programming unit and an integrated electronic delay detonator.
Current commercially available detonation systems still ultimately require physically connecting wires to each detonator regardless of the mode of initiation.
The purpose of the present invention is to provide a remote wireless untethered acoustic blast initiation system. The need for such a system comes from a greater requirement to automate the entire mining process. A key part of the underground hard rock mining process is blasting. In order to automate blasting, a technique is needed to allow for the wireless initiation of a blast. Wiring a blast is a labor intensive manual process requiring a person to physically connect wires to each detonator. As well, many different time delays are required for the blast. Since development blasts can have a blast pattern containing 80 or more detonators, the possibility for human error is high. These errors occur in the placement of a detonator with the wrong timing in a hole.
Incorrect placement and timing of the blast pattern creates poor break" bootlegs, loose rock, varying muck size and damage to the opening. This in turn raises safety issues and creates higher mining costs.
Assignee has developed a successful prototype 1tF remote detonator system wherein a coded 1iF triggering signal is transmitted from an RF transceiver to one or more wireless 1tF detonators. The 1tF signal programs the RF detonators' time delay and initiates the blast.
The difficulty with RF initiated remote systems relates to the problematic transmission and reception of the 1tF signals through underground rock and ore.
Electrical signals are attenuated and do not travel through these mediums very far. To ensure that the detonators receive programming and initiation signals, the detonators require antennae that protrude out of the blasthole. Antennae are relatively fragile and are subject to damage. Moreover, they pose handling and loading problems, particularly when utilized with automatic loading devices. The spider web of antennae is easily dislodged.
As an alternative, acoustic triggering was considered. Mindful that structures, especially mines, are subject to a bewildering array of noise and vibration from numerous sources-blasting, hauling, drilling, machinery, etc., the safety of acoustic based detonator systems was carefully considered.
It is known that noise is capable of traveling great distances underground through solid and liquid mediums such as rock, ore and water. The instant inventors believed that by harnessing, modulating and analyzing vibration within rock, a safe dependable acoustic-based detonating system could be developed. Alteration of acoustic signals can be calculated and physically measured to initiate an explosive charge.
The present invention allows data from a computerized blasting design program to be transferred directly to the detonators and the automatic machine installing them.
This reduces error and allows for a machine to automatically install the detonators. The elimination of wires greatly reduces the complexity of the automated machine required to install the detonators. The elimination of wires or other tethers such as shock tubes also eliminates the chance of the tethers being cut by the blast before the initiation signal can .4_ propagate to the other detonators. This creates a poor blast i.e. oversize chunks, poor perimeter contour and bootlegs. All of these factors create additional worker hazards, decrease e~ciency and raise costs. Efficiency and safety of the process is also improved since the blast design data is immediately available to the blast operator and is transferred by computer file instead of being read and acted upon by a person.
In summary, conventional detonators come with preset times, creating the need to stock many dii~erent detonators, each with individual time delays. In contrast, the present acoustic system allows one detonator to be stocked and allows for much finer control of the blast by allowing a higher resolution and greater number of delay times.
The detonators may be timed in I millisecond (ms) increments up to 10,000 ms, giving total timing control. These times are determined by measuring rock properties.
Matching the timing to the rock properties gives consistent fragmentation, which is required in automated mining.
An advantage of using acoustic communication as opposed to ItF initiation is that there are no cumbersome antenna wires. They are easily damaged and may also be easily pulled out of the detonator causing failure to fire the detonator resulting in undetonated explosives remaining in the blasthole. Moreover, the initiating acoustic signal to the acoustic detonators can be sent over relatively long distances underground through solid materials.
,SUMMARY OF THE INVENTION
Accordingly, there is provided an acoustic detonator system that is adapted to initiate a timed sequential blast pattern by an acoustic signal transmitted to each individual detonator.
A remote central processing unit (CPU) programmed with detonator programming software communicates with an acoustic base transceiver. The acoustic base transceiver communicates with at least one remote dedicated acoustic detonator affixed to an individual charge. The acoustic detonator interprets the signal, disregards extraneous and potentially dangerous "noise" and fires off an internal fuse directly setting off the associated charge.
-S-PC-~t 177 B~tIEF DESCRIPTION OF'~~ D,~~~TGS
Figure 1 is an overall schematic diagram of an embodiment of the invention.
Figure 2 is a schematic diagram of an embodiment of the invention.
Figure 3 is a schematic diagram of an embodiment of the invention.
Figure 4 is a schematic diagram of an embodiment of the invention.
Figuro 5 is a schematic diagram of an embodiment of the invention.
Figure 6 is a schematic diagram of an embodiment of the invention.
Figure 7 is a schematic diagram of an embodiment of the invention.
Figure 8 is a schematic diagram of an embodiment of the invention.
Figure 9 is a schematic diagram of an embodiment of the invention.
Figure 10 is a schematic diagram of an embodiment of the invention.
Figure 11 is a sample waveform.
Figure 1 depicts a schematic representation of the remote acoustic detonating system 10. A programmable controller 12, preferably a computer, ultimately communicates via acoustic energy or sound waves 18 through a medium such as solid ground 20 to one or more discrete explosive charges 14 or 14(A) ("A" equaling 1, 2, 3,....).
Each explosive charge 14 includes its own si~x~ and ~dicated microacoustic detonator 16 or 16A ("A" equaling 1, 2, 3,....). For non-limiting simplicity, any reference to an individual component will include multiple iterations unless indicated to the contrary.
Acoustic transmitting transducers 22, such as piezoelectric devices, microphones, sonic transducers, speakers, flat panels, pingers, etc. generate the sound waves 18 of appropriate wavelength, amplitude, frequency and duration to travel to and safely trigger the explosive charges 14. Similarly, acoustic receiving transceivers 24, which may be identical to the transducers 22, receive the transmitted sound waves 18 for interpretation and detonation. The receivers 24 are generally small enough to be integrated into or affixed to the detonator 16 so as to be easily fit into a blast hole.
By virtue of the controller's 12 software, once a firing program has been initiated, 13 an acoustic trigger will target each batch of detonators 16. By reducing or eliminating wired connections between the controller 12 and the blast site, the difficulties posed by the prior art direct hardwired or wireless antenna based systems are reduced.
In the embodiment depicted, the inventors utilized Inco Limited's preexisting broadband CATV communications network 32 connecting surface structures to underground mine locations. However, as will become apparent, any communication system bridging the controller 12 and the blast site may be used.
The system 10 includes the controller/computer 12 (preferably equipped with Microsoft Windows~ 95 or NT~ (or later), and Inco Limited's proprietary Telebiast AT"~ blast control software [copyrighted copies are available from Inco Limited]), a local acoustic detonator base transmitter 26 ("acoustic transmitter") and one or more remote acoustic detonators 16.
The computer 12 communicates with the acoustic transmitter 26 using its serial communications port (COM 1 ). The acoustic transmitter 26 modulates the data stream coming from the computer 12 onto the acoustic wave signal 18. The acoustic wave signal 18 is received by the acoustic detonator 16 and is demodulated to provide data for a central processing unit 36 located in the acoustic detonator 16. See Figure 3.
_7-As briefly stated previously, Figure 1 demonstrates Inco Limited's abovegound/undergound communications system in an abbreviated fashion. The controller 12, which may be stand-alone or part of a larger comprehensive mining control system and may be disposed above ground 28 or in any secure remote location, is connected to a conventional serial to ethernet converter 30 via a RS-232 serial bus 104.
The signal is passed through the conventional network 32 to a first standard modem 34.
The modem 34 in turn is connected to the acoustic transmitter 26 conveniently disposed underground, that is, below ground 28. The communications link is passed underground through a main broadband underground communications trunk system 100.
A branch line 102 offthe trunk 28 is diverted to the modem 34. The modem 34 in turn communicates with the acoustic base transmitter 26.
As one skilled in the art will readily appreciate, the means for communicating and transmitting a signal from the controller 12 to the acoustic transmitter 26 may be as varied as desired depending on site considerations, available equipment, permanence, finances, etc. It is within the realm of this invention that in non-mining situations such as construction, oil, gas, demolition, quarrying, etc., the distance and communication system may be relatively short, line of sight, wireless and simple. In other situations, such as underground or under water, the communication system traversing the controller 12 and the acoustic ddonator base transmitter 26 may be sophisticated and greatly spaced.
Whatever the conditions, one skilled in the art is capable of causing the controller 12 to communicate with the acoustic transmitter 26.
In particular, the instant system 10 allows for easy integration onto a conventional two-way network 32 such as one typically installed in underground mines.
