Continuous casting machine blank moving vehicle high-precision position control method based on motor rotating speed feedback

Abstract

The invention belongs to the technical field of metallurgical continuous casting equipment control, and particularly relates to a continuous casting machine blank moving vehicle high-precision position control method based on motor rotating speed feedback. Comprising the following steps: S1, acquiring a rotating speed signal and a current signal of a motor for driving the blank moving vehicle in real time; s2, establishing a conversion model between the rotating speed of the motor and linear displacement of the blank moving vehicle according to mechanical transmission system parameters of the blank moving vehicle; s3, calculating the real-time accumulated displacement of the blank moving vehicle based on the rotating speed signal and the conversion model; s4, a dynamic compensation mechanism is introduced in the real-time accumulated displacement calculation process to compensate for displacement errors caused by mechanical transmission gaps and / or load fluctuation; and S5, performing closed-loop control on the motor according to the deviation between the compensated real-time accumulated displacement and the target position. The device can improve the position control precision of the blank moving vehicle, is not influenced by field high temperature, dust and vibration, and is good in reliability.

Description

Technical Field

[0001] This invention belongs to the field of control technology for metallurgical continuous casting equipment, and particularly relates to a high-precision position control method for the billet transfer car of a continuous casting machine based on motor speed feedback. Background Technology

[0002] The billet transfer car in a continuous casting machine is a key piece of equipment on the continuous casting production line, transferring high-temperature billets from the crystallizer outlet to subsequent processes. Its positioning accuracy directly affects production efficiency and safety. Currently, the positioning control of the billet transfer car mainly relies on external position sensors (such as laser rangefinders). In the harsh environment of metallurgical workshops—high temperature, dust, and strong vibration—existing technologies have significant drawbacks: external sensors are expensive and prone to errors or failures due to high-temperature radiation and dust adhesion, requiring frequent maintenance, resulting in low positioning accuracy and poor long-term reliability. Therefore, there is an urgent need for a method that does not rely on expensive external sensors and can achieve high-precision, high-reliability position control under harsh operating conditions. Summary of the Invention

[0003] The purpose of this invention is to provide a high-precision position control method for the billet transfer car of a continuous casting machine based on motor speed feedback, so as to solve the problems existing in the prior art.

[0004] The technical solution adopted by this invention to solve its technical problem is:

[0005] A high-precision position control method for the billet transfer car of a continuous casting machine based on motor speed feedback includes the following steps:

[0006] S1. Real-time acquisition of the speed and current signals of the motor driving the billet transfer cart;

[0007] S2. Based on the mechanical transmission system parameters of the billet transfer car, establish a conversion model between the motor speed and the linear displacement of the billet transfer car;

[0008] S3. Based on the rotation speed signal and conversion model, calculate the real-time cumulative displacement of the billet transfer car;

[0009] S4. A dynamic compensation mechanism is introduced in the real-time cumulative displacement calculation process to compensate for displacement errors caused by mechanical transmission clearance and / or load fluctuations.

[0010] S5. Based on the deviation between the compensated real-time cumulative displacement and the target position, perform closed-loop control on the motor.

[0011] Furthermore, the conversion model described in step S2 is used to calculate the linear displacement ΔL of the moving trolley corresponding to each revolution of the motor, and its expression is:

[0012] ;

[0013] Where D is the diameter of the drive wheel, N gearZ represents the number of teeth on the driving gear. chain denoted as the number of links in the transmission chain, and i represents the gear ratio of the reducer.

[0014] Furthermore, the method for calculating the real-time cumulative displacement of the billet transfer car in step S3 is as follows:

[0015] ;

[0016] Where S(t) is the cumulative displacement of the billet transfer car from time 0 to time t, in meters; n(τ) is the rotational speed of the motor at time τ after being collected and converted through step S1, in revolutions per second.

