Intelligent positioning control method for fixed-length doffing of rotor spinning doffing trolley

Abstract

The invention belongs to the technical field of automatic control of textile machinery, and particularly relates to an intelligent positioning control method for fixed-length doffing of a rotor spinning doffing dolly, which dynamically triggers a doffing instruction based on the accumulated winding length of each spindle position, and combines an improved nearest neighbor path optimization algorithm and a two-section type interruption driving accurate positioning mechanism to realize the intelligent positioning control of the fixed-length doffing of the rotor spinning doffing dolly. Sub-millimeter stopping and full-automatic mechanical creeling are carried out on a full-barrel spindle position according to the shortest one-way path; meanwhile, according to the method, encoder data are collected in real time through an upper monitoring subsystem, a cruising path is dynamically planned through a doffing control programmable logic controller, deceleration braking is triggered through double edges of a sensing mechanism, and high-precision, high-efficiency and low-interference-risk intelligent doffing operation is ensured. The problems that due to synchronous doffing of an existing complete machine, yarn length deviation is large, paths are redundant, and positioning precision is insufficient are solved.

Description

Technical Field

[0001] This invention belongs to the field of textile machinery automation control technology, specifically relating to a fixed-length doffing intelligent positioning control method for rotor spinning doffing carriages. Background Technology

[0002] Rotor spinning, as an important technological branch of modern short-fiber spinning, is widely used in cotton spinning, chemical fiber, and blended spinning fields due to its advantages such as high output, high efficiency, and strong adaptability to raw materials. In the continuous production process of rotor spinning machines, the doffing stage, as a key node connecting spinning and subsequent processes, directly affects the overall machine operating efficiency, yarn formation consistency, and the stability of subsequent winding and doubling processes due to its automation level and control precision. As the textile industry accelerates its evolution towards intelligence and flexibility, higher demands are placed on the precision, timeliness, and system coordination capabilities of doffing operations. The traditional doffing mode, which relies on fixed rhythms and mechanical sequences, can no longer meet the current comprehensive goals of high-quality, low-loss, and minimally manned production.

[0003] Currently, most mainstream rotor spinning equipment adopts a synchronized doffing strategy, where a doffing trolley sequentially traverses all spindles along a preset track, performing doffing actions according to a uniform timing sequence regardless of whether each bobbin is full. Its core components typically include a track guide mechanism, pneumatic or electric actuators, and a time- or position-triggered sequence controller, enabling the completion of periodic doffing tasks without complex sensor feedback. In the context of limited automation and relatively relaxed production schedules in earlier equipment, this approach effectively simplified the control system logic and ensured basic operational reliability through standardized operating procedures.

[0004] However, this "one-size-fits-all" doffing mechanism essentially ignores the actual winding length variation at each spindle caused by factors such as raw material fluctuations, tension differences, and yarn breakage rejoining, resulting in significant deviations in the yarn length of the produced yarn bobbins. Such length inconsistencies not only easily lead to problems such as sudden tension changes and frequent yarn breaks during subsequent unwinding processes, but may also cause an imbalance in the fixed length ratio of the entire batch of yarn, seriously affecting the process stability and finished product quality in the weaving or knitting stages.

[0005] Furthermore, with the continuous development of related technologies and the increasingly stringent performance requirements of application scenarios, the inherent characteristics of the whole-machine synchronous doffing strategy at the principle level have gradually revealed its limitations in addressing new challenges. Fundamentally, the whole-machine doffing mode forcibly binds the "doffing trigger condition" with the "physical position traversal," severing the dynamic connection between the doffing behavior and the actual spinning state. Further, this mode lacks intelligent scheduling capabilities in path planning; even if only a few spindles reach full capacity, the doffing trolley still needs to complete a full-stroke inspection, resulting in a large amount of ineffective movement and wasted time. Simultaneously, its positioning mechanism relies heavily on mechanical limits or coarse position encoder feedback, making it difficult to achieve sub-millimeter-level stopping accuracy at high speeds. When the trolley approaches the target spindle, if the deceleration response is lagging or the braking is over-aggressive, it is highly susceptible to interference with the main machine structure during mechanical actions such as flipping and gripping. This can lead to yarn bobbin jamming and positioning failure, or even damage to transmission components or complete machine shutdown. Correspondingly, to mitigate such risks, operators often need to intervene manually to reset or fine-tune parameters. This not only negates the efficiency gains brought by automation but also increases the probability of human error. In addition, due to the lack of overall optimization for multi-objective doffing tasks, when multiple spindles are full at the same time, the existing system cannot dynamically generate the shortest cruise path, resulting in longer doffing cycles, reduced equipment utilization, and the formation of an efficiency bottleneck.

