Control method for controlling variable load of linear driver based on torque of push rod motor

Abstract

The invention discloses a control method for controlling variable load of a linear driver based on torque of a push rod motor. The control method comprises the following steps: acquiring a current overturning angle theta of a hood; calculating the gravitational torque Mg of the hood, and calculating the torque Mp of the push rod motor according to the acceleration requirement of the hood; according to the torque of the push rod motor, the output force Fp of the push rod is calculated to judge whether the angle of the hood exceeds 90 degrees or not, and the output direction of the push rod is determined according to the judgment result: when theta is greater than or equal to 0 degree and less than or equal to 90 degrees, forward thrust is output; when theta is smaller than or equal to 180 degrees, reverse braking force is output; according to the output force of the push rod, corresponding driving current is generated to control the linear driver, and stable opening and closing of the hood are achieved.

Description

Technical Field

[0001] The present invention relates to a control method for a DC motor linear driver, and particularly to a variable-load adaptive control method applied to the opening and closing control of the engine hood of construction machinery and agricultural machinery. Background Art

[0002] The maintenance and repair of the engines of construction machinery and agricultural machinery require frequent opening of the engine hood. At present, most construction machinery such as loaders and rollers adopt an integral tilting engine hood, and its structural feature is that the front end of the engine hood is connected to the vehicle frame through a hinge. The opening of the engine hood is usually realized by means of gas springs, manual hydraulic pumps, valve-controlled hydraulic systems, and linear drivers.

[0003] The traditional gas spring method is laborious to operate, has a large impact force on the engine hood when opening, and has a limited opening angle; the manual hydraulic pump method has a slow opening speed and a high labor intensity for maintenance personnel; the valve-controlled hydraulic system has a complex structure, high cost, and difficult maintenance. In recent years, using a DC linear driver to open and close the engine hood is becoming an industry trend, but the existing direct drive method also has obvious deficiencies.

[0004] Currently, most adopt the method of directly driving the engine hood by a motor. During the opening and closing process, due to the continuous change of the center of gravity position of the engine hood, the load of the motor changes dynamically, resulting in unstable speed during the opening and closing of the engine hood, manifested as being fast and slow, and jittering. Seriously, this instability may damage the engine hood and the driver. Especially when the engine hood is close to the starting point during closing, due to the action of gravity and inertia, a large impact is generated between the engine hood and the vehicle frame, causing deformation or damage to the engine hood.

[0005] The existing technology generally adopts a fixed current control strategy and cannot adapt to the load change of the engine hood at different angular positions. Although some systems adopt position closed-loop control, an accurate mathematical relationship between the angle and the required thrust is not established, and smooth control cannot be achieved. In addition, the lack of effective acceleration and deceleration control strategies results in the problem of mechanical shock during startup and stop still not being solved.

[0006] Therefore, there is an urgent need to develop an adaptive control method based on the torque control of the push rod motor. Through real-time feedback of the angle sensor and dynamic torque adjustment, smooth control and safety protection of the engine hood under load change conditions can be achieved. Summary of the Invention

[0007] The object of the present invention is to solve the problems existing in the prior art, and provide a variable-load control method for a linear driver based on the torque control of a push rod motor. By establishing an accurate mathematical relationship model between the flipping angle of the engine hood and the driving force, combined with the real-time feedback of the angle sensor, the output force of the push rod is dynamically adjusted to achieve smooth opening and closing and safety protection of the engine hood under load change conditions.

[0008] The control method proposed by the present invention is based on the rigid body dynamics model, and an accurate mathematical relationship between the hood flipping angle and the required driving force is established. In this method, first, the current flipping angle θ of the hood is obtained, and then the gravitational moment M of the hood is calculated g . The gravitational moment is calculated by the formula , where m is the mass of the hood, g is the acceleration due to gravity, L c is the distance from the center of gravity of the hood to the rotation center, and θ is the hood flipping angle. The gravitational moment changes with the change of the hood flipping angle, and it is the largest when the hood is in the horizontal position (θ = 0°) and zero when in the vertical position (θ = 90°).

[0009] According to the acceleration requirement of the hood, the torque of the push rod motor is calculated , where I is the moment of inertia of the hood relative to the rotation center, and α is the angular acceleration of the hood. The moment of inertia I can be calculated by the formula , assuming a simplified model when the hood is a uniform flat plate.

[0010] According to the torque of the push rod motor, the output force of the push rod is calculated , where L2 is the length of the push rod force arm, and α is the angle between the push rod and the force arm. Substituting all the parameters, the complete formula for the output force of the push rod is obtained: .

