Strain acquisition controller and method of controlling the same

Abstract

The application belongs to the technical field of mechanical strain measurement, and discloses a strain acquisition controller and a control method thereof. The strain acquisition controller comprises a programmed constant voltage source, a current-limiting resistor, a strain gauge resistor network, a first analog switch, a second analog switch, an amplifier, an ADC conversion circuit, an MCU module, a wireless transmission module and an electronic adjustable potentiometer. The strain gauge resistor network comprises N strain gauge single-arm bridges, and N is greater than or equal to 4. The strain gauge resistor network is used for converting a strain signal into an analog signal with resistance variation. The high potential end of the programmed constant voltage source is connected to the common end of the first analog switch through the current-limiting resistor. The i-th branch pin in the first analog switch is connected to the i-th strain gauge single-arm bridge in the strain gauge resistor network, and 1 is less than or equal to i and i is less than or equal to N. The application is suitable for online measurement of the strain of a drum girth weld, early warning of the fracture of the girth weld, miniaturization of the strain acquisition controller and reduction of power consumption.

Description

Technical Field

[0001] This invention belongs to the field of mechanical strain measurement technology, and relates to a strain acquisition controller and its control method. Background Technology

[0002] Large belt conveyors are the main equipment for material transportation in enterprises such as mines and ports. In belt conveyors, large rollers act as both driving and driven wheels. If fatigue failure of the rollers is not detected in time, it will cause the entire industrial production line to break.

[0003] Numerous experiments have shown that fatigue failure of drive rollers typically occurs in high-stress areas or at material defects. When the stress value reaches a certain level, the circumferential weld on the roller body is the first area where fatigue failure occurs. The safe operation of large rollers during use is crucial to the normal operation of the conveyor line. Therefore, fatigue strength testing of the roller circumferential weld is necessary. Online monitoring of the stress in the circumferential weld can provide early warning of weld fracture.

[0004] Strain gauges are commonly used stress-strain measurement sensors. They convert strain changes in a structure into resistance changes, and stress changes in the structure can be calculated by measuring the resistance changes through electronic circuits. However, traditional stress-strain testing instruments require long and complex wiring for stress testing of large roller circumferential welds. This is inconvenient for on-site installation, and the long wiring often interferes with the analog small signals of the strain gauges, affecting data reading. Furthermore, size and power consumption limitations prevent online monitoring of multiple strain points on rotating objects. Summary of the Invention

[0005] The purpose of this invention is to provide a strain acquisition controller that can realize early warning of circumferential weld fracture by online measurement of strain in the circumferential weld of the drum.

[0006] To achieve the above objectives, the technical solution adopted by this invention is as follows:

[0007] A strain acquisition controller includes a programmable constant voltage source, a current-limiting resistor, a strain gauge resistor network, a first analog switch, a second analog switch, an amplifier, an ADC conversion circuit, an MCU module, a wireless transmission module, and an electronically adjustable potentiometer.

[0008] The strain gauge resistor network includes N strain gauge single-arm bridges, N≥4, used to convert strain signals into analog signals of resistance changes;

[0009] The high potential end of the programmable constant voltage source is connected to the common terminal of the first analog switch through a current limiting resistor. The i-th branch pin of the first analog switch is connected to the i-th strain gauge single-arm bridge in the strain gauge resistor network, 1≤i≤N.

[0010] The i-th branch pin of the second analog switch is connected to the i-th strain gauge single-arm bridge in the strain gauge resistor network, and the non-inverting input terminal of the amplifier is connected to the common terminal of the second analog switch to amplify the analog signal output by the analog switch.

[0011] The input terminal of the ADC conversion circuit is connected to the output terminal of the amplifier, and is used to convert the analog signal output by the amplifier into a digital signal.

