TECHNICAL FIELD
[0001] The present invention relates to the field of tools and tool machines. In particular,
the invention relates to a grinding system comprising a grinder and a grinding wheel,
and a method to exchange information between the grinder and the grinding wheel of
the grinding system.
BACKGROUND
[0002] In the production of mechanical products, the finishing processes of the product
- such as deburring, grinding, sharpening and lapping - are fundamental in determining
the quality of the same.
[0003] These processes are typically implemented by means of dedicated tool machines, called
grinders or grinding machines. In detail, a grinder uses a tool, called grinding wheel,
to carry out the finishing process. The grinding wheel has an abrasive surface, typically
comprising a mixture of abrasive granules and a binding material. In use, the grinding
wheel and a workpiece to be machined are placed in contact with each other and one,
or both, are placed in motion. In this way, friction is generated by rubbing between
the abrasive surface of the grinding wheel and the product being machined which causes
an erosion of the grinding wheel and the desired finish of the product.
[0004] The friction between grinding wheel and product generates heat which can, in some
cases, damage the grinding wheel and/or the machined product. To avoid this problem,
grinding wheels have been proposed equipped with electronic devices designed to acquire
information on the operation of the grinding wheel, for example a working temperature
of the grinding wheel, and transmit it to a control unit of the grinder.
[0005] However, the operating conditions of the grinding wheel cause considerable complications
in the exchange of signals between the grinding wheel and the grinder. In particular,
the work environment is typically saturated with dust and noisy due to the interactions
between grinding wheel and product being machined. In addition, during operation the
grinding wheel rotates at high speeds and can be displaced along one or more processing
axes, as well as being subjected to mechanical stresses of varying intensity due to
the interactions between the grinding wheel and the product being machined.
[0006] Therefore, these working conditions make it difficult to implement in a simple and/or
economical way efficient communication systems that provide for the transmission of
signals by cable, or by optical or sound signalling.
[0007] The United States Patent no.
US 7,840,305 describes an abrasive tool for chemical-mechanical polishing (cmp), comprising a
substrate with two main opposite surfaces, and an abrasive material superimposed on
at least one of the two main surfaces. Furthermore, the tool comprises a means, for
example an RFID tag or a sensor, adapted to provide information on the cmp process
to a transmitter positioned near the substrate. The transmitter is adapted to receive
cmp information via wireless communication and transmitting it to a remote receiver.
[0008] The United States patent application
US 2018/158707 describes a system for semiconductor chip processing equipped with apparatus for
detecting, authenticating and tracing processing components comprised in the system.
In particular, a chemical mechanical polishing system (CMP) is illustrated which comprises
a plurality of remote communication devices (RFID) incorporated in a polishing disc
and configured to communicate with one or more interrogation devices of a plurality
of interrogation devices integrated in or coupled to CMP system components.
[0009] Although it allows overcoming some of the problems indicated above, the solutions
proposed in the United States patent
US 7,840,305 and in the United States patent application
US 2018/158707 do not explain how to solve the problems related to the variability of the intensity
of the signals exchanged between TAG and the RFID reader or one of the RFID readers.
The movement of the grinding wheel when grinding a workpiece, and the consequent variation
in the distance between TAG and the RFID reader, as well as the presence in variable
amounts of dust and processing scraps, in particular metal scraps, affect the quality
of the transmitted signal and make therefore a correct transmission of data between
grinding wheel and grinder difficult.
OBJECTS AND SUMMARY OF THE INVENTION
[0010] An object of the present invention is to overcome the disadvantages of the prior
art.
[0011] In particular, it is an object of the present invention to present a grinding system
comprising a grinder and a grinding wheel which guarantees an exchange of information
between grinding wheel and grinder that is reliable and robust.
[0012] It is also an object of the present invention to present a grinding system which
comprises a communication system between grinding wheel and grinder which is simple
to make but at the same time robust to interferences and insensitive to disturbances
due to the working conditions of the system.
[0013] Furthermore, it is a further object of the present invention to present a method
for transmitting information between the grinder and the grinding wheel in a simple
and reliable manner.
[0014] These and other objects of the present invention are reached by a system and a method
incorporating the characteristics of the appended claims, which form an integral part
of the present description.
[0015] A first aspect of the invention concerns a grinding system, comprising a grinding
wheel and a grinder. The grinder comprising an actuating arm adapted to receive an
abrasive grinding wheel, an actuator coupled to the actuating arm to rotatably drive
or translate it along a driving axis, and a transceiver unit (hereinafter also referred
to as PickUP) adapted to receive and transmit electromagnetic signals. The grinding
wheel is fixed to the actuating arm of the grinder and comprises a body which has
at least one abrasive surface intended to come into contact with a workpiece to be
machined, and an electronic unit (hereinafter also referred to as TAG) coupled to
the body. Advantageously, the transceiver unit is located in the grinder so as to
be separated from the abrasive grinding wheel and comprises at least one resonant
circuit, while the electronic unit of the grinding wheel comprises a further resonant
circuit having a resonance frequency equal to or close to (within a range going from
-15% to +15%, or better going from -10% to +10%) the resonance frequency of the at
least one resonant circuit of the transceiver unit. This allows information to be
exchanged between the electronic unit of the grinding wheel and the transceiver unit
of the grinder. The grinder further comprises a movement means suitable for moving
the transceiver unit along an axis parallel to the driving axis of the actuating arm,
and for maintaining the at least one resonance circuit of the grinder and the further
resonance circuit of the grinding wheel aligned during a translation of the actuating
arm.
[0016] This solution allows a good communication to be obtained between the devices despite
the fact that the grinding wheel is translated along a driving axis to compensate
for wear of the abrasive material.
[0017] In one embodiment the movement means is integral with the actuating arm. This allows
the resonant circuits of the grinding wheel and the grinder to be maintained always
aligned on a same plane transverse to the driving axis, guaranteeing a high electromagnetic
coupling. At each rotation of the grinding wheel, therefore, PickUP and TAG are able
to communicate for a time interval Δt dependent on the rotation speed of the grinding
wheel.