[0011] The method of the present invention also considers the characteristic that the gravitational moment changes from a resistance moment to a driving moment after the hood passes through the midline (θ = 90°), and judges the output direction of the push rod according to the hood angle: when 0° ≤ θ ≤ 90°, a positive thrust is output; when 90° < θ ≤ 180°, a reverse braking force is output. According to the calculated output force of the push rod, a corresponding drive current is generated to control the linear actuator to achieve smooth opening and closing of the hood.

[0012] To achieve smooth driving, the present invention adopts an S-shaped curve to control the acceleration process. The target angular velocity of the hood during the acceleration stage is calculated by the formula , and the angular acceleration is calculated by the formula . Compared with the traditional linear acceleration, this S-shaped curve is smoother at the start and the end of acceleration, reducing mechanical shock. ]>

[0013] During the deceleration stage, the present invention adopts a non-linear deceleration strategy to control the angular velocity by the formula , where d norm is the normalized remaining distance, and n is the deceleration curve index and is greater than 1. This method realizes smooth deceleration when approaching the target position, effectively avoiding mechanical shock.

[0014] The present invention also calculates the length of the push rod through geometric relationships: , where the coordinates of the point (x3, y3) are determined by the hood angle θ: , .

[0015] At the same time, calculate the extension and retraction speed of the push rod: , to achieve precise control of the push rod movement.

[0016] The present invention also provides a variable load adaptive control system based on the above method, comprising an angle sensor, a controller, a linear actuator, and a built-in limit switch. The angle sensor measures the hood's tilt angle θ in real time. The controller calculates the gravity torque and pushrod motor torque based on the angle sensor input, and calculates the required pushrod output force. The linear actuator controls the pushrod to output the corresponding force based on the drive signal output by the controller. The built-in limit switch triggers a stop when the hood reaches its limit position, serving as a secondary protection for the angle sensor.

[0017] The control method of the present invention can automatically adjust the drive motor current according to the changes in the push (pull) force required at different positions during the hood flipping process, thereby avoiding fluctuations in movement speed and unstable jitter. When the hood falls and approaches the starting point, deceleration control is implemented to prevent the hood from being damaged by excessive pulling by the driver. The starting and ending points of the hood can be arbitrarily set using angle sensors, which is convenient and flexible (the linear driver has a built-in travel switch that serves as a secondary protection). The device can automatically adjust the drive current according to the size and direction of the load, making the hood opening and closing more stable and reliable. Compared with other types of hood opening and closing devices, it has a simple structure and is easy to operate, which not only greatly reduces the labor intensity of staff but also improves work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the connection between the hood and the linear actuator of the present invention; Figure 2 is a force analysis diagram of the hood movement process in an embodiment of the present invention; Figure 3 This is a schematic diagram of the hood flipping state with 0°≤θ≤90° in the present invention; Figure 4 This is a schematic diagram of the hood state when θ=90° in the present invention; Figure 5 This is a schematic diagram of the hood flipping state with 90°<θ≤180° in the present invention; Figure 6 It is a schematic diagram of the process structure of the present invention.

[0019] Reference numerals: 1. hood; 2. linear actuator; 3. controller ECU; 4. angle sensor. DETAILED DESCRIPTION

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] As Figure 1 , Figure 2 shown, the variable-load adaptive control system of the linear actuator based on the torque control of the push-rod motor provided by the present invention includes an engine hood 1, a linear actuator 2, a controller ECU 3, an angle sensor 4, and a travel switch built into the linear actuator (not shown in the figure). The hood 1 is connected to the vehicle frame through a hinge point O1. The telescopic rod of the linear actuator 3 is connected to the connection point O3 of the hood 1 through a pin shaft, and the base of the linear actuator 3 is connected to the connection point O2 of the vehicle frame through a pin shaft. The controller ECU 3 receives the hood flipping angle θ measured by the angle sensor 4 and outputs a control signal to the linear actuator 3.

[0022] As Figure 6 shown, the control method of the present invention is based on the rigid body dynamics model, and an accurate mathematical relationship between the hood flipping angle and the required driving force is established. The rotation of the hood follows the basic equation of rigid body rotational dynamics: , where ∑M is the total torque acting on the hood, I is the moment of inertia of the hood relative to the rotation center O1, and α is the angular acceleration of the hood. The hood is subjected to the combined action of the push-rod motor torque M p and the gravity torque M g : , so the required push-rod motor torque can be expressed as: .

[0023] The moment of inertia I of the hood is related to its mass distribution. Assuming the hood is a uniform flat plate, its moment of inertia can be approximated as: , where m is the mass of the hood, and L c is the distance from the center of gravity of the hood to the rotation center O1. In practical applications, a more accurate moment of inertia value can be obtained through experimental measurement.

