The application discloses an S-shaped speed planning system for liquid shaking control of heavy-load ring rail shuttle vehicles in curve driving

Abstract

The application provides a liquid sway control S-shaped speed planning system suitable for heavy load loop track shuttle vehicle curve driving, relates to the field of electric digital data processing, and comprises a track section perception unit, an S-shaped speed planning unit, a curve differential speed coordination unit, a liquid sway detection unit, a wave height feedback control unit and a ZVD input shaping unit. The track section perception unit identifies track section types in real time and sends switching signals to each unit, the S-shaped speed planning unit generates a seven-section speed curve with continuous jerk, the liquid sway detection unit outputs an equivalent comprehensive wave height, the wave height feedback control unit feeds back a speed correction amount to the S-shaped speed planning unit, the ZVD input shaping unit applies convolution shaping to a speed instruction and updates convolution kernel parameters on line under a curve working condition, and the curve differential speed coordination unit respectively outputs differential speed rotation speed instructions to front and rear shafts according to a curve radius. The application adopts a compound control structure combining feedforward and feedback, and effectively suppresses liquid sway in heavy load liquid goods curve driving.

Description

Technical Field

[0001] This invention relates to the field of electronic digital data processing, and more specifically to a hydraulic sloshing control S-shaped speed planning system suitable for heavy-duty circular rail shuttles traveling on curves. Background Technology

[0002] Heavy-duty circular rail shuttles are automated guided vehicles (AGVs) with their tracks arranged in a closed loop in a plane. Multiple vehicles can operate simultaneously, and they are widely used in industrial logistics and warehousing scenarios for transporting heavy-duty liquid goods. Compared with linear reciprocating shuttles, circular rail shuttles have significant advantages in improving conveying capacity and warehouse space utilization, making them an important development direction for automated warehousing equipment.

[0003] However, liquid sloshing is a common problem during the transportation of heavy-duty liquid cargo. Liquid sloshing refers to the phenomenon where liquid inside a container sloshes under acceleration. This can lead to liquid spillage or cargo instability, or even container tipping, causing property damage and personal injury. Compared to straight-line driving conditions, shuttle vehicles experience both longitudinal acceleration / deceleration inertial forces and lateral centrifugal forces when driving on curves. The direction of liquid sloshing excitation changes from longitudinal to a coupled longitudinal-lateral direction, significantly increasing the difficulty of suppressing liquid sloshing.

[0004] Current research on liquid anti-sloshing control technology mainly focuses on fields such as aerospace, tank trucks, and light packaging conveyor lines, employing methods including container structure optimization, baffle installation, and motion curve design. However, these solutions are all tailored to their specific scenarios, and there is currently no systematic liquid sloshing control solution for the curved driving conditions of heavy-duty industrial circular rail shuttles.

[0005] To address the issue of suppressing high liquid sloshing waves, existing technologies have employed structural anti-sloshing devices. For example, Chinese patent CN115247752A discloses a vibration control device for liquid storage tanks that combines collision energy dissipation and anti-sloshing reduction. Based on the principle of a tuned mass damper, a circular steel plate is suspended above the liquid storage tank cavity, with an additional mass block attached. Under seismic action, the steel plate and mass block oscillate to dissipate vibrational energy, while collisions further dissipate seismic energy, thereby reducing the height of liquid sloshing waves and preventing liquid from impacting the top cover. This solution achieves liquid sloshing suppression by adding a mechanical structure inside the container, and it is effective for fixed-installation large liquid storage tanks under seismic conditions. However, the above solution has the following shortcomings: First, the device relies on the fixed mechanical structure inside the container to function, and the addition of mass blocks will significantly increase the container's weight, making it unsuitable for heavy-duty shuttle scenarios that are sensitive to load. Second, the device is designed for the low-frequency broadband characteristics of seismic excitation, while the hydraulic sloshing excitation during shuttle cornering originates from motion control commands, has clear frequency characteristics and predictable timing patterns, and suppressing the excitation at the source of motion control is a more fundamental and effective approach. Third, the device is a passive control method and cannot adaptively adjust according to the real-time operating status of the shuttle, lacking the ability to switch parameters between cornering and straight-line conditions.

[0006] Existing shuttle control systems typically use trapezoidal velocity curves for motion planning, resulting in abrupt acceleration changes that cause impact excitation to the liquid surface. This leads to limited effectiveness in suppressing liquid sloshing and fails to meet the actual needs of controlling liquid sloshing during heavy-duty liquid cargo travel on curves. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings by proposing a hydraulic sloshing control S-shaped speed planning system suitable for heavy-duty circular rail shuttles traveling on curves.

