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CN111007778A - Dual-redundancy detection and control system for unmanned aerial vehicle - Google Patents

Dual-redundancy detection and control system for unmanned aerial vehicle Download PDF

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Publication number
CN111007778A
CN111007778A CN201911347867.3A CN201911347867A CN111007778A CN 111007778 A CN111007778 A CN 111007778A CN 201911347867 A CN201911347867 A CN 201911347867A CN 111007778 A CN111007778 A CN 111007778A
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China
Prior art keywords
module
detection module
detection
signal
signal processing
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CN201911347867.3A
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Chinese (zh)
Inventor
王晴
张琪
高冬梅
杨亚强
黄朝丽
张陶鹏
陈涛
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Shaanxi Aerospace Times Navigation Equipment Co ltd
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Shaanxi Aerospace Times Navigation Equipment Co ltd
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Priority to CN201911347867.3A priority Critical patent/CN111007778A/en
Publication of CN111007778A publication Critical patent/CN111007778A/en
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    • GPHYSICS
    • G05CONTROLLING; REGULATING
    • G05BCONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00Programme-control systems
    • G05B19/02Programme-control systems electric
    • G05B19/04Programme control other than numerical control, i.e. in sequence controllers or logic controllers
    • G05B19/042Programme control other than numerical control, i.e. in sequence controllers or logic controllers using digital processors
    • G05B19/0423Input/output
    • GPHYSICS
    • G05CONTROLLING; REGULATING
    • G05BCONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00Program-control systems
    • G05B2219/20Pc systems
    • G05B2219/21Pc I-O input output
    • G05B2219/21137Analog to digital conversion, ADC, DAC

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
  • Steering Control In Accordance With Driving Conditions (AREA)

Abstract

The utility model provides a two redundancy of unmanned aerial vehicle detect and control system, including flying control computer system, steering wheel system and power, it exports control signal to first detection module and second detection module respectively to fly control computer system, through adopting two redundancy systems, when first detection module detects on the steering wheel or main control circuit breaks down, the fault information that second detection module received first detection module makes first detection module outage through control relay switch, it continues to detect and control unmanned aerial vehicle through second detection module to fly control computer system, improve unmanned aerial vehicle's flight safety and reliability, prevent that the incident from taking place.

Description

Dual-redundancy detection and control system for unmanned aerial vehicle
Technical Field
The invention relates to the field of unmanned aerial vehicles, in particular to a dual-redundancy detection and control system for an unmanned aerial vehicle.
Background
Detection and control system are unmanned aerial vehicle flight control system's important component, usually detect the steering wheel system on the unmanned aerial vehicle through detection device, detection device gathers the data on the unmanned aerial vehicle and carries out calculation processing, the flight purpose of unmanned aerial vehicle is controlled to corresponding control algorithm of rethread, but the one set of detection controlgear of installation only on unmanned aerial vehicle now, and this detection controlgear breaks down, then the easy incident that takes place of unmanned aerial vehicle, security and reliability are low.
Disclosure of Invention
In order to overcome the defects of low safety and reliability and easy occurrence of safety accidents in the prior art, the invention provides a safe and reliable dual-redundancy detection and control system for the unmanned aerial vehicle.
The technical scheme of the invention is as follows: an unmanned aerial vehicle dual-redundancy detection and control system comprises a flight control computer system, a steering engine system and a power supply, wherein the flight control computer system is respectively connected with a first detection module and a second detection module, the first detection module is connected with the second detection module, the steering engine is connected with a first Hall position sensor, a second Hall position sensor, a first potentiometer and a second potentiometer, the first detection module is sequentially connected with a first signal processing module and a first driving module, the second detection module is sequentially connected with a second signal processing module and a second driving module, the first detection module is connected with the first potentiometer, the second detection module is connected with the second potentiometer, the first signal processing module is connected with the first Hall position sensor, the second signal processing module is connected with the second Hall position sensor, the steering engine is respectively connected with a first driving module and a second driving module, the first driving module is connected with a first detection module, and the second driving module is connected with a second detection module;
the flight control computer system respectively outputs control signals to a first detection module and a second detection module, the first detection module detects inclination angle data of a steering engine through a first potentiometer, the first detection module outputs PWM control signals and direction signals to a first signal processing module, the first signal processing module detects Hall signals of the steering engine through a first Hall position sensor, processes the Hall signals by combining the PWM control signals and the direction signals, and outputs the PWM control signals to a first driving module, the first driving module isolates, amplifies and drives the steering engine to enable the PWM control signals, and the first detection module detects whether the first detection module fails to the first driving module;
when the second detection module receives the fault detected by the first detection module, the second detection module enables the first detection module to be closed, the second detection module detects the inclination angle data of the steering engine through a second potentiometer, the second detection module outputs a PWM (pulse width modulation) control signal and a direction signal to the second signal processing module, the second signal processing module detects the Hall signal of the steering engine through a second Hall position sensor, processes the Hall signal by combining the PWM control signal and the direction signal and outputs the PWM control signal to the first driving module, the second driving module isolates, amplifies and drives the PWM control signal and detects whether the fault occurs on the second detection module and the second driving module;
the power supply supplies power to the first detection module, the first signal processing module, the first driving module, the second detection module, the second signal processing module and the second driving module respectively.
Preferably, a backup transmission line and a serial port chip are arranged between the first detection module and the second detection module.
Preferably, the steering engines comprise 6.
Preferably, each steering engine control is provided with 1 PWM control signal output line and 2 direction signal output lines between the first detection module and the first signal processing module, and 6 signal lines corresponding to the steering engine are arranged between the first signal processing module and the first driving module.
Preferably, each steering engine control is provided with 1 PWM control signal output line and 2 direction signal output lines between the second detection module and the second signal processing module, and 6 signal lines corresponding to the steering engine are arranged between the second signal processing module and the second driving module.
Preferably, a first analog-to-digital converter is arranged between the first potentiometer and the first detection module.
Preferably, a second analog-to-digital converter is arranged between the second potentiometer and the second detection module.
Preferably, a first current detector is arranged between the first detection module and the first driving module.
Preferably, a second current detector is arranged between the second detection module and the second driving module.
The invention has the beneficial effects that: according to the invention, by adopting the dual-redundancy system, when the first detection module detects that the steering engine or the main control circuit has a fault, the second detection module receives the fault information of the first detection module and controls the relay switch to power off the first detection module, and the flight control computer system continuously detects and controls the unmanned aerial vehicle through the second detection module, so that the flight safety and reliability of the unmanned aerial vehicle are improved, and safety accidents are prevented.
Drawings
FIG. 1 is a block diagram of the circuit of the present invention;
fig. 2 is a circuit diagram of an implementation.
Detailed Description
In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.
The invention has the technical scheme that the dual-redundancy detection and control system of the unmanned aerial vehicle comprises a flight control computer system, a steering engine and a power supply, wherein the flight control computer system is respectively connected with a first detection module and a second detection module, the first detection module is connected with the second detection module, the steering engine is connected with a first Hall position sensor, a second Hall position sensor, a first potentiometer and a second potentiometer, the steering engine comprises a motor, a first coil winding and a second coil winding are arranged on the motor, the first Hall position sensor and the second Hall position sensor are respectively used for detecting the current position of the motor, the first potentiometer and the second potentiometer are used for detecting the inclination angle of the steering engine, the first detection module is sequentially connected with a first signal processing module and a first driving module, the second detection module is sequentially connected with a second signal processing module and a second driving module, the first detection module is connected with the first potentiometer, the second detection module is connected with the second potentiometer, the first signal processing module is connected with the first Hall position sensor, the second signal processing module is connected with the second Hall position sensor, the steering engine is respectively connected with the first driving module and the second driving module, the first driving module is connected with the first detection module, and the second driving module is connected with the second detection module;
the flight control computer system respectively outputs control signals to a first detection module and a second detection module, under the condition that the steering engine is not driven, quiescent current exists on the steering engine, the first detection module detects inclination angle data of the steering engine through a first potentiometer, the first detection module outputs PWM (pulse width modulation) control signals and direction signals to a first signal processing module, the first signal processing module detects Hall signals of the steering engine through a first Hall position sensor and processes the Hall signals in combination with the PWM control signals and the direction signals and outputs the PWM control signals to a first driving module, the first driving module isolates, amplifies and drives the PWM control signals to drive the steering engine, and the first detection module detects whether the output end of the first detection module to the output end of the first driving module fails;
when the second detection module receives the fault detected by the first detection module, the second detection module controls the relay switch to cut off the power of the first detection module, the second detection module detects the inclination angle data of the steering engine through the second potentiometer, the second detection module outputs a PWM control signal and a direction signal to the second signal processing module, the second signal processing module detects the Hall signal of the steering engine through the second Hall position sensor and processes the Hall signal by combining the PWM control signal and the direction signal, and outputs the PWM control signal to the second driving module, the second driving module isolates, amplifies and drives the PWM control signal, and the second detection module detects whether the fault occurs from the output end of the second detection module to the output end of the second driving module;
the power supply respectively supplies power to the first detection module, the first signal processing module, the first driving module, the second detection module, the second signal processing module and the second driving module.
Be equipped with backup transmission line and serial ports chip between first detection module and second detection module, first detection module passes through the serial ports with the data of gathering and transmits to second detection module, prevents the main entrance trouble, leads to data loss, influences unmanned aerial vehicle flight safety.
The steering engine on general unmanned aerial vehicle includes 6.
Each steering engine control is equipped with 1 PWM control signal output line and 2 direction signal output lines between first detection module and first signal processing module, and 2 direction signal output lines control steering engine rotation direction are equipped with 6 signal lines corresponding with the steering engine between first signal processing module and first drive module.
Each steering engine control is provided with 1 PWM control signal output line and 2 direction signal output lines between the second detection module and the second signal processing module, the 2 direction signal output lines control the rotation direction of the steering engine, and 6 signal lines corresponding to the steering engine are arranged between the second signal processing module and the second driving module.
A first analog-to-digital converter is arranged between the first potentiometer and the first detection module.
And a second analog-to-digital converter is arranged between the second potentiometer and the second detection module.
A first current detector is arranged between the first detection module and the first driving module.
And a second current detector is arranged between the second detection module and the second driving module.
The first embodiment is as follows: as shown in fig. 2, the first detection module and the second detection module respectively adopt a DSP processor, the model of the DSP processor is TMS320F2812, the first signal processing module and the second signal processing module respectively adopt CPLDs, the first driving module and the second driving module respectively adopt driving circuits, the driving circuits include IR driving chips, magnetic coupling isolators and field effect transistors, the model of the IR driving chips is IRs2334, the number of the steering engines is 6, and each steering engine is connected with a first hall position sensor, a second hall position sensor, a first potentiometer and a second potentiometer;
the flight control computer system respectively sends control signals to a first DSP processor and a second DSP processor through RS422 interfaces, the first DSP processor starts to collect data on a first potentiometer after receiving the control signals, the second DSP processor and a subsequent circuit are in a hot backup state, the first potentiometer on each steering engine transmits the inclination angle data of the corresponding steering engine to the first DSP processor through voltage signals, the first DSP processor converts the voltage signals into angle values through an analog-digital converter for judgment, when the first DSP processor detects that 50 periodic angle values are continuously larger than +/-50 degrees through the first potentiometer, the inclination angle of the steering engine is judged to exceed a normal range or the first potentiometer is in fault, at the moment, the second DSP processor detects fault information sent by the first DSP processor, and then the power supply of the first DSP processor is cut off through a control relay switch to switch detection circuits, when the first DSP processor does not detect the fault, the first DSP processor transmits a PWM control signal and a direction signal to the first CPLD, the first CPLD acquires the current position information of the motor on each steering engine through the first Hall sensor on each steering engine, when the first CPLD continuously receives the state of all 1 in 50 periods, the first Hall sensor is judged to have the fault, the second DSP processor receives the fault information detected by the first DSP processor at the moment, the power supply of the first DSP processor is cut off through a control relay switch to switch a detection circuit, and the first DSP processor does not detect the fault, the first CPLD carries out logic control by combining the Hall signal with the PWM control signal and the direction signal, the first CPLD outputs the PWM control signal through 6 signal lines corresponding to the control of each steering engine, the first magnetic coupling isolator on the first driving circuit isolates and outputs the PWM control signal, the first IR driving chip drives the field effect tube to control each steering engine to rotate according to a certain sequence according to the isolated PWM control signal, the output end of the first driving circuit converts a current signal into a voltage signal through the first current detector and transmits the voltage signal to the first DSP processor, the first DSP processor detects the voltage signal to judge whether the first driving circuit breaks down, the second DSP processor detects fault information sent by the first DSP processor at the moment, and then the power supply of the first DSP processor is cut off through the control relay switch to switch the detection circuit.
When the first DSP processor detects a fault and the second DSP processor receives a fault signal generated by the first DSP processor through a serial port chip, the second DSP processor cuts off the power supply of the first DSP processor through a control relay switch, the second DSP processor continues the first DSP processor and subsequent circuits to start working, each steering engine is controlled to reset, a second potentiometer on each steering engine transmits the inclination angle data detected by the potentiometer to the second DSP processor through a voltage signal, the second DSP processor converts the voltage signal into an angle value through a second analog-to-digital converter for judgment, if the second DSP processor does not detect the fault, the second DSP processor transmits a PWM control signal and a direction signal to a second CPLD, the second CPLD acquires the current position information of the motor on each steering engine through a second Hall sensor on each steering engine, and if the second DSP processor does not detect the fault, the second CPLD performs logic control on the Hall signal by combining the PWM control signal and the direction signal, outputs the PWM control signal through 6 signal lines corresponding to the control of each steering engine, the second magnetic coupling isolator on the second driving circuit isolates and outputs the PWM control signal, the second IR driving chip drives the field effect tube to control each steering engine to rotate according to a certain sequence according to the isolated PWM control signal, the output end of the second driving circuit converts the current signal into a voltage signal through the second current detector and transmits the voltage signal to the second DSP processor, and the second DSP processor detects the voltage signal to judge whether the second driving circuit has a fault.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.

Claims (9)

1. The utility model provides a two redundancy detection of unmanned aerial vehicle and control system, includes flight control computer system, steering wheel system and power, its characterized in that: the flight control computer system is respectively connected with a first detection module and a second detection module, the first detection module is connected with the second detection module, the steering engine is connected with a first Hall position sensor, a second Hall position sensor, a first potentiometer and a second potentiometer, the first detection module is sequentially connected with a first signal processing module and a first driving module, the second detection module is sequentially connected with a second signal processing module and a second driving module, the first detection module is connected with the first potentiometer, the second detection module is connected with the second potentiometer, the first signal processing module is connected with the first Hall position sensor, the second signal processing module is connected with the second Hall position sensor, the steering engine is respectively connected with the first driving module and the second driving module, the first driving module is connected with the first detection module, the second driving module is connected with the second detection module;
the flight control computer system respectively outputs control signals to a first detection module and a second detection module, the first detection module detects inclination angle data of a steering engine through a first potentiometer, the first detection module outputs PWM control signals and direction signals to a first signal processing module, the first signal processing module detects Hall signals of the steering engine through a first Hall position sensor, processes the Hall signals by combining the PWM control signals and the direction signals, and outputs the PWM control signals to a first driving module, the first driving module isolates, amplifies and drives the steering engine to drive the PWM control signals, and the first detection module detects whether the first detection module and the first driving module fail;
when the second detection module receives the fault detected by the first detection module, the second detection module enables the first detection module to be closed, the second detection module detects the inclination angle data of the steering engine through a second potentiometer, the second detection module outputs a PWM (pulse width modulation) control signal and a direction signal to the second signal processing module, the second signal processing module detects the Hall signal of the steering engine through a second Hall position sensor, processes the Hall signal by combining the PWM control signal and the direction signal and outputs the PWM control signal to the second driving module, the second driving module isolates, amplifies and drives the PWM control signal and detects whether the second detection module and the second driving module have faults or not;
the power supply supplies power to the first detection module, the first signal processing module, the first driving module, the second detection module, the second signal processing module and the second driving module respectively.
2. The dual-redundancy detection and control system of an unmanned aerial vehicle of claim 1, wherein: and a backup transmission line and a serial port chip are arranged between the first detection module and the second detection module.
3. The dual-redundancy detection and control system of an unmanned aerial vehicle of claim 1, wherein: the steering wheel includes 6.
4. The dual-redundancy detection and control system of an unmanned aerial vehicle of claim 3, wherein: each steering engine control is equipped with 1 PWM control signal output line and 2 direction signal output lines between first detection module and first signal processing module, is equipped with 6 signal lines corresponding with the steering engine between first signal processing module and first drive module.
5. The dual-redundancy detection and control system of an unmanned aerial vehicle of claim 3, wherein: each steering engine control is equipped with 1 PWM control signal output line and 2 direction signal output lines between second detection module and second signal processing module, is equipped with 6 signal lines corresponding with the steering engine between second signal processing module and second drive module.
6. The dual-redundancy detection and control system of an unmanned aerial vehicle of claim 1, wherein: and a first analog-to-digital converter is arranged between the first potentiometer and the first detection module.
7. The dual-redundancy detection and control system of an unmanned aerial vehicle of claim 1, wherein: and a second analog-to-digital converter is arranged between the second potentiometer and the second detection module.
8. The dual-redundancy detection and control system of an unmanned aerial vehicle of claim 1, wherein: and a first current detector is arranged between the first detection module and the first driving module.
9. The dual-redundancy detection and control system of an unmanned aerial vehicle of claim 1, wherein: and a second current detector is arranged between the second detection module and the second driving module.
CN201911347867.3A 2019-12-24 2019-12-24 Dual-redundancy detection and control system for unmanned aerial vehicle Pending CN111007778A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116224761A (en) * 2023-04-19 2023-06-06 四川傲势科技有限公司 Flight control method, unmanned aerial vehicle, terminal equipment and medium
CN116360477A (en) * 2021-12-28 2023-06-30 北京三快在线科技有限公司 Unmanned aerial vehicle control method and small unmanned aerial vehicle
CN119828745A (en) * 2024-12-27 2025-04-15 紫光计算机科技有限公司 Unmanned aerial vehicle double-flight control system and method based on emergency treatment

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102700706A (en) * 2012-05-31 2012-10-03 西北工业大学 Dual-redundancy actuator system and control method
CN104590550A (en) * 2013-10-30 2015-05-06 北京精密机电控制设备研究所 Highly reliable dual redundancy electric steering gear control device
CN105223870A (en) * 2015-10-12 2016-01-06 西南石油大学 A kind of electric steering engine control system based on DSP and CPLD
CN206807331U (en) * 2017-06-20 2017-12-26 四川建筑职业技术学院 A kind of helm control circuit for multichannel brushless electric machine

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102700706A (en) * 2012-05-31 2012-10-03 西北工业大学 Dual-redundancy actuator system and control method
CN104590550A (en) * 2013-10-30 2015-05-06 北京精密机电控制设备研究所 Highly reliable dual redundancy electric steering gear control device
CN105223870A (en) * 2015-10-12 2016-01-06 西南石油大学 A kind of electric steering engine control system based on DSP and CPLD
CN206807331U (en) * 2017-06-20 2017-12-26 四川建筑职业技术学院 A kind of helm control circuit for multichannel brushless electric machine

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
应浩 等: "一种多通道电气双余度的无人直升机舵系统", 《兵工自动化》 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116360477A (en) * 2021-12-28 2023-06-30 北京三快在线科技有限公司 Unmanned aerial vehicle control method and small unmanned aerial vehicle
CN116224761A (en) * 2023-04-19 2023-06-06 四川傲势科技有限公司 Flight control method, unmanned aerial vehicle, terminal equipment and medium
CN119828745A (en) * 2024-12-27 2025-04-15 紫光计算机科技有限公司 Unmanned aerial vehicle double-flight control system and method based on emergency treatment

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Application publication date: 20200414