Wireless communication device for measurement systems
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- RENISHAW PLC
- Filing Date
- 2022-04-06
- Publication Date
- 2026-08-03
Smart Images
Figure 0007899212000001 
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Abstract
Description
Technical Field
[0001] The present invention relates to a frequency hopping wireless communication module for use in a measurement system. In particular, the present invention relates to such a frequency hopping wireless communication module for use in a machine tool measurement probe and / or a related probe interface.
Background Art
[0002] Coordinate positioning devices (such as machine tools) often include a measurement device, such as a touch trigger probe that measures the position of a point on the surface of a workpiece. The touch trigger probe has a stylus that generates a so-called trigger signal when deflected by contact with the surface. This trigger signal is used to freeze the output of the machine tool's measurement scale, thereby indicating the position of the probe and, thus, with appropriate calibration, the position of a point on the surface of the workpiece.
[0003] In certain situations, for example, when it is difficult to directly wire the probe to the machine controller, a wireless transmission system is used to communicate the trigger signal to the machine controller via a probe interface. In particular, it is known to use frequency hopping spread spectrum (FHSS) communication between the probe and the probe interface. Such a communication protocol is described in International Publication No. 2004 / 057552 (WO2004 / 057552: Patent Document 1) and is also used in the "RMP" series of machine tool probes and related "RMI" probe interfaces sold by Renishaw plc, of Wotton-under-Edge, Gloucestershire, UK. A similar FHSS communication protocol is also used in the Primo series of measurement probes sold by Renishaw plc.
[0004] The FHSS systems described above have often proven to provide robust communication in harsh (RF) operating environments. While FHSS is typically the best option once operational, challenges arise in establishing communication when transitioning from a low-power "standby" (battery-saving) mode to an operational mode for measurement. In particular, before synchronization is established, neither the probe nor the interface knows which channel the other is operating on. Therefore, appropriate techniques must be employed to ensure that both ends of the link (probe and interface) reach the same channel simultaneously in order to successfully exchange data.
[0005] Renishaw's RMP system operates on 79 separate channels with a frame time of 1 ms. To establish communication, the interface stays on each channel in a hopping sequence for 79 ms, while the probe hops through the entire hopping sequence, changing channels and transmitting every 1 ms. This ensures that there is an opportunity for communication at least every 79 ms (provided a particular channel is not already occupied). Renishaw's Primo system operates on 79 separate channels with a frame time of 1.024 ms. To establish communication, the probe adjusts its frame time to 1.2 ms and transmits each frame. Ultimately, due to differences in "skew" timing, the probe and interface can reach the same channel simultaneously and establish communication. Furthermore, if an aligned channel is blocked, the next hop is still available to establish communication.
[0006] While RMP and PRIMO systems can reliably establish FHHS communication, this can take up to a quarter of a second, during which time the probe transmits each frame. The inventors have found this to be time-inefficient, undesirable from the standpoint of battery power consumption, and adds congestion to the RF environment.
[0007] International Publication No. 2014 / 091202 (WO2014 / 091202: Patent Document 2) describes a modification of the FHSS technology described in Patent Document 1 (WO2004 / 057552), wherein the probe interface includes a primary modem and a secondary modem. The primary modem is used to communicate with an active measurement probe (i.e., the probe used to acquire measurement values) via a first frequency-hopping spread spectrum radio link. The secondary modem is used to communicate with other measurement probe devices via a different frequency-hopping spread spectrum radio link. The communication link provided by the secondary modem is used solely to allow frequency-hopping synchronization with the other measurement probe devices to be maintained (i.e., measurement data is not received by the secondary modem). This configuration eliminates the need to establish frequency-hopping synchronization each time a different measurement probe device is used with the primary modem, since the necessary synchronization information is already known to the interface. Thus, it is possible to quickly switch the primary modem to communicate with different measurement probe devices. The technology described in Patent Document 2 (WO2014 / 091202) reduces the need to re-establish frequency hopping synchronization, but it consumes battery power, and periodic transmissions add congestion to the RF environment. Furthermore, if communication with the standby probe is lost (for example, if the probe moves out of the receiver's range), full frequency hopping synchronization must be re-established.
