GA-RK-based fast vertical lifting method for electric cylinder

Abstract

The application provides a GA-RK-based quick vertical lifting method of an electric cylinder, which divides the vertical lifting process of the electric cylinder into four stages: a constant torque control electric cylinder is used for vertical lifting in the vertical lifting starting stage; the initial vertical lifting angle and the vertical lifting angular velocity are the vertical lifting angle and the vertical lifting angular velocity corresponding to the last point of the constant torque stage, the motor rotating speed is calculated, when the motor power reaches the rated power of the motor, a constant power control electric cylinder is used for vertical lifting, when the motor rotating speed reaches the rated rotating speed of the motor, a constant rotating speed control electric cylinder is used for vertical lifting, then a uniform deceleration mode is used to control the electric cylinder for deceleration until the electric cylinder stops, and the time of the deceleration stage is obtained. In the whole planning process, the electric cylinder pushes the load according to the four stages of constant torque, constant power, constant rotating speed and uniform deceleration, and fitting transition stages are added in each stage, so that the shaking and impact of the load are reduced, and the total vertical lifting time can be reduced under the same motor condition.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electric cylinder erecting, and particularly relates to a fast erecting method of electric cylinder based on GA-RK. BACKGROUND

[0002] With the rapid development of science and technology, electric cylinders are widely applied in transmission equipment and transportation equipment. The electric cylinder is generally used as a supporting, transporting and erecting device in military equipment. Compared with a hydraulic cylinder, the electric cylinder has no oil tank and hydraulic pipeline, and has no leakage phenomenon and good environmental protection performance. A multi-stage electric cylinder has no stage change impact and relatively stable movement.

[0003] At present, the erecting method of the electric cylinder in the erecting field is as follows: constant acceleration acceleration lifting, constant speed uniform lifting, constant acceleration deceleration braking and stopping. The erecting method has the following disadvantages.

[0004] 1. Insufficient utilization of the motor

[0005] When the traditional erecting method is used for erecting, the motor uses the maximum power for about 5% of the total erecting time, and the motor power is less than 50% of the maximum power for the rest of the time.

[0006] 2. Too large impact in each stage

[0007] When the traditional erecting method is used for erecting, there is a process of instantaneously changing the acceleration from a relatively large value to 0 between the constant acceleration stage and the uniform speed stage, which will cause a large impact, and even cause damage to the entire electric cylinder structure. SUMMARY

[0008] The purpose of the application is to provide a fast erecting method of electric cylinder based on GA-RK to improve the power utilization rate of the motor and reduce the maximum power of the motor.

[0009] The technical solution for achieving the purpose of the application is as follows:

[0010] A fast erecting method of electric cylinder based on GA-RK divides the electric cylinder erecting process into four stages.

[0011] The constant torque control electric cylinder is used in the erecting starting stage: the erecting angle angleS in the constant torque stage is determined, the erecting speed is angleV, the erecting angle acceleration angleA and the erecting time angle time, and the corresponding motor power is closest to the erecting time of the rated power of the motor power, and the erecting end time of the constant torque stage is taken as the torque time.

[0012] Then the constant power control electric cylinder is used to erect, the initial erecting angle and erecting angular velocity are the erecting angle and erecting angular velocity corresponding to the last point of the constant torque stage, the motor speed is calculated, and the erecting time corresponding to the motor power closest to the motor rated speed speed is taken as the erecting end time powertime of the constant power stage;

[0013] When the motor speed reaches the motor rated speed, the constant speed control electric cylinder is used to erect, the initial erecting angle and erecting angular velocity are the erecting angle and erecting angular velocity corresponding to the state at the end of the previous stage (the constant power stage), the erecting angle of the constant speed stage is calculated angleS, and the erecting time corresponding to the erecting angle closest to the rated deceleration angle slowangle is taken as the erecting end time speedtime of the constant speed stage.

[0014] Then the uniform deceleration mode is used to control the electric cylinder to decelerate until the electric cylinder stops.

[0015] Compared with the prior art, the present application has the following advantages:

[0016] The erecting method provided by the present application increases the maximum power utilization time of the motor to 30-40% of the total erecting time, and the erecting method can smoothly fit between stages, and the load angle acceleration obtained after fitting has no discontinuous points, ensuring smooth transmission.