[0012] The input terminal of the MCU module is connected to the output terminal of the ADC conversion circuit, and is used to receive the digital signal, process the data to obtain the average value, maximum value and minimum value of the digital signal; the MCU module is communicatively connected to the wireless transmission module, and is used to transmit the data processed by the MCU module to an external host computer, and send the control commands of the external host computer to the MCU module;

[0013] The power control output terminal of the MCU module is connected to the power control input terminal of the programmable constant voltage source. After receiving the power control command, the programmable constant voltage source starts or stops. The resistance adjustment signal output terminal of the MCU module is connected to the resistance control terminal of the electronically adjustable potentiometer. After receiving the resistance adjustment command, the electronically adjustable potentiometer adjusts to the corresponding resistance value to regulate the output voltage of the programmable constant voltage source. The feedback terminal of the electronically adjustable potentiometer is connected to the inverting input terminal of the amplifier. The amplifier is used to adjust the gain according to the resistance value of the electronically adjustable potentiometer. The gating signal output terminal of the MCU module is connected to the control terminals of the first analog switch and the second analog switch respectively. After receiving the gating control command, the first analog switch and the second analog switch perform the same switching connection on the multi-channel strain gauge single-arm bridge in the strain gauge resistor network.

[0014] As a limitation, the strain gauge resistor network includes a balancing resistor unit and a strain gauge unit. The balancing resistor unit includes N balancing resistors and N Zener diodes, and the strain gauge unit includes N strain gauges.

[0015] One end of the i-th balancing resistor in the balancing resistor unit is connected to one end of the corresponding i-th strain gauge in the strain gauge unit to form the i-th strain gauge single-arm bridge of the strain gauge resistor network. The i-th strain gauge single-arm bridge is connected to the i-th branch pin of the second analog switch through a signal line at the node where the balancing resistor and the strain gauge are connected.

[0016] In the balancing resistor unit, the other end of the i-th balancing resistor is connected to the positive terminal of the i-th Zener diode, and the negative terminal of the i-th Zener diode, the other end of the i-th strain gauge, and the i-th branch pin of the first analog switch are all connected; the positive terminals of the N Zener diodes are all connected to the low potential terminal of the programmable voltage source.

[0017] As a second limitation, the wireless transmission module is a Bluetooth Low Energy module.

[0018] As a third limitation, both the first analog switch and the second analog switch are single or multiple low on-resistance double-pole four-throw analog switches.

[0019] As a fourth limitation, the amplifier is a differential amplifier.

[0020] The present invention also provides a control method for a strain acquisition controller, which is implemented using the strain acquisition controller described above, and includes the following steps:

[0021] S1. The MCU module receives the wake-up command from the external host computer through the wireless transmission module, enters the working mode from the power-down mode, and sends a power control command to the programmable constant voltage source to start the programmable constant voltage source.

[0022] S2. The MCU module sends a selection control command to the first analog switch and the second analog switch to select the first strain gauge single-arm bridge. The programmable constant voltage source provides a constant voltage excitation to the first strain gauge single-arm bridge through the current limiting resistor.

[0023] S3. The MCU module outputs a resistance adjustment command according to the preset zero-adjustment resistance value. The electronic adjustable potentiometer receives the resistance adjustment command and adjusts it to the corresponding resistance value.

[0024] S4. After the circuit stabilizes, the analog signal output from the second analog switch is received by the amplifier and amplified. Then, the analog signal output by the amplifier is converted into a digital signal by the ADC conversion circuit.

[0025] S5. The MCU module receives the digital signal output by the ADC conversion circuit, continuously reads and records multiple digital signals, and records the average, maximum and minimum values ​​of the digital signals;

[0026] S6. The MCU module sends a selection control command to the first analog switch and the second analog switch. The first analog switch and the second analog switch select one of the remaining strain gauge single-arm bridges in the strain gauge resistor network. Repeat steps S3 to S6 until all N strain gauge single-arm bridges of the strain gauge resistor network have completed one acquisition.

[0027] S7. The MCU module transmits the average, maximum, and minimum values ​​of the N-channel strain gauge single-arm bridge of the strain gauge resistor network to an external host computer via a wireless transmission module.

[0028] S8. According to the external host computer control instructions, the MCU module sends a power control instruction to the programmable constant voltage source to shut down the programmable constant voltage source, and the MCU module enters power-down mode.

[0029] As a limitation, in step S5, when recording the average, maximum, and minimum values ​​of the digital signal:

[0030] When the ratio between the difference between the maximum and the average, and between the absolute values ​​of the difference between the minimum and the average, exceeds twice, multiple digital signals are re-read and recorded, along with the average, maximum, and minimum values ​​of the digital signals.