[0018] In one embodiment, the grinder further comprises an electronic control unit suitable
for supplying the transceiver unit with power, the electronic control unit being fixed
and connected to the transceiver unit by sufficiently long cables to maintain the
connection during the movement of the receiver unit between two end-of-travel ends.
[0019] This allows the electronic control unit to be maintained fixed and only the transceiver
unit to be moved. This offers several advantages: firstly, the electronic unit can
be supplied with power in a simple way, secondly the electronic unit can be used for
other functions of the grinder, so this solution makes it possible to upgrade an existing
grinder by simply reconfiguring or replacing the existing electronic unit and connecting
a mobile transceiver unit thereto.
[0020] Advantageously, in one embodiment the transceiver unit further comprises a signal
processing module, connected to the at least one resonant circuit and to a switching
element. The signal processing module is configured to switch, as a function of the
value of a bit to be transmitted, the switching element from a first condition in
which the at least one resonant circuit is connected to an oscillator module, to a
second condition in which the at least one resonant circuit is connected to a ground
potential. The signal processing module is configured to control the switching of
the switch as a function of a value of the bit to be transmitted.
[0021] This solution allows implementing a communication protocol based on the amplitude
modulation of a resonance signal that is generated when the resonant circuits of the
grinding wheel and the grinder are coupled.
[0022] In a preferred embodiment, the signal processing module of the PickUp is configured
to monitor the amplitude variations of at least one resonance signal (sn) sensed at
said at least one resonance circuit and to switch the aforesaid switching element
after detecting a first amplitude variation of said at least one resonance signal
(sn).
[0023] This solution allows implementing a fast and effective communication protocol that
does not require identification steps or data exchange prior to communication, as
instead occurs in some existing RFID systems. Data transmission occurs, in fact, when
the system detects the coupling between the resonant circuits, that is an increase
in the amplitude of the monitored resonant signal.
[0024] Advantageously, in one embodiment the electronic unit of the grinding wheel comprises
a second signal processing module coupled to a respective further resonant circuit
to monitor a second resonance signal sensed at the aforesaid further resonant circuit.
The signal processing module is also coupled to a switch element, and is configured
to switch, as a function of a value of the bit to be transmitted, the switch element
between a closed state, in which it short circuits the resonant circuit, and an open
state in which it does not short circuit the resonant circuit. The signal processing
module is configured to switch the switch element based on a value of the bit to be
transmitted. In particular, the second signal processing module is configured to monitor
the amplitude variations of said second resonance signal sensed at said further resonance
circuit and to switch the switch after detecting a first amplitude variation of said
second resonance signal.
[0025] This solution thus allows the electronic unit (TAG) of the grinding wheel to transmit
information to the transceiver unit (PickUp) of the grinder, and accordingly to the
latter's control unit, which can thus use the information coming from the grinding
wheel to control its operation, for example, change the rotation speed of the actuating
arm.
[0026] Advantageously, the control unit of the grinding wheel comprises a logic module,
connected to the second signal processing module to exchange data received and to
be transmitted, and a measuring circuitry for measuring a temperature of the abrasive
surface of the grinding wheel and connected to the logic module for providing a temperature
measurement. Preferably, the measuring circuitry comprises a temperature sensor arranged
in a seat formed in the grinding wheel body and a probe made of a good heat conducting
material. The probe is thermally connected to the temperature sensor and passes through
the grinding wheel body from the abrasive surface to the temperature sensor. The second
signal processing module switches the switch to transmit a plurality of bits corresponding
to the temperature measurement performed by said measuring circuitry.
[0027] In one embodiment, the electronic unit (TAG) of the grinding wheel comprises a battery
which supplies electrical energy necessary for the operation of the same electronic
unit. Preferably, a switch element is coupled to the battery and is adapted to selectively
enable the supply of electrical energy. Advantageously, an enabling assembly is coupled
to the switch element to close it at an intensity of the vibrations indicative of
an actuation of the grinding wheel or due to the effect of the centrifugal force developed
during its rotation.
[0028] Thanks to this solution it is possible to use a battery power supply and therefore
to ensure sufficient and substantially uniform electrical energy for the operation
of the electronic unit and at the same time to guarantee a consumption of electrical
energy limited to the periods of use of the grinding wheel e, therefore, an efficient
use of the electrical energy stored in the battery.
[0029] In one embodiment, the electronic unit includes an energy harvesting system. Advantageously,
the energy harvesting system is adapted to both generate electrical energy from sources
external to the electronic unit such as, for example, vibrations to which the grinding
wheel is subjected during operation, and to harvest electromagnetic energy exchanged
during the time interval Δt, at which PICKUP and TAG are aligned.
[0030] In this way, it is possible to guarantee at least part of the electrical energy necessary
for the operation of the electronic unit thus reducing, or eliminating, a dependence
on batteries of the electronic unit.
[0031] Another aspect of the present invention proposes a method for exchanging information
between a grinder and a grinding wheel.
[0032] Further features and advantages of the present invention will be more apparent from
the description of the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The invention will be described below with reference to some examples, provided for
explanatory and non-limiting purposes, and illustrated in the appended drawings. These
drawings illustrate different aspects and embodiments of the present invention and,
where appropriate, reference numerals illustrating structures, components, materials
and/or similar elements in different figures are indicated by similar reference numerals.