[0017] Furthermore, the compensation for the mechanical transmission clearance in step S4 includes: when a change in the movement direction of the transfer cart is detected, a compensation amount based on the dynamic clearance value is superimposed on the calculated displacement.

[0018] Furthermore, the dynamic gap value is an adaptive value that is dynamically adjusted based on ambient temperature, mechanical wear, and the cumulative operating time of the system.

[0019] Furthermore, the compensation for load fluctuations in step S4 includes: estimating the load torque based on the real-time collected motor current signal, and dynamically adjusting a displacement integral weighting coefficient based on the load torque, with the weighting coefficient ranging from (0.95 to 1.00).

[0020] Furthermore, in step S3, before calculating the real-time cumulative displacement, the rotational speed signal is processed using a Kalman filter algorithm to eliminate noise interference.

[0021] Furthermore, in step S5, a PID control algorithm is used for closed-loop control.

[0022] The present invention has the following beneficial effects:

[0023] 1. This invention effectively corrects the main error sources through a dynamic compensation mechanism, achieving sub-centimeter-level positioning accuracy without using external position sensors. Furthermore, the system is unaffected by harsh environments, significantly improving reliability.

[0024] 2. It completely eliminates the need for expensive external sensors such as laser rangefinders and their maintenance costs, achieving a balance between high performance and low cost.

[0025] 3. The core algorithm of this invention relies solely on the encoder and current signal built into the motor, which has natural immunity to high temperatures, dust, and vibrations on site, ensuring continuous and stable production operation.

[0026] 4. The gap compensation model can be adaptively adjusted according to temperature and time, and the load compensation can suppress slippage in real time, thereby improving the stability of control and reducing the intensity of manual maintenance. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0028] This embodiment provides a high-precision position control method for the billet transfer car of a continuous casting machine based on motor speed feedback. The specific steps are as follows:

[0029] S1. Construct and install the relevant control system, including:

[0030] Signal acquisition module: incremental encoder (1024 lines) at the motor shaft end, and current detection unit of the frequency converter itself.

[0031] Control unit: A high-performance PLC (such as Siemens S71500) is selected, which is internally programmed to implement the displacement calculation, dynamic compensation and PID control algorithm.

[0032] Human-machine interaction module: Industrial touch screen, which communicates with the PLC via Ethernet.

[0033] All devices are connected via PROFINET industrial Ethernet, forming a distributed control system.

[0034] System initialization and parameter input: Input the mechanical transmission parameters of the transfer cart through the human-machine interface (HMI), including the drive wheel diameter D=0.5m and the number of teeth N of the drive gear. gear =20, number of chain links Z chain =100, reducer transmission ratio i=20. Simultaneously, the initial mechanical clearance value δ0=1mm, clearance temperature compensation coefficient α=0.02mm / ℃, reference temperature T0=20℃, and clearance wear compensation coefficient β=0.001mm / h are preset. Load compensation threshold current I. th =50A (corresponding torque threshold) load compensation saturation current I sat =70A, slip compensation factor λ=0.05, sampling period Ts=0.01s.

[0035] The motor's original speed signal, measured in RPM, is acquired in real-time at a period Ts using an incremental encoder built into the motor. This signal is then divided by 60 to convert it to revolutions per second (rpm). Simultaneously, the motor's three-phase currents Ia(k), Ib(k), and Ic(k) are read via a frequency converter. The instantaneous torque current Iq(k) is calculated to characterize the load torque. Finally, the ambient temperature sensor value T(k) is read from a temperature sensor.

[0036] S2. Based on the mechanical transmission system parameters of the billet transfer car, establish a conversion model between the motor speed and the linear displacement of the billet transfer car, the expression of which is:

[0037] ;

[0038] Where D is the diameter of the drive wheel, N gear Z represents the number of teeth on the driving gear. chain denoted as the number of links in the transmission chain, and i represents the gear ratio of the reducer.