[0031] When, in n consecutive records, n≥3, the ratio between the absolute values ​​of the difference between the maximum and average values, and the difference between the minimum and average values, all exceed twice, record the most recent average, maximum, and minimum values.

[0032] The present invention, by adopting the above-described technical solution, achieves the following technical advancements compared to existing technologies:

[0033] (1) The strain acquisition controller of the present invention includes a programmable constant voltage source, a current limiting resistor, a strain gauge resistor network, a first analog switch, a second analog switch, an amplifier, an ADC conversion circuit, an MCU module, a wireless transmission module, and an electronically adjustable potentiometer; wherein the first analog switch and the second analog switch realize the automatic switching acquisition of N strain gauge single-arm bridges (N≥4) in the strain gauge resistor network, which improves the scalability and applicability of the system; the MCU module controls the start and stop of the programmable constant voltage source, and the output voltage is dynamically adjusted in combination with the electronically adjustable potentiometer to realize low power consumption management of the power supply, which is convenient for low power consumption strain monitoring scenarios; the MCU module controls the resistance value of the electronically adjustable potentiometer to realize gain adjustment and zero-point calibration, which is convenient for batch adjustment and automatic correction;

[0034] (2) The strain acquisition controller of the present invention realizes the monitoring of multiple strain points in a limited space, and has the advantages of miniaturization and power consumption reduction, which can meet the online monitoring of multiple strain points of rotating objects such as roller ring welds;

[0035] (3) The MCU module of the present invention supports power-down mode and is woken up by wireless command. It only starts the programmable constant voltage source and strain acquisition controller during acquisition, which greatly reduces power consumption;

[0036] (4) The MCU module of the present invention samples each signal multiple times and calculates the average, maximum and minimum values, thereby improving data quality and anti-interference capability.

[0037] In summary, this invention is suitable for online measurement of strain in roller circumferential welds, early warning of weld fracture, miniaturization of strain acquisition controller, and reduction of power consumption. Attached Figure Description

[0038] Figure 1The diagram shown is a circuit schematic of the strain acquisition controller according to Embodiment 1 of the present invention.

[0039] In the diagram: 1. Programmable constant voltage source; 2. Current limiting resistor; 3. First analog switch; 4. Second analog switch; 5. Amplifier; 6. ADC conversion circuit; 7. MCU module; 8. Wireless transmission module; 9. Electronic adjustable potentiometer; 10. Strain gauge resistor network; 11. Balancing resistor; 12. Zener diode; 13. Strain gauge. Detailed Implementation

[0040] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] Example 1

[0042] like Figure 1 As shown, this embodiment is a strain acquisition controller, including a programmable constant voltage source 1, a current limiting resistor 2, a strain gauge resistor network 10, a first analog switch 3, a second analog switch 4, an amplifier 5, an ADC conversion circuit 6, an MCU module 7, a wireless transmission module 8, and an electronically adjustable potentiometer 9.

[0043] In this embodiment, the strain gauge resistor network 10 includes N strain gauge single-arm bridges, where N≥4, used to convert the strain signal into an analog signal of resistance change.

[0044] The high potential end of the programmable constant voltage source 1 is connected to the common terminal of the first analog switch 3 through the current limiting resistor 2. The i-th branch pin of the first analog switch 3 is connected to the i-th strain gauge single-arm bridge in the strain gauge resistor network 10, where 1≤i≤N.

[0045] The i-th branch pin of the second analog switch 4 is connected to the i-th strain gauge single-arm bridge in the strain gauge resistor network 10. The non-inverting input terminal of the amplifier 5 is connected to the common terminal of the second analog switch 4 to amplify the analog signal output by the analog switch. The number of branch pins in the first analog switch 3 and the second analog switch 4 is greater than or equal to the number of strain gauge single-arm bridges in the strain gauge resistor network 10, so that each strain gauge single-arm bridge in the strain gauge resistor network 10 can be connected to the corresponding branch pins in the first analog switch 3 and the second analog switch 4 respectively.

[0046] The input terminal of the ADC conversion circuit 6 is connected to the output terminal of the amplifier 5, and is used to convert the analog signal output by the amplifier 5 into a digital signal.

