Self-adaptive speed regulation method based on conveying belts of multiple movable telescopic belt type reversed loader

Abstract

The invention provides a self-adaptive speed regulation method based on conveying belts of multiple movable telescopic belt type reversed loader. The load island phenomenon in the collaborative conveying process of a plurality of movable telescopic belt type reversed loaders can be effectively relieved, the resource utilization rate and the operation efficiency of a conveying system are improved, and meanwhile high-precision and quick-response inter-partition dynamic speed regulation is achieved through direct torque control.

Description

Technical Field

[0001] This invention relates to the field of multi-machine collaborative control of conveyor systems, and in particular to an adaptive speed regulation method for conveyor belts based on multiple mobile telescopic belt transfer machines. Background Technology

[0002] The mobile telescopic belt conveyor is a new type of underground transportation equipment in coal mines. It exhibits significant flexibility and adaptability in complex geological conditions such as steep slopes and frequent turns. The conveyor belt is driven by a motor to transport materials, and its telescopic length can be adjusted within a limited range as needed. This equipment is widely used in scenarios requiring frequent turns and rapid excavation, such as continuous tunneling and continuous mining and filling. A single unit typically transports materials over distances of tens of meters. In practice, multiple units are usually deployed in the tunneling roadway to work together and complete long-distance material transport. Traditional belt conveyors can have conveyor belts that are hundreds or even thousands of meters long. Due to the cutting process, the coal flow along the entire conveyor belt is often isolated, resulting in intermittent coal flow and uneven load distribution. This not only leads to resource waste due to idle sections but also requires manual cleaning due to coal blockages and leaks, increasing labor intensity and transportation costs. While intelligent coal flow technology has been introduced into traditional belt conveyor systems with technological advancements, its speed regulation is systemic and cannot effectively alleviate the isolated load situation.

[0003] Currently, commonly used speed regulation technologies for coal mine tunneling conveyor systems include: (1) Speed ​​regulation of motor frequency converter based on conveyor belt machine; (2) Speed ​​regulation is controlled by a hydraulic proportional valve.

[0004] In scheme (1), the coal flow rate is perceived in real time and the belt rotation speed is optimized by combining sensor monitoring, AI visual recognition, variable frequency speed regulation and IoT control. However, this scheme is limited by the application characteristics of belt conveyors. Under normal circumstances, the conveyor belt of a belt conveyor can be hundreds or even thousands of meters long. Its speed regulation is systematic. Since the amount of coal entering the belt conveyor from the tunneling equipment changes in real time, the load on the entire belt is uneven, resulting in local belt idleness and the risk of coal blockage and leakage. The speed regulation range of this scheme is narrow and cannot effectively solve the phenomenon of isolated coal transport volume. The effect of improving resource utilization is generally average.

[0005] Scheme (2) can achieve stepless speed regulation of the conveyor belt by adjusting the opening of the proportional valve. It has the characteristics of wide speed range and strong resistance to load impact, but the adjustment accuracy is low and it is not suitable for long-distance continuous conveyor belt drive. Summary of the Invention

[0006] The present invention aims to at least partially solve one of the technical problems in the related art.

[0007] Therefore, the first objective of this invention is to propose an adaptive speed control method for conveyor belts of multiple mobile telescopic transfer machines.

[0008] The second objective of this invention is to provide an adaptive speed control device for conveyor belts of multiple mobile telescopic transfer machines.

[0009] To achieve the above objectives, a first aspect of the present invention proposes an adaptive speed control method for conveyor belts of multiple mobile telescopic transfer machines, comprising: S1, the weight and rotation speed data of the material on the conveyor belt of this stage are collected by the weighing sensor and rotation speed sensor of each mobile telescopic belt transfer machine; S2, based on the CAN bus communication module and CAN repeater, constructs a redundant data sharing network between multi-level transfer machines, and transmits the collected data of adjacent transfer machines in real time; S3 uses the PLC controller to calculate the target speed of the conveyor belt at this stage based on the material weight data of the previous stage transfer machine and the preset physical parameters. S4 employs direct torque control technology to adjust the speed of the conveyor motor in this stage through closed-loop control mode, so that the actual speed is dynamically matched with the target speed to achieve regional load balance.

[0010] In one embodiment of the present invention, the method of collecting material weight and rotation speed data of the conveyor belt at each stage through the weighing sensor and rotation speed sensor of each mobile telescopic belt transfer machine further includes: S11, The weighing sensor is installed below the belt idler and collects the weight m of the material conveyed by each transfer machine belt through pressure sensing, in kg; S12, the rotation speed sensor is installed on the end of the drive drum shaft and collects the rotation speed n of each transfer conveyor belt with a sampling period of 100ms, in rad / min.

[0011] In one embodiment of the present invention, the redundant data sharing network between multi-level transfer machines constructed based on the CAN bus communication module and the CAN repeater further includes: S21 establishes a dual-channel redundant communication link between adjacent transfer machines via a CAN repeater, and automatically switches to the backup channel when the main channel signal strength is below -80dBm. The S22 uses the CAN 2.0B protocol for data frame encapsulation. Each data frame contains an 11-bit identifier and an 8-byte payload, with a transmission period of 50ms.

[0012] In one embodiment of the present invention, the step of using a PLC controller to calculate the target rotational speed of the current conveyor belt based on the material weight data of the previous stage transfer machine and in combination with preset physical parameters further includes: S31, based on formula Calculate the target rotational speed n*, where P is the active power of the electric drum in kW, r is the pulley radius in m, μ is the belt friction factor, and g is the acceleration due to gravity. S32, when the material weight m of the previous stage transfer machine is detected to exceed the preset threshold m_max for 3 consecutive sampling cycles, the friction factor μ in the dynamic adjustment formula is μ×1.2.

[0013] In one embodiment of the present invention, the method of adjusting the speed of the conveyor motor in this stage using direct torque control technology through closed-loop control mode further includes: S41, input the difference between the target speed n* and the actual speed n into the PI speed regulator. The PI parameters Kp=0.8 and Ki=0.05 are determined through on-site debugging. S42 uses SVPWM technology to generate three-phase inverter switching signals, with the switching frequency set to 8kHz and the duty cycle calculation accuracy reaching 0.1%.

