Energy management method for self-driving wireless sensor nodes

Abstract

The present invention proposes an energy management method for a self-driven wireless sensor node. The method can calculate the captured environmental energy intensity according to the power consumption state of the energy storage element after power-on initialization, and then determine the working cycle of the working mode of "continuously collecting and sending after power-on until the power is consumed to the low-voltage threshold and re-entering the charging cycle" or "calculating the sleep and wake-up cycle after power-on, and then performing periodic sleep, wake-up, data collection and transmission, and sleep cycle according to the cycle", and select the working mode with the shortest working cycle to maximize energy utilization efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of wireless sensors, and in particular relates to an energy management method for a self-driven wireless sensor node. Background Art

[0002] For a self-driven wireless sensor node, it is necessary to include modules such as energy harvester, energy management circuit (PMIC), energy storage element, load switch, BUCK or LDO circuit, system load, etc. The energy collected by the energy harvester is converted to a level by the energy management circuit to charge the energy storage element. The energy management circuit realizes the on or off control of the load switch by setting the high voltage and low voltage thresholds of the capacitor voltage. In addition, a BUCK or LDO circuit is generally required at the back stage of the load switch for level conversion, converting the output voltage of the front stage PMIC into a level that can be used by the back stage microcontroller, sensor and other system loads.

[0003] When the energy storage value of the energy storage element reaches the set threshold, the load switch is turned on to discharge the system load. When the input energy intensity is low, the system cannot maintain long-term operation and will initiate data collection and transmission as soon as possible until the energy storage element is exhausted. Therefore, the system will work in a repeated charging and discharging manner, with the load switch intermittently turned on and off, and the system load intermittently working, and stop working when power is lost. When the input energy intensity is strong, it is sufficient to support the continuous operation of the system load, or sufficient to support the intermittent sleep and wake-up operation of the system. The working mode at this time is the continuous working mode. In the design process, each component of the wireless sensor node has a certain number of bypass and filter capacitors. During each power-on process, these capacitors need to be recharged, resulting in a large amount of power-on power consumption. If the system adopts a working mode of continuously initiating data collection and transmission until the energy storage element is exhausted, the only additional power consumption during the charging process is the leakage current of the energy storage element, but the additional power consumption of power-on initialization is generated during the discharge stage. If the system adopts an intermittent sleep and wake-up mode, although the additional power consumption generated by the secondary initialization is avoided, the sleep power consumption during the sleep charging process is increased.

[0004] In summary, the problem existing in the prior art is that an energy management algorithm is needed to balance the relationship between input energy and working mode to maximize the energy management efficiency of the system. Summary of the invention

[0005] The purpose of the present invention is to solve the problems in the prior art and propose an energy management method for a self-driving wireless sensor node.

[0006] The present invention is implemented by the following technical solution. The present invention proposes an energy management method for a self-driving wireless sensor node, and the method comprises the following steps:

[0007] S1: The capacitor voltage reaches the high-voltage discharge threshold, the load switch is turned on, the capacitor is discharged, and the system load is powered;

[0008] S2: System load initialization;

[0009] S3: Measure the capacitor voltage, recorded as U2;

[0010] S4: Determine whether condition 1 is met. If condition 1 is not met, execute S7. If condition 1 is met, execute S5.

[0011] S5: Continuously initiate sensor data and send it wirelessly to the host;

[0012] S6: The capacitor voltage is consumed to the low voltage threshold, the load switch is turned off, and the capacitor stops discharging;

[0013] S7: Calculate the sleep-wake cycle T B ;

[0014] S8: Set the RTC clock interrupt period to (T B )s;

[0015] S9: collect sensor data and send it wirelessly to the host once;

[0016] S10: Sleep (T)s, return to S8.

[0017] Furthermore, condition 1 in S4 is deltaT<0.

[0018] Furthermore, the deltaT is calculated by formula 13:

[0019]

[0020] Furthermore, T in Formula 13 A and T B Calculated by formula 5 and formula 10 respectively;

[0021]

[0022]

[0023] Furthermore, Formula 1 represents the differential relationship between the PMIC output energy and the capacitor charging and capacitor self-leakage during the charging process. In this formula, C is the capacitance of the energy storage capacitor, U is the voltage value on the energy storage capacitor, and I s1 is the self-leakage current of the energy storage capacitor, P out is the PMIC output power, the load switch self-leakage current is ignored; I s1Its value is small. To simplify the calculation, the second term of Formula 1 is equivalent to a certain value, as shown in Formula 2. Substitute Formula 2 into Formula 1 and simplify to obtain Formula 3. Integrate both ends to obtain Formula 4, where U H is the high voltage discharge threshold, U L is the low voltage discharge threshold, T A is the charging time of working mode A; from formula 4, we get formula 5, T A With P out The relationship is expressed by formula 5;

[0024]

[0025]

[0026]

[0027]

[0028] Furthermore, the working mode A is: continuously collecting and sending after power-on until the power is consumed to the low voltage threshold, and then re-entering the charging cycle.

