Stepless speed regulating system for electric hoist

Abstract

The application discloses a stepless speed regulation system for an electric hoist, comprising: a target frequency acquisition module for acquiring a target power supply frequency, a real frequency reading module for reading a real power supply frequency, a frequency curve construction module for constructing a target frequency change curve which is smoothly transitioned between a target timestamp and a current timestamp, a frequency sequence construction module for constructing a stage expected frequency sequence of N discrete timestamps, a voltage vector construction module for constructing a rotating voltage vector sequence, a power pulse generation module for generating six-way power pulses for driving a three-phase inverter, and a hook speed tracking module for making a hook speed of the electric hoist track a set hook target speed; the application can automatically prolong the speed change process under heavy load conditions, effectively avoid overcurrent or stall of the motor due to too fast frequency change, reduce inertia swing of the hook caused by sudden acceleration or deceleration, and reduce the speed regulation jerk feeling under the premise of ensuring safe operation of the electric hoist.

Description

Technical Field

[0001] This invention relates to the field of electric hoist speed regulation, and more specifically to a stepless speed regulation system for electric hoists. Background Technology

[0002] Electric hoists, as a common lifting device, are widely used in factories, warehouses, and construction sites. Their operational safety and smooth operation are of paramount importance. To achieve continuous adjustment of the hook lifting speed, modern electric hoists generally adopt variable frequency speed control technology, which adjusts the rotational speed by controlling the power supply frequency of the three-phase asynchronous motor, thereby changing the linear speed of the drum.

[0003] In existing technologies, frequency converters typically use fixed acceleration / deceleration time parameters (such as preset ramp-up / descend times) to achieve frequency transition. For example, when an operator sets a new target hook speed, the frequency converter transitions from the current frequency linearly or along an S-curve to the target frequency. The time required for the entire process is pre-configured by the user and remains constant during operation.

[0004] However, electric hoists have a wide range of load variations, and the load is suspended, making them extremely sensitive to the smoothness of acceleration and deceleration. Existing variable frequency speed control systems generally use fixed frequency and speed change times, without considering the actual load conditions. Because the speed change time is fixed, under heavy load conditions, the motor needs to output high torque in a short time, resulting in a sudden increase in stator current, which can easily trigger overcurrent protection or cause stalling; while under light load or no load, the excessively rapid frequency changes cause the hook to swing significantly due to inertia, affecting positioning accuracy and posing a collision risk.

[0005] Although some frequency converters can indirectly estimate the load and limit the torque through the output current, the current is affected by factors such as motor parameters and temperature drift, making it difficult to accurately reflect the actual load weight. Furthermore, their control logic is only used to prevent overload and cannot dynamically adjust the speed change time according to the load weight to suppress hook sway. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a continuously variable speed control system for electric hoists, which solves the technical problems mentioned in the background by introducing a dynamic adjustment of the speed change time based on the load weight.

[0007] To achieve the above objectives, the present invention provides the following technical solution: The stepless speed regulation system for electric hoists includes the following application modules. The target frequency acquisition module is used to acquire the target power supply frequency of the electric hoist at the target timestamp; The real frequency reading module is used to read the real power supply frequency of the electric hoist at the current timestamp; The frequency curve construction module is used to construct a target frequency change curve that smoothly transitions between the target timestamp and the current timestamp, based on the target power supply frequency, the actual power supply frequency, and the current load weight of the electric hoist. The frequency sequence construction module is used to construct a stage-expected frequency sequence with N discrete timestamps based on the target frequency change curve. The voltage vector construction module is used to construct a rotating voltage vector sequence based on the desired frequency sequence of the stage. The power pulse generation module is used to perform vector pulse width modulation on the rotating voltage vector sequence to generate six power pulses to drive the three-phase inverter. The hook speed tracking module is used to output the six power pulses to the power module of the frequency converter to drive the three-phase asynchronous motor so that the hook speed of the electric hoist tracks the set target hook speed.

