Method of operation of electric excavator drives at low temperatures

Abstract

FIELD: mining mechatronics.SUBSTANCE: invention is intended to improve the operational reliability of quarry excavators at low ambient temperatures by adjusting the mechanical characteristics of drives to reduce dynamic loads. A method is proposed for temperature correction of the values of angular velocity and mechanical torque of electric drives of an electric excavator when operating at low temperatures, in which the ambient temperature θ c is measured, regulate the angular velocity of electric drives with torque limitation, in the memory of the control controller for each electric drive, the data of the parameters of the angular velocity of the electric drive and the mechanical torque are stored and the parameters of the angular velocity of the electric drive and the mechanical torque are corrected automatically. Moreover, the first linear section of the dependence of the angular velocity on the mechanical torque (mechanical characteristic) of the electric drive corresponds to the range of high angular velocities. The second section corresponds to the range of average angular velocities and has a hyperbolic dependence of angular velocity on torque. The third linear section corresponds to the range of maximum loads and low angular velocities. The beginning of this section corresponds to the cut-off point, which is adjusted depending on the temperature. The regulation of the rigidity of the mechanical characteristic in the first section and the cut-off moment occurs depending on the ambient temperature in accordance with the logistic dependence of the impact toughness of the metal on temperature. The values used as correction temperature are θ=θp(t+τ2) when θc > θp (t+τ2) and θ=θc(t-τ1) when θc ≤ θp (t +τ2), where τ2 is the forecast time interval. When the predicted ambient temperature decreases, the mechanical characteristics of the electric drives are adjusted: the rigidity in the range of high angular velocities is reduced and the cutoff moment МCUT is reduced in advance for the time τ2 until the ambient temperature reaches the predicted value. When the ambient temperature increases, the modified mechanical characteristics of the drives are maintained for a period of time τ1, i.e. the transient process with an increase in ambient temperature.EFFECT: increasing the reliability of the operation of the mechanical equipment of the excavator at low temperatures by correcting the mechanical characteristics of the electric drives.1 cl, 3 dwg

Description

[0001] The proposed invention relates to mining mechatronics and is intended to improve the reliability of electric quarry excavators at low ambient temperatures by adjusting the mechanical characteristics of drives in order to reduce dynamic loads.

[0002] Known methods are for temperature correction of the values ​​of angular velocity and mechanical torque of electric drives of an electric excavator when operating at low temperatures, in which the ambient temperature is measured, the angular velocity of the drives with torque limitation is regulated, and the speed reference and torque limitation are adjusted as a function of the ambient temperature (USSR A.S. No. 1090813. IPC E02F 9 / 20. Single-bucket excavator electric drive control device / D.E. Makhno et al. - Published 07.05.1984, Bulletin No. 17; USSR A.S. No. 1416626. IPC E02F 9 / 20. Excavator electric drive control device / R.E. Klimenko et al. - Published 15.08.1988, Bulletin No. 30; Russian Federation Patent No. 2255184. IPC E02F 9 / 20; H02P 5 / 00. Method for controlling a direct current electric drive of a single-bucket excavator and a device for implementing it / S.S. Leonenko et al. - Published 06 / 27 / 2005, Bulletin No. 18).

[0003] In known methods, the mechanical characteristics of DC electric drives have two sections of linear dependence of angular velocity on the load torque. The motor's stall torque is controlled by a complex parameter that takes into account the machine metal temperature, wind load, and the rate of change of these quantities. Electric excavator drives operate in a cyclical start-stop mode. Dynamic effects on the mechanical components of the excavator at low ambient temperatures pose a risk of brittle fractures. Moreover, the greatest danger to the metal structures of excavators comes from transient thermal deformations due to temperature fluctuations, both during decreases and increases in temperature. In known methods, speed adjustment and stall torque limitation are performed without taking into account predicted ambient temperatures.Due to the inertia of thermal processes in metal structures, the change in parameters does not correspond to the time intervals during which transient processes occur and which pose the greatest danger in terms of destruction.

[0004] Thus, the disadvantage of known methods of operating electric excavator drives at low temperatures is the low reliability of the electromechanical equipment.

