Feed-forward control method for pan-tilt
By introducing a feedforward control model into traditional PID control and using the angular velocity after IMU decoupling to adjust the motor control quantity, the problems of delay and large computational load in feedback control in UAV motion scenarios are solved, achieving faster and more accurate gimbal control.
Patent Information
- Application Number
- CN202511073967.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-01
- Publication Date
- 2025-11-07
AI Technical Summary
In drone motion scenarios, feedback control technology suffers from problems such as adjustment response delay and large computational load, making it difficult to ensure image stability, especially when tracking high-speed targets.
By introducing feedforward control on the basis of traditional PID control, a feedforward control model is constructed. The angular velocity after IMU decoupling is used as input, superimposed on the output of the angle PID loop, and multiplication and addition operations are performed to adjust the motor control quantity and achieve a faster response.
It improves the response speed and accuracy of gimbal control, reduces latency, broadens application scenarios, and enhances performance in complex environments.
Smart Images
Figure CN120915205A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of gimbal control, in particular to a feedforward control method for gimbal. BACKGROUND
[0002] In the current industry, feedback control is the most widely used mainstream control technology for gimbal. For example, the common PID control algorithm based on position sensor feedback, the position sensor monitors the actual angle of the gimbal in real time, and feeds back the information to the controller, and the controller calculates the adjustment amount according to the deviation between the preset target angle and the actual angle, and drives the motor to change the angle of the gimbal. In the fixed monitoring scene, this control method can effectively maintain the gimbal at the set position and ensure the stability of the monitoring picture.
[0003] However, in the motion scene such as unmanned aerial vehicle, the vibration amplitude and frequency are complex and changeable, and pure reliance on sensor feedback control cannot guarantee the stability of the picture, which limits the application scene.
[0004] At present, the feedback control technology has time lag in the process of tracking high-speed targets, from the change of target position, to the detection of deviation by the sensor and the transmission to the controller, and then to the calculation of adjustment amount by the controller and the driving of the motor.
[0005] The adaptive control technology depends on accurate mathematical model, and the calculation structure is complex and the calculation amount is large. In order to realize real-time control, a large number of numerical calculations are required according to the model, which requires high hardware performance. This not only increases the system cost, but also may affect the real-time control. SUMMARY
[0006] The purpose of the present application is to provide a feedforward control method for gimbal, which retains the advantages of simple structure and small calculation amount of traditional PID feedback control, introduces feedforward control, and realizes more accurate and rapid gimbal control to solve the problems of adjustment delay and large calculation amount in the background technology.
[0007] To achieve the above purpose, the present application provides the following technical scheme: a feedforward control method for gimbal, comprising the following steps:
[0008] S1, constructing a feedforward control model: only one feedforward control parameter, i.e. target angle parameter, is set for each feedforward control path of the control motor of the gimbal, and each feedforward control path additionally increases a multiplication operation and an addition operation module based on the original PID control;
[0009] S2, inputting initial signal and processing: the target angle, the current angle of the motor and the angular velocity of the motor after IMU decoupling are inputted for each axis of the control motor of the gimbal, the angular velocity after IMU decoupling is directly used as input for the feedforward control path, and is superimposed to the angle PID ring output to obtain the target angular velocity;
[0010] S3, the feedforward control path multiplies the error between the target angular velocity and the actual angular velocity by a corresponding feedforward coefficient, and superimposes the error to the angular PID loop output to obtain a motor control quantity;
[0011] S4, outputting the control quantity: applying the motor control quantity to the motor drive board corresponding to the shaft to control the motor rotation;
[0012] S5, using Simulink to build a finite element single-axis motor simulation model, and comparing the tracking speed and accuracy of the control motor of the gimbal with and without feedforward control under different frequency errors;
[0013] S6, applying external interference vibration with the same frequency and amplitude to the actual gimbal, and using PID control and feedforward control respectively to stabilize the gimbal at the horizontal angle, and comparing the tracking speed and accuracy of the two in the self-stabilization control of the gimbal by observing the angle error of the three-axis stabilization.