Figure 1 is a perspective view of an abrasive grinding wheel according to an embodiment
of the present invention;
Figure 2 is a schematic representation of a grinder according to an embodiment of
the present invention. In this figure, the grinder drives the grinding wheel of Figure
1;
Figure 3 is a schematic block representation of a grinding wheel and a grinder according
to an embodiment of the present invention;
Figure 4 is a graph showing waveforms of signals transmitted from the grinder to the
grinding wheel;
Figures 5A and 5B illustrate a flowchart of a method for the transmission of information
from the grinder to the grinding wheel according to an embodiment of the present invention;
Figure 6 is a graph showing waveforms of signals transmitted from the grinding wheel
to the grinder, and
Figures 7A and 7B illustrate a flowchart of a method for the transmission of information
from the grinder to the grinding wheel according to an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0034] While the invention is susceptible to various modifications and alternative constructions,
some preferred embodiments are shown in the drawings and are described hereinbelow
in detail. It is in any case to be noted that there is no intention to limit the invention
to the specific embodiment illustrated, rather on the contrary, the invention intends
covering all the modifications, alternative and equivalent constructions that fall
within the scope of the invention as defined in the claims.
[0035] The use of "for example", "etc.", "or" indicates non-exclusive alternatives without
limitation, unless otherwise indicated. The use of "includes" means "includes, but
not limited to", unless otherwise indicated.
[0036] Figure 1 is a perspective view of an abrasive grinding wheel 1 according to an embodiment
of the present invention. The grinding wheel 1 comprises a typically disc-shaped body
10, which has a first main surface 11 and a second main surface, or abrasive surface
13, mutually opposite and separated by a side wall 15. In the example considered,
the surfaces 11 and 13 are substantially circular with corresponding areas, and have
a diameter greater than the distance separating them, that is the height of the side
wall 15.
[0037] The body 10 of the grinding wheel 1 is at least partially made of abrasive material.
In particular, the body 10 comprises a portion of abrasive material which extends
from the abrasive surface 13 towards the first main surface 11. In one embodiment,
this portion of abrasive material can correspond to the entire body. The abrasive
material is suitable for use in subtractive manufacturing techniques, such as deburring,
grinding, sharpening, lapping and the like. Typically, the abrasive material comprises
a mixture of abrasive granules - having a hardness selected according to the material
to be machined - and a support material, adapted to act as a binder in order to keep
the granules joined in a predefined form.
[0038] Furthermore, the grinding wheel 1 comprises a connecting element 17, for example
a through hole or a hub, preferably with a longitudinal axis coaxial to an axis L
which corresponds, in use, to the axis of rotation of the grinding wheel 1.
[0039] In the example of figure 1, the connecting element 17 is a through hole that joins
the centres of the surfaces 11 and 13. By means of this through hole, the grinding
wheel 1 can be connected to a grinder 30, shown in Figure 3 and described below. For
example, the grinder 30 can be provided with an arm that fits into the through hole
17; the through hole is fitted into the arm until abutting against an abutment surface
of the arm and is fixed in position by means of a nut screwed on the free end of the
arm.
[0040] In an alternative embodiment (not shown), the first surface can be fixed to a flange
of the grinder by means of nuts embedded in the mixture of the grinding wheel. Said
flange comprises or is connected to the connecting element 17 mentioned above in order
to be mechanically connected to the grinder 30.
[0041] An electronic unit 20 is integrated in the grinding wheel 1, for example it is housed
inside a seat which opens onto the side surface 15 of the body 10. Advantageously,
as shown in Figure 2, the seat of the electronic unit 20 is arranged in proximity
of the first main surface 11 and, therefore, distal to the abrasive surface 13 which
is intended to come into contact with one or more products or workpieces 40 to be
machined. In the aforementioned alternative embodiment, in which fixing nuts are embedded
in the body of the grinding wheel, the housing seat of the electronic unit is positioned
in the body portion 10 comprised between the first main surface 11 and the nut that
is the furthest from this first main surface 11. In this way, the useful abrasive
portion of the body 10 is maximized.
[0042] In detail, as it is visible in Figure 3, the electronic unit 20 (hereinafter also
referred to as TAG) comprises a logic module 21, adapted to control the operation
of the entire electronic unit 20, a power supply circuitry 23, adapted to supply electrical
energy necessary for the operation of the components of the electronic unit, a measuring
circuitry 25, adapted to measure a temperature of the grinding wheel 1, a communication
circuitry 27, adapted to exchange data with the grinder 30, and optionally an RFID
module 29 adapted to store and transmit data concerning the grinding wheel 1. Furthermore,
the logic module 21 is connected to the communication circuitry 27 and to the RFID
module 29 for exchanging data therewith, and to the measuring circuitry 25 for receiving
temperature measurements.
[0043] The logic module 21 can comprise one or more from among a microcontroller, a microprocessor,
an ASIC, an FPGA, a memory and, possibly, one or more ancillary circuits, such as
a circuit for generating a synchrony signal (clock), amplifiers for input/output signals,
etc.
[0044] The power supply circuitry 23 comprises a battery 231, a switch element, for example
a transistor, 233, a piezoelectric sensor 235 and a conditioning module of the piezoelectric
signal 237. The battery 231 is connected through a first terminal to the remaining
components of the electronic unit 20, while a reference terminal (or ground) is selectively
connected to a second terminal through the transistor 233. A control terminal of the
transistor 233 is connected to the conditioning module of the piezoelectric signal
237 to which the piezoelectric sensor 235 is also connected. Briefly, the transistor
233, the conditioning module of the piezoelectric signal 237 and the piezoelectric
sensor 235 form an enabling assembly which allows the electronic unit 20 to be supplied
with power only when the grinding wheel 1 is used. In particular, the piezoelectric
sensor 235 generates an electrical voltage proportional to the mechanical stresses
to which the grinding wheel 1 is subjected. The conditioning module of the piezoelectric
signal 237 is designed to adapt this electrical voltage so that, for a predetermined
intensity of the vibrations - corresponding to an actuation of the grinding wheel
(1), the transistor 233 enters into conduction, thereby allowing the battery to supply
electrical energy to the other components of the electronic unit 20. As an alternative
to the piezoelectric sensor 235, a switch device activated by the centrifugal force
developed during the rotation of the grinding wheel can be advantageously used.