[0017] The present application realizes overall planning of the erecting time under the conditions of variable hinge point, variable electric cylinder parameters, variable load angle, etc., and can also plan the positions of the hinge point of the electric cylinder, the lead of the screw rod, the reduction ratio of the gear box, and the reduction ratio of the speed reducer. During the entire planning process, the electric cylinder pushes the load according to four stages of constant torque, constant power, constant speed, and uniform deceleration, and a fitting transition stage is added in each stage, which reduces the shaking and impact of the load and reduces the total erecting time under the same motor condition. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The flowchart of each stage of the electric cylinder erecting.

[0019] Figure 2 The schematic diagram of the electric cylinder erecting.

[0020] Figure 3 The S-curve erecting planning diagram.

[0021] Figure 4 The GA-RK curve erecting planning diagram. DETAILED DESCRIPTION

[0022] The application will be further described below in conjunction with the drawings and specific embodiments.

[0023] The electric cylinder rapid erecting method provided by the embodiment adopts a motor, a reducer, a gear box and a screw rod drive. Figure 1 Figure 1 The Runge-kutta method is referred to as RK method. The electric cylinder rapid erecting method based on GA-RK provided by the embodiment comprises the following steps.

[0024] Step one, erecting a motion planning system of the electric cylinder, determining the erecting angle and deceleration angle of the load, determining the mass of the load, determining the rated torque, rated speed and rated power of the motor and other parameters, and determining the efficiency of each link. The parameters involved in this step are shown in Table 1.

[0025] Table 1. Parameter table involved in step one

[0026] Parameter Unit Parameter Description g0x, g0y mm Horizontal and vertical coordinates of the load mass center angle rad Lifting angle loadmass kg Load mass djs Number of motors providing mechanical energy in a single electric cylinder dgs Number of electric cylinders in the lifting system torque Nm Rated torque of the motor power kW Rated power of the motor speed rpm Rated rotating speed of the motor slowangle rad Pre-set deceleration angle n1 Friction efficiency n2 Multi-cylinder synchronization efficiency n3 Motor efficiency n4 Driver efficiency n5 Decelerator efficiency n6 Gearbox efficiency n7 Lead screw pair efficiency n8 Other efficiency (power loss due to incomplete coaxiality of lead screw, push rod, etc.)

[0027] Step two, confirming the parameters to be optimized (the upper and lower hinge point positions of the electric cylinder, the reduction ratio of the reducer, the reduction ratio of the gear box and the total lead of the screw rod). If optimization is needed, the upper and lower limit ranges of the parameters to be optimized are given. If optimization is not needed, a certain value of the parameters to be optimized is given.

[0028] Note: Figure 2 In the Runge-kutta method, the rotation point of the load in the erecting system is taken as the origin, the right direction is taken as the positive direction of the x-axis, and the upward direction is taken as the positive direction of the y-axis to determine the coordinate system, and the position parameters are determined according to the coordinate system. The parameters involved in this step are shown in Table 2.

[0029] Table 2. Parameter table involved in step two

[0030]

[0031] In the table, Value = 0 indicates that the parameter does not need to be optimized, Value = 1 indicates that the parameter needs to be optimized, and min and max indicate the lower limit value and the upper limit value of the corresponding parameter. For example, downxmin and downxmax indicate the lower limit value and the upper limit value of the horizontal coordinate downx of the lower hinge point of the electric cylinder.

[0032] Step three, importing the above parameters into a computer to perform initial condition calculation. The erecting schematic diagram is shown in Figure 2

[0033] The detailed steps are as follows:

[0034] A. Determining the distance og0 between the mass center of the load and the rotation point and the angle beta2 between the line connecting the mass center and the rotation point and the x-axis:

[0035] ​​(Note: og0 is in m, so divide the result by 1000; the angle is taken as the positive angle)

[0036]

[0037]

[0038] B. Treat the load as a uniform density circular rod to determine the moment of inertia of the load, Jload:

[0039] (Note: If the moment of inertia is known, a more accurate value can be provided)

[0040]

[0041] C. Calculate the distance from the lower and upper hinge points of the electric cylinder to the pivot point in the initial state, oup0 and odown, calculate the initial length of the electric cylinder when it is erected, downup0, and calculate the angle between the line connecting the lower and upper hinge points and the pivot point in the initial position, beta1:

[0042] (Note: oup0 and odown are in m, so divide the result by 1000)

[0043]

[0044]

[0045]

[0046]

[0047] D. Set the erecting angle as angleS, the erecting angular velocity as angleV, and the erecting angular acceleration as angleA, and calculate the length downup when the angle is erected:

[0048] (Note: angleS is in rad, angleV is in rad / s, and angleA is in rad / (s^2))

