A hydraulic motor stepless speed regulation control system and method based on eccentricity inverse calculation

Abstract

The present application belongs to the field of hydraulic transmission and automatic control technology, and discloses a kind of hydraulic motor stepless speed regulation control system and method based on eccentricity inverse calculation.By collecting the angle signal of two swing cylinders, combining the preset geometric position relationship between the center of swing cylinder base and the center of output shaft, the eccentric center position and the actual eccentricity are inversely calculated; the target eccentricity is determined according to the target speed, and the error between the target eccentricity and the actual eccentricity is taken as the control input, the servo valve control quantity is obtained through the PID operation of the controller, the variable executing mechanism is driven to continuously adjust the eccentric mechanism position, so as to realize the continuous change of hydraulic motor displacement and the continuous stepless regulation of speed. The control process can also be combined with zero correction, direction consistency correction, differential filtering, anti-integral saturation, dead zone compensation and output amplitude limiting to improve the speed regulation stability and control accuracy. The present application solves the problems of difficult measurement of internal eccentric mechanism state of hydraulic motor and difficult continuous speed regulation in wide speed range.

Description

Technical Field

[0001] This invention relates to the field of hydraulic transmission and automatic control technology, and in particular to a continuously variable speed control system and method for hydraulic motors based on eccentricity back calculation. Background Technology

[0002] Hydraulic motors are widely used in engineering machinery, mining machinery, marine equipment, and heavy-duty drive systems. For hydraulic drive systems that need to operate under high loads and wide speed ranges, hydraulic motors not only need to have high output torque capabilities, but also good speed regulation performance, especially the ability to achieve continuous, smooth, and controllable stepless speed regulation between the minimum stable speed and the maximum operating speed.

[0003] For variable displacement swing cylinder hydraulic motors, speed regulation essentially relies on the continuous adjustment of the eccentricity. However, the eccentric mechanism is located inside the motor, and due to structural space constraints and harsh working conditions, the actual eccentricity is extremely difficult to measure directly. Traditional open-loop control or indirect control relying solely on the servo piston position is easily affected by hydraulic hysteresis, structural clearances, friction dead zones, and load disturbances, resulting in low displacement control accuracy and difficulty in maintaining smooth switching of dynamic speeds.

[0004] This invention proposes a continuously variable speed control system and method for hydraulic motors based on eccentricity back-calculation. By obtaining the precise actual eccentricity through real-time calculation of the cylinder's attitude, it overcomes the technical bottleneck of unmeasurable internal parameters. This technology not only significantly improves the displacement adjustment accuracy and system stability of the motor under extreme operating conditions, but also provides key technical support for achieving high-efficiency, high-response digital speed regulation in heavy equipment, and has broad industrial application prospects in the field of high-end hydraulic transmission. Summary of the Invention

[0005] The purpose of this invention is to provide a hydraulic motor stepless speed regulation control system and method based on eccentricity back calculation, so as to solve the problems in the prior art that the state of the eccentric mechanism is difficult to obtain accurately, the eccentricity adjustment accuracy is insufficient, and the hydraulic motor is difficult to achieve stable and continuous stepless speed regulation in the entire speed regulation range.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a hydraulic motor stepless speed regulation control system based on eccentricity back calculation, comprising:

[0007] A variable displacement swing cylinder hydraulic motor has an output shaft, an eccentric mechanism, and a variable actuator that is drivenly connected to the eccentric mechanism;

[0008] A servo valve is used to regulate the flow of hydraulic oil to the variable actuator;

[0009] The first angle sensor and the second angle sensor are used to detect the attitude angle information of the two swing cylinders, respectively.

[0010] A speed sensor is used to detect the actual speed of the variable displacement swing cylinder hydraulic motor;

[0011] The controller is connected to the first angle sensor, the second angle sensor, the speed sensor, and the servo valve, respectively.

[0012] The controller is configured to:

[0013] Based on the angle signals collected by the first angle sensor and the second angle sensor, and combined with the preset geometric positional relationship between the center of the two swing cylinder bases and the center of the output shaft, the directional information from the center of the two swing cylinder bases to the eccentric center is determined. The position of the eccentric center is obtained based on the directional information, and the actual eccentricity is calculated.

[0014] Determine the target eccentricity based on the target rotational speed;

[0015] PID calculations are performed based on the eccentricity error between the target eccentricity and the actual eccentricity to obtain the servo valve control quantity and output it to the servo valve;

[0016] The servo valve adjusts the valve core opening, allowing hydraulic oil to enter the corresponding cylinder chamber of the variable actuator through the valve core opening and drive the variable actuator to move. After the variable actuator reaches the corresponding position balance under hydraulic pressure, the eccentricity is continuously adjusted through the transmission connection with the eccentric mechanism to continuously change the displacement of the variable displacement swing cylinder hydraulic motor, thereby realizing stepless speed regulation of the variable displacement swing cylinder hydraulic motor between the lowest stable speed and the highest working speed.

[0017] The controller is configured with the center of the output shaft as the origin. O Establish a two-dimensional coordinate system, and set the center coordinates of the first swing cylinder base as follows: The center coordinates of the second swing cylinder base are The coordinates of the eccentric center are The zero-angle reference direction vectors of the two angle sensors are respectively and Based on the angle values ​​output by the first angle sensor and the second angle sensor α、β Through rotation matrix R( ) Determine the process respectively and Two direction vectors and This leads to two corresponding directional rays. and The eccentricity is determined by the intersection of the two directional rays. The coordinates are determined, and the eccentric center E is moved to the origin. Odistance |OE| As the actual eccentricity e ;

[0018] , , ,

[0019] , ,

[0020] , ;

[0021] in: This is expressed as the angle required by the rotation matrix. Represents the direction vector, which originates from the point... A unit vector pointing in the direction of the eccentric center E. Represents the direction vector, which originates from the point... A unit vector pointing in the direction of the eccentric center E. and These are the positive directions of the first angle sensor angle and the positive directions of the second angle sensor angle, respectively. and Represented as direction vectors scalar parameters and direction vector scalar parameters, and These are the x-coordinate and y-coordinate of the eccentric center E, respectively.