[0024] The gravity torque M g varies with the change of the hood flipping angle θ: , where g is the acceleration due to gravity, θ is the flipping angle of the hood, and cos(θ) describes the component of gravity in the direction perpendicular to the force arm. This formula shows that the gravity torque is maximum when the hood is in the horizontal position (θ = 0°) and zero when in the vertical position (θ = 90°). When the hood angle exceeds 90°, cos(θ) becomes negative, and the gravity torque becomes a driving torque instead of a resistance torque.

[0025] The output force F p of the push rod and the push-rod motor torque M p are related as follows: , where L2 is the length of the push-rod force arm, and α is the angle between the push rod and the force arm. Solving for the push-rod output force: . Substituting the push-rod motor torque formula, the complete push-rod output force formula is obtained: This formula is the core of the present invention, indicating that the output force of the push rod needs to be dynamically adjusted according to the random hood angle.

[0026] To achieve smooth driving, the present invention adopts an S-shaped curve to control the acceleration process. The target angular velocity of the hood during the acceleration phase is calculated by the formula where ω max is the target constant angular velocity, t acc is the time required to complete the acceleration, t is the current time and 0 ≤ t ≤ t acc . The angular acceleration α(t) is the derivative of the angular velocity with respect to time and can be calculated by the formula . This S-shaped curve is smoother at the start and end of acceleration compared to the traditional linear acceleration curve, reducing mechanical shock.

[0027] The present invention takes into account the characteristic that the gravitational moment changes from the resistance moment to the driving moment after the hood passes through the midline (as shown in Figure 4 , θ = 90°) and adopts a phased control strategy. When the hood angle is in the range of 0° ≤ θ ≤ 90° (resistance phase), the push rod outputs a positive thrust; when the hood angle is in the range of 90° < θ ≤ 180° (driving force phase), the push rod needs to provide a reverse braking force. This control strategy can be expressed as: As shown in Figure 3 , , when 0° ≤ θ ≤ 90° (resistance phase); As shown in Figure 5 , , when 90° < θ ≤ 180° (driving force phase).

[0028] During the deceleration phase, the present invention adopts a non-linear deceleration strategy. When the hood approaches the target position, the normalized remaining distance is calculated, where θ remain is the remaining angle and θ threshold is the deceleration trigger angle threshold. Then, a non-linear deceleration function is applied to control the angular velocity: , where n is the deceleration curve exponent and n > 1. A larger n value provides a smoother deceleration process, and the typical value range is 1.5 - 3.0. This method achieves smooth deceleration when approaching the target position and effectively avoids mechanical shock.

[0029] The present invention also calculates the length and speed of the push rod through geometric relationships. The length of the push rod , where the coordinates of the point (x3, y3) are determined by the hood angle θ: , . (x1, y1) are the coordinates of the hood rotation center O1, (x2, y2) are the coordinates of the fixed end O2 of the push rod, and L1 is the distance from the rotation center O1 to the push rod connection point O3. The telescopic speed of the push rod , where ω is the current angular velocity of the hood. This speed calculation formula realizes the mapping relationship between the angular velocity of the hood and the linear velocity of the push rod, ensuring the synchronization of the push rod movement and the hood rotation.

[0030] The control process of the present invention includes four stages: initialization, acceleration, constant-speed operation, and deceleration. In the initialization stage, mechanical parameters (m, L c , I), geometric parameters (L1, L2), and control parameters (ω max , t acc , n) are set, the angle sensor is calibrated, the starting point angle θmin and the ending point angle θ max are determined, and the driver status is checked. In the acceleration stage, an on / off instruction is received, the current hood angle θ current is read, the target angular velocity and angular acceleration are calculated according to the S-shaped acceleration curve, the gravity moment, the push rod motor moment, and the push rod output force are calculated, and the drive current is output. In the constant-speed operation stage, the current angle θ current is read, the remaining angle θ remain is calculated, it is judged whether to enter the deceleration stage, the gravity moment is calculated, it is judged whether to pass the midline position, the push rod output force is calculated, and the drive current is output. In the deceleration stage, the normalized remaining distance d norm is calculated, the non-linear deceleration function is applied to reduce the angular velocity, the required push rod force is recalculated, the drive current is output, and the drive is stopped when approaching the target position.

[0031] During the whole control process, the system continuously monitors the angle abnormality, current overload, and the status of the travel switch to achieve multiple safety protections. When the angle exceeds the preset range, the stop is triggered; when the current exceeds the safety threshold for a certain period of time, the protection is triggered; when the travel switch is triggered, the drive is immediately stopped.