[0008] In some specific embodiments, obtaining the target power supply frequency of the electric hoist at the target timestamp includes: S1-1, Target timestamp on the timeline; S1-2, Obtain the target speed of the hook corresponding to the target timestamp; S1-3. Calculate the target power supply frequency of the electric hoist at the target timestamp based on the target speed of the hook and the preset mechanical transmission parameters. In some specific embodiments, calculating the target power supply frequency of the electric hoist at the target timestamp includes: S1-3-1 Extract the reducer speed ratio and drum circumference from the mechanical transmission parameters; S1-3-2. Calculate the ratio of the reducer speed ratio to the drum circumference to generate the speed conversion coefficient; S1-3-3. Calculate the product of the speed conversion coefficient and the target speed of the hook to generate the actual output speed of the motor; S1-3-4. Look up the table to obtain the slip rate of the motor under operating conditions; S1-3-5. Calculate the synchronous speed of the motor based on the actual output speed and slip of the motor; S1-3-6. Extract the number of motor pole pairs from the mechanical transmission parameters; S1-3-7. Calculate the target power supply frequency based on the number of motor pole pairs and the synchronous speed of the motor; In some specific embodiments, a target frequency change curve that smoothly transitions between the target timestamp and the current timestamp is constructed, including: S3-1. Obtain the current load weight; S3-2. Based on the current load weight, target power supply frequency, and actual power supply frequency, calculate the minimum speed change time required to complete the frequency transition. S3-3. Determine the adaptive proportional coefficient based on the current load weight; S3-4. Multiply the adaptive proportional coefficient by the minimum shift time to determine the actual shift time range; S3-5. Within the actual speed change time interval, construct a target frequency change curve with continuous first derivative and bounded second derivative; wherein, the target frequency change curve includes three adjacent speed change stages, namely, an acceleration stage, a constant speed stage, and a deceleration stage.

[0009] In some specific embodiments, within the actual speed change time interval, a target frequency variation curve with continuous first derivative and bounded second derivative is constructed, including: S3-5a. Divide the actual speed change time interval T into seven consecutive time segments according to the time ratio of 1:2:1:0:1:2:1, which successively constitute the acceleration stage, the constant speed stage and the deceleration stage. S3-5b: During the acceleration phase, the control frequency change rate starts from zero and sequentially goes through a process of linear increase, constant maintenance, and linear decrease until the end frequency of the acceleration phase is reached. S3-5c, During the uniform speed phase, the power supply frequency is kept constant and the frequency change rate is zero. S3-5d, During the deceleration phase, a frequency change rate process that is symmetrically executed in the opposite direction to that during the acceleration phase is performed, so that the frequency smoothly converges to the target power supply frequency.

[0010] In some specific embodiments, based on the target frequency change curve, a stage-expected frequency sequence with N discrete timestamps is constructed, including: S4-1. Within the time interval between the current timestamp and the target timestamp, select N discrete timestamps at equal time intervals; S4-2. Obtain the speed change phase corresponding to N discrete timestamps on the target frequency change curve; S4-3. Substitute the N discrete timestamps into the curve function of the speed change stage to obtain the N stage expected frequencies corresponding to each discrete timestamp. S4-4. Arrange the N stage expected frequencies corresponding to each discrete timestamp in ascending order according to the timestamp sequence to generate the stage expected frequency sequence.

[0011] In some specific embodiments, a rotating voltage vector sequence is constructed based on the desired frequency sequence of the stage, including: S5-1. Based on the preset voltage-frequency ratio, the N stage expected frequencies in the stage expected frequency sequence are mapped to the motor terminal voltages corresponding to the discrete timestamps. S5-2. Taking the current timestamp as the starting point of integration, perform time integration on the expected frequency of the stage represented by the target frequency change curve, and multiply it with the coefficient 2π to obtain the electrical angle corresponding to each discrete timestamp. S5-3. Pair the motor terminal voltage and electrical angle for each of the N discrete time stamps to generate the rotational voltage vector for each of the N discrete time stamps; S5-4. Arrange the rotating voltage vectors in ascending order according to the time sequence of N discrete timestamps to construct a rotating voltage vector sequence.