The system 10 takes advantage of existing cable and network infrastructure already installed thereby reducing cost. The cost of installing dedicated wiring is eliminated.
Security of communications is ensured by using blast control software employing a mathematical coding scheme, cyclic redundancy check ("CRC"), addressable detonators 16, a dedicated broadband CATV channel and a distinctive acoustic signal.
_g-The system 10 unabashedly takes advantage of the ever increasing and amazing reductions in electronic component size and cost. The components making up the acoustic detonator 16 can be made so small and cheaply that they are literally expendable.
By physically mating the acoustic donator 16 to each specific charge 14, the safety and efficiency of explosive blasting is considerably camped up.
In the present discussion, particular manufacturers' components may be referenced for convenience. However, it should be understood that comparable alternatives may be substituted for the particular identified components. What must be t0 borne in mind is that a remote safety-triggering signal is transmitted from a remote initiation site to a transmitter 26. The transmitter 26 in tum generates an acoustic signal 18 to a distinct explosive charge 14. Each charge 14 includes its own stand-alone dedicated acoustic detonator 16. The acoustic detonator I6 interprets the signal from the transmitter 26 and, if conditions are appropriate, initiates the explosive sequence.
In Figure 2, the controller 12 is shown connected to the acoustic detonator base transmitter 26 (minus intermediate connections). Figure 3 is a schematic of an acoustic detonator 16.
The controller 12 is programmed with the appropriate software and commands the system 10. The Telebfast AT"' blast control software:
a) computes the CRC for communication verification and integrity.
This is a method for checking the accuracy of a digital transmission over a communications link. The computer 12 performs a calculation on the data and attaches the resulting CRC
value to the communication data stream; the transmitter CPU 38 performs the same calculation and compares its result to the original value in anticipation of a hand shake confirmation. If they do not match, a transmission error has occurred and the receiving CPU 38 requests retransmission of the data;
b) allows an operator to program: a blast batch identification number, a detonator identification number and detonator delay time in milliseconds (0 to 10000) into each detonator;
s a c) allows an operator to initiate a common fire command to start a countdown from each individual detonator delay setting for all detonators within a batch;
d) allows programming and initiation over a secure networked communication system via the modem 34.
The acoustic detonator base transmitter 26:
l0 a) transmits coded acoustic signals. It communicates with the detonator CPU 36.
The CPU 38:
a) encodes the batch identification number, detonator identification number, detonator delay times, CRC, arm and fire codes.
The transmitter (Tx} 48 includes:
a) modulation circuitry which modulates encoded transmit data. It uses a FSK (frequency shift keying) modulation format.
b) driver circuitry which takes the tow voltage and low current signal of the modulation circuit and provides enough current and voltage to drive the acoustic transducer 22.
The transducer 22 converts modulated electrical energy into modulated acoustical energy. For underground applications it is preferably coupled to solid ground or rock 20.
The acoustic detonating system 10 may be used in non-gaseous mediums such as solid-like earth formations, rock, underground mines, quarries, tunnels, construction and demolition sites, etc.. It may be also used in liquid environments such as bodies of water, rivers, liquid conduits, pools, etc. As long as the non-gaseous medium is capable of effectively transmitting an acoustic energy (sound) wave to the ultimate destination, the instant system 10 may be employed in many situations. Naturally in water environments the components need to be sufficiently waterproofed.
r The acoustic detonator 16 receives and decodes coded acoustic signals:
a) The acoustic receiver 24 is an acoustic signal sensor such as a microphone (piezoelectric sensor in the prototype). The acoustic receiver 24 converts acoustic energy to electrical energy which it receives acoustic energy transmitted through rock and explosive emulsion.
b) The receiver (Rx) 50 consists of a receive buffer and demodulation circuit. The receive buffer amplifies the signal from the acoustic receiver 24 for use by the demodulation circuit.
The demodulation circuit demodulates the FSK signal into a data stream for use by the CPU 36.
c) The CPU 36 decodes coded data from receiver 50 consisting of batch identification number, detonator identification number, detonator delay times, arm command, fire command and CRC.
If appropriate, it outputs a fire command to relay 40.
d) The energy source 42, which may be a battery and/or capacitor, powers the acoustic detonator 16 including the receiver 50, the CPU 36, the relay 40 and the fuse 44 circuits. Discharge 98 begins upon turning on the roceiver 50 and the CPU 36.
A prototype acoustic detonating system 10 was built and successfully tested as shown in Figures 4-10. The following discussion relates to the prototype in greater detail.
For both the transmitter 26 and detonator 16, a MicrochipTM CPU PIC 16C63A
programmable microcontroller ("PIC") 52, 80 was chosen based on its low cost, functionality and ease of programming. The PIC 52, 80 is essentially a complete computer in a small, low cost package, with a central processor, random access memory (RAM) for temporary storage and programmable read only memory (PROM) for permanent storage of a software program.
To acoustically transmit and receive the binary sequence, several modulation schemes were identified including impulsive (hammer type), on-off keying (pinging) and frequency shift keying ("FSK", two separate frequencies representing on and off. For the prototype, FSK was used.
The transmission circuitry 56 was programmed to generate a binary 8-bit transistor-transistor logic ("TTL") (on-oil sequence. As shown in Figure 4, the TfL
signal is transformed by FSK modulating circuit 58 to an FSK signal large enough to drive via piezo driver circuit 60 the acoustic transducer 22. Piezoelectric devices were used for the acoustic transducer 22 and receiver sensor 24 simply due to their availability and the ease with which they may be interfaced. For demonstration purposes, a 4-foot ( I .22m) high cylindrical column of concrete 54 was used to simulate transmission through rock. The driver circuit 60 amplifies the FSK signal to an appropriate level for the piezoelectric device 22.
The acoustic signal, after passing through the concrete 54, is received by the second piezoelectric device 24 also affixed to the concrete 57. In order to receive an adequate signal level, a buffer circuit 62 is used to provide signal gain from the piezoelectric device 24 to the remaining receiver system. The received FSK
signal is then passed through an FSK demodulation circuit I 08, resulting in the reproduction of the original TTL signal. The TTL signal is then inputted to the receive circuit 64 including PIC 80, where it is decoded to an 8-bit value. A valid detonation code is determined if the 8-bit value matched a predetermined value that was stored in the receiver PIC 80.
Upon reception of a valid detonation code, the receive circuit 108 energizes a thus simulating a detonation. If the data is not a valid detonation code, the LED remains de-energized and the receive circuit 108 continues to await another transmission.
The receive circuit 108 can be programmed with a variable time delay. Thus, the LED 68 can be programmed to energize after a programmed time delay, which simulates a delayed detonation signal to a detonator cap.
To control the acoustic detonator 16 circuits, software performs the following tasks:
s r a) on the transmit PIC 52 (see Figure S) the software, transmits one of two possible 8-bit binary numbers selectable by an electronic switch;
b) on the receive PIC 80 (see Figure 10), the software receives and decodes the 8-bit binary signal and determines whether it is a valid detonation command; and c) on the receive PIC 80, if the received code is valid, it simulates detonation by energizing the LED 68 after a determined time delay.
Turning now to the details of the prototype in greater detail.
The PIC 52 is used on the transmitter 26 to store and generate the detonation codes. Two separate 8-bit codes were required to demonstrate successful operation of the acoustic detonator 16 prototype. The ftrst code is a valid detonation code, which, when transmitted, will result in a simulated detonation. The srcond is an invalid detonation code, which, does not result in a simulated detonation, thus demonstrating that a specific 8-bit number is required to trigger a detonation. The 8-bit codes were chosen arbitrarily and can be assigned any value.
For brevity, in Figures 5 to 10, a number of the components such as resistors, capacitors, power supplies, amplifiers, etc. known to those skilled in the art will not be discussed.
Figure 5 is a schematic drawing of the transmit circuit 56. The transmit PIC
outputs the 8-bit code serially on pin 22 (RB1, Port B). This binary TTL
signal is then passed to the FSK modulation circuit 58. An electronic switch SW I is used to allow the user to select which 8-bit code was to be transmitted (i.e. the valid or invalid code). The switch SW 1 is connected to pin 23 (ltB2, Port B) and pin 24 (RB3, Port B).
When toggled, the switch S W I places on either RB2 or ltB3, thus selecting which code is to be transmitted. Two LEDs D1 (valid code) and D2 (invalid code) are connected in line with the switch SW 1 to display which code had been selected for transmission. A
momentary close switch SW2 is connected to pin 21 (RBO/INT). Pressing this switch asserts an interrupt on the PIC 52 resulting in the selected code being transmitted once (i.e. one shot operation).
