CN101902832A - Low-power wireless sensor network node device for continuous vibration monitoring - Google Patents

Abstract

The present invention proposes a low-power wireless sensor network node device that can continuously monitor vibration, and a power module, a communication module and a sensor module are all connected to a microprocessor; the structure of the power module is: a solar battery and a lithium battery The output terminals are respectively connected to 3 input terminals of the first analog switch, and the output terminals of the first analog switch are connected to the power interface of the microprocessor; the signal output terminals of the self-source type vibration sensor are compared by the first operational amplifier and The device is respectively connected with the signal input terminal and the interrupt port of the microprocessor; the signal output terminal of the external source type acceleration sensor is connected with the other signal input terminal of the microprocessor through the second operational amplifier; the power supply of the external source type acceleration sensor The terminal is controlled by the current power supply output terminal selected by the second analog switching node of the microprocessor. The device has an obvious energy-saving effect, and can guarantee the wireless sensor network nodes to work continuously for a long time.

Description

Low-power wireless sensor network node device for continuous vibration monitoring

technical field

The technology of the invention relates to a low-power wireless sensor network node device that can continuously monitor vibration, and is suitable for application occasions that require real-time online monitoring, such as state monitoring and target detection. the

technical background

A wireless sensor network is an ad hoc network composed of a large number of low-cost sensor nodes. Nodes have wireless communication capabilities, not only responsible for the collection and processing of environmental information, but also receive and send data of themselves and the network, but their energy and other resources are limited. Since the power supply battery of the node is inconvenient to replace, maximum energy saving is the primary principle of node design. The wireless sensor network node is composed of four modules such as microprocessor, wireless communication, sensor and power supply. It is generally believed that the power consumption of the sensing module is very low, so the existing research basically only discusses the energy saving of the processor and the wireless communication device. Due to energy supply constraints, wireless sensor networks are generally suitable for environmental monitoring with low real-time requirements. When the sensor continues to work, its energy consumption is not necessarily lower than that of the communication module, and the higher the performance requirements, the greater the energy consumption. Therefore, it is difficult for existing wireless sensor nodes to adapt to applications such as status monitoring that require high real-time performance and require sensors to work continuously. the

The microprocessor is the control core of the whole node, responsible for data collection, processing and wireless communication, but it is not always in a high-load working state. Therefore, the microprocessor of the node should have a variety of working modes with different power consumption. Reasonably select a working mode that satisfies performance requirements and reduces power consumption under load conditions. the

In the previous low-power design of nodes, the sensor module operates with a low duty cycle. Therefore, the research on low-power technology of wireless sensor nodes ignores the influence of sensors, and lacks low-power design for sensor work. With the development of wireless sensor technology and the demand for real-time applications, there are many occasions in practice that require continuous online monitoring of vibration signals. Due to the continuous monitoring of vibration signals, even if low-power integrated sensor devices are used, the energy consumption of the sensor module accounts for a large proportion of the total energy consumption of the node, which cannot be ignored, and low-power design needs to be carried out according to task requirements and sensor characteristics. There are many types of sensors with different working principles and compositions. According to the energy relationship, sensors can be divided into self-source type and external source type. The output of the self-source sensor is directly converted from the measured energy without the need for an excitation power supply. However, the measurement accuracy is generally lower than that of the external source sensor due to weak signals. In the occasion of target detection and state monitoring, although the use of high-precision external source sensors can guarantee the accuracy requirements, when the appearance of the target is unpredictable, continuous use of this type of sensor monitoring will consume too much energy of the node battery and cannot meet the long-term requirements. job requirements. Only using self-sourced sensors can significantly reduce node energy consumption and prolong node life, but often its measurement accuracy and bandwidth are not enough. Therefore, there is an urgent need for a wireless sensor network node technology that can not only monitor continuously, but also have low power consumption. the