[0012] In some specific embodiments, the six power pulses are output to the power module of the frequency converter to drive the three-phase asynchronous motor, including: S7-1. Based on the six power pulses, control the inverter power module to apply the rotating voltage vector to the stator winding of the three-phase asynchronous motor to generate three-phase stator current; S7-2. A rotating magnetic field is established based on the three-phase stator current, which is coupled with the rotor induced current to output a continuously adjustable electromagnetic torque. S7-3. The electromagnetic torque drives the motor rotor to rotate, and after being reduced in speed and increased in torque by a reducer, it is transmitted to the drum. S7-4. The drum drives the hook to rise and fall by winding the wire rope, so that the actual hook linear speed tracks the target hook speed in real time.

[0013] This invention provides a stepless speed regulation system for electric hoists, which has the following beneficial effects: This invention dynamically determines the speed change time required for frequency transition based on the current load weight, automatically extending the speed change process under heavy load conditions, effectively avoiding overcurrent or stalling of the motor due to excessively rapid frequency changes; at the same time, under light load or no load conditions, the minimum speed change time is adaptively extended based on the sway suppression requirements, significantly reducing the inertial sway of the hook caused by sudden acceleration and deceleration, thereby reducing the speed regulation jerking sensation while ensuring the safe operation of the electric hoist. Attached Figure Description

[0014] Figure 1 This is a structural block diagram of the stepless speed regulation system for electric hoists of the present invention; Figure 2 This is a schematic diagram of the speed regulation process of the stepless speed regulation system for electric hoists of the present invention. Figure 3 This is a schematic diagram illustrating the calculation process of the target power supply frequency described in this invention; Figure 4 This is a schematic diagram illustrating the construction process of the target frequency variation curve described in this invention; Figure 5 This is a schematic diagram of the process for generating the desired frequency sequence in the stages described in this invention. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Example 1: Please refer to Figures 1 to 2 This invention provides a stepless speed regulation system for electric hoists, including the following application modules: The target frequency acquisition module is used to acquire the target power supply frequency of the electric hoist at the target timestamp; The real frequency reading module is used to read the real power supply frequency of the electric hoist at the current timestamp; The frequency curve construction module is used to construct a target frequency change curve that smoothly transitions between the target timestamp and the current timestamp, based on the target power supply frequency, the actual power supply frequency, and the current load weight of the electric hoist. The frequency sequence construction module is used to construct a stage-expected frequency sequence with N discrete timestamps based on the target frequency change curve. The voltage vector construction module is used to construct a rotating voltage vector sequence based on the desired frequency sequence of the stage. The power pulse generation module is used to perform vector pulse width modulation on the rotating voltage vector sequence to generate six power pulses to drive the three-phase inverter. Specifically, the vector pulse width modulation process includes the following steps: Based on the rotating voltage vector sequence, a vector pulse width modulation (VPWM) method is used to generate six power switch drive pulses to control the six power switches of the three-phase inverter. This modulation process ensures that the fundamental voltage output of the inverter accurately tracks the input rotating voltage vector in both amplitude and phase, thereby enabling the motor stator flux linkage to evolve smoothly along the trajectory planned by the target frequency change curve, achieving shock-free, continuously adjustable speed operation during hook lifting and lowering. In this embodiment, a symmetrical seven-segment spatial vector pulse width modulation strategy based on six-sector division is preferably used for vector pulse width modulation.

[0017] The hook speed tracking module is used to output the six power pulses to the power module of the frequency converter to drive the three-phase asynchronous motor so that the hook speed of the electric hoist tracks the set target hook speed.