[0032] The control system of the present invention includes an angle sensor 4, a controller ECU3, a linear driver 3, and a built-in travel switch. The angle sensor 4 can be a potentiometer, a Hall sensor, an encoder, etc., and is installed at the hinge of the hood to measure the flipping angle θ of the hood in real time and output it to the controller ECU3. The controller ECU3 is built with a microprocessor and a current drive circuit. According to the input of the angle sensor, it executes the above control method, calculates the gravity moment and the push rod motor moment, and calculates the required push rod output force according to the formula and then converts it into the corresponding drive current to control the linear driver 3. The linear driver 3 includes a motor and a telescopic rod, and controls the push rod to output the corresponding force according to the drive signal output by the controller to realize the smooth opening and closing of the hood. The built-in travel switch 6 is set inside the linear driver and is triggered to stop when the hood reaches the limit position, serving as a secondary protection for the angle sensor.

[0033] By adopting the control method of the present invention, it is possible to automatically adjust the driving motor current according to the change of the required pushing (pulling) force at different positions during the flipping process of the hood, avoiding the phenomena of sudden fast and slow movement speed and unstable jitter; when the hood falls close to the starting point, deceleration control is achieved to avoid damage to the hood caused by over-pulling by the driver; the starting point and the ending point of the hood can be arbitrarily set through the angle sensor, which is convenient and flexible. This device can automatically adjust the driving current according to the size and direction change of the load, making the opening and closing of the hood smoother and more reliable. Compared with other types of hood opening and closing devices, it has a simple structure and convenient operation, which not only greatly reduces the labor intensity of the staff, but also improves the work efficiency.

[0034] To better understand the present invention, the present invention provides a calculation example of the variable load control method of the linear actuator based on the torque control of the push rod motor, which is specifically as follows: Initial parameter setting This example is based on the actual parameters of the hood of a certain type of loader for method verification calculation, and the relevant parameters are as follows: The mass of the hood m = 80 kg; The distance L from the center of gravity to the rotation center c = 0.6 m; The moment of inertia I = m·L c ² = 80×0.6² = 28.8 kg·m²; The length of the push rod force arm L2 = 0.3 m; The acceleration time t acc = 2 s; The target uniform angular velocity ω max = 0.2 rad / s; The deceleration curve index n = 2.0; The deceleration trigger angle threshold θ threshold = 15°; The gravitational acceleration g = 9.8 m / s²; Geometric parameter setting: The coordinates of the rotation center O1(x1,y1) of the hood = (0,0) m; The coordinates of the fixed end of the push rod O2(x2,y2) = (0.2, -0.3) m; The distance L1 from the rotation center to the connection point of the push rod = 0.5 m; The initial included angle α between the push rod and the force arm = 60°; The target opening angle of the hood is set as θ max = 110°, and the initial closed state angle is θmin = 0°.

[0035] The calculation process is as follows: 1. Calculation in the acceleration stage (t = 0 s to t = 2 s) Four time points (t = 0s, t = 0.5s, t = 1s, t = 2s) are selected for detailed calculations to show the dynamic changes during the acceleration phase.

[0036] Calculation at t = 0s First, obtain the current flipping angle θ(0) = 0° of the hood. Calculate the gravitational moment: M g = m·g·L c ·cos(θ) = 80×9.8×0.6×cos(0°) = 80×9.8×0.6×1 = 470.4N·m.

[0037] Apply the S-shaped acceleration curve to calculate the target angular velocity: ω(0) = ω max ·(3·(0 / t acc )² - 2·(0 / t acc )³) = 0.2×(3×0 - 2×0) = 0rad / s Calculate the angular acceleration: α(0) = (6·ω max / t acc ²)·(0 / t acc - 0² / t acc ²) = (6×0.2 / 4)×0 = 0rad / s² Calculate the torque of the push rod motor: M p = I·α - M g = 28.8×0 - 470.4 = -470.4N·m (the negative sign indicates that the gravity generates a resistance torque, and the push rod needs to provide a positive torque to resist) Calculate the output force of the push rod: F p = M p / (L2·sin(α)) = -470.4 / (0.3×sin(60°)) = -470.4 / (0.3×0.866) = -1810.6N Since the hood angle θ = 0° < 90° at this time, it is in the resistance stage, and the push rod needs to provide a positive thrust. Therefore, the actual thrust value is 1810.6N.