[0022] The variable actuator includes a servo piston and a cylinder housing the servo piston. The servo valve controls the flow of hydraulic oil by adjusting the valve core opening to drive the displacement of the servo piston. The servo piston and the eccentric mechanism are connected by a transmission structure to convert the displacement of the servo piston into a change in the eccentricity of the eccentric mechanism.

[0023] The first angle sensor and the second angle sensor are respectively installed at the two swing cylinders, and are used to detect the angle between the reference line connecting the center of the corresponding swing cylinder base to the center of the output shaft and the line connecting the center of the corresponding swing cylinder base to the eccentric center. α、β Two swing cylinders are arranged at intervals in the circumferential direction of the hydraulic motor so that the two directional rays pointing to the eccentric center, determined based on the included angle, have a preset included angle.

[0024] The controller utilizes α、βBefore the angle signal determines the two directional rays, the angle signal is zero-position correction and direction consistency correction to obtain the effective angle value for eccentricity back calculation; when the absolute value of the included angle between the two directional rays is less than a preset threshold, it is determined that the near parallel condition is met, the eccentricity back calculation is abnormal, and the controller performs abnormal handling. The abnormal handling includes maintaining the actual eccentricity of the previous sampling period and performing amplitude limiting update on the current actual eccentricity.

[0025] The theoretical displacement of the variable displacement swing cylinder hydraulic motor is a function of the eccentricity, satisfying:

[0026] (1)

[0027] in, To match the actual eccentricity e The corresponding theoretical displacement of the hydraulic motor, The diameter of the swing cylinder, The number of cylinders is specified. The controller continuously adjusts the eccentricity to achieve continuous displacement variation, so that the hydraulic motor speed continuously varies between the highest working speed corresponding to the minimum displacement and the lowest stable speed corresponding to the maximum displacement.

[0028] The controller determines the target eccentricity based on the target rotational speed and the preset rotational speed-eccentricity mapping relationship, and the theoretical rotational speed of the hydraulic motor. satisfy:

[0029] (2)

[0030] in, Q To supply the flow rate to the hydraulic motor;

[0031] The preset rotational speed-eccentricity mapping relationship is a theoretical functional relationship that satisfies:

[0032] (3)

[0033] in, K It is a constant related to the oil supply flow rate, cylinder diameter, and number of cylinders. .

[0034] The input quantity for the PID calculation is the eccentricity error between the target eccentricity and the actual eccentricity;

[0035] (4)

[0036] The output is the servo valve control quantity. u(t) And satisfy:

[0037] (5)

[0038] in, For a moment The eccentricity error, For a moment Target eccentricity, This is the proportionality coefficient. The integral coefficient is... These are the differential coefficients. For the time in the integration operation The eccentricity error;

[0039] When performing PID calculations, the controller also performs at least one of output limiting, integral anti-saturation, and dead-zone compensation.

[0040] A stepless speed control method for a hydraulic motor based on eccentricity back calculation, implemented based on the aforementioned stepless speed control system for a hydraulic motor based on eccentricity back calculation, includes the following steps:

[0041] S1. Acquire the angle signals output by the first angle sensor and the second angle sensor. α、β And collect the actual speed signal output by the speed sensor. n ;

[0042] S2. Based on the preset geometric positional relationship between the centers of the two swing cylinder bases and the center of the output shaft, the angle signal is processed to determine the direction information from the centers of the two swing cylinder bases to the eccentric center.

[0043] S3. Determine the position of the eccentric center based on the direction information. E And calculate the actual eccentricity. e ;

[0044] S4. Based on the target rotational speed Determine the target eccentricity ;

[0045] S5. Calculate the target eccentricity. actual eccentricity e Eccentricity error between ;

[0046] S6. The eccentricity error The input is processed by the PID controller to obtain the control quantity of the servo valve. u ;

[0047] S7. Servo valve controller based on servo valve control quantity u Adjusting the servo valve spool opening allows hydraulic oil to enter the corresponding cylinder chamber of the variable actuator through the valve spool opening and drive the variable actuator to operate;

[0048] S8. After the variable actuator reaches equilibrium at the corresponding position under hydraulic pressure, the eccentricity is changed through the transmission connection with the eccentric mechanism. e ;

[0049] S9. By eccentricity e The continuous change of speed allows for continuous variation of the hydraulic motor's displacement, thereby achieving stepless speed regulation between the lowest stable speed and the highest operating speed; based on the actual speed signal n and the target speed... The comparison results determine whether the speed adjustment target has been achieved; if the speed adjustment target has not been achieved, the process returns to steps S1-S8.

[0050] The hydraulic motor achieves continuously adjustable speed by adjusting the eccentricity, with the actual speed... n satisfy:

[0051] (6)

[0052] in, For volumetric efficiency, To match the actual eccentricity e The corresponding actual displacement of the motor.