[0014] In one embodiment of the present invention, it further includes: S5, when the CAN bus communication module detects that the data loss of the adjacent transfer machine exceeds 2 consecutive transmission cycles, it starts the predictive control mode based on local historical data and uses the average coal flow weight m_avg of the last 5 sampling cycles to replace the real-time data for speed adjustment.

[0015] To achieve the above objectives, a second aspect of the present invention provides an adaptive speed control device for conveyor belts of multiple mobile telescopic transfer machines, comprising: The data acquisition module is used to collect the material weight and rotation speed data of the conveyor belt at this stage through the weighing sensor and rotation speed sensor of each mobile telescopic belt transfer machine; The redundant communication network construction module is used to build a redundant data sharing network between multi-level transfer machines based on the CAN bus communication module and CAN repeater, and to transmit the collected data of adjacent transfer machines in real time. The target speed calculation module is used by the PLC controller to calculate the target speed of the conveyor belt at this stage based on the material weight data of the previous stage transfer machine and the preset physical parameters. The speed regulation module is used to adjust the speed of the conveyor motor in this stage through a closed-loop control mode using direct torque control technology, so that the actual speed is dynamically matched with the target speed to achieve load balance in different areas.

[0016] The method and apparatus of this invention can effectively eliminate the load island phenomenon in the conveying system, realize regional dynamic speed regulation and load balancing among multiple mobile telescopic belt transfer machines, improve conveying efficiency and resource utilization, and reduce energy consumption and manual maintenance requirements.

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

[0018] Based on the shortcomings of commonly used speed regulation technologies in tunnel conveying systems, the technical effects of this invention's implementation scheme include, but are not limited to: (1) The maximum length of the conveyor belt of a single mobile telescopic belt transfer machine is about tens of meters. It also has a separate speed control system. The coal flow transportation of multiple mobile telescopic belt transfer machines in the roadway can realize the speed control of the interval. Through the dynamic adjustment of the system, the load islanding of the entire conveying system can be effectively alleviated. (2) By applying direct torque control technology to belt motor to achieve belt speed regulation, the real-time performance and accuracy of belt speed adjustment can be guaranteed. Attached Figure Description

[0019] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a flowchart of an adaptive speed control method for conveyor belts of multiple mobile telescopic transfer machines according to an embodiment of the present invention; Figure 2 This is an architecture diagram of an adaptive speed regulation method for conveyor belts of multiple mobile telescopic transfer machines according to an embodiment of the present invention; Figure 3 This is a structural diagram of a sensor acquisition system according to an embodiment of the present invention; Figure 4 This is a structural diagram of a network communication module according to an embodiment of the present invention; Figure 5 This is a structural diagram of the main controller system according to an embodiment of the present invention; Figure 6 This is a structural diagram of an adaptive speed control device for conveyor belts of multiple mobile telescopic transfer machines according to an embodiment of the present invention. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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 should fall within the scope of protection of the present invention.

[0022] The following description, with reference to the accompanying drawings, describes an adaptive speed control method and apparatus for conveyor belts based on multiple mobile telescopic conveyor transfer machines according to embodiments of the present invention.

[0023] Understandably, the mobile telescopic belt conveyor has a rotation sensor installed on the drive conveyor roller to detect the belt rotation speed, and a load cell installed on the belt idler roller to detect the weight of the material on the belt. The PLC controller collects the data from the rotation sensor and the load cell, and after obtaining the data, the controller calculates and analyzes the data and applies direct torque control technology to adjust the speed of the conveyor motor. Multiple mobile telescopic belt conveyors are deployed in the tunneling roadway. Each device shares data via a CAN bus. The conveyor belt of this level is connected to the conveyor belts of the previous and next levels. During production, all conveyors are in the running state. To solve the problem of isolated coal flow along the entire conveyor belt in traditional conveying systems, and considering the independent characteristics of the conveyor belts of the mobile telescopic belt conveyors in the roadway, the weight of the coal flow in the previous level belt is used as the key variable for adjusting the speed of this level belt. That is, when the weight of the coal flow in the previous level belt is detected to be increasing, the speed of this level belt is continuously increased; when the weight of the coal flow in the previous level belt is detected to be decreasing, the speed of this level belt is continuously decreased. This method of dynamically adjusting the entire conveying system in intervals can effectively alleviate the isolated coal flow on the belt. Due to the use of direct torque control technology, which has the advantages of strong robustness and fast control response, the adjustment accuracy of the belt speed can be guaranteed.

[0024] Example 1 Figure 1 This is a flowchart of an adaptive speed control method for conveyor belts of multiple mobile telescopic transfer machines according to an embodiment of the present invention, such as... Figure 1 and Figure 2 As shown, it includes: S1 collects the material weight and rotation speed data of the conveyor belt at this stage through the weighing sensor and rotation speed sensor of each mobile telescopic belt transfer machine.

[0025] Specifically, in some implementations, the weight and rotational speed of the material on the conveyor belt at each stage are collected using load cells and rotational speed sensors on each mobile telescopic belt transfer machine. This step is based on a sensor acquisition system, such as... Figure 3As shown, 1 represents the sensor acquisition system, which specifically consists of a load cell 1-1 and a speed sensor 1-2, used to monitor the weight of the material on the belt in real time. (unit: ) and belt rotation speed (unit: Weighing sensors are typically installed below belt idlers, employing a high-precision strain gauge structure and possessing an IP67 protection rating. They are suitable for long-term stable operation in the humid and dusty environments of underground coal mines. Their sampling frequency is no less than 100 Hz to ensure real-time response to changes in material weight. Figure 4 As shown, module 2 is the network communication module, consisting of CAN communication module 2-1 and CAN repeater CAN2-2. CAN communication module 2-1 realizes CAN bus data transmission and reception, while CAN repeater 2-1 can extend the CAN communication transmission distance and improve the system's electrical isolation and anti-interference capabilities. Figure 5 As shown, 3 is the main controller system, which is composed of PLC controlling 3-1. It realizes data acquisition and calculation of the sensor acquisition system, and adjusts the speed of the belt drum of the frequency converter through direct torque control.