[0006] Therefore, how to construct an intelligent doffing method that can dynamically trigger doffing commands based on the actual winding length of each spindle, and on this basis realize the optimal path planning and high-precision positioning collaborative control of the doffing trolley, so as to take into account yarn length consistency, work efficiency and mechanical safety, has become a key challenge and a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0007] This invention provides a fixed-length doffing intelligent positioning control method for rotor spinning doffing carriages, aiming to solve the problems of large yarn length deviation, redundant doffing paths, insufficient positioning accuracy, and high risk of mechanical interference caused by the synchronous doffing strategy of the whole machine in the prior art.

[0008] To achieve the above-mentioned objectives, this invention proposes a systematic method that dynamically triggers doffing commands based on the cumulative winding length of the spindle position, and combines optimal path planning with two-stage precise positioning and collaborative control. This ensures that the doffing operation is performed only on spindle positions that have reached the preset winding length, and completes high-precision docking and mechanical motion execution within the shortest stroke.

[0009] This invention provides a fixed-length doffing intelligent positioning control method for a rotor spinning doffing trolley, executed by a fixed-length doffing intelligent positioning control system. This system includes a host monitoring subsystem, a doffing control programmable logic controller, a doffing trolley, and sensing and execution mechanisms mounted on the trolley body. The method comprises the following steps:

[0010] First, the upper-level monitoring subsystem collects the pulse signals output by the rotary encoder of each spindle position in real time, accumulates and converts them into cumulative winding length. When the cumulative winding length of any spindle position reaches or exceeds the preset target fixed length threshold, a doffing trigger command containing the spindle position number is generated and sent to the doffing control programmable logic controller.

[0011] Secondly, after receiving one or more doffing trigger commands, the doffing control programmable logic controller uses a path optimization algorithm module to parse the physical position coordinates of the corresponding target spindle, and uses the current position of the doffing trolley as the starting node to dynamically construct the shortest non-loop cruising path covering all target spindles to be processed. In addition, unidirectional travel constraints are enforced during the path planning process. The path optimization algorithm module uses an improved nearest neighbor heuristic search strategy to dynamically construct the shortest non-loop cruising path covering all target spindles to be processed.

[0012] Furthermore, the doffing trolley moves sequentially to each target spindle position along the shortest non-loop cruising path. Before approaching each target spindle position, the doffing trolley achieves two-stage precise positioning and stopping through the interrupt response management unit. Specifically, the sensing mechanism installed on the trolley cooperates with the metal detection target fixed on the main frame to capture two interrupt signals, the rising edge and the falling edge, and trigger the first-stage deceleration and emergency braking commands respectively, thereby achieving two-stage precise positioning and stopping of the doffing trolley.

[0013] After docking, the actuator is activated to sequentially perform the actions of adsorbing, pushing out, removing the old yarn bobbin, and loading the new empty bobbin, thus completing the single-spindle doffing operation.

[0014] Finally, repeat the above movement, positioning, and single-spindle doffing operation process until all target spindles have completed doffing, and then return to the standby position.

[0015] Preferably, the conversion of the cumulative winding length of each spindle position is based on the following formula:

[0016]

[0017] In the formula, Let be the cumulative winding length of the i-th spindle. is the cumulative number of pulses at the i-th spindle position; p is the theoretical winding length corresponding to a single pulse, in mm; k is the system calibration coefficient, used to compensate for winding errors caused by yarn tension fluctuations and spindle wear.

[0018] Preferably, the improved nearest neighbor heuristic search strategy introduces a direction weight factor when calculating the distance between nodes. When the candidate target spindle is located behind the current doffing trolley position, its effective distance is magnified to the actual distance. This is multiplied by a factor of 1 to ensure that the generated cruise path satisfies the unidirectional travel constraint, where >10.

[0019] Preferably, the sensing mechanism is a proximity sensor array, wherein the proximity sensor array consists of multiple high-frequency response inductive proximity switches arranged linearly along the direction of travel of the vehicle. Each spindle position is provided with a metal detection target whose width covers the effective sensing range of the proximity sensor, and the sensing surface of the proximity sensor is parallel to the surface of the metal target with a vertical spacing of 3mm.