[0029] Furthermore, the expression of the output energy of PMIC during charging, load sleep power consumption, capacitor charging energy consumption and capacitor self-leakage energy consumption is shown in Formula 6, where I s2 is the load sleep power consumption, U B is the output voltage of the BUCK circuit, η B is the conversion efficiency of the BUCK circuit. To simplify the calculation, the second term, the capacitor self-leakage, is simplified as shown in Formula 7. Substitute Formula 7 into Formula 6 and simplify it to get Formula 8. Integrate the two ends to get Formula 9, where U1 is the voltage value on the capacitor after the system load performs a single collection and transmission work and the charge is consumed. T B is the charging time of working mode B, the integral result is T B It can be expressed by formula 10;

[0030]

[0031]

[0032]

[0033]

[0034] Furthermore, the working mode B is: after power-on, the sleep-wake-up cycle is calculated, and then periodic sleep, wake-up, data collection and transmission and sleep cycles are performed according to the cycle.

[0035] Further, the voltage value U1 is calculated, as shown in formula 11. The first term is the capacitor discharge during a single acquisition and transmission operation, the second term is the output energy of the PMIC during a single acquisition and transmission operation, and the third term is the power consumption of the system load for a single transmission. Formula 11 can be simplified to formula 12 to obtain the expression of the voltage value U1. Substituting this formula into formula 10 can obtain T B The completed expression of T A With T B Subtract and we get formula 13. In formula 13, we can get the working time of working mode A and working mode B and P out relationship;

[0036]

[0037]

[0038] Furthermore, when the system is powered on and initialized, the PMIC output energy intensity can be determined based on the initialization power consumption state, as shown in Formula 14. Due to the high energy consumption during the initialization period, the capacitor self-leakage is ignored in this formula. Simplifying Formula 14, we can obtain Formula 15, that is, the PMIC output power P out The expression of P out Substitute into formula 13 and calculate the positive and negative of deltaT to determine which working mode to use at this time;

[0039]

[0040]

[0041] Beneficial effects of the present invention:

[0042] (1) The method described in the present invention accurately calculates the relationship between the working cycle and the PMIC output power in two working modes.

[0043] (2) The system operating mode is linked to the calculated working cycles of the two operating modes. When the PMIC output power is the same, the operating mode with the shortest working cycle is selected.

[0044] (3) After the known quantity is substituted into the formula, the calculation formula for judging the working mode will be greatly simplified, thereby greatly reducing the computing energy consumption of the microprocessor, and only one calculation is required to run according to the calculation result. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 The present invention provides an operation flow chart of an energy management method for a self-driving wireless sensor node. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] In order to overcome the problems existing in the prior art, the present invention provides an energy management method for a self-driven wireless sensor node, which realizes switching between two working modes by dividing the energy input intensity, and can maximize the reduction of the loss of wireless sensor node input energy in the application.

[0048] The present invention defines two working modes: working mode A: continuous collection and transmission after power-on until the power is consumed to the low-voltage threshold and re-enters the charging cycle; working mode B: calculating the sleep and wake-up cycle after power-on, and then performing periodic sleep, wake-up, data collection and transmission, and sleep cycles according to the cycle.

[0049] When the PMIC output energy is the same, the one with a shorter single working cycle in the two working modes consumes less energy and is more efficient. For working mode A, during its charging process, due to the no-load sleep power consumption, the charging rate is higher and the charging time may be shorter. For working mode B, since it does not require secondary initialization, after the first initialization, after each acquisition and transmission work is completed, the capacitor voltage does not drop to the low voltage threshold, and the capacitor is always in a charging cycle from the intermediate voltage to the high voltage threshold, and the charging time may be shorter. The method described in the present invention will derive and compare the working cycle lengths of the two working modes through formula derivation, and derive the relationship between the difference in working time of the two working modes and the output energy of the PMIC.

[0050] In the present invention, a capacitor is selected as an energy storage element for analysis, and other energy storage elements have similar analysis methods. In the present invention, a BUCK circuit is selected as a level conversion form after a load switch, and a similar analysis method is used for LDO.