[0026] The rotational speed sensor is installed at the end of the drive roller shaft. It uses a photoelectric encoder or a magnetoelectric sensor to detect the rotational speed, and has high resolution and anti-interference capabilities. Its output signal is a pulse frequency, which is processed by the PLC controller and converted into angular velocity. In practical applications, this sensor needs to meet the CAN bus communication protocol and support data exchange with adjacent transfer machines to achieve multi-machine collaborative control.

[0027] Through collection and Based on the data, the PLC controller can further calculate the load status of the current and next-level transfer machines, and combine it with formulas. (in The active power of the electric drum is expressed in kW. This is the acceleration due to gravity, expressed in m / s². The coefficient of friction of the belt; Determine the target rotational speed using the pulley radius (in meters). This provides input data for subsequent direct torque control (DTC). This step provides the data foundation for realizing zoned dynamic speed regulation, effectively alleviating the coal quantity island phenomenon in traditional conveying systems and improving overall conveying efficiency and resource utilization.

[0028] Furthermore, S1 includes: S11, the weighing sensor is installed below the belt idler and collects the weight m of the material conveyed by each transfer machine by pressure sensing, in kg.

[0029] Specifically, in some implementations, the weighing sensor is installed below the belt idler and collects the weight of the material conveyed by each transfer conveyor belt through pressure sensing. The unit is Its technical principle is based on mechanical sensing and signal acquisition technology. The load cell typically uses a high-precision strain gauge pressure sensor, installed below the support structure of the conveyor belt idler. The load-bearing action of the idler on the material converts the material's weight into mechanical stress, which is then converted into an electrical signal output through the deformation of the strain gauge. This sensor has an IP67 protection rating and is suitable for the humid and dusty environments of underground coal mines. Its measuring range is typically set to... The sampling frequency is This is to ensure real-time response to dynamic material flows.

[0030] In practical operation, the load cell connects to the PLC controller via an analog or digital interface (such as RS485 or CAN bus) to achieve real-time data acquisition and transmission. The sensor collects material weight data. As a key input parameter in subsequent control algorithms, it is used to calculate the target rotational speed of the next-stage transfer conveyor belt. Its formula is ,in Active power of the electric drum (unit: ), Acceleration due to gravity (unit: ), The coefficient of friction between the belt and the idler roller. The radius of the pulley (unit: This step, by sensing the weight of the material in real time, provides a basis for subsequent speed adjustment based on direct torque control (DTC), thereby enabling flexible speed regulation of the conveying system in different areas, effectively alleviating the load islanding phenomenon, and improving the overall operating efficiency and stability of the system.

[0031] S12, the rotation speed sensor is installed on the end of the drive drum shaft and collects the rotation speed n of each transfer conveyor belt with a sampling period of 100ms, in rad / min.

[0032] Specifically, in some implementations, the rotational speed sensor is mounted on the end of the drive roller shaft to collect the rotational speed of the belt of each mobile telescopic conveyor at a sampling period of 100ms. The unit is This step is one of the key links in realizing dynamic response control in the entire adaptive speed regulation system, and its technical implementation is based on a high-precision rotation detection and real-time data acquisition mechanism.

[0033] Rotational speed sensors typically employ photoelectric encoders or magnetoelectric speed sensors, mounted on the output shaft of the drive roller. They sense pulse signals through the shaft's rotational motion. The encoder's resolution should be no less than 1024 pulses / revolution to ensure sufficient angular velocity accuracy even at low speeds. The sensor's output signal is acquired by a high-speed counting module in the PLC controller, with a sampling period set to 100ms, meaning 10 speed data acquisitions per second, meeting the system's basic requirements for dynamic response. During data acquisition, the controller counts and timestamps the pulse signals, converting the number of pulses per unit time into angular velocity. The calculation formula is as follows:

[0034] in, This represents the number of pulses collected within the sampling period. The sampling period is The number of pulses per encoder revolution (unit: ), 60000 is the unit to be transferred from Convert to Conversion factor.

[0035] This procedure applies to collaborative operation systems of multiple mobile telescopic belt conveyors in complex underground coal mine roadways. Because each conveyor has a short conveying distance (typically tens of meters), its independent control characteristics allow for greater flexibility and faster response in speed acquisition and adjustment. Data sharing between multiple devices is achieved via a CAN bus. The controller can dynamically adjust the speed of its own conveyor belt based on the coal flow weight information from the upstream conveyor, thereby achieving load balancing and coal flow continuity.

[0036] The technical value of this step lies in providing real-time and accurate speed feedback signals for subsequent direct torque control (DTC), which is the foundation for achieving closed-loop control. (Combined with the formula...) The controller can calculate the target rotational speed and compare it with the actual collected data. The motor speed is precisely adjusted by comparing the output signals from the PI controller to the inverter. Therefore, this step is crucial for improving system control accuracy, reducing energy consumption, and minimizing the risks of coal blockage and leakage.

[0037] S2, based on the CAN bus communication module and CAN repeater, constructs a redundant data sharing network between multi-level transfer machines, and transmits the collected data of adjacent transfer machines in real time.

[0038] Specifically, this step involves constructing a redundant data sharing network among multiple transfer conveyors based on a CAN bus communication module and a CAN repeater. This enables real-time transmission of data collected by adjacent transfer conveyors and is a key step in achieving multi-machine collaborative control and adaptive speed regulation in this invention. In some implementations, this network structure adopts the CAN 2.0B protocol standard, with a communication rate configurable from 125 kbps to 1 Mbps to meet the stable data transmission requirements of the complex electromagnetic environment within the tunnel. The CAN bus communication module is deployed in the PLC controller of each mobile telescopic belt transfer conveyor, responsible for collecting data from the weighing and rotation speed sensors of its own level and encapsulating the data in a standard CAN frame format (such as an 11-bit identifier) ​​before sending it to adjacent transfer conveyors.