[0038] Calculate the coordinates of the push rod connection point: x3 = x1 + L1·sin(θ) = 0 + 0.5×sin(0°) = 0m y3 = y1 - L1·cos(θ) = 0 - 0.5×cos(0°) = -0.5m Calculate the current length of the push rod: L p = √((x3 - x2)² + (y3 - y2)²) = √((0 - 0.2)² + (-0.5 - (-0.3))²) = √(0.04 + 0.04) = √0.08 = 0.283m At this time, the telescopic speed of the push rod is 0 because the angular velocity in the initial state is 0.

[0039] Calculation at t = 0.5s Calculate the target angular velocity using the S-shaped acceleration curve: ω(0.5) = ω max ·(3·(0.5 / 2)² - 2·(0.5 / 2)³) = 0.2×(3×0.0625 - 2×0.015625) = 0.2×(0.1875 - 0.03125) = 0.2×0.15625 = 0.03125rad / s Calculate the angular acceleration: α(0.5) = (6·ω max / t acc ²)·(0.5 / t acc - (0.5)² / t acc ²) = (6×0.2 / 4)·(0.25 - 0.0625) = 0.3×0.1875 = 0.05625rad / s² Estimate the current angle (by integral approximation): θ(0.5) ≈ θ(0) + ω(0)×0.5 + 0.5×α(0)×0.5² ≈ 0 + 0×0.5 + 0.5×0×0.25 ≈ 0° (In the initial acceleration state, the angle change is very small and is simplified to 0 here) Calculate the gravitational moment: M g = 80×9.8×0.6×cos(0°) = 470.4N·m Calculate the torque of the push rod motor: M p = 28.8×0.05625 - 470.4 = 1.62 - 470.4 = -468.78N·m Calculate the output force of the push rod: F p = -468.78 / (0.3×sin(60°)) = -468.78 / (0.3×0.866) = -1804.25N Since the hood angle θ ≈ 0° < 90° at this time and it is in the resistance stage, the push rod needs to provide a positive thrust, so the actual thrust value is 1804.25N.

[0040] Calculation at t = 1s Calculate the target angular velocity using the S-shaped acceleration curve: ω(1) = 0.2×(3×(1 / 2)² - 2×(1 / 2)³) = 0.2×(3×0.25 - 2×0.125) = 0.2×(0.75 - 0.25) = 0.2×0.5 = 0.1rad / s Calculate the angular acceleration: α(1) = (6×0.2 / 4)×(1 / 2 - (1)² / 4) = 0.3×(0.5 - 0.25) = 0.3×0.25 = 0.075 rad / s² Estimate the current angle (by integral approximation): θ(1) ≈ θ(0) + ∫¹ω(t)dt ≈ 0 + 0.05 ≈ 2.86° (estimated value obtained using average angular velocity 0.05 rad / s) Calculate the gravitational moment: M g = 80×9.8×0.6×cos(2.86°) = 80×9.8×0.6×0.9988 = 469.8 N·m Calculate the torque of the push rod motor: M p = 28.8×0.075 - 469.8 = 2.16 - 469.8 = -467.64 N·m Calculate the output force of the push rod: F p = -467.64 / (0.3×sin(60°)) = -467.64 / (0.3×0.866) = -1799.5 N Since the hood angle θ = 2.86° < 90° at this time and it is in the resistance stage, the push rod needs to provide a positive thrust, so the actual thrust value is 1799.5 N.

[0041] Calculation at t = 2 s (end point of acceleration) Apply the S-shaped acceleration curve to calculate the target angular velocity: ω(2) = 0.2×(3×(2 / 2)² - 2×(2 / 2)³) = 0.2×(3×1 - 2×1) = 0.2×1 = 0.2 rad / s Calculate the angular acceleration: α(2) = (6×0.2 / 4)×(2 / 2 - (2)² / 4) = 0.3×(1 - 1) = 0 rad / s² (angular acceleration at the end point of acceleration is 0) Estimate the current angle (by integral approximation): θ(2) ≈ θ(0) + ∫²ω(t)dt ≈ 0 + 0.2 ≈ 11.46° (estimated value obtained using average angular velocity 0.1 rad / s) Calculate the gravitational moment: M g = 80×9.8×0.6×cos(11.46°) = 80×9.8×0.6×0.98 = 461.1 N·m Calculate the torque of the push rod motor: M p = 28.8×0 - 461.1 = -461.1 N·m Calculate the output force of the push rod: F p =-461.1 / (0.3×sin(60°))=-461.1 / (0.3×0.866)=-1775.3N Since the hood angle θ = 11.46° < 90° at this time and it is in the resistance stage, the push rod needs to provide a positive thrust. Therefore, the actual thrust value is 1775.3N.

