A system with modular units connected by a cabled bus network

Abstract

A system, such as a deflectometer (100), comprising a plurality of modular units (1; 206); a master controller (50); and a plurality of slave units including a first slave unit and a second slave unit; wherein each slave unit is interlinked with a corresponding modular unit (1; 206); and wherein a cabled bus network (22) connects the master controller (50) to the first slave unit and interconnects the first slave unit to a second slave unit. The master controller (50) automatically and dynamically keeps track of the physical position or at least the physical order of the slave units on the cabled network.

Description

[0001] A system with modular units connected by a cabled bus network

[0002] A system is configured for communication between a master controller and a plurality of slave units each interlinked with a modular unit. The master controller and the slave units enable automatic position determination of the modular units. In particular, the system may be a deflectometer, in which the modular units are geophone units.

[0003] INTRODUCTION

[0004] Geophones are often used for detecting such as quantifying and / or determining characteristics of, seismic waves propagating in the ground. One example is utilization of one or more geophones for sensing conditions at a ground surface, such as conditions of pavements such as road pavements. A falling weight deflectometer may be used. The deflectometer comprises a force inducing arrangement that may for example comprise a drop weight and a load plate. The load plate is configured to transfer an impact force / impulse force provided by means of the drop weight to a test surface. This causes seismic waves to propagate in the pavement, and one or more geophones of the falling weight deflectometer may register / sense the vertical deflection response of the ground surface, such as the pavement surface, caused by the propagating seismic wave. Such geophones comprise a geophone sensor arrangement. This sensor arrangement senses vibrations transferred from the test surface of the ground surface and provides a first sensor output based thereon. Often, this sensor arrangement comprises a coil and a magnet configured to move relative to each other when the geophone is subjected to the vertical deflection response, and the sensor arrangement thereby provides a sensor output reflecting the vertical deflection response. The information of this output can be analysed by a computer processing arrangement, and thereby conditions of the surface subjected to the seismic waves can be determ ined / estimated. This solution may often be used at pavements of, e.g., highways, local roads, airport pavements, harbour areas, railway tracks and / or the like. A geophone comprising such a sensor arrangement may also be referred to as an electromagnetic geophone. A geophone is conventionally mechanically complex and delicate. In some cases, the geophone may thus fail over time or gradually change mechanical behaviour over time, which may influence on the reliability of the information in the output from the geophone.

[0005] One or more geophones on the falling weight deflectometer are regularly or occasionally removed from their respective position on the falling weight deflectometer for service, e.g., including calibration, check or repair. In some examples, the one or more geophones are installed in random order following service or some, but not all geophones are removed, or some geophones are added to the configuration at the falling weight deflectometer.

[0006] PRIOR ART

[0007] WO 2023 / 209069 A1 (assigned to Dynatest A / S) discloses a falling weight deflectometer including a force inducing arrangement and a seismic sensor arrangement comprising one or more geophone units. Each of the geophone units comprises a housing and a geophone sensor arrangement arranged in the housing. In some examples, the deflectometer comprises a fault detection system configured to detect fault conditions in / of said one or more geophones. In one or more embodiments geophones are configured for wired communication with a geophone data collection arrangement, e.g., using a communication bus such as a data bus, such as a CAN (Controller Area Network) bus.

[0008] SUMMARY

[0009] Conventional CAN bus systems with a plurality of modular units, such as deflectometers with a plurality of geophone units, operate with fixed, pre-assigned and unique addresses. However, such systems are cumbersome to service and re-configure, e.g., since the modular units may be put back in random order following a service task. This is problematic since a control system and / or an associated data processing system will lose track of the physical order of the modular units. It is an object of the present disclosure to provide a system with improved flexibility and user-friendliness, e.g., in connection with tasks related to service or re-configuration of the system including the modular units, such as geophones arranged on a beam or frame of a deflectometer.

[0010] There is provided a system, comprising: a plurality of modular units including a first modular unit, a master controller, and a plurality of slave units; wherein a first slave unit is interlinked with the first modular unit; wherein a cabled bus network connects the master controller to the first slave unit and interconnects the first slave unit to a second slave unit at least via a first wire and a second wire; wherein the plurality of slave units are each configured to recurrently broadcast a current address value on the cabled bus network and to: take on a first state, wherein the slave unit takes a default address value; wherein the slave unit disengages downstream slave units; wherein the slave unit is enabled to be assigned an address value from the master controller; and wherein the slave unit, in response to having been assigned an address value, takes on a second state; and take on the second state, wherein the slave unit has an address value different from the default address; wherein the slave unit engages one or more downstream slave units; and wherein the slave unit enters the first state in response to a detection of being disengaged from an upstream unit; wherein the master controller communicates with the plurality of slave units to assign, in turn, an address value to a slave unit in response to detection of a default address value.