Different modules of wireless sensor network nodes have different working currents or voltages, and the currents of the same module are also different under different working conditions. From the consideration of energy saving, each module of the node has different power consumption working modes and working voltages, so the power supply needs to be adjusted. On the other hand, the different types of batteries used by the nodes, such as alkaline batteries and lithium batteries, make the actual nonlinear characteristics and output voltage ranges of the batteries different. In order to provide the required stable voltage for each module and make full use of the battery power, energy-efficient step-up, step-down or step-up/down regulation is required. Load changes and battery characteristics make the input and output of the node power regulator change, and the output current changes greatly. This requires the node power supply and management to not only meet the power specification and quality requirements required for node operation and performance, but also adapt to the load changes of other modules of the node, provide them with the voltage and current required for different working states, and at the same time reduce the load from Self-consumption of power supply under high load to no-load conditions, improving energy efficiency under different loads. At present, most nodes are directly powered by batteries, and some typical node platforms are only equipped with linear voltage regulators to maintain the stable voltage output of batteries, without realizing the energy saving of power modules. the

Contents of the invention

The purpose of the present invention is to propose a low-power wireless sensor network node device that can continuously monitor vibration. The device has obvious energy-saving effect and can ensure the continuous operation of the wireless sensor network node for a long time. the

Technical solution of the present invention is as follows:

A low-power wireless sensor network node device for sustainable monitoring of vibration, including a microprocessor, a power module, a communication module and a sensor module, and the power module, communication module and sensor module are all connected to the microprocessor;

The structure of the power module is as follows: the output terminals of the solar battery and the lithium battery are respectively connected to two input terminals of the first analog switch controlled by the microprocessor, and the output terminals of the first analog switch are stabilized The transformer is connected to the power interface of the microprocessor; the output terminal of the lithium battery is connected to the positive pole of the diode, and the negative pole of the diode is connected to the output terminal of the power module;

The structure of the sensor module is: the signal output end of the self-source type vibration sensor is connected with the signal input end of the microprocessor through the first operational amplifier, and the signal output end of the self-source type vibration sensor is connected with an input end of the comparator , the other input terminal of the comparator is connected to the output terminal of the reference voltage resistor divider circuit whose comparison threshold can be set by the numerical control potentiometer, and the output terminal of the comparator is connected to the interrupt port of the microprocessor;

The signal output end of the external source type acceleration sensor is connected with another signal input end of the microprocessor through the second operational amplifier; the power supply end of the external source type acceleration sensor is controlled by a switch of the second analog switch of the microprocessor The channel is connected to the output port of the power module; the power terminal of the first operational amplifier is connected to the output port of the power module through another switch channel controlled by the second analog switch of the microprocessor. the

The structure of the communication module is as follows: the wireless communication device is connected to the output port of the power supply module through the third analog switch controlled by the microprocessor, and the wireless communication device is connected to the microprocessor. the

A solar cell is connected in parallel with a supercapacitor. the

The microprocessor adopts an ultra-low power consumption microprocessor, and the regulator selects an integrated step-up/down voltage regulator that can maintain high energy efficiency under small loads, and the self-source acceleration sensor is composed of a piezoelectric vibration element combined with low power consumption The comparator and operational amplifier are composed of low-power integrated devices for the external source acceleration sensor. The first analog switch, the second analog switch and the third analog switch all use ultra-low power integrated electronic analog switches. The first operational amplifier and The second operational amplifiers all adopt low-power integrated chips, and the wireless communication devices adopt integrated modules. the

The model of the microprocessor is MSP430F1611, the model of the regulator is TPS63030, the self-source vibration sensor adopts the piezoelectric vibration element MiniSense 100, the model of the external source acceleration sensor is ADXL202E, the model of the first analog switch is ADG821, and the model of the second The model of the analog switch is ADG821, the model of the third analog switch is ADG821, the first operational amplifier and the second operational amplifier both use the TLV2402 chip, the comparator uses the TLV3492 chip, the reference voltage source uses the ref1112 chip, and the wireless communication device uses the CC2520 chip. The output voltage of the output port of the power module is 3V. the