[0039] Furthermore, the CAN repeater 2-2 is used to extend the communication distance, typically supporting a maximum transmission distance of up to 1.5 km, and features electrical isolation to effectively suppress signal interference caused by the high humidity and dust environment in the tunnel. The repeater supports multi-level cascading deployment, ensuring reliable data transmission even when multiple transfer conveyors are connected in series. In practical applications, the PLC controller of each transfer conveyor periodically receives material weight data m (unit: kg) and rotational speed n (unit: rad / min) from the previous level transfer conveyor via the CAN bus, and performs real-time analysis in conjunction with local sensor data to determine the target rotational speed of the current level conveyor belt. Where p is the active power of the electric drum (unit: kW), g is the acceleration due to gravity (9.81 m / s²), μ is the belt friction coefficient, and r is the pulley radius (unit: m).

[0040] This step, by constructing a redundant communication network, ensures that even if communication at a certain node is interrupted, the system can still transmit and forward data via repeaters, thereby improving the overall system reliability and real-time performance. Its technical value lies in providing accurate and timely coal flow status information for subsequent direct torque control (DTC), enabling flexible speed regulation in different zones, effectively alleviating load islanding, and improving the operating efficiency and energy utilization of the conveying system.

[0041] Furthermore, S2 includes: S21 establishes a dual-channel redundant communication link between adjacent transfer machines via a CAN repeater, and automatically switches to the backup channel when the main channel signal strength is below -80dBm.

[0042] Specifically, in some implementations, this invention establishes a dual-channel redundant communication link between adjacent mobile telescopic conveyor belt transfer machines using CAN repeaters to ensure the stability and reliability of data transmission in complex tunnel environments. CAN bus, as a serial communication protocol widely used in industrial control, features high real-time performance, strong anti-interference capabilities, and good node scalability, making it suitable for scenarios involving collaborative control of multiple devices in underground coal mines. In this technical solution, each transfer machine is equipped with a CAN communication module, and data relay and forwarding between adjacent devices are achieved through CAN repeaters, thereby constructing a redundant communication structure with parallel main and backup channels.

[0043] In the specific implementation, CAN repeaters are deployed at communication nodes between adjacent transfer machines. They support the CAN 2.0B protocol standard, with a communication rate configurable from 125 kbps to 1 Mbps, preferably 500 kbps to balance real-time performance and anti-interference capability. The main channel and backup channel are connected via independent CAN physical buses, forming two parallel data transmission paths. Under normal operating conditions, the main channel is prioritized for real-time data transmission, including material weight collected by the weighing sensor. (Unit: kg) and belt speed collected by the speed sensor (Unit: rad / min), and control commands output by the PLC controller.

[0044] When the signal strength of the main channel is lower than the set threshold When necessary, the system automatically triggers a channel switching mechanism through the signal detection module, switching data transmission to the backup channel. This switching process combines hardware-level signal quality assessment with software-level protocol arbitration to ensure seamless switching and data integrity. During the switching process, the CAN repeater identifies signal quality degradation through the arbitration mechanism and completes the channel switching within 100 ms, avoiding control delays caused by communication interruptions.

[0045] This step plays a crucial role in the overall technical solution. Through the establishment and automatic switching mechanism of redundant communication links, it effectively improves the communication stability of the multi-transfer conveyor collaborative control system, thereby ensuring the real-time performance and accuracy of conveyor belt speed regulation based on Direct Torque Control (DTC). In practical applications, this technology is particularly suitable for underground coal mine scenarios with complex roadway environments, severe electromagnetic interference, and long communication distances, providing a reliable data transmission foundation for achieving flexible intelligent speed regulation in different zones.

[0046] The S22 uses the CAN 2.0B protocol for data frame encapsulation. Each data frame contains an 11-bit identifier and an 8-byte payload, with a transmission period of 50ms.

[0047] Specifically, in some implementations, this invention uses the CAN 2.0B protocol for data frame encapsulation to achieve efficient and reliable communication between multiple mobile telescopic conveyor belt transfer machines. The CAN 2.0B protocol supports 11-bit standard identifiers and 29-bit extended identifiers; this embodiment uses 11-bit standard identifiers to meet the needs of scenarios with a limited number of devices and a relatively fixed communication structure within the tunnel. Each data frame contains an 8-byte payload (Data Field) used to transmit key operating parameters, such as belt speed, material weight, and power status, conforming to the definition of the CAN frame structure in the ISO 11898-1 standard.

[0048] The CAN 2.0B protocol data frame consists of a Start of Frame (SOF), an arbitration segment (including an identifier), a control segment, a data segment, a CRC segment, an acknowledgment segment, and a End of Frame. The data segment is 8 bytes long and can carry up to 64 bits of data, suitable for real-time data exchange between the PLC controller and adjacent transfer machines in this invention. The transmission cycle is set to 50ms to ensure sufficient system response speed to support the execution of dynamic speed control logic. This cycle parameter can be fine-tuned in practical applications based on roadway length, number of devices, and communication load, but 50ms is sufficient for the collaborative control requirements of most tunneling roadways.

[0049] This step is used to build the communication infrastructure for multi-machine collaborative control. Each transfer conveyor connects to adjacent devices via a CAN bus, forming a distributed control network. The PLC controller periodically encapsulates the data collected by the speed and weighing sensors into CAN frames and sends them to the upstream and downstream transfer conveyors within a set 50ms period, achieving real-time sharing of coal flow status. Simultaneously, the controller receives CAN frame data from adjacent transfer conveyors to determine changes in the coal flow weight of the upstream conveyor, thereby adjusting the speed of its own conveyor to achieve flexible speed regulation in different areas.

[0050] The standardized CAN 2.0B protocol encapsulation and periodic transmission mechanism ensure the real-time performance and reliability of the data, providing stable data support for subsequent direct torque control (DTC) and interval speed regulation strategies. (Combined with the formula...) The controller can determine the weight of the coal flow based on the previous stage transfer conveyor. and active power Calculate the target rotational speed using parameters such as [parameter name]. This allows for dynamic adjustments, effectively alleviating load islanding and improving overall system efficiency and stability.

[0051] S3 uses the PLC controller to calculate the target speed of the conveyor belt at this stage based on the material weight data of the previous stage transfer machine and the preset physical parameters.

[0052] Specifically, in some implementations, the PLC controller calculates the target speed of the conveyor belt at this stage based on the material weight data from the previous stage transfer machine and preset physical parameters. This is a key control step in the adaptive speed regulation method of this invention. This step is based on direct torque control (DTC) technology, combined with a sensor acquisition system and a CAN bus communication module, to achieve dynamic adjustment of the conveyor belt speed, thereby optimizing the material flow state of the entire conveying system.