[0049]

[0050] E. Calculate the gravitational moment Mgravity and the force arm forcearm:

[0051] Mgravity = loadmass x 9.8 x og0 x cos(beta2 + angleS) (9)

[0052]

[0053] Table 3: Parameters involved in step three

[0054] Parameter Unit Parameter Description og0 m Distance between load mass center and rotation point oup0 m Distance between upper hinge point of electric cylinder and rotation point in initial state odown m Distance between lower hinge point of electric cylinder and rotation point downup0 m Initial length of electric cylinder downup m Length of electric cylinder after lifting a certain angle Jload kgm^2 Rotational inertia of the load beta1 rad Angle between upper and lower hinge points of electric cylinder and the line connecting them to the rotation point beta2 rad Angle between the line connecting the load mass center and the rotation point and the x-axis (take the positive angle) Mgravity Nm Torque of the load gravity around the rotation point forcearm m Distance between the rotation point and the line on which the output of the electric cylinder is located

[0055] Step four, use RK method to plan each stage. Detailed steps are as follows:

[0056] A. Use RK method to plan constant torque stage:

[0057] Calculate total torque T that system can provide in constant torque stage and vertical angle acceleration angle A under constant torque condition:

[0058] (Note: the unit of total torque T is Nm)

[0059]

[0060]

[0061] Determine initial vertical angle degree and vertical angle velocity as 0, determine vertical planning time as a large value, use ode45 function to control vertical angle acceleration equal to the value corresponding to formula (12), get vertical angle degree angle S, vertical angle velocity angle V, and the relationship matrix of vertical angle acceleration angle A and vertical time angle time in constant torque stage.

[0062]

[0063] According to the above relationship, determine the corresponding motor power Pst (standard power, unit: kW), take the vertical time corresponding to the motor power closest to the rated power of the motor as the vertical end time of the constant torque stage:

[0064] B. Use RK method to plan constant power stage:

[0065] Calculate total power P that system can provide in constant power stage and vertical angle acceleration angle A under constant power condition:

[0066] (Note: the unit of total power P is kW)

[0067] P = power × djs × dgs × 1000 × n1 × n2 × n4 × n5 × n6 × n7 × n8 (14)

[0068]

[0069] The initial erecting angle and erecting speed are determined as the erecting angle and erecting speed corresponding to the last point of the constant torque phase at the end of the last phase (the constant torque phase), the erecting planning time is determined as a large value, the ode45 function is used to control the erecting angle acceleration to be equal to the value corresponding to formula (15), and the relationship matrix of the erecting angle angleS, the erecting speed angleV, the erecting angle acceleration angleA and the erecting time angletime in the constant power phase is obtained.

[0070]

[0071] The corresponding motor speed nst (standard speed, unit: rpm) is determined according to the above relationship, and the erecting time corresponding to the motor power closest to the rated speed speed of the motor is taken as the erecting end time powertime in the constant power phase.

[0072] C. The RK method is used to plan the constant speed phase:

[0073] The relationship of the erecting angle acceleration angleA and the erecting angle angleS, the erecting speed angleV under the condition of constant speed is calculated:

[0074]

[0075] The initial erecting angle and erecting speed are determined as the erecting angle and erecting speed corresponding to the last point of the constant power phase at the end of the last phase (the constant power phase), the erecting planning time is determined as a large value, the ode45 function is used to control the erecting angle acceleration to be equal to the value corresponding to formula (17), and the relationship matrix of the erecting angle angleS, the erecting speed angleV, the erecting angle acceleration angleA and the erecting time angletime in the constant speed phase is obtained. The erecting end time speedtime in the constant speed phase is determined as the erecting time closest to the rated deceleration angle slowangle obtained from angleS.

[0076] D. The deceleration phase is planned:

[0077] The planning is carried out in a uniform deceleration manner, the current erecting angle (denoted as angleS3) and the current erecting speed (denoted as angleV3) are obtained according to step C, the deceleration phase time slowtime and the erecting angle acceleration angleA are calculated, and then the total time totaltime is obtained:

[0078]

[0079]

[0080] totaltime = slowtime + speedtime (20)

[0081] E. Fit the points between each stage:

[0082] Delete the end part of the last stage and the beginning part of the next stage, and use S-shaped curve (uniform acceleration, uniform speed, uniform deceleration) to fit. After fitting, splice the vertical angle angleS, vertical angle velocity angleV and vertical angle acceleration angleA of each stage to get the planning result and total vertical time in the total vertical process.