[0008] Frequency hopping systems are also known for general applications that are not specialized for measurement. International Publication No. 99 / 60718 (WO99 / 60718: Patent Document 3) describes a hybrid direct sequencing and frequency hopping communication protocol. U.S. Patent No. 4606040 (US4606040: Patent Document 4) describes a frequency hopping system employing high-speed and low-speed skip rules. [Prior art documents] [Patent Documents]
[0009] [Patent Document 1] International Publication No. 2004 / 057552 [Patent Document 2] International Publication No. 2014 / 091202 [Patent Document 3] International Publication No. 99 / 60718 [Patent Document 4] U.S. Patent No. 4606040 [Patent Document 5] International Publication No. 2018 / 134585 [Overview of the project]
[0010] According to a first aspect, the present invention includes a frequency-hopping wireless communication module for a measurement system, the communication module being configured to transmit and / or receive wireless signals using at least 10 different frequency channels within a frequency band, and to operate in a measurement mode and a standby mode for transmitting at least measurement data, wherein operation in standby mode includes hopping between fewer frequency channels than operation in measurement mode, Operation in measurement mode includes hopping between at least 10 frequency channels according to a first hopping pattern. Operation in standby mode involves hopping between at least three of ten frequency channels according to a second hopping pattern, where the three frequency channels are from different one-thirds of the frequency band.
[0011] Accordingly, the present invention relates to a frequency-hopping spread spectrum (FHSS) wireless communication module that can be used in a measurement system to establish FHSS (wireless) wireless communication links between different system components. In a preferred embodiment, the communication module of the present invention may be used for wireless communication of measurement data from multiple battery-powered measurement probes to a measurement interface that is physically connected (hardwired) to a machine tool. The communication module transmits and / or receives wireless signals over multiple frequency channels within a specific frequency band (for example, spreading across a 2.4 GHz wireless band).
[0012] The communication module is capable of operating in at least two different modes, namely, a measurement (first) mode and a standby (second) mode. Both the measurement mode and the standby mode implement a frequency-hopping communication protocol and, therefore, hop between different frequency channels according to a predetermined hopping pattern during use. Data packets may be transmitted and / or received on each such frequency channel.
[0013] The measurement mode is configured for transmitting measurement data. For example, the measurement mode may be configured to enable wireless transmission of measurement data from a measurement device to a measurement interface. The measurement data may include, for example, touch trigger event information, position measurements, ultrasonic measurements, temperature measurements, etc., depending on the type of measurement sensor provided as part of the measurement device. Therefore, it is preferable that the measurement mode uses a sufficient number of frequency channels to ensure reliable and robust communication even in the presence of many other wireless devices or RF interference. In particular, the measurement mode uses at least 10 different frequency channels. Thus, the measurement mode may implement a frequency hopping scheme similar to that described in Patent Document 1 (WO2004 / 057552).
[0014] Standby mode is not intended for the transmission of measurement data, but rather can be used to establish frequency-hopping synchronization between two communication modules. For example, multiple measurement devices may include communication modules that are placed in standby mode when they are not currently needed for measurement purposes. At that time, the communication module of each such measurement device may hop between frequency channels, waiting to receive an "on" signal from the communication module of the associated measurement interface.
[0015] As described above, the standby mode implements frequency hopping but uses fewer frequency channels than the measurement mode. In particular, the frequencies in standby mode hop between three channels. In a preferred embodiment, the measurement mode may hop between 39 or 79 channels. The fewer frequency channels used in standby mode (i.e., three) means that the communication link can be established quickly (which is important for the measurement system) but is still robust against interference. For example, if a communication module needs to periodically listen across all frequency channels for one cycle, it will be faster and use less power when only three frequency channels are used. This power saving is particularly important for battery-powered components of the measurement system. The standby mode can be terminated as soon as an ON command is received. In a preferred embodiment, the ON command also provides the information necessary to establish frequency hopping synchronization in measurement mode.
[0016] It should be noted that the communication module of the present invention can be implemented in various ways. For example, the communication module may include a well-configured circuit or processor (e.g., a transceiver). The communication module may also include an RF antenna, or be connectable to an associated RF antenna. As described below, the communication module may be incorporated into a measuring device (e.g., a measuring probe) and / or an interface for communicating with such a measuring device. Other components may be included within the communication module.
[0017] In an FHSS system, a so-called hopping pattern defines the frequency channels used for communication, along with the order in which those channels are used (i.e., the order in which they are hopped). Operation in measurement mode involves hopping between frequency channels according to a first hopping pattern. The first hopping pattern may include each of at least 10 frequency channels. In other words, all available frequency channels may be included in the first hopping pattern. Alternatively, it may be possible to use only a subset of all available frequency channels. Different first hopping patterns may be used for different communication modules. In particular, the order of the channels may differ for different communication modules to prevent communications clashes. The first hopping pattern may be derived from a unique identifier, such as a probe ID or serial number, which is a unique identifier for a communication module or measurement device. In this way, different first hopping patterns may be used in co-located systems, thereby reducing the possibility of conflict with adjacent systems by allowing many different hopping patterns to be created.