[0014] Preferably, the control motor includes a pitch motor, a roll motor and a heading motor controlled by a control circuit board, and the pitch motor, the roll motor and the heading motor are electrically connected with the control circuit board.
[0015] Preferably, the feedforward control path includes an initial signal input module for providing a target angle and an angular velocity instruction of the control motor, a PID controller for performing PID operation on the angle deviation between the target instruction and the feedback signal and outputting a control quantity, a signal conditioning module for processing the signal sampling rate, a motor drive module for converting the voltage instruction output by the control algorithm into an electrical signal for driving the motor, and a feedback monitoring module for collecting the actual angle and position signal of the motor shaft and feeding back to the PID controller.
[0016] The initial signal input module, the PID controller, the signal conditioning module, the motor drive module and the feedback monitoring module are electrically connected.
[0017] Preferably, the first multiplication and addition module is parallel to the PID controller, and the first multiplication and addition module includes a Gain4 gain unit and a SUM1 summation unit for adding the value obtained by the Gain4 gain unit to the output of the PID controller.
[0018] Preferably, the signal conditioning module includes a rate converter and a manual switch, and the rate converter and the manual switch are electrically connected.
[0019] Preferably, the motor driving module comprises a driving circuit and a motor body receiving power input of the driving circuit, the motor body is configured as a three-phase alternating current motor, and the electromagnetic torque TE interface and the motor speed Wm interface of the motor body are electrically connected with the feedback monitoring module.
[0020] Preferably, the feedback monitoring module comprises an angle encoder and a signal observation window for displaying the motor angle, the control quantity and the current signal in real time, and the feedback monitoring module is electrically connected with the signal observation window.
[0021] Preferably, in step S3, the error of the target angular velocity and the actual angular velocity is obtained by the following way:
[0022] The IMU mounted on the lens of the holder is responsible for calculating the actual angle information of the lens, the target angle is input, the arithmetic logic unit of the microcontroller in the control circuit board subtracts the actual angle calculated by the IMU to obtain the angle error, and the angle error is used as the input signal of the PID control path. The angle differential detected by the IMU, i.e. the angular velocity, is used as the input signal of the feedforward control path through decoupling operation.
[0023] Preferably, the holder comprises a control motor, a C-shaped arm, an L-shaped arm, a damping structure, a mounting structure and a shelter with a lens, an inertial measurement sensor and a control circuit board built-in, the lens is used for recording images, the inertial measurement sensor is used for collecting the attitude information of the lens, and the control motor, the inertial measurement sensor and the lens are electrically connected with the control circuit board.
[0024] Compared with the prior art, the present application has the following advantages:
[0025] 1. By adding a feedforward control path on the basis of the traditional PID control method and adjusting the feedforward control parameters, the present application can predict the subsequent intervention adjustment before the error occurs, improve the following effect of the holder control motor and reduce the delay. The motor shaft can be stably maintained at a specific angle, thereby ensuring the camera picture effect.
[0026] 2. The feedforward control path of the present application only needs to increase one multiplication and one addition operation in the traditional PID control path, which can significantly improve the control effect while increasing the calculation amount by a tiny amount. The calculation amount is small and the response is fast, which can widen the application scenarios and application range of the holder and improve its performance in various scenarios. BRIEF DESCRIPTION OF DRAWINGS
[0027] Figure 1 The flowchart of the present application;
[0028] Figure 2 The line connection schematic diagram of initial data processing in the feedforward control path of one motor shaft of the present application;
[0029] Figure 3 The schematic diagram of the line connection for controlling the motor in the feedforward control path of one of the motor shafts of the application;
[0030] Figure 4 The bar chart of the average total time length of the motor shaft control by the traditional PID control method and the average total time length with the feedforward control of the application;
[0031] Figure 5 The error waveform diagram of the three groups of motor shafts of the gimbal under the traditional PID control method;
[0032] Figure 6 The error waveform diagram of the three groups of motor shafts of the gimbal under the feedforward control method of the application;
[0033] Figure 7 The block diagram of the feedforward control method of the application;
[0034] Figure 8 The feedforward control diagram based on the reference input differential of the application;
[0035] Figure 9 The feedforward control diagram based on the reciprocal of the controlled system of the application;
[0036] Figure 10 The feedforward control diagram based on the model prediction of the application;
[0037] Figure 11 The schematic diagram of the gimbal of the application;
[0038] Figure 12 The angle error response curve diagram under the traditional PID control;
[0039] Figure 13 The angular velocity error response curve diagram under the traditional PID control;
[0040] Figure 14 The angle error response curve diagram under the feedforward control of the application;
[0041] Figure 15 The angular velocity error response curve diagram under the feedforward control of the application.