[0045] The measuring circuitry 25 comprises a temperature sensor 251 connected to a conditioning
module of the temperature signal 253. The temperature sensor 251 preferably comprises
a thermistor of the PTC type or, alternatively of the NTC type, and is connected to
the conditioning module of the temperature signal 253. In turn, the conditioning module
of the temperature signal 253 is connected to the logic module 21. During operation,
the temperature sensor 251 generates an electrical voltage proportional to the temperature
of the grinding wheel 1. The conditioning module of the temperature signal 253 is
designed to adapt, for example to amplify or linearise, such electrical voltage so
that it is correctly acquired by the logic module 21. Preferably, the temperature
sensor 251 is mounted on the electronic board 20 so as to face the abrasive surface
13 when the electronic unit 20 is associated with the grinding wheel 1. The logic
module 21 can also contain predictive algorithms that allow anticipating the temperature
reading in order to take into account the delay due to the limited thermal diffusivity
of the probe 50.
[0046] The communication circuitry 27 comprises a resonant circuit 271, connected in parallel
to a switch element 273, which are both connected to a signal processing module 275.
The signal processing module 275 is connected to the logic module 21 to exchange data
therewith and can comprise signal demodulation circuits, and control circuitry of
the switch element 273 for signal modulation. In particular, the signal processing
module 275 comprises circuits suitable for modulating in amplitude a signal to be
transmitted to the Pickup, and for demodulating in amplitude the signals coming from
the Pickup.
[0047] The RFID module 29 comprises a non-volatile memory in which the ID identification
data of the grinding wheel 1 such as a model code and/or operating parameters OP,
are stored, for example an indication of the hardness of the grinding wheel 1, the
dimensions of the abrasive surface 13, the height of the side wall 15, the rotation
speed for which the wheel is designed, etc. In one embodiment, the RFID module also
stores a threshold temperature value T
TH among the operating parameters OP of the grinding wheel 1 indicative of a maximum
surface temperature Ts that can be reached by the abrasive surface 13 without incurring
damage and/or deformation. In addition or as an alternative, the operating parameters
OP of the grinding wheel 1 can comprise a second threshold value T
MIN indicative of a limit surface temperature Ts below which the performance and/or the
productivity of the grinding wheel 1 is reduced. The ID identification data and the
operating parameters OP can be read at any time - for example, during storage, distribution
or during the installation of the grinding wheel 1 - also by means of an RFID reader
device independent of the grinder 30 without requiring the activation of the rest
of the electronic unit 20.
[0048] In a preferred embodiment of the present invention, the electronic unit also comprises
a probe 50. The probe 50 extends in the grinding wheel 1 starting from the abrasive
surface 13 up to the temperature sensor 29. In particular, the probe 50 is thermally
coupled to a detection surface of the temperature sensor 29, that is the thermistor
in the example considered. Preferably, a first end of the probe 50 is in contact with
the thermistor of the temperature sensor 29, while a second end is flush with the
abrasive surface 13.
[0049] Preferably, the probe 50 extends in a direction substantially transverse to the main
surfaces 11 and 13 of the body 10 of the grinding wheel 1, therefore substantially
parallel to the axis L of the grinding wheel 1. In particular, the probe 50 has an
elongated conformation, e.g. like a wire or a stick, with a main dimension substantially
greater than the others.
[0050] Advantageously, the probe 50 is made of a material that is a good thermal conductor.
The probe 50 transfers the heat which develops at the abrasive surface 13 directly
to the thermistor of the temperature sensor 29. Consequently, the temperature sensor
29 detects a temperature corresponding to the surface temperature Ts of the abrasive
surface 13.
[0051] With reference to Figures 2 and 3, in use, the grinding wheel 1 is mounted on an
actuating arm 31 of the grinder 30 to form a grinding system adapted to machine one
or more products, or workpieces 40. For example, the actuating arm 31 comprises a
pin which is inserted in the connecting element 17, and clamping elements which keep
the grinding wheel 1 integral with the actuating arm 31.
[0052] The actuating arm 31 is operatively coupled to an actuator 33, for example an electric
actuator. Typically, the actuator 33 is configured to impart a rotation about a driving
axis of the grinding wheel - corresponding to the axis L - of the grinding wheel 1
mounted on the actuating arm 31, and a translational movement, for example along the
same driving axis of the actuating arm 31.
[0053] The grinder 30 comprises an electronic control unit 35, which is configured to control
the operation of the grinder 30.
[0054] The control unit 35 of the grinder 30 can comprise one or more from among a microcontroller,
a microprocessor, an ASIC, an FPGA, a PLC and, possibly, one or more ancillary circuits,
such as a circuit for generating a synchrony signal (clock), amplifiers for input/output
signals, power supply circuitry, etc...
[0055] Advantageously, the grinder 30 comprises a user interface 37 provided with input/output
elements (not shown, for example a keypad and a screen) and operatively coupled to
the control unit 35 to allow an operator (not shown) to check and/or set an operation
of the grinder 30.
[0056] Furthermore, the grinder 30 can comprise - or be associated with - a spindle 38 adapted
to keep the workpiece 40 to be machined in position, for example a spring. Advantageously,
the spindle 38 is positioned so that the second surface 13 of the grinding wheel 1,
mounted on the actuating arm 31, faces the workpiece 40 to be machined. The spindle
38 can be replaced by other positioning devices able to keep the workpiece to be machined
in position during the interaction with the abrasive surface of the grinding wheel.
For example, the spindle can be replaced by a pair of jaws. In an alternative embodiment
(not shown), the workpieces to be machined (e.g. springs) are positioned on a workpiece-holder
disc able to house different workpieces to be machined. The workpiece-holder disc
preferably has an axis of rotation parallel to and spaced from the axis L of the grinding
wheel itself. The continuous rotation of the workpiece-holder disc progressively subjects
the workpieces to the abrasive action of the grinding wheel.
[0057] The grinder 30 also comprises a transceiver unit 39 operatively coupled to the control
unit 35, which allows the exchange of information between the electronic unit 20 of
the grinding wheel 1 and the control unit 35 of the grinder 30 as described below.