[0018] Operation in standby mode involves hopping between three frequency channels according to a second hopping pattern. As mentioned above, the second hopping pattern involves fewer channels than the first hopping pattern. The second hopping pattern involves a subset of multiple frequency channels. In other words, three of the available frequency channels form the second hopping pattern. All frequency channels used in the second hopping pattern may also be used in the first hopping pattern. In other words, frequency channels do not need to be reserved solely for standby mode communication. Different second hopping patterns may be used for different communication modules. In particular, the channels used and their order may differ for different communication modules to prevent communication collisions. The same number of channels may be used in each second hopping pattern. The second hopping pattern may be derived from a unique identifier. For example, a unique identifier for a communication module or measurement device, such as a probe ID or serial number. For the same reasons as above, the possibility of conflict with adjacent systems is reduced.
[0019] Advantageously, the frequency channels of the second hopping pattern are spaced apart across the operating frequency band. The three frequency channels are selected from different thirds of the frequency band. This helps ensure that any interference from a particular interference source (e.g., Wi-Fi® channels) is more likely to be avoided by hopping between different thirds of the frequency band.
[0020] As described above, the measurement mode preferably uses as many channels as possible to provide a reliable and robust wireless communication link. Therefore, operation in measurement mode involves hopping between at least 10, more preferably at least 20, or more preferably at least 30 different frequency channels. Operation in standby mode involves hopping between three frequency channels. In a preferred embodiment, three frequency channels are used in standby mode and 39 or 79 frequency channels are used in measurement mode. This provides good resilience in measurement mode and fast communication acquisition (synchronization) time in standby mode. Note that different frame rates may be used in standby mode and measurement mode. For example, a shorter frame rate may be used in standby mode, while the frame rate in measurement mode may have an adjustable length to accommodate different types of data communication.
[0021] Standby mode is preferably used for communication between two communication modules that do not involve the transfer of measurement data. Advantageously, information communicated in standby mode allows for the establishment of a communication link in measurement mode. For example, a master communication module operating in standby mode may establish a frequency-hopping communication link with a slave communication module also operating in standby mode. This communication link may be used to pass synchronization information between the master and slave modules, enabling both modules to enter measurement mode synchronously. For example, the clocks of the master and slave modules may be aligned, and a starting channel for a first hopping pattern may be specified. Then, both modules may begin hopping from the next frame (i.e., operating in measurement mode) according to the first hopping pattern, starting from the specified frequency channel.
[0022] The present invention also extends to a measurement device including the above-described frequency hopping wireless communication module. The measurement device may also include a measurement sensor for generating measurement data. The measurement sensor can be of any type. For example, it may enable measurements of dimensions, position, temperature, etc. The sensor can be a contact sensor (i.e., it can physically contact the object being measured), or it can be a non-contact sensor (e.g., it can use optical, inductive, capacitive, etc. sensing). In a preferred embodiment, the measurement sensor is a touch trigger sensor for measuring the displacement of a stylus (i.e., the measurement device includes a touch trigger probe). The measurement data generated by the measurement sensor is preferably transmitted to the relevant interface using the frequency hopping wireless communication module of the measurement device operating in measurement mode.
[0023] In a given system of communication modules, the same hopping pattern is used to enable coordinated hopping between frequency channels. As described above, communications used by different systems (i.e., different sets of communication modules) can benefit from using different hopping patterns to reduce the potential for interference when such systems are co-located. In a preferred embodiment, the measuring device includes a unique identifier. For example, each measuring device may be assigned a unique identification code. Then, the first and / or second hopping patterns used in measurement mode and standby mode can be derived from that unique code. In such an example, the unique identifier should be known by the measuring device and by the associated interface (e.g., by pre-programming or through a previous pairing process). This may allow both ends of a communication link to derive the same first and / or second hopping patterns for use in measurement mode and standby mode, respectively. Alternatively, one communication module may transmit a hopping pattern or pattern to the other communication module during the initial pairing or partnering process. For example, a measuring device may receive a hopping pattern used in measurement mode and / or standby mode from the relevant interface. This information may be transmitted during the initial partnering process.
[0024] The measurement device may be battery-powered. Therefore, it is advantageous for the measurement device to use as little power as possible to maximize battery life. Accordingly, the communication module of the measurement device may be configured to passively receive information (hopping between channels) until an activation message is received from the relevant measurement interface. The frame rate used when passively listening for an activation message may be greater than the frame rate of the relevant measurement interface. In particular, the duration of each frame used by the measurement device may be set to be at least equal to the time it takes for the relevant measurement interface to cycle through each frequency channel (e.g., cycle through a second hopping pattern). Once an activation message is received, the measurement device may send information to the measurement interface (e.g., to confirm receipt of the activation message).