The output terminal of the lithium battery is connected to the positive pole of the diode, and the negative pole of the diode is connected to the output terminal of the power module. , the lithium battery supplies power to the microprocessor through the diode. When the low-power wireless sensor network node device that continuously monitors vibration works stably, the diode branch will no longer work. the

Beneficial effect:

On the premise of ensuring performance requirements, the present invention realizes continuous monitoring of vibration signals in a low-power consumption manner and prolongs the service life of nodes, which are mainly reflected in the following aspects:

1. The present invention adopts the collaborative work mode of self-sourced and external-sourced sensors, which reduces the power consumption of the sensor module of the node, and can be adapted to applications such as state monitoring with high real-time requirements and continuous work of sensors. Even if the existing wireless sensor nodes use low-power external source integrated sensor devices, the minimum operating current is above 0.3mA under the same performance, which is generally at the mA level, and its power supply voltage is 3.3V. Consumption between 1 ~ 10mW. If the traditional node is applied in an occasion where the sensor needs to work continuously, when its working time is increased by 10 times, for example, from 1s to 10s, the energy consumption of the sensor module (measured by 1mW) will increase from 1mJ to 10mJ. The power supply voltage of the present invention is 3V, and the self-source type sensor is used to detect the target signal. If no target event occurs, the external source type sensor remains in a dormant state, and only the comparison circuit of the self-source type sensor consumes energy (power<20μW), and its 10s can Consumption <200μJ; if the target event occurs, start the external sensor to obtain high-precision measurement data, if the sleep time of the external sensor is the same as the working time (50% duty cycle), the energy consumption of the sensor module within 10s is only Increased to 4.7mJ (4.5+0.2=4.7), less than half of the energy consumption (10mJ) of traditional node sensor modules. Since the target event is a low-probability event, there are few cases where high-precision measurement is required. Therefore, if the probability of event occurrence is 1%, the energy consumption (average power consumption) of the sensor module of the present invention can be as low as that of a traditional node. 1/41 (0.45x0.01+0.02x1≈1/41). the

2. The present invention adopts a low power consumption module switch to switch the power supply mode of the node power supply, which improves the energy efficiency of the power supply and can obtain a longer service life. Most traditional nodes use voltage regulators to provide stable voltages for other modules in a fixed manner, but the energy efficiency of voltage regulators varies with load changes, and the average energy efficiency of general voltage regulators under small load currents is mostly no more than 75%; the present invention uses lithium The battery is the main power supply, and the solar battery is the auxiliary power supply. A voltage regulator that can maintain high energy efficiency (above 85%) under small loads is selected, and the voltage adjustment or direct power supply mode is dynamically selected according to the node load and the voltage of the solar battery, so that the power module The average energy efficiency is higher than 85%. At the same time, when the solar energy is sufficient, the battery is replenished with energy, so that the node can have a longer life. the

3. For the communication module, the wireless communication device periodically monitors the channel. If there is no received data, the microprocessor outputs a sleep command through the I/O port, so that the wireless communication device enters a low-power sleep mode; if there is data to send, Then transfer to dormant mode when the transmission is completed; for further energy saving, a low-power analog switch can be used to output a low level through the I/O port of the microprocessor, so that the low-power analog switch closes the power channel of the wireless communication device. Keep the wireless communication device in a power-off state. This design of the communication module can also significantly reduce the power consumption of the wireless sensor network nodes. the

Description of drawings

FIG. 1 is a structural block diagram of a low-power wireless sensor network node device for continuous vibration monitoring of the present invention. the

Fig. 2 is a circuit diagram of self-source sensor amplification and conditioning of the node device embodiment of the present invention. the

Fig. 3 is the circuit diagram of the motherboard of the embodiment of the node device of the present invention