[0008] The present invention adopts the following technical solution: A liquid sloshing control S-shaped speed planning system suitable for heavy-duty circular rail shuttles traveling on curves includes a track segment sensing unit, an S-shaped speed planning unit, a curve differential speed coordination unit, a liquid sloshing detection unit, a wave height feedback control unit, and a ZVD input shaping unit. Each unit operates in the shuttle's PLC controller. The track segment sensing unit is connected to the shuttle car barcode scanning and positioning system. It reads the absolute position of the shuttle car in real time, identifies the current track segment type and curve curvature radius, and sends a curve preparation signal to each unit when the remaining distance is shortened to the curve preparation distance threshold. After the shuttle car passes the curve apex and enters the straight section, it sends a curve exit signal to each unit. The S-shaped speed planning unit uses the remaining travel distance of the current track segment, the current maximum allowable speed, the maximum acceleration, and the maximum jerk as planning parameters. It outputs speed commands in each sampling period, and the speed curve is divided into seven segments. The jerk is constant within each segment, and the acceleration is continuous without abrupt changes between adjacent segments. After receiving the curve preparation signal, it enters the curve mode and performs curve adaptive adjustment on the planning parameters. The curve differential speed coordination unit outputs differentiated speed commands to the front and rear axle frequency converters respectively based on the curve curvature radius and the current speed command, so that the ratio of the front and rear axle speeds is consistent with the ratio of the inner and outer trajectory lengths of the curve. The liquid sloshing detection unit collects the liquid sloshing state in the container in real time and outputs the equivalent comprehensive wave height to the wave height feedback control unit. The wave height feedback control unit runs a PID control algorithm with the liquid sloshing safe wave height threshold as the set value, and outputs the speed correction amount to the S-shaped speed planning unit. The S-shaped speed planning unit superimposes the speed command and the speed correction amount and outputs them to the ZVD input shaping unit. The ZVD input shaping unit applies ZVD convolution shaping to the received speed command sequence. The shaped speed sequence is then processed by differential operation to obtain acceleration and deceleration commands, which are input together with the shaped speed sequence into the inverter control interface.

[0009] Furthermore, the curve preparation distance threshold is dynamically calculated based on the shuttle's current speed and maximum allowable deceleration to ensure that the shuttle decelerates to the curve's allowable speed just as it reaches the curve entrance.

[0010] Furthermore, the S-shaped speed planning unit performs three parameter adjustments in curve mode: Replace the current maximum permissible speed with the maximum permissible speed for curves determined based on the curve radius of curvature and hydraulic sloshing safety constraints; The time ratio between the acceleration and deceleration phases is extended compared to the linear operating condition. If the equivalent composite wave height exceeds the safety threshold during the constant speed section of the curve, the target speed value of the constant speed section will be further reduced. After the wave height falls back to within the safety threshold, it will be gradually restored to the maximum allowable speed of the curve.

[0011] Furthermore, there is a trigger priority and a collaborative relationship between the adjustments of the three parameters: The maximum speed replacement and the extended deceleration period ratio for curves take effect simultaneously within the same sampling period after receiving the curve preparation signal, with the highest priority. Active speed reduction during constant speed sections is triggered only when the shuttle has entered the constant speed section of the curve and the equivalent composite wave height exceeds the safety threshold, and its priority is lower than the first two items. The constant speed section active deceleration and the speed correction amount output by the wave height feedback control unit are superimposed in the S-shaped speed planning unit and jointly act on the current speed command. The superimposed composite speed command has a lower limit constraint, and the composite speed shall not be lower than the minimum travel speed required to ensure that the shuttle can pass through the curve normally. Once the equivalent composite wave height falls back to within the safety threshold, the target speed value of the constant speed segment gradually rises back to the maximum allowable speed of the curve according to the preset recovery rate, and the speed correction amount is simultaneously returned to zero. Both exit in a smooth manner.

[0012] Furthermore, in the PID control algorithm of the wave height feedback control unit: The proportional term makes the velocity correction amount proportional to the wave height over-limit amplitude; The differential term is adjusted in advance based on the trend of wave height change, and the adjustment amount is increased in advance during the rapid rise of wave height. The integral term eliminates steady-state wave height deviation, and an amplitude limit constraint is set to prevent saturation. When the corner exit signal arrives, the integral term is reset to zero to prevent the integral amount accumulated during the low-speed phase of the corner from causing overshoot during acceleration out of the corner.

[0013] Furthermore, the ZVD input shaping unit uses different convolution kernel parameters for straight-line and curved-line conditions; Under linear operating conditions, the damping period Td and amplitude attenuation coefficient K are set according to the longitudinal excitation frequency calibration results, and the convolution kernel remains unchanged; Under curve conditions, after receiving the curve preparation signal, the ZVD input shaping unit estimates the free sway frequency of the liquid in the lateral direction based on the lateral inner cavity size of the container and the current liquid level depth. The higher the liquid level, the lower the natural frequency, and the wider the lateral inner cavity of the container, the lower the natural frequency. Based on this, the Td and K values ​​are updated and the convolution kernel is regenerated. After receiving the curve exit signal, the convolution kernel is restored to the calibration parameters for the straight-line condition.

[0014] Furthermore, the convolution kernel switching of the ZVD input shaping unit adopts a smooth transition method, which uses a preset number of transition steps to linearly interpolate each coefficient of the convolution kernel from the current working condition value to the target working condition value. The number of transition steps is determined based on the difference between the straight working condition Td and the curved working condition Td. The larger the difference, the more transition steps are required. The switching is completed when all coefficients of the convolution kernel have been linearly interpolated to reach the target operating value, and the equivalent comprehensive wave height change rate is lower than the preset stability judgment threshold within several consecutive sampling periods. If the shuttle triggers a speed correction due to excessive wave height during the transition period, the ZVD input shaping unit will pause the transition process and continue the transition after the speed correction amount returns to zero.

[0015] Furthermore, the S-shaped speed planning unit and the ZVD input shaping unit are connected in series to form a feedforward control channel, which actively suppresses the excitation of the liquid surface from both the speed command generation and shaping levels. The wave height feedback control unit constitutes a feedback control channel to compensate for residual liquid sloshing that the feedforward channel could not completely eliminate in real time. The two work together to form a composite control structure that combines feedforward and feedback.