[0025] The communication module of a measurement device can function as either a transmit master or a transmit slave. Measurement mode and standby mode may use different transmit masters to control the communication link. Preferably, the communication module of the measurement device functions as a transmit slave in standby mode. As a result, the communication module of the associated measurement interface can function as a transmit master. As described above, the communication module of the measurement device may passively receive signals while hopping between frequency channels according to a second hopping pattern until an activation message is received from the measurement interface. At that time, the communication module of the measurement device may switch from standby mode to measurement mode upon receiving an appropriate activation message from the associated measurement interface. The activation message may contain information that enables the establishment of frequency-hopping synchronization with the associated interface upon entering measurement mode. Upon entering measurement mode, the communication module of the measurement device can function as a transmit master (i.e., the measurement interface becomes a transmit slave). This is particularly advantageous when the measurement device needs to transmit information from asynchronous measurement events.
[0026] Note that the communication protocol may include an appropriate sequence of acknowledgments with redundancy (e.g., retransmission, etc.) to protect against non-receipt of messages due to interference or the like.
[0027] In a preferred embodiment, the measurement sensor of the measurement device includes a touch trigger sensor. The touch trigger sensor can generate a trigger signal when reaching a certain spatial relationship with a point on the surface of an object. For example, the trigger signal can be generated when a stylus is deflected. The measurement probe can be for a machine tool. This trigger signal can be communicated to an associated interface when the communication module is operating in the measurement mode. The measurement probe can also include at least one of a stylus, a shank, and a battery. Transmission of such a trigger signal (or any measurement data) may not be possible when operating in the standby mode. The measurement device can include a plurality of measurement sensors (e.g., a touch trigger sensor and a temperature sensor).
[0028] The present invention also extends to a measurement interface including the communication module described above. The measurement interface may be physically connected to the associated machine (i.e., not battery-powered). For example, the measurement interface may be connected (physically connected) to a machine tool controller. Advantageously, the measurement interface is for communicating with multiple associated measuring devices. The measurement interface may have one or more outputs for passing measurement data received from the associated measuring devices to the associated machine (e.g., a machine tool or an industrial PC). The measurement interface may include multiple different outputs for different types of measurement data. Analog probe data may be passed to an industrial PC for processing via Ethernet® or an industrial Ethernet link. Trigger signals generated by a touch trigger sensor may be passed directly from the interface to the machine tool controller via a real-time link. For example, such a touch trigger signal may be output by latching the voltage of a line connected to the controller's SKIP input, or by generating a pulse or a series of pulses that are passed to the SKIP input. Alternatively, the trigger signal may be passed to the controller 30 via a digital data bus (as described, for example, in International Publication No. 2018 / 134585 (WO2018 / 134585: Patent Document 5)).
[0029] The communication module of the measurement interface can function as a transmit master or a transmit slave. The measurement mode and standby mode may use different transmit masters to control the communication link. Preferably, the communication module of the measurement interface functions as a transmit master in standby mode. Therefore, the communication module of the associated measurement device may function as a transmit slave in standby mode. When operating in standby mode, the measurement interface may send an ON command or message for the required measurement device. This ON or ON command may be specific to one measurement device from several measurement devices operating in standby mode. Therefore, the measurement interface uses a second hopping pattern for the measurement device to be turned ON. The ON message may also include a header containing information about the measurement device to be activated (e.g., a probe ID). The communication module of the measurement interface may also be configured to receive acknowledgments from the activated measurement device. Once the ON message is successfully transmitted, the communication module of the measurement interface may enter measurement mode. The ON message may include information that enables the establishment of frequency-hopping synchronization with the associated measurement device upon entering measurement mode. When entering measurement mode, the communication module of the measurement interface can function as a transmit slave (i.e., the measurement device becomes the transmit master).
[0030] The measurement interface may include memory for storing a second hopping pattern. Each of the measurement interface and multiple associated measurement devices may store the same second hopping pattern. Alternatively, each of the multiple associated measurement devices may store a different second hopping pattern, and the measurement interface may store each of the second hopping patterns. In this way, any selected one of the multiple associated measurement devices can be activated and enter measurement mode, thereby enabling measurement data communication. The memory may also store a first hopping pattern. Each of the measurement interface and multiple associated measurement devices may store the same first hopping pattern. Alternatively, each of the multiple associated measurement devices may store a different first hopping pattern, and the measurement interface may store each of the first hopping patterns. The stored hopping patterns may be pre-calculated (e.g., during manufacturing). The hopping patterns may be generated separately from the module and then loaded into the module. In one embodiment, the first and / or second hopping patterns may be stored by the measurement interface and communicated to the relevant measurement device during the initial partnering or pairing process. Alternatively, the module includes a processor for calculating the hopping patterns. The hopping patterns may be calculated once and then stored in memory for future use. Alternatively, the hopping patterns may be calculated whenever they are needed (e.g., upon power-up).