[0018] In this embodiment, by sequentially acquiring the target power supply frequency and the current power supply frequency, constructing a target frequency change curve with smooth transition, generating the desired frequency sequence for each stage and the corresponding rotating voltage vector, and outputting six precise timing drive pulses based on vector pulse width modulation, the stator flux of the motor can evolve continuously and without abrupt changes, thereby avoiding mechanical impact caused by speed jumps during hook lifting and lowering, and realizing stepless speed regulation operation of the electric hoist.

[0019] Example 2: See Figures 3 to 5 The technical solution of this embodiment 2 differs from that of embodiment 1 in that it discloses the specific application steps of each application module in embodiment 1.

[0020] Specifically, in this embodiment, the application steps of the target frequency acquisition module are as follows: S1-1, Target timestamp on the timeline; The target timestamp is used to specify the effective time point of the hook speed change.

[0021] S1-2, Obtain the target speed of the hook corresponding to the target timestamp; The target hook speed refers to the expected hook lifting speed at the target timestamp, which serves as the speed command input for the continuously variable speed control system.

[0022] S1-3. Calculate the target power supply frequency of the electric hoist at the target timestamp based on the target speed of the hook and the preset mechanical transmission parameters. The formula for calculating the target power supply frequency is:

[0023] in: Indicates the target power supply frequency. The target speed of the hook is represented by i, the speed ratio of the reducer is represented by P, the number of pole pairs of the motor is represented by d, the drum diameter is represented by S, and the motor slip is represented by a value of 0.02 to 0.05.

[0024] In this embodiment, the target power supply frequency is calculated based on the target speed of the hook and mechanical parameters, so that the frequency command output by the frequency converter matches the actual lifting speed required by the hook, thus avoiding the hook running too fast or too slow due to frequency setting deviation.

[0025] Furthermore, steps S1-3 specifically include: S1-3-1 Extract the reducer speed ratio and drum circumference from the mechanical transmission parameters; Wherein, the speed ratio of the reducer represents the ratio of the speed of the motor input shaft to the speed of the drum output shaft, and the circumference of the drum is the circumference length of the section where the rope is wound on the drum; S1-3-2. Calculate the ratio of the reducer speed ratio to the drum circumference to generate the speed conversion coefficient; S1-3-3. Calculate the product of the speed conversion coefficient and the target speed of the hook to generate the actual output speed of the motor; S1-3-4. Look up the table to obtain the slip rate of the motor under operating conditions; Specifically, slip ratio represents the relative slip ratio between the synchronous speed of the motor and the actual rotor speed. It can be obtained by looking up the current output current amplitude of the inverter through a pre-established load current-slip ratio mapping table.

[0026] S1-3-5. Calculate the synchronous speed of the motor based on the actual output speed and slip of the motor; The formula for calculating the synchronous speed of the motor is: in, Indicates the synchronous speed of the motor. This indicates the actual output speed of the motor. Indicates the slip ratio; Specifically, the synchronous speed of the motor is used to compensate for the speed drop caused by the load, so that the synchronous speed is higher than the actual output speed.

[0027] S1-3-6. Extract the number of motor pole pairs from the mechanical transmission parameters; Specifically, the number of motor pole pairs refers to the number of stator magnetic pole pairs of the motor, which is used to convert synchronous speed into target power supply frequency.

[0028] S1-3-7. Calculate the target power supply frequency based on the number of motor pole pairs and the synchronous speed of the motor; The formula for calculating the target power supply frequency is: ; in, Indicates the target power supply frequency. This indicates the number of pole pairs of the motor.

[0029] In this embodiment, the slip rate is obtained by looking up the table based on the current load current, and the synchronous speed of the motor is corrected accordingly. This ensures that the calculated target power supply frequency can compensate for the speed drop caused by the load and prevent the hook speed from being inconsistent under light and heavy loads.