[0053] The beneficial effects of this invention are:

[0054] This invention combines dual-angle feedback with geometric inverse calculation to achieve real-time acquisition and reconstruction of the internal eccentricity state of a hydraulic motor. It transforms the traditionally difficult-to-measure internal eccentric mechanism position into a calculable and feedback-able control quantity, thereby improving the accuracy and real-time performance of eccentricity identification. Utilizing the attitude angle information of the two swing cylinders, combined with the preset geometric positional relationship between the center of the swing cylinder base and the center of the output shaft, the eccentric center position and actual eccentricity can be calculated inversely, enhancing the perception of the internal variable state of the hydraulic motor and overcoming the problems of difficult direct measurement of eccentricity and insufficient control basis in existing technologies. Using the error between the target eccentricity and the actual eccentricity as the control input, the servo valve output is dynamically adjusted through a PID closed-loop control algorithm, achieving stable and continuous tracking of the target eccentricity by the eccentric mechanism. Finally, relying on the hydraulic balance cooperation between the servo valve and the variable actuator, the eccentricity and displacement are continuously changed, enabling smooth and stable stepless speed regulation of the hydraulic motor between the minimum stable speed and the maximum operating speed, effectively avoiding the mechanical shock caused by discrete speed switching. Attached Figure Description

[0055] Figure 1 This is a block diagram of the principle of a hydraulic motor stepless speed regulation control system based on eccentricity back calculation.

[0056] Figure 2 This is a schematic diagram showing the distribution of the swing cylinder and the installation position of the angle sensor in this invention;

[0057] Figure 3 This is a schematic diagram of the hydraulic principle and mechanical structure of the variable actuator of the present invention;

[0058] Figure 4 This is a diagram illustrating the geometric modeling and coordinate system definition for the inverse calculation of eccentricity in this invention.

[0059] Figure 5 This is the overall logic flowchart of the stepless speed control method of the present invention;

[0060] Figure 6 This is a mapping diagram showing the relationship between the angle sensor output and the minimum eccentricity of the motor in this invention.

[0061] Figure 7 This is a mapping diagram showing the relationship between the angle sensor output and the maximum eccentricity of the motor in this invention.

[0062] Figure 8 This is a comparison chart showing the effect of the PID enhancement stage of this invention on jitter suppression;

[0063] Figure 9 This is a dynamic speed response curve of the present invention under variable speed conditions.

[0064] In the diagram: 1-II cylinders; 2-VII cylinders. Detailed Implementation

[0065] This invention provides a continuously variable speed control system for a hydraulic motor based on eccentricity back calculation, comprising a variable displacement swing cylinder hydraulic motor, a servo valve, a first angle sensor, a second angle sensor, a speed sensor, and a controller. The variable displacement swing cylinder hydraulic motor has an output shaft, an eccentric mechanism, and a variable actuator connected to the eccentric mechanism. The servo valve is used to regulate the flow of hydraulic oil to the variable actuator. The first and second angle sensors are used to detect the attitude angle information of the two swing cylinders, respectively. The speed sensor is used to detect the actual speed of the hydraulic motor. The controller is connected to the first angle sensor, the second angle sensor, the speed sensor, and the servo valve.

[0066] The controller uses angle signals collected by the first angle sensor and the second angle sensor. α、β Based on the preset geometric positional relationship between the centers of the two swing cylinder bases and the center of the output shaft, the directional information from the centers of the two swing cylinder bases to the eccentric center is determined, and the position of the eccentric center is calculated based on the directional information. E Then calculate the actual eccentricity. e ;

[0067] in: α、β These represent the angles of the first angle sensor and the second angle sensor, respectively. EThis represents the position coordinates of the eccentric center in the established coordinate system, specifically expressed as ( ); and These represent the x-coordinate and y-coordinate of the eccentric center E in the established coordinate system, respectively. e This indicates the actual eccentricity of the variable displacement swing cylinder motor, which, depending on the motor model, meets the following requirements. , This indicates the minimum eccentricity of the motor used. This indicates the maximum eccentricity of the motor used. In this embodiment, it satisfies... ;

[0068] Specifically, the controller is configured with the center of the output shaft as the origin. O Establish a two-dimensional coordinate system, and set the center coordinates of the first swing cylinder base as follows: The center coordinates of the second swing cylinder base are The coordinates of the eccentric center are The zero-angle reference direction vectors of the two angle sensors are respectively and Based on the angle values ​​output by the first angle sensor and the second angle sensor α、β Through rotation matrix R( )， Determine the process separately and And pointing to the eccentric center E Two direction vectors and And thus obtain the process and And two rays pointing towards the eccentric center E and The eccentric center is obtained from the intersection of the two directional rays. The coordinates; the eccentric center E is transferred to the origin. O distance |OE| As the actual eccentricity e ;

[0069] in, , , , , , ;

[0070] in: This is expressed as the angle required by the rotation matrix. and These are the positive directions of the first angle sensor angle and the positive directions of the second angle sensor angle, respectively. and Represented as direction vectors scalar parameters and direction vector scalar parameters, and These are the x-coordinate and y-coordinate of the eccentric center E, respectively.

[0071] The first angle sensor and the second angle sensor are respectively installed at the two swing cylinders to detect whether the center of the corresponding swing cylinder base points to the center of the output shaft. O The reference line and the corresponding center of the swing cylinder base point to the eccentric center. E The angle between the lines connecting them α、β Before performing the eccentricity back calculation, the controller can also process the angle signal. α、β Zero-position correction and direction consistency correction are performed to obtain an effective angle value for eccentricity back-calculation. When the absolute value of the angle between the two directional rays is less than a preset threshold (5° in this embodiment), it is determined that the near-parallel condition is met, the eccentricity back-calculation is abnormal, and the controller performs abnormal handling. The abnormal handling includes maintaining the actual eccentricity of the previous sampling period and performing amplitude limiting update on the current actual eccentricity.