[0031] The present invention also extends to a measurement system including one or more measuring devices (i.e., measuring devices or a plurality of measuring devices) and a measurement interface. Each component of the measurement system (i.e., each measuring device and measurement interface) may include a communication module of the present invention. Legacy communication protocols may also be provided for such components. In a preferred embodiment, the measurement system is for use on a machine tool.
[0032] As described above in relation to the measuring device and the measuring interface, the first and second hopping patterns of the measuring system may be transmitted to the measuring device by the measuring interface during the initial partnering process. The communication module of the measuring device may function as a transmit slave in standby mode. The communication module of the measuring device may switch from standby mode to measurement mode when it receives an appropriate activation message from the measuring interface. The activation message transmitted by the measuring interface may contain information that enables the establishment of frequency hopping synchronization with the measuring interface when entering measurement mode. The communication module of the measuring device may function as a transmit master when operating in measurement mode. The measuring sensor of the measuring device may include a touch trigger sensor that generates a trigger signal when it reaches a certain spatial relationship with a point on the surface of an object, and the trigger signal is passed from the measuring device to the measuring interface using measurement mode.
[0033] The multiple frequency channels used by the communication module may include frequency channels within the 2.4 GHz radio frequency band (spanning 2.4000–2.4835 GHz). This is also known as the Industrial, Scientific, and Medical (ISM) band and is license-free in most countries. Each frequency channel may be 2 MHz wide, but it should be noted that any transmission may only occur over a portion of the frequency range of each channel. In a preferred embodiment, 39 channels (each 2 MHz wide) are provided, spanning from 2.404 GHz to 2.480 GHz.
[0034] It should be noted that the present invention can be used in any radio frequency band and is not limited to ISM band operation. Preferably, the module is configured to operate in a standard license-free radio frequency band. It should be noted that such frequency bands may change from country to country or over time depending on regulatory rules, but this does not alter the advantages related to the present invention. It should also be noted that the communication module may be classified as a digital transmission system (DTS) or hybrid system, rather than an FHSS system, according to the formal definition of the Federal Communications Commission (FCC).
[0035] The communication module may be formed in any suitable manner. For example, the module may be formed as a circuit board (e.g., an FPGA module) for mounting within a measurement probe and / or within the measurement probe interface. The circuit board may implement other functions for frequency hopping communication or other processes. The module may also include one or more of the features described in Patent Document 1 (WO2004 / 057552).
[0036] Also described herein is a frequency-hopping radio communication module for transmitting and / or receiving radio signals using multiple frequency channels, wherein the communication module is operable in at least a first mode and a second mode, the second mode comprising hopping between fewer frequency channels than the first mode. The module may be used for measurement or any other purpose.
[0037] Also described herein is a method for using a frequency-hopping radio communication module for communicating measurement data. The method includes the step of transmitting and / or receiving radio signals using multiple frequency channels. The method further includes at least a measurement mode for communicating measurement data and a step of operating in standby mode. The step of operating in standby mode may include hopping between fewer frequency channels than the step of operating in measurement mode. The method may include one or more of the features described above for similar devices.
[0038] Also described herein is a measuring device comprising a measuring sensor for generating measurement data and a frequency-hopping wireless communication module configured to operate in a measurement mode and a standby mode for transmitting and / or receiving wireless signals using multiple frequency channels and for communicating at least measurement data, wherein the operation in standby mode comprises hopping between fewer frequency channels than the operation in measurement mode. The measuring device may have any one or more of the features described above.
[0039] Also described herein is a measurement interface including a communication module configured to operate in a measurement mode for transmitting and / or receiving radio signals using multiple frequency channels and for communicating at least measurement data, and in a standby mode, wherein operation in standby mode includes hopping between fewer frequency channels than operation in measurement mode, and the measurement interface also includes an output (or multiple outputs) for passing measurement data received from an associated measurement device to an associated machine. The kit includes the measurement interface and a measurement probe may also be provided.
[0040] Also described herein is a frequency-hopping radio communication module for a measurement system, the communication module being configured to transmit and / or receive radio signals using a plurality of frequency channels and to operate in a measurement mode for communicating at least measurement data, and in a standby mode, wherein the operation in standby mode includes hopping between fewer frequency channels than the operation in measurement mode. The operation in standby mode includes hopping between 10 or fewer frequency channels, more preferably 5 or fewer, or more preferably 3 or fewer. Such a frequency-hopping radio communication module may have any one or more of the features described above.