The PIC 52 is powered by a SV regulated power supply. A 20MHz crystal 70 is placed across pin 9 (CLKIN) and pin 10 (CLKOUT), resulting in a SMIPS
instruction rate. An additional LED D3 is placed on pin 2 (RAO, Port A) which is energized when the PIC 52 is under normal operation.
The TTL binary signal from the transmit circuit 56 is FSK modulated by the circuitry shown in Figure 6. FSK modulation was chosen for its simplicity to implement and the control it allows over the frequency content of transmitted signals.
FSK was also chosen in order to reduce the risk of a narrow band interference source from initiating a detonation by virtue of it's frequency diversity. For ~monstration purposes, a center frequency of 2.SkHz was chosen arbitrarily with mark/space frequencies of 2kHz/3kHz.
IS Thus, binary 0 results in a 2kHz sine wave, while binary 1 produces a 3kHz sine wave.
To achieve this modulation technique, the FSK modulation circuit 58 was designed using a XR-2206T"' function generator integrated circuit 72 manufactured by EXART"~.
The circuit 58 is capable of converting a TTL keying signal (the 8-bit code) to a frequency-modulated sine wave. The mark/space frequencies are set by a combination of external resistors and capacitors.
The TTL signal from the transmit circuit 56 is input to pin 9 of the integrated circuit 72. Capacitor C1 (across pins 5 & 6) along with R1 (pin 7) and R2 (pin 8) determine the mark/space frequencies. The amplitude of the output sine wave may be adjusted by changing the resistor value of R3 connected to pin 3. However, for this demonstration the value was chosen to pmduce a 6V peak-peak sine wave. The FSK
output is located on pin 2 and is capacitively coupled to the driver circuit 60. The integrated circuit 72 was powered by a l OV regulated supply for the demonstration.
However, it is capable of operating over a range of 1 OV-26V. Frequency of operation 3o may be anywhere between 0.01 Hz - I MHz.
Turning now to Figure 7, there is shown a driver circuit 60. Due to the inefficiency of the piezoelectric material as a transmitter, a large voltage is required to successfully transmit an acoustic signal through several feet of concrete. The output from r the circuit 58 in the modulation circuitry only provides a 6V peak-peak signal. It was required to boost this signal to roughly 400V peak-peak to achieve a successful transmission. A step-up transformer 74 is used to achieve the boost. However, a buffer circuit is also required to provide the current to drive the transformer 74 and the transducer 22.
The transformer 74 is a simple wire wound iron core. The buffer circuit is comprised of an OF183TM operational amplifier 76 configured for unity gain.
The amplifier 76 was chosen for its high output capability arid fast skew rates.
The transformer 74 drives the acoustic transmitter 22.
A detonator 16 was assembled with three main subsystems:
1 ) Receiver buffer 62;
2) FSK demodulation circuit 64; and 3) Receive circuit 108.
For demonstration purposes, two detonators were assembled ( 16 and 16A - see Figure 4), on a single circuit board and, for simplicity, shared the receiver buffer 62 and FSK demodulator 64 subsystems. See Figure 8.
The buffer circuit 62 is required to provide signal gain from the piezoelectric sensor 24 for use by the FSK demodulation circuit 64. A second or mirror OP183T"~
operational amplifter 78 was chosen and configured as a unity gain amplifier.
The buffed signal is routed to the FSK demodulation circuit 64.
In Figure 9, the demodulation circuit 64 was designed to perform FSK
demodulation based on mark/space frequencies of 2kHzi3kI-Iz. This design incorporated a XR-221 I FSK demodulation integrated circuit 106 ("1C"). The mark/space frequencies are selected by setting external resistors and capacitors. The FSK signal from the input buffer 62 is capacitively coupled to pin 2 of IC 106. The signal must be between l OmV-3V to be recognized by the IC 106.
The iC l 06 is configured to output two signals. The first is a carrier detect (CD) signal that is used to indicate whether or not the IC 106 has locked on a valid carrier frequency (i.e. between 2kHz and 3kHz). If a valid frequency is detected, the CD signal is to I~ set to OV. Otherwise, a SV signal indicates that a valid frequency is not found and hence no data is received. The second output signal is the data output (DATA). The DATA signal is TTL level and is derived from the raceiv~ FSK signal. It should be noted that as long as the CD signal is high (i.e. no carrier detected), the DATA output signal is un-defined. The CD and DATA signals are sent to the receive circuit 108 for interpretation. The IC 106 is powered by a l OV (Vcc) regulated supply.
Figure 10 depicts the receive circuit 108. The receive circuit 108 having the PIC
16C 63A programmable microcontroller 80 ("receive PIC 80") on the detonator 16 is required to perform three functions. First, the receive PIC 80 determines whether the data it is receiving from the FSK demodulation circuit 64 is valid or noise induced. It does this through analysis of the carrier detect signal (GD). If the CD signal from the FSK
demodulation circuit 64 is logic high (i.e. 5V indicating no carrier due) the receive t 5 PIC 80 ignores the data signal it received. If the CD signal is logic low, then the receiver PIC 80 accepts the data signal as a transmitted code. The second function roquired of the receive PIC 80 is to transform the received data back into an 8-bit cod and LED 110 is lit. The third function is to ddermine whether or not the received code matches the expected detonation code. If a match is found, the receive PIC 80 simulates detonation through energizing LED 68 after a predetermined time delay. For the demonstration, the two detonators 16 and 16A were implemented. This allowed the user to demonstrate that one transmitted code would result in two separate time delayed detonations.
The cagier detect (CD) sigaal is input to pin 13 (RC2, Port C) of the PIC 80 and the data (DATA) signal is input to pin 12 (RC1, Port C). The LED 68 is connected to pin 4 (RA2, Port A). This LED 68 is energized to simulate a detonation. The PIC 80 is powered by a SV regulated power supply. A 20MHz crystal 112 is placed across pin 9 (CLKIN} and pin 10 (CLKOUT), resulting in a SMIPS instruction rate. An additional LED 82 is placed on pin 2 (RAO, Port A) which is energized when the PIC 80 is under normal operation. Several of these detonators 16 may be constructed, each simulating a detonator with a different blast time delay.
The PIC 80 for the detonator 16 is programmed as a serial communications receiver. When powered up, the PIC 80 initializes itself and immediately starts waiting for the caurier detect (CD) signal from the demodulator circuit 64. When the CD makes the transition from high to low, it is known that the IC 106 is recxiving data so the processor waits for the start bit. If no information is being sent from the transmitter, the default data sent is stop bits. The start bit is detected when the FSK data pin makes the transition from high to low. This activates TIMER1 in the PIC 80 and all subsequent samples of the FSK data pin 12 are taken based on this timer. The data format that the PIC 80 re~nizes is 7 data bits, 1 parity bit and 2 stop bits. The program then verifies that the data is in the proper format and that the parity is cornet. If the detonate code is valid, then the software times out and turns on the LED 68 which represents the detonate signet. If during any part of the data gathering process the PIC 80 stops detecting the CD
signal, the PIC 80 reverts back to its waiting for carrier detect state. If the data received is determi~d to be invalid, the program reverts back to its start-bit wait state. Invalid data can be caused by an invalid parity bit, insufficient stop bits, or an invalid detonate code.
The baud rate use in the serial communications was ar6ritrarily set to 62.5 BPS.
At an instruction cycle spend of 5 MHz and a timer pre-sealer of 8:1 for the module, one bit length corresponds to 10000 TIMER1 increments. This is the delay time that is used with the TIMERI interrupt to control the sampling of serial data.
The program is designed to work like a state machine, with clearly defined states and statatrnnsitions that govern the flow of the program. The machine advances states depending ~ the 2 external or 1 internal interrupt. These are the carrier detect (CD) signal coming from the PIC 80, the data detect (DD) interrupt coming from the PIC 80 or the TIMERI interrupt generated by the PIC 80. If the data received is invalid, the program flow will return to the start bit wait state.
The program for the transmit circuit 56 works as follows. On startup, the transmit PIC 52 is initialized and immediately starts sending out stop bits (logic high) to the FSK modulating circuit 58. The only external inputs to the circuit 58 are a button (switch SW2) connected to pin RBO, and a toggle switch SW 1 connecting either pin RB2 or RB3 to logic high. When the button on switch SW2 is pressed, an RBO
interrupt is created and depending on whether RB2 or RB3 is high a different code is sent to the FSK
modulating circuit 58. The signal is sent at 62.5 BPS to pin RB 1. This signal is timed -i 7-out exactly as it is in the receiver using TIMERI . Once the transmission is complete another transmission can be started if desired.