[0058] The transceiver unit 39 comprises a plurality of series resonant circuits 391 - ten
in the non-limiting example of Figure 2 -, an oscillator module 395, a signal processing
module 393 and a switching element 397. In detail, the resonant circuits 391 are arranged
in parallel with each other between the reference potential (or ground) of the transceiver
unit 39 and a common terminal of the switching element 397. The latter has a second
terminal which can be connected alternately to the oscillator module 395 and a third
terminal connected to the reference potential. Furthermore, each resonant circuit
391 is connected, via a respective intermediate terminal 3910, to a corresponding
reading terminal of the signal processing module 393.
[0059] In turn, the signal processing module 393 is connected to the switching element 397
to control it.
[0060] Finally, the control unit 35 is connected both to the oscillator module 395 to supply
it with power, and to the signal processing module 393 to supply it with power and
exchange data with the latter.
[0061] In an alternative embodiment, the signal processing module 393 can be implemented
in the control unit 35 of the grinder 30 instead of in the transceiver unit 39.
[0062] The transceiver unit 39 is positioned on the grinder 30 so as to be in proximity
of the side wall 15 of the grinding wheel 1, when the latter is mounted on the actuating
arm 31. Advantageously, the transceiver unit 39 is arranged in the grinder 30 in a
side wall thereof in a position radial to the grinding wheel 1; for example, so as
to be at a distance d - preferably, in the order of centimetres - from the side wall
of the grinding wheel 1 - as shown in Figures 2 and 3. Alternatively, the transceiver
unit 39 can be arranged in another position proximal to the grinding wheel 1, for
example on the actuating arm. In other words, the transceiver unit 39 is located in
the grinder 30 so as to be separated from the abrasive grinding wheel 1 fixed thereon.
In particular, the term 'separate' means that the transceiver unit 39 and the abrasive
grinding wheel 1 are not in direct contact nor are there any kind of wirings between
them.
[0063] In particular, the resonant circuits 391 are arranged aligned - or with at least
one of their inductive elements aligned - along a direction parallel to the driving
axis of the actuating arm 31 and therefore to the axis L of the grinding wheel 1 coupled
thereto. In this way, it is possible to guarantee a reliable electromagnetic coupling
between the resonant circuit 271 of the communication circuitry 27 and one or more
from among the resonant circuits 391 of the transceiver unit 39, even when the grinding
wheel 1 and, therefore, the communication module 27, is displaced parallel to the
axis of rotation. In fact, operationally, as the grinding wheel wears out, the grinder
lowers the grinding wheel support to keep the abrasive surface 13 in contact with
the workpieces to be machined. This involves displacing the resonant circuit in the
direction of the workpiece to be machined. As the resonant circuit 271 lowers, it
is coupled to a different resonant circuit 391. The transceiver unit 39 comprises
a number of resonant circuits 391 suitably arranged so as to ensure an efficient electromagnetic
coupling between resonant circuits 391 and 271 for the entire travel of the grinding
wheel 1 in the grinder 30. Summarizing, the resonant circuits of the transceiver unit
are arranged so that the resonant circuit of the communication circuitry 27 is electromagnetically
coupled to at least one resonant circuit 391 of the transceiver unit 39 along the
entire travel allowed, in use, to the abrasive grinding wheel 1.
[0064] The switch element 397 normally connects the oscillator module 395 to the resonant
circuits 391 providing them with a carrier signal having a frequency substantially
corresponding to the resonance frequency f
R of the resonant circuits 391 and 271. The term substantially corresponding is herein
understood to mean that the resonance frequencies of the resonant circuits 391 and
271 differ by a maximum of 15%, or more preferably differ by a maximum of 10%.
[0065] In use, the control unit 35 of the grinder 30 drives the actuator 33 to put the actuating
arm 31 and the grinding wheel 1 with it in a rotational and/or linear motion so as
to bring the grinding wheel 1 in contact with the workpiece 40 to be machined. In
order to effectively machine the workpiece 40, the control unit 35 of the grinder
30 exchanges information with - or at least receives information from - the electronic
unit 20 of the grinding wheel 1. The control unit 35 uses this information to adjust
the actuation of the actuator 31. Advantageously, the electronic unit 20 of the grinding
wheel 1 and the transceiver unit 39 of the grinder 30 exchange information in a reliable
and effective manner. The information transmitted by the electronic unit 20 of the
grinding wheel 1 is then transferred from the transceiver unit 39 to the control unit
35 and, vice versa, the information provided by the control unit 35 is transmitted
to the electronic unit 20 of the grinding wheel 1 from the transceiver unit 39.
[0066] In the preferred embodiment, the control unit 35 and the electronic unit 20 exchange
information (for example binary data) by exploiting the electromagnetic coupling between
the resonant circuit 271 and one or more of the resonant circuits 391. For this purpose,
the inductive L
T, the capacitive C
T and the resistive R
T elements of the parallel resonant circuit 271 are dimensioned to resonate at the
same frequency f
R at which the inductive L
n, the capacitive C
n and the resistive R
n elements (with n = [1, 2, ..., 10] in the considered example) of each series resonant
circuit 391 resonate.
[0067] The resonant circuits are able to periodically couple to each other for a communication
time interval Δt. The periodicity of the coupling is equal to the rotation time T
in which the grinding wheel 1 performs a rotation. In detail, during the rotation
of the grinding wheel, the resonant circuit 271 periodically passes in a position
proximal to the resonant circuits 391. As the grinding wheel rotates, the resonant
circuit 271 approaches the resonant circuits 391 and coupled thereto; in these conditions,
data transmission is now possible. As the rotation continues, the resonant circuit
271 begins to move away, so that after a communication time Δt the two resonant circuits
are sufficiently far away so that they are no longer coupled. In these conditions,
data transmission is not possible.