[0041] Next, the present invention will be described merely as an example, with reference to the attached drawings. [Brief explanation of the drawing]
[0042] [Figure 1] Figure 1 shows a machine tool measuring probe and probe interface. [Figure 2A] Figure 2A shows the frequency hopping pattern (of the conventional technology). [Figure 2B] Figure 2B shows the frequency hopping pattern (of the conventional technology). [Figure 3] Figure 3 shows the hopping patterns of the first (measurement mode) and second (standby mode) of the present invention. [Figure 4] Figure 4 shows the establishment of communication in standby mode. [Figure 5] Figure 5 shows a successful and immediate transition from standby mode communication to measurement mode communication. [Figure 6] Figure 6 illustrates how reliability can be incorporated into the transition from standby to measurement mode communication. [Modes for carrying out the invention]
[0043] Figure 1 shows a touch-triggered measuring probe 10 mounted on the spindle 12 of a machine tool. The measuring probe 10 has a deflectable stylus 14 with a tip 16 that contacts the workpiece. The measuring probe also includes a first frequency-hopping radio communication module 18, which is typically integrated into the body of the measuring probe but is shown separately in Figure 1 for clarity. The measuring probe interface 20 is mounted on a fixed component 22 of the machine tool structure and connected (typically via a cable) to a machine tool controller 24. The measuring probe interface 20 also includes a second frequency-hopping radio communication module 26.
[0044] The data is transmitted between the measurement probe 10 and the probe interface 20 via a frequency-hopping radio communication link established between the first frequency-hopping radio communication module 18 and the second frequency-hopping radio communication module 26. As described above, the first and second frequency-hopping radio communication modules need to hop between synchronized frequency channels in order to enable the communication link to be established. The sequence in which various different frequency channels are used is commonly called a "hopping pattern." Thus, a hopping pattern describes the order in which different frequency channels are used and ensures that both ends of the radio link are transmitting and receiving on the same frequency channel at the same time (after proper synchronization). In other words, a hopping pattern describes the sequence of "hopping" between different frequency channels. A hopping pattern also defines the set of frequency channels used for communication.
[0045] As will be described in more detail below, the present invention relates to the use of measurement and standby modes employing different hopping patterns. Therefore, further details of the system, such as how communication timing is established to ensure synchronized frequency hopping and how the reliability of communication of measurement data from the measurement probe to the probe interface can be improved by enabling data retransmission, are not described in detail herein. Further details of such features are provided in Patent Document 1 (WO2004 / 057552), the contents of which are incorporated herein by reference.
[0046] Referring to Figures 2A and 2B, it is shown how a single hopping pattern is established for the type of wireless probe and probe interface system described in Patent Document 1 (WO2004 / 057552) mentioned above.
[0047] The frequency-hopping radio system operates using 79 discrete frequency channels within the 2.4 GHz frequency band. For convenience, the frequency channels are numbered sequentially from channel 1 to 79, with frequency channel 1 being the lowest frequency and frequency channel 79 being the highest frequency. As shown in Figure 2A, all frequency channels have the same bandwidth of approximately 1 MHz. Note that Figure 2A shows only a portion of the channels for simplification.
[0048] The increment value is generated from the set of data bits of the probe identification code ("probe ID code") of the measurement probe. Therefore, this probe ID code is a unique identifier for the measurement probe. The hopping pattern is then calculated by adding the increment value (e.g., an integer "I") to the current channel to establish the next channel in the sequence. For example, I could take the value 4. As can be seen in Figure 2A, the first frequency channel in the hopping pattern is channel 1, followed by channel 5, then channel 9, and so on. The sequence also wraps back, so that in the example shown in Figure 2A, channel 2 follows channel 77. After the increment value (4 in this case) has been applied 78 times, all frequency channels have been used. Furthermore, since 79 is a prime number, no channel appears more than once in the hopping pattern. Therefore, regardless of the value of I, all 79 channels appear exactly once in the hopping pattern. As an alternative to the technology described in Patent Document 1 (WO2004 / 057552), the above version of the RMI / RMP product uses an algorithm to share unique data (such as probe identification codes) to generate a randomized (shuffled) hopping pattern.
[0049] Figure 2B shows the start of the hopping pattern derived using the method described with reference to Figure 2A. As mentioned above, the complete hopping pattern includes all 79 channels in an order determined by the increment value (I). This hopping pattern is then used for all communication between the measurement probe and the interface. If timing synchronization is lost, it must be re-established before communication becomes possible. Communication through the 79 individual channels takes place over a 1ms frame time (i.e., the time to transmit or receive on a channel). To establish or re-establish communication, the interface remains on each channel in the hopping sequence for 79ms, while the probe hops through the entire hopping sequence, changing channels every 1ms and transmitting. This ensures that there is an opportunity for communication at least every 79ms (provided that a particular channel is not already occupied). In practice, it has been found that it can take up to 0.25 seconds to establish communication, during which time the probe is transmitting on every frame. This is time-inefficient and undesirable from a battery power consumption perspective. It also increases congestion in the RF environment.