[0083] Table 4 Step four target parameter table

[0084] Parameter Unit Parameter Description torquetime s End time of constant torque phase powertime s End time of constant power phase, including constant torque phase time speedtime s End time of constant speed phase, including constant torque and constant power phase time slowtime s Total time of deceleration phase totaltime s Total lifting time angletime s Lifting time angleS rad Lifting angle angleV rad / s Lifting angular velocity angleA rad / s^2 Lifting angular acceleration

[0085] Step five, the computer uses GA method to optimize the total vertical time.

[0086] GA method is a genetic algorithm, which is a computational model simulating the natural selection and genetic mechanism of Darwin's biological evolution theory. It is a method of searching for optimal solution by simulating the natural evolution process.

[0087] A. According to step two, determine the parameters to be optimized, determine the number of optimized parameters nvars and the upper and lower limit range of parameters;

[0088] B. Use GA method to optimize and find the optimal solution.

[0089] GA method is a genetic method, taking total vertical time totaltime as fitness parameter, importing GA toolbox after determining each optimization parameter, and the toolbox uses the following code:

[0090] [x, totaltime] = ga (@timecalculate, nvars, [], [], [], [], lb, ub); (21)

[0091] Where:

[0092] x ----- the optimization parameter matrix composed of the optimal solution of each optimization parameter;

[0093] timecalculate ----- the function of calculating the total vertical time;

[0094] totaltime ----- the optimized total vertical time;

[0095] nvars ----- the number of optimized parameters;

[0096] [], [], [], []-----nonlinear constraints and linear constraints (Note: there are no nonlinear constraints and linear constraints in this example);

[0097] lb-----lower limit value of the optimization parameter;

[0098] ub-----upper limit value of the optimization parameter.

[0099] The optimal parameter value is iterated according to the method.

[0100] Step six, repeat step four using the optimal parameter value to plan the vertical lifting, and obtain the optimal control signal.

[0101] Step seven, start power supply, and calculate the control electric cylinder according to the optimal control signal. The computer can read each parameter in real time to calculate the parameters of the motor and electric cylinder, and form a pattern.

[0102] Using S-curve (conventional method) and GA-RK curve (method of the present application) to simulate the example in Table 5, and compare the minimum vertical lifting time.

[0103] Parameters in the example in Table 5

[0104] Parameter Unit Parameter Value g0x, g0y mm -3000,0 downx, downy mm -2500,-1000 up0x, up0y mm -6000,-600 pitch mm 40 angle rad 1.5708(90°) loadmass kg 20000 djs 4 dgs 1 torque Nm 54 power kW 8.5 speed rpm 3175 slowangle rad 1.5359(88°) n1 0.97 n2 0.9 n3 0.95 n4 0.96 n5 0.88 n6 0.95 n7 0.95 n8 0.95

[0105] The results obtained by simulation are: the total vertical lifting time of S-curve is about 50 seconds, as shown in Figure 3 ; the total vertical lifting time of GA-RK curve is about 44 seconds, as shown in Figure 4 .

Claims

1. A GA-RK-based fast vertical lifting method for an electric cylinder, characterized by, The erecting process of the electric cylinder is divided into four stages: The constant torque control electric cylinder is used in the initial stage of erecting: the erecting angle angleS, the erecting speed angleV, the erecting angle acceleration angleA and the erecting time angleTime are determined, the erecting time corresponding to the motor power closest to the rated power power is taken as the erecting end time torquetime of the constant torque stage; Then the constant power control electric cylinder is used for erecting, the initial erecting angle and the erecting angle speed are determined as the erecting angle and the erecting angle speed corresponding to the last point of the constant torque stage, the motor speed is calculated, and the erecting time corresponding to the motor power closest to the rated speed speed is taken as the erecting end time powertime of the constant power stage; When the motor speed reaches the rated speed, the constant speed control electric cylinder is used for erecting, the initial erecting angle and the erecting angle speed are determined as the erecting angle and the erecting angle speed corresponding to the state at the end of the constant power stage, the erecting angle angleS of the constant speed stage is calculated, and the erecting time corresponding to the erecting angle closest to the rated deceleration angle slowangle is taken as the erecting end time speedtime of the constant speed stage; Then the uniform deceleration control electric cylinder is used for deceleration until the electric cylinder stops; The total erecting time totaltime is: totaltime = slowtime + speedtime Where angle is the erecting angle, angleS3 is the current erecting angle obtained by the constant speed stage, angleV3 is the current erecting speed obtained by the constant speed stage, slowtime is the deceleration stage time, and angleA is the erecting angle acceleration; The GA method is used to optimize the total erecting time, The total erecting time totaltime is used as the fitness parameter, the optimization parameters are determined and imported into the GA toolbox, and the toolbox uses the code: [x, totaltime] = ga(@timecalculate, nvars, [], [], [], [], lb, ub) Where: x-----the optimization parameter matrix composed of the optimal solution of each optimization parameter; timecalculate-----the function for calculating the total erecting time; totaltime-----the optimized total erecting time; nvars-----the number of optimization parameters; [], [], [], []-----nonlinear constraints and linear constraints; lb-----the lower limit value of the optimization parameter; ub-----the upper limit value of the optimization parameter; The optimization parameters include one or more combinations of the upper and lower hinge point positions of the electric cylinder, the reduction ratio of the reducer, the reduction ratio of the gear box and the total lead of the screw.

