IMU-free attitude adjustment method and system for UAV gimbals

Abstract

This invention discloses an IMU-free attitude adjustment method and system for UAV gimbals. The method includes: the gimbal controls its attitude via several servo motors, each servo motor's output shaft is equipped with an angle encoder; the range A of the UAV's attitude angle is acquired, the encoder value B corresponding to range A is acquired, and a conversion relationship between encoder value B and the UAV's attitude angle is established; during flight, the gimbal establishes communication with the UAV, acquires the change in the UAV's attitude angle in real time, converts it into the change in the corresponding encoder value according to the conversion relationship, and the servo motors adjust the gimbal attitude based on the acquired encoder value change. This invention, an IMU-free attitude adjustment method and system for UAV gimbals, eliminates the need for electronic stabilization devices, achieves gimbal stabilization by controlling the relative position of the gimbal and the UAV, and addresses the mismatch between encoder data and attitude data through normalization and analogy.

Description

Technical Field

[0001] This invention relates to the field of motion control, and more specifically to an IMU-free attitude adjustment method and system for use in UAV gimbals. Background Technology

[0002] In current drone gimbal control technology, an IMU (Inertial Measurement Unit), also known as an electronic stabilization device, is added to the gimbal. First, the attitude control of the gimbal itself is combined with the movement of the drone to perform fused attitude control.

[0003] In existing technologies, gimbals can achieve spontaneous attitude adjustment by using an electronic stabilization device (IMU) alone, but the addition of an IMU increases the cost of the gimbal itself.

[0004] The attitude calculation of the IMU itself requires a lot of CPU resources, so a relatively powerful MCU is needed to control it, resulting in more resource consumption.

[0005] The movement of the drone gimbal is strongly correlated with the movement of the drone. Therefore, as long as it can be coupled and synchronized with the movement of the drone, a lot of performance and resource waste can be reduced. Thus, adding a separate IMU to the gimbal does not have a high actual utilization rate.

[0006] Chinese invention patent ZL 201611245415.0 relates to the field of aircraft, such as... Figure 1 As shown, a gimbal stabilization system is disclosed, disposed within a gimbal, comprising: a mechanical stabilization device and an electronic stabilization device; the mechanical and electronic stabilization devices are electrically connected to the same set of vibration sensors, which are fixed within the gimbal; the mechanical stabilization device, based on the output signal of the vibration sensors, controls the gimbal to perform mechanical movements opposite to the detected vibration direction via an electronically controlled mechanical structure to counteract gimbal jitter, thereby achieving mechanical stabilization; the mechanical stabilization device outputs residual jitter data after mechanical stabilization to the electronic stabilization device; the electronic stabilization device, based on the residual jitter data and the output signal of the vibration sensors, performs image processing on the image captured by the gimbal's camera to eliminate various types of image jitter, thereby achieving two-stage stabilization. Only a fraction of a pixel needs to be cropped from the image to achieve a highly stable image.

[0007] The design flaws of the above-mentioned patented system are:

[0008] 1. The aircraft's resources were not used rationally, and the cost of the gimbal was too high due to the addition of electronic stabilization hardware;

[0009] 2. The CPU needs to control the gimbal and perform calculations for the electronic stabilization device, which is too costly. Summary of the Invention

[0010] To address the shortcomings of existing technologies, this invention provides an IMU-free attitude adjustment method and system for UAV gimbals. This method is suitable for attitude control of UAV gimbals, reduces the need for the electronic stabilization device (IMU) in the gimbal itself, and solves the gimbal attitude control problem solely through interaction with the UAV, thereby achieving cost reduction and efficiency improvement.

[0011] To achieve the above objectives, the present invention provides the following technical solution:

[0012] An IMU-free attitude adjustment method for use in UAV gimbals includes the following steps:

[0013] The gimbal is controlled by several servo motors, and an angle encoder is installed on the output shaft of each servo motor.

[0014] Obtain the range A of the UAV attitude angle, obtain the encoder value B of the angle encoder corresponding to the range A, and establish the conversion relationship between the encoder value B and the UAV attitude angle.

[0015] During flight, the gimbal establishes communication with the drone to obtain the changes in the drone's attitude angle in real time. Based on the conversion relationship, these changes are converted into changes in the corresponding encoder values. The servo motors then adjust the gimbal attitude according to the obtained encoder value changes.

[0016] As a further embodiment of the method of the present invention, the gimbal is controlled by rotating the output shafts in three mutually perpendicular directions via three servo motors to control the gimbal's attitude.

[0017] As a further embodiment of the method of the present invention, the conversion relationship includes a numerical relationship and a directional relationship, wherein the encoder adjustment direction is opposite to the direction of change of the UAV attitude angle.

[0018] As a further embodiment of the method of the present invention, before flight, both the drone and the gimbal are in the neutral position, the angle encoder value is in the neutral position of 0, and the drone attitude angle is in the neutral position of 0 degrees.

[0019] An IMU-free attitude adjustment system for use in UAV gimbals includes:

[0020] An angle encoder is provided; the gimbal is controlled by several servo motors, and the angle encoder is installed on the output shaft of each servo motor.

[0021] The normalization module is connected to the UAV control system and the angle encoder. It is used to obtain the range A of the UAV attitude angle, obtain the encoder value B corresponding to the range A of the angle encoder, and establish the conversion relationship between the encoder value B and the UAV attitude angle.

[0022] The attitude adjustment module, connected to the angle encoder and the normalization module, is used to acquire the change in the attitude angle of the UAV in real time during flight, convert it into the change in the corresponding encoder value according to the conversion relationship, and the servo motor adjusts the gimbal attitude according to the obtained change in the encoder value.

[0023] By adopting the above technical solution, the present invention has the following beneficial effects:

[0024] 1. The use of IMU hardware was reduced, thus achieving the goal of cost reduction;

[0025] 2. The attitude control purpose is achieved without calculating the attitude, thus freeing up the CPU load;

[0026] 3. The encoder and flight attitude were homogenized using normalization and analogy methods;

[0027] 4. Adjust the gimbal attitude by maintaining a spatial relative position with the drone. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A block diagram of a gimbal stabilization system based on existing technology.

[0030] Figure 2 This is a block diagram of an IMU-less attitude adjustment system applied to a drone gimbal, according to an embodiment of the present invention.

[0031] Figure 3 This is a flowchart illustrating an IMU-free attitude adjustment method for a drone gimbal, according to an embodiment of the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0033] A drone gimbal is a support device used by drones to mount and fix payloads such as cameras. The gimbal control system primarily studies and develops a dedicated gimbal control system using a microcontroller as the main control chip, combined with various sensors and actuators. The control functions of the gimbal control system mainly include two aspects: first, realizing the gimbal's self-stabilization function, also known as image stabilization; and second, controlling the gimbal's rotation in space. If the controlled object has controllable components, such as camera shooting and aperture adjustment, the control system should also have corresponding control functions for those components.

[0034] A pan-tilt head (PTZ) is a mounting platform composed of two AC motors, capable of horizontal and vertical movement. However, it's important to distinguish it from the concept of a pan-tilt head in photographic equipment. A photographic PTN is generally just a tripod, with its orientation adjusted manually; while a monitoring system PTN allows for remote control of its rotation and movement via a control system. The rotation speed of a PTN is an important indicator of its quality. Since the horizontal and vertical directions are driven by two different motors, the rotation speed is divided into horizontal and vertical speeds. Due to load requirements, the vertical motor has greater torque during startup and operation than the horizontal motor. Furthermore, in actual monitoring, the required horizontal speed is higher than the vertical speed. Therefore, generally speaking, the vertical speed of a PTN is lower than its horizontal speed.

[0035] In this embodiment, the gimbal controls its attitude by rotating its output axes in three mutually perpendicular directions using three servo motors. These correspond to the three directions of rotation of the drone. During flight, the drone can rotate around the Pitch, Yaw, and Roll axes. Pitch is obtained by rotating around the X-axis and is called the pitch angle; Yaw is rotated around the Y-axis and is called the yaw angle; and Roll is rotated around the Z-axis and is called the roll angle. In this embodiment, the gimbal is mounted on the drone, and the two establish communication. The output axes of the three servo motors of the gimbal are in the same direction as the drone's Pitch, Yaw, and Roll axes, respectively. The gimbal controls its attitude through several servo motors, and each servo motor's output axis is equipped with an angle encoder. An angle encoder is a device that measures angular displacement using digital line technology such as gratings or binary lines (also called an angle encoder).

[0036] This invention provides an IMU-free attitude adjustment method for UAV gimbals, which mainly includes the following steps:

[0037] Step 1: The gimbal is controlled by several servo motors, and an angle encoder is installed on the output shaft of each servo motor;

[0038] Step 2: Obtain the range A of the UAV attitude angle, obtain the encoder value B corresponding to the range A of the angle encoder, and establish the conversion relationship between the encoder value B and the UAV attitude angle.

[0039] Assuming the drone's attitude angle range A is 360 degrees, and the corresponding encoder range for 360 degrees is 32768, then the encoder value for 1 degree of attitude angle is 32768 / 360 = 91. If the required control precision is 0.1 degrees, then the encoder value for 0.1 degrees of attitude angle is 32768 / 3600 = 9.1 ≈ 9. Therefore, 0.1 degrees normalized to an encoder value of 9. That is, every 0.1 degree change in the drone's attitude angle is equivalent to a 9-degree change in the encoder value. It's important to note that gimbal stabilization refers to the gimbal automatically moving in the opposite direction when the drone's attitude angle changes, thus offsetting the impact of the drone's attitude change on the gimbal. Therefore, the conversion relationship in this step includes not only numerical relationships but also directional relationships; that is, the direction of encoder value change is opposite to the direction of drone attitude angle change. For example, if the drone's attitude angle is rotating upwards, the encoder changes downwards; if the drone's attitude angle is rotating to the left, the encoder changes to the right.

[0040] Step 3: During flight, the gimbal establishes communication with the drone to obtain the changes in the drone's attitude angle in real time. Based on the conversion relationship, these changes are converted into the corresponding encoder values. The servo motors then adjust the gimbal attitude according to the obtained encoder values.

[0041] Before flight, both the drone and the gimbal are in the neutral position, with the angle encoder value at 0 and the drone's attitude angle at 0 degrees. When the drone performs maneuvers, the attitude data changes. At this time, the gimbal calculates based on the drone's attitude data. For example, if the drone's pitch changes from 0 to 20 degrees (the gimbal is pointing downwards), the gimbal pitch should move 20 degrees in the opposite direction. By calculating the normalized value, the required encoder rotation value is determined, and the motor rotation is controlled to achieve the purpose of stabilization.

[0042] This invention also provides an IMU-free attitude adjustment system for use in UAV gimbals, used to implement the aforementioned IMU-free attitude adjustment method for use in UAV gimbals. The system includes:

[0043] Angle encoder: The gimbal is controlled by several servo motors, and an angle encoder is set on the output shaft of each servo motor.

[0044] The normalization module is connected to the UAV control system and the angle encoder. It is used to obtain the range A of the UAV attitude angle, obtain the encoder value B corresponding to the range A of the angle encoder, and establish the conversion relationship between the encoder value B and the UAV attitude angle.

[0045] The attitude adjustment module, connected to the angle encoder and normalization module, is used to acquire the change in the attitude angle of the UAV in real time during flight, convert it into the change in the corresponding encoder value according to the conversion relationship, and the servo motor adjusts the gimbal attitude according to the obtained change in the encoder value.

[0046] Cooperate Figure 2 and Figure 3 As shown, taking the Pitch axis as an example, this invention is used to explain the IMU-free attitude adjustment method of UAV gimbal. Other axes can be described by analogy.

[0047] S1: Power-on initialization;

[0048] S2: Move the Pitch axis of the gimbal downwards to find the limit position and record the Pitch axis encoder value leftPosition;

[0049] S3: Move the Pitch axis of the gimbal upwards to find a fixed position, and record the RightPosition value of the Pitch axis encoder.

[0050] S4: Calculate the MidPosition using leftPosition and rightPosition. MidPosition is the middle position of the Pitch axis.

[0051] S5: The gimbal receives the attitude data of the drone. At this time, the attitude angle of the Pitch axis is 0, so the MidPosition corresponds to the attitude angle of 0.

[0052] S6: If the drone's pitch axis attitude changes, the change amount is PerValue based on the corresponding attitude angle of the encoder, and the change amount of the aircraft attitude is CurrentPose. The gimbal attitude adjustment is calculated as follows: TargetPostion = MidPosition + CurrentPose * PerValue.

[0053] S7: When controlling the gimbal movement independently, the encoder value of the gimbal movement change is converted into the drone attitude value and recorded as the relative angle. When returning to center, the drone can be rotated back to its position based on the angle.

[0054] Specifically, if the system recognizes that the gimbal attitude is being manually adjusted without changing the drone's attitude, after the adjustment is completed, the initial midpoint position OldPosition = MidPosition is saved, and the adjusted position is used as the new midpoint position MidPositon = CurrentPositon (current position).

[0055] This invention relates to an IMU-free attitude adjustment method and system for UAV gimbals. It eliminates the need for electronic stabilization devices in the gimbal and achieves gimbal stabilization by controlling the relative position of the gimbal and the UAV. It also addresses the mismatch between encoder data and attitude data through normalization and analogy.

[0056] Although embodiments of the present invention have been shown and described, these specific embodiments are merely explanations of the invention and are not intended to limit it. The specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. After reading this specification, those skilled in the art may make modifications, substitutions, and variations to the embodiments as needed without departing from the principles and spirit of the invention, but such modifications, substitutions, and variations are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for IMU-free attitude adjustment applied to UAV gimbals, characterized in that, Includes the following steps: The gimbal is controlled by several servo motors, and an angle encoder is installed on the output shaft of each servo motor. Obtain the range A of the UAV attitude angle, obtain the encoder value B of the angle encoder corresponding to the range A, and establish the conversion relationship between the encoder value B and the UAV attitude angle. During flight, the gimbal establishes communication with the drone to obtain the changes in the drone's attitude angle in real time. Based on the conversion relationship, these changes are converted into changes in the corresponding encoder values. The servo motors then adjust the gimbal attitude according to the obtained encoder value changes.

2. The IMU-free attitude adjustment method for UAV gimbals as described in claim 1, characterized in that, The gimbal's attitude is controlled by three servo motors that rotate the output axes in three mutually perpendicular directions.

3. The IMU-free attitude adjustment method for UAV gimbals as described in claim 1, characterized in that, The conversion relationship includes numerical relationship and directional relationship, and the encoder adjustment direction is opposite to the direction of the UAV attitude angle change.

4. The IMU-free attitude adjustment method for UAV gimbals as described in claim 1, characterized in that, Before flight, both the drone and the gimbal were in the neutral position, the angle encoder value was in the neutral position of 0, and the drone attitude angle was in the neutral position of 0 degrees.

5. An IMU-free attitude adjustment system for use in UAV gimbals, characterized in that, include: An angle encoder is provided; the gimbal is controlled by several servo motors, and the angle encoder is installed on the output shaft of each servo motor. The normalization module is connected to the UAV control system and the angle encoder. It is used to obtain the range A of the UAV attitude angle, obtain the encoder value B corresponding to the range A of the angle encoder, and establish the conversion relationship between the encoder value B and the UAV attitude angle. The attitude adjustment module, connected to the angle encoder and the normalization module, is used to acquire the change in the attitude angle of the UAV in real time during flight, convert it into the change in the corresponding encoder value according to the conversion relationship, and the servo motor adjusts the gimbal attitude according to the obtained change in the encoder value.

Images