[0053] The PLC controller first receives the material weight data collected by the weighing sensor of the upstream transfer conveyor via the CAN bus. The unit is Meanwhile, the controller has several preset physical parameters, including the belt friction coefficient. Gravitational acceleration (usually taken) and the radius of the drive roller The unit is In addition, the controller also needs to obtain the active power of the conveyor belt motor at this level. The unit is Based on these parameters, the controller calculates the target speed of the conveyor belt in this stage using the following formula:

[0054] This formula reflects the dynamic relationship between power and material weight. By adjusting the rotational speed, the conveying system can maintain optimal material conveying efficiency under different load conditions.

[0055] The calculation accuracy of the PLC controller must meet the following requirements. The error range is set to ensure the stability of speed regulation. Meanwhile, the CAN bus communication rate is typically set to... To ensure real-time data transmission, the sampling frequency of the weighing sensor is recommended to be no less than [specified frequency]. The resolution of the speed sensor should reach This is to improve the system's ability to perceive the state of material flow.

[0056] This procedure is applicable to collaborative operations of multiple mobile telescopic belt conveyors in complex underground coal mine roadways. Because each conveyor has a relatively short conveying distance (typically tens of meters), its independent control characteristics allow the conveyor belt to respond quickly to the load status of the preceding conveyor, thereby achieving flexible speed regulation within sections and effectively alleviating the "coal quantity island" phenomenon that occurs in traditional conveying systems.

[0057] This step, by calculating the target speed in real time and combining it with direct torque control technology, achieves high-precision closed-loop control of the motor speed, significantly improving the dynamic response capability and load balancing level of the conveying system, reducing energy consumption and maintenance costs, and improving overall transportation efficiency and system stability.

[0058] Furthermore, S3 includes: S31, based on formula Calculate the target rotational speed n*, where P is the active power of the electric drum in kW, r is the radius of the pulley in m, μ is the belt friction factor, and g is the acceleration due to gravity.

[0059] Specifically, in some implementations, based on formulas Calculating the target rotational speed is one of the core control logics for achieving adaptive speed regulation of the conveyor belt in this invention. This step involves collecting the current weight of the material on the conveyor belt. Combined with the active power of the electric drum Belt pulley radius The coefficient of friction between the belt and the roller and gravitational acceleration It dynamically calculates the target speed that the next stage transfer machine should be adjusted to, thereby realizing flexible speed regulation control in different regions.

[0060] This formula is based on the principles of mechanics and energy conservation, and calculates the active power output by the motor. (Unit: kW) is converted into the basis for controlling the belt speed. Specifically, the active power of the electric drum... It is closely related to the belt's traction, speed, and friction characteristics. By... With pulley radius Multiplying these together gives the traction torque output by the roller, which can then be combined with the weight of the material. Gravitational acceleration and coefficient of friction This allows us to derive the target speed required for the belt under the current load conditions. In this formula, 60000 is a unit conversion factor used to unify the physical quantities between power (kW) and speed (rad / min).

[0061] Typically, data is collected in real time by frequency converters or power sensors, with an accuracy requirement of ±1%. The load is measured by a weighing sensor on the belt roller, with a sampling frequency of 10 Hz and a range of 0~500 kg; Take standard gravitational acceleration ; The coefficient of friction between the belt and the roller is typically between 0.2 and 0.4, varying depending on the belt material and the surface treatment of the roller. The radius of the pulley is measured in meters (m), and its value is determined by the equipment's structural parameters, generally ranging from 0.1 to 0.3 m.

[0062] This procedure applies to conveyor systems consisting of multiple mobile telescopic belt conveyors in underground coal mines. Each conveyor shares data via a CAN bus, and the PLC controller uses the material weight from the previous conveyor to control the data. Combined with the power of this level of electric drum Based on the structural parameters, the target speed that the next stage conveyor should be adjusted to is calculated and used as the set value of the direct torque control (DTC) system. The inverter is then closed-loop controlled through SVPWM technology, thereby achieving precise adjustment of the belt speed.

[0063] By combining power and load parameters, dynamic speed regulation based on a physical model is achieved, effectively alleviating the load islanding problem caused by uneven coal flow in traditional conveying systems. Simultaneously, this method possesses excellent real-time performance and control accuracy, providing reliable data support and control basis for multi-machine collaborative control, significantly improving the operating efficiency and resource utilization of the conveying system.

[0064] S32, when the material weight m of the previous stage transfer machine is detected to exceed the preset threshold m_max for 3 consecutive sampling cycles, the friction factor μ in the dynamic adjustment formula is μ×1.2.

[0065] Specifically, in some implementations, when the weight of the material on the upstream transfer machine is detected... Exceeding the preset threshold for 3 consecutive sampling periods At that time, the system will dynamically adjust the friction factor. for This step, based on direct torque control (DTC) technology and a closed-loop feedback mechanism, aims to improve the response and operational stability of the conveyor belt under high load conditions.

[0066] This step first relies on load cells to monitor the weight of the material on the conveyor belt of the upstream transfer machine in real time. The sampling frequency of the load cells is typically set to 10 Hz to 20 Hz to ensure data continuity and real-time performance. The weight of the material is measured over three consecutive sampling periods. All exceeded the set limits (Unit: kg), the PLC controller will trigger friction factors. The adjustment logic. Friction factors. It is a key parameter affecting belt traction and motor output power, and its adjustment will directly affect the calculation results of subsequent speed regulation formulas.

[0067] Friction factor The initial value is usually calibrated based on the belt material, surface condition, and material characteristics, generally ranging from 0.2 to 0.5. When the system detects a high load condition, it will... Upgraded to This adjustment enhances the friction between the belt and the rollers, thereby increasing traction and preventing slippage. This strategy is applicable to the dynamic coordination control between adjacent transfer machines in a CAN bus communication system, ensuring stable system operation even under sudden load changes.