[0020] Preferably, the two-stage precise positioning and stopping specifically includes: when the first proximity sensor enters the sensing range of the metal target and outputs a rising edge signal, the servo drive motor switches to a low-speed operation mode, the speed drops to 0.05 m / s, and the output torque is limited to 30% of the rated value; when the sensor completely passes the trailing edge of the metal target and outputs a falling edge signal, the servo drive motor enters a zero-speed holding state and activates the electromagnetic brake device to implement mechanical locking.

[0021] Preferably, the actuator is a mechanical actuator arm assembly, which includes a vacuum suction cup mechanism, a push cylinder, a new bobbin supply slide, and a return spring mechanism. Its specific action sequence is as follows: the vacuum suction cup mechanism first descends to the top of the old bobbin to establish negative pressure suction; the push cylinder extends synchronously, pushing the old bobbin horizontally out of the spindle; then the vacuum suction cup mechanism rises and moves laterally out of the working area, and the old bobbin falls into the conveyor belt below; the new bobbin supply slide releases an empty bobbin under gravity, allowing it to slide into the spindle positioning slot; finally, the entire mechanical actuator arm returns to its initial position, ready to perform the doffing task at the next target spindle position.

[0022] The action sequence of the mechanical actuator assembly is controlled by a pneumatic solenoid valve group. The action interval of each cylinder is set to a fixed value of 200 ms. The negative pressure start and stop of the vacuum suction cup mechanism is strictly synchronized with the descent action. A photoelectric beam sensor is installed at the bottom of the new cylinder supply slide to detect the empty cylinder's position. If an obstruction signal is not detected within a preset time, the current doffing process is paused and an alarm is triggered.

[0023] Preferably, the doffing control programmable logic controller has a task queue buffer inside, which is used to temporarily store the doffing trigger instructions that arrive concurrently, and re-execute the path optimization process each time a new instruction set is received or the end spindle of the current path is completed, so as to include the newly added target spindle in the next cruise cycle.

[0024] Preferably, the upper-level monitoring subsystem communicates with the doffing control programmable logic controller via industrial Ethernet, using a timestamp synchronization mechanism, and the end-to-end transmission delay of the doffing trigger command does not exceed 10 ms.

[0025] Preferably, the servo drive motor is equipped with an encoder with a resolution of no less than 100,000 pulses per revolution. After being driven by a reducer, the system achieves a position control resolution of 10 micrometers in the track direction, with a repeatability accuracy better than ±0.1 mm.

[0026] Preferably, a laser rangefinder is added in front of the doffing trolley's travel path to scan the track area in real time; when an unexpected obstacle is detected, the path optimization algorithm temporarily marks the affected spindle as unreachable and recalculates the shortest cruising path among the remaining reachable spindles. The obstacle mark is automatically cleared after the task is completed.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] This invention fundamentally eliminates the problem of yarn bobbin length dispersion caused by differences in spinning rates between spindles by switching the doffing trigger condition from time-based cycle time to cumulative winding length and using the cumulative winding length as the actual winding length. By introducing a dynamic path optimization mechanism, the ineffective travel of the doffing trolley is significantly shortened, improving doffing efficiency per unit time. Through a two-stage interrupt-driven precise positioning technology, sub-millimeter-level stopping accuracy is achieved, effectively avoiding structural interference risks during mechanical flipping. The fully closed-loop automated workflow completely replaces manual intervention, reducing operational complexity and the probability of error. This method is applicable to all rotor spinning equipment equipped with track-type doffing trolleys, requiring no major modifications to the main structure; only an upgrade to the control system software and the addition of necessary sensing elements are needed to achieve high-quality, high-efficiency, and high-safety intelligent doffing operations. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the overall system architecture of the fixed-length doffing intelligent positioning control method for the rotor spinning doffing trolley of the present invention.

[0031] Figure 2 This is a schematic diagram of the path planning for the doffing trolley to travel along the track and perform multi-spindle doffing tasks in this invention.

[0032] Figure 3 This is a schematic diagram of the two-stage precise positioning process when the doffing trolley approaches the target spindle position in this invention.

[0033] Figure 4 This is a schematic diagram illustrating the action flow of the mechanical actuator assembly in this invention, which completes the removal of the old cylinder and the installation of the new cylinder at the target spindle position.

