WO2022036457A1

WO2022036457A1 - Wireless sensor unit

Info

Publication number: WO2022036457A1
Application number: PCT/CA2021/051155
Authority: WO
Inventors: Anthony BASTIAANSEN; Thai Bich TRAN
Original assignee: Boss Packaging Inc.
Priority date: 2020-08-20
Filing date: 2021-08-20
Publication date: 2022-02-24

Abstract

A wireless sensor unit, having a processor, dual accelerometers with non-overlapping resonant frequencies, a temperature measurement device, a power source, and a wireless transmitter, which are mounted within a housing and configured for mounting on an object to be measured. The at least two accelerometers may be 3-axis micro electro-mechanical system (MEMS) accelerometers. The wireless sensor units may be used in a sensor unit network with one or more gateway units, each having a processor, a power source, and a wireless transceiver.

Description

WIRELESS SENSOR UNIT

Field of the Invention

[0001] The present invention relates to vibration and temperature sensors and, in particular, to vibration and temperature sensors used in a wireless network of sensor units.

Background

[0002] Wireless sensors are used in a growing range of applications to measure parameters such as vibration, movement, and temperature of objects and equipment and transmit data wirelessly to a remote monitoring centre. They are available in a wide variety of configurations and sizes and generally contain an accelerometer for measuring vibration and a wireless transmitter to relay the measurements for processing.

[0003] These types of wireless sensors may be used to gather valuable information in a wide range of applications. For example, vibration and temperature monitoring of mechanical equipment can provide valuable information on the operating condition of the equipment and provide early warning before a critical failure of the equipment occurs. This facilitates better maintenance planning and can reduce unscheduled downtime of the equipment.

[0004] When the accelerometers typically installed in wireless sensors are used in high vibration applications, for example, on locomotives or railcars, the significant background vibrations present in the operating environment can cause high signal “noise” in the accelerometer measurements. This can lead to inaccurate measurement of acceleration and reduce the reliability of the information produced by the wireless sensors. [0005] Accordingly, there is a need for a wireless sensor that is able to reduce the signal “noise” caused in high vibration operating environments to produce more accurate and reliable acceleration measurements.

Summary of the Invention

[0006] A wireless sensor unit, according to the present invention, has a processor, at least two accelerometers with non-overlapping resonant frequencies, a temperature measurement device, a power source, and a wireless transmitter, which are mounted within a housing and configured for mounting on an object to be measured.

[0007] In another embodiment, the at least two accelerometers are 3-axis micro electromechanical system (MEMS) accelerometers.

[0008] In another embodiment, at least one of the two or more accelerometers is a low-power accelerometer.

[0009] In another embodiment, the temperature measurement device is a resistance temperature detector (RTD) wire extending from the housing inside a hollow bolt.

[0010] In another embodiment, a plurality of the wireless sensor units may be used in a sensor unit network with one or more gateway units, each having a processor, a power source, and a wireless transceiver.

[0011] In another embodiment, the power consumption of the wireless sensor units may be minimized by operating a low-power accelerometer continuously while one or more other electronic components of the wireless sensor unit operate in a low power setting to reduce power consumption. The low-power accelerometer may detect an acceleration signal above a first threshold and the wireless sensor unit may switch the one or more other electronic components to operate in a normal power setting.

[0012] In another embodiment, the wireless sensor unit may switch the one or more other electronic components back to a low power setting after detecting acceleration below a second threshold for a period of time.

Brief Description of the Drawings

[0013] In order that the invention may be more clearly understood, a preferred embodiment thereof will now be described in detail by way of example, with reference to the accompanying drawings, in which:

[0014] Figure 1 is a perspective view of the wireless sensor unit, according to the present invention.

[0015] Figure 2 is a side view of the wireless sensor unit.

[0016] Figure 3 is a top view of the wireless sensor unit.

[0017] Figure 4 is an exploded perspective view of the wireless sensor unit.

[0018] Figure 5 is a perspective view of the wireless sensor unit, with a portion of the housing removed to show the interior.

[0019] Figure 6 is a side view of the wireless sensor unit, as shown in Fig. 5.

[0020] Figure 7 is a side sectional view of the wireless sensor unit, along the lines A- A.