[0068] The control unit 35, through the transceiver unit 39, and the electronic unit 20
are configured to exchange information, for example an information corresponding to
a single binary data, or bit during one or more communication time intervals Δt. Preferably,
the control unit 35 is configured to operate as a main or master unit, while the electronic
unit 20 is configured to operate as a secondary or slave unit.
[0069] Referring to Figures 4, 5A and 5B, in the case of transmission from the transceiver
unit 39a to the electronic unit 20, the signal processing module 393 initially receives
(block 601) from the control unit 35 the information to be transmitted, for example
a string of one or more bits to be transmitted. In the example considered, the information
is transmitted sequentially - for example, a bit Btx at a time-, each during a respective
communication time interval Δt.
[0070] As illustrated in Figure 4, when the electronic unit 20 of the grinding wheel 1 passes
in proximity of the resonant circuits 391, through the region which from now on we
will define as operational, during the communication time interval Δt, one or more
resonant circuits 391 resonate with the resonant circuit 271. The electromagnetic
coupling between the resonant circuits of the TAG and the PickUp causes an amplitude
variation of one or more of the resonance signals s
n (indicated with COIL1, COIL2,...COIL10 in Figure 4) provided by the resonant circuits
391 and a corresponding variation in the amplitude of the resonance signal s
m provided by the resonant circuit 271 of the electronic unit 20.
[0071] The signal processing module 393 of the transceiver unit 39 is configured to select
(block 603) at least one resonance signal s
n, provided by a respective resonant circuit 391, to be used. Alternatively, the signal
processing module 393 of the transceiver unit 39 is designed to make the sum of the
signals s
n coming from the resonant circuits 391, so that, during the transition from a resonant
circuit to the other, the amplitude of the demodulated sum signal remains almost constant.
[0072] The signal processing module 393 generates (block 606) a digital signal D
n based on the resonance signal s
n selected, or based on the sum of the resonance signals s
n received as input in the alternative described above. In detail, the signal processing
module 393 is configured to demodulate - for example in amplitude - the resonance
signal s
n - or the sum of the signals s
n- obtaining a corresponding demodulated signal sd
n. The demodulated signal sd
n is digitized by the signal processing module 393, which converts the crossings of
a threshold value Athn of the demodulated signal sd
n into corresponding switchings of the digital signal D
n from a low logic value (for example, the reference voltage) to a high logic value
(for example, the power supply voltage) or vice versa.
[0073] Furthermore, the signal processing module 393 is configured to identify (decision
block 609) the initial time instant to of the communication time interval Δt. For
example, the signal processing module is configured to detect a switching from a first
logic value to a second logic value of the digital signal D
n, corresponding to a (first) crossing of the threshold value Athn by a demodulated
signal sd
n. In this embodiment, therefore, the crossing of the threshold value A
thn by the demodulated signal sd
n is then considered the start of the communication time interval Δt.
[0074] If the signal processing module 393 detects the start of the communication time interval
Δt (output branch Y of the decision block 609 and time instant to in Figure 4), the
signal processing module 393 selects (block 612) the information to be transmitted.
In the example considered, the signal processing module 393 selects the logic value
of a bit of the bit string to be transmitted received from the control unit 35, for
example, a logic "zero" in the left portion of Figure 4 and a logic "one" in the right
portion of Figure 4.
[0075] The signal processing module 393 is configured to measure an elapsed time of the
communication time interval to detect (decision block 615) that a guard time Tp -
lower than Δt - has been reached by the time instant to.
[0076] After the guard time Tp (output branch Y of the decision block 615) has elapsed,
the signal processing module 393 is configured to modify the amplitude of the resonance
signals s
n in order to transmit a bit having the desired value. In the example considered, the
signal processing module 393 compares (decision block 618) the logic value of the
bit to be transmitted and the logic value of the digital signal D
n with the instant Tp - for example, sampling the digital signal D
n - and determines the need to modify the amplitude trend of the resonance signal s
n based on a discrepancy between these logic values.
[0077] In the case wherein the logic value of the bit to be transmitted and the logic value
of the digital signal D
n do not correspond (output branch N of the decision block 618), the signal processing
module 393 maintains (block 621) the resonance signal s
n unchanged for the duration of the communication time interval Δt. In particular,
the signal processing module 393 maintains the switching element 397 closed between
the oscillator module 395 and the resonant circuits 391, thereby transmitting a bit
at a first logic value, for example 0 as illustrated in the left portion of Figure
4.
[0078] Otherwise (output branch Y of the decision block 618), the signal processing module
393 is configured to alter (block 624) the resonance signal s
n, thereby transmitting a bit at a second logic value, for example 1, as illustrated
in the right portion of Figure 4. In detail, the signal processing module 393 is configured
to switch the switching element 397 so that it connects the resonant circuits 391
to the reference potential, rather than to the oscillator module 393, for example
by switching a value of a control signal sp of the switching element 397. This quickly
cancels out the amplitude of the resonance signal s
n and, consequently, the resonance signal s
m on the resonant circuit 271 of the communication module 27. Preferably, the signal
processing module 393 is configured to maintain the resonant circuits 391 connected
to the reference terminal at least until the end of the communication time interval
Δt (that is, the closing time is greater than or equal to the difference between Δt
and Tp). This causes the resonance signal s
n to remain nil for the remaining part of the communication time interval Δt (that
is, Δt - Tp).
[0079] In parallel, the signal processing module 275 of the communication module 27 is configured
to generate (block 627) a digital signal D
m based on the second resonance signal s
m at the ends of the resonant circuit 271. Similarly to what has been described above,
the signal processing module 275 of the TAG device is configured to demodulate - for
example in amplitude - the resonance signal s
m read at the ends of the resonant circuit 271, obtaining a demodulated signal sd
m. The demodulated signal sd
m is digitized by the signal processing module 393, which converts the crossings of
a threshold value Athn of the demodulated signal sd
m into corresponding switchings of the digital signal D
m from a low logic value (for example, the reference voltage) to a high logic value
(for example, the power supply voltage) or vice versa.