[0034] Figure 5 This is a block diagram showing the communication and data processing interaction between the upper-level monitoring subsystem and the doffing control programmable logic controller in this invention.

[0035] Figure 6 This is a schematic diagram illustrating the complete workflow of the fixed-length doffing intelligent positioning control method in this invention. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] like Figure 1-6As shown, this invention provides a fixed-length doffing intelligent positioning control method for a rotor spinning doffing trolley. The overall technical solution comprises a host monitoring subsystem, a doffing control programmable logic controller, the doffing trolley body, and its associated sensing and execution mechanisms, forming a closed-loop control system. This closed-loop control system collects real-time cumulative winding length data from each spindle position, dynamically generates doffing commands when the fixed-length condition is met, and combines a path optimization algorithm with a two-stage precise positioning mechanism to achieve high-precision docking and automated mechanical operation of the target spindle position.

[0039] In this application, the upper-level monitoring subsystem collects and records the cumulative winding length data of each spindle position in real time. This data comes from the pulse signal output by the rotary encoder installed on the spindle of each spindle position, and is converted into the actual winding length value after being accumulated by the high-speed counting module.

[0040] The supervisory control and data acquisition (SCADA) subsystem is deployed within the central control cabinet and runs on an industrial-grade embedded computer platform with a real-time Linux kernel operating system, possessing multi-threaded task scheduling capabilities. This system establishes communication connections with the rotary encoders on each spindle position via a high-speed fieldbus interface. Each spindle position is equipped with an incremental rotary encoder, whose output signal is a three-phase A / B / Z signal with a resolution of 2048 lines per revolution. After being quadrupled by a high-speed counting module, the effective pulse resolution reaches 8192 count units per revolution. The SCADA subsystem reads the cumulative pulse value of each spindle position at a fixed sampling period and converts the pulse value into the cumulative winding length based on preset yarn diameter parameters and spindle geometry parameters. The conversion formula is as follows:

[0041]

[0042] In the formula, Let be the cumulative winding length of the i-th spindle. is the cumulative number of pulses at the i-th spindle position; p is the theoretical winding length corresponding to a single pulse, in mm; k is the system calibration coefficient, used to compensate for winding errors caused by factors such as yarn tension fluctuations and spindle wear.

[0043] When the cumulative winding length of any spindle is greater than or equal to the preset target fixed length threshold At that time, the upper-level monitoring subsystem immediately generates a doffing trigger command containing the target spindle number i, and sends the command along with the target spindle number to the doffing control programmable logic controller via industrial Ethernet.

[0044] In this application, after receiving the set of doffing trigger instructions from the upper-level monitoring subsystem, the doffing control programmable logic controller (PLC) first parses the physical position coordinates of all target spindles to be processed. These coordinates are linearly encoded with millimeter-level resolution along the track direction, using the track start point as the reference origin. Subsequently, the PLC calls the built-in path optimization algorithm module, taking the current position of the doffing trolley as the starting node, and traverses all target spindles to be processed, dynamically constructing the shortest non-looping cruise path covering all target nodes. The path optimization process strictly follows the unidirectional travel constraint, meaning that the doffing trolley cannot run in reverse before completing a full doffing task cycle to avoid potential interference with the host structure. The final generated path sequence is arranged in execution order and serves as the basis for subsequent motion control instructions.

[0045] The doffing control programmable logic controller adopts a modular hardware architecture. The core processing unit is a 32-bit RISC architecture microprocessor, equipped with a dedicated motion control coprocessor, supporting multi-axis synchronous interpolation operations. Internally, it integrates a task queue buffer, a path optimization algorithm module, and an interrupt response management unit.

[0046] The task queue buffer adopts a circular FIFO structure with a maximum capacity of 64 doffing instructions, supporting both first-in-first-out (FIFO) and priority preemption scheduling modes. The task queue buffer temporarily stores multiple concurrently arriving doffing instructions and reorders them according to path optimization results, avoiding scheduling chaos caused by instruction backlog.

[0047] The path optimization algorithm module immediately initiates the path replanning process upon receiving a new set of doffing instructions. For example... Figure 2 As shown, this module uses the current physical position of the doffing trolley as the starting node, traverses the coordinate information of all target spindles to be processed, and constructs the shortest non-looping cruising path covering all target nodes. The path coordinates are linearly encoded with millimeter-level resolution along the track direction, using the track start point as the reference origin, and each spindle corresponds to a unique coordinate value. , where j={1,2,…,m}, and m is the total number of spindles to be processed.