In summary, the acoustic detonator system 10 demonstrates the feasibility of acoustically triggering the detonation of a blast area. The objectives of the acoustic detonator system 10 demonstrates the following: .
a) to acoustically transmit a unique binary code;
b) to acoustically receive and recognize a unique binary code through rock;
c) to process the unique code as a detonation trigger and perform the function of a programmable time-delayed detonation source;
and d) to perform the detonator functions in a small autonomous package that can be reproduced simply and cheaply in large quantities.
To accomplish these objectives, the prototype detonator 16 and transmitter 26 were constructed using an inexpensive microcontrollers and piezoelectric sensors. The transmitter unit was programmed to send two different "detonation codes": an invalid and valid code. The prototype detonators were programmed to receive and recognize a unique code, designated as the "valid code" by the transmitter. The prototype detonators were successfully demonstrated; they recognized the detonation code, delayed by a preprogrammed period, and asserted a detonation signal.
In a fully operational system 10, the output from the receive circuit 108 would be routed, not to the LED 68, but the relay 40. The cascade of events from the receipt of the acoustic signal 18 will discharge 98 the explosive charge 14.
By employing the FSK paradigm, a customized signal 18 may be generated thereby causing the most efficient signal propagation through the various rock and ground conditions in a mine.
_ 18_ Two typical non-limiting signal characteristic cases are outlined below. A 31 bit code and a 63 bit wave packet code are contemplated. The 63 bit code can carry additional intelligence. Other wave packets may be acceptable.
Center fl Q Chip 31-Bit 63-Bit Chip 31-Bit 63-Bit Freq. (Hz) (Hz) DnratioCode Code DuratioCode Code (Tiz) n Length Length n Length Length (mSec) (mSec) (mSec) (mSec) (mSec) (mSec) Case Case Case Case Case Case 2 312.5 2 342 4 1240 252 80 248 5040 1546.25_ 171 _ _ _ ~ 160 __ 10080 142 ~ _ _ __ ~ _ 80 ~ 2480 r 5040 4960 ~
Figure 11 shows a 31 bit detonator coding code excerpt. Each acoustic detonator 26 will respond to a particular code sequence and duration. For example, the following code characteristics may apply to the excerpt shown in Figure 11.
F~(Hz) F=(JEIz) Tc(msec) 2294 2725 5 or 10 1157 1350 10 or 20 574 680 20 or 40 285 342 40 or 80 142 171 80 or 160 The amplitude of the signal is a function of the medium and the range.
However, preliminary indications for hard rock mines, such as those found in Sudbury, Ontario, Canada appear to be somewhere between 110-120 db re 1 uPa 1 m, where the sensitivity of receiver device 24 is about 85db re 1 uPa. Under perfect conditions this translates to a range of about 50 meters. However, it should be apparent that different mediums will require different signal characteristics, and the above parameters are non-limiting examples.
The design components are easily miniaturized for use in blast holes.
The acoustic detonating system 10 need not be static. Returning to Figure 1, a communications junction box 84 including a modem 86 and wireless modem 88 are connected to a leaky coax cable 90. The leaky coax cable 90 may be disposed throughout a mine and on different levels, drafts and stopes.
An acoustic detonator mobile base transmitter 92 mounted on a mobile vehicle is capable of being brought into close proximity to a blast site. It is contemplated that the transmitter 92 may be coupled with a remotely operated automatic explosives loader that can both load the holes with an exposure charge 14 / detonator 16 combination via an explosures vehicle processor 96 and then remotely detonating the blast face safely and economically. A wireless modem 114 receives the initiation signal from the leaky coax cable 90. The acoustic detonator mobile base transmitter 92 operates in a similar manner as does the previously discussed acoustic detonator base transmitter 26.
While in accordance with the provisions of the statute, there are illustrated and described herein specific embodiments of the invention, those skilled in the art will understand that changes may be made in the form of the invention covered by the claims and that certain features of the invention may sometimes be used to advantage without a corresponding use of the other features.
U.S. patent 5,159,149 to Marsden discloses a remote detonator system employing untethered radio frequency (1tF) transmitters and receivers. Each detonator must be physically coupled and uncoupled with a combined charging energy storage means and a programmable delay time means prior to shot initiation.
Canadian patent 1,309,299 to Beattie et al., discloses a wireless system including detonation means capable of receiving ItF signals from a remote source hardwired to a fuse via connecting wires.
Canadian patent 1,298,899 to Beattie et al., discloses a dual detonation system employing RF and a steerable laser beam.
Wired designs include U.S. patent 5,295,438 to Hill et al, and U.S. patent 5,520,114 to Guimard et al. The former patent discloses a transportable programming tool and a control loop. Each detonator is affixed to a split core which is hooked to the loop. The latter patent discloses a feedback programming unit and an integrated electronic delay detonator.
Current commercially available detonation systems still ultimately require physically connecting wires to each detonator regardless of the mode of initiation.
The purpose of the present invention is to provide a remote wireless untethered acoustic blast initiation system. The need for such a system comes from a greater requirement to automate the entire mining process. A key part of the underground hard rock mining process is blasting. In order to automate blasting, a technique is needed to allow for the wireless initiation of a blast. Wiring a blast is a labor intensive manual process requiring a person to physically connect wires to each detonator. As well, many different time delays are required for the blast. Since development blasts can have a blast pattern containing 80 or more detonators, the possibility for human error is high. These errors occur in the placement of a detonator with the wrong timing in a hole.
Incorrect placement and timing of the blast pattern creates poor break" bootlegs, loose rock, varying muck size and damage to the opening. This in turn raises safety issues and creates higher mining costs.
Assignee has developed a successful prototype 1tF remote detonator system wherein a coded 1iF triggering signal is transmitted from an RF transceiver to one or more wireless 1tF detonators. The 1tF signal programs the RF detonators' time delay and initiates the blast.
The difficulty with RF initiated remote systems relates to the problematic transmission and reception of the 1tF signals through underground rock and ore.
Electrical signals are attenuated and do not travel through these mediums very far. To ensure that the detonators receive programming and initiation signals, the detonators require antennae that protrude out of the blasthole. Antennae are relatively fragile and are subject to damage. Moreover, they pose handling and loading problems, particularly when utilized with automatic loading devices. The spider web of antennae is easily dislodged.
As an alternative, acoustic triggering was considered. Mindful that structures, especially mines, are subject to a bewildering array of noise and vibration from numerous sources-blasting, hauling, drilling, machinery, etc., the safety of acoustic based detonator systems was carefully considered.
It is known that noise is capable of traveling great distances underground through solid and liquid mediums such as rock, ore and water. The instant inventors believed that by harnessing, modulating and analyzing vibration within rock, a safe dependable acoustic-based detonating system could be developed. Alteration of acoustic signals can be calculated and physically measured to initiate an explosive charge.
The present invention allows data from a computerized blasting design program to be transferred directly to the detonators and the automatic machine installing them.
This reduces error and allows for a machine to automatically install the detonators. The elimination of wires greatly reduces the complexity of the automated machine required to install the detonators. The elimination of wires or other tethers such as shock tubes also eliminates the chance of the tethers being cut by the blast before the initiation signal can .4_ propagate to the other detonators. This creates a poor blast i.e. oversize chunks, poor perimeter contour and bootlegs. All of these factors create additional worker hazards, decrease e~ciency and raise costs. Efficiency and safety of the process is also improved since the blast design data is immediately available to the blast operator and is transferred by computer file instead of being read and acted upon by a person.
In summary, conventional detonators come with preset times, creating the need to stock many dii~erent detonators, each with individual time delays. In contrast, the present acoustic system allows one detonator to be stocked and allows for much finer control of the blast by allowing a higher resolution and greater number of delay times.
The detonators may be timed in I millisecond (ms) increments up to 10,000 ms, giving total timing control. These times are determined by measuring rock properties.
Matching the timing to the rock properties gives consistent fragmentation, which is required in automated mining.
An advantage of using acoustic communication as opposed to ItF initiation is that there are no cumbersome antenna wires. They are easily damaged and may also be easily pulled out of the detonator causing failure to fire the detonator resulting in undetonated explosives remaining in the blasthole. Moreover, the initiating acoustic signal to the acoustic detonators can be sent over relatively long distances underground through solid materials.
,SUMMARY OF THE INVENTION
Accordingly, there is provided an acoustic detonator system that is adapted to initiate a timed sequential blast pattern by an acoustic signal transmitted to each individual detonator.