[0068] This step is primarily applied to collaborative operations of multiple mobile telescopic belt conveyors in complex underground coal mine roadways. Due to the significant undulations and frequent turns in the roadways, material can easily accumulate locally during the transfer process, leading to a sudden increase in the load on the upstream conveyor. This is addressed through dynamic adjustment. The system can anticipate and enhance the traction capacity of the next-level transfer machine, thereby achieving a smooth load transition and improving conveying efficiency.

[0069] This step, by introducing a dynamic compensation mechanism for friction factors, effectively improves the robustness and adaptability of the DTC control model under high load conditions. (Combined with the formula...) Friction factors The adjustment directly affects the calculation result of the target revolutions, thereby achieving precise control of the motor speed. This method reduces the risk of coal blockage and leakage while improving the overall resource utilization and operating efficiency of the conveying system.

[0070] S4 employs direct torque control technology to adjust the speed of the conveyor motor in this stage through closed-loop control mode, so that the actual speed is dynamically matched with the target speed to achieve regional load balance.

[0071] Specifically, in some implementations, this invention employs Direct Torque Control (DTC) technology to dynamically adjust the speed of the conveyor motor in the current stage through a closed-loop control mode, thereby achieving load balancing in different areas. This step is the core control link of the entire adaptive speed regulation system, and its technical implementation is based on real-time sensing of the weight of the material on the previous stage conveyor belt, combined with the operating status of the current stage belt for responsive speed regulation.

[0072] DTC control uses a PLC controller to collect data from the speed sensor and load cell of the conveyor belt at this stage. The speed sensor is used to detect the real-time rotational speed of the belt rollers. (Unit: rad / min) The load cell is used to obtain the weight of the material on the conveyor belt. (Unit: kg). The controller dynamically sets the target speed of the current belt based on the material weight variation trend of the previous belt. The calculation formula is as follows: ,in The active power of the electric drum (unit: kW). The acceleration due to gravity (approximately) ), The coefficient of friction between the belt and the material. Where is the pulley radius (unit: m). This formula reflects the dynamic relationship between power and load, providing a theoretical basis for subsequent closed-loop control.

[0073] The controller compares the target speed. Compared with actual speed The difference is used to adjust the inverter output using a proportional-integral (PI) controller, thereby controlling the motor's torque and speed. The parameters of the PI controller... and Tuning is required based on the system's response speed and stability; typically... Settings Within the range, Settings Within a certain range, to ensure that the system can maintain a fast response and stable output even under sudden load changes.

[0074] This procedure applies to conveying systems consisting of multiple mobile telescopic belt conveyors in underground coal mines. Since each conveyor has a short conveying distance (typically tens of meters) and an independent drive and control system, data sharing and collaborative control between the devices can be achieved via a CAN bus. In actual operation, when the upstream conveyor detects an increase in coal flow weight, the controller will increase the speed of its own motor to match the material conveying demand; conversely, it will decrease the speed, thereby achieving load balancing in different areas.

[0075] The high responsiveness and robustness of DTC technology enable precise control of the conveyor motor speed, effectively alleviating the "island" phenomenon caused by uneven coal flow in traditional conveying systems, improving the overall resource utilization and operating efficiency of the system, and reducing the need for manual intervention, thus having significant engineering practical value.

[0076] Furthermore, S4 includes: S41, input the difference between the target speed n* and the actual speed n into the PI speed regulator. The PI parameters Kp=0.8 and Ki=0.05 are determined through on-site debugging.

[0077] Specifically, in some implementations, the target speed is compared with the actual speed. The differential input PI speed regulator is a key control component in the closed-loop speed regulation system based on direct torque control (DTC) in this invention. This step uses a proportional-integral (PI) control algorithm to dynamically compensate for speed deviations, thereby achieving high-precision regulation of the conveyor motor speed and ensuring continuous and stable material transport between multiple mobile telescopic belt conveyors.

[0078] Specifically, the PI speed regulator receives a real-time speed signal from the speed sensor. It is then compared with the set target speed to calculate the speed deviation. This deviation value serves as the input to the PI controller, which adjusts the input based on the proportional gain. and integral gain The deviation is weighted, and the output control quantity is used to adjust the inverter's output voltage and frequency, thereby controlling the motor's torque and speed. PI parameters and It was determined through on-site commissioning to adapt to the dynamic response requirements and steady-state error control under different operating conditions.

[0079] proportionality coefficient Primarily used for rapid response to speed deviations, improving the dynamic performance of the system; integral coefficient This is used to eliminate steady-state errors and ensure that the system maintains speed stability during long-term operation. The output signal of the PI controller is usually an analog or digital signal, which is transmitted to the frequency converter via the CAN bus to achieve real-time speed control of the motor.

[0080] The PLC control system deployed in each mobile telescopic conveyor belt transfer machine, combined with direct torque control technology, achieves high-precision closed-loop control of the conveyor drum motor. Because each device has independent speed regulation capabilities and data sharing is achieved through the CAN bus, flexible speed regulation can be implemented in sections along the entire conveying line, effectively alleviating the phenomenon of isolated coal quantities and improving the overall material conveying efficiency and energy utilization of the system.

[0081] This PI control step can significantly improve the response speed and control accuracy of the conveying system, ensuring coordinated operation among various transfer machines in the tunneling environment where coal flow changes frequently, reducing the occurrence of abnormal situations such as coal blockage and leakage, thereby reducing maintenance costs and improving the intelligence level and operational stability of the transportation system.

[0082] S42 uses SVPWM technology to generate three-phase inverter switching signals, with the switching frequency set to 8kHz and the duty cycle calculation accuracy reaching 0.1%.

[0083] Specifically, in some implementations, this invention employs Space Vector Pulse Width Modulation (SVPWM) technology to generate switching signals for the three-phase inverter, thereby achieving high-precision speed control of the transmission motor. SVPWM is a voltage space vector-based modulation strategy that, compared to traditional SPWM technology, provides higher voltage utilization and lower harmonic distortion at the same switching frequency, thus improving the efficiency and dynamic response performance of motor control.

[0084] SVPWM approximates a reference voltage vector by synthesizing the three-phase voltages into a rotating voltage space vector and selecting adjacent basic voltage vectors within a hexagonal voltage vector space for synthesis. In this invention, the switching frequency of the three-phase inverter is set to 8kHz. This frequency ensures the system's dynamic response while also controlling switching losses and electromagnetic interference. The switching frequency setting must meet the switching characteristics and heat dissipation capabilities of power electronic devices (such as IGBTs), and a range of 5-10kHz is typically a reasonable choice for industrial applications.