[0047] The input terminal of MCU module 7 is connected to the output terminal of ADC conversion circuit 6, and is used to receive digital signals, process data to obtain the average value, maximum value and minimum value of digital signals; MCU module 7 is connected to wireless transmission module 8, and is used to transmit the data processed by MCU module 7 to an external host computer, and send the control commands of the external host computer to MCU module 7.

[0048] The power control output terminal of MCU module 7 is connected to the power control input terminal of programmable constant voltage source 1. After receiving the power control command, programmable constant voltage source 1 starts or stops. The resistance adjustment signal output terminal of MCU module 7 is connected to the resistance control terminal of electronic adjustable potentiometer 9. After receiving the resistance adjustment command, electronic adjustable potentiometer 9 adjusts to the corresponding resistance value to adjust the output voltage of programmable constant voltage source 1. The feedback terminal of electronic adjustable potentiometer 9 is connected to the inverting input terminal of amplifier 5. Amplifier 5 is used to adjust the gain according to the resistance value of electronic adjustable potentiometer 9. The gating signal output terminal of MCU module 7 is connected to the control terminals of the first analog switch 3 and the second analog switch 4 respectively. After receiving the gating control command, the first analog switch 3 and the second analog switch 4 perform the same switching connection on the multiple strain gauge single-arm bridges in the strain gauge resistor network 10. The same switching connection means that after receiving the selection control command, the first analog switch 3 and the second analog switch 4 switch the connection to the same strain gauge single-arm bridge in the strain gauge resistor network 10.

[0049] In this embodiment, the strain gauge resistor network 10 includes a balancing resistor unit and a strain gauge unit. The balancing resistor unit includes N balancing resistors 11 and N Zener diodes 12, and the strain gauge unit includes N strain gauges 13.

[0050] One end of the i-th balancing resistor 11 in the balancing resistor unit is connected to one end of the corresponding i-th strain gauge 13 in the strain gauge unit to form the i-th strain gauge single-arm bridge of the strain gauge resistor network 10. The i-th strain gauge single-arm bridge is connected to the i-th branch pin of the second analog switch 4 through a signal line at the node where the balancing resistor 11 and the strain gauge 13 are connected. The other end of the i-th balancing resistor 11 in the balancing resistor unit is connected to the positive terminal of the i-th Zener diode 12. The negative terminal of the i-th Zener diode 12, the other end of the i-th strain gauge 13, and the i-th branch pin of the first analog switch 3 are all connected. The positive terminals of the N Zener diodes 12 are all connected to the low potential terminal of the programmable voltage source.

[0051] Among them, the programmable constant voltage source 1 provides excitation to the strain gauge resistor network 10 through the current limiting resistor 2 and the first analog switch 3, and the Zener diode 12 can make the excitation of the strain gauge resistor network 10 a constant voltage excitation.

[0052] In this embodiment, the wireless transmission module 8 is a low-power Bluetooth module; the first analog switch 3 and the second analog switch 4 are both single or multiple low on-resistance double-pole four-throw analog switches; the double-pole four-throw analog switches use a circuit based on the CH444G chip; the MCU module 7 uses a circuit based on the STC8A8K64D4 chip; the amplifier 5 is a differential amplifier; the Zener diode 12 is a 1.8V Zener diode 12, and the programmable constant voltage source 1 is a 2.5V constant voltage power supply. This strain acquisition controller is powered by a high-capacity disposable lithium battery, which can meet the requirement of continuous online monitoring of the strain of moving objects.

[0053] The strain acquisition controller in this embodiment is small in size and low in power consumption, enabling online monitoring of multiple strain points on a rotating object. Depending on the requirements, this embodiment can also be used for stress detection on bridges, cranes, construction machinery, amusement equipment, etc.

[0054] Example 2

[0055] This embodiment is a control method for a strain acquisition controller, which is implemented using the strain acquisition controller of Embodiment 1.

[0056] Taking the measurement of strain in the circumferential weld of a large drum as an example, when collecting data through the strain acquisition controller, the strain acquisition controller is first installed on the drum body, and the strain gauges 13 are arranged around the circumferential weld of the drum. The strain gauges 13 are perpendicular to the circumferential weld and attached to both sides of the circumferential weld, 1-3 mm away from the boundary of the circumferential weld.