[0042] 2. Calculation in the uniform motion stage Select three angular positions (θ = 30°, θ = 60°, θ = 90°) for calculation to show the thrust adjustment with the angle change in the uniform motion stage.

[0043] Calculation when θ = 30° In the uniform motion stage, the angular velocity remains a constant value ω = 0.2 rad / s, and the angular acceleration α = 0 rad / s².

[0044] Calculate the gravitational moment: M g =80×9.8×0.6×cos(30°)=80×9.8×0.6×0.866=407.5N·m Calculate the torque of the push rod motor: M p =28.8×0 - 407.5=-407.5N·m Calculate the output force of the push rod: F p =-407.5 / (0.3×sin(60°))=-407.5 / (0.3×0.866)=-1568.2N Since the hood angle θ = 30° < 90° at this time and it is in the resistance stage, the push rod needs to provide a positive thrust. Therefore, the actual thrust value is 1568.2N.

[0045] Calculate the coordinates of the push rod connection point: x3 = 0 + 0.5×sin(30°)=0 + 0.5×0.5 = 0.25m y3 = 0 - 0.5×cos(30°)=0 - 0.5×0.866=-0.433m Calculate the current length of the push rod: L p =√((0.25 - 0.2)²+(-0.433 - (-0.3))²)=√(0.0025 + 0.01773)=√0.02023 = 0.142m Calculate the telescopic speed of the push rod: v p=0.2×(1 / 0.142)×[(0.25 - 0.2)(0.5×cos(30°)) + ((-0.433) - (-0.3))(0.5×sin(30°))] = 0.2×7.04×[0.05×0.433 + (-0.133)×0.25] = 1.41×[0.02165 - 0.03325] = 1.41×(-0.0116) = -0.0164 m / s (The negative value indicates the push rod contracts) Calculation when θ = 60° Calculate the gravitational moment: M g = 80×9.8×0.6×cos(60°) = 80×9.8×0.6×0.5 = 235.2 N·m Calculate the moment of the push rod motor: M p = 28.8×0 - 235.2 = -235.2 N·m Calculate the output force of the push rod: F p = -235.2 / (0.3×sin(60°)) = -235.2 / (0.3×0.866) = -905.1 N Since the hood angle θ = 60° < 90° at this time and it is in the resistance stage, the push rod needs to provide a positive thrust. Therefore, the actual thrust value is 905.1 N.

[0046] Calculate the coordinates of the push rod connection point: x3 = 0 + 0.5×sin(60°) = 0 + 0.5×0.866 = 0.433 m y3 = 0 - 0.5×cos(60°) = 0 - 0.5×0.5 = -0.25 m Calculate the current length of the push rod: L p = √((0.433 - 0.2)² + (-0.25 - (-0.3))²) = √(0.05429 + 0.0025) = √0.05679 = 0.238 m Calculate the telescopic speed of the push rod: v … p = 0.2×(1 / 0.238)×[(0.433 - 0.2)(0.5×cos(60°)) + ((-0.25) - (-�0.3))(0.5×sin(60°))] = 0.2×4.2×[0.233×0.25 + 0.05×0.866] = 0.84×[0.05825 + 0.0433] = 0.84×0.10155 = 0.0853 m / s (The positive value indicates the push rod extends) Calculation when θ = 90° Calculate the gravitational moment: Mg = 80 × 9.8 × 0.6 × cos(90°) = 80 × 9.8 × 0.6 × 0 = 0 N·m (The gravitational moment at the 90° position is zero) Calculate the torque of the push rod motor: M p = 28.8 × 0 - 0 = 0 N·m Calculate the output force of the push rod: F p = 0 / (0.3 × sin(60°)) = 0 / (0.3 × 0.866) = 0 N (No thrust is required at the 90° position) Calculate the coordinates of the push rod connection point: x3 = 0 + 0.5 × sin(90°) = 0 + 0.5 × 1 = 0.5 m y3 = 0 - 0.5 × cos(90°) = 0 - 0.5 × 0 = 0 m Calculate the current length of the push rod: L p = √((0.5 - 0.2)² + (0 - (-0.3))²) = √(0.09 + 0.09) = √0.18 = 0.424 m Calculate the telescopic speed of the push rod: v p = 0.2 × (1 / 0.424) × [(0.5 - 0.2)(0.5 × cos(90°)) + (0 - (-0.3))(0.5 × sin(90°))] = 0.2 × 2.358 × [0.3 × 0 + 0.3 × 1] = 0.472 × 0.3 = 0.142 m / s (A positive value indicates that the push rod extends) 3. Calculation after passing the midline (θ = 100°) After the hood angle exceeds 90°, the gravitational moment changes from a resistance moment to a driving moment, and the push rod needs to provide a reverse braking force.