[0085] The duty cycle calculation accuracy reaches 0.1%, meaning that within the 0-100% range, the minimum resolution of the duty cycle is 0.1%. This accuracy is achieved by the PWM module inside the controller (such as a PLC), which typically requires at least 10 bits of resolution to ensure good control accuracy even in low duty cycle ranges. The duty cycle is calculated based on the difference between the target speed and the actual speed. A PI controller outputs a control quantity, which in turn adjusts the switching state of the three-phase inverter, achieving closed-loop control of the motor speed.

[0086] This step is applied to the collaborative control system of multiple mobile telescopic conveyor belt transfer machines, where each machine achieves data sharing and communication via a CAN bus. In actual operation, when the PLC controller receives the material weight signal from the upstream transfer machine, it calculates the weight according to the formula... The target speed is calculated, and precise three-phase switching signals are generated using SVPWM technology to drive the inverter to output voltages with corresponding frequency and amplitude, thereby adjusting the motor speed and achieving dynamic load balance in the conveying system.

[0087] This step, through high-precision duty cycle control and an 8kHz switching frequency, significantly improves the waveform quality and control response speed of the inverter output voltage, providing a stable and efficient execution platform for direct torque control (DTC). This ensures the real-time and accurate regulation of the conveyor belt speed, effectively alleviating the coal quantity isolation phenomenon in traditional conveying systems and improving overall transportation efficiency and energy utilization. Also includes: S5, when the CAN bus communication module detects that the data loss of the adjacent transfer machine exceeds 2 consecutive transmission cycles, it starts the predictive control mode based on local historical data and uses the average coal flow weight m_avg of the last 5 sampling cycles to replace the real-time data for speed adjustment.

[0088] Specifically, in some implementations, when the CAN bus communication module detects that data loss from an adjacent transfer conveyor has exceeded two consecutive transmission cycles, the system will automatically switch to a predictive control mode based on local historical data. The core technical principle of this step lies in using a redundant data processing mechanism to ensure the stable operation of the transfer conveyor belt even in the event of communication failure, thereby avoiding imbalances in the conveying system or material accumulation caused by data interruption.

[0089] The specific implementation is as follows: The PLC controller periodically collects data from the weighing and speed sensors of the current transfer conveyor and sends this data to the previous and next level transfer conveyors via the CAN bus module. Under normal communication conditions, the controller adjusts the speed based on the real-time coal flow weight of adjacent transfer conveyors. When the CAN bus module detects that an adjacent transfer conveyor has not received valid data for two consecutive transmission cycles (usually 100ms per cycle), it determines that data loss has occurred, and the system automatically uses local historical data for predictive control. At this time, the controller performs a moving average calculation on the coal flow weight data from the most recent five sampling cycles (each cycle interval is 100ms) to obtain a replacement value for the current coal flow weight. This serves as the basis for adjusting the speed of the conveyor belt of the transfer machine at this level.

[0090] The sampling period is set to 100ms, and the historical data window length is 5 periods, meaning the system retains coal flow weight data from the most recent 500ms. The moving average algorithm uses either a weighted average or an equal-weighted average; in the specific implementation, an equal-weighted average can be optionally used to simplify the calculation. The formula is as follows:

[0091] in This represents the weight of the coal flow in the i-th sampling period, in kg. This substitute value will serve as a key input parameter for calculating the target revolutions in subsequent direct torque control (DTC) to maintain the dynamic balance of the conveying system.

[0092] In practical applications, this step is suitable for scenarios where multiple transfer conveyors operate collaboratively in complex underground coal mine roadways. It is particularly effective in ensuring the continuity and stability of the conveying system when CAN bus communication is interfered with or malfunctions. Through predictive control based on local historical data, the system can maintain a reasonable coal flow conveying speed even during communication interruptions, thereby reducing the risk of decreased conveying efficiency and equipment downtime caused by communication failures.

[0093] This step significantly improves the system's fault tolerance and operational continuity, ensuring that the transfer machine can still adaptively adjust its speed based on historical data in the event of communication failures, thus preventing the exacerbation of coal flow islanding and improving the overall resource utilization and operational efficiency of the conveying system.

[0094] The adaptive speed regulation method for conveyor belts based on multiple mobile telescopic belt transfer machines in this invention realizes regional dynamic speed regulation among multiple mobile telescopic belt transfer machines, effectively alleviating the load islanding phenomenon in the conveying system, improving the continuity of coal flow transportation and resource utilization, and improving the accuracy and response speed of speed regulation through direct torque control.

[0095] Example 2 To achieve the above embodiments, such as Figure 6 As shown, this embodiment also provides an adaptive speed control device 10 based on the conveyor belts of multiple mobile telescopic transfer machines, including: The data acquisition module 100 is used to collect the material weight and rotation speed data of the conveyor belt at this stage through the weighing sensor and rotation speed sensor of each mobile telescopic belt transfer machine. The redundant communication network construction module 200 is used to build a redundant data sharing network between multi-level transfer machines based on the CAN bus communication module and the CAN repeater, and to transmit the collected data of adjacent transfer machines in real time. The target speed calculation module 300 is used to calculate the target speed of the conveyor belt at this stage based on the material weight data of the previous stage transfer machine and the preset physical parameters using the PLC controller. The speed regulation module 400 is used to regulate the speed of the conveyor motor in this stage through a closed-loop control mode using direct torque control technology, so that the actual speed is dynamically matched with the target speed to achieve load balance in different areas.

[0096] Furthermore, the data acquisition module is also used for: The weight of the material conveyed by each transfer conveyor belt is collected by a weighing sensor installed under the belt idler, in kg. The rotational speed n of each transfer conveyor belt is collected by a rotational speed sensor installed at the end of the drive drum shaft with a sampling period of 100ms, and the unit is rad / min.