[0048] The path optimization algorithm employs an improved nearest neighbor heuristic search strategy. Its core logic is as follows: starting from the current node, select the nearest unvisited target node as the next node to be visited, repeating this process until all target nodes are included in the path sequence. To ensure unidirectional movement constraints, the algorithm introduces a direction weight factor when calculating the distance between nodes. ( (Value greater than 10) When a candidate node is located behind the current node, its effective distance is magnified to half of the actual distance. This forces the path generator to prioritize the preceding nodes. Finally, the paths are executed in the order they appear in the final output sequence and used as inputs for the motion trajectory commands of the servo drive motors.

[0049] In this application, the doffing trolley body is equipped with a servo drive motor, a reducer, a drive wheel assembly, a driven wheel assembly, a proximity sensor array, and a mechanical actuator assembly. The servo drive motor is rigidly connected to the input end of the reducer via a coupling, and the output end of the reducer is fixed to the main shaft of the drive wheel assembly via a keyway, thereby transmitting rotational power to the track contact surface. The proximity sensor array consists of multiple high-frequency response inductive proximity switches, arranged linearly along the trolley's travel direction, with their sensing surfaces facing the track sidewall. Each spindle position corresponds to a metal detection target, which is fixed to the main frame, aligned with the spindle centerline, and its width covers the effective sensing range of the trolley's proximity sensor.

[0050] The doffing trolley is mounted on a parallel double-rail structure. The rails are made of hardened alloy steel with a precision-ground surface, ensuring a straightness error of no more than ±0.05 mm / m. The trolley chassis is cast from high-strength aluminum alloy, with multiple reinforcing ribs to enhance structural rigidity and a platform providing mounting surfaces for internal electronic modules. The servo drive motor is a permanent magnet synchronous motor with a rated power of 400 watts and a peak torque of 1.2 N·m. It is equipped with an absolute encoder with a resolution of 131,072 position pulses per revolution. The motor output shaft is connected to the input end of a planetary reducer via a rigid coupling, with a reduction ratio of 1:20. The reducer output end is fixed to the main shaft of the drive wheel set via a flat key. The drive wheel set consists of two polyurethane-coated drive wheels with a diameter of 80 mm, forming a rolling friction pair with the rail contact surface. The driven wheel set is located at the rear of the trolley and consists of two guide wheels with bearings, used to maintain the stability of the trolley's movement.

[0051] The proximity sensor array consists of four high-frequency response inductive proximity switches, model LJ12A3-4-Z / BX, with a response frequency of 2 kHz and a detection distance of 4 mm. The four sensors are arranged linearly along the trolley's travel direction, spaced 20 mm apart, with the sensing surfaces facing the track sidewall. Each spindle position has a corresponding metal detection target on the main frame, made of Q235 carbon steel, 3 mm thick and 30 mm wide, with its centerline strictly aligned with the spindle position's centerline. The target surface is sandblasted to enhance electromagnetic induction consistency. The proximity sensor is mounted parallel to the target's upper surface, with a vertical distance of 3 mm between them to ensure a steep signal transition and strong resistance to environmental interference.

[0052] In this application, the interrupt response management unit is used to capture two interrupt signals, the rising edge and the falling edge, by cooperating with the proximity sensor array installed on the trolley and the metal detection target fixed on the main frame when the doffing trolley moves sequentially to each target spindle along the shortest non-loop cruising path. These signals trigger the first-stage deceleration and emergency braking commands respectively, thereby realizing the two-stage precise positioning and stopping of the doffing trolley.