[0050] To speed up the establishment of frequency-hopping communication links, it may be possible to initiate the communication process using a fixed-channel system. However, fixed-channel systems have many potential drawbacks. These include the necessary planning and coordination of co-located systems, and a lack of resilience to interference and multipath effects. However, they have the advantage of faster communication synchronization because both the probe and interface are on the same channel. Bluetooth® Low Energy (BLE) uses such a fixed-channel approach to initiate communication. In particular, it reserves three channels as so-called "advertising channels." These three channels are predefined by the BLE protocol and are spaced apart from each other on the radio spectrum to avoid WIFI® interference. Fixed-channel communication is repeated sequentially on each channel, and information that enables the establishment of a complete Bluetooth (i.e., FHSS) communication link is provided through each fixed channel.
[0051] Next, the communication protocol of the present invention will be explained with reference to Figures 3 to 6.
[0052] The communication link of the present invention is operable in measurement mode and standby mode. These different modes use different hopping patterns, with the hopping pattern in standby mode including only a few (i.e., three) frequency channels. The hopping pattern in measurement mode may include all available frequency channels, which may be ordered in a manner similar to prior art systems (e.g., based on probe ID codes) or pre-derived using a suitable (e.g., shuffle) algorithm. The three subchannels in standby mode may also be extracted from unique data (e.g., probe ID codes) exchanged between the probe and the interface when the probe and interface are combined, or may be pre-defined. In one embodiment, the hopping pattern may be passed from the interface to the probe (or vice versa) during the initial partnering process. The process or algorithm used to derive the three subchannels preferably ensures that each of the three channels used in standby mode comes from a different third of the available bandwidth. This ensures that if interference is present in one of the three channels, the other two channels are spaced far enough apart to communicate on those channels instead. Furthermore, the multipath problem is addressed by forcing the wavelengths of the three channels to be sufficiently different.
[0053] Referring first to Figure 3, the top of the drawing shows a first hopping pattern containing 39 channels in the order selected as described above with reference to Figures 2A and 2B. A second hopping pattern containing only three channels (labeled "standby channels") is also shown.
[0054] Next, referring to Figure 4, we will describe how to establish a communication link in standby mode. In particular, during standby, both the measurement probe and the probe interface operate on only three subchannels (i.e., channels 4, 23, and 35 in this example) with a frame time period of 0.25 milliseconds (i.e., jump between them). When the probe needs to perform a measurement operation (i.e., when operation in measurement mode is required to communicate measurement data), the probe interface sequentially transmits a "start" request beacon on each of the three channels. This sequence of frequency channels employed by the interface is shown in the top row of Figure 4. During this period, the probe remains on each of the same three individual channels for four frame periods (i.e., 1 ms) before hopping to the next. The sequence of frequency channels employed by the probe is shown in the bottom row of Figure 4.
[0055] Therefore, assuming that at least one communication on the frequency channels is received, we can see that communication is established within 3 ms. This represents a significantly shorter "on time" that benefits overall current consumption (in the probe), resulting in class-leading battery life. Once communication is established, both the probe and interface switch to a 0.5 ms frame time and return to full-band frequency-hopping communication, with the probe acting as the communication master. In other words, once communication is established in standby mode, data is passed between the interface and probe, enabling communication in measurement mode (i.e., when there is hopping between all frequency channels according to the first hopping pattern).
[0056] This configuration has the advantage that the standby probe does not pollute the RF environment by performing unnecessary query scans to determine whether to start operation. Furthermore, the probe on time is significantly reduced, shortening the machine cycle time. The three subchannels are preferably different for each machine, which helps prevent communication collisions when attempting to turn on multiple probes simultaneously from different machines. In addition, battery life is significantly improved because the probes only receive signals for very short periods.
[0057] Referring to Figure 5, the successful reception of communication in standby mode and the transition to measurement mode are shown. In particular, it can be seen that the interface and probe communicate over frequency channel 4 during the first time slot. The communication is bidirectional and includes the probe receiving a message and sending confirmation that it has been safely received by the interface. The message received by the probe from the interface instructs it to move to the main operating band on a specific channel (channel 10 in this example), thereby the probe also transitions from transmit slave to transmit master. At that time, the probe and interface hop synchronously between channels using the first frequency hopping pattern. That is, communication in measurement mode is established using the information exchanged in standby mode.
[0058] Referring now to Figure 6, it should be remembered that it is impossible to guarantee that a response to a transmitted message will be received by the interface, and it is impossible to be certain that the original message to the probe was lost or that only the response was received. Thus, an example is provided of how communication robustness can be ensured.