2. The GA-RK based fast vertical lift method of electric cylinders as claimed in claim 1, wherein, The smooth curve is used for fitting between each stage, and the vertical angle angleS, vertical velocity angleV and vertical acceleration angleA of each stage are spliced after fitting to obtain the planning result and total vertical time in the total vertical process.

3. The GA-RK based fast vertical lift method of electric cylinders as claimed in claim 1, wherein, The calculation process of motor power corresponding to the constant torque stage is as follows: The total torque T that the system can provide in the constant torque stage and the vertical acceleration angleA under the constant torque condition are calculated as follows: Where torque is the rated torque of the motor, djs is the number of motors providing mechanical energy in a single electric cylinder, dgs is the number of electric cylinders contained in the vertical system, n1 is the friction efficiency, n2 is the multi-cylinder synchronization efficiency, n3 is the motor efficiency, n4 is the driver efficiency, n5 is the reducer efficiency, n6 is the gear box efficiency, n7 is the screw pair efficiency, slowratio is the reduction ratio of the reducer, and forcearm is the distance from the rotation point to the line where the output direction of the electric cylinder is located.

4. The GA-RK based fast vertical lift method of electric cylinders as claimed in claim 1, wherein, The calculation process of motor speed corresponding to the constant power stage is as follows: The total power P that the system can provide in the constant power stage and the vertical acceleration angleA under the constant power condition are calculated as follows: P = power × djs × dgs × 1000 × n1 × n2 × n4 × n5 × n6 × n7 × n8 The relationship matrix of the vertical angle angleS, vertical velocity angleV, vertical acceleration angleA and vertical time angletime in the constant power stage is obtained by using the ode45 function to control the value corresponding to the vertical acceleration; The corresponding motor speed nst is determined according to the above relationship, wherein power is the rated power of the motor, djs is the number of motors providing mechanical energy in a single electric cylinder, dgs is the number of electric cylinders contained in the vertical system, n1 is the friction efficiency, n2 is the multi-cylinder synchronization efficiency, n3 is the motor efficiency, n4 is the driver efficiency, n5 is the reducer efficiency, n6 is the gear box efficiency, n7 is the screw pair efficiency, n8 is the other efficiency of power loss, Jload is the rotational inertia of the load, Mgravity is the torque of the load gravity around the rotation point, odown is the distance from the lower hinge point of the electric cylinder to the rotation point, oup0 is the distance from the upper hinge point of the electric cylinder to the rotation point in the initial state, beta1 is the included angle between the upper and lower hinge points of the electric cylinder and the rotation point, beta2 is the included angle between the line connecting the center of mass and the rotation point and the x-axis, downup is the length of the electric cylinder after vertical lifting by a certain angle, pitch is the total lead of the screw, slowratio is the reduction ratio of the reducer, and gearratio is the reduction ratio of the gear box.

5. The GA-RK based fast vertical lift method of electric cylinders as claimed in claim 1, wherein, The calculation process of the vertical angle angleS in the constant speed stage is as follows: The relationship of the vertical acceleration angleA and the vertical angle angleS, and the vertical velocity angleV under the constant speed condition is calculated as follows: The vertical angle angleS in the constant speed stage is obtained by using the ode45 function to control the value corresponding to the vertical acceleration; wherein odown is the distance from the lower hinge point of the electric cylinder to the rotation point, oup0 is the distance from the upper hinge point of the electric cylinder to the rotation point in the initial state, and beta1 is the included angle between the upper and lower hinge points of the electric cylinder and the rotation point.

Images