[0011] An advantage is that the slave units, interlinked with respective modular units and calibration data associated therewith, are serially assigned an address value, in turn, in accordance with the slave unit’s physical address on the cabled network. Here, the slave unit’s physical address corresponds with slave unit’s order seen from the master controller via the cabled bus network. The master controller is thereby able to process data from a slave unit’s assigned address in the correct order.

[0012] If, for instance, the system is a deflectometer, and the modular units are geophone units, this means that the master controller can process data corresponding to a propagation direction of a travelling wave caused by an impact induced by a force inducing arrangement at the deflectometer. This may be used in to obtain a representation of the order of the locations of the geophones along the geophone beam at the falling weight deflectometer (FWD). The cabled network extends along the geophone beam.

[0013] Generally, in respect of deflectometers, it is of utmost importance to obtain a representation of the order of the locations of the geophones along the geophone beam since pavement characteristics obtained by processing of data from the geophones are dependent on not only the measured deflection at each location but also the distance from the centre of load impact to the measurement locations.

[0014] Also, it is possible to use a bus topology network rather than, e.g., a star network topology, while enabling mapping between physical address and data received from a address.

[0015] In the case of a deflectometer, this means that a data packet containing data from a geophone sensor and transmitted by or via a slave unit and including a corresponding address assigned to the respective slave unit can be stored and / or processed in accordance with the physical address at which a geophone unit obtained the data. This plays an important role in terms of reduced complexity in connection with service tasks performed at the deflectometer and requiring detachment of the geophones.

[0016] A service task performed at the system may include that one or more slave units are disengaged, e.g., due to a lost connection, e.g., due to a disconnected cable, from an upstream unit. Thus, if the slave units are re-arranged, including disconnection, to a different order as seen from the master controller along the cabled bus network, the address of at least one of the slave units is reconfigured such that all slave units have an address in correspondence with the new, different order. Despite such a service task, the master controller is able to process data from a slave unit’s address in the correct order.

[0017] In some examples a slave unit is separate from the modular unit. Each slave unit may include a first connector for an upstream connection, a second connector for a downstream connection, and a third connector for interlinking the slave unit with a corresponding modular unit. The slave unit may thus have a T-configuration. Each pair of a modular unit and slave unit can thus be configured for a so-called multi-drop network structure.

[0018] Herein, an address is represented by a value. The address is included in a series of consecutive addresses (each address being unique). The series of consecutive addresses may include values that can be ordered in an ascending or descending order. The order may be in accordance with an implicit or explicit convention.

[0019] Herein, an address may be designated a ‘logical address’, however an address is assigned as described herein to reflect a physical order of the slave units (geophones).

[0020] Herein, a deflectometer, such as a falling weight deflectometer, ‘FWD’, may include a force inducing arrangement comprising a drop weight.

[0021] Herein, the slave units are not configured with Ethernet and not configured for TCP / IP communication. The master controller is at least not configured with Ethernet and not configured for TCP / IP communication for communication with the slave units.

[0022] Generally, the recurrent broadcast including a current address on the cabled bus network is also denoted a ‘heartbeat’.

[0023] In some aspects each of the slave units is configured to communicate with the master controller to obtain an address value in the first state.

[0024] In some examples, the master controller is configured with a list of serial addresses and assigns each of the slave units, one at a time, a serial address from the list of serial addresses. The addresses are also denoted addresses. In some examples, the master controller transmits a configuration message to the slave unit. The configuration message may include the assigned address and optionally additional values for configuration of the slave unit.

[0025] In some aspects each of the slave units is configured to communicate data packets to the master controller in the second state; wherein each data packet includes or is transmitted with an address value assigned to the slave unit at a time when the slave unit was in the first state.

[0026] In some examples, in the case of a deflectometer, the data packet is received from or is generated based on signals from a corresponding geophone controller. In some examples, the geophone controller is configured to generate compensated data based on calibration data stored in the corresponding memory.

[0027] Generally, at least in some examples, each slave unit is configured with a “listen- before-transmit” protocol to reduce the risk of several slave units transmitting on the cabled network at the same time.

[0028] In some aspects the master controller includes an address table, including at least a first address value and a corresponding time code value, and is configured to: recurrently listen for a message including the first address value; in accordance with a determination that the first address value is different from a default address value, update the address table at the first address value to include a current time code value; and in accordance with a determination that the first address value is a default address, send a configuration message including a unique address value to a slave unit having a default address value on the cabled bus network.

[0029] An advantage is that the master controller keeps itself updated and is able to react to detection of a default address. Each of the slave units recurrently broadcast their respective current address. Thus, by detection of a default address, the master controller is able to determine that a slave unit is (reconnected, e.g., at a random physical position or that slave units on the cabled bus network was (temporarily) disconnected. Any time a user reconnects a slave unit, e.g., at a random physical position, the master controller is able to (reestablish the order of connected slave units by starting addressing (of all slave units) anew and updating the address table accordingly.

[0030] In some aspects the master controller includes an address table, including at least a first address value and a corresponding time code value, and is configured to: recurrently, iterate through the address table; in accordance with a determination that a time code value does not meet a time criterion: display an error signal at a display of the master controller; broadcast a restart message on the cabled bus network to the slave units; and reset the address table including the respective time code values.