[0005] Of the known methods, the closest to the proposed technical solution is the method of temperature correction of the values ​​of angular velocity and mechanical torque of electric drives of an electric excavator when operating at low temperatures, in which the ambient temperature θ is measured c, regulate the angular velocity of electric drives with torque limitation, in the memory of the control controller for each electric drive, the data on the parameters of the angular velocity of the electric drive and the mechanical torque are stored and the parameters of the angular velocity of the electric drive and the mechanical torque are adjusted automatically depending on the temperature in accordance with the expression

[0006]

[0007] where Ω is the angular velocity of the drive; Ω0 is the idle angular velocity; M is the mechanical torque; M ст - locking moment; P н - rated engine power; α and β are coefficients depending on the ambient temperature and the category of the material being developed,

[0008]

[0009] where α0 is the proportionality coefficient; χ is the correction coefficient depending on the category of the material being developed; and α and a β- tuning coefficients; b - coefficient depending on the temperature properties of metal structures; θ - correction temperature; θ0 - temperature corresponding to the upper limit of the interval of critical change in brittleness (RU Patent No. 2850773, IPC E02F 9 / 20; H02P 6 / 08. Method of operation of excavator electric drives at low temperatures / S.I. Malafeev, S.S. Malafeev, N.A. Serebrennikov. - Published 11 / 13 / 2025, Bulletin No. 32).

[0010] In the known method, the dependence of angular velocity on mechanical torque, i.e., the mechanical characteristic of the electric drive, has three sections. The first linear section corresponds to the range of high angular velocities and has adjustable stiffness. The second section corresponds to the range of medium angular velocities and has a hyperbolic dependence of angular velocity on torque. In this section, the drive operates in constant power mode. The third linear section corresponds to the range of maximum loads and low angular velocities. The beginning of this section corresponds to the cutoff torque, which is adjusted depending on temperature. The end of the third section corresponds to the stall torque point and zero angular velocity of the drive. Adjustment of the stiffness of the mechanical characteristic in the first section and the cutoff torque occurs depending on the ambient temperature, in accordance with the logistic dependence of the metal's impact toughness on temperature.Operating the drive with constant power in the medium angular velocity range and reduced rigidity at high speeds and loads reduces dynamic loads while maintaining the stall force (i.e., maximum digging torque) and idle angular velocity. Modifying the mechanical characteristics does not significantly reduce excavator performance. Thus, the mechanical performance of the excavator is improved at low temperatures by modifying the mechanical characteristics.

[0011] The greatest danger to excavator metal structures is presented by transient thermal deformations during temperature fluctuations, both during decreases and increases. Known methods modify the mechanical characteristics of drives without taking into account predicted ambient temperatures. Due to the inertia of thermal processes in metal structures, changes in drive settings do not correspond to the time intervals during which transient temperature changes occur, which pose the greatest risk of damage.

[0012] Thus, the disadvantage of the known method is the method of temperature correction of the values ​​of the angular velocity and mechanical torque of the electric drives of an electric excavator when operating at low temperatures.

[0013] The purpose of the proposed invention is to increase the reliability of the operation of the electromechanical equipment of an excavator at low temperatures.

[0014] The stated goal is achieved by the fact that in the known method of temperature correction of the values ​​of angular velocity and mechanical moment of electric drives of an electric excavator when operating at low temperatures, in which the ambient temperature θ is measured c , regulate the angular velocity of electric drives with torque limitation, in the memory of the control controller for each electric drive, the data of the parameters of the angular velocity of the electric drive and the mechanical torque are stored, and the parameters of the angular velocity of the electric drive and the mechanical torque are adjusted automatically depending on the temperature in accordance with the expression

[0015]

[0016] where Ω is the angular velocity of the drive; Ω0 is the idle angular velocity; M is the mechanical torque; M ст- locking moment; P н - rated engine power; α and β are coefficients depending on the ambient temperature and the category of the material being developed,

[0017]