[0072] The theoretical displacement of the variable displacement swing cylinder hydraulic motor is a function of the eccentricity, satisfying:

[0073] (7)

[0074] in: Actual eccentricity e The corresponding theoretical displacement of the hydraulic motor, Indicates the diameter of the swing cylinder. Indicates the number of cylinders.

[0075] The controller determines the target eccentricity based on the target rotational speed and the preset rotational speed-eccentricity mapping relationship, and the theoretical rotational speed of the hydraulic motor. Satisfying the flow-displacement relationship:

[0076] (8)

[0077] in, Q To supply the flow rate to the hydraulic motor;

[0078] The target eccentricity and the target rotational speed satisfy a preset rotational speed-eccentricity mapping relationship:

[0079] (9)

[0080] in: K It is expressed as a constant related to the fuel supply flow rate, cylinder diameter, and number of cylinders. .

[0081] Based on the above relationship, the controller continuously adjusts the eccentricity to achieve continuous change in displacement, so that the speed of the hydraulic motor continuously changes between the highest working speed corresponding to the minimum displacement and the lowest stable speed corresponding to the maximum displacement.

[0082] The controller uses the eccentricity error between the target eccentricity and the actual eccentricity as the input for PID control. Let the eccentricity error be:

[0083] (10)

[0084] in: For a moment The eccentricity error, For a moment Target eccentricity, For a moment The actual eccentricity;

[0085] To prevent the control quantity of the servo valve from exceeding the allowable range, suppress integral saturation, reduce the amplification effect of the derivative element on noise, and compensate for the dead zone of the servo valve, the controller also performs output limiting, integral anti-saturation, derivative filtering, and dead zone compensation processing on the servo valve control quantity during PID calculation.

[0086] PID raw output satisfy:

[0087] (11)

[0088] in: For a moment The original output of the PID, This is the proportionality coefficient. For a moment The integral term is output. For a moment The output of the differential term after differential filtering;

[0089] In the controller, let the sampling period be... , No. k The eccentricity error at each sampling time is denoted as Then the original output of the discrete PID is:

[0090] (12)

[0091] in: This is the raw output of the PID in the kth sampling period. ] is the integral term output of the k-th sampling period, and D[k] is the differential term output of the k-th sampling period after differential filtering;

[0092] Due to eccentricity error Derived from signals acquired by angle sensors and geometric inverse calculations, actual signals typically contain measurement noise and high-frequency fluctuations. If ideal differential terms are directly used... This will amplify high-frequency noise, causing high-frequency jitter in the servo valve control quantity, which in turn leads to frequent minute oscillations of the valve core, fluctuations in hydraulic oil flow, and unstable movements of the variable actuator. The differential term after differential filtering... satisfy:

[0093] (13)

[0094] in: Differential term Laplace transform, Eccentricity error Laplace transform, These are the differential coefficients. Let be the time constant of the differential filter, and ;

[0095] Compared with the ideal differential term, the above expression introduces a first-order low-pass filter into the differential term, so that the differential term retains the error change trend information while suppressing the adverse effects of high-frequency noise on the servo valve control quantity.

[0096] Its corresponding time-domain form can be expressed as:

[0097] (14)

[0098] The discrete differential filter form is:

[0099] (15)

[0100] in: ] represents the eccentricity error in the (k-1)th sampling period, and D[k-1] represents the differential term output after differential filtering in the (k-1)th sampling period;

[0101] Differential filtering can reduce the amplification effect of eccentricity error measurement noise in the differential stage, reduce the high-frequency jitter of servo valve control, improve the smoothness of valve core movement, and improve the stability of small-amplitude adjustment of variable actuator near the target eccentricity. It is especially beneficial to the smoothness of stepless speed regulation under low-speed and intermediate-speed conditions.

[0102] When the controller output reaches the limiting boundary, if the error continues to be integrated, the integral term will accumulate, leading to significant overshoot and recovery hysteresis after the system desaturates. Therefore, an inverse integral anti-saturation strategy is adopted, where the integral term satisfies:

[0103] (15)

[0104] in: This is the proportionality coefficient. As an anti-integral saturation coefficient, The control quantity after limiting at time t. The intermediate control quantity after dead zone compensation at time t;

[0105] Its discrete form is:

[0106] (16)

[0107] Where: I[k-1] is the integral term output of the (k-1)th sampling period, This is the control quantity after amplitude limiting in the (k-1)th sampling period. This is the intermediate control quantity after dead zone compensation in the (k-1)th sampling period;

[0108] when When it exceeds the allowable range, The integral term will be suppressed or reversed under the action of the correction term, thereby preventing the integral from continuing to accumulate.

[0109] By using integral anti-saturation processing, the integral cumulative effect when the servo valve enters the saturation region can be reduced, the time required for the system to recover from the saturation state to the normal regulation state can be shortened, the overshoot during the eccentricity adjustment process can be reduced, and the dynamic response quality of the system can be improved.

[0110] To keep the servo valve control output from the controller within the allowable control range of the servo valve, a limiting process is performed on the raw PID output. satisfy:

[0111] (17)

[0112] in, Let be a saturated function, satisfying:

[0113]

[0114] in: x For saturation function sat Input variables, and These are the upper and lower limits of the servo valve control quantity, respectively. Let be the intermediate control quantity after dead zone compensation at time t.