[0042] In the figure: 1, C-shaped arm; 2, L-shaped arm; 3, mounting structure; 4, lens; 5, shelter; 6, damping structure. DETAILED DESCRIPTION
[0043] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.
[0044] Please refer to Figures 1-15 The present application provides a technical solution: a feedforward control method for a gimbal, comprising the following steps:
[0045] S1, constructing a feedforward control model: only one feedforward control parameter is set for each feedforward control path of the control motor of the gimbal, and each feedforward control path additionally increases a multiplication operation and an addition operation module on the basis of the original PID control; as shown in Figure 2 、 Figure 3 and Figure 4 , a feedforward control path for the motor shaft of one of the motor bodies in the control motor, which is parallel to the PID controller. It is known from Figure 4 that only a multiplication and an addition operation are additionally increased on the basis of the original PID control, which significantly improves the control effect while the increased calculation amount is extremely small. According to statistics, the average total calculation time of three motor shafts under the traditional PID control method is 7.8us, and the average total calculation time of three motor shafts under the feedforward control method is 8.54us, which increases the total calculation time of three shafts by 0.74us, which is 9.5% of the original calculation time.
[0046] S2, inputting an initial signal and processing: the target angle, the current angle and the angular velocity of the motor after IMU decoupling of each shaft of the control motor of the gimbal are input, the angular velocity after IMU decoupling is directly used as the input of the feedforward control path, and is superimposed to the angle PID loop output to obtain the target angular velocity; the angle feedforward control adopts the reference input differential mode, as shown in Figure 8 Since the angle differential is the angular velocity, the angular velocity after IMU decoupling is directly used as the angle feedforward input, which not only saves the differential calculation link, but also has a higher input frequency compared with the differential directly calculated based on the angle.
[0047] This method obtains the rate of change information by performing differential operation on the reference input signal. Using this rate of change, the corresponding control action is introduced in advance at the system input. For example, in a motor control system, when the reference speed command changes, the differential of the speed command can quickly adjust the input voltage of the motor, so that the motor responds to the speed change more quickly, reduces the tracking error, and improves the dynamic response performance of the system.
[0048] S3, the feedforward control path multiplies the error between the target angular velocity and the actual angular velocity by a corresponding feedforward coefficient, and superimposes it to the angular PID loop output to obtain the motor control quantity; the angular velocity feedforward control is based on a model, as shown in the figure, the error between the target angular velocity and the actual angular velocity is multiplied by a corresponding feedforward coefficient, and then superimposed on the output of the angular velocity PID loop as the final angular velocity loop output of the shaft, that is, the motor control quantity. Figure 10
[0049] The method uses the prediction model of the system to predict the future output of the system according to the current system state and the reference input in the future period of time. The feedforward control sequence that makes the predicted output as close as possible to the reference output is calculated. For example, in chemical process control, the model-based feedforward control can predict the trend of temperature, pressure and other parameters in advance based on the reaction process model, and calculate the corresponding control quantity to adjust the valve opening, heating power and other actuators in advance to cope with disturbances and set value changes in the process, improve the accuracy and stability of control, and achieve efficient control of complex systems.