[0021] Figure 8 is another perspective view of the wireless sensor unit, as shown in Fig. 5. [0022] Figure 9 is an exploded perspective view of the wireless sensor unit, as shown in Fig. 8.

Description of the Preferred Embodiment

[0023] The wireless sensor unit, according to the present invention, has a processor, at least two accelerometers with non-overlapping resonant frequencies, a temperature measurement device, a power source, and a wireless transmitter, which are mounted within a housing and configured for mounting on an object or piece of equipment to be measured or monitored. The wireless sensor units are connected to a gateway unit that collects, stores, and transmits data from a network of wireless sensor units. One or more gateway units and networks of wireless sensor units may be installed on a piece of equipment, such as a locomotive and associated railcars or railroad tracks, to monitor, store, and transmit data on the condition of the equipment in real time. This data may include temperature, vibration, acceleration, velocity, and tilt angle information that can be used to detect or predict emergency conditions, such as a train derailment, or improperly functioning equipment that may require maintenance in order to avoid a failure.

[0024] As shown in Figures 4, 5, and 7, the processor 1 of the wireless sensor unit, or sensor, controls the electronic components of the sensor and is mounted inside the housing 2. Preferably, the processor 1 is a single-chip microcontroller unit (MCU) installed on a printed circuit board (PCB) with the other electronic components of the sensor. Alternatively, other types of processors may be used, such as a CPU using additional external peripheral circuits and IC. The PCB is mounted within the housing 2 by way of a sealing adhesive, or potting material, to protect the PCB from damage, while transmitting vibration and acceleration forces to the accelerometers on the PCB for accurate measurement. Preferably, the PCB fits snugly into a cavity within the housing 2 dimensioned to fit the PCB and associated electronic components of the sensor and is held in place by an electronics grade solid silicone elastomer potting material.

[0025] The sensor has two types of measurement devices, namely, an accelerometer and a temperature measurement device. The accelerometer measures static acceleration (i.e. gravity) and dynamic acceleration (i.e. motion and vibration). At least two accelerometers are used, having non-overlapping resonant frequencies. Preferably, two 3-axis micro electro-mechanical system (MEMS) accelerometers are used, but other types of accelerometers may be used and more than 2 accelerometers may be used, provided at least two of the accelerometers have nonoverlapping resonant frequencies.

[0026] A MEMS accelerometer measures the deflection of a mechanical beam to infer acceleration. The beam will have a resonant frequency defined by the mechanical structure of the sensing element. As the input acceleration stimulation frequency approaches the resonant frequency of the sensing element, constructive interference causes the deflection on the beam to exceed the input stimulus and therefore the inferred acceleration is amplified. This results in "noise" measurements from the accelerometer, which do not accurately reflect the motion of the accelerometer. This can reduce the reliability of the acceleration measurements and significantly affect the accuracy of any calculated values, such as velocity or tilt angle, based on a series of acceleration measurements.

[0027] The use of at least two accelerometers with non-overlapping resonant frequencies addresses this limitation of single accelerometer sensors by taking measurements from each accelerometer and comparing them to filter out false readings, or "noise", caused by vibration at the resonant frequency of one of the dual accelerometers. By eliminating "noise" in this way, the accuracy and reliability of acceleration measurements can be improved. As a result, the accuracy and reliability of any calculated values, based thereon, are also improved.

[0028] The sensor may also provide temperature measurement by way of a temperature probe, or other suitable temperature measurement device, which provides temperature readings to the processor. Preferably, a resistance temperature detector (RTD) wire 3 is used to measure temperature, but other types of temperature measurement devices may be used, such as thermocouples, thermistors, or infrared sensors. As shown in Figures 6-9, the RTD wire 3 is attached to the PCB and extends from the cavity in the housing 2, inside a hollow bolt 4 to protect the RTD wire 3 from the surrounding environment.

[0029] The power source 5 for the electronic components of the sensor is a battery, which is attached over the cavity in the housing 2, as shown in Figures 1-4. Alternatively, other power sources may be used, such as a solar cell, harvested energy, or a wired power supply.

[0030] The sensors are installed as a network of connected units, which communicate with a gateway unit by way of a wireless transmitter, preferably a wireless radio. The wireless radio is an electronic component installed on the PCB, mounted within the housing 2. Preferably, a 2.4 GHz or a 915 MHz transmitter is used, but other types of one-way wireless radios or two-way wireless transceivers may be used.