A remote central processing unit (CPU) programmed with detonator programming software communicates with an acoustic base transceiver. The acoustic base transceiver communicates with at least one remote dedicated acoustic detonator affixed to an individual charge. The acoustic detonator interprets the signal, disregards extraneous and potentially dangerous "noise" and fires off an internal fuse directly setting off the associated charge.
-S-PC-~t 177 B~tIEF DESCRIPTION OF'~~ D,~~~TGS
Figure 1 is an overall schematic diagram of an embodiment of the invention.
Figure 2 is a schematic diagram of an embodiment of the invention.
Figure 3 is a schematic diagram of an embodiment of the invention.
Figure 4 is a schematic diagram of an embodiment of the invention.
Figuro 5 is a schematic diagram of an embodiment of the invention.
Figure 6 is a schematic diagram of an embodiment of the invention.
Figure 7 is a schematic diagram of an embodiment of the invention.
Figure 8 is a schematic diagram of an embodiment of the invention.
Figure 9 is a schematic diagram of an embodiment of the invention.
Figure 10 is a schematic diagram of an embodiment of the invention.
Figure 11 is a sample waveform.
Figure 1 depicts a schematic representation of the remote acoustic detonating system 10. A programmable controller 12, preferably a computer, ultimately communicates via acoustic energy or sound waves 18 through a medium such as solid ground 20 to one or more discrete explosive charges 14 or 14(A) ("A" equaling 1, 2, 3,....).
Each explosive charge 14 includes its own si~x~ and ~dicated microacoustic detonator 16 or 16A ("A" equaling 1, 2, 3,....). For non-limiting simplicity, any reference to an individual component will include multiple iterations unless indicated to the contrary.
Acoustic transmitting transducers 22, such as piezoelectric devices, microphones, sonic transducers, speakers, flat panels, pingers, etc. generate the sound waves 18 of appropriate wavelength, amplitude, frequency and duration to travel to and safely trigger the explosive charges 14. Similarly, acoustic receiving transceivers 24, which may be identical to the transducers 22, receive the transmitted sound waves 18 for interpretation and detonation. The receivers 24 are generally small enough to be integrated into or affixed to the detonator 16 so as to be easily fit into a blast hole.
By virtue of the controller's 12 software, once a firing program has been initiated, 13 an acoustic trigger will target each batch of detonators 16. By reducing or eliminating wired connections between the controller 12 and the blast site, the difficulties posed by the prior art direct hardwired or wireless antenna based systems are reduced.
In the embodiment depicted, the inventors utilized Inco Limited's preexisting broadband CATV communications network 32 connecting surface structures to underground mine locations. However, as will become apparent, any communication system bridging the controller 12 and the blast site may be used.
The system 10 includes the controller/computer 12 (preferably equipped with Microsoft Windows~ 95 or NT~ (or later), and Inco Limited's proprietary Telebiast AT"~ blast control software [copyrighted copies are available from Inco Limited]), a local acoustic detonator base transmitter 26 ("acoustic transmitter") and one or more remote acoustic detonators 16.
The computer 12 communicates with the acoustic transmitter 26 using its serial communications port (COM 1 ). The acoustic transmitter 26 modulates the data stream coming from the computer 12 onto the acoustic wave signal 18. The acoustic wave signal 18 is received by the acoustic detonator 16 and is demodulated to provide data for a central processing unit 36 located in the acoustic detonator 16. See Figure 3.
_7-As briefly stated previously, Figure 1 demonstrates Inco Limited's abovegound/undergound communications system in an abbreviated fashion. The controller 12, which may be stand-alone or part of a larger comprehensive mining control system and may be disposed above ground 28 or in any secure remote location, is connected to a conventional serial to ethernet converter 30 via a RS-232 serial bus 104.
The signal is passed through the conventional network 32 to a first standard modem 34.
The modem 34 in turn is connected to the acoustic transmitter 26 conveniently disposed underground, that is, below ground 28. The communications link is passed underground through a main broadband underground communications trunk system 100.
A branch line 102 offthe trunk 28 is diverted to the modem 34. The modem 34 in turn communicates with the acoustic base transmitter 26.
As one skilled in the art will readily appreciate, the means for communicating and transmitting a signal from the controller 12 to the acoustic transmitter 26 may be as varied as desired depending on site considerations, available equipment, permanence, finances, etc. It is within the realm of this invention that in non-mining situations such as construction, oil, gas, demolition, quarrying, etc., the distance and communication system may be relatively short, line of sight, wireless and simple. In other situations, such as underground or under water, the communication system traversing the controller 12 and the acoustic ddonator base transmitter 26 may be sophisticated and greatly spaced.
Whatever the conditions, one skilled in the art is capable of causing the controller 12 to communicate with the acoustic transmitter 26.
In particular, the instant system 10 allows for easy integration onto a conventional two-way network 32 such as one typically installed in underground mines.
The system 10 takes advantage of existing cable and network infrastructure already installed thereby reducing cost. The cost of installing dedicated wiring is eliminated.
Security of communications is ensured by using blast control software employing a mathematical coding scheme, cyclic redundancy check ("CRC"), addressable detonators 16, a dedicated broadband CATV channel and a distinctive acoustic signal.
_g-The system 10 unabashedly takes advantage of the ever increasing and amazing reductions in electronic component size and cost. The components making up the acoustic detonator 16 can be made so small and cheaply that they are literally expendable.
By physically mating the acoustic donator 16 to each specific charge 14, the safety and efficiency of explosive blasting is considerably camped up.
In the present discussion, particular manufacturers' components may be referenced for convenience. However, it should be understood that comparable alternatives may be substituted for the particular identified components. What must be t0 borne in mind is that a remote safety-triggering signal is transmitted from a remote initiation site to a transmitter 26. The transmitter 26 in tum generates an acoustic signal 18 to a distinct explosive charge 14. Each charge 14 includes its own stand-alone dedicated acoustic detonator 16. The acoustic detonator I6 interprets the signal from the transmitter 26 and, if conditions are appropriate, initiates the explosive sequence.
In Figure 2, the controller 12 is shown connected to the acoustic detonator base transmitter 26 (minus intermediate connections). Figure 3 is a schematic of an acoustic detonator 16.
The controller 12 is programmed with the appropriate software and commands the system 10. The Telebfast AT"' blast control software:
a) computes the CRC for communication verification and integrity.
This is a method for checking the accuracy of a digital transmission over a communications link. The computer 12 performs a calculation on the data and attaches the resulting CRC
value to the communication data stream; the transmitter CPU 38 performs the same calculation and compares its result to the original value in anticipation of a hand shake confirmation. If they do not match, a transmission error has occurred and the receiving CPU 38 requests retransmission of the data;
b) allows an operator to program: a blast batch identification number, a detonator identification number and detonator delay time in milliseconds (0 to 10000) into each detonator;
s a c) allows an operator to initiate a common fire command to start a countdown from each individual detonator delay setting for all detonators within a batch;
d) allows programming and initiation over a secure networked communication system via the modem 34.
The acoustic detonator base transmitter 26:
l0 a) transmits coded acoustic signals. It communicates with the detonator CPU 36.
The CPU 38:
a) encodes the batch identification number, detonator identification number, detonator delay times, CRC, arm and fire codes.
The transmitter (Tx} 48 includes:
a) modulation circuitry which modulates encoded transmit data. It uses a FSK (frequency shift keying) modulation format.
b) driver circuitry which takes the tow voltage and low current signal of the modulation circuit and provides enough current and voltage to drive the acoustic transducer 22.
The transducer 22 converts modulated electrical energy into modulated acoustical energy. For underground applications it is preferably coupled to solid ground or rock 20.
The acoustic detonating system 10 may be used in non-gaseous mediums such as solid-like earth formations, rock, underground mines, quarries, tunnels, construction and demolition sites, etc.. It may be also used in liquid environments such as bodies of water, rivers, liquid conduits, pools, etc. As long as the non-gaseous medium is capable of effectively transmitting an acoustic energy (sound) wave to the ultimate destination, the instant system 10 may be employed in many situations. Naturally in water environments the components need to be sufficiently waterproofed.
r The acoustic detonator 16 receives and decodes coded acoustic signals:
a) The acoustic receiver 24 is an acoustic signal sensor such as a microphone (piezoelectric sensor in the prototype). The acoustic receiver 24 converts acoustic energy to electrical energy which it receives acoustic energy transmitted through rock and explosive emulsion.
b) The receiver (Rx) 50 consists of a receive buffer and demodulation circuit. The receive buffer amplifies the signal from the acoustic receiver 24 for use by the demodulation circuit.