[0059] Figure 6 shows the frequency channels used by the interface and the corresponding frequency channels of the probe. If the first transmission by the interface on channel 4 is not received by the probe, the interface continues to cycle through the frequency channels of the second hopping pattern. When both the probe and the interface are on channel 23, the transmission is received by the probe, but the probe's response is not received by the interface. Therefore, the probe jumps to the designated starting channel (channel 34) and begins hopping through the first hopping pattern (i.e., the probe enters measurement mode), but the interface is still cycling through the second hopping pattern.
[0060] The designated starting channel (shown in the top row of Figure 6) changes according to the first hopping pattern. In particular, each subsequent on message increments the channel on which the probe is requested to begin operating, as if hopping through the main band in measurement mode. If the interface is unable to establish communication with the measurement probe after a predetermined number of cycles of the second hopping pattern, it is assumed that the probe must have entered measurement mode. However, the interface knows which channel the probe is operating on, since it would follow the first hopping pattern if the probe entered measurement mode during any of the preceding slots. Therefore, the interface jumps to the latest destination channel (channel 1 in this example) to check whether the probe is active on that frequency channel. In particular, after all attempts to send on messages have been sent by the interface, it also transitions to measurement mode as a transmit slave on the next channel in the operating hopping sequence (i.e., if the probe receives any of them, the channel has been updated for each on transmit, so the probe and interface remain synchronized on the main band).
[0061] The above examples relate to measurement probes and probe interfaces, but the same frequency-hopping wireless communication modules can be used in other measurement devices. Similarly, the use of 79 or 39 frequency channels and operation in the 2.4 GHz wireless band are provided merely as examples and are not intended to limit the scope of the present invention. It should also be noted that while the frequency-hopping wireless communication modules of measurement probes and probe interfaces should share the same hopping pattern, such modules do not need to be completely identical in all embodiments. For example, one or all modules may include other features described in Patent Document 1 (WO2004 / 057552).
Claims
1. A frequency hopping wireless communication module and a measuring sensor for generating measurement data, The frequency-hopping wireless communication module is configured to transmit and / or receive wireless signals using at least 10 different frequency channels within a frequency band, and to operate in a measurement mode for communicating at least measurement data, and in a standby mode, wherein operation in standby mode includes hopping between fewer frequency channels than operation in measurement mode. The operation in the measurement mode includes hopping between the at least 10 frequency channels according to a first hopping pattern. The operation in the standby mode includes hopping between three of the at least ten frequency channels according to a second hopping pattern, wherein the three frequency channels are from different one-thirds of the frequency band. A measuring device, The measurement data generated by the measurement sensor is transmitted by the frequency-hopping wireless communication module operating in the measurement mode. The frequency-hopping wireless communication module functions as a transmit slave when operating in standby mode and as a transmit master when operating in measurement mode. Measuring device.
2. The measuring device according to claim 1, wherein the three frequency channels used when operating in the standby mode are spaced apart across the frequency band.
3. The measuring device according to claim 1, wherein the first and second hopping patterns are derived from a unique identifier.
4. The measuring device according to any one of claims 1 to 3, wherein the at least 10 frequency channels include at least 30 frequency channels.
5. The measuring device according to any one of claims 1 to 3, wherein the at least 10 frequency channels include 39 or 79 frequency channels.
6. The measuring device according to claim 1 or 2, wherein the information communicated in the standby mode enables the establishment of a frequency-hopping communication link in the measurement mode.
7. A measurement system comprising a measuring device and a measuring interface as described in claim 1, The measurement interface comprises a second frequency-hopping wireless communication module for receiving measurement data and an output for passing the measurement data to an associated machine, wherein the second frequency-hopping wireless communication module is configured to transmit and / or receive wireless signals using at least 10 different frequency channels within the frequency band and to operate in a measurement mode and a standby mode for communicating at least the measurement data, the operation in standby mode comprising hopping between fewer frequency channels than the operation in measurement mode, The operation in the measurement mode includes hopping between the at least 10 frequency channels according to the first hopping pattern, The operation in the standby mode includes hopping between three of the at least ten frequency channels according to the second hopping pattern, wherein the three frequency channels are from different one-thirds of the frequency band. Measurement system.
8. The measurement system according to claim 7, wherein the first and second hopping patterns are transmitted to the measurement device by the measurement interface during the initial partnering process.
9. The measurement system according to claim 7, wherein the frequency-hopping wireless communication module of the measuring device switches from the standby mode to the measurement mode when it receives an appropriate startup message from the measurement interface.
10. The measurement system according to claim 9, wherein the startup message transmitted by the measurement interface includes information that enables the establishment of frequency-hopping synchronization with the measurement interface when entering measurement mode.
11. The measurement system according to any one of claims 7 to 10, wherein the measurement sensor of the measurement device includes a touch trigger sensor that generates a trigger signal when it reaches a predetermined spatial relationship with a point on the surface of an object, and the trigger signal is passed from the measurement device to the measurement interface using the measurement mode.