[0097] Furthermore, the redundant communication network building module is also used for: A dual-channel redundant communication link is established between adjacent transfer machines using a CAN repeater. When the signal strength of the main channel is lower than -80dBm, it automatically switches to the backup channel. The data frames are encapsulated using the CAN 2.0B protocol. Each data frame contains an 11-bit identifier and an 8-byte payload, and the transmission period is set to 50ms.

[0098] Furthermore, the target speed calculation module is also used for: Based on formula Calculate the target rotational speed n*, where P is the active power of the electric drum in kW, r is the pulley radius in m, μ is the belt friction factor, and g is the acceleration due to gravity. When the material weight m of the upstream transfer machine exceeds the preset threshold m_max for three consecutive sampling cycles, the friction factor μ in the dynamic adjustment formula is set to μ×1.2.

[0099] The adaptive speed control device for conveyor belts of multiple mobile telescopic transfer conveyors in this invention uses sensor acquisition technology, network transmission technology, and direct torque control technology to achieve flexible and intelligent speed control of the entire conveyor line in different areas, which can effectively reduce the operating and maintenance costs of tunneling and transportation.

[0100] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0101] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

Claims

1. A method for adaptive speed regulation of conveyor belts based on multiple mobile telescopic belt transfer machines, characterized in that, include: S1, the weight and rotation speed data of the material on the conveyor belt of this stage are collected by the weighing sensor and rotation speed sensor of each mobile telescopic belt transfer machine; S2, based on the CAN bus communication module and CAN repeater, constructs a redundant data sharing network between multi-level transfer machines, and transmits the collected data of adjacent transfer machines in real time; S3 uses the PLC controller to calculate the target speed of the conveyor belt at this stage based on the material weight data of the previous stage transfer machine and the preset physical parameters. S4 employs direct torque control technology to adjust the speed of the conveyor motor in this stage through closed-loop control mode, so that the actual speed is dynamically matched with the target speed to achieve regional load balance.

2. The method as described in claim 1, characterized in that, The method of collecting material weight and rotation speed data of the conveyor belt at each stage through the weighing sensor and rotation speed sensor of each mobile telescopic belt transfer machine also includes: S11, the load cell is installed below the belt idler and collects the weight m of the material conveyed by each transfer conveyor belt through pressure sensing, in kg; S12, the rotation speed sensor is installed at the end of the drive drum shaft, and collects the belt rotation speed n of each transfer machine at a sampling period of 100ms, in rad / min.

3. The method as described in claim 1, characterized in that, The redundant data sharing network between multi-level transfer machines built based on the CAN bus communication module and CAN repeater also includes: S21 establishes a dual-channel redundant communication link between adjacent transfer machines via a CAN repeater, and automatically switches to the backup channel when the main channel signal strength is below -80dBm. The S22 uses the CAN 2.0B protocol for data frame encapsulation. Each data frame contains an 11-bit identifier and an 8-byte payload, with a transmission period of 50ms.

4. The method as described in claim 1, characterized in that, The calculation of the target rotation speed of the current conveyor belt using a PLC controller based on the material weight data from the previous transfer machine and preset physical parameters also includes: S31, based on formula Calculate the target rotational speed n*, where P is the active power of the electric drum in kW, r is the pulley radius in m, μ is the belt friction factor, and g is the acceleration due to gravity. S32, when the material weight m of the previous stage transfer machine is detected to exceed the preset threshold m_max for 3 consecutive sampling cycles, the friction factor μ in the dynamic adjustment formula is μ×1.

2.

5. The method as described in claim 1, characterized in that, The method of using direct torque control technology to adjust the speed of the conveyor motor in this stage through closed-loop control mode also includes: S41, input the difference between the target speed n* and the actual speed n into the PI speed regulator. The PI parameters Kp=0.8 and Ki=0.05 are determined through on-site debugging. S42 uses SVPWM technology to generate three-phase inverter switching signals, with the switching frequency set to 8kHz and the duty cycle calculation accuracy reaching 0.1%.

6. The method as described in claim 1, characterized in that, Also includes: S5, when the CAN bus communication module detects that the data loss of the adjacent transfer machine exceeds 2 consecutive transmission cycles, it starts the predictive control mode based on local historical data and uses the average coal flow weight m_avg of the last 5 sampling cycles to replace the real-time data for speed adjustment.

7. An adaptive speed control device for conveyor belts of multiple mobile telescopic belt transfer machines, characterized in that, include: The data acquisition module is used to collect the material weight and rotation speed data of the conveyor belt at this stage through the weighing sensor and rotation speed sensor of each mobile telescopic belt transfer machine; The redundant communication network construction module is used to build a redundant data sharing network between multi-level transfer machines based on the CAN bus communication module and CAN repeater, and to transmit the collected data of adjacent transfer machines in real time. The target speed calculation module is used by the PLC controller to calculate the target speed of the conveyor belt at this stage based on the material weight data of the previous stage transfer machine and the preset physical parameters. The speed regulation module is used to adjust the speed of the conveyor motor in this stage through a closed-loop control mode using direct torque control technology, so that the actual speed is dynamically matched with the target speed to achieve load balance in different areas.

8. The apparatus as claimed in claim 7, characterized in that, The data acquisition module is also used for: The weight of the material conveyed by each transfer conveyor belt is collected by a weighing sensor installed under the belt idler, in kg. The rotational speed n of each transfer conveyor belt is collected by a rotational speed sensor installed at the end of the drive drum shaft with a sampling period of 100ms, and the unit is rad / min.

9. The apparatus as claimed in claim 7, characterized in that, The redundant communication network construction module is also used for: A dual-channel redundant communication link is established between adjacent transfer machines using a CAN repeater. When the signal strength of the main channel is lower than -80dBm, it automatically switches to the backup channel. The data frames are encapsulated using the CAN 2.0B protocol. Each data frame contains an 11-bit identifier and an 8-byte payload, and the transmission period is set to 50ms.

10. The apparatus as claimed in claim 7, characterized in that, The target speed calculation module is also used for: Based on formula Calculate the target rotational speed n*, where P is the active power of the electric drum in kW, r is the pulley radius in m, μ is the belt friction factor, and g is the acceleration due to gravity. When the material weight m of the upstream transfer machine exceeds the preset threshold m_max for three consecutive sampling cycles, the friction factor μ in the dynamic adjustment formula is set to μ×1.2.

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