[0039] S3. First, the Kalman filter algorithm is used to process the rotation speed signal to eliminate noise interference, obtaining a smoothed and denoised rotation speed value. Then, based on the rotation speed signal and the conversion model, the real-time cumulative displacement of the transfer car is calculated. The calculation method for the real-time cumulative displacement of the transfer car is as follows:

[0040] ;

[0041] Where S(t) is the cumulative displacement of the billet transfer car from time 0 to time t, in meters; n(τ) is the rotational speed of the motor at time τ after being collected and converted through step S1, in revolutions per second.

[0042] In practical digital control systems, the aforementioned continuous integral is implemented using a discretization algorithm. For example, in a system with a sampling period of Ts, the cumulative displacement S(k) at the k-th sampling time can be recursively calculated as follows:

[0043] S(k) = S(k-1) + ΔL·n(k)·Ts, where n(k) is the rotational speed (r / s) at the kth sampling time, and S(k) is the discrete-time representation of S(t), where t = k*Ts.

[0044] S4. Dynamic compensation mechanism, including mechanical clearance compensation and load fluctuation compensation:

[0045] Mechanical backlash compensation: When the direction of motion changes, the backlash value is superimposed on the displacement calculation result. The motor's rotational speed is a signed quantity. Typically, the speed is defined as positive when rotating forward (e.g., moving towards target position A) and negative when rotating in reverse (returning or moving towards target position B). Therefore, the sign of the rotational speed can be used to determine whether a change in the direction of motion has occurred. For example, by comparing the rotational speed signs of the current detection cycle k with those of the previous detection cycle k-1, if the signs are different, it is determined that a change in direction has occurred.

[0046] To further improve accuracy, an adaptive model of gap-temperature-run time is established:

[0047] δ(k) = δ0 + α·(T(k) - T0) + β·t op(k); where δ(k) is the dynamic clearance value; δ0: preset initial mechanical clearance value (mm), obtained through no-load testing; α: clearance temperature compensation coefficient (mm / ℃), determined by the thermal expansion characteristics of the transmission material, with a value of 0.02mm / ℃; T(k): current ambient temperature (℃); T0: reference temperature (℃), usually taken as room temperature 20℃; β: clearance wear compensation coefficient (mm / h), obtained by fitting historical wear data, with a value of 0.001mm / h; t op (k): System cumulative uptime (hours), starting from the last major overhaul.

[0048] After calculating the dynamic clearance value δ(k), the displacement increment ΔSgap(k) that needs to be compensated for due to mechanical clearance in the k-th sampling period is calculated using the following formula: ΔSgap(k) = sign(n(k)) × δ(k) / 1000; where ΔSgap(k) is the displacement increment that needs to be compensated for due to mechanical clearance in the k-th sampling period; sign(n(k)) is the sign function, taking the sign of the current motor speed n(k). If n(k) > 0 (forward rotation), then sign(n(k)) = +1; if n(k) < 0 (reverse rotation), then sign(n(k)) = -1; if n(k) = 0 (stopped), then sign(n(k)) = 0. δ(k) is the dynamic mechanical clearance value at the current sampling moment, which is converted from millimeters to meters after being divided by 1000.

[0049] Load fluctuation compensation: Estimating the load torque T based on the motor current signal. load (k): T load (k)≈Kt*|Iq(k)|, where Kt is the motor torque constant. Then, based on the load torque T... load A weighting coefficient η(k) is dynamically calculated based on the magnitude of (k):

[0050] ;

[0051] The value of η(k) is between 0.95 and 1.00. The larger the load, the smaller the coefficient, in order to suppress slippage.

[0052] Then, the total compensation amount for this period is calculated:

[0053] ΔStotal(k)=[ΔL·n(k)·Ts+ΔSgap(k)]×η(k)

[0054] The calculated compensated increments are accumulated: S(k) = S(k-1) + ΔStotal(k) to obtain the final real-time cumulative displacement value S(k).

[0055] Step S5: Closed-loop control

[0056] First, the deviation e(k) between the compensated real-time cumulative displacement and the target position is calculated: e(k) = Starget - S(k), where Starget is the preset target position. Then, the error e(k) is input into the digital PID controller, and the speed control command u(k) is calculated using the PID control algorithm. The speed command u(k) is sent to the frequency converter to drive the motor until the position error meets the accuracy requirements (e.g., |e(k)| < 3mm).

[0057] A three-month test was conducted on the billet transfer car using this method in the continuous casting workshop of a steel plant. The results showed that, under conditions of high ambient temperature and heavy dust, the positioning error of the billet transfer car remained within ±3mm, fully meeting the process requirements. In contrast, the original positioning system based on an external laser rangefinder experienced four positioning failures within three months due to signal interference caused by high-temperature radiation and dust adhering to the optical lens.

[0058] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the concept and scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the design concept of the present invention should fall within the protection scope of the present invention.

[0059] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. A high-precision position control method for a continuous casting machine billet transfer car based on motor speed feedback, characterized in that, Includes the following steps: S1. Real-time acquisition of the speed and current signals of the motor driving the billet transfer cart; S2. Based on the mechanical transmission system parameters of the billet transfer car, establish a conversion model between the motor speed and the linear displacement of the billet transfer car; S3. Based on the rotation speed signal and conversion model, calculate the real-time cumulative displacement of the billet transfer car; S4. A dynamic compensation mechanism is introduced in the real-time cumulative displacement calculation process to compensate for displacement errors caused by mechanical transmission clearance and / or load fluctuations. S5. Based on the deviation between the compensated real-time cumulative displacement and the target position, perform closed-loop control on the motor.

2. The high-precision position control method for the billet transfer car of a continuous casting machine based on motor speed feedback according to claim 1, characterized in that, The conversion model described in step S2 is used to calculate the linear displacement ΔL of the moving trolley corresponding to each revolution of the motor, and its expression is: ； Where D is the diameter of the drive wheel, N gear Z represents the number of teeth on the driving gear. chain denoted as the number of links in the transmission chain, and i represents the gear ratio of the reducer.

3. The high-precision position control method for the billet transfer car of a continuous casting machine based on motor speed feedback according to claim 2, characterized in that, The method for calculating the real-time cumulative displacement of the billet transfer car in step S3 is as follows: ； Where S(t) is the cumulative displacement of the billet transfer car from time 0 to time t, in meters; n(τ) is the rotational speed of the motor at time τ after being collected and converted through step S1, in revolutions per second.

4. The high-precision position control method for the billet transfer car of a continuous casting machine based on motor speed feedback according to claim 3, characterized in that, The compensation for the mechanical transmission clearance in step S4 includes: when a change in the movement direction of the transfer cart is detected, a compensation amount based on the dynamic clearance value is superimposed on the calculated displacement.

5. The high-precision position control method for the billet transfer car of a continuous casting machine based on motor speed feedback according to claim 4, characterized in that, The dynamic gap value is an adaptive value that is dynamically adjusted based on ambient temperature, mechanical wear, and the cumulative operating time of the system.

6. The high-precision position control method for the billet transfer car of a continuous casting machine based on motor speed feedback according to claim 3, characterized in that, The compensation for load fluctuations in step S4 includes: estimating the load torque based on the real-time collected motor current signal, and dynamically adjusting a displacement integral weighting coefficient based on the load torque, with the weighting coefficient ranging from (0.95 to 1.00).

7. The high-precision position control method for the billet transfer car of a continuous casting machine based on motor speed feedback according to claim 1, characterized in that, In step S3, before calculating the real-time cumulative displacement, the rotational speed signal is processed using a Kalman filter algorithm to eliminate noise interference.

8. The high-precision position control method for the billet transfer car of a continuous casting machine based on motor speed feedback according to claim 1, characterized in that, In step S5, a PID control algorithm is used for closed-loop control.

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