[0050] In S3, the angular velocity feedforward control based on a model can be replaced by Figure 9 Based on the mathematical model of the controlled system. By deriving its inverse model, that is, the reciprocal model, the reference input is operated through the inverse model to obtain the feedforward control quantity. Taking a simple first-order inertia system as an example, if the system transfer function is G(s) = 1 / (Ts+1), its inverse model is G-1(s) = Ts+1. When there is a reference input, the control quantity calculated by the inverse model can offset the influence of the dynamic characteristics of the system to some extent, so that the output can track the reference input more quickly, effectively improving the control accuracy and response speed of the system.
[0051] S4, output control quantity: the motor control quantity is applied to the motor drive board corresponding to the shaft to control the motor rotation; even if there are disturbances in the external environment, this mechanism can ensure that the shaft is stably maintained at a specific angle, thereby ensuring the camera picture effect.
[0052] S5, use Simulink to build a finite element single-shaft motor simulation model, and compare the tracking speed and accuracy of the gimbal control motor at different frequency errors with and without feedforward control;
[0053] The effectiveness of the method is verified by Simulink. First, the traditional PID control method is used to adjust the parameters to make the motor follow the angle error and angular velocity error optimally. On this basis, the designed feedforward control path is added, and the feedforward control parameters are adjusted to observe the following performance of the motor to the angle error and angular velocity error. As shown in Figure 12 , Figure 13 , Figure 14 and Figure 15 As shown, the simulation results show that the traditional PID control method can only respond after the error occurs, and both the theory and the simulation results show that this method cannot completely follow the error frequency and there is inevitably a delay. The method with feedforward control can closely follow the error because it intervenes in the adjustment in advance when the error trend occurs. From the Simulink simulation results, it can be known that after the feedforward control is added, the error frequency that cannot be followed originally is followed, and the upper limit of the response of the system to the error frequency is improved.
[0054] S6, the same frequency and amplitude of external interference vibration is applied on the actual gimbal, the gimbal is stabilized at the horizontal angle by using the traditional PID control and the feedforward control respectively, the angle error of the three-axis stabilization is observed, and the tracking speed and accuracy of the two in the gimbal self-stabilization control are compared. Figure 5 and Figure 6 As shown, from the error waveform, under the same interference, the gimbal self-stabilization accuracy is improved from the original 0.02° to 0.01°, and the experimental results show that the feedforward control is better than the traditional PID control in the gimbal stabilization effect, and the performance is more outstanding.
[0055] The control motor includes a pitch motor, a roll motor and a heading motor controlled by a control circuit board, and the pitch motor, the roll motor and the heading motor are electrically connected with the control circuit board. Only the feedforward control path of one group of motors is displayed in the embodiment, the other two groups are the same as this group, and the three groups of motors are independently controlled.
[0056] The feedforward control path includes an initial signal input module for providing a target angle and an angular velocity instruction of the control motor, a PID controller for performing PID operation on the angle deviation of the target instruction and a feedback signal and outputting a control amount, a signal conditioning module for processing a signal sampling rate, a motor driving module for converting a voltage instruction output by the control algorithm into a strong electric signal for driving the motor, and a feedback monitoring module for collecting actual angle and position signals of the motor shaft and feeding back to the PID controller;
[0057] The input is a target angle expected to be maintained by the gimbal, and an IMU installed on the gimbal lens is responsible for calculating the actual angle information of the lens. In the PID control path, the angle error is sequentially subjected to proportional (P), integral (I) and differential (D) operations, and the results are summed to obtain the PID angle output. The PID control path is the same as the prior art.
[0058] The initial signal input module, the PID controller, the signal conditioning module, the motor driving module and the feedback monitoring module are electrically connected.
[0059] The first multiplication operation and the first addition operation module is parallel to the PID controller, and the first multiplication operation and the first addition operation module comprises a Gain4 gain unit and a SUM1 summation unit for adding the value obtained by the Gain4 gain unit to the output of the PID controller.