[0031] In order to facilitate easy mounting of the sensor on the object to be measured or monitored, the sensors are configured with a mount suitable for the intended application (i.e. the particular equipment). Where the object is magnetic, a magnetic mount 6 may be used. Where existing mounting structures are conveniently located on the object, such as threaded apertures, a complementary mechanical mount may be provided on the outside of the housing, such as a threaded bolt or quarter-turn mount. Preferably, as shown in Figures 1, 2, and 4 the sensor has a magnetic mount 6 for mounting on metallic equipment, such as elements of the frame, chassis, or other stationary components of the locomotive or railcars of a train.

[0032] The sensor is intended to operate in a variety of challenging environmental conditions, including high temperatures. Accordingly, the housing 2 is constructed of a rugged material, such as a high-performance polyamide resin, which also provides thermal insulation for the electronic components of the sensor, such as the processor 1, dual accelerometers, and wireless transmitter mounted within the housing 2. In applications where high temperature is not a significant concern, the housing may be constructed fully or partially of metal. The sensor may also be required to operate in the presence of dust, moisture, or other contaminants in the air. Accordingly, the housing 2 is preferably sealed to prevent infiltration of any contaminants that could interfere with the electronic components of the sensor.

[0033] As discussed above, the dual accelerometers measure vibration and movement (i.e. acceleration) of the sensor. The sensor can also use the acceleration measurements to calculate the velocity and displacement of the sensor. Since the MEMS accelerometers that make up the dual accelerometers in the sensor are 3-axis accelerometers, the sensor is able to constantly measure both the magnitude and direction of the acceleration forces applied to the sensor. These measurements of acceleration forces are used to continuously update the calculated velocity and displacement of the sensor in three dimensions.

[0034] For example, when the sensors are mounted on the locomotive and railcars of a train, which is accelerating from a stop, the sensors will begin with an initial velocity of zero. The dual accelerometers of the sensors will detect the acceleration forces as the locomotive accelerates and will update the calculated velocity. As the train reaches its desired speed of travel and the operator reduces the acceleration to maintain a constant speed, the sensors will continue to measure the changing acceleration and update the calculated velocity. Once the train is moving at a constant speed of travel, the sensors will detect zero, or substantially zero, acceleration and the calculated velocity should match the actual speed of the train along the track. If the train operator engages the brakes or the train encounters a turn in the track, the sensors will detect the acceleration forces and update the calculated velocity accordingly.

[0035] The sensor may also be configured to calculate the angle of tilt, using the known absolute orientation and magnitude of the Earth’s gravitational field and comparing it to a detected orientation of the static acceleration of the sensor to calculate the sensor’s orientation (or angle of tilt) relative to that of the Earth.

[0036] As described above, a network of sensors may be installed on a piece of equipment, each gathering information at a different location on the equipment. A gateway unit is mounted on or near the equipment and functions as a communications hub for a plurality of sensors. The gateway unit has a processor, a power source, and a wireless transceiver, which are mounted within a housing. The gateway unit will typically be larger to permit a larger battery, or other power source, a more sophisticated processor, and a longer-range wireless transceiver. Optionally, the gateway unit may be connected to an external power source, with or without a battery backup, since the positioning of the gateway unit is not critical. The gateway unit also, preferably, has a data storage device, such as a hard drive, to store the data transmitted to it by each sensor in the network of connected sensors.

[0037] Optionally, in order to reduce the cost and power requirements of the sensors, the sensors can operate only to measure acceleration and/or temperature and transmit those measurements to the gateway unit. All of the calculated values, such as acceleration and tilt, may be calculated by the processor of the gateway unit, thereby reducing the processing capacity and power requirements of each sensor.

[0038] In some embodiments, the sensor may have a low-power accelerometer that operates continuously, while the other electronic components of the sensor are powered off or are operating in a low power consumption setting. The low-power accelerometer is able to detect acceleration events at a specified threshold and send a signal to the processor to "wake up" the other electronic components of the sensor and switch them to operate in a normal power setting. The dual accelerometers and wireless transmitter can then begin measuring the acceleration, with higher accuracy than the low-power accelerometer, and transmitting the measurements to the gateway unit. In order to minimize power consumption, the sensor may be powered off or return to a low power consumption setting again, for example, after acceleration measurements have dropped below a specified threshold for a specified period of time. This prolongs the life of the sensor's battery, requiring less frequent maintenance or replacement of the sensors. Reduced maintenance requirements are particularly beneficial for sensors placed on remote equipment or on equipment such as railcars, which may travel long distances before returning to a maintenance depot or other convenient location for maintenance or replacement of the sensors on the railcar.