[0080] Furthermore, the signal processing module 275 is configured to identify (decision
block 630) the initial time instant to of the communication time interval Δt for a
respective rotation period T of the grinding wheel 1. For example, the signal processing
module 275 is configured to detect a switching from a first logic value to a second
logic value of the digital signal D
m, that is a (first) crossing of the threshold value A
thm by the demodulated signal sd
m, and to consider this logic switching with the start of the communication time interval
Δt.
[0081] The signal processing module 275 is configured to measure an elapsed time of the
communication time interval in order to detect (decision block 633) that a respective
guard time T
T has been reached by the initial instant to of the communication time Δt.
[0082] After the guard time T
T (output branch Y of the decision block 633) has elapsed, the signal processing module
275 identifies (decision block 636) the bit contained in the second resonance signal
s
m and records the reception of a bit B
RX accordingly to which the high logic value (block 639) or the low logic value (block
642) will be associated. In detail, the signal processing module 275 is configured
to determine the logic value of the digital signal D
m. In the case wherein the digital signal D
m has a high logic value, the signal processing module 275 is configured to record
in a memory buffer a bit at a low logic value (left portion of Figure 4) or, vice
versa, to record a bit at a high logic value if the digital signal D
m has a low logic value (right portion of Figure 4).
[0083] Finally, the signal processing module 275 transfers the bits stored to the logic
module 21 of the electronic unit 20 of the grinding wheel 1.
[0084] The method 600 described above is reiterated (returning to block 603) at each period
T until the transmission of the bit string is completed and is implemented each time
the control unit 35 transmits a bit string to the transceiver unit 39.
[0085] In a preferred embodiment, the transmission of one or more bits is provided from
the electronic unit 20 to the control unit 35 of the grinder 30, preferably upon request
of the control unit 35. For example, the control unit 35 is configured to transmit
a predetermined bit string to the electronic unit 20 which is interpreted by the logic
module 21 as an instruction for the transmission of a datum, for example one or more
temperature measurements performed by the measuring circuitry 25.
[0086] The number of bits that can be transmitted is limited by the response speed of the
electronic circuits of the involved TAG and PICKUP and by the time Δt available for
data exchange. If the rotation speed of the grinding wheel is sufficiently low, it
is possible to exchange a complete ASCII character, thereby increasing the rapidity
of data exchange by a factor of 8 with respect to the case in which the data exchange
is limited to a single bit.
[0087] After that, the transmission of bits from the grinding wheel 1, that is from the
TAG, to the grinder 30, through the transceiver unit 39 (Pickup), occurs in a similar
way to what previously described for the reverse transmission.
[0088] Referring to the Figures 6, 7A and 7B, the signal processing module 275 of the communication
module 27 receives (block 701) from the logic module 21 a string of one or more bits
B
tx to be transmitted and, possibly, a transmission enabling signal (not shown).
[0089] Furthermore, the signal processing module 275 of the communication module 27 is configured
to generate (block 703) a digital signal D
m based on the resonance signal s
m that is generated at the ends of the resonant circuit 271 when it passes through
the operational region, during the communication time interval Δt.
[0090] Furthermore, the signal processing module 275 is configured to identify (decision
block 706) the start of the communication time interval Δt, in particular the initial
time instant t
0 of the communication time interval Δt. The start of the communication time interval
Δt is preferably identified using the same criterion adopted in the transceiver unit
39 of the PickUp, for example by verifying that the demodulated signal D
m changes logic value due to the electromagnetic coupling between the resonant circuits
of the TAG (271) and the PickUp (391).
[0091] Once the start of the communication time interval Δt (output branch Y of the decision
block 706) has been determined, the signal processing module 275 selects (block 709)
the information to be transmitted.
[0092] The signal processing module 275 is configured to measure an elapsed time of the
communication time interval Δt and to detect (decision block 712) that the guard time
T
T has been reached starting from the initial instant to of the communication time Δt.
Upon detection that the guard time T
T has been reached (output branch Y of the decision block 712) the signal processing
module 275 allows determining (decision block 715) whether the resonance signal s
m must be modified to transmit a bit at the desired logic value, in the same way as
described above.
[0093] In the case in which it is not necessary to modify the resonance signal s
m (output branch N of the decision block 715), the signal processing module 275 maintains
(block 718) the resonance signal s
n unchanged for the duration of the communication time interval Δt. In particular,
the signal processing module 275 maintains the switch element 273 open, thereby transmitting
a bit at a first logic value, for example 0 as illustrated in the left portion of
Figure 6.
[0094] Otherwise (output branch Y of the decision block 715), the signal processing module
275 is configured to modify (block 721) the resonance signal s
m, thereby transmitting a bit at a second logic value, for example 1, as illustrated
in the right portion of Figure 6. In detail, the signal processing module 275 is configured
to close the switch element 273 for example by switching a control signal s
t which controls the switch element 273. This forms a short circuit branch in parallel
with the resonant circuit 271 and the signal processing module 275. Consequently,
the amplitude of the resonance signal s
m cancels out quickly. Preferably, the signal processing module 275 is configured to
maintain the switch element 273 closed at least until the end of the communication
time interval Δt. This causes the resonance signal s
m to remain nil for the remaining part of the communication time interval Δt (that
is for a time Δt - Tp).
[0095] In parallel, the signal processing module 393 of the transceiver unit 39 is configured
to select (block 724) at least one resonance signal s
n, provided by a respective resonant circuit 391, to be used, similarly to what has
been described above.
[0096] The signal processing module 393 of the transceiver unit 39 is configured to generate
(block 727) a digital signal D
n built following the amplitude demodulation of the sum of one or more resonance signals
s
n that develop at the ends of the resonant circuits 391 or, as mentioned above, of
a resonance signal s
n selected (for example selected since it has a greater amplitude variation).