Fig. 4 is a circuit diagram of a node self-source piezoelectric vibration element and a rectifier bridge. the

Figure 5 is a circuit diagram of the node external source type acceleration sensor. the

Fig. 6 is a schematic diagram of node wireless module control. the

Fig. 7 is a circuit diagram of the node power supply module. the

FIG. 8 is an overall structural diagram of a low-power wireless sensor network node device that can continuously monitor vibration. the

Detailed ways

The present invention will be further described in detail below in conjunction with the drawings and specific implementation process. the

Example 1:

As shown in Figure 1, the structural block diagram of a low-power wireless sensor network node device that can continuously monitor vibrations includes a microprocessor, a sensor module, a communication module, and a power supply module. The microprocessor is the core of the node, and other modules are connected with the microprocessor connected and controlled by a microprocessor. the

As shown in FIG. 2 , the device embodiment of the present invention is a self-source type sensor amplification and conditioning circuit diagram. The self-source piezoelectric vibration sensor MiniSense 100 (taking the vertical direction as an example) amplification and conditioning circuit includes a rectifier bridge, a low-power comparator TLV3492 and a low-power integrated operational amplifier TLV2402. The voltage output of the piezoelectric vibrating element is firstly rectified by the rectifier bridge, and then connected to an input terminal of the low-power comparator U13C and the positive input terminal of the low-power integrated operational amplifier U7C, and the output of the low-power integrated operational amplifier The end is connected with the A/D converter interface of the microprocessor U9C to realize the sampling of the output voltage of the piezoelectric vibration element; the other input end of the low-power comparator receives the reference voltage controlled by the microprocessor, and the controlled reference voltage The voltage circuit includes a low power consumption reference voltage source chip U10C and a digital potentiometer U14C, and controls the output voltage value of the reference voltage circuit through the 27 and 28 I/O pins of the microprocessor. When the over-threshold vibration signal appears, the output terminals "1" and "7" of the low-power comparator are respectively connected to the interrupt port "17" and "19" pins of the microprocessor, and the microprocessor is woken up through the interrupt mode Then, the microprocessor supplies power to the operational amplifier in the self-source piezoelectric vibration sensor through the second channel of the low-power analog switch U5C, so as to sample the output of the self-source piezoelectric sensor. If the sampling result shows If the vibration intensity of the signal is indeed greater than the threshold, that is, when the set target signal appears, the first channel of the low-power analog switch U5C is selected to activate the external-source acceleration sensor with high-precision and fast measurement performance. the

Waking up the dormant microprocessor through the output terminal of the comparator and making the operational amplifier (i.e. the first operational amplifier) in the self-source piezoelectric vibration sensor be connected with the output terminal of the power supply through an analog switch, on the one hand, in order to avoid errors One of the purposes of further sampling the output of the self-sourced piezoelectric sensor by the microprocessor is to check whether there is a malfunction, and the other is to save energy. The power supply starts only when it is used, which can significantly reduce energy consumption. the

As shown in Figure 3, the circuit diagram of the main board of the embodiment of the low-power wireless sensor network node device for continuous vibration monitoring of the present invention. The microprocessor uses MSP430F1611, the power supply voltage range is 1.8-3.6V, the internal functional modules can work independently, and its power consumption is 330uA in the active mode of 2.2V voltage and 1MHz clock frequency, and it has multi-level power consumption mode. The 3V voltage input port J2C of the motherboard is connected to the 3V voltage output port J16C of the power module. The wireless communication device and the JTAG programmer are respectively connected to the microprocessor through the wireless communication interface J5C and the JTAG interface J7C. The piezoelectric signal interface J9C and the acceleration signal interface J3C are used for the sampling of the sensor signal by the microprocessor and power control, while the power adjustment and switching of the power module are realized through the power control port J12C of the processor module, and J10C and J11C are the devices Reserved I/O port for expansion. Through the above-mentioned interface, the processor realizes the signal acquisition and power control of each module. the