[0030] Specifically, in this embodiment, the application steps of the frequency curve construction module are as follows: S3-1. Obtain the current load weight; S3-2. Based on the current load weight, target power supply frequency, and actual power supply frequency, calculate the minimum speed change time required to complete the frequency transition. The formula for calculating the minimum speed change time is:

[0031] in, Indicates the minimum shift time. Indicates the target power supply frequency. Indicates the actual power supply frequency. Indicates the current load weight. This is expressed as an equivalent no-load weight offset to avoid a denominator of zero or unstable values. This indicates the maximum permissible rate of change of the reference frequency under no-load conditions.

[0032] Specifically, the frequency change rate represents the first derivative of the power supply frequency with respect to time, and its maximum allowable value decreases as the load weight increases; the minimum speed change time represents the shortest time required to complete the frequency jump without exceeding the maximum allowable frequency change rate under the current load, so as to prevent the motor from stalling or experiencing overcurrent due to excessive frequency change.

[0033] S3-3. Determine the adaptive proportional coefficient based on the current load weight; Specifically, the adaptive proportional coefficient is represented by the time extension factor applied to the minimum speed change time to suppress hook sway, and its value is not less than 1, and it increases with the increase of load weight; Its calculation formula can be expressed as:

[0034] Wherein, α is the preset swing suppression gain, with a value ranging from 0.1 to 0.5.

[0035] S3-4. Multiply the adaptive proportional coefficient by the minimum shift time to determine the actual shift time range; S3-5. Within the actual speed change time interval, construct a target frequency change curve with continuous first derivative and bounded second derivative; wherein, the target frequency change curve includes three adjacent speed change stages, namely, an acceleration stage, a constant speed stage, and a deceleration stage.

[0036] In this embodiment, the minimum speed change time is calculated based on the current load weight, and an adaptive proportional coefficient that increases with the increase of the load is introduced to extend the minimum speed change time to the actual speed change time range. This makes the frequency transition process automatically slow down under heavy load and relatively speed up under light load, which not only avoids the motor from overcurrent or stalling due to excessive frequency change, but also effectively reduces the swing amplitude of the hook caused by inertia during acceleration and deceleration.

[0037] Furthermore, the application steps of steps S3-5 specifically include: S3-5a. Divide the actual speed change time interval T into seven consecutive time segments according to the time ratio of 1:2:1:0:1:2:1, which successively constitute the acceleration stage, the constant speed stage and the deceleration stage. Specifically, the duration of each time segment is as follows: Field 1: =1 / 8T; Field 2: =2 / 8T; Field 3: =1 / 8T; Field 4: = ); Field 5: = ; Field 6: = ; Field 7: = ; S3-5b: During the acceleration phase, the control frequency change rate starts from zero and sequentially goes through a process of linear increase, constant maintenance, and linear decrease until the end frequency of the acceleration phase is reached. Within the first to third sub-segments, the rate of change of frequency starts from 0 and successively goes through the process of "linear increase → constant → linear decrease", completing the acceleration phase; The curve function for the acceleration phase is:

[0038] in, This represents the frequency value at timestamp t during the acceleration phase. This represents the maximum permissible rate of frequency change determined based on the current load weight, and its value satisfies: T represents the actual speed change time interval length; t represents the relative time from the current timestamp, i.e., the timestamp t. S3-5c, During the uniform speed phase, the power supply frequency is kept constant and the frequency change rate is zero. Within the 4th sub-segment, the frequency change rate is 0, and the frequency changes at a constant speed, completing the constant speed phase (if T is large enough, this segment exists; otherwise, it is merged into the adjacent segment). The curve function for the uniform velocity phase is: ; in, This indicates the frequency value at the end of the acceleration phase; S3-5d, During the deceleration phase, the frequency change rate process is symmetrically executed in the opposite direction to the acceleration phase, so that the frequency smoothly converges to the target power supply frequency. Within the 5th to 7th sub-segments, a deceleration process is performed symmetrically to eventually bring the frequency to the target power supply frequency, thus completing the deceleration phase. The curve function for the deceleration phase is: ; in, This represents the frequency value of the deceleration phase at the timestamp. Connect the target frequencies at each timestamp to form a continuous curve, which serves as the target frequency variation curve. The endpoint of this curve equals the target power supply frequency, and the total frequency variation over the entire curve is... Wherein, the maximum value of the frequency change rate does not exceed the maximum permissible frequency change rate.