[0097] Furthermore, the signal processing module 393 is configured to identify (decision
block 730) the start of the communication time Δt for a respective rotation period
T of the grinding wheel 1.
[0098] The signal processing module 275 is configured to measure an elapsed time to detect
(decision block 733) that the guard time Tp has been reached starting from the initial
instant to of the communication time Δt.
[0099] As the guard time Tp has elapsed (output branch Y of the decision block 733), the
signal processing module 393 is configured to identify (decision block 736) the bit
transmitted by the TAG based on the logic value of the digital signal D
m and record in a memory buffer a bit B
RX received at the high logic value (block 739) or at the low logic value (block 742)
accordingly.
[0100] The operations described above can be repeated at each rotation of the grinding wheel
1, that is with a period T, so as to transmit the entire bit string (bringing the
operation back to block 703).
[0101] The invention thus conceived is susceptible to numerous modifications and variations,
all falling within this invention as resulting from the appended claims.
[0102] For example, nothing precludes providing a housing for the electronic unit 20 exposed
on the first main surface 11 of the grinding wheel 1.
[0103] In an alternative embodiment (not shown), the electronic unit 20 of the grinding
wheel 1 can comprise a different power supply circuitry 23; for example, provided
with an energy harvesting system from sources external to the electronic unit 20.
For example, the power supply circuitry can comprise one or more piezoelectric elements
coupled to an accumulator, for example a capacitor or a supercap, able to accumulate
electrical energy generated by the piezoelectric element due to the vibrations of
the grinding wheel. Alternatively, the energy used by the power supply circuit of
the TAG 20 can be, all or in part, harvested by the resonant circuit 271 during the
time communication interval Δt.
[0104] Furthermore, nothing precludes providing a grinder 30 in which the spindle 38, which
receives the workpiece 40 to be machined, is movable, in particular can be actuated
in rotation and/or rigidly translatable in the space. In detail, the movable spindle
38 can be implemented in a grinder comprising the movable actuating arm 31 described
above or, alternatively, in a grinder with a fixed support arm. As a further alternative,
the workpieces to be machined can be arranged on a conveyor belt, so as to be brought
sequentially into an operational position so as to be machined by the grinder 30.
[0105] Furthermore, it is possible to equip the grinder 30 with a movement means suitable
for moving the transceiver unit 39 along an axis parallel to the driving axis (L)
of the actuating arm, so as to maintain at least one of the resonance circuits 391
aligned with the resonance circuit 271 of the grinding wheel during a translation
of the actuating arm. The two circuits are considered to be maintained "aligned" if,
during their movement, a point of the resonant circuit 271 and a point of the at least
one resonant circuit 391 lie, at tolerances lower than ± 5%, on a same plane transverse
to the driving axis of the actuating arm. Said in other words, the movement means
allows a synchronous movement (or substantially synchronous if the tolerances are
considered) of the resonant circuits 271 and 391. Alternatively, in order to avoid
mechanical complications, it is possible to use only a resonant circuit 391 whose
dimension is sufficient to cover the entire displacement of the TAG 20, along the
axis parallel to the axis of rotation, due to the consumption of the grinding wheel.
[0106] The movement means can be equipped with an autonomous movement system (for example
it is possible to provide an electric motor controlled by the control unit 35), however
to guarantee a better coupling between the resonant circuits avoiding complications
due to an autonomous movement system, the movement means can be integral with the
actuating arm. For example, such movement means can comprise a bracket fixed to the
actuating arm; the transceiver unit 39 is then mounted on the bracket and is thus
translated integrally with the actuating arm.
[0107] It is yet possible to provide for the movement of both the transceiver unit 39 and
the control unit 35. However, preferably, the electronic control unit is fixed and
connected to the transceiver unit by sufficiently long cables to maintain the connection
during the movement of the transceiver unit 39 between two end-of-travel ends.
[0108] Even where a movement means for moving the transceiver unit 39 is provided, instead
of providing a plurality of resonant circuits 391 aligned along the driving axis L,
it is also possible to provide a resonant circuit 391 only. The communication system
and the circuit described above with reference to Figures 4 to 7 does not change except
for the number of the resonant circuits 391.
[0109] Finally, all details can be replaced by other technically equivalent elements. For
example, nothing precludes providing a grinding wheel 1 with a different conformation,
for example with a disc, a cup or a conical shape.
[0110] In an alternative embodiment (not shown), the side wall 15 is used as an abrasive
surface. In this case, the electronic unit 20 is arranged in proximity of the connecting
element 17 and the probe 50 extends radially from the temperature sensor 251 up to
the side wall 15.
[0111] In an alternative embodiment, the transceiver unit 39 and the communication unit
27 are configured to exchange an information comprising more than one bit during a
communication time interval Δt. For example, the resonance signals can be modulated
to transmit a byte (8 bits).
[0112] In another embodiment, the signal processing module 393 of the transceiver unit 39
is configured to select two or more resonance signals. In this case, the signal processing
module 393 can be configured to combine the resonance signals s
n and obtain a single digital reference signal.
[0113] In addition, nothing precludes implementing a procedure which envisages identifying
which one/s of the resonant circuits 391 of the transceiver unit 39 couple/s to the
resonant circuit 271 of the communication module 27, and determine a position or a
direction of movement of the grinding wheel 1, for example to verify the effective
positioning of the grinding wheel 1.
[0114] In alternative embodiments, the resonant circuits 391 illustrated in the figures
can be replaced by parallel resonant circuits, that is of the resonant circuit type
271 and can be one or more than one. In turn, in other embodiments, the resonant circuit
271 can be of the series type, such as those described above with reference to Figure
3. For the purposes of the present invention, it is therefore sufficient to provide
for the TAG and PickUp to have resonant circuits that can be coupled to generate resonance
signals, but the resonant circuits can be of the series type or of the parallel type.
[0115] In conclusion, the materials used, as well as the contingent shapes and dimensions,
can be whatever according to the specific implementation requirements without for
this reason departing from the scope of protection of the following claims.