[0115] The corresponding discrete form is:

[0116] (18)

[0117] in: This is the control quantity after limiting in the k-th sampling period. This is the intermediate control quantity after dead zone compensation in the k-th sampling period;

[0118] By limiting the output amplitude, the control quantity can be prevented from exceeding the servo valve drive range, thus preventing excessive deflection of the valve core, hydraulic shock, and instability of the variable actuator, thereby improving the system's operational safety and control stability.

[0119] The servo valve has a certain dead zone. That is, when the control quantity is small, although the valve core receives the control signal, it is not enough to overcome the influence of friction or valve port overlap, resulting in an insignificant change in the valve core opening. This causes the variable actuator to respond sluggishly to small eccentricity errors. Therefore, dead zone compensation is performed on the original PID output.

[0120] The intermediate control quantity after dead-time compensation is: It satisfies:

[0121] (20)

[0122] in: This is the amount of compensation for the dead zone. For a symbolic function, satisfying:

[0123]

[0124] in: y For symbolic functions Input variables;

[0125] The discrete form of the intermediate control quantity after dead-time compensation is:

[0126] (twenty one)

[0127] By adding dead zone compensation in the non-zero control direction This allows the servo valve control quantity to quickly cross the dead zone threshold, thereby improving the valve core's sensitivity and response to small eccentricity errors.

[0128] Dead zone compensation is particularly beneficial for low-speed operation, small eccentricity correction operation, and small error adjustment operation near the target eccentricity. It can effectively improve the problem of non-operation or sluggish response of variable actuators under small signal input, and improve the continuous reachability and adjustment smoothness of intermediate speed points and low speed range during stepless speed regulation.

[0129] Therefore, the final control quantity output by the controller to the servo valve is:

[0130] (twenty two)

[0131] The corresponding discrete form is:

[0132] (twenty three)

[0133] That is, the controller is based on the eccentricity error The original PID output is obtained by combining differential filtering processing. Subsequently, dead-zone compensation was performed on the servo valve based on its characteristics to obtain the compensated control quantity. and to Output limiting is performed to obtain the final control quantity output to the servo valve. Meanwhile, an anti-integral saturation correction term based on amplitude limiting deviation is introduced during the integral term update process.

[0134] After adopting the above processing method, the servo valve control quantity output by the controller can be kept within the effective control range, and the adverse effects of the saturation dead zone on the system regulation performance can be reduced, thereby improving the accuracy of the eccentricity closed-loop control and the stability of the hydraulic motor stepless speed regulation.

[0135] This invention uses two angle sensors to detect the attitude angles of two swing cylinders, and combines the preset geometric position relationship between the center of the swing cylinder base and the center of the output shaft to calculate the position of the eccentric center and the actual eccentric distance. This allows the state of the eccentric mechanism inside the hydraulic motor to be perceived and reconstructed in real time, improving the accuracy of eccentric distance acquisition.

[0136] This invention uses the eccentricity error between the target eccentricity and the actual eccentricity as the control input, and employs a PID controller to output the control quantity of the servo valve to achieve single closed-loop control of the eccentricity. This enables the eccentric mechanism to stably and continuously track the target eccentricity, thereby improving the eccentricity adjustment accuracy and dynamic response performance.

[0137] This invention controls the valve core opening through a servo valve, allowing hydraulic oil to enter the corresponding cylinder chamber of the variable actuator and drive the servo piston to move. After the servo piston reaches the corresponding position balance under the action of hydraulic pressure, the position of the eccentric mechanism is adjusted through the transmission structure, so that the eccentricity can be continuously changed, thereby realizing the continuous change of displacement.

[0138] This invention utilizes the functional relationship between displacement and eccentricity, as well as the correspondence between rotational speed and displacement, to enable the hydraulic motor speed to continuously vary between the highest operating speed corresponding to the minimum displacement and the lowest stable speed corresponding to the maximum displacement, thereby achieving continuous stepless speed regulation of the hydraulic motor, rather than simply switching between a few discrete speed points.

[0139] The embodiments of this application are described in detail below with reference to the accompanying drawings, examples of which are shown in the drawings. This application provides a hydraulic motor stepless speed regulation control system and method based on eccentricity back calculation, to solve the problems of difficulty in accurately obtaining the state of the internal eccentric mechanism of a variable displacement swing cylinder hydraulic motor, insufficient eccentricity adjustment accuracy, and difficulty in achieving stable and continuous stepless speed regulation of the hydraulic motor across the entire speed range.

[0140] The stepless speed control method for a hydraulic motor based on eccentricity back calculation described in this embodiment includes the following steps:

[0141] Acquire angle signals output by the first angle sensor and the second angle sensor. α、β And collect the actual speed signal output by the speed sensor. n ;

[0142] Based on the preset geometric positional relationship between the centers of the two swing cylinder bases and the center of the output shaft, determine the directional information from the centers of the two swing cylinder bases to the eccentric center;

[0143] Determine the position of the eccentric center based on the direction information. E And calculate the actual eccentricity. e ;

[0144] Calculate the eccentricity error between the target rotational speed and the actual eccentricity. ;

[0145] The eccentricity error is input into the PID controller, and the servo valve control quantity is obtained by combining algorithms such as differential filtering, anti-integral filtering, and dead-zone compensation. u ;

[0146] The servo valve spool opening is adjusted according to the control quantity, which drives the variable actuator to move and change the actual eccentricity through the transmission connection. e ;

[0147] Based on the actual eccentricity e The continuous change of speed enables the continuous change of motor displacement, thereby achieving stepless speed regulation of the hydraulic motor between the lowest stable speed and the highest operating speed.