[0039] In this embodiment, by dividing the actual speed change time interval into seven segments, and symmetrically controlling the frequency change to first rise linearly, then remain constant, and then decrease linearly during the acceleration and deceleration phases, the first derivative of the power supply frequency is continuous and the second derivative is bounded, thereby avoiding sudden changes in the electromagnetic torque of the motor and preventing current surges and mechanical vibrations caused by acceleration jumps.

[0040] Specifically, in this embodiment, the application steps of the frequency sequence construction module are as follows: S4-1. Within the time interval between the current timestamp and the target timestamp, select N discrete timestamps at equal time intervals; S4-2. Obtain the speed change phase corresponding to N discrete timestamps on the target frequency change curve; S4-3. Substitute the N discrete timestamps into the curve function of the speed change stage to obtain the N stage expected frequencies corresponding to each discrete timestamp. The stage expected frequency represents the planned power supply frequency value at the corresponding discrete timestamp on the target frequency change curve, which is used to generate the rotating voltage vector.

[0041] S4-4. Arrange the N stage expected frequencies corresponding to each discrete timestamp in ascending order according to the timestamp sequence to generate the stage expected frequency sequence.

[0042] In this embodiment, by selecting N time points at equal intervals between the current timestamp and the target timestamp, and extracting the corresponding frequency values ​​from the target frequency change curve, a phased expected frequency sequence arranged in chronological order is formed, thereby transforming continuous frequency planning into a set of discrete, ordered, and point-by-point executable frequency instructions.

[0043] Specifically, in this embodiment, the application steps of the voltage vector construction module are as follows: S5-1. Based on the preset voltage-frequency ratio, the N stage expected frequencies in the stage expected frequency sequence are mapped to the motor terminal voltages corresponding to the discrete timestamps. Specifically, the voltage-frequency ratio represents a constant proportionality coefficient between the motor terminal voltage and the power supply frequency, used to maintain constant motor magnetic flux; the motor terminal voltage represents the effective value of the motor terminal voltage amplitude applied to the stator winding of the three-phase asynchronous motor. S5-2. Taking the current timestamp as the starting point of integration, perform time integration on the expected frequency of the stage represented by the target frequency change curve, and multiply it with the coefficient 2π to obtain the electrical angle corresponding to each discrete timestamp. Specifically, the electrical angle represents the rotational phase angle of the motor stator magnetomotive force in space, and its unit is radians; its specific integral calculation formula is: ; in, This represents the accumulated electrical angles from the current timestamp to timestamp t. This represents the angular frequency, i.e., the electrical angular velocity corresponding to the power supply frequency. This represents the expected frequency at any given moment on the target frequency change curve. S5-3. Pair the motor terminal voltage and electrical angle for each of the N discrete time stamps to generate the rotational voltage vector for each of the N discrete time stamps; The rotating voltage vector represents a two-dimensional voltage vector with amplitude (motor terminal voltage) and phase (electric angle) on the complex plane, which is used to drive the three-phase inverter to synthesize the motor terminal voltage.

[0044] S5-4. Arrange the rotating voltage vectors in ascending order according to the time sequence of N discrete timestamps to construct a rotating voltage vector sequence.

[0045] In this embodiment, by converting the desired frequency of each stage into the corresponding motor terminal voltage and combining it with the time integral of that frequency to obtain the electrical angle, each discrete timestamp corresponds to a rotating voltage vector with a definite amplitude and phase, thereby forming a complete rotating voltage vector sequence that describes the spatial trajectory of the stator voltage.