[0018] where α0 is the proportionality coefficient; χ is the correction coefficient depending on the category of the material being developed; and α and a β - adjustment coefficients; b - coefficient depending on the temperature properties of metal structures; θ - correction temperature; θ0 - temperature corresponding to the upper limit of the interval of critical change in brittleness, in addition, the on-board computer of the excavator stores in memory the values ​​of the ambient temperature θ c (t - τ1) in the time interval (t - τ1), where t is the current time, τ1 is the time shift, periodically receives data on the predicted values ​​of temperature θ upon request пfrom the weather service server, and the values ​​θ = θ are used as the correction temperature п (t + τ2) at θ с > θ п (t + τ2) and θ = θ с (t - τ1) at θ с ≤ θ п (t + τ2), where τ2 is the forecast time interval, transmit data on the current and forecast temperatures of the environment, as well as the found correction temperature to the electric drive control controller, store in the memory of the control controller for each electric drive the values ​​of the correction temperature for regulating the values ​​of the angular velocity of the electric drives with torque limitation, additionally automatically correct the angular velocity of the electric drive and the mechanical torque in the electric drive control controller depending on the found value of the correction temperature.

[0019] Compared with the closest similar technical solution, the proposed method contains the following new operations:

[0020] - the excavator's on-board computer stores the ambient temperature θ values ​​in its memory c (t - τ1) in the time interval (t - τ1), where t is the current time, τ1 is the time shift;

[0021] - periodically receives data on predicted temperature values ​​θ upon request п from the weather service server;

[0022] - the values ​​θ = θ are used as the correction temperature п (t + τ2) at θ с > θ п (t + τ2) and θ = θ c (t - τ1) at θс ≤ θ п (t + τ2), where τ2 is the forecast time interval;

[0023] - transmit data on the current and predicted ambient temperatures, as well as the detected correction temperature to the electric drive controller;

[0024] - store in the memory of the control controller for each electric drive the correction temperature values ​​for regulating the angular velocity values ​​of electric drives with torque limitation;

[0025] - additionally automatically corrects the angular velocity of the electric drive and the mechanical torque in the electric drive controller depending on the detected correction temperature value.

[0026] Therefore, the claimed technical solution meets the requirement of “novelty”.

[0027] For each of the distinguishing features, a search was conducted for known technical solutions in the field of electrical engineering, electric drives and mining automation.

[0028] Operations:

[0029] - the excavator's on-board computer stores the ambient temperature θ values ​​in its memory c (t - τ1) in the time interval (t - τ1), where t is the current time, τ1 is the time shift;

[0030] - periodically receives data on predicted temperature values ​​θ upon request п from the weather service server;

[0031] - the values ​​θ = θ are used as the correction temperature п (t + τ2) at θ с > θ п (t + τ2) and θ = θ c(t - τ1) at θ с ≤ θ п (t + τ2), where τ2 is the forecast time interval;

[0032] - transmit data on the current and predicted ambient temperatures, as well as the detected correction temperature to the electric drive controller;

[0033] - store in the memory of the control controller for each electric drive the correction temperature values ​​for regulating the angular velocity values ​​of electric drives with torque limitation;

[0034] - additionally automatically corrects the angular velocity of the electric drive and the mechanical torque in the electric drive controller depending on the detected correction temperature value,

[0035] Not found in known technical solutions.

[0036] Thus, the specified features ensure that the claimed technical solution meets the requirement of “significant differences”.

[0037] The proposed technical solution improves the reliability of excavator electromechanical equipment at low temperatures. This is achieved by correcting the angular velocity and mechanical moments at low and transient ambient temperatures. The values ​​θ = θ are used as the correction temperature. п (t + τ2) at θ с > θ п (t + τ2) and θ = θ с (t _ τ1) at θ с ≤ θ п (t + τ2), where τ2 is the forecast time interval. As the forecast ambient temperature decreases, the dependences of angular velocities on mechanical moments (mechanical characteristics) of electric drives are modified: the rigidity in the range of high angular velocities decreases and the cutoff torque M decreases. отсin advance, for a time τ2 before the ambient temperature reaches the predicted value. This reduces the acceleration and dynamic loads of the drives during the transient temperature drop. At the same time, the value of the holding torque M is maintained. ст and drive power within the range of primary operating loads. As the ambient temperature increases, the adjusted angular velocity and mechanical torque parameters of the electric drives are maintained for a time interval of τ1, i.e., during the transient change in the temperature of the metal structures with increasing ambient temperature. The adjusted mechanical characteristics of the drives exert a damping effect on the system and reduce dynamic loads. Modifying the mechanical characteristics does not significantly reduce the excavator's performance.