As shown in Figure 4, the self-source piezoelectric vibration element and rectifier bridge circuit diagram of the example node, the piezoelectric vibration element MiniSense 100 is used to detect vibration signals in a certain direction, and the voltage sensitivity is 1V/g. The piezoelectric sensor interface J8C is connected to the piezoelectric signal interface J9C of the node motherboard, and is used to send the output voltage to the low-power comparator U13C on the motherboard. According to actual needs, the circuit can be installed in different positions and directions to realize multi-dimensional vibration detection. For example, if it is necessary to detect vibration signals in the vertical and horizontal directions in actual requirements, that is, two-dimensional vibration detection, two such circuits can be used, respectively placed in the vertical and horizontal directions. Similarly, if a three-dimensional or more dimensional vibration detection is required, it is only necessary to install three or more circuits in the positions and directions to be detected. the

As shown in FIG. 5 , the circuit diagram of the exogenous vibration sensor of the example node device, the acceleration sensor interface J1C is connected to the acceleration signal interface J3C of the node main board. In this example, the multi-dimensional acceleration sensor is a high-performance dual-axis accelerometer ADXL202E, with a working voltage of 3-5.25V, a working current of 0.6mA, a measuring range of ±2g, and a sensitivity of 167mV/g. It consumes a lot of power but has high measurement accuracy. The frequency bandwidth is wide, and its output is connected to the RC filter circuit, and then sent to the acceleration sensor interface J1C after being amplified by the low-power amplifier "U2C". The microprocessor sets the "P1.3" I/O port to a high level, thereby strobing the first channel of the low-power analog switch U5C, that is, the second pin of U5C is connected to the 3V power supply provided to the acceleration sensor , thereby starting the acceleration sensor in order to obtain high-precision measurement data; on the contrary, if the microprocessor sets the I/O port corresponding to P1.3 to a low level, the 3V power supply of the acceleration sensor is cut off and the sensor is turned off. the

As shown in Figure 6, the wireless module control diagram of the example node, the microprocessor MSP430F1611 and the wireless communication device are connected through three buses, which are power control line, data line and control line. The wireless communication device periodically monitors the channel. If there is no received data, the microprocessor outputs a dormancy command through the control line to make the wireless communication device go into a low-power sleep mode; if there is data to be sent, it turns into Sleep mode; in order to further save energy, you can use the power control line to output a low level to disconnect the strobe channel of the low-power analog switch (1/2 ADG821), so that the wireless communication device (CC2520) is in a power-off state middle. the

The circuit diagram of the power module of the example node is shown in Figure 7. The power adjustment circuit uses the step-up/down regulator TPS63030, the input voltage range is 1.8V to 5.5V, and the output current can reach 500mA when the input voltage is 3V. In the energy-saving mode, When the output current is reduced to about 1mA, the energy efficiency can still be kept above 85%. The solar battery interface J13C, supercapacitor interface J14C and rechargeable lithium battery interface J15C with wide input voltage range are respectively connected to the solar battery, supercapacitor and rechargeable lithium battery. The 3V voltage output port J16C and the power module control port J17C are respectively connected to the 3V voltage input port J2C of the microprocessor and the processor module power control port J12C. When the node device is first powered on, the output voltage of the lithium battery is directly stepped down by a diode and a resistor (less than 3V) and then sent to the microprocessor to start the microprocessor. Then, the microprocessor controls the low-power analog switch U17C, that is, 1.5 One ADG821 realizes power supply management, and can choose between solar battery power supply, lithium battery power supply, direct output and regulated output through a voltage regulator, etc., to realize the control of node power supply, so as to maximize the energy efficiency of the power supply, Thereby prolonging the service life. The power supply mode selection strategy is as follows:

1. When the voltage of the solar cell is greater than 3V, the pin 31 of the microprocessor is set to a high level, and the solar cell is directly used as the power supply; when the voltage of the solar cell is lower than 3V but still higher than the lower limit value of the input voltage of the regulator TPS63030, The pin 30 and pin 32 of the microprocessor are set at high level, so that the voltage output of the solar cell is adjusted to a stable 3V power supply through the regulator TPS63030, which is used as the power supply of the node; if the voltage of the solar cell is lower than the input voltage of the regulator lower limit value, the solar cell is not used. the

2. On the premise of not using solar cells, when the lithium battery voltage is higher than 3.3V (3V+diode tube voltage drop 0.3V), or lower than 3V but still higher than the lower limit of the input voltage of the regulator TPS63030 When the microprocessor "32" pin is set to high level, start to adjust the voltage regulator TPS63030, and use the output of the voltage regulator as the node power supply; when the voltage of the lithium battery is lower than 3.3V and not lower than 3V, the lithium battery is directly used The battery is used as the power supply; if the voltage of the lithium battery is lower than the lower limit value of the input voltage of the regulator TPS63030, it indicates that the power of the node has been exhausted. the

Since it is necessary to judge the voltage of the solar cell and the lithium battery, there must be a circuit for measuring the voltage of the solar cell and the lithium battery, and the measured signal is sent to the microprocessor for processing. This part of the circuit is an existing mature technology. the

Claims (4)

1. A low-power consumption wireless sensor network node device for sustainable monitoring of vibrations, comprising a microprocessor, a power module, a communication module and a sensor module, and the power module, the communication module and the sensor module are all connected to the microprocessor; It is characterized by: The structure of the power supply module is as follows: the output terminals of the solar cell and the lithium battery are respectively connected to two input terminals of the first analog switch controlled by the microprocessor, and the output terminals of the first analog switch are adjusted The voltage regulator is connected to the power interface of the microprocessor; the output terminal of the lithium battery is connected to the positive pole of the diode, and the negative pole of the diode is connected to the output terminal of the power module; The structure of the sensor module is: the signal output end of the self-source type vibration sensor is connected with the signal input end of the microprocessor through the first operational amplifier, and the signal output end of the self-source type vibration sensor is connected with an input end of the comparator , the other input terminal of the comparator is connected to the output terminal of the reference voltage resistor divider circuit whose comparison threshold can be set by the numerical control potentiometer, and the output terminal of the comparator is connected to the interrupt port of the microprocessor; The signal output end of the external source type acceleration sensor is connected with another signal input end of the microprocessor through the second operational amplifier; the power supply end of the external source type acceleration sensor is controlled by a switch of the second analog switch of the microprocessor The channel is connected to the output port of the power module; the power terminal of the first operational amplifier is connected to the output port of the power module through another switch channel controlled by the second analog switch of the microprocessor. 2. The low-power consumption wireless sensor network node device of sustainable monitoring vibration according to claim 1, characterized in that, the structure of the communication module is: the wireless communication device is controlled by the third simulation of the microprocessor The switch is connected to the output port of the power supply module, and the wireless communication device is connected with the microprocessor. 3. The low power consumption wireless sensor network node device for continuously monitoring vibration according to claim 1 or 2, characterized in that the solar cell is connected in parallel with the supercapacitor. 4. The low-power wireless sensor network node device for sustainable monitoring of vibration according to claim 2, characterized in that the model of the microprocessor is MSP430F1611, the model of the regulator is TPS63030, and the self-source vibration sensor adopts voltage Electric vibration element MiniSense 100, the model of external acceleration sensor is ADXL202E, the model of the first analog switch is ADG821, the model of the second analog switch is ADG821, the model of the third analog switch is ADG821, the first operational amplifier and the second The operational amplifier adopts TLV2402 chip, the comparator adopts TLV3492 chip, the reference voltage source adopts ref1112 chip, the wireless communication device adopts CC2520 chip, and the output voltage of the output port of the power module is 3V.

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