[0046] Specifically, in this embodiment, the application steps of the hook speed tracking module are as follows: S7-1. Based on the six power pulses, control the inverter power module to apply the rotating voltage vector to the stator winding of the three-phase asynchronous motor to generate three-phase stator current; S7-2. A rotating magnetic field is established based on the three-phase stator current, which is coupled with the rotor induced current to output a continuously adjustable electromagnetic torque. Specifically, the electromagnetic torque is generated by the interaction between the stator rotating magnetic field and the rotor induced current, and its magnitude is matched with the desired frequency and load state of the stage to achieve smooth acceleration or deceleration.

[0047] S7-3. The electromagnetic torque drives the motor rotor to rotate, and after being reduced in speed and increased in torque by a reducer, it is transmitted to the drum. Specifically, the reducer converts the high speed and low torque output by the motor into the low speed and high torque required by the drum, and the transmission ratio is determined by preset mechanical parameters.

[0048] S7-4. The drum drives the hook to rise and fall by winding the wire rope, so that the actual hook linear speed tracks the target hook speed in real time.

[0049] In this embodiment, the inverter outputs a three-phase voltage consistent with the rotating voltage vector through a six-channel power pulse control, which enables the electromagnetic torque generated by the motor to change smoothly and be transmitted to the hook through the reducer and drum. This allows the actual lifting speed of the hook to follow the set target linear speed in real time, avoiding overshoot, lag, or jitter. In this embodiment, starting from the target speed of the hook, the power supply frequency calculation, load adaptive speed change time planning, seven-segment smooth frequency curve generation, discrete frequency sequence extraction, rotating voltage vector construction and vector pulse width modulation are completed in sequence. Finally, the drive motor achieves shock-free speed regulation, so that the electric hoist will not cause motor overcurrent or stall due to frequency change during the entire lifting process, nor will it cause large swing of the hook or speed tracking deviation due to excessive acceleration and deceleration.

[0050] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer program are loaded or executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., infrared, wireless, microwave, etc.) means.