The demodulation circuit demodulates the FSK signal into a data stream for use by the CPU 36.
c) The CPU 36 decodes coded data from receiver 50 consisting of batch identification number, detonator identification number, detonator delay times, arm command, fire command and CRC.
If appropriate, it outputs a fire command to relay 40.
d) The energy source 42, which may be a battery and/or capacitor, powers the acoustic detonator 16 including the receiver 50, the CPU 36, the relay 40 and the fuse 44 circuits. Discharge 98 begins upon turning on the roceiver 50 and the CPU 36.
A prototype acoustic detonating system 10 was built and successfully tested as shown in Figures 4-10. The following discussion relates to the prototype in greater detail.
For both the transmitter 26 and detonator 16, a MicrochipTM CPU PIC 16C63A
programmable microcontroller ("PIC") 52, 80 was chosen based on its low cost, functionality and ease of programming. The PIC 52, 80 is essentially a complete computer in a small, low cost package, with a central processor, random access memory (RAM) for temporary storage and programmable read only memory (PROM) for permanent storage of a software program.
To acoustically transmit and receive the binary sequence, several modulation schemes were identified including impulsive (hammer type), on-off keying (pinging) and frequency shift keying ("FSK", two separate frequencies representing on and off. For the prototype, FSK was used.
The transmission circuitry 56 was programmed to generate a binary 8-bit transistor-transistor logic ("TTL") (on-oil sequence. As shown in Figure 4, the TfL
signal is transformed by FSK modulating circuit 58 to an FSK signal large enough to drive via piezo driver circuit 60 the acoustic transducer 22. Piezoelectric devices were used for the acoustic transducer 22 and receiver sensor 24 simply due to their availability and the ease with which they may be interfaced. For demonstration purposes, a 4-foot ( I .22m) high cylindrical column of concrete 54 was used to simulate transmission through rock. The driver circuit 60 amplifies the FSK signal to an appropriate level for the piezoelectric device 22.
The acoustic signal, after passing through the concrete 54, is received by the second piezoelectric device 24 also affixed to the concrete 57. In order to receive an adequate signal level, a buffer circuit 62 is used to provide signal gain from the piezoelectric device 24 to the remaining receiver system. The received FSK
signal is then passed through an FSK demodulation circuit I 08, resulting in the reproduction of the original TTL signal. The TTL signal is then inputted to the receive circuit 64 including PIC 80, where it is decoded to an 8-bit value. A valid detonation code is determined if the 8-bit value matched a predetermined value that was stored in the receiver PIC 80.
Upon reception of a valid detonation code, the receive circuit 108 energizes a thus simulating a detonation. If the data is not a valid detonation code, the LED remains de-energized and the receive circuit 108 continues to await another transmission.
The receive circuit 108 can be programmed with a variable time delay. Thus, the LED 68 can be programmed to energize after a programmed time delay, which simulates a delayed detonation signal to a detonator cap.
To control the acoustic detonator 16 circuits, software performs the following tasks:
s r a) on the transmit PIC 52 (see Figure S) the software, transmits one of two possible 8-bit binary numbers selectable by an electronic switch;
b) on the receive PIC 80 (see Figure 10), the software receives and decodes the 8-bit binary signal and determines whether it is a valid detonation command; and c) on the receive PIC 80, if the received code is valid, it simulates detonation by energizing the LED 68 after a determined time delay.
Turning now to the details of the prototype in greater detail.
The PIC 52 is used on the transmitter 26 to store and generate the detonation codes. Two separate 8-bit codes were required to demonstrate successful operation of the acoustic detonator 16 prototype. The ftrst code is a valid detonation code, which, when transmitted, will result in a simulated detonation. The srcond is an invalid detonation code, which, does not result in a simulated detonation, thus demonstrating that a specific 8-bit number is required to trigger a detonation. The 8-bit codes were chosen arbitrarily and can be assigned any value.
For brevity, in Figures 5 to 10, a number of the components such as resistors, capacitors, power supplies, amplifiers, etc. known to those skilled in the art will not be discussed.
Figure 5 is a schematic drawing of the transmit circuit 56. The transmit PIC
outputs the 8-bit code serially on pin 22 (RB1, Port B). This binary TTL
signal is then passed to the FSK modulation circuit 58. An electronic switch SW I is used to allow the user to select which 8-bit code was to be transmitted (i.e. the valid or invalid code). The switch SW 1 is connected to pin 23 (ltB2, Port B) and pin 24 (RB3, Port B).
When toggled, the switch S W I places on either RB2 or ltB3, thus selecting which code is to be transmitted. Two LEDs D1 (valid code) and D2 (invalid code) are connected in line with the switch SW 1 to display which code had been selected for transmission. A
momentary close switch SW2 is connected to pin 21 (RBO/INT). Pressing this switch asserts an interrupt on the PIC 52 resulting in the selected code being transmitted once (i.e. one shot operation).
The PIC 52 is powered by a SV regulated power supply. A 20MHz crystal 70 is placed across pin 9 (CLKIN) and pin 10 (CLKOUT), resulting in a SMIPS
instruction rate. An additional LED D3 is placed on pin 2 (RAO, Port A) which is energized when the PIC 52 is under normal operation.
The TTL binary signal from the transmit circuit 56 is FSK modulated by the circuitry shown in Figure 6. FSK modulation was chosen for its simplicity to implement and the control it allows over the frequency content of transmitted signals.
FSK was also chosen in order to reduce the risk of a narrow band interference source from initiating a detonation by virtue of it's frequency diversity. For ~monstration purposes, a center frequency of 2.SkHz was chosen arbitrarily with mark/space frequencies of 2kHz/3kHz.
IS Thus, binary 0 results in a 2kHz sine wave, while binary 1 produces a 3kHz sine wave.
To achieve this modulation technique, the FSK modulation circuit 58 was designed using a XR-2206T"' function generator integrated circuit 72 manufactured by EXART"~.
The circuit 58 is capable of converting a TTL keying signal (the 8-bit code) to a frequency-modulated sine wave. The mark/space frequencies are set by a combination of external resistors and capacitors.
The TTL signal from the transmit circuit 56 is input to pin 9 of the integrated circuit 72. Capacitor C1 (across pins 5 & 6) along with R1 (pin 7) and R2 (pin 8) determine the mark/space frequencies. The amplitude of the output sine wave may be adjusted by changing the resistor value of R3 connected to pin 3. However, for this demonstration the value was chosen to pmduce a 6V peak-peak sine wave. The FSK
output is located on pin 2 and is capacitively coupled to the driver circuit 60. The integrated circuit 72 was powered by a l OV regulated supply for the demonstration.
However, it is capable of operating over a range of 1 OV-26V. Frequency of operation 3o may be anywhere between 0.01 Hz - I MHz.
Turning now to Figure 7, there is shown a driver circuit 60. Due to the inefficiency of the piezoelectric material as a transmitter, a large voltage is required to successfully transmit an acoustic signal through several feet of concrete. The output from r the circuit 58 in the modulation circuitry only provides a 6V peak-peak signal. It was required to boost this signal to roughly 400V peak-peak to achieve a successful transmission. A step-up transformer 74 is used to achieve the boost. However, a buffer circuit is also required to provide the current to drive the transformer 74 and the transducer 22.
The transformer 74 is a simple wire wound iron core. The buffer circuit is comprised of an OF183TM operational amplifier 76 configured for unity gain.
The amplifier 76 was chosen for its high output capability arid fast skew rates.
The transformer 74 drives the acoustic transmitter 22.
A detonator 16 was assembled with three main subsystems:
1 ) Receiver buffer 62;
2) FSK demodulation circuit 64; and 3) Receive circuit 108.
For demonstration purposes, two detonators were assembled ( 16 and 16A - see Figure 4), on a single circuit board and, for simplicity, shared the receiver buffer 62 and FSK demodulator 64 subsystems. See Figure 8.
The buffer circuit 62 is required to provide signal gain from the piezoelectric sensor 24 for use by the FSK demodulation circuit 64. A second or mirror OP183T"~
operational amplifter 78 was chosen and configured as a unity gain amplifier.
The buffed signal is routed to the FSK demodulation circuit 64.
In Figure 9, the demodulation circuit 64 was designed to perform FSK
demodulation based on mark/space frequencies of 2kHzi3kI-Iz. This design incorporated a XR-221 I FSK demodulation integrated circuit 106 ("1C"). The mark/space frequencies are selected by setting external resistors and capacitors. The FSK signal from the input buffer 62 is capacitively coupled to pin 2 of IC 106. The signal must be between l OmV-3V to be recognized by the IC 106.