[0148] In a specific example, this invention combines angle sensing feedback, eccentricity inverse calculation geometric model, and enhanced PID control algorithm, and applies it to the variable control of hydraulic motors. This overcomes the obstacle of unmeasurable internal parameters, improves displacement adjustment accuracy, and achieves smooth stepless speed regulation.

[0149] Specifically, Figure 1 For example, a block diagram of the control system principle. Figure 1 As shown, the control method includes the following steps:

[0150] S1. Construct the hardware for the hydraulic motor control system. The system includes a variable displacement swing cylinder hydraulic motor, a servo valve, a first angle sensor, a second angle sensor, a speed sensor, and a controller. The hydraulic motor drives an eccentric mechanism through a variable actuator, changing the eccentricity to adjust the displacement.

[0151] S1.1: In this embodiment, as Figure 2 As shown, the first angle sensor and the second angle sensor are installed at position 1 of swing cylinder II and position 2 of swing cylinder VII, respectively. The first angle sensor and the second angle sensor detect the angle between the reference line connecting the center of the swing cylinder base to the center of the output shaft and the line connecting the center of the base to the eccentric center. α、β .like Figure 3 As shown, the variable actuator includes a servo piston and a cylinder. The servo valve regulates the flow of hydraulic oil to the working chambers on both sides of the servo piston, driving the servo piston to produce displacement. The servo piston converts the displacement into a position change of the eccentric mechanism through a transmission structure, ultimately adjusting the actual eccentricity. e .

[0152] S2. Geometric inverse calculation of actual eccentricity e This includes the following steps:

[0153] S2.1: The controller is configured as follows Figure 4 As shown, with the center of the output shaft as the origin. O Establish a two-dimensional coordinate system, and set the center coordinates of the base of the No. II swing cylinder 1 as follows: The center coordinates of the base of the VII swing cylinder 2 are: The coordinates of the eccentric center are The zero-angle reference direction vectors of the two angle sensors are respectively and Based on the angle values ​​output by the first angle sensor and the second angle sensor α、β Through rotation matrix R( )， Determine the process separately and And two direction vectors pointing to the eccentric center E and And thus obtain the process and And two rays pointing towards the eccentric center E and The eccentric center is obtained from the intersection of the two directional rays. The coordinates; the eccentric center E is transferred to the origin. O distance | OE| As the actual eccentricity e ;

[0154] in, , , , , , ;

[0155] in: This is expressed as the angle required by the rotation matrix. and These are the positive directions of the first angle sensor angle and the positive directions of the second angle sensor angle, respectively. and Represented as direction vectors scalar parameters and direction vector scalar parameters, and These are the x-coordinate and y-coordinate of the eccentric center E, respectively.

[0156] S2.2: The controller utilizes α、β Before determining the two directional rays using the angle signal, the angle signal undergoes zero-position correction and direction consistency correction to obtain the effective angle value for eccentricity inverse calculation. The eccentricity is related to the angle signal. α、β The corresponding mapping relationship is as follows Figure 6 and Figure 7 As shown, the angle signals corresponding to the two predetermined swing cylinders α、β During the movement of the eccentric mechanism, the changes are periodic and continuous, and the pattern of these changes approximates a sinusoidal fluctuation. A phase difference exists between the two angle signals, corresponding to the spatial arrangement of the two predetermined swing cylinders. For different eccentricity values, the angle signals... α、β The fluctuation amplitudes of the angle signal differ, and the larger the eccentricity, the larger the fluctuation amplitude of the angle signal; the smaller the eccentricity, the smaller the fluctuation amplitude of the angle signal. Therefore, the angle signal... α、β The phase relationship can characterize the instantaneous spatial coordinate information of the eccentric center, and its amplitude change can characterize the change in the eccentricity. Furthermore, when the two directional rays satisfy the near-parallel condition, the eccentricity back-calculation is abnormal, and the controller performs anomaly handling. The anomaly handling includes maintaining the actual eccentricity of the previous sampling period and performing amplitude limiting update on the current actual eccentricity.

[0157] S3. Determine the target eccentricity based on the target rotation speed, and implement it according to formula (7)-formula (9).

[0158] According to equation (7), the theoretical displacement of the hydraulic motor varies with the actual eccentricity. e It increases with the increase of the actual eccentricity. e The eccentricity decreases as the actual eccentricity decreases, therefore it can be reduced by continuously adjusting the actual eccentricity. eTo achieve continuous variation of motor displacement.

[0159] According to equation (9), under the condition that the oil supply flow rate is basically constant, the theoretical speed of the hydraulic motor is... actual eccentricity e They are inversely proportional; that is, when the eccentricity increases, the displacement of the hydraulic motor increases and the speed decreases; when the eccentricity decreases, the displacement of the hydraulic motor decreases and the speed increases.

[0160] S4. Calculate the target eccentricity. actual eccentricity e Eccentricity error between .

[0161] S5. Based on eccentricity error PID calculations are performed, and combined with differential filtering, anti-integral saturation, dead-zone compensation, and output limiting, the control input of the servo valve is obtained.