[0047] Calculate the gravitational moment: M g = 80 × 9.8 × 0.6 × cos(100°) = 80 × 9.8 × 0.6 × (-0.1736) = -81.7 N·m (The negative sign indicates that the gravity generates a driving moment) Calculate the torque of the push rod motor: M p = 28.8 × 0 - (-81.7) = 81.7 N·m (The positive sign indicates that the push rod needs to provide a resistance moment) Calculate the output force of the push rod: F p = 81.7 / (0.3 × sin(60°)) = 81.7 / (0.3 × 0.866) = 314.5 N Since the hood angle θ = 100° > 90° at this time and it is in the driving force stage, the push rod needs to provide reverse braking force, so the output braking force is 314.5 N.

[0048] 4. Deceleration stage calculation Assume that the hood is close to the target position θ = 100°, and there is still 10° angle to reach the target position θ max = 110°.

[0049] Calculate the remaining angle: θ remain = |θ max - θ current | = |110° - 100°| = 10° Since θ remain < θ threshold (15°), it enters the deceleration stage.

[0050] Calculate the normalized remaining distance: d norm = θ remain / θ threshold = 10 / 15 = 0.667 Apply the non - linear deceleration function to calculate the target angular velocity: ω = ω max · (d norm ) n = 0.2×(0.667)² = 0.2×0.445 = 0.089 rad / s (the angular velocity is reduced to 44.5% of the uniform state) Calculate the required angular deceleration (assuming it needs to decelerate from 0.2 rad / s to 0.089 rad / s in 2 seconds): α = (0.089 - 0.2) / 2 = - 0.0555 rad / s² Calculate the gravitational moment: M g = 80×9.8×0.6×cos(100°) = - 81.7 N·m Calculate the torque of the push rod motor: M p = 28.8×(- 0.0555) - (- 81.7) = - 1.6 + 81.7 = 80.1 N·m Calculate the output force of the push rod: F p = 80.1 / (0.3×sin(60°)) = 80.1 / (0.3×0.866) = 308.3 N Since the hood angle θ = 100° > 90° at this time and it is in the driving force stage, the push rod needs to provide reverse braking force, so the output braking force is 308.3 N.

[0051] 5. Calculation near the stop position (θ = 108°) When the hood approaches the end position (θ = 108°), the remaining angle is only 2°.

[0052] Calculate the normalized remaining distance: d norm = 2 / 15 = 0.133 Apply the non-linear deceleration function to calculate the target angular velocity: ω = 0.2×(0.133)² = 0.2×0.0177 = 0.0035 rad / s (the angular velocity is reduced to 1.77% of the uniform state) Calculate the gravitational moment: M g = 80×9.8×0.6×cos(108°) = 80×9.8×0.6×(-0.309) = -145.5 N·m Calculate the required angular deceleration (close to stop at this time): α ≈ -0.01 rad / s² Calculate the torque of the push rod motor: M p = 28.8×(-0.01) - (-145.5) = -0.288 + 145.5 = 145.2 N·m Calculate the output force of the push rod: F p = 145.2 / (0.3×sin(60°)) = 145.2 / (0.3×0.866) = 559.0 N Since the hood angle θ = 108° > 90° at this time and it is in the driving force stage, the push rod needs to provide reverse braking force, so the output braking force is 559.0 N.

[0053] Result analysis Through the above detailed calculations, the following conclusions are obtained: Characteristics of the acceleration stage: The push rod force gradually decreases from the initial 1810.6 N to 1775.3 N because as the hood angle increases, the gravitational moment decreases and the resistance to be overcome also decreases. The S-shaped acceleration curve achieves a smooth start. The angular acceleration starts from 0, reaches the maximum value in the middle (t = 1 s), and then returns to 0, avoiding sudden impacts.

[0054] Characteristics of the uniform motion stage: The push rod force decreases significantly as the hood angle increases: 1568.2 N is required at the 30° position, 905.1 N is required at the 60° position, and no thrust is required at the 90° position.

[0055] The telescopic speed of the push rod changes from negative (-0.0164 m / s at θ = 30°) to positive (0.0853 m / s at θ = 60°), indicating that the push rod first contracts and then extends, which is consistent with the geometric relationship of the hood movement.

[0056] Characteristics after crossing the center line: When the hood angle exceeds 90°, the gravitational moment changes from resistance to driving force, and the push rod needs to change from providing thrust to providing braking force.