The iC l 06 is configured to output two signals. The first is a carrier detect (CD) signal that is used to indicate whether or not the IC 106 has locked on a valid carrier frequency (i.e. between 2kHz and 3kHz). If a valid frequency is detected, the CD signal is to I~ set to OV. Otherwise, a SV signal indicates that a valid frequency is not found and hence no data is received. The second output signal is the data output (DATA). The DATA signal is TTL level and is derived from the raceiv~ FSK signal. It should be noted that as long as the CD signal is high (i.e. no carrier detected), the DATA output signal is un-defined. The CD and DATA signals are sent to the receive circuit 108 for interpretation. The IC 106 is powered by a l OV (Vcc) regulated supply.
Figure 10 depicts the receive circuit 108. The receive circuit 108 having the PIC
16C 63A programmable microcontroller 80 ("receive PIC 80") on the detonator 16 is required to perform three functions. First, the receive PIC 80 determines whether the data it is receiving from the FSK demodulation circuit 64 is valid or noise induced. It does this through analysis of the carrier detect signal (GD). If the CD signal from the FSK
demodulation circuit 64 is logic high (i.e. 5V indicating no carrier due) the receive t 5 PIC 80 ignores the data signal it received. If the CD signal is logic low, then the receiver PIC 80 accepts the data signal as a transmitted code. The second function roquired of the receive PIC 80 is to transform the received data back into an 8-bit cod and LED 110 is lit. The third function is to ddermine whether or not the received code matches the expected detonation code. If a match is found, the receive PIC 80 simulates detonation through energizing LED 68 after a predetermined time delay. For the demonstration, the two detonators 16 and 16A were implemented. This allowed the user to demonstrate that one transmitted code would result in two separate time delayed detonations.
The cagier detect (CD) sigaal is input to pin 13 (RC2, Port C) of the PIC 80 and the data (DATA) signal is input to pin 12 (RC1, Port C). The LED 68 is connected to pin 4 (RA2, Port A). This LED 68 is energized to simulate a detonation. The PIC 80 is powered by a SV regulated power supply. A 20MHz crystal 112 is placed across pin 9 (CLKIN} and pin 10 (CLKOUT), resulting in a SMIPS instruction rate. An additional LED 82 is placed on pin 2 (RAO, Port A) which is energized when the PIC 80 is under normal operation. Several of these detonators 16 may be constructed, each simulating a detonator with a different blast time delay.
The PIC 80 for the detonator 16 is programmed as a serial communications receiver. When powered up, the PIC 80 initializes itself and immediately starts waiting for the caurier detect (CD) signal from the demodulator circuit 64. When the CD makes the transition from high to low, it is known that the IC 106 is recxiving data so the processor waits for the start bit. If no information is being sent from the transmitter, the default data sent is stop bits. The start bit is detected when the FSK data pin makes the transition from high to low. This activates TIMER1 in the PIC 80 and all subsequent samples of the FSK data pin 12 are taken based on this timer. The data format that the PIC 80 re~nizes is 7 data bits, 1 parity bit and 2 stop bits. The program then verifies that the data is in the proper format and that the parity is cornet. If the detonate code is valid, then the software times out and turns on the LED 68 which represents the detonate signet. If during any part of the data gathering process the PIC 80 stops detecting the CD
signal, the PIC 80 reverts back to its waiting for carrier detect state. If the data received is determi~d to be invalid, the program reverts back to its start-bit wait state. Invalid data can be caused by an invalid parity bit, insufficient stop bits, or an invalid detonate code.
The baud rate use in the serial communications was ar6ritrarily set to 62.5 BPS.
At an instruction cycle spend of 5 MHz and a timer pre-sealer of 8:1 for the module, one bit length corresponds to 10000 TIMER1 increments. This is the delay time that is used with the TIMERI interrupt to control the sampling of serial data.
The program is designed to work like a state machine, with clearly defined states and statatrnnsitions that govern the flow of the program. The machine advances states depending ~ the 2 external or 1 internal interrupt. These are the carrier detect (CD) signal coming from the PIC 80, the data detect (DD) interrupt coming from the PIC 80 or the TIMERI interrupt generated by the PIC 80. If the data received is invalid, the program flow will return to the start bit wait state.
The program for the transmit circuit 56 works as follows. On startup, the transmit PIC 52 is initialized and immediately starts sending out stop bits (logic high) to the FSK modulating circuit 58. The only external inputs to the circuit 58 are a button (switch SW2) connected to pin RBO, and a toggle switch SW 1 connecting either pin RB2 or RB3 to logic high. When the button on switch SW2 is pressed, an RBO
interrupt is created and depending on whether RB2 or RB3 is high a different code is sent to the FSK
modulating circuit 58. The signal is sent at 62.5 BPS to pin RB 1. This signal is timed -i 7-out exactly as it is in the receiver using TIMERI . Once the transmission is complete another transmission can be started if desired.
In summary, the acoustic detonator system 10 demonstrates the feasibility of acoustically triggering the detonation of a blast area. The objectives of the acoustic detonator system 10 demonstrates the following: .
a) to acoustically transmit a unique binary code;
b) to acoustically receive and recognize a unique binary code through rock;
c) to process the unique code as a detonation trigger and perform the function of a programmable time-delayed detonation source;
and d) to perform the detonator functions in a small autonomous package that can be reproduced simply and cheaply in large quantities.
To accomplish these objectives, the prototype detonator 16 and transmitter 26 were constructed using an inexpensive microcontrollers and piezoelectric sensors. The transmitter unit was programmed to send two different "detonation codes": an invalid and valid code. The prototype detonators were programmed to receive and recognize a unique code, designated as the "valid code" by the transmitter. The prototype detonators were successfully demonstrated; they recognized the detonation code, delayed by a preprogrammed period, and asserted a detonation signal.
In a fully operational system 10, the output from the receive circuit 108 would be routed, not to the LED 68, but the relay 40. The cascade of events from the receipt of the acoustic signal 18 will discharge 98 the explosive charge 14.
By employing the FSK paradigm, a customized signal 18 may be generated thereby causing the most efficient signal propagation through the various rock and ground conditions in a mine.
_ 18_ Two typical non-limiting signal characteristic cases are outlined below. A 31 bit code and a 63 bit wave packet code are contemplated. The 63 bit code can carry additional intelligence. Other wave packets may be acceptable.
Center fl Q Chip 31-Bit 63-Bit Chip 31-Bit 63-Bit Freq. (Hz) (Hz) DnratioCode Code DuratioCode Code (Tiz) n Length Length n Length Length (mSec) (mSec) (mSec) (mSec) (mSec) (mSec) Case Case Case Case Case Case 2 312.5 2 342 4 1240 252 80 248 5040 1546.25_ 171 _ _ _ ~ 160 __ 10080 142 ~ _ _ __ ~ _ 80 ~ 2480 r 5040 4960 ~
Figure 11 shows a 31 bit detonator coding code excerpt. Each acoustic detonator 26 will respond to a particular code sequence and duration. For example, the following code characteristics may apply to the excerpt shown in Figure 11.
F~(Hz) F=(JEIz) Tc(msec) 2294 2725 5 or 10 1157 1350 10 or 20 574 680 20 or 40 285 342 40 or 80 142 171 80 or 160 The amplitude of the signal is a function of the medium and the range.
However, preliminary indications for hard rock mines, such as those found in Sudbury, Ontario, Canada appear to be somewhere between 110-120 db re 1 uPa 1 m, where the sensitivity of receiver device 24 is about 85db re 1 uPa. Under perfect conditions this translates to a range of about 50 meters. However, it should be apparent that different mediums will require different signal characteristics, and the above parameters are non-limiting examples.
The design components are easily miniaturized for use in blast holes.
The acoustic detonating system 10 need not be static. Returning to Figure 1, a communications junction box 84 including a modem 86 and wireless modem 88 are connected to a leaky coax cable 90. The leaky coax cable 90 may be disposed throughout a mine and on different levels, drafts and stopes.
An acoustic detonator mobile base transmitter 92 mounted on a mobile vehicle is capable of being brought into close proximity to a blast site. It is contemplated that the transmitter 92 may be coupled with a remotely operated automatic explosives loader that can both load the holes with an exposure charge 14 / detonator 16 combination via an explosures vehicle processor 96 and then remotely detonating the blast face safely and economically. A wireless modem 114 receives the initiation signal from the leaky coax cable 90. The acoustic detonator mobile base transmitter 92 operates in a similar manner as does the previously discussed acoustic detonator base transmitter 26.