[0162] According to the above implementation method, such as Figure 5 As shown in the overall logic flowchart, the angle signals of the two swing cylinders are used. α、β Based on the preset geometric positional relationship between the center of the cylinder base and the center of the output shaft, the position of the eccentric center is calculated in real time. E and actual eccentricity e This method transforms the state of the eccentric mechanism, which was originally located inside the hydraulic motor and difficult to measure directly, into a feedback quantity that can be sensed in real time and controlled in a closed loop. Furthermore, it utilizes the relationship between the hydraulic motor's displacement, eccentricity, and speed, mapping the target eccentricity to the target speed, and using the error between the target eccentricity and the actual eccentricity as the PID control input. Simultaneously, it introduces enhancement processing such as differential filtering, anti-integral saturation, dead-zone compensation, and output limiting to improve the stability of the servo valve's control quantity. Finally, the servo valve regulates the movement of the variable actuator and continuously changes the eccentricity, causing the hydraulic motor's displacement to change continuously. This achieves smooth, stable, and continuous stepless speed regulation of the hydraulic motor between its lowest stable speed and highest operating speed, avoiding the response lag and mechanical shock caused by traditional discrete speed regulation methods.

[0163] To verify the effectiveness of the control method proposed in this invention, PID simulation experiments of the controller and prototype experiments of the hydraulic motor were conducted. The results are as follows: Figure 8 and Figure 9 As shown. Figure 8 This is a simulation comparison chart showing the effect of the PID enhancement stage of this invention on jitter suppression. Figure 8It can be seen that after a step change in the input, the system output under ordinary PID control exhibits significant overshoot and oscillation, with continuous fluctuations even in the steady-state phase. However, with the enhanced PID control of this invention, the system output can more smoothly approach the target value, the overshoot is significantly reduced, the oscillation decays faster, and the steady-state fluctuation amplitude is also significantly reduced. The simulation results demonstrate that the enhancements introduced in this invention, such as differential filtering, anti-integral saturation, dead-zone compensation, and output limiting, can effectively suppress control quantity jitter and dynamic fluctuations caused by measurement noise, valve core dead zone, control saturation, and hydraulic system nonlinearity, thereby improving the stability of the servo valve control quantity and the quality of the eccentricity closed-loop regulation. Figure 9 The dynamic speed response curve of the prototype under variable speed conditions is shown below. Figure 9 It can be seen that during the switching of multiple target speeds, the actual speed of the hydraulic motor can quickly follow the change of the given speed, achieving a continuous and smooth transition from low speed to medium speed and then to high speed. Although there is a brief dynamic adjustment process during each stage switching, the overall overshoot is small and the recovery is fast. Moreover, the speed fluctuation in the steady state stage remains at a low level, without obvious continuous oscillation or speed regulation instability. This indicates that the present invention obtains the actual eccentricity in real time through dual-angle feedback and eccentricity back-calculation, and performs closed-loop adjustment based on the mapping relationship between the target speed and the target eccentricity. This effectively drives the variable actuator to continuously change the eccentricity, so that the displacement of the hydraulic motor changes continuously, thereby achieving continuous stepless speed regulation. In summary, the experimental analysis shows that the present invention not only verifies the suppression effect of enhanced PID on control quantity jitter and dynamic fluctuations at the control algorithm level, but also verifies the feasibility and effectiveness of the method in a real hydraulic motor system at the prototype level. This allows the variable displacement swing cylinder hydraulic motor to still have good tracking accuracy, adjustment smoothness and stepless speed regulation performance under wide speed range conditions.

[0164] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A continuously variable speed control system for a hydraulic motor based on eccentricity inverse calculation, characterized in that, include: A variable displacement swing cylinder hydraulic motor has an output shaft, an eccentric mechanism, and a variable actuator that is drivenly connected to the eccentric mechanism; A servo valve is used to regulate the flow of hydraulic oil to the variable actuator; The first angle sensor and the second angle sensor are used to detect the attitude angle information of the two swing cylinders, respectively. A speed sensor is used to detect the actual speed of the variable displacement swing cylinder hydraulic motor; The controller is connected to the first angle sensor, the second angle sensor, the speed sensor, and the servo valve, respectively. The controller is configured to: Based on the angle signals collected by the first angle sensor and the second angle sensor, and combined with the preset geometric positional relationship between the center of the two swing cylinder bases and the center of the output shaft, the directional information from the center of the two swing cylinder bases to the eccentric center is determined. The position of the eccentric center is obtained based on the directional information, and the actual eccentricity is calculated. Determine the target eccentricity based on the target rotational speed; PID calculations are performed based on the eccentricity error between the target eccentricity and the actual eccentricity to obtain the servo valve control quantity and output it to the servo valve; The servo valve adjusts the valve core opening, allowing hydraulic oil to enter the corresponding cylinder chamber of the variable actuator through the valve core opening and drive the variable actuator to move. After the variable actuator reaches the corresponding position balance under hydraulic pressure, the eccentricity is continuously adjusted through the transmission connection with the eccentric mechanism to continuously change the displacement of the variable displacement swing cylinder hydraulic motor, thereby realizing stepless speed regulation of the variable displacement swing cylinder hydraulic motor between the lowest stable speed and the highest working speed. The controller is configured with the center of the output shaft as the origin. O Establish a two-dimensional coordinate system, and set the center coordinates of the first swing cylinder base as follows: The center coordinates of the second swing cylinder base are The coordinates of the eccentric center are The zero-angle reference direction vectors of the two angle sensors are respectively and Based on the angle values ​​output by the first angle sensor and the second angle sensor α、β Through rotation matrix R( ) Determine the process respectively and Two direction vectors and This leads to two corresponding directional rays. and The eccentricity is determined by the intersection of the two directional rays. The coordinates are determined, and the eccentric center E is moved to the origin. O distance |OE| As the actual eccentricity e ; ， ， ， ， ， ， ； in: This is expressed as the angle required by the rotation matrix. Represents the direction vector, which originates from the point... A unit vector pointing in the direction of the eccentric center E. Represents the direction vector, which originates from the point... A unit vector pointing in the direction of the eccentric center E. and These are the positive directions of the first angle sensor angle and the positive directions of the second angle sensor angle, respectively. and Represented as direction vectors scalar parameters and direction vector scalar parameters, and These are the x-coordinate and y-coordinate of the eccentric center E, respectively.