[0057] At θ = 100°, a braking force of 314.5 N needs to be provided to prevent the hood from moving too fast under the action of gravity.

[0058] Characteristics in the deceleration stage: The braking force increases from 308.3 N to 559.0 N in the deceleration stage because as the hood approaches the end, a greater braking force is required to make it stop smoothly.

[0059] The non-linear deceleration strategy (n = 2) makes the speed decay according to the square relationship of the remaining distance, providing a smooth speed transition.

[0060] System adaptability: During the whole process, the push rod force is dynamically adjusted according to the hood angle, angular velocity and angular acceleration to adapt to the load change.

[0061] When the hood is opened from 0° to 110°, the change range of the push rod force reaches from 1810.6 N to 559.0 N, indicating that the fixed current drive mode cannot meet the requirements.

[0062] Through the implementation of this method, the hood can maintain a stable motion state during the whole opening and closing process, avoiding the phenomena of sudden speed change and jitter. Especially near the end position, the non-linear deceleration strategy effectively avoids mechanical shock. At the same time, the system can automatically adjust the push rod output force according to different angular positions, realizing variable load adaptive control.

Claims

1. A variable load control method for a linear actuator based on torque control of a push rod motor, characterized in that, It includes: Obtain the current flipping angle θ of the hood; Gravitational moment M of the computer hood g , and the gravitational moment is calculated by the following formula: , where m is the mass of the hood, g is the acceleration due to gravity, and L c is the distance from the center of gravity of the hood to the rotation center, and θ is the flipping angle of the hood; Calculate the torque M of the push rod motor according to the acceleration requirement of the hood p : , where I is the moment of inertia of the hood relative to the rotation center, and α is the angular acceleration of the hood; Calculate the push rod output force F based on the torque of the push rod motor p : , where L2 is the length of the push rod force arm and α is the angle between the push rod and the force arm; Substitute the complete formula to obtain the output force of the push rod: ; Judge whether the hood angle exceeds 90°, and determine the output direction of the push rod according to the judgment result: when 0° ≤ θ ≤ 90°, output a positive thrust, and when 90° < θ ≤ 180°, output a reverse braking force; According to the output force of the push rod, generate a corresponding drive current to control the linear actuator to achieve smooth opening and closing of the hood.

2. The linear driver variable load adaptive control method according to claim 1, wherein The angular acceleration α of the hood is calculated by an S-curve: , where ω max is the target constant angular velocity, t acc is the time required to complete the acceleration, and t is the current time.

3. The linear actuator variable load adaptive control method according to claim 1, characterized in that, The moment of inertia I of the hood is calculated by the following formula: , where m is the mass of the hood, and L c is the distance from the center of gravity of the hood to the rotation center.

4. The adaptive control method for variable load of the linear driver according to claim 1, characterized in that, It also includes: Calculate the length L of the push rod according to the current angle θ of the hood p : , where , ; x1, y1 are the coordinates of the hood rotation center; x2, y2 are the coordinates of the fixed end of the push rod, and L1 is the distance from the rotation center to the connection point of the push rod.

5. The adaptive control method for variable load of the linear driver according to claim 1, wherein It also includes: Calculate the telescopic speed v of the push rod p : , where ω is the current angular velocity of the hood and L p is the current length of the push rod.

6. The linear actuator variable load adaptive control method according to claim 1 or 2, characterized in that The target angular velocity ω(t) of the hood during the acceleration phase is calculated by an S-curve: , where ω max is the target constant angular velocity, t acc is the time required to complete the acceleration, and t is the current time.

7. The adaptive control method for variable load of a linear driver according to claim 1, wherein The target angular velocity ω of the hood during the deceleration phase is calculated by the following formula: , where ω max is the angular velocity during uniform motion, d norm is the normalized remaining distance, d norm = θ remain / θ threshold , θ remain is the remaining angle, θ threshold is the deceleration trigger angle threshold, and n is the deceleration curve exponent and n > 1.

8. A linear drive variable load adaptive control system based on the method according to any one of claims 1-7, characterized in that, It includes: An angle sensor for measuring the flipping angle θ of the hood in real time; A controller for calculating the gravity moment based on the input of an angle sensor and the torque of the push rod motor , and calculating the required push rod output force according to the formula ; A linear actuator, including a motor and a telescopic rod, controls the push rod to output a corresponding force according to the drive signal output by the controller to achieve smooth opening and closing of the hood; A built-in travel switch is set inside the linear actuator and is triggered to stop when the hood reaches the limit position, serving as a secondary protection for the angle sensor.

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