[0038] Therefore, the claimed technical solution meets the requirement of “positive effect”.

[0039] The essence of the proposed invention is explained by the drawings. Fig. 1 shows a simplified diagram of the control system for AC drives of an electric quarry excavator, implementing the proposed method. Fig.1 indicates: 1 - three-phase power supply network 6 kV, 50 Hz; 2 - input electrical switchgear of the excavator; 3 - main step-down transformer; 4 - ambient temperature sensor; 5 and 6 - command devices for controlling the electric drives of the excavator; 7 - power reactor; 8 - transformer for power supply of auxiliary needs of the excavator; 9 - CAN bus; 10 - drive control controller; 11 - active rectifier; 12 - auxiliary electrical equipment for controlling the excavator; 13 and 15 - inverter control units; 14 - DC link capacitive storage; 16 - driver's monitor; 17 and 18 - electric drive inverters; 19 - transistor converter of emergency energy dump; 20 and 21 - electric motors of the excavator drives; 22 - Internet network; 23 - on-board computer; 24 - weather service server; 25 - resistor block. In Fig.1 shows the control circuits for only two engines 20 and 21; the remaining engines of the main drive and travel drives, of which there are seven in modern excavators, for example, the EKG-20 (two machines each in the lifting, turning and travel drives and one pressure engine), as well as other electrical equipment of the excavator are not shown in order to simplify the drawing.

[0040] The electric excavator drive control system implementing the proposed method operates as follows. The excavator is connected to the power grid 1. The grid voltage is fed to the input high-voltage switchgear 2. The main step-down transformer 3 supplies the local DC electric grid. The output AC voltage of transformer 3 is converted via reactor 7 by active rectifier 11 into a stabilized DC link voltage with capacitive storage 14. This voltage supplies power to all excavator drives. Inverters 17 and 18 regulate the speed of the main drive and travel drive motors 20 and 21. The inverter control signals are generated by control units 15 and 13, respectively. Transistor converter 19 serves for emergency energy dumping and its conversion into heat using resistor block 25.

[0041] The second step-down transformer 8 is designed to supply power to the auxiliary electrical equipment of the excavator 12 (ventilation, heating, lighting, oil pumps, etc.). The CAN network 9 is designed for data exchange between system components. On-board computer 23 performs:

[0042] - collection and processing of data on the state of all components to generate control commands and transmit data to the excavator’s information and diagnostic system;

[0043] - generating weather forecast requests for the 24-hour weather server, receiving data on forecast temperature values ​​θ upon request п from the weather service server 24;

[0044] - storing ambient temperature values ​​θ in memory c (t - τ1) in the time interval (t - τ1), where t is the current time, τ1 is the time shift,

[0045] - transmission of correction signals to the drive control controller 10;

[0046] - transfer of data on current and predicted temperatures and actual reduction in the rigidity of mechanical characteristics of drives for display on monitor 16.

[0047] Monitor 16 is located in the driver's cab and is designed to display the processes and status of electrical equipment. Temperature sensor 4 generates a signal proportional to the ambient temperature, which is sent to the inputs of drive controller 10 and via CAN bus 9 to on-board computer 23. Drive controller 10, which generates signals for all drives, stores the adjustment temperature correction values ​​for each electric drive in memory to regulate the angular velocity of the torque-limiting electric drives.

[0048] The values ​​of angular velocities and mechanical moments that determine the shapes and parameters of mechanical characteristics are set programmatically using the operator's monitor 16 or are modified automatically during excavator operation depending on the ambient temperature.