2. The hydraulic motor stepless speed regulation control system based on eccentricity back calculation according to claim 1, characterized in that, The variable actuator includes a servo piston and a cylinder housing the servo piston. The servo valve controls the flow of hydraulic oil by adjusting the valve core opening to drive the displacement of the servo piston. The servo piston and the eccentric mechanism are connected by a transmission structure to convert the displacement of the servo piston into a change in the eccentricity of the eccentric mechanism.

3. The hydraulic motor stepless speed regulation control system based on eccentricity back calculation according to claim 1, characterized in that, The first angle sensor and the second angle sensor are respectively installed at the two swing cylinders, and are used to detect the angle between the reference line connecting the center of the corresponding swing cylinder base to the center of the output shaft and the line connecting the center of the corresponding swing cylinder base to the eccentric center. α、β Two swing cylinders are arranged at intervals in the circumferential direction of the hydraulic motor so that the two directional rays pointing to the eccentric center, determined based on the included angle, have a preset included angle.

4. The hydraulic motor stepless speed regulation control system based on eccentricity back calculation according to claim 1, characterized in that, The controller utilizes α、β Before the angle signal determines the two directional rays, the angle signal is zero-position correction and direction consistency correction to obtain the effective angle value for eccentricity back calculation; when the absolute value of the included angle between the two directional rays is less than a preset threshold, it is determined that the near parallel condition is met, the eccentricity back calculation is abnormal, and the controller performs abnormal handling. The abnormal handling includes maintaining the actual eccentricity of the previous sampling period and performing amplitude limiting update on the current actual eccentricity.

5. The hydraulic motor stepless speed regulation control system based on eccentricity back calculation according to claim 1, characterized in that, The theoretical displacement of the variable displacement swing cylinder hydraulic motor is a function of the eccentricity, satisfying: （1） in, To match the actual eccentricity e The corresponding theoretical displacement of the hydraulic motor, The diameter of the swing cylinder, The number of cylinders is specified. The controller continuously adjusts the eccentricity to achieve continuous displacement variation, so that the hydraulic motor speed continuously varies between the highest working speed corresponding to the minimum displacement and the lowest stable speed corresponding to the maximum displacement.

6. The hydraulic motor stepless speed regulation control system based on eccentricity back calculation according to claim 5, characterized in that, The controller determines the target eccentricity based on the target rotational speed and the preset rotational speed-eccentricity mapping relationship, and the theoretical rotational speed of the hydraulic motor. satisfy: （2） in, Q To supply the flow rate to the hydraulic motor; The preset rotational speed-eccentricity mapping relationship is a theoretical functional relationship that satisfies: （3） in, K It is a constant related to the oil supply flow rate, cylinder diameter, and number of cylinders. .

7. A hydraulic motor stepless speed regulation control system based on eccentricity back calculation according to claim 1, characterized in that, The input quantity for the PID calculation is the eccentricity error between the target eccentricity and the actual eccentricity; （4） The output is the servo valve control quantity. u(t) And satisfy: （5） in, For a moment The eccentricity error, For a moment Target eccentricity, This is the proportionality coefficient. The integral coefficient is... These are the differential coefficients. For the time in the integration operation The eccentricity error; When performing PID calculations, the controller also performs at least one of output limiting, integral anti-saturation, and dead-zone compensation.

8. A method for stepless speed regulation control of a hydraulic motor based on eccentricity back calculation, characterized in that, The continuously variable speed control system for hydraulic motors based on eccentricity back calculation as described in any one of claims 1-7 is implemented by the following steps: S1. Acquire the angle signals output by the first angle sensor and the second angle sensor. α、β And collect the actual speed signal output by the speed sensor. n ; S2. Based on the preset geometric positional relationship between the centers of the two swing cylinder bases and the center of the output shaft, the angle signal is processed to determine the direction information from the centers of the two swing cylinder bases to the eccentric center. S3. Determine the position of the eccentric center based on the direction information. E And calculate the actual eccentricity. e ; S4. Based on the target rotational speed Determine the target eccentricity ; S5. Calculate the target eccentricity. actual eccentricity e Eccentricity error between ; S6. The eccentricity error The input is processed by the PID controller to obtain the control quantity of the servo valve. u ; S7. Servo valve controller based on servo valve control quantity u Adjusting the servo valve spool opening allows hydraulic oil to enter the corresponding cylinder chamber of the variable actuator through the valve spool opening and drive the variable actuator to operate; S8. After the variable actuator reaches the corresponding position balance under the action of hydraulic pressure, the eccentricity is changed through the transmission connection with the eccentric mechanism; S9. By eccentricity e The continuous change of speed enables the continuous change of hydraulic motor displacement, thereby achieving stepless speed regulation of the hydraulic motor between the lowest stable speed and the highest operating speed. Based on the actual speed signal n With target speed The comparison results determine whether the speed adjustment target has been achieved; if the speed adjustment target has not been achieved, the process returns to steps S1-S8.

9. The stepless speed control method for a hydraulic motor based on eccentricity back calculation according to claim 8, characterized in that, The hydraulic motor achieves continuously adjustable speed by adjusting the eccentricity, with the actual speed... n satisfy: （6） in, For volumetric efficiency, To match the actual eccentricity e The corresponding actual displacement of the motor.

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