[0057] When the strain acquisition controller acquires data, the control method of the strain acquisition controller in this embodiment includes the following steps:

[0058] S1. The MCU module 7 receives the wake-up command from the external host computer through the wireless transmission module 8, enters the working mode from the power-down mode, and sends a power control command to the programmable constant voltage source 1 to start the programmable constant voltage source 1.

[0059] S2, MCU module 7 sends selection control command to the first analog switch 3 and the second analog switch 4 to control the first analog switch 3 and the second analog switch 4 to select the first strain gauge single-arm bridge. The programmable constant voltage source 1 provides a constant voltage excitation to the first strain gauge single-arm bridge through the current limiting resistor 2 and the corresponding Zener diode 12.

[0060] S3, MCU module 7 outputs resistance adjustment command according to the preset zero adjustment resistance value, and electronic adjustable potentiometer 9 adjusts to the corresponding resistance value after receiving the resistance adjustment command.

[0061] S4. After the circuit stabilizes, the analog signal output from the second analog switch 4 is received by amplifier 5 and amplified. Then, the analog signal output by amplifier 5 is converted into a digital signal by ADC conversion circuit 6.

[0062] S5, MCU module 7 receives the digital signal output by ADC conversion circuit 6, continuously reads and records multiple digital signals, and records the average, maximum and minimum values ​​of the digital signals;

[0063] Specifically, when recording the average, maximum, and minimum values ​​of a digital signal:

[0064] When the ratio between the difference between the maximum and the average, and between the absolute values ​​of the difference between the minimum and the average, exceeds twice, multiple digital signals are re-read and recorded, along with the average, maximum, and minimum values ​​of the digital signals.

[0065] When, in n consecutive records, n≥3, the ratio between the absolute values ​​of the difference between the maximum and the average, and the difference between the minimum and the average, all exceed twice, record the most recent average, maximum, and minimum values.

[0066] S6. The MCU module 7 sends a selection control command to the first analog switch 3 and the second analog switch 4. The first analog switch 3 and the second analog switch 4 select one of the remaining strain gauge single-arm bridges in the strain gauge resistor network 10. Repeat steps S3 to S6 until all N strain gauge single-arm bridges of the strain gauge resistor network 10 have completed one acquisition.

[0067] S7 and MCU module 7 transmit the average, maximum and minimum values ​​of the N-channel strain gauge single-arm bridge of strain gauge resistor network 10 to the external host computer through wireless transmission module 8.

[0068] S8. According to the external host computer control command, the MCU module 7 sends a power control command to the programmable constant voltage source 1 to shut down the programmable constant voltage source 1, and the MCU module 7 enters the power-down mode.

[0069] It should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions described in the above embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A strain acquisition controller, characterized in that, It includes a programmable constant voltage source, current-limiting resistor, strain gauge resistor network, first analog switch, second analog switch, amplifier, ADC conversion circuit, MCU module, wireless transmission module and electronically adjustable potentiometer; The strain gauge resistor network includes N strain gauge single-arm bridges, N≥4, used to convert strain signals into analog signals of resistance changes; The high potential end of the programmable constant voltage source is connected to the common terminal of the first analog switch through a current limiting resistor. The i-th branch pin of the first analog switch is connected to the i-th strain gauge single-arm bridge in the strain gauge resistor network, 1≤i≤N. The i-th branch pin of the second analog switch is connected to the i-th strain gauge single-arm bridge in the strain gauge resistor network, and the non-inverting input terminal of the amplifier is connected to the common terminal of the second analog switch to amplify the analog signal output by the analog switch. The input terminal of the ADC conversion circuit is connected to the output terminal of the amplifier, and is used to convert the analog signal output by the amplifier into a digital signal. The input terminal of the MCU module is connected to the output terminal of the ADC conversion circuit, and is used to receive the digital signal, perform data processing to obtain the average value, maximum value and minimum value of the digital signal; The MCU module communicates with the wireless transmission module to transmit the data processed by the MCU module to an external host computer and to send control commands from the external host computer to the MCU module. The power control output terminal of the MCU module is connected to the power control input terminal of the programmable constant voltage source. After receiving the power control command, the programmable constant voltage source starts or stops. The resistance adjustment signal output terminal of the MCU module is connected to the resistance control terminal of the electronically adjustable potentiometer. After receiving the resistance adjustment command, the electronically adjustable potentiometer adjusts to the corresponding resistance value to adjust the output voltage of the programmable constant voltage source. The feedback terminal of the electronically adjustable potentiometer is connected to the inverting input terminal of the amplifier. The amplifier is used to adjust the gain according to the resistance value of the electronically adjustable potentiometer. The gating signal output terminal of the MCU module is connected to the control terminals of the first analog switch and the second analog switch respectively. After receiving the gating control command, the first analog switch and the second analog switch perform the same switching connection on the multi-channel strain gauge single-arm bridge in the strain gauge resistor network. The strain gauge resistor network includes a balancing resistor unit and a strain gauge unit. The balancing resistor unit includes N balancing resistors and N Zener diodes, and the strain gauge unit includes N strain gauges. One end of the i-th balancing resistor in the balancing resistor unit is connected to one end of the corresponding i-th strain gauge in the strain gauge unit to form the i-th strain gauge single-arm bridge of the strain gauge resistor network. The i-th strain gauge single-arm bridge is connected to the i-th branch pin of the second analog switch through a signal line at the node where the balancing resistor and the strain gauge are connected. In the balancing resistor unit, the other end of the i-th balancing resistor is connected to the positive terminal of the i-th Zener diode, and the negative terminal of the i-th Zener diode, the other end of the i-th strain gauge, and the i-th branch pin of the first analog switch are all connected; the positive terminals of the N Zener diodes are all connected to the low potential terminal of the programmable voltage source.

2. The strain acquisition controller according to claim 1, characterized in that, The wireless transmission module is a low-power Bluetooth module.

3. The strain acquisition controller according to claim 1, characterized in that, Both the first analog switch and the second analog switch are single or multiple low on-resistance double-pole four-throw analog switches.

4. The strain acquisition controller according to claim 1, characterized in that, The amplifier is a differential amplifier.

5. A control method for a strain acquisition controller, characterized in that, The strain acquisition controller described in any one of claims 1 to 4 is used to implement the following steps: S1. The MCU module receives the wake-up command from the external host computer through the wireless transmission module, enters the working mode from the power-down mode, and sends a power control command to the programmable constant voltage source to start the programmable constant voltage source. S2. The MCU module sends a selection control command to the first analog switch and the second analog switch to select the first strain gauge single-arm bridge. The programmable constant voltage source provides a constant voltage excitation to the first strain gauge single-arm bridge through the current limiting resistor. S3. The MCU module outputs a resistance adjustment command according to the preset zero-adjustment resistance value. The electronic adjustable potentiometer receives the resistance adjustment command and adjusts it to the corresponding resistance value. S4. After the circuit stabilizes, the analog signal output from the second analog switch is received by the amplifier and amplified. Then, the analog signal output by the amplifier is converted into a digital signal by the ADC conversion circuit. S5. The MCU module receives the digital signal output by the ADC conversion circuit, continuously reads and records multiple digital signals, and records the average, maximum and minimum values ​​of the digital signals; S6. The MCU module sends a selection control command to the first analog switch and the second analog switch. The first analog switch and the second analog switch select one of the remaining strain gauge single-arm bridges in the strain gauge resistor network. Repeat steps S3 to S6 until all N strain gauge single-arm bridges of the strain gauge resistor network have completed one acquisition. S7. The MCU module transmits the average, maximum, and minimum values ​​of the N-channel strain gauge single-arm bridge of the strain gauge resistor network to an external host computer via a wireless transmission module. S8. According to the external host computer control instructions, the MCU module sends a power control instruction to the programmable constant voltage source to shut down the programmable constant voltage source, and the MCU module enters power-down mode.

6. The control method for the strain acquisition controller according to claim 5, characterized in that, In step S5, when recording the average, maximum, and minimum values ​​of the digital signal: When the ratio between the difference between the maximum and the average, and between the absolute values ​​of the difference between the minimum and the average, exceeds twice, multiple digital signals are re-read and recorded, along with the average, maximum, and minimum values ​​of the digital signals. When, in n consecutive records, n≥3, the ratio between the absolute values ​​of the difference between the maximum and average values, and the difference between the minimum and average values, all exceed twice, record the most recent average, maximum, and minimum values.

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