[0060] After the initial data input, the instruction performs a differential operation, and the gain Gain4 is adjusted to extract the rate information of the instruction, such as the dynamic change trend of the target angular velocity, to provide a basis for feedforward control or dynamic compensation.
[0061] The signal conditioning module comprises a rate converter and a manual switch, the rate converter ensures signal synchronization and conflict-free between different modules, and the manual switch provides a manual and automatic control switching function, facilitating testing, such as manual intervention in the control process or switching between different control strategies, and the rate converter and the manual switch are electrically connected.
[0062] The motor driving module comprises a driving circuit and a motor body receiving power input from the driving circuit, the motor body is a three-phase alternating current motor, and the electromagnetic torque TE interface and the motor speed Wm interface of the motor body are electrically connected with the feedback monitoring module. Figure 3 As shown, the motor body receives power input from the driving circuit, the angle and angular velocity of the output shaft, and the interfaces such as the electromagnetic torque Te and the motor speed Wm are fed back to the system to form a closed-loop control.
[0063] The feedback monitoring module comprises an angle encoder and a signal observation window for real-time display of motor angle, control amount and current signal, the signal observation window displays signals in real time for debugging and analysis, such as verifying whether the control algorithm enables the motor shaft to accurately track the target instruction, and the feedback monitoring module and the signal observation window are electrically connected.
[0064] In step S3, the error between the target angular velocity and the actual angular velocity is obtained by the following method:
[0065] The IMU installed on the lens of the gimbal is responsible for calculating the actual angle information of the lens, the target angle is input, and the arithmetic logic unit of the microcontroller in the control circuit board subtracts the target angle from the actual angle calculated by the IMU to obtain the angle error, and the angle error is simultaneously used as the input signal of the traditional PID control path and the feedforward control path.
[0066] The target angular velocity is subtracted from the angular velocity measured by the IMU and decoupled, to obtain an angular velocity error. The angular velocity error is input to an angular velocity PID control channel and an angular velocity feedforward control channel. In the angular velocity PID control channel, the angular velocity error is calculated by a proportional (P), integral (I) and derivative (D) calculation and summed to obtain a PID angular velocity output. The PID angular velocity output is added to a feedforward angular velocity output to obtain an angular velocity control output, i.e. a motor voltage.
[0067] The motor voltage is transmitted to a drive board to control the motor to rotate as required, so as to ensure that the gimbal is stable at the target angle. The IMU and the motor are both mounted on the gimbal lens, and the IMU is responsible for detecting and calculating the angle and angular velocity of the gimbal, and the output thereof is used for gimbal control operation.
[0068] The gimbal comprises a control motor, a C-shaped arm, an L-shaped arm, a damping structure, a mounting structure, and a shelter in which a lens, an inertial measurement sensor and a control circuit board are arranged, the lens is used for recording images, the inertial measurement sensor is used for collecting attitude information of the lens, and the control motor, the inertial measurement sensor and the lens are all electrically connected with the control circuit board.
[0069] The control circuit board calculates the required voltage of the motor according to the target angle of the gimbal and the information collected by the IMU, and then controls the rotation of the motor.
[0070] On the basis of the conventional PID control mode, the feedforward control channel is added, so that the error trend can be predicted and adjusted in advance, the following effect of the gimbal control motor is improved, and the delay is reduced.
[0071] Although the embodiments of the present application have been shown and described, it can be understood by those skilled in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the present application, and the scope of the present application is defined by the appended claims and their equivalents.