[0053] like Figure 3 As shown, when the doffing trolley moves along the track towards the first target spindle, the servo drive motor starts and accelerates to the cruising speed according to the preset S-shaped acceleration curve. The acceleration phase lasts for 0.8 seconds, and the cruising speed is set to 0.3 m / s. It enters the pre-deceleration zone 150 mm before the target spindle. At this time, the first proximity sensor enters the sensing range of the metal target, and the output signal jumps from low level (0 volts) to high level (24 volts). This rising edge signal is captured in real time by the high-speed interrupt input port of the doffing control programmable logic controller. The controller immediately triggers the first-stage deceleration command, and the servo drive motor switches to low-speed operation mode, reducing the speed to 0.05 m / s. Simultaneously, the output torque is limited to 30% of the rated value to suppress inertial overshoot. As the trolley continues forward, when the proximity sensor completely passes the trailing edge of the metal target, the output signal drops from high level to low level. This falling edge signal is again captured by the high-speed interrupt port, and the controller immediately issues an emergency braking command. The servo drive motor enters a zero-speed holding state and activates the electromagnetic brake device to implement mechanical locking. The electromagnetic brake is a normally closed DC brake with a rated voltage of 24 volts, a release time of less than 20 ms, and a locking torque of 5 N·m. This two-stage parking mechanism ensures that the trolley can accurately stop within ±0.5 mm of the target spindle centerline.

[0054] After precise positioning, the doffing control programmable logic controller (PLC) initiates the action sequence of the mechanical actuator assembly. This assembly, mounted on the top platform of the trolley, consists of a vacuum suction cup mechanism, a pusher cylinder, a new bobbin supply slide, and a return spring mechanism. All movements of the mechanical actuator assembly are controlled by a pneumatic solenoid valve group. The extension and retraction timing of each cylinder is precisely coordinated by the doffing control PLC through a digital output module. The action interval is set to a fixed value to eliminate timing drift caused by differences in air path response. The negative pressure source for the vacuum suction cup mechanism is provided by an independent vacuum generator, whose start / stop signal is strictly synchronized with the suction cup's descent to prevent empty suction or missed suction. A photoelectric sensor is installed at the bottom of the new bobbin supply slide to detect whether an empty bobbin is in place. If the detection fails, an alarm is triggered and the current doffing process is paused until manual intervention resumes.

[0055] In this embodiment, the vacuum suction cup mechanism consists of an aluminum alloy bracket, a silicone suction cup, and vacuum tubing. The suction cup has a diameter of 40mm and an internal pressure sensor for monitoring negative pressure. The push cylinder is a double-acting cylinder with a diameter of 32mm and a stroke of 80mm. A polyoxymethylene push block is installed at the end of the piston rod, and its surface is covered with a rubber buffer layer. The new cylinder supply slide is an inclined stainless steel channel with an inclination angle of 15°. A photoelectric beam sensor is installed at the bottom, with a distance of 25mm between the transmitter and receiver. The reset spring mechanism consists of a compression spring and a guide rod, with a preload of 50N, used to automatically reset the actuator arm to its initial position after the cylinder retracts.

[0056] like Figure 4 As shown, the mechanical actuator assembly executes its actions in the following sequence: First, the vacuum suction cup mechanism, driven by a vertical cylinder, descends to the top of the old yarn bobbin, with a descent stroke of 60 mm and a time of 0.5 s. Simultaneously, the vacuum generator starts, establishing a negative pressure of -60 kPa, and the adsorption confirmation signal is fed back to the controller by a pressure sensor. Next, the pusher cylinder extends, horizontally pushing the old yarn bobbin out of the spindle tray with a stroke of 70 mm and a time of 0.6 s. After detaching from the spindle tray, the old yarn bobbin falls onto the conveyor belt below under gravity. Then, the vacuum suction cup mechanism rises and moves laterally out of the working area, with an upward stroke of 60 mm and a lateral displacement of 100 mm, taking a total of 0.8 s. The new yarn bobbin supply chute releases an empty bobbin under gravity, allowing it to slide into the spindle tray positioning slot. A photoelectric sensor continuously monitors the empty bobbin's position; if no obstruction signal is detected within 1 s, it is determined that an empty bobbin is missing, and the controller immediately triggers an alarm and pauses the current yarn doffing process. Finally, the entire mechanical arm returns to its initial position under the action of the return spring, ready to perform the doffing task at the next target spindle position. All pneumatic actions are controlled by a three-position five-way solenoid valve group with a valve response time of 15 ms. The interval between each action is set to a fixed value of 200 ms to eliminate timing drift caused by differences in pneumatic response.

[0057] After completing all mechanical actions at the current target spindle, the doffing control programmable logic controller (PLC) drives the doffing trolley to move to the next target spindle according to the optimized path sequence, repeating the aforementioned proximity sensing, two-stage stopping, and mechanical action process until all spindles have completed the doffing operation. After the task is completed, the doffing trolley automatically returns to the standby position at the end of the track. This position is equipped with a mechanical limit stop and a zero-point calibration sensor to periodically correct the trolley's absolute position. During the return process, the trolley runs at a constant speed of 0.25 m / s. Upon reaching the standby position, it enters a low-power sleep state, the servo driver shuts down its output, retaining only the communication module and interrupt listening function, awaiting the next doffing command.

[0058] The upper-level monitoring subsystem and the doffing control programmable logic controller (PLC) exchange data in real time via industrial Ethernet. The physical layer uses Cat6A shielded twisted-pair cable with a transmission rate of 100 Mbps. The communication protocol is custom-developed based on the TCP / IP stack and employs a timestamp synchronization mechanism. Each doffing trigger instruction packet includes instruction type, spindle number, timestamp, and checksum fields. Upon receiving the instruction, the controller immediately sends back an acknowledgment frame. The measured round-trip communication delay does not exceed 8 ms, meeting real-time requirements. The task queue buffer uses a double-buffering mechanism. Write operations are completed by the communication interrupt service routine, while read operations are executed cyclically by the main control, avoiding data contention.

[0059] In this application, the proximity sensor is installed parallel to the surface of the metal target, with a distance of three millimeters between them to ensure the steepness of the signal transition edge and anti-interference capability. The encoder feedback resolution of the servo drive motor is no less than 100,000 pulses per revolution, which, combined with the gearbox transmission ratio, achieves a position control resolution of 10 micrometers in the track direction.

[0060] In this application, the proximity sensor signal processing circuit is integrated into the controller I / O expansion module, using a Schmitt trigger for shaping with a hysteresis voltage of 2 volts to effectively filter out signal jitter caused by mechanical vibration. The servo drive motor's position closed-loop control adopts a three-loop control structure: an outer position loop, a middle velocity loop, and an inner current loop. The position loop sampling period is 1 ms, the proportional gain Kp is set to 1200, and the integral time Ti is 200 ms; the velocity loop sampling period is 0.5 ms, and the proportional gain is 80; the current loop sampling period is 0.1 ms, and the bandwidth is 2 kHz. Combined with the reducer transmission ratio and wheel diameter parameters, the system achieves a position control resolution of 10 micrometers in the track direction, with a repeatability better than ±0.1 mm.

[0061] The path optimization algorithm module recalculates the globally optimal path each time it receives a new set of doffing instructions, without relying on historical path memory, thus adapting to dynamically changing full-bore distributions. If a new spindle reaches a full-bore state during the doffing trolley's execution, i.e., the cumulative winding length of that spindle is greater than or equal to the preset target fixed-length threshold... Upon receiving the request, the supervisory control subsystem immediately adds it to the processing queue and sets a high-priority flag. After completing the last spindle position of the current path, the doffing control programmable logic controller checks the queue status. If a new high-priority task is added, the path optimization process is immediately triggered, incorporating the new target into the next cycle. This mechanism ensures that the system's response delay to dynamic full-bore events does not exceed one complete doffing cycle.

[0062] All pneumatic components of the mechanical actuator assembly are connected to a centralized air supply unit, with a stable operating pressure of 0.55 MPa. The pipeline is equipped with an oil-water separator and a pressure-reducing filter. The vacuum generator is a Venturi type, consuming 15 liters per minute of air, with a response time of less than 100 ms. All digital output signals drive the solenoid valve coils after optocoupler isolation, with an isolation voltage of 2500 volts, effectively preventing malfunctions caused by electromagnetic interference.

[0063] To verify the actual effect of the technical solution of the present invention, the following embodiments and comparative tests were conducted.

[0064] In one specific embodiment, a rotor spinning machine with 480 spindles is selected and equipped with the fixed-length doffing intelligent positioning control system described in this invention. A target fixed-length threshold is set. The length is 12,000 m. The upper-level monitoring subsystem collects the winding length of each spindle at a period of 100 ms, and the doffing control programmable logic controller checks the task queue every 500 ms. During the test, a total of 1,000 doffing operations were recorded, and the actual winding length of the yarn bobbin, the travel of the doffing carriage, the positioning deviation, and the task completion time were statistically analyzed.

[0065] As a comparison, the same model of equipment, employing a traditional whole-machine synchronous doffing strategy, was operated under the same spinning process conditions. This equipment triggers doffing across the entire machine at a fixed time interval (every 30 minutes), without distinguishing the actual winding state of each spindle.

[0066] The test results are shown in the table below:

[0067]

[0068] Experimental data show that the yarn bobbin length dispersion was significantly reduced in the embodiment, the doffing trolley travel was shortened by approximately 59%, the positioning accuracy was improved by an order of magnitude, and the single-spindle doffing efficiency was increased by 39%, without any mechanical interference events. These results fully demonstrate the technical advantages of this invention in fixed-length control, path optimization, precise positioning, and system reliability.

[0069] Furthermore, in a continuous 72-hour stability test, the system of this invention processed a total of 14,280 doffing commands, achieving a 100% task completion rate, a 0% communication packet loss rate, no out-of-tolerance alarms from the servo system, and a 99.98% success rate for the mechanical actuator (two failures were due to empty cylinder jamming, which were resolved after manual reset). The system's mean time between failures (MTBF) exceeds 500 hours, meeting the requirements for long-term stable operation in industrial settings.

[0070] Furthermore, the path optimization algorithm module can be further integrated with dynamic obstacle avoidance functionality. When temporary obstacles (such as maintenance tools, foreign objects, etc.) exist on the track, an additionally installed laser rangefinder sensor scans the area 1 m ahead in real time. If an unexpected reflection signal is detected, the affected spindle section is temporarily excluded from the path planning, and a detour sub-path is generated. This function is enabled through software configuration without requiring changes to the hardware structure.

[0071] Specifically, the laser rangefinder sensor is model LMS111, with a scanning frequency of 25 Hz, a ranging range of 0.15 to 20 m, and an accuracy of ±20 mm. Its data stream is connected to the Ethernet extension module of the doffing control programmable logic controller (PLC). After filtering and clustering, a list of obstacle locations is generated. When constructing the node graph, the path optimization algorithm marks spindles within the obstacle coverage area as "unreachable" and recalculates the shortest path among the remaining reachable nodes. After the task is completed, the system automatically clears the obstacle markings and restores service capability to the entire area.

[0072] In summary, this invention directly links the doffing trigger mechanism to the actual winding length, combining dynamic path optimization, two-stage interruption-driven precise positioning, and a fully closed-loop mechanical execution process to construct a highly efficient, precise, and reliable intelligent control system for rotor spinning doffing. This solution only requires the addition of a rotary encoder, proximity sensor, metal target, and upgraded control software to existing equipment to achieve high-quality fixed-length doffing operations, demonstrating significant engineering application value and promising prospects for widespread adoption.

[0073] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for intelligent positioning control of fixed-length doffing in a rotor spinning doffing carriage, characterized in that, This is executed through a fixed-length doffing intelligent positioning control system, which includes a host monitoring subsystem, a doffing control programmable logic controller, a doffing trolley, and sensing and execution mechanisms mounted on the doffing trolley body. The process includes the following steps: First, the upper-level monitoring subsystem collects the pulse signals output by the rotary encoder of each spindle position in real time, accumulates and converts them into cumulative winding length. When the cumulative winding length of any spindle position reaches or exceeds the preset target fixed length threshold, a doffing trigger command containing the spindle position number is generated and sent to the doffing control programmable logic controller. Secondly, after receiving one or more doffing trigger commands, the doffing control programmable logic controller uses a path optimization algorithm module to parse the physical position coordinates of the corresponding target spindle, and uses the current position of the doffing trolley as the starting node to dynamically construct the shortest non-loop cruising path covering all target spindles to be processed. In addition, unidirectional travel constraints are enforced during the path planning process. The path optimization algorithm module uses an improved nearest neighbor heuristic search strategy to dynamically construct the shortest non-loop cruising path covering all target spindles to be processed. Furthermore, the doffing trolley moves sequentially to each target spindle position along the shortest non-loop cruising path. Before approaching each target spindle position, the doffing trolley achieves two-stage precise positioning and stopping through the interrupt response management unit. Specifically, the sensing mechanism installed on the trolley cooperates with the metal detection target fixed on the main frame to capture two interrupt signals, the rising edge and the falling edge, and trigger the first-stage deceleration and emergency braking commands respectively, thereby achieving two-stage precise positioning and stopping of the doffing trolley. After docking, the actuator is activated to sequentially perform the actions of adsorbing, pushing out, removing the old yarn bobbin, and loading the new empty bobbin, thus completing the single-spindle doffing operation. Finally, repