CN115065275B - A control system for a stable platform of an aerial remote sensing camera - Google Patents

Abstract

The present invention relates to the field of aerial remote sensing imaging technology, and specifically to a control system for an aerial remote sensing camera stabilization platform. To ensure the imaging quality of the camera, it is necessary to correct the camera attitude under the condition of the carrier aircraft attitude change to ensure its stability in the inertial space. The attitude measurement unit senses the three attitude position changes of the aircraft carrier, and the gyroscope senses the inertial space angular rate of the heading axis motor, the pitch axis motor and the roll axis motor; the interface expands the FPGA module to transmit the sensed data to the main controller, complete the closed-loop control algorithm in the main controller and generate the motor drive signal, and complete the driving of the heading axis motor, the pitch axis motor and the roll axis motor through the optical coupling isolation and the motor driver, thereby completing the closed-loop feedback control of the position loop and the speed loop to achieve the inertial space stability of the camera.

Description

A control system for a stable platform of an aerial remote sensing camera

Technical Field

The invention relates to the technical field of aerial remote sensing imaging, and in particular to a control system for an aerial remote sensing camera stabilization platform.

Background Art

During the imaging process, the camera imaging quality will be reduced due to changes in the attitude (yaw, pitch, roll) of the airborne platform. This effect is mainly manifested when the camera is continuously imaging. Changes in the aircraft attitude will cause distortion of the ground imaging strips and produce image shifts in the row and column directions of the TDI CCD detector. For example, changes in the aircraft pitch attitude will produce image shifts in the row direction, changes in the roll attitude will produce image shifts in the column direction, and changes in the yaw attitude will produce image shifts in both the row and column directions. At the same time, changes in the aircraft's roll attitude will also cause the camera to tilt, causing the imaging to deviate from the target area. In the forward image motion compensation process based on the speed-to-height ratio, when the aircraft attitude angle changes, there will be a deviation between the theoretically calculated image motion compensation speed and the actual required image motion compensation speed, and the greater the change in the attitude angle, the greater the image motion compensation deviation, which will lead to a decrease in imaging resolution.

Therefore, the prior art still has defects and needs further development.

Summary of the invention

The embodiment of the present invention provides an aerial remote sensing camera stabilization platform control system to at least solve the problem that when the attitude of the existing aircraft changes, the camera imaging quality decreases, thereby causing the imaging resolution to decrease.

According to one embodiment of the present invention, there is provided an aerial remote sensing camera stabilization platform control system, comprising:

The main controller is connected to the camera controller for communication, receiving control instructions and providing status feedback;

The interface expansion FPGA module is connected to the interface expansion PFGA module, and the interface expansion PFGA module collects data from the encoder, gyro and attitude measurement unit and transmits the data to the main controller; wherein the gyro includes a heading axis gyro, a pitch axis gyro and a roll axis gyro, and the encoder includes a lateral axis encoder, a pitch axis encoder and a roll axis encoder;

A motor driver connected to the main controller, the main controller drives the motor of the aircraft through the motor driver; wherein the motor of the aircraft includes a panning axis motor, a pitch axis motor and a roll axis motor, and each of the panning axis motor, the pitch axis motor and the roll axis motor is equipped with a motor driver;

Hall current sensor, used to detect winding current and monitor bus voltage by resistor voltage division;

An ADC converter is connected to the interface expansion FPGA module and the Hall current sensor, and is used to transmit the current and voltage data detected by the Hall current sensor to the main controller through the interface expansion FPGA module;

The main controller completes the closed-loop control algorithm and generates motor drive signals. The main controller is optically isolated from the motor driver, and the heading axis motor, pitch axis motor and roll axis motor are driven through the optical coupling isolation and the motor driver.

Furthermore, the stable platform control system also includes:

A power conversion unit connected to the camera controller, the camera controller provides a power supply and a signal power supply isolated from each other for the stable platform control system;

The power conversion unit is used to convert the digital power in the signal power into a variety of digital power supplies required for a stable platform control system.

Furthermore, the main controller is connected to the camera controller via an RS-422 interface.

Further, the main controller includes:

A control instruction parsing state feedback module is used to receive control instructions from the camera controller and provide state feedback;

The closed-loop control algorithm module is used to complete the closed-loop control algorithm, including completing the position loop, speed loop and current loop closed-loop control of the panning axis motor, pitch axis motor and roll axis motor respectively;

The XINTF interface is connected to the interface expansion FPGA and is used for data transmission with the interface expansion FPGA.

Furthermore, the closed-loop control algorithm specifically includes:

Set 0.05ms (1/20kHz) as the counting period;

Each time a counting cycle is reached, the interrupt processing is started. In each interrupt, the current closed-loop algorithm is executed once, including reading current data and corrector calculation, and updating the duty cycle;

The speed closed-loop algorithm is executed once every 10 interruptions, including reading speed data and corrector calculation ratio, and updating the current value setting;

The position closed-loop algorithm is executed once every 100 interrupts, including reading position data and corrector calculation, and updating the speed value.

Furthermore, the calculation frequency of the current loop is 20KHz, the calculation frequency of the speed loop is 2KHz, and the calculation frequency of the position loop is 200Hz.

Furthermore, the Hall current sensor transmits the detected current and voltage to an ADC converter through a signal conditioning circuit.

In order to ensure the imaging quality of the camera, the control system of the aerial remote sensing camera stabilization platform in the embodiment of the present invention needs to correct the camera attitude under the condition of the carrier aircraft attitude change to ensure its stability in the inertial space. The attitude measurement unit senses the position changes of the three attitudes (pitch, yaw, and roll) of the aircraft carrier, and the gyroscope senses the inertial space angular rate of the heading axis motor, the pitch axis motor, and the roll axis motor; the interface expands the FPGA module to transmit the sensed data to the main controller, complete the closed-loop control algorithm in the main controller and generate the motor drive signal, and complete the driving of the heading axis motor, the pitch axis motor, and the roll axis motor through the optical coupling isolation and the motor driver, thereby completing the closed-loop feedback control of the position loop and the speed loop to achieve the inertial space stability of the camera.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

FIG1 is a schematic diagram of a control system for an aerial remote sensing camera stabilization platform according to the present invention;

FIG2 is a three-axis platform permanent magnet brushed DC torque motor algorithm execution strategy of the present invention;

FIG3 is a block diagram of a position loop control system in an air stabilization mode of the present invention;

FIG. 4 is a block diagram of a control system of a stable platform in a ground application mode of the present invention.

DETAILED DESCRIPTION

In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described 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 should fall within the scope of protection of the present invention.

It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

According to an embodiment of the present invention, a control system for an aerial remote sensing camera stabilization platform is provided, referring to FIG1 , comprising:

The main controller is connected to the camera controller for communication, receiving control instructions and providing status feedback;

The interface expansion FPGA module is connected to the interface expansion PFGA module, and the interface expansion PFGA module collects data from the encoder, gyro and attitude measurement unit and transmits the data to the main controller; wherein the gyro includes a heading axis gyro, a pitch axis gyro and a roll axis gyro, and the encoder includes a lateral axis encoder, a pitch axis encoder and a roll axis encoder;

A motor driver connected to the main controller, the main controller drives the motor of the aircraft through the motor driver; wherein the motor of the aircraft includes a panning axis motor, a pitch axis motor and a roll axis motor, and each of the panning axis motor, the pitch axis motor and the roll axis motor is equipped with a motor driver;

Hall current sensor, used to detect winding current and monitor bus voltage by resistor voltage division;

An ADC converter is connected to the interface expansion FPGA module and the Hall current sensor, and is used to transmit the current and voltage data detected by the Hall current sensor to the main controller through the interface expansion FPGA module;

The main controller completes the closed-loop control algorithm and generates motor drive signals. The main controller is optically isolated from the motor driver, and the heading axis motor, pitch axis motor and roll axis motor are driven through the optical coupling isolation and the motor driver.

In order to ensure the imaging quality of the camera, the control system of the aerial remote sensing camera stabilization platform in the embodiment of the present invention needs to correct the camera attitude under the condition of the carrier aircraft attitude change to ensure its stability in the inertial space. The attitude measurement unit senses the position changes of the three attitudes (pitch, yaw, and roll) of the aircraft carrier, and the gyroscope senses the inertial space angular rate of the heading axis motor, the pitch axis motor, and the roll axis motor; the interface expands the FPGA module to transmit the sensed data to the main controller, complete the closed-loop control algorithm in the main controller and generate the motor drive signal, and complete the driving of the heading axis motor, the pitch axis motor, and the roll axis motor through the optical coupling isolation and the motor driver, thereby completing the closed-loop feedback control of the position loop and the speed loop to achieve the inertial space stability of the camera.

The present invention relates to the field of aerial remote sensing imaging technology, and in particular to a TDI CCD aerial remote sensing camera stabilization platform control method based on DSP (main controller) and FPGA architecture, which has both an air stabilization mode and a ground stabilization mode, as shown in Figures 3 and 4. The ground stabilization mode simulates the closed-loop control algorithm flow of the air stabilization mode, which brings great convenience to the TDICCD push-broom imaging experiment under laboratory conditions, facilitates the completion of various functional test verifications, and is of great significance for the application of actual engineering projects.

The main controller uses TI's TM320F28335ZJZQ DSP controller. Three pairs of ePWM are used to drive three DC motors respectively; one SCI is responsible for communicating with the camera controller, one SPI interface is responsible for data interaction with E2PROM, and the XINTF interface is responsible for data interaction with the extended FPGA and external extended SRAM.

The interface expansion FPGA uses Xilinx's XC4VLX25, which is responsible for collecting data from three rate gyroscopes, three encoders and the POS system. It also collects data from three winding circuits and bus voltage output by the ADC converter, and sends them to the DSP in real time through the XINTF interface after packaging and sorting.

The functional block diagram of the stable platform control system is shown in Figure 1. The electrical interface between the system and the camera controller is the power supply interface and the RS-422 communication interface. The camera controller provides the stable platform control system with isolated power supply and signal power supply, and multiple power supplies and analog power supplies are converted in the camera controller.

The stable platform control system also includes:

A power conversion unit connected to the camera controller, the camera controller provides a power supply and a signal power supply isolated from each other for the stable platform control system;

The power conversion unit is used to convert the digital power in the signal power into a variety of digital power supplies required for a stable platform control system.

The power conversion unit is responsible for converting the digital power +5V in the signal power supply into a variety of digital power supplies for system control. The main controller is responsible for communicating with the camera controller through the RS-422 interface, receiving control instructions and providing status feedback.

The main controller includes:

A control instruction parsing state feedback module is used to receive control instructions from the camera controller and provide state feedback;

The closed-loop control algorithm module is used to complete the closed-loop control algorithm, including completing the position loop, speed loop and current loop closed-loop control of the panning axis motor, pitch axis motor and roll axis motor respectively;

The XINTF interface is connected to the interface expansion FPGA and is used for data transmission with the interface expansion FPGA.

The interface expansion FPGA module collects data from the encoders, gyroscopes and POS attitude measurement systems of each axis, and transmits it to the DSP through the XINTF interface. The winding current is detected by the Hall current sensor and the bus voltage is monitored by the resistor voltage divider. The current and voltage data converted by the ADC are also transmitted to the DSP through the FPGA. The closed-loop control algorithm is completed inside the main controller DSP and the motor drive PWM signal is generated. The drive of the motors of each axis is completed through optocoupler isolation and the motor driver.

The closed-loop control algorithm specifically includes:

Set 0.05ms (1/20kHz) as the counting period;

Each time a counting cycle is reached, the interrupt processing is started. In each interrupt, the current closed-loop algorithm is executed once, including reading current data and corrector calculation, and updating the duty cycle;

The speed closed-loop algorithm is executed once every 10 interruptions, including reading speed data and corrector calculation ratio, and updating the current value setting;

The position closed-loop algorithm is executed once every 100 interrupts, including reading position data and corrector calculation, and updating the speed value.

The main controller needs to complete the three closed-loop control of the position loop, speed loop and current loop of the three motors (the panning axis motor, the pitch axis motor and the roll axis motor). The PWM frequency is 20kHz, so the calculation frequency of the current loop is usually 20kHz. According to the calculation of 1/10, the calculation frequency of the speed loop is 2kHz, and the calculation frequency of the position loop is 200Hz.

For the main controller implementation, its implementation timing diagram is shown in Figure 2. A counter with a period of 0.05ms (1/20kHz) is turned on. Each time the counting cycle is reached, interrupt processing is entered. The current closed-loop algorithm is executed once in each interrupt, including reading current data and corrector calculations, and updating the duty cycle; the speed closed-loop algorithm is executed once every 10 interrupts, including reading speed data and corrector calculations, and updating the current value setting; the position closed-loop algorithm is executed once every 100 interrupts, including reading position data and corrector calculations, and updating the speed value setting.

In the air stabilization mode shown in FIG3 , the position data is given by the attitude measurement unit; in the ground stabilization mode shown in FIG4 , the position data is given by the encoder.

Compared with the traditional inertial stabilization platform, the special feature of the present invention is that on the basis of satisfying the air stabilization mode, it also realizes the ground stabilization mode, which helps to better complete the TDI CCD camera ground push-broom imaging test in the laboratory environment, bringing great convenience to the ground imaging test.

The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims (7)

1. An aerial remote sensing camera stabilized platform control system, comprising:

the main controller is in communication connection with the camera controller, receives the control instruction and performs state feedback;

The interface expansion FPGA module is connected with an encoder, a gyroscope and a gesture measurement unit, and the interface expansion FPGA module collects data from the encoder, the gyroscope and the gesture measurement unit and transmits the data to the main controller; the gyro comprises a course axis gyro, a pitch axis gyro and a roll axis gyro, and the encoder comprises a course transverse axis encoder, a pitch axis encoder and a roll axis encoder;

The motor driver is connected with the main controller, and the main controller drives a motor of the aircraft through the motor driver; the motor of the airplane comprises a course shaft motor, a pitching shaft motor and a rolling shaft motor, wherein the course shaft motor, the pitching shaft motor and the rolling shaft motor are respectively provided with one motor driver;

The Hall current sensor is used for detecting winding current and monitoring bus voltage in a resistor voltage division mode;

The ADC is connected with the interface expansion FPGA module and the Hall current sensor and is used for transmitting current and voltage data detected by the Hall current sensor to the main controller through the interface expansion FPGA module;

The main controller completes a closed-loop control algorithm and generates motor driving signals, the main controller is isolated from the motor driver by an optical coupler, and the motor driver drives the course shaft motor, the pitch shaft motor and the roll shaft motor through the optical coupler isolation.

2. The aerial remote sensing camera stabilized platform control system of claim 1, further comprising:

The power conversion unit is connected with the camera controller, and the camera controller provides a power supply and a signal power supply which are isolated from each other for the stable platform control system;

The power supply conversion unit is used for converting digital power supply in the signal power supply into various digital power supplies required by the stable platform control system.

3. The aerial remote sensing camera stabilization platform control system of claim 2, wherein the master controller is connected with the camera controller through an RS-422 interface.

4. The aerial remote sensing camera stabilized platform control system of claim 3, wherein the master controller includes:

The control instruction analysis state feedback module is used for receiving the control instruction of the camera controller and carrying out state feedback;

The closed-loop control algorithm module is used for completing a closed-loop control algorithm and comprises the completion of closed-loop control of a position loop, a speed loop and a current loop of each of the course shaft motor, the pitch shaft motor and the roll shaft motor;

XINTF interface, connected with the interface expansion FPGA, for data transmission with the interface expansion FPGA.

5. The aerial remote sensing camera stabilized platform control system of claim 4, wherein the closed-loop control algorithm specifically comprises:

Setting 0.05ms as a counting period;

The interrupt processing is carried out when each counting period is up, and a current closed loop algorithm is executed once in each interrupt, wherein the current closed loop algorithm comprises the steps of reading current data and calculating by a corrector, and updating the duty ratio;

executing a speed closed loop algorithm once every 10 interrupts, including reading speed data and calculating a ratio by a corrector, and updating a current value given;

The position closed loop algorithm is executed once every 100 interrupts, including reading the position data and corrector calculations, updating the speed value set.

6. The aerial remote sensing camera stabilized platform control system of claim 5, wherein the calculated frequencies of the current loops are 20KHz, the calculated frequencies of the speed loops are 2KHz, and the calculated frequencies of the position loops are 200Hz.

7. The aerial remote sensing camera stabilized platform control system of claim 6, wherein the hall current sensor transmits the detected current and voltage to the ADC converter via a signal conditioning circuit.