[0049] When the excavator is operating, the operator controls the travel drives using command devices 5 and 6. The output signals from command devices 5 and 6 and ambient temperature sensor 4 are sent to the inputs of controller 10, which is also connected to the local CAN network 9. The controller's output signal, in the form of a serial digital code with the receiver identification numbers, is transmitted to the inputs of control units 13 and 15. The speed setting signals for the main travel and drive drives are generated depending on the position of command devices 5 and 6, with correction based on the current, stored, and predicted ambient temperatures.

[0050] Figure 2 shows the mechanical characteristics of the excavator electric drive. The solid line represents the main special characteristic with limitations on power, angular velocity, and torque in various drive operating modes at normal temperatures. In the range of high angular velocities and low torques (section 1), angular velocity stabilization with a high stiffness value is ensured. In the medium load range (section 2), the hyperbolic characteristic in the drive limits the specified power. The third section (3) of the characteristic corresponds to the torque limitation, i.e., the stopper.

[0051] At low temperatures, the mechanical characteristic is automatically modified according to equation (1). The modified characteristic is shown in Fig. 2 by the dotted line. The characteristic stiffness α -1In the first section, it decreases depending on temperature in accordance with equation (2). The dependence of the coefficient α (a value inversely proportional to the stiffness) on temperature is described by a logistic function that models the decrease in impact toughness at low temperatures. In equation (2), the coefficient α0 has a dimension inverse to the dimension of the stiffness of the mechanical characteristic rad⋅(s⋅N⋅m) -1 The dimensionless correction factor χ takes into account the category of the material being developed. For example, for rocks of category I-III, the factor χ=1, for rocks of category IV-V, the factor χ=1.1. The dimensionless factor a α is chosen equal to the relative value of the reduction in angular velocity at the nominal load torque and minimum temperature. The coefficient b has the dimension K -1 and characterizes the rate of change of impact toughness with changes in temperature.

[0052] Fig. 3 (solid line) shows a graph of the dependence of the relative value of the coefficient from temperature, constructed for values ​​χ = 1; and α = 0.4; b = 0.25 K -1 .

[0053] The second section of the mechanical characteristic corresponds to the drive's operation under a specified limitation, such as rated power. The angular velocity is inversely proportional to the torque, i.e. . Torque value corresponds to the transition point of the mechanical characteristic from the first section to the second.

[0054] The third linear section of the mechanical characteristic provides a "soft" reduction in angular velocity in the maximum load zone. The value of the torque M отс = βM стcorresponds to the transition point of the mechanical characteristic from the second to the third section, i.e., the cutoff point. The dependence of the dimensionless coefficient β on temperature is described by a logistic function that models the change in impact toughness at low temperatures. The dimensionless correction factor χ takes into account the category of the material being developed. The dimensionless coefficient a β is selected equal to the relative reduction in the cut-off torque in relation to the stopping torque at minimum temperature.

[0055] Fig. 3 (dashed line) shows a graph of the dependence of the coefficient β on temperature, constructed for values ​​χ = 1; a β = 0.3; b = 0.25 K -1 .

[0056] The correction temperature is θ = θ п (t + τ2) at θ c > θ п (t + τ2) and θ = θ с (t - τ1) at θ с ≤ θ п(t + τ2), where τ2 is the forecast time interval. As the forecast ambient temperature decreases, the mechanical characteristics of the electric drives are modified: the stiffness in the high-speed range decreases, and the cutoff torque M decreases. ОТС in advance, for a time τ2 before the ambient temperature reaches the predicted value. This reduces the acceleration and dynamic loads of the drives during the transient process of decreasing the temperature of the metal structures. At the same time, the value of the holding torque M is maintained. СТand drive power within the range of primary operating loads (section 2). Consequently, the excavator's primary operating characteristics are not significantly reduced. As the ambient temperature increases, the modified mechanical characteristics of the drives are maintained for the time interval τ1, i.e., the transient process with increasing ambient temperature. The modification of the mechanical characteristics at low and transient temperatures, shown in Fig. 2, ensures their "softening." The "soft" mechanical characteristics of the electric drives exert a damping effect on the system and reduce dynamic loads. Reducing dynamic loads improves the operational reliability of the electromechanical equipment at low and transient ambient temperatures.

[0057] On-board computer 23 generates a message about the temperatures and drive settings for display on monitor 16, for example, in the form:

[0058] Air temperature θ с , °С;

[0059] Air temperature according to forecast θ п , °С;

[0060] Drive characteristic hardness reduction level - no (10%, 20% …).

[0061] Therefore, the use of a known method for temperature correction of the values ​​of angular velocity and mechanical torque of electric drives of an electric excavator when operating at low temperatures, in which the ambient temperature θ is measured С , regulate the angular velocity of electric drives with torque limitation, in the memory of the control controller of each electric drive, the data of the parameters of the angular velocity of the electric drive and the mechanical torque are stored and the parameters of the angular velocity of the electric drive and the mechanical torque are adjusted automatically depending on the temperature in accordance with the expression

[0062]

[0063] where Ω is the angular velocity of the drive; Ω0 is the idle angular velocity; M is the mechanical torque; M ст - locking moment; Pн - rated engine power; α and β are coefficients depending on the ambient temperature and the category of the material being developed,

[0064]

[0065] where α0 is the proportionality coefficient; χ is the correction coefficient depending on the category of the material being developed; and α and a β - adjustment coefficients; b - coefficient depending on the temperature properties of metal structures; θ - correction temperature; θ0 - temperature corresponding to the upper limit of the interval of critical change in brittleness, additionally storing the value of the ambient temperature θ in the memory of the on-board computer of the excavator c (t - τ1) in the time interval (t - τ1), where t is the current time, τ1 is the time shift, according to requests for periodic receipt of data on the predicted values ​​of temperature θ п from the weather service server, and the values ​​θ = θ are used as the correction temperature п(t + τ2) at θ с > θ п (t + τ2) and θ = θ с (t - τ1) at θ с ≤ θ п (t + τ2) where τ2 is the time interval of the forecast, the transmission of data on the current and forecasted ambient temperatures, as well as the found correction temperature to the electric drive controller, the storage in the memory of the control controller of each electric drive of the correction temperature value for regulating the values ​​of the angular velocity of electric drives with torque limitation, additional automatic correction of the angular velocity and mechanical torque of electric drives in the electric drive controller depending on the found correction temperature value, increases the reliability of the electromechanical equipment.

[0066] The use of the proposed method in mechatronic systems of electric drives of quarry excavators will contribute to increasing the reliability and quality of operation of mechanical equipment.

Claims

A method for temperature correction of the values ​​of angular velocity and mechanical torque of electric drives of an electric excavator when operating at low temperatures, in which the ambient temperature θ is measured c , regulate the angular velocity of electric drives with torque limitation, in the memory of the control controller for each electric drive, the data on the parameters of the angular velocity of the electric drive and the mechanical torque are stored and the parameters of the angular velocity of the electric drive and the mechanical torque are adjusted automatically depending on the temperature in accordance with the expression where Ω is the angular velocity of the drive; Ω0 is the idle angular velocity; M is the mechanical torque; M ст - locking moment; P Н - rated engine power; α and β are coefficients depending on the ambient temperature and the category of the material being developed, where α0 is the proportionality coefficient; χ is the correction coefficient depending on the category of the material being developed; and α and a β - adjustment factors; b - factor depending on the temperature properties of metal structures; θ - correction temperature; θ0 - temperature corresponding to the upper limit of the interval of critical change in brittleness, characterized in that the on-board computer of the excavator additionally stores in memory the values ​​of the ambient temperature θ c (t - τ1) in the time interval (t - τ1), where t is the current time, τ1 is the time shift, periodically receives data on the predicted values ​​of temperature θ upon request п from the weather service server, and the values ​​θ = θ are used as the correction temperature п (t - τ2) at θ с > θ п (t - τ2) and θ = θ c (t - τ1) at θ c ≤ θ п(t + τ2), where τ2 is the forecast time interval, transmit data on the current and forecast temperatures of the environment, as well as the determined correction temperature to the electric drive control controller, store in the memory of the control controller of each electric drive the values ​​of the correction temperature for regulating the values ​​of the angular velocity of the electric drives with torque limitation, additionally automatically correct the angular velocity of the electric drive and the mechanical torque in the electric drive control controller depending on the determined value of the correction temperature.

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