[0051] In the present invention, it is assumed that the energy storage capacitor value and the discharge voltage threshold have been determined, the power consumption of system initialization and single data collection and transmission has been measured, the system sleep power consumption and system operating voltage are known, and the BUCK circuit conversion efficiency is fixed. In the following estimation, the discharge time (generally a few ms to more than ten ms) accounts for a very small proportion of the entire working cycle, and the discharge time of the two modes is close, so the working cycle duration is only counted into the charging time.

[0052] Combination Figure 1 The present invention proposes an energy management method for a self-driving wireless sensor node, the method comprising the following steps:

[0053] S1: The capacitor voltage reaches the high-voltage discharge threshold, the load switch is turned on, the capacitor is discharged, and the system load is powered;

[0054] S2: System load initialization;

[0055] S3: Measure the capacitor voltage, recorded as U2;

[0056] S4: Determine whether condition 1 is met. If condition 1 is not met, execute S7. If condition 1 is met, execute S5.

[0057] S5: Continuously initiate sensor data and send it wirelessly to the host;

[0058] S6: The capacitor voltage is consumed to the low voltage threshold, the load switch is turned off, and the capacitor stops discharging;

[0059] S7: Calculate the sleep-wake cycle T B ;

[0060] S8: Set the RTC clock interrupt period to (T B )s;

[0061] S9: collect sensor data and send it wirelessly to the host once;

[0062] S10: Sleep (T)s, return to S8.

[0063] Condition 1 in S4 is deltaT < 0. Substituting the voltage U2 measured in S3 into formula 15, P is calculated. out , and then P out Substitute into formula 13 to get deltaT, and execute S4 according to the judgment of condition 1. If condition 1 is met, deltaT < 0, which proves that the cycle of working mode A is less than that of working mode B, and the power consumption of working mode A is less than that of working mode B. Therefore, working mode A continues to work until the power is exhausted. If condition 1 is not met, it works according to working mode B, and it is necessary to calculate the system sleep wake-up cycle.

[0064] The deltaT is calculated by formula 13:

[0065]

[0066] T in Formula 13 A and T B Calculated by formula 5 and formula 10 respectively;

[0067]

[0068]

[0069] For working mode A, formula 1 represents the differential relationship between the PMIC output energy and the capacitor charging and capacitor self-leakage during the charging process. In this formula, C is the capacitance of the energy storage capacitor, U is the voltage value on the energy storage capacitor, and I s1 is the self-leakage current of the energy storage capacitor, P out is the PMIC output power, the load switch self-leakage current (usually a few nA) is ignored; I s1 Generally, it is several hundred nA to several uA. Compared with the other two terms in formula 1, its value is smaller. To simplify the calculation, the second term of formula 1 is equivalent to a certain value, as shown in formula 2. Substitute formula 2 into formula 1 and simplify to get formula 3. Integrate both ends to get formula 4, where U H is the high voltage discharge threshold, U L is the low voltage discharge threshold, T A is the charging time of working mode A; from formula 4, we get formula 5, T A With P out The relationship is expressed by formula 5;

[0070]

[0071]

[0072]

[0073]

[0074] For working mode B, the output energy of PMIC during charging, load sleep power consumption, capacitor charging energy consumption and capacitor self-leakage energy consumption are expressed as shown in Formula 6, where I s2 is the load sleep power consumption, U B is the output voltage of the BUCK circuit, η B is the conversion efficiency of the BUCK circuit. To simplify the calculation, the second term, the capacitor self-leakage, is simplified as shown in Formula 7. Substitute Formula 7 into Formula 6 and simplify it to get Formula 8. Integrate the two ends to get Formula 9, where U1 is the voltage value on the capacitor after the system load performs a single collection and transmission work and the charge is consumed. T B is the charging time of working mode B, the integral result is T B It can be expressed by formula 10;

[0075]

[0076]

[0077]

[0078]

[0079] Calculate the voltage value U1, as shown in formula 11. The first item is the capacitor discharge during a single acquisition and transmission operation, the second item is the output energy of the PMIC during a single acquisition and transmission operation, and the third item is the power consumption of a single transmission of the system load. Formula 11 can be simplified to formula 12 to obtain the expression of the voltage value U1. Substituting this formula into formula 10 can obtain T B The completed expression of T A With T B Subtract and we get formula 13. In formula 13, we can get the working time of working mode A and working mode B and P out relationship;

[0080]

[0081]

[0082] When the system is powered on and initialized, the PMIC output energy intensity can be determined based on the initialization power consumption state, as shown in Formula 14. Due to the high energy consumption during the initialization period, the capacitor self-leakage is ignored in this formula. Simplifying Formula 14, we can get Formula 15, that is, the PMIC output power P out The expression of P out Substitute into formula 13 and calculate the positive and negative of deltaT to determine which working mode to use at this time;

[0083]

[0084]

[0085] The above is a detailed introduction to the energy management method of a self-driving wireless sensor node proposed in the present invention. This article uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for general technical personnel in this field, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. An energy management method for a self-driving wireless sensor node, characterized in that: The method comprises the following steps: S1: The capacitor voltage reaches the high-voltage discharge threshold, the load switch is turned on, the capacitor is discharged, and the system load is powered; S2: System load initialization; S3: Measure the capacitor voltage, recorded as U2; S4: Determine whether condition 1 is met. If condition 1 is not met, execute S7. If condition 1 is met, execute S5. S5: Continuously initiate sensor data and send it wirelessly to the host; S6: The capacitor voltage is consumed to the low voltage threshold, the load switch is turned off, and the capacitor stops discharging; S7: Calculate the sleep-wake cycle T B ; S8: Set the RTC clock interrupt period to (T B )s; S9: collect sensor data and send it wirelessly to the host once; S10: sleep (T)s, return to S8; Condition 1 in S4 is deltaT<0; The deltaT is calculated by formula 13: T in Formula 13 A and T B Calculated by formula 5 and formula 10 respectively; Formula 1 shows the differential relationship between the PMIC output energy and the capacitor charging and capacitor self-leakage during the charging process. In this formula, C is the capacitance of the energy storage capacitor, U is the voltage value on the energy storage capacitor, and I s1 is the self-leakage current of the energy storage capacitor, P out is the PMIC output power, the load switch self-leakage current is ignored; I s1 Its value is small. To simplify the calculation, the second term of Formula 1 is equivalent to a certain value, as shown in Formula 2. Substitute Formula 2 into Formula 1 and simplify to obtain Formula 3. Integrate both ends to obtain Formula 4, where U H is the high voltage discharge threshold, U L is the low voltage discharge threshold, T A is the charging time of working mode A; from formula 4, we get formula 5, T A With P out The relationship is expressed by formula 5; The working mode A is: after power-on, continuous collection and transmission is performed until the power is consumed to the low voltage threshold and the charging cycle is re-entered; The expression of the output energy of PMIC, load sleep power consumption, capacitor charging energy consumption and capacitor self-leakage energy consumption during charging is shown in Formula 6, where I s2 is the load sleep power consumption, U B is the output voltage of the BUCK circuit, η B is the conversion efficiency of the BUCK circuit. To simplify the calculation, the second term, the capacitor self-leakage, is simplified as shown in Formula 7. Substitute Formula 7 into Formula 6 and simplify it to get Formula 8. Integrate the two ends to get Formula 9, where U1 is the voltage value on the capacitor after the system load performs a single collection and transmission work and the charge is consumed. T B is the charging time of working mode B, the integral result is T B It can be expressed by formula 10; The working mode B is: after power-on, the sleep-wake-up cycle is calculated, and then the sleep, wake-up, data collection and transmission and sleep cycles are performed periodically according to the cycle; Calculate the voltage value U1, as shown in formula 11. The first item is the capacitor discharge during a single acquisition and transmission operation, the second item is the output energy of the PMIC during a single acquisition and transmission operation, and the third item is the power consumption of a single transmission of the system load. Formula 11 can be simplified to formula 12 to obtain the expression of the voltage value U1. Substituting this formula into formula 10 can obtain T B The completed expression of T A With T B Subtract and we get formula 13. In formula 13, we can get the working time of working mode A and working mode B and P out relationship; Among them, t Single Indicates the time length consumed by a single collection and sending work of the system load, Q Single Indicates the amount of charge consumed by the system load in a single acquisition and transmission operation; When the system is powered on and initialized, the PMIC output energy intensity can be determined based on the initialization power consumption state, as shown in Formula 14. Due to the high energy consumption during the initialization period, the capacitor self-leakage is ignored in this formula. Simplifying Formula 14, we can get Formula 15, that is, the PMIC output power P out The expression of P out Substitute into formula 13 and calculate the positive and negative of deltaT to determine which working mode to use at this time; Among them, t init Indicates the time consumed by system load initialization, Q init Indicates the amount of charge consumed by system load initialization.

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