[0051] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A stepless speed regulation system for an electric hoist, characterized in that, include: The target frequency acquisition module is used to acquire the target power supply frequency of the electric hoist at the target timestamp; The real frequency reading module is used to read the real power supply frequency of the electric hoist at the current timestamp; The frequency curve construction module is used to construct a target frequency change curve that smoothly transitions between the target timestamp and the current timestamp, based on the target power supply frequency, the actual power supply frequency, and the current load weight of the electric hoist. The frequency sequence construction module is used to construct a stage-expected frequency sequence with N discrete timestamps based on the target frequency change curve. The voltage vector construction module is used to construct a rotating voltage vector sequence based on the desired frequency sequence of the stage. The power pulse generation module is used to perform vector pulse width modulation on the rotating voltage vector sequence to generate six power pulses to drive the three-phase inverter. The hook speed tracking module is used to output the six power pulses to the power module of the frequency converter to drive the three-phase asynchronous motor to run, so that the hook speed of the electric hoist tracks the set hook target speed; Obtaining the target power supply frequency of the electric hoist at the target timestamp includes: S1-1. Select the target timestamp on the timeline; S1-2, Obtain the target speed of the hook corresponding to the target timestamp; S1-3. Calculate the target power supply frequency of the electric hoist at the target timestamp based on the target speed of the hook and the preset mechanical transmission parameters. Construct a target frequency change curve that smoothly transitions between the target timestamp and the current timestamp, including: S3-1. Obtain the current load weight; S3-2. Based on the current load weight, target power supply frequency, and actual power supply frequency, calculate the minimum speed change time required to complete the frequency transition. S3-3. Determine the adaptive proportional coefficient based on the current load weight; S3-4. Multiply the adaptive proportional coefficient by the minimum shift time to determine the actual shift time range; S3-5. Within the actual speed change time interval, construct a target frequency change curve with continuous first derivative and bounded second derivative; wherein, the target frequency change curve includes three adjacent speed change stages, namely, an acceleration stage, a constant speed stage, and a deceleration stage. Within the actual speed-changing time interval, construct the target frequency variation curve with continuous first derivative and bounded second derivative, including: S3-5a. Divide the actual speed change time interval T into seven consecutive time segments according to the time ratio of 1:2:1:0:1:2:1, which successively constitute the acceleration stage, the constant speed stage and the deceleration stage. S3-5b: During the acceleration phase, the control frequency change rate starts from zero and sequentially goes through a process of linear increase, constant maintenance, and linear decrease until the end frequency of the acceleration phase is reached. S3-5c, During the uniform speed phase, the power supply frequency is kept constant and the frequency change rate is zero. S3-5d, During the deceleration phase, the frequency change rate process is symmetrically executed in the opposite direction to the acceleration phase, so that the frequency smoothly converges to the target power supply frequency. Based on the expected frequency sequence of the stage, a rotating voltage vector sequence is constructed, including: S5-1. Based on the preset voltage-frequency ratio, the N stage expected frequencies in the stage expected frequency sequence are mapped to the motor terminal voltages corresponding to the discrete timestamps. S5-2. Taking the current timestamp as the starting point of integration, perform time integration on the expected frequency of the stage represented by the target frequency change curve, and multiply it with the coefficient 2π to obtain the electrical angle corresponding to each discrete timestamp. S5-3. Pair the motor terminal voltage and electrical angle for each of the N discrete time stamps to generate the rotational voltage vector for each of the N discrete time stamps; S5-4. Arrange the rotating voltage vectors in ascending order according to the time sequence of N discrete timestamps to construct a rotating voltage vector sequence; The six power pulses are output to the power module of the frequency converter to drive the three-phase asynchronous motor, including: S7-1. Based on the six power pulses, control the inverter power module to apply the rotating voltage vector to the stator winding of the three-phase asynchronous motor to generate three-phase stator current; S7-2. A rotating magnetic field is established based on the three-phase stator current, which is coupled with the rotor induced current to output a continuously adjustable electromagnetic torque. S7-3. The electromagnetic torque drives the motor rotor to rotate, and after being reduced in speed and increased in torque by a reducer, it is transmitted to the drum. S7-4. The drum drives the hook to rise and fall by winding the wire rope, so that the actual hook linear speed tracks the target hook speed in real time.

2. The stepless speed regulation system for electric hoists according to claim 1, characterized in that, The calculation of the target power supply frequency of the electric hoist at the target timestamp includes: S1-3-1 Extract the reducer speed ratio and drum circumference from the mechanical transmission parameters; S1-3-2. Calculate the ratio of the reducer speed ratio to the drum circumference to generate the speed conversion coefficient; S1-3-3. Calculate the product of the speed conversion coefficient and the target speed of the hook to generate the actual output speed of the motor; S1-3-4. Look up the table to obtain the slip rate of the motor under operating conditions; S1-3-5. Calculate the synchronous speed of the motor based on the actual output speed and slip of the motor; S1-3-6. Extract the number of motor pole pairs from the mechanical transmission parameters; S1-3-7. Calculate the target power supply frequency based on the number of motor pole pairs and the synchronous speed of the motor.

3. The stepless speed regulation system for electric hoists according to claim 1, characterized in that, Based on the target frequency variation curve, construct a stage-expected frequency sequence with N discrete timestamps, including: S4-1. Within the time interval between the current timestamp and the target timestamp, select N discrete timestamps at equal time intervals; S4-2. Obtain the speed change phase corresponding to N discrete timestamps on the target frequency change curve; S4-3. Substitute the N discrete timestamps into the curve function of the speed change stage to obtain the N stage expected frequencies corresponding to each discrete timestamp. S4-4. Arrange the N stage expected frequencies corresponding to each discrete timestamp in ascending order according to the timestamp sequence to generate the stage expected frequency sequence.

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