While in accordance with the provisions of the statute, there are illustrated and described herein specific embodiments of the invention, those skilled in the art will understand that changes may be made in the form of the invention covered by the claims and that certain features of the invention may sometimes be used to advantage without a corresponding use of the other features.
Claims (28)
1. An acoustic detonator system, the system comprising a controller, the controller communicating with an acoustic detonator transmitter, the controller adapted to generate an initiation signal, the acoustic detonator transmitter including a generator for generating an acoustic signal, the acoustic signal capable of propagating through a medium, an acoustic detonator having an acoustic signal receiver, the acoustic detonator capable of being associated with an explosive charge, the acoustic detonator transmitter adapted to recognize the initiation signal generated by the controller and transmit the acoustic signal to the acoustic detonator, and the acoustic detonator adapted to receive and interpret the acoustic signal to initiate the explosive charge.
2. The acoustic detonator system according to claim 1 wherein the acoustic detonator transmitter includes a first microcontroller, and the first microcontroller communicating with an acoustic wave generator.
3. The acoustic detonator system according to claim 2 wherein the acoustic wave generator includes a first piezoelectric unit.
4. The acoustic detonator system according to claim 2 where the acoustic detonator transmitter includes a first microcontroller and the acoustic wave generator, and a source of energy.
5. The acoustic detonator system according to claim 1 wherein the acoustic detonator includes a second microcontroller, and the second microcontroller communicating with the acoustic signal receiver.
6. The acoustic detonator system according to claim 5 wherein the acoustic signal receiver includes a second piezoelectric unit.
7. The acoustic detonator system according to claim 5 wherein the second microcontroller communicates with the acoustic signal receiver, a relay, a fuse, and a power supply.
8. The acoustic detonator system according to claim 7 wherein the fuse communicates with the explosive charge.
9. The acoustic detonator system according to claim 1 wherein the controller includes blast initiation programming for the initiation signal having recognition protocols, the acoustic detonator transmitter and the acoustic detonator adapted to learn, recognize and respond to the recognition protocols.
10. The acoustic detonator system according to claim 9 wherein the recognition protocols include a communications link, a blast batch identifier, a blasting cap identifier, a communication integrity verifier, a blasting cap delay instruction, and a fire command.
11. The acoustic detonator system according to claim 1 including a broadband connection between the controller and the acoustic detonator transmitter.
12. The acoustic detonator system according to claim 1 wherein the acoustic detonator transmitter includes means for accepting the initiation signal from the controller and a first central processing unit for interpreting the initiation signal and transmitting the acoustic signal away from the acoustic detonator transmitter.
13. The acoustic detonator system according to claim 1 wherein the acoustic detonator includes means for accepting the resultant signal, a second control processing unit for learning and interpreting the acoustic signal, blast initiation means responsive to the acoustic signal, and the acoustic detonator affixed to the dedicated explosive charge.
14. The acoustic detonator system according to claim 1 including a plurality of detonators.
15. The acoustic detonator system according to claim 1 including a plurality of dedicated explosive charges, each dedicated explosive charge affixed to a matching dedicated acoustic detonator.
16. The acoustic detonator system according to claim 1 wherein the acoustic signal generator is selected from the group consisting of a microphone, piezoelectric unit, sonic transducer, speaker, flat panel, and pinger.
17. The acoustic detonator system according to claim 1 wherein the medium is selected from the group consisting of a solid and a liquid.
18. The acoustic detonator system according to claim 1 wherein the acoustic detonator includes a microphone.
19. The acoustic detonator system according to claim 1 wherein the acoustic detonator transmitter includes a transmit microprocessor, a frequency shift key modulator communicating with the transmit microprocessor, an acoustic driver communicating with the frequency shift key modulator, a buffer circuit communicating with the frequency shift key modulator, and an acoustic wave generator communicating with the acoustic driver.
20. The acoustic detonator system according to claim 1 wherein the acoustic detonator includes an acoustic wave receiver, a signal buffer communicating with the acoustic wave receiver, a frequency shift key demodulator communicating with the signal buffer, and a receive microprocessor communicating with the frequency shift key demodulator.
21. An acoustic method of remotely initiating explosive charges by remotely activating detonators, the method comprising:
a) sending a initiation signal to an acoustic detonator transmitter, the initiation signal including preselected safety and firing parameters, b) causing the acoustic detonator transmitter to receive and interpret the initiation signal and, if appropriate, generate a resultant acoustic signal, c) causing the resultant acoustic signal to be transmitted through a medium, d) receiving the acoustic signal with an acoustic detonator, the acoustic detonator adapted to interpret the acoustic signal, and e) causing the acoustic signal, if appropriate, to initiate an explosive charge particularly dedicated and connected to the acoustic detonator.
a) sending a initiation signal to an acoustic detonator transmitter, the initiation signal including preselected safety and firing parameters, b) causing the acoustic detonator transmitter to receive and interpret the initiation signal and, if appropriate, generate a resultant acoustic signal, c) causing the resultant acoustic signal to be transmitted through a medium, d) receiving the acoustic signal with an acoustic detonator, the acoustic detonator adapted to interpret the acoustic signal, and e) causing the acoustic signal, if appropriate, to initiate an explosive charge particularly dedicated and connected to the acoustic detonator.
22. The method according to claim 21 including utilizing a plurality of acoustic detonators with associated explosive charges, and each detonator connected to a dedicated explosive charge.
23. The method according to claim 21 including sending the initiation signal to the acoustic transmitter via a broad band transmission.
24. The method according to claim 21 wherein the initiation signal includes recognition protocols, the acoustic transmitter determining that the recognition protocols are appropriate, and transmitting the acoustic signal to an acoustic detonator.
25. The method according to claim 24 wherein the acoustic detonator receives and interprets the acoustic signal to assess the recognitional protocols, and if appropriate, initiate an explosive charge.
26. The method according to claim 21 wherein the acoustic signal is encoded in a sound wave transmitted from the acoustic detonator transmitter to an acoustic detonator.
27. The method according to claim 21 wherein the initiation signal is modulated in a frequency shift key modulation format.
28. The method according to claim 21 including:
a) acoustically transmitting a unique binary code through the medium;
b) acoustically receiving and recognizing the unique binary code through the medium;
c) processing the unique binary code as a detonator trigger and, if appropriate, activating a programmable time-delayed detonation source; and d) detonating the explosive charge.
a) acoustically transmitting a unique binary code through the medium;
b) acoustically receiving and recognizing the unique binary code through the medium;
c) processing the unique binary code as a detonator trigger and, if appropriate, activating a programmable time-delayed detonation source; and d) detonating the explosive charge.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US75850301A | 2001-01-11 | 2001-01-11 | |
| US09/758,503 | 2001-01-11 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2367161A1 true CA2367161A1 (en) | 2002-07-11 |
Family
ID=25051959
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2367161 Abandoned CA2367161A1 (en) | 2001-01-11 | 2002-01-09 | Remote acoustic detonator system |
Country Status (4)
| Country | Link |
|---|---|
| AU (1) | AU1008202A (en) |
| CA (1) | CA2367161A1 (en) |
| FI (1) | FI20020039A (en) |
| NO (1) | NO20020116L (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7778006B2 (en) | 2006-04-28 | 2010-08-17 | Orica Explosives Technology Pty Ltd. | Wireless electronic booster, and methods of blasting |
| US7810430B2 (en) | 2004-11-02 | 2010-10-12 | Orica Explosives Technology Pty Ltd | Wireless detonator assemblies, corresponding blasting apparatuses, and methods of blasting |
-
2002
- 2002-01-08 AU AU10082/02A patent/AU1008202A/en not_active Abandoned
- 2002-01-09 CA CA 2367161 patent/CA2367161A1/en not_active Abandoned
- 2002-01-09 FI FI20020039A patent/FI20020039A/en unknown
- 2002-01-10 NO NO20020116A patent/NO20020116L/en not_active Application Discontinuation
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7810430B2 (en) | 2004-11-02 | 2010-10-12 | Orica Explosives Technology Pty Ltd | Wireless detonator assemblies, corresponding blasting apparatuses, and methods of blasting |
| US7778006B2 (en) | 2006-04-28 | 2010-08-17 | Orica Explosives Technology Pty Ltd. | Wireless electronic booster, and methods of blasting |
Also Published As
| Publication number | Publication date |
|---|---|
| NO20020116L (en) | 2002-07-12 |
| AU1008202A (en) | 2002-08-01 |
| FI20020039A0 (en) | 2002-01-09 |
| FI20020039A (en) | 2002-07-12 |
| NO20020116D0 (en) | 2002-01-10 |
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