[0016] The beneficial effects achieved by this invention are: This invention provides an online adaptive update of the convolution kernel parameters of the ZVD input shaping unit for cornering conditions. Existing input shaping techniques typically operate with fixed parameters, designing convolution kernels only for a single excitation frequency. This invention, under cornering conditions, estimates the lateral liquid free sloshing frequency in real time based on the container's lateral internal dimensions and current liquid level depth, dynamically updates the damping period Td and amplitude attenuation coefficient K, and regenerates the convolution kernel. This ensures that the ZVD shaper always matches the actual excitation frequency of the corner, overcoming the problem of a significant decrease in vibration suppression effect caused by fixed-parameter shapers exceeding the robustness tolerance in cornering conditions, and guaranteeing feedforward shaping and vibration suppression throughout the entire cornering process.

[0017] This invention designs a three-pronged adaptive parameter adjustment mechanism for curve conditions within the S-shaped speed planning unit. By replacing the maximum permissible speed with a maximum permissible speed for the curve determined based on the curve's radius of curvature and liquid sloshing safety constraints, the lateral excitation intensity of the curve's centrifugal acceleration on the liquid surface is fundamentally limited. By extending the time ratio between the acceleration and deceleration phases, the impact excitation of the liquid surface by the rate of velocity change at the curve's inlet and outlet is reduced. By actively lowering the target speed value and setting a lower limit constraint on the composite speed when the wave height exceeds the limit during the constant speed phase, the natural decay of liquid sloshing is accelerated while ensuring the normal passage of the shuttle. The three adjustments have clear trigger priorities and synergistic relationships, significantly improving the curve liquid sloshing suppression effect compared to existing trapezoidal speed curves or fixed-parameter S-shaped curve schemes without adding additional mechanical structures.

[0018] This invention connects an S-shaped velocity planning unit and a ZVD input shaping unit in series to form a feedforward control channel, and a wave height feedback control unit to form a feedback control channel, thus creating a composite control structure combining feedforward and feedback. The feedforward channel actively suppresses excitation on the liquid surface from both the velocity command generation and shaping levels, determining the basic level of liquid sloshing suppression; the feedback channel provides real-time compensation for residual liquid sloshing that the feedforward channel cannot completely eliminate, addressing uncertainties caused by deviations in actual operating conditions.

[0019] To further understand the features and technical content of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are for reference and illustration only and are not intended to limit the present invention. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structural framework of the present invention; Figure 2 This is a schematic diagram of the seven-segment division of the S-shaped velocity curve of the present invention; Figure 3 This is a schematic diagram of the adjustment of S-shaped speed planning parameters in the curve mode of the present invention; Figure 4 This is a schematic diagram of the curve parameter switching process of the ZVD shaping unit of the present invention; Figure 5 This is a schematic diagram of the system operation timing of the present invention. Detailed Implementation

[0021] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can understand the advantages and effects of the present invention from the content disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the spirit of the present invention. Furthermore, the accompanying drawings of the present invention are for simple illustrative purposes only and are not depictions of actual dimensions; this is stated beforehand. The following embodiments will further describe the relevant technical content of the present invention in detail, but the disclosed content is not intended to limit the scope of protection of the present invention.

[0022] Example 1.

[0023] This invention provides a hydraulic sloshing control S-shaped speed planning system suitable for heavy-duty circular rail shuttles traveling on curves, combined with... Figure 1 It includes a track segment sensing unit, an S-shaped speed planning unit, a curve differential speed coordination unit, a liquid sloshing detection unit, a wave height feedback control unit, and a ZVD input shaping unit, each of which operates in the shuttle car PLC controller; The track segment sensing unit is responsible for identifying the type of track segment the shuttle is currently in and providing track segment switching trigger signals to other units. It is the prerequisite for the entire system to sense the arrival of a curve and trigger parameter switching of each unit. The track segment sensing unit is connected to the shuttle's barcode scanning and positioning system, reads the absolute position of the shuttle in real time, compares it with the track topology table pre-stored in the PLC, and continuously outputs the current track segment type, the current curve curvature radius, and the remaining distance to the next curve entrance. When the remaining distance is shortened to the curve preparation distance threshold, the track segment sensing unit sends a curve preparation signal to the S-shaped speed planning unit and transmits the current curve curvature radius to the curve differential speed coordination unit. After the shuttle passes the apex of the curve and enters the straight section, the track segment sensing unit sends a curve exit signal to each unit. The curve preparation distance threshold is dynamically calculated based on the shuttle's current speed and the maximum allowable deceleration to ensure that the shuttle completes deceleration to the curve's allowable speed just as it reaches the curve entrance, neither decelerating excessively in advance and losing transportation efficiency, nor traveling at an excessive speed in the curve due to triggering too late.

[0024] The S-shaped speed planning unit is responsible for generating a sequence of speed commands with continuous acceleration and minimal excitation to the liquid surface throughout the entire journey. It is the core feedforward control component for suppressing liquid sloshing in this system. The S-shaped speed planning unit uses the remaining travel distance of the current track segment, the current maximum allowable speed, the maximum acceleration, and the maximum jerk as planning parameters. In each sampling period, it outputs the speed command for the current moment, which is then sent to the ZVD input shaping unit. Figure 2 The velocity curve is divided into seven stages on the time axis: acceleration, uniform acceleration, deceleration, uniform speed, acceleration and deceleration, uniform deceleration and deceleration. The acceleration in each stage is constant, and the acceleration between adjacent stages is continuous without abrupt changes. The continuity of acceleration ensures a smooth transition of the velocity curve and eliminates the impact excitation on the liquid surface caused by acceleration step in the conventional trapezoidal velocity curve. Upon receiving the curve preparation signal, the S-shaped speed planning unit enters curve mode, combined with... Figure 3 Adjust the following three parameters.

[0025] First, the current maximum permissible speed is replaced with the maximum permissible speed for curves. When traveling on a curve, the shuttle is subjected to a lateral centrifugal acceleration that is proportional to the square of its travel speed and inversely proportional to the radius of curvature of the curve. This lateral acceleration constitutes a lateral excitation on the liquid inside the container. The maximum permissible speed for curves is the maximum travel speed that ensures the lateral acceleration does not exceed the liquid sloshing safety threshold. The greater the lateral centrifugal acceleration, the higher the liquid sloshing wave height. The system determines the maximum permissible speed for curves based on the corresponding relationship by looking up a table, so that the lateral acceleration experienced by the shuttle throughout the curve does not exceed the maximum permissible value corresponding to the liquid sloshing safety threshold. The smaller the radius of curvature of the curve, the lower the maximum permissible speed; the larger the radius of curvature of the curve, the higher the maximum permissible speed, approaching the rated speed of the straight section.

[0026] Second, the time ratio between the deceleration and acceleration / deceleration phases is extended. The magnitude of the rate of change of velocity during the deceleration process at the bend entrance and the acceleration process at the bend exit directly determines the instantaneous excitation intensity on the liquid surface. The greater the rate of change of velocity, the more drastic the acceleration change, and the stronger the impact excitation on the liquid surface. In bend mode, the system appropriately extends the time ratio between the deceleration and acceleration / deceleration phases compared to the straight-line operation, making the transition of acceleration from the peak value to zero smoother and reducing the lateral excitation intensity on the liquid surface at the bend entrance and exit.

[0027] Third, if the liquid sloshing detection unit detects that the equivalent composite wave height still exceeds the safety threshold during the constant speed section of the curve, the system further reduces the target speed value of the constant speed section, actively reduces the lateral centrifugal acceleration, and accelerates the natural decay of the liquid sloshing. After the wave height falls back to within the safety threshold, the target speed value of the constant speed section gradually recovers to the maximum allowable speed of the curve.

[0028] There is a clear triggering priority and synergistic relationship among the above three parameter adjustments. The first item, the replacement of the maximum allowable speed in the curve, and the second item, the extension of the deceleration phase time ratio, take effect simultaneously within the same sampling period after receiving the curve preparation signal. Together, they constitute the basic parameter framework of the curve mode and are pre-adjustments that must be completed before entering the curve, with the highest priority. The third item, the active deceleration in the constant speed phase, is only triggered when the shuttle has entered the constant speed phase of the curve and the equivalent comprehensive wave height fed back by the liquid sloshing detection unit exceeds the safety threshold. It is a superimposed compensation measure based on the first two adjustments and has a lower priority than the first two.

[0029] The third item, the active deceleration in the constant speed segment and the speed correction output from the wave height feedback control unit, work together in a superimposed manner within the S-shaped speed planning unit to affect the current speed command. These two items are different in nature and function at different levels, and do not substitute for each other. The correction from the wave height feedback control unit is calculated in real-time by the PID algorithm based on the wave height deviation, resulting in a fast response and affecting the speed command output for each sampling period, representing continuous, fine-grained real-time correction. The active deceleration in the constant speed segment, determined by the S-shaped speed planning unit based on the wave height exceeding the limit, adjusts the overall speed target value of the constant speed segment downwards, affecting the planning benchmark for the entire constant speed segment, representing a coarse-grained, phased adjustment. After the two are superimposed, the wave height feedback correction continues to play a real-time correction role on the new benchmark speed after the active deceleration, ensuring that speed regulation considers both phased stability and fine-grained response at the sampling level.

[0030] When the constant speed section active deceleration and the wave height feedback correction are applied simultaneously, the S-shaped speed planning unit sets a lower limit constraint on the combined speed command after the two are superimposed. The combined speed must not be lower than the minimum travel speed required to ensure that the shuttle can pass through the curve normally. This prevents the two from being superimposed too much, which could cause the shuttle to have too low a speed or even stop in the middle of the curve. When the equivalent combined wave height falls back to within the safety threshold, the speed target value of the constant speed section gradually rises back to the maximum speed allowed for the curve according to the preset recovery rate. The wave height feedback correction is simultaneously returned to zero. Both are withdrawn in a smooth manner to avoid the sudden increase in speed from generating new excitation on the liquid surface.

[0031] Upon receiving the corner exit signal, the S-shaped speed planning unit exits the corner mode, allowing the maximum speed to return to the rated value of the straight section, and replans the acceleration curve. When the wave height feedback control unit outputs the speed correction amount, the S-shaped speed planning unit superimposes the current speed command with the correction amount and outputs it, realizing the real-time intervention of the feedback channel on the feedforward speed command.

[0032] The cornering differential speed coordination unit is responsible for outputting differentiated speed commands to the front and rear axle inverters when traveling on curves, ensuring pure rolling of each traveling wheel and preventing lateral force interference caused by wheel speed mismatch from being superimposed on the hydraulic sloshing excitation. The cornering differential speed coordination unit receives the curve curvature radius transmitted by the track segment sensing unit and the current speed command output by the S-shaped speed planning unit. Based on the geometric relationship between the wheelbase of the shuttle's front and rear axles and the curve curvature radius, it outputs corresponding speed commands to the front and rear axle inverters respectively, so that the ratio of the front and rear axle speeds is consistent with the ratio of the lengths of the inner and outer tracks of the curve. The smaller the curve curvature radius, the greater the speed difference between the front and rear axles; the larger the curve curvature radius, the smaller the speed difference between the front and rear axles, approaching the same speed state when traveling on a straight line. After receiving the curve exit signal, the cornering differential speed coordination unit resumes the same speed output of the front and rear axles.

[0033] The liquid sloshing detection unit is responsible for quantifying the degree of liquid sloshing in the container in real time, providing a continuous and reliable feedback signal to the wave height feedback control unit. The liquid sloshing detection unit adopts different schemes for open and closed heavy-duty containers.

[0034] For open-type heavy-duty containers, an ultrasonic liquid level sensor is installed above each of the four corners of the container to continuously collect the liquid level height at four measuring points: front left, front right, rear left, and rear right. The transverse wave height component and the longitudinal wave height component are extracted by differential operation and synthesized into an equivalent comprehensive wave height output to the wave height feedback control unit.

[0035] For closed-type heavy-duty containers, a weighing sensor is installed at each of the four corners of the bottom of the container. By collecting the uneven distribution of the supporting forces at the four corners in real time, the data is converted into the equivalent liquid surface tilt and then into the equivalent comprehensive wave height output.

[0036] In both scenarios, the detection signals are processed by low-pass filtering to remove high-frequency noise introduced by vehicle vibration. When driving in a curve, the direction of liquid sloshing changes from longitudinal to a coupled longitudinal and transverse direction. The four-point arrangement can simultaneously sense the transverse and longitudinal wave height components, which can more comprehensively reflect the true state of liquid sloshing under curve conditions compared to the scheme that only detects a single direction.

[0037] The wave height feedback control unit is responsible for real-time correction of the speed output of the S-shaped speed planning unit based on the measured liquid sloshing status, forming the feedback control channel of this system. The wave height feedback control unit receives the equivalent composite wave height output from the liquid sloshing detection unit, runs a PID control algorithm with the liquid sloshing safe wave height threshold as the setpoint, and outputs the calculated speed correction to the S-shaped speed planning unit. When the equivalent composite wave height does not exceed the safe threshold, the correction is zero, and the speed operates according to the S-shaped reference curve; when the equivalent composite wave height exceeds the safe threshold, the correction is negative, and the S-shaped speed planning unit issues a speed command. The shuttle decelerates and operates at reduced speed. Once the wave height falls below the threshold, the correction amount is gradually reduced to zero, and the speed returns to the baseline curve value. The proportional term makes the correction amount proportional to the wave height over-limit; the greater the over-limit, the greater the speed reduction. The differential term predicts the wave height change trend and increases the correction amount in advance during the rapid rise of the wave height to prevent the wave height from continuing to climb due to system response lag. The integral term eliminates the steady-state wave height deviation, but has an amplitude limit constraint to prevent saturation. When the corner exit signal arrives, the integral term is reset to zero to prevent the integral amount accumulated in the low-speed phase of the corner from causing overshoot during corner exit acceleration and triggering new hydraulic sloshing excitation.

[0038] The ZVD input shaping unit is responsible for performing feedforward shaping on the speed command sequence output by the S-type speed planning unit, eliminating the continuous excitation of the liquid surface by the residual periodic oscillation component in the speed command. It is the second-stage vibration suppression link of the feedforward control channel of this system. The ZVD shaper consists of three pulses. In the time domain, the shaping process is equivalent to performing a discrete convolution operation between the speed command sequence and the convolution kernel composed of three pulses, and outputting the shaped speed sequence. The amplitude of each pulse and the time interval between adjacent pulses are determined by the liquid free sloshing damping period Td and the amplitude attenuation coefficient K.

[0039] Td is obtained by measuring the time interval between adjacent peaks of the liquid surface response after applying a step excitation to the container, and K is determined by the amplitude of adjacent peaks. , Logarithmic decay rate Calculated using the following formula: ; ; ; The amplitudes A1, A2, and A3 of the three pulses of the ZVD shaper, as well as the time interval, are determined by the following formula: ; ; The convolution kernel is a one-dimensional array whose length is related to the pulse interval. The ZVD shaper convolution kernel has a length of two pulse intervals. The corresponding buffer length must be greater than the number of sampling points corresponding to two pulse intervals. The real-time speed input signal is combined with the ZVD convolution kernel to perform real-time convolution operation. The real-time result is the shaped speed signal. The shaped speed sequence is differentially processed to obtain the acceleration sequence. The positive value part is used as the acceleration command, and the absolute value of the negative value part is taken as the deceleration command. The positive value part and the absolute value of the negative value part are input together with the shaped speed sequence into the inverter control interface. The inverter adjusts the output voltage and frequency to drive the front and rear axle motors to run smoothly according to the shaped speed trajectory.

[0040] Compared to the ZV shaper, the ZVD shaper adds a pulse constraint, making it more robust to deviations in the natural frequency parameters of the liquid. It can still maintain an effective vibration suppression effect when there is a certain deviation between the actual excitation frequency and the shaper's design frequency. However, in the case of curves, the excitation direction of the shuttle to the liquid changes from longitudinal to lateral. The natural frequency of lateral liquid sloshing varies due to the lateral dimensions of the container and the liquid filling depth compared to the longitudinal case. If the convolution kernel parameters calibrated under the straight-line case are still used, the frequency deviation may exceed the robustness tolerance of the ZVD shaper, resulting in a significant decrease in the vibration suppression effect.

[0041] To this end, the ZVD input shaping unit uses different convolution kernel parameters for straight and curved conditions. In the straight condition, Td and K are set according to the longitudinal excitation frequency calibration results, and the convolution kernel remains unchanged. In the curved condition, after receiving the curved preparation signal, the unit re-estimates the transverse liquid free sloshing frequency based on the transverse dimensions of the container and the current liquid level depth, updates the Td and K values ​​accordingly, and regenerates the convolution kernel to ensure that the shaper maintains an effective vibration suppression effect for the actual excitation frequency of the curve. The estimation of the transverse liquid sloshing frequency takes into account factors such as the transverse inner cavity dimensions of the container, the current liquid level height, and the liquid density. The higher the liquid level, the lower the natural frequency; the wider the transverse inner cavity of the container, the lower the natural frequency. Combination Figure 4 The timing of the curve parameter switching is strictly synchronized with the moment when the track segment sensing unit issues the curve preparation signal. The ZVD input shaping unit immediately starts the parameter update process within the current sampling period after receiving the curve preparation signal. Based on the curve curvature radius synchronously transmitted by the track segment sensing unit and the liquid level depth currently output by the liquid sloshing detection unit, the lateral liquid free sloshing frequency is estimated, Td and K values ​​are recalculated, and a curve working condition convolution kernel is generated. The parameter switching is completed within several sampling periods after the curve preparation signal arrives. When the switching is completed, the shuttle is still in the deceleration section before the curve entrance, ensuring that the ZVD shaping unit is fully working under the curve working condition parameters when the shuttle officially enters the curve.

[0042] The convolution kernel switching process employs a smooth transition rather than a direct jump. A direct jump would cause discontinuity in the convolution kernel before and after the switching moment, resulting in a step disturbance in the shaped velocity sequence at the switching point, generating additional excitation on the liquid surface. In the smooth transition mode, after the ZVD input shaping unit completes the parameter update, it linearly interpolates the convolution kernel coefficients from the straight-line condition values ​​to the curve condition values ​​using a preset number of transition steps. During the transition, the convolution kernel coefficients are updated once per sampling period. The number of transition steps is determined based on the difference between the straight-line condition Td and the curve condition Td; the larger the difference, the more transition steps are required. This ensures that the rate of change of the convolution kernel coefficients remains within a range that does not cause abrupt changes in the shaped output. The shaping process is uninterrupted during the transition; each sampling period applies shaping to the velocity command using the convolution kernel in the current transition state, ensuring the continuity of the velocity command output.

[0043] The switching is completed when all coefficients of the convolution kernel have been linearly interpolated to reach the target value for the curve condition, and the equivalent comprehensive wave height change rate output by the liquid sloshing detection unit is lower than the preset stability judgment threshold for several consecutive sampling periods. This indicates that the liquid sloshing state has established a stable response to the convolution kernel for the curve condition. After the above two conditions are met, the ZVD input shaping unit marks the curve parameter switching as complete. Thereafter, the convolution kernel is fixed at the curve condition value until the curve exit signal is received. If the shuttle triggers the speed reduction correction of the wave height feedback control unit due to the wave height exceeding the limit during the transition period, causing the actual travel speed of the shuttle to deviate from the planned speed, the ZVD input shaping unit suspends the transition process, keeps the convolution kernel unchanged in the current transition state, and continues to advance the transition after the wave height correction amount returns to zero and the speed recovers to the planned curve. This prevents the convolution kernel change during the speed disturbance period from being superimposed and amplified by the speed disturbance on the liquid surface.

[0044] The parameter switching when exiting a curve also adopts a smooth transition method. After receiving the curve exit signal, the ZVD input shaping unit uses the same linear interpolation mechanism to transition the convolution kernel from the curve condition value back to the straight condition calibration parameter. The judgment condition for the completion of the transition is the same as that when entering the curve, ensuring that the shaping process of the speed command throughout the acceleration phase of exiting the curve remains continuous and smooth.

[0045] After receiving the curve exit signal, the convolution kernel is restored to the calibration parameters for the straight-line operation.

[0046] Example 2: Combination Figure 5 The following example, using a typical curve passage process, illustrates the signal flow and coordination timing of each unit in this system.

[0047] The shuttle travels along an S-shaped reference speed curve on a straight section. At this time, the S-shaped speed planning unit operates at the rated speed of the straight section as the maximum allowable speed. The ZVD input shaping unit shapes the speed command with a convolution kernel calibrated by the longitudinal excitation frequency. The liquid sloshing detection unit continuously collects the liquid level height at four points and outputs the equivalent comprehensive wave height. The wave height feedback control unit continuously monitors the wave height but the correction amount is zero. The curve differential speed coordination unit outputs the front and rear axle constant speed command. Each unit is in a steady-state operation state on the straight section.

[0048] The track segment sensing unit calculates the remaining distance between the shuttle car and the next curve entrance in real time. When the remaining distance is shortened to the curve preparation distance threshold dynamically calculated based on the current speed and the maximum allowable deceleration, the track segment sensing unit simultaneously sends a curve preparation signal to the S-shaped speed planning unit, transmits the current curve curvature radius to the curve differential speed coordination unit, and sends a curve preparation signal to the ZVD input shaping unit. The three units receive the trigger signal and begin to respond within the same sampling period.

[0049] Upon receiving the curve preparation signal, the S-type speed planning unit immediately replaces the maximum permissible speed with the maximum permissible speed for the curve determined based on the curve curvature radius and liquid sloshing safety constraints. Simultaneously, it switches the time ratio of the acceleration / deceleration phase to the curve mode parameters, replans the deceleration curve according to the new parameters, and outputs a smooth deceleration speed command sequence. Upon receiving the curve preparation signal, the ZVD input shaping unit estimates the lateral liquid free sloshing frequency based on the container's lateral inner cavity dimensions and the current liquid level depth, recalculates Td and K values, and updates the convolution kernel. Subsequently, it applies shaping processing to the speed command sequence output by the S-type speed planning unit with the new convolution kernel. Upon receiving the curve curvature radius, the curve differential speed coordination unit starts outputting differentiated speed commands to the front and rear axle inverters based on the geometric relationship between the front and rear axle wheelbase and the curve curvature radius. The speed difference between the front and rear axles gradually establishes as the shuttle moves, and each traveling wheel enters a pure rolling state.

[0050] After the shuttle enters the curve, the lateral centrifugal acceleration generates a lateral excitation on the liquid surface. The lateral wave height component in the four-point liquid surface height collected by the liquid sloshing detection unit begins to increase, and the equivalent composite wave height rises accordingly. If the equivalent composite wave height does not exceed the safety threshold, the correction amount of the wave height feedback control unit remains at zero, and the S-shaped speed planning unit outputs a speed command according to the curve mode reference curve. The system relies on the S-shaped planning and ZVD shaping of the feedforward channel to maintain liquid sloshing suppression. If the equivalent composite wave height exceeds the safety threshold, the proportional term of the wave height feedback control unit immediately outputs a negative correction amount proportional to the over-limit amplitude, and the differential term is superimposed with the advance correction amount according to the wave height rise rate. The two are combined and output to the S-shaped speed planning unit. The S-shaped speed planning unit superimposes the current speed command and the correction amount and outputs it. The actual travel speed of the shuttle is lower than the given value of the S-shaped reference curve, and the lateral centrifugal acceleration decreases accordingly. The growth of the liquid sloshing wave height is suppressed and begins to fall back.

[0051] If the equivalent composite wave height has not fallen below the safety threshold during the constant speed section of the curve, the S-shaped speed planning unit further reduces the target speed value of the constant speed section. On the basis of the correction amount of the wave height feedback control unit, an additional speed reduction is added to accelerate the natural decay of the liquid sloshing. After the equivalent composite wave height falls below the safety threshold, the correction amount of the wave height feedback control unit is gradually reduced to zero, and the target speed value of the constant speed section is gradually restored to the maximum speed allowed for the curve. The shuttle then resumes operation at the baseline speed of the curve mode.

[0052] After the shuttle passes the apex of the curve, the track segment sensing unit detects the start mark of the straight section and simultaneously sends a curve exit signal to the S-shaped speed planning unit, the curve differential speed coordination unit, and the ZVD input shaping unit. Upon receiving the signal, the S-shaped speed planning unit exits the curve mode, allowing the maximum speed to return to the straight section's rated value. It then plans the acceleration curve according to the new parameters and switches the acceleration / deceleration time ratio back to the straight-line operating parameters to smoothly increase the shuttle speed to the rated speed. Upon receiving the signal, the ZVD input shaping unit restores the convolution kernel to the straight-line operating calibration parameters and continues to apply shaping processing to the acceleration speed command to prevent rapid changes in the speed command during the curve exit acceleration process from generating new longitudinal excitation on the liquid surface. Upon receiving the curve exit signal, the wave height feedback control unit performs an integral term zeroing reset to eliminate the integral amount accumulated in the low-speed phase of the curve and prevent integral residue from causing overshoot during the curve exit acceleration. Upon receiving the signal, the curve differential speed coordination unit gradually returns the front and rear axle speed difference to zero, restoring the constant speed output of the front and rear axles. After all units complete the switching, the system returns to the steady-state operation of the straight section, completing a full curve passage process.

[0053] The content disclosed above is only a preferred and feasible embodiment of the present invention, and is not intended to limit the scope of protection of the present invention. Therefore, all equivalent technical changes made based on the content of the present invention specification and drawings are included within the scope of protection of the present invention. Furthermore, the elements therein can be updated as technology develops.

Claims

1. A hydraulic sway control S-shaped speed planning system suitable for heavy-duty circular rail shuttles traveling on curves, characterized in that, It includes a track segment sensing unit, an S-shaped speed planning unit, a curve differential speed coordination unit, a liquid sloshing detection unit, a wave height feedback control unit, and a ZVD input shaping unit, each of which operates in the shuttle car PLC controller; The track segment sensing unit is connected to the shuttle car barcode scanning and positioning system. It reads the absolute position of the shuttle car in real time, identifies the current track segment type and curve curvature radius, and sends a curve preparation signal to each unit when the remaining distance is shortened to the curve preparation distance threshold. After the shuttle car passes the curve apex and enters the straight section, it sends a curve exit signal to each unit. The S-shaped speed planning unit uses the remaining travel distance of the current track segment, the current maximum allowable speed, the maximum acceleration, and the maximum jerk as planning parameters. It outputs speed commands in each sampling period, and the speed curve is divided into seven segments. The jerk is constant within each segment, and the acceleration is continuous without abrupt changes between adjacent segments. After receiving the curve preparation signal, it enters the curve mode and performs curve adaptive adjustment on the planning parameters. The curve differential speed coordination unit outputs differentiated speed commands to the front and rear axle frequency converters respectively based on the curve curvature radius and the current speed command, so that the ratio of the front and rear axle speeds is consistent with the ratio of the inner and outer trajectory lengths of the curve. The liquid sloshing detection unit collects the liquid sloshing state in the container in real time and outputs the equivalent comprehensive wave height to the wave height feedback control unit. The wave height feedback control unit runs a PID control algorithm with the liquid sloshing safe wave height threshold as the set value, and outputs the speed correction amount to the S-shaped speed planning unit. The S-shaped speed planning unit superimposes the speed command and the speed correction amount and outputs them to the ZVD input shaping unit. The ZVD input shaping unit applies ZVD convolution shaping processing to the received speed command sequence. The shaped speed sequence is then subjected to differential operation to obtain acceleration and deceleration commands, which are input together with the shaped speed sequence into the inverter control interface. The S-shaped speed planning unit performs three parameter adjustments in curve mode: Replace the current maximum permissible speed with the maximum permissible speed for curves determined based on the curve radius of curvature and hydraulic sloshing safety constraints; The time ratio between the acceleration and deceleration phases is extended compared to the linear operating condition. If the equivalent composite wave height exceeds the safety threshold during the constant speed section of the curve, the target speed value of the constant speed section will be further reduced, and the speed will be gradually restored to the maximum allowable speed of the curve after the wave height falls back to within the safety threshold. There is a trigger priority and a collaborative relationship among the adjustments of the three parameters: The maximum speed replacement and the extended deceleration period ratio for curves take effect simultaneously within the same sampling period after receiving the curve preparation signal, with the highest priority. Active speed reduction during constant speed sections is triggered only when the shuttle has entered the constant speed section of the curve and the equivalent composite wave height exceeds the safety threshold, and its priority is lower than the first two items. The constant speed section active deceleration and the speed correction amount output by the wave height feedback control unit are superimposed in the S-shaped speed planning unit and jointly act on the current speed command. The superimposed composite speed command has a lower limit constraint, and the composite speed shall not be lower than the minimum travel speed required to ensure that the shuttle can pass through the curve normally. Once the equivalent composite wave height falls back to within the safety threshold, the target speed value of the constant speed segment gradually rises back to the maximum allowable speed of the curve according to the preset recovery rate, and the speed correction amount is simultaneously returned to zero. Both exit in a smooth manner.

2. The hydraulic sway control S-shaped speed planning system for heavy-duty circular rail shuttles traveling on curves as described in claim 1, characterized in that, The curve preparation distance threshold is dynamically calculated based on the shuttle's current speed and maximum allowable deceleration to ensure that the shuttle decelerates to the curve's allowable speed just as it reaches the curve entrance.

3. The S-shaped speed planning system for hydraulic sway control suitable for heavy-duty circular rail shuttles traveling on curves, as described in claim 2, is characterized in that... In the PID control algorithm of the wave height feedback control unit: The proportional term makes the velocity correction amount proportional to the wave height over-limit amplitude; The differential term is adjusted in advance based on the trend of wave height change, and the adjustment amount is increased in advance during the rapid rise of wave height. The integral term eliminates steady-state wave height deviation, and an amplitude limit constraint is set to prevent saturation. When the corner exit signal arrives, the integral term is reset to zero to prevent the integral amount accumulated during the low-speed phase of the corner from causing overshoot during acceleration out of the corner.

4. The S-shaped speed planning system for hydraulic sloshing control suitable for heavy-duty circular rail shuttles traveling on curves, as described in claim 3, is characterized in that... The ZVD input shaping unit uses different convolution kernel parameters for straight-line and curved-line conditions; Under linear operating conditions, the damping period Td and amplitude attenuation coefficient K are set according to the longitudinal excitation frequency calibration results, and the convolution kernel remains unchanged; Under curve conditions, after receiving the curve preparation signal, the ZVD input shaping unit estimates the free sway frequency of the liquid in the lateral direction based on the lateral inner cavity size of the container and the current liquid level depth. The higher the liquid level, the lower the natural frequency, and the wider the lateral inner cavity of the container, the lower the natural frequency. Based on this, the Td and K values ​​are updated and the convolution kernel is regenerated. After receiving the curve exit signal, the convolution kernel is restored to the calibration parameters for the straight-line condition.

5. The S-shaped speed planning system for hydraulic sway control suitable for heavy-duty circular rail shuttles traveling on curves, as described in claim 4, is characterized in that... The ZVD input shaping unit uses a smooth transition method for switching convolution kernels. The coefficients of the convolution kernel are linearly interpolated from the current working condition value to the target working condition value with a preset number of transition steps. The number of transition steps is determined based on the difference between the straight working condition Td and the curved working condition Td. The larger the difference, the more transition steps are required. The switching is completed when all coefficients of the convolution kernel have been linearly interpolated to reach the target operating value, and the equivalent comprehensive wave height change rate is lower than the preset stability judgment threshold within several consecutive sampling periods. If the shuttle triggers a speed correction due to excessive wave height during the transition period, the ZVD input shaping unit will pause the transition process and continue the transition after the speed correction amount returns to zero.

6. The S-shaped speed planning system for hydraulic sloshing control suitable for heavy-duty circular rail shuttles traveling on curves, as described in claim 5, is characterized in that... The S-shaped speed planning unit and the ZVD input shaping unit are connected in series to form a feedforward control channel, which actively suppresses the excitation of the liquid surface from both the speed command generation and shaping levels. The wave height feedback control unit constitutes a feedback control channel to compensate for residual liquid sloshing that the feedforward channel could not completely eliminate in real time. The two work together to form a composite control structure that combines feedforward and feedback.

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