[0039] The present invention has been described and illustrated with reference to an exemplary embodiment, however, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention as set out in the following claims. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed herein.

Claims

What is claimed is:

1. A wireless sensor unit, comprising: a processor, at least two accelerometers having nonoverlapping resonant frequencies, a temperature measurement device, a power source, and a wireless transmitter, which are mounted within a housing and configured for mounting on an object to be measured.

2. The wireless sensor unit of claim 1 , wherein the at least two accelerometers measure static acceleration and dynamic acceleration.

3. The wireless sensor unit of claim 2, wherein the at least two accelerometers are 3-axis micro electro-mechanical system accelerometers.

4. The wireless sensor unit of claim 2, wherein at least one of the at least two accelerometers is a low-power accelerometer.

5. The wireless sensor unit of claim 3, wherein the wireless transmitter is a wireless radio.

6. The wireless sensor unit of claim 3, wherein the wireless transmitter is a wireless transceiver.

7. The wireless sensor unit of claim 3, wherein the temperature measurement device is selected from the group consisting of: resistance temperature detector wires, thermocouples, thermistors, and infrared sensors.

8. The wireless sensor unit of claim 7, wherein the temperature measurement device is a resistance temperature detector wire extending from the housing inside a hollow bolt.

9. The wireless sensor unit of claim 3, wherein the power source is selected from the group consisting of: a battery, a solar cell, a harvested energy system, and a wired power supply.

10. The wireless sensor unit of claim 9, wherein the power source is a battery.

11. The wireless sensor unit of claim 3, wherein the wireless sensor unit has a magnetic mount for mounting to the object.

12. The wireless sensor unit of claim 3, wherein the wireless sensor unit has a mechanical mount for mounting to complementary mounting structures on the object.

13. A sensor unit network, comprising: a plurality of wireless sensor units, wherein each wireless sensor unit comprises: a processor, at least two accelerometers having non-overlapping resonant frequencies, a temperature measurement device, a power source, and a wireless transmitter, which are mounted within a housing and configured for mounting on an object to be measured; and one or more gateway units, wherein each gateway unit comprises: a processor, a power source, and a wireless transceiver.

14. The sensor unit network of claim 13, wherein the one or more gateway units comprise a data storage device.

15. The sensor network of claim 14, wherein the at least two accelerometers are 3-axis micro electro-mechanical system accelerometers and measure static acceleration and dynamic acceleration.

16. The sensor network of claim 15, wherein at least one of the at least two accelerometers is a low-power accelerometer.

17. A method of minimizing power consumption of a wireless sensor unit, wherein the wireless sensor unit comprises a processor, at least two accelerometers having non-overlapping resonant frequencies, a temperature measurement device, a power source, and a wireless transmitter, which are mounted within a housing and configured for mounting on an object to be measured, and wherein at least one of the at least two accelerometers is a low-power accelerometer, comprising the steps of: operating the low-power accelerometer continuously while one or more other electronic components of the wireless sensor unit operate in a low power setting to reduce power consumption; detecting an acceleration signal above a first threshold with the low-power accelerometer; and switching the one or more other electronic components to operate in a normal power setting.

18. The method of claim 17, further comprising the steps of: detecting acceleration below a second threshold for a period of time; and switching the one or more other electronic components to operate in a low power setting.

19. The method of claim 18, wherein the at least two accelerometers are 3-axis micro electromechanical system accelerometers and measure static acceleration and dynamic acceleration.

20. A method of determining an angle of tilt of a wireless sensor unit, wherein the wireless sensor unit comprises a processor, at least two accelerometers having non-overlapping resonant frequencies, a temperature measurement device, a power source, and a wireless transmitter, which are mounted within a housing and configured for mounting on an object to be measured, comprising the steps of: detecting an orientation of a static acceleration force on the wireless sensor unit; and comparing the detected orientation to a known orientation of the Earth’s gravitational field to calculate the angle of tilt of the wireless sensor unit.