[0031] An advantage is an improved quality check since an operator of the system can be alerted of displaced modular units before or during use of the system while the master controller and slave units (re-)assigns themselves to reflect the actual order of the modular units. In some examples, each slave unit takes on the first state in response to receiving the restart message.

[0032] In some aspects a slave unit is configured to listen for a restart message and a configuration message; in accordance with receiving a restart message: set the address value at the slave unit to the default address value and disengage downstream slave units; and in accordance with receiving a configuration message: set the address value at the slave unit to an address value received form the master controller; and engage a downstream slave unit.

[0033] In some examples an error signal is displayed in response to receiving a restart message. In some examples the error signal is reset or an ok signal is displayed in response to having been assigned an address by a configuration message. A slave unit is thereby able to communicate its status to an operator of the deflectometer. In one example, slave units by default lights a red LED to show an error message. Following an update of the display, the slave unit lights a green LED and turns off the red LED. An operator can then wait until all slave units show a green LED before using the system.

[0034] In some aspects, each slave unit comprises a transceiver and a modular unit controller; wherein the slave unit includes an electronic circuit configured to selectively engage and disengage a downstream connection downstream of an upstream connection; wherein the transceiver is connected at the upstream connection; and wherein the modular unit controller is connected to the transceiver and the electronic circuit to selectively engage and disengage downstream slave units connected at the downstream connection.

[0035] An advantage is that a robust and low-cost electronic circuit for engaging or disengaging downstream slave units is provided. The electronic circuit may include a first switch in-line the first wire and a second switch in-line the second wire. The first switch and the second switch may include semiconductor switches. The switches may be operated to be ‘open’ at the same time or ‘closed’ at the same time.

[0036] In some examples, the modular unit controllers each includes an analogue-to- digital converter (ADC). If, for instance, the modular unit controller is a geophone controller, a geophone sensor may be connected to the analogue-to-digital converter, and the geophone sensor may output an analogue signal representative of a sensed deflection.

[0037] In some aspects each slave unit, in the second state, is configured to: listen to broadcast messages including corresponding address values; determine a largest address value among the corresponding address values; and electrically terminate the upstream connection and disengage the downstream connection in response to a determination that an address value assigned to the slave unit corresponds with the largest address value and that a threshold amount of time has passed without receiving any broadcast message.

[0038] This provides a solution to a problem of the cabled bus being left in a nonterminated, open state, which in some examples may prevent communication on the cabled bus. An advantage is that the last slave unit on the cabled network identifies itself as the last slave unit and electrically terminates the network to ensure continued communication. This is particularly useful in networks, such as CAN bus networks, requiring electrical termination at the last slave unit.

[0039] In some aspects, the master controller is configured to store a largest address value assigned to a slave unit and to transmit a terminate message addressed to the slave unit having the largest address value; and each slave unit, in the second state, is configured to: listen for a terminate message addressed to the slave unit; and electrically terminate the upstream connection and disengage the downstream connection in response to a determination that the terminate message is received.

[0040] This provides another solution to a problem of the cabled bus being left in a nonterminated, open state, which in some examples may prevent communication on the cabled bus. An advantage is that master controller addresses a terminate message to the one, last slave unit to electrically terminate the cabled network. This is particularly useful in networks, such as CAN bus networks, requiring electrical termination at the last slave unit.

[0041] In some aspects each slave unit and the master controller includes corresponding electronic circuits configured to establish a physical layer of a CAN bus.

[0042] An advantage is that the system can be configured with a low-cost communication bus while providing improved flexibility and user-friendliness, e.g., in connection with tasks related to service or re-configuration of the system including the modular units.

[0043] Obviously, the solutions presented in the present disclosure are not limited to being implemented using CAN bus networks. Other examples of cabled bus networks, with which this solution could be implemented include RS422, RS485, Ethernet, CAN FD, light guides, LIN, FlexRay, and 100BASE-T1.

[0044] In some aspects the plurality of slave units each comprises an electronic circuit including a first switch in-line the first wire, and / or a second switch in-line the second wire, and a third switch for shunting the first wire and the second wire via a terminator resistor, upstream of the first switch and the second switch.

[0045] In some examples the first switch and the second switch are operated to be concurrently ‘on’ while the third switch is concurrently ‘off’ or vice versa. Thus, termination of the cabled network and engaging / disengaging downstream slave units can be controlled via a single wire.

[0046] In some examples, in the second state at a slave unit: the first switch and the second switch are ‘on’ to engage a downstream port of the slave unit; and the third switch is ‘off’ to forgo shunting the first wire and the second wire via a terminator resistor. In the first state at the slave unit: the first switch and the second switch are ‘off’ to disengage the downstream port of the slave unit; and the third switch is ‘on’ to shunt the first wire and the second wire via the terminator resistor.

[0047] In some aspects, the system is a deflectometer, the modular units are geophone units, and the modular unit controller is a geophone controller.

[0048] Deflectometers with a plurality of geophone units arranged along a beam or frame of a deflectometer and connected by a cabled bus network are obvious examples of systems, in which the advantages of the present disclosure can really come into play. Other examples of such systems include light systems for concerts and the like, in which interconnected light projectors, which must be individually controlled, may be replaced or rearranged from time to time

[0049] In some aspects each geophone unit accommodates a geophone sensor and a geophone controller including a memory unit storing calibration data.

[0050] In that case, the geophone controller may include a slave unit. Each geophone unit can thus be configured for a so-called daisy-chained network, wherein each geophone unit includes first connector for an upstream connection and a second connector for a downstream connection.

[0051] There is also provided a method relating to a system including a plurality of modular units, a master controller, and a plurality of slave units including at least a first slave unit and a second slave unit each associated with a corresponding modular unit; wherein a cabled bus network connects the master controller to the first slave unit and interconnects the first slave unit to the second slave unit; the method comprising the steps of: from each of the first slave unit and the second slave unit recurrently broadcasting a current address value on the cabled bus network; at the first slave unit and the second slave unit, in turn: taking on a first state, wherein the slave unit takes a default address value; wherein the slave unit disengages downstream slave units; wherein the slave unit is enabled to be assigned an address value from the master controller; and wherein the slave unit, in response to having been assigned an address value, takes on a second state; and taking on the second state, wherein the slave unit has an address value different from the default address value; wherein the slave unit engages one or more downstream slave units; and wherein the slave unit enters the first state in response to a detection of being disengaged from an upstream unit; wherein the master controller communicates with the plurality of slave units to assign, in turn, an address value to a slave unit in response to detection of a default address value.

[0052] In some aspects of this method, the system is a deflectometer and the modular units are geophone units.

[0053] There is also provided a computer-readable storage medium storing one or more programs configured to be executed by processors at the slave units and the master controller of the above method, the one or more programs including instructions for performing the above method. BRIEF DESCRIPTION OF THE FIGURES

[0054] A more detailed description follows below with reference to the drawing, in which: fig. 1 shows a deflectometer; fig. 2 each shows a master controller and multiple slave units in a linear daisy chain network with in-line switches and illustrate a process for sequentially addressing the slave units one at a time along the cabled, linear bus network; fig. 3a shows a flowchart for operation of the master controller; fig. 3b shows a block diagram for a master controller; fig. 4a shows a flowchart for operation of a slave unit; and fig. 4b shows a block diagram for a slave unit.

[0055] DETAILED DESCRIPTION

[0056] Fig. 1 shows a deflectometer. The deflectometer 100 includes a force inducing arrangement 11 and a seismic sensor arrangement 21 .

[0057] The force inducing arrangement 11 has a drop weight 12, a lifting arrangement 23, and a load plate 14, wherein the load plate 14 is arranged to transfer an impact force from the drop weight 12 to a test surface 15. The lifting arrangement 23 is configured to lift the drop weight 12 to a height, such as a predetermined height, above the load plate 14. The lifting arrangement 23 may comprise an electrical or hydraulic motor. The drop weight 12 may be configured to directly or indirectly impact the load plate 14 so as to provide a force impulse to be transmitted to the test surface 15 when the drop weight 12 is released from said height. A displacement arrangement 40, e.g., including a linear actuator, is configured to lower the load plate on to the test surface before the drop weight 12 is released and to retract the load plate after one or more impulses are transmitted to the test surface by one or more impacts. The seismic sensor arrangement 21 comprises a plurality of geophone units 1. The geophone sensor arrangement is configured to sense vibrations transferred via the test surface 15 and to provide corresponding sensor outputs.

[0058] The geophone units 1 are arranged at a frame arrangement 16 of the deflectometer so as to detect vibrations from the test surface 15, e.g., at discretely arranged positions. A master controller 50 receives the information from the geophone units 1 by means of a cabled bus network 22. The frame arrangement 16 can be lowered towards the test surface 15 or retracted therefrom by a displacement drive 130. Thereby the geophone units 1 , arranged at the frame arrangement 16, are lowered towards the test surface 15 or retracted by displacement drive 130.

[0059] In some examples, the deflectometer 100 is arranged on a trailer configured for being towed by a vehicle. In this respect reference numeral 110 refers to a trailer coupling and 120 refers to a wheel shaft (wheels are omitted from the figure). In other embodiments, the deflectometer is integrated with or carried by a motorized vehicle.

[0060] During use, the deflectometer is moved to a desired location. Then the load plate 14 is moved to sit firmly on the test surface by means of the displacement arrangement 40. Then the falling weight 12 is moved to a desired height and is then dropped to strike / impact a force transferring arrangement that transfers the impact force to the load plate 14 and therefrom to the test surface 15. That induces propagation of a wave T 1 that travels along the surface of the test surface 15, and the vertical deflection response of the test surface 15 due to the impact is registered by the respective geophone units 1 and transmitted to the master controller 50 via the cabled bus network 22. In some examples, the master controller includes a microcontroller, a single board computer, or another type of computing device.

[0061] An example of a geophone unit comprises a geophone housing and a geophone sensor accommodated in the geophone housing. In some examples, a geophone sensor comprises a coil and a magnet configured to move relative to each other when the geophone is subjected to said vibrations. In some examples, a geophone unit is suspended from the frame arrangement 16, e.g., at an overhang portion at which the frame arrangement supports the geophone unit. The frame arrangement may include one or more holes, e.g., for a lock pin, recesses or fixtures for holding the geophones units at fixed positions, e.g., at equally distant positions or at other positions. In some examples, the geophones are freely placeable along the frame arrangement. Details of an example of a geophone and other examples are given in WO 2023 / 209069 A1 .

[0062] Each geophone unit accommodates, is integrated with or interlinked with a corresponding slave unit. Each slave unit is in turn connected via a cabled, linear bus network to enable communication with a master controller. Sequential addressing of the slave units, one-by-one, along the linear bus network enables determining the logical location of the geophone collecting location-specific data, transmitted from the geophone unit via a uniquely addressed slave unit. This assists in processing of the location-specific data in the correct order.

[0063] Figs. 2a to 2e each shows a master controller and multiple slave units in a linear daisy chain network with in-line switches and illustrate a process for sequentially addressing the slave units one at a time along the cabled, linear bus network.

[0064] The master controller 201 connects via the cabled bus network to slave units 202. The slave units 202 are interlinked with corresponding modular units, such as geophones G, 206. In some examples a slave unit is integrated with a modular unit, e.g., accommodated in a geophone housing. In other examples, a slave unit is separate from but interconnectable with a modular unit. For the sake of simplicity, the modular units G, 206 are omitted from figures 2b through 2e.

[0065] Each of the slave units 202 has at least a first state, indicated by numeral one in square brackets [1], and a second state indicated by numeral two in square brackets [2], Each of the slave units are connected to a cabled linear bus network extending from the master controller 201 via a most proximal, nearest, slave unit to a most distant, last, slave unit on the linear bus network. For the sake of illustration switches 210 are shown downstream of each slave unit 202 although a switch is typically integrated with the nearest upstream slave unit. The switches are inline, in series, with the linear cabled bus network to enable that slave unit can disengage downstream slave units by opening the inline switch and enable that the slave unit can engage downstream slave units by closing the inline switch.

[0066] Each slave unit 202 is configured with a default address. A slave unit may take this address during a power-on phase, in response to a message from the master controller, in response to a manual press of a reset button on in another way. Each slave unit can be configured with a unique address, different from the default address, assigned by the master controller. The slave units are assigned a unique address one-by-one, in turn, and in order from the nearest slave unit to the last slave unit. In any event, the plurality of slave units are each configured to recurrently broadcast their respective current address on the cabled bus network. This broadcast is performed at times when the slave unit is powered on and is also denoted a ‘heartbeat’ since it signals that the slave unit is powered on.

[0067] Fig. 2a shows that all slave units 202 takes on the first state

[0001] , In the first state, the slave units each takes the same default address. By opening its downstream switch, each slave unit disengages downstream slave units. As can be seen, only the one slave unit nearest to the master controller is engaged since the master controller 201 does not disengage slave units (the cabled connection between the master controller and the nearest slave unit is maintained).

[0068] Fig. 2b shows that the nearest slave unit broadcasts its current address in an address message, Adr, 203, which is a default address at this stage. The nearest slave unit is still in the first state

[0001] and is enabled to be assigned an address from the master controller. Since the master controller engages any downstream slave unit and since each slave unit disengages downstream slave units only the nearest slave unit, nearest to the master controller can be assigned an address different from the default address at this stage. Each slave unit will recurrently transmit the default address, however only addresses from engaged slave units, including the nearest slave unit, can reach the master controller.

[0069] Fig. 2c shows that the nearest slave unit receives a configuration message CF, 204, containing an assigned unique address, from the master controller. The nearest slave unit takes this assigned unique address and takes on the second state [2],

[0070] Fig. 2d shows that nearest slave unit takes on the second state [2] in response to have been assigned an address different from the default address and engages one or more downstream slave units as can be seen by the closed switch downstream of the nearest slave unit.

[0071] Fig. 2e shows that the second nearest slave unit is engaged by the closed switch of the nearest, upstream slave unit and is thereby enabled to broadcast its (default) address in the address message Adr, 205.

[0072] The process for sequentially addressing the slave units one at a time along the cabled, linear bus network continues in the same way until all slave units 202 have obtained a unique address, all different from the default address. As long as the master controller 201 detects a default address, the master controller 201 communicates with the one or more slave units to assign an address to the correspond slave unit.

[0073] Each slave unit 202 is configured to take on the first state

[0001] in response to a detection of being disengaged from an upstream unit. A slave unit may detect being disengaged from an upstream unit in response to an upstream, inline switch 210 being opened or in response to a disconnection from the cabled network, e.g., in response to being removed during a service task.

[0074] In some examples, the master controller 201 is configured to await a user input at a user interface (not shown) before initiating addressing of the slave units. In some examples, the master controller 201 is configured to initiate addressing anew in response to detecting a fail to receive an assigned unique address, within a range of unique, assigned addresses, within a time window.

[0075] The master controller 201 is configured to keep track of assigned addresses and the order in which they were assigned such that, at a time when all slave units on the linear bus network have been assigned an address, the master controller has obtained a list of serial addresses and the order in which they were assigned. The master controller has thereby obtained a representation of the order of the slave units on the linear bus.

[0076] In the case of a deflectometer, for instance, it is thereby possible to convert the order of the slave units to a physical position along the beam structure onto which the geophones are mounted at the falling weight deflectometer (FWD). In some examples, the deflectometer is configured to receive the geophones at fixed positions only. In such examples, a conversion table at the master controller may include corresponding values of the address assigned to a slave unit (and thus the geophone) and a physical position of the geophone corresponding to the address. As an example, the conversion table may include absolute physical position values, e.g., that the first address corresponds with a horizontal distance of 50 centimetres from the falling weight, that the second address corresponds with a horizontal distance of 100 centimetres from the falling weight etc. As another example, the table may include relative physical position values representing mutual distances at least between deflectometers. The conversion table may be configured with the physical positions during manufacture of the deflectometer and / or during a user’s configuration of the master controller.

[0077] In other examples, the deflectometer is configured to receive the geophones at free positions along the frame. In such examples, a conversion table at the master controller includes corresponding values of the address assigned to a slave unit (and thus the geophone) and a physical position of the geophone corresponding to the address. However, the master controller may be configured to receive values entered by user who has acquired absolute or relative measurements of positions of the geophones. The received values are stored in the conversion table. The user may enter the values at a user interface of the master controller or load the values into the master controller via a remote computer via a wired or wireless connection or network. In some examples the conversion table is not stored in the master controller but is rather stored at a remote computer at which processing of data from the geophones is performed.

[0078] It is generally known in the field of deflectometers and processing related thereto that it is of utmost importance to know the location of all geophones along the beam since the calculation of pavement characteristics are dependent on not only the measured deflection at each location but also the distance from the centre of load impact to the measurement locations.

[0079] Fig. 3a shows a flowchart for operation of the master controller. The master controller is initiated in step 301 and concurrently executes a first process 310 and a second process 320. A third process 330 processes, e.g., including sorting or organizing, data packets sent from the slave units in accordance with an address included in or transmitted with the data packet and in accordance with order of the addresses in the first table.

[0080] The first process 310 listens for messages, each including a corresponding address, from the slaves at step 311. In response to a detection of a message, the first process at step 312 either determines that the message fails to include a default address (N) or determines that the message includes a default address (Y). In accordance with a determination that the message fails to include a default address (N), i.e., that the message includes a unique address previously assigned to a slave unit, the first table 302 is updated in step 314 to reflect that the corresponding slave responded with a message at a current time, e.g., by updating a timestamp. Alternatively, in accordance with a determination that the message includes a default address (Y), the first process assigns a unique serial address to the slave unit in step 313 by transmitting an address assignment message. Due to the operation of the slave units, operating the inline switches, it is expected that the master controller assigns an address to only one slave unit at a time.

[0081] The second process 320 monitors whether messages from all slave units are recurrently received and is able to initiate dynamic addressing anew or forgo initiate addressing anew. At step 321 the second process waits for a period of time, then at step 322 it reads through the first table 302, and determines in step 323 either that any one of the slave units failed to respond within a threshold amount of time (Y) or that all slave units did not fail to respond within a threshold amount of time (N). In some examples, the determination is based on the timestamp or count mentioned above. In accordance with a determination that that all the slave units did not fail to respond within a threshold amount of time (N), the second process reverts to step 321 to wait for a period of time. In accordance with a determination that any one of the slave units failed to respond within a threshold amount of time (Y), the second process displays a message accordingly, e.g., an alert type of message, in step 324 and sends a broadcast message to the slave units instructing the slave units to perform a restart procedure by sending a restart message (to initiate addressing anew) in step 325 and to reset the first table in step 326.

[0082] Fig. 3b shows a block diagram for a master controller. The master controller may include an electronic device 340, e.g., including a single-board computer, with a microcontroller 342, a transceiver 344 interfacing via a connector to the cabled bus network, and a LAN / WAN interface interfacing (via a connector or via an antenna) to a wired or wireless LAN / WAN network, e.g., the Internet. The user interface may include a combination of a display and one or more input devices, e.g., a keyboard and / or a touch-sensitive display. The electronic device 340 is configured to execute the processes described in connection with fig. 3a.

[0083] Fig. 4a shows a flowchart for operation of the slave units. The slave unit is powered up in step 401 and proceeds to step 402 to take the default address and disengage downstream slave units. Concurrently, the slave unit executes a first process 410 and a second process 420.

[0084] The first process 410 waits for a period of time in step 411 ; proceeds to read in step 412 its address, which may include a default address or an address assigned by the master controller, from a memory at the slave unit; and broadcast a message with its address in step 413. The first process thus recurrently announces itself to the master controller. Generally, a slave unit and the master controller apply a listen-before-talking principle to avoid interfering with other units already transmitting on the network.

[0085] The second process 420 listens a message on the cabled network in step 421 . In accordance with a determination that the message is a restart message, the second process proceeds to step 422. In accordance with a determination that the message is an address assignment message, the second process proceeds to step 425.

[0086] In step 422 the slave unit sets its address to the default address, proceeds to step 423 to disengage downstream slave units, and proceeds to step 424 to display an alert type message on a user interface of the slave unit (not shown). Such a user interface may include one or more LED light sources and optionally one or more buttons. The alert type message may be shown by turning a red LED on.

[0087] In step 425 the slave unit sets its address to an address received in the address assignment message, proceeds to engage downstream slave units in step 426 and displays an okay type message on the user interface in step 427. The okay type message may be shown by turning a green LED on.

[0088] Fig. 4b shows a block diagram for a slave unit. In this example, the slave unit 430 is interconnectable to a modular unit in the form of a geophone unit 435 via a wired connection and the slave unit is configured to receive analogue signals from the geophone sensor 435. Here the cabled bus network is shown to include a first wire W1 and a second wire W2. The slave unit 430 includes a first switch S1 in-line the first wire W1 , and a second switch S2 in-line the second wire W2, and a third switch S3 for shunting the first wire W1 and the second wire W2 via a terminator resistor R1 , upstream of the first switch and the second switch. Although the wires are interrupted by the switches, the wires are referred to as W1 and W2 upstream and downstream of the switches. The terminator resistor is configured to provide adequate ohmic termination of the cabled network as it is known in the art. The microcontroller 432 is configured to control the switches.

[0089] In accordance with the first state [1] of the slave unit, the microcontroller sets the first switch S1 and the second switch S2 ‘off’ to disengage the downstream port of the slave unit; and the third switch is set ‘on’ to shunt the first wire and the second wire via the terminator resistor.

[0090] In accordance with the second state [2] of the slave unit, the microcontroller sets the first switch S1 and the second switch S2 ‘on’ to engage a downstream port of the slave unit; and the third switch is set ‘off’ to forgo shunting the first wire and the second wire via a terminator resistor.

[0091] The transceiver 431 is connected at the upstream side of the switches S1 and S2. The microcontroller 432, e.g., denoted a geophone controller, is connected to the transceiver and the electronic circuit, comprising switches S1 , S2, S3 and inverter 11 , to selectively engage and disengage downstream slave units connected at the downstream side of the switches S1 and S2. The inverter 11 controls the switch S3 in opposite phase to the switches S1 and S2.

[0092] In some examples, the cabled network and the slave units are configured for a daisy-chained structure, wherein each slave unit includes and upstream connector and a downstream connector.

[0093] In other examples, the modular unit may include an analogue-to-digital converter and a microcontroller for communicating with the microcontroller 432 in the slave unit.

[0094] Optionally, the modular unit, such as the geophone sensor 435 in the case of a deflectometer, may include a memory for storing calibration data corresponding with the modular unit.

[0095] In some examples, the cabled network and the slave units are configured for a multi-drop structure, wherein each slave unit is included in a T-type element with an upstream connector, a downstream connector and a drop connector, wherein the drop connector enables interconnection with a modular unit, e.g., for analogue or digital communication.

[0096] Generally, it is understood that the falling weight deflectometer in embodiments of the present disclosure may be used for non-destructive testing (NDT) of ground surfaces such as for pavement structural evaluation and health monitoring. The falling weight deflectometer may be used for evaluating physical properties / condition of surfaces such as ground surfaces, such as pavement surfaces, for example road surfaces. A road surface may comprise a pavement of, e.g., highways, local roads, airport pavements, harbour areas, railway tracks and / or the like. The data acquired from the falling weight deflectometer may originate directly or indirectly from geophone(s) of the deflectometer. This data may be used for estimating pavement structural capacity. Depending on the falling weight deflectometer design it may, e.g., be placed at / part of a towable trailer or it may be built into a self-propelled vehicle.

Claims

CLAIMS1. A system, comprising: a plurality of modular units (1 ; 206) including a first modular unit, a master controller (201 ), and a plurality of slave units (202); wherein a first slave unit is interlinked with the first modular unit; wherein a cabled bus network connects the master controller to the first slave unit and interconnects the first slave unit to a second slave unit at least via a first wire and a second wire; wherein the plurality of slave units (202) are each configured to recurrently broadcast a current address value on the cabled bus network and to: take on a first state, wherein the slave unit takes a default address value; wherein the slave unit disengages downstream slave units; wherein the slave unit is enabled to be assigned an address value from the master controller; and wherein the slave unit, in response to having been assigned an address value, takes on a second state; and take on the second state, wherein the slave unit has an address value different from the default address; wherein the slave unit engages one or more downstream slave units; and wherein the slave unit enters the first state in response to a detection of being disengaged from an upstream unit; wherein the master controller communicates with the plurality of slave units to assign, in turn, an address value to a slave unit in response to detection of a default address value.

2. The system according to claim 1 , wherein each of the slave units is configured to communicate with the master controller to obtain an address value in the first state.

3. The system according to claim 1 or 2, wherein each of the slave units is configured to communicate data packets to the master controller in the second state; wherein each data packet includes or is transmitted with an address value assigned to the slave unit at a time when the slave unit was in the first state.

4. The system according to any of the preceding claims, wherein the master controller includes an address table, including at least a first address value and a corresponding time code value, and is configured to: recurrently listen for a message including the first address value; in accordance with a determination that the first address value is different from a default address value, update the address table at the first address value to include a current time code value; and in accordance with a determination that the first address value is a default address, send a configuration message including a unique address value to a slave unit having a default address value on the cabled bus network.

5. The system according to any of the preceding claims, wherein the master controller includes an address table, including at least a first address value and a corresponding time code value, and is configured to: recurrently, iterate through the address table; in accordance with a determination that a time code value does not meet a time criterion: display an error signal at a display of the master controller; broadcast a restart message on the cabled bus network to the slave units; and reset the address table including the respective time code values.

6. The system according to any of the preceding claims, wherein a slave unit is configured to listen for a restart message and a configuration message; in accordance with receiving a restart message: set the address value at the slave unit to the default address value and disengage downstream slave units; and in accordance with receiving a configuration message: set the address value at the slave unit to an address value received form the master controller; and engage a downstream slave unit.

7. The system according to any of the preceding claims, wherein each slave unit comprises a transceiver (431 ) and a modular unit controller (432);wherein the slave unit (430) includes an electronic circuit configured to selectively engage and disengage a downstream connection downstream of an upstream connection; wherein the transceiver (432) is connected at the upstream connection; and wherein the modular unit controller (432) is connected to the transceiver and the electronic circuit to selectively engage and disengage downstream slave units connected at the downstream connection.

8. The system according to any of the preceding claims, wherein each slave unit, in the second state, is configured to: listen to broadcast messages including corresponding address values; determine a largest address value among the corresponding address values; and electrically terminate the upstream connection and disengage the downstream connection in response to a determination that an address value assigned to the slave unit corresponds with the largest address value and that a threshold amount of time has passed without receiving any broadcast message.

9. The system according to any of the preceding claims, wherein the master controller is configured to store a largest address value assigned to a slave unit and to transmit a terminate message addressed to the slave unit having the largest address value; wherein each slave unit, in the second state, is configured to: listen for a terminate message addressed to the slave unit; and electrically terminate the upstream connection and disengage the downstream connection in response to a determination that the terminate message is received.

10. The system according to any of the preceding claims, wherein each slave unit and the master controller includes corresponding electronic circuits configured to establish a physical layer of a CAN bus.11 . The system according to any of the preceding claims, wherein the plurality of slave units each comprises an electronic circuit including a first switch in-line the first wire, and / or a second switch in-line the second wire, and a third switch for shunting the first wire and the second wire via a terminator resistor, upstream of the first switch and the second switch.

12. The system according to any of the preceding claims, wherein the system is a deflectometer, the modular units are geophone units, and the modular unit controller (432) is a geophone controller.

13. The system according to claim 12, wherein each geophone unit accommodates a geophone sensor and a geophone controller including a memory unit storing calibration data.

14. A method relating to a system including a plurality of modular units, a master controller, and a plurality of slave units including at least a first slave unit and a second slave unit each associated with a corresponding modular unit; wherein a cabled bus network connects the master controller to the first slave unit and interconnects the first slave unit to the second slave unit; the method comprising the steps of: from each of the first slave unit and the second slave unit recurrently broadcasting a current address value on the cabled bus network; at the first slave unit and the second slave unit, in turn: taking on a first state, wherein the slave unit takes a default address value; wherein the slave unit disengages downstream slave units; wherein the slave unit is enabled to be assigned an address value from the master controller; and wherein the slave unit, in response to having been assigned an address value, takes on a second state; and taking on the second state, wherein the slave unit has an address value different from the default address value; wherein the slave unit engages one or more downstream slave units; and wherein the slave unit enters the first state in response to a detection of being disengaged from an upstream unit;wherein the master controller communicates with the plurality of slave units to assign, in turn, an address value to a slave unit in response to detection of a default address value.

15. The method according to claim 14, wherein the system is a deflectometer and the modular units are geophone units.

16. A computer-readable storage medium storing one or more programs configured to be executed by processors at the slave units and the master controller of the method of claim 14 or 15, the one or more programs including instructions for performing the method of claim 14 or 15.

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