Claims
1. A feedforward control method for a gimbal, characterized in that, The method comprises the following steps: S1, constructing a feedforward control model: the control motor of the gimbal is provided with only one feedforward control parameter, i.e., a target angle parameter, on each feedforward control path, and each feedforward control path additionally increases a multiplication operation and an addition operation module on the basis of original PID control; S2, inputting initial signals and processing: the control motor of the gimbal inputs a target angle, a current angle and an angular velocity of the motor after IMU decoupling, the feedforward control path directly uses the angular velocity after IMU decoupling as input, and the angular velocity is superimposed to the angle PID ring output to obtain a target angular velocity; S3, the feedforward control path multiplies an error between the target angular velocity and an actual angular velocity by a corresponding feedforward coefficient, and the error is superimposed to the angle PID ring output to obtain a motor control amount; S4, outputting the control amount: the motor control amount is applied to a motor drive board corresponding to the axis to control the rotation of the motor; S5, using Simulink to build a finite element single-axis motor simulation model, and comparing the tracking speed and accuracy of the control motor of the gimbal to different frequency errors with and without feedforward control; S6, applying external interference vibration with the same frequency and amplitude to the actual gimbal, using PID control and feedforward control respectively, stabilizing the gimbal at a horizontal angle, observing the angle error of three-axis stabilization, and comparing the tracking speed and accuracy of the two in the self-stabilization control of the gimbal.
2. The feedforward control method for a pan-tilt according to claim 1, characterized in that: The control motor includes a pitch motor, a roll motor and a heading motor controlled by a control circuit board, and the pitch motor, the roll motor and the heading motor are electrically connected with the control circuit board.
3. The feedforward control method for a pan-tilt according to claim 2, characterized in that: The feedforward control path includes an initial signal input module providing a target angle and an angular velocity instruction of the control motor, a PID controller performing PID operation on the angle deviation of the target instruction and the feedback signal and outputting a control amount, a signal conditioning module processing a signal sampling rate, a motor driving module converting a voltage instruction output by the control algorithm into an electrical signal for driving the motor, and a feedback monitoring module collecting actual angle and position signals of the motor shaft and feeding back to the PID controller. The initial signal input module, the PID controller, the signal conditioning module, the motor driving module and the feedback monitoring module are electrically connected.
4. The feedforward control method for a pan-tilt according to claim 3, characterized in that: The multiplication operation and the addition operation module are parallel to the PID controller, and the multiplication operation and the addition operation module include a Gain4 gain unit and a SUM1 summation unit adding a value obtained by the Gain4 gain unit to an output of the PID controller.
5. The feedforward control method for a pan-tilt according to claim 4, characterized in that: The signal conditioning module includes a rate converter and a manual switch, and the rate converter and the manual switch are electrically connected.
6. The feedforward control method for a pan-tilt head according to claim 5, wherein: The motor driving module includes a driving circuit and a motor body receiving power input of the driving circuit, the motor body is a three-phase alternating current motor, and an electromagnetic torque TE interface and a motor speed Wm interface of the motor body are electrically connected with the feedback monitoring module.
7. The feedforward control method for a pan-tilt according to claim 6, characterized in that: The feedback monitoring module includes an angle encoder and a signal observation window displaying motor angle, control amount and current signal in real time, and the feedback monitoring module and the signal observation window are electrically connected.
8. The feedforward control method for a pan-tilt head according to claim 7, characterized in that: In step S3, the error between the target angular velocity and the actual angular velocity is obtained by the following way: The IMU installed on the lens of the holder is responsible for calculating the actual angle information of the lens, inputting the target angle, and the microcontroller arithmetic logic unit in the control circuit board subtracts the target angle from the actual angle calculated by the IMU to obtain the angle error, which is used as the input signal of the PID control path. The angle differential detected by the IMU, i.e. the angular velocity, is used as the input signal of the feedforward control path through decoupling operation.
9. The feedforward control method for a pan-tilt head according to claim 1, characterized in that: The holder includes a control motor, a C-shaped arm, an L-shaped arm, a damping structure, a mounting structure, and a shelter with a lens, an inertial measurement sensor, and a control circuit board built-in, the lens is used for recording images, the inertial measurement sensor is used for collecting attitude information of the lens, and the control motor, the inertial measurement sensor, and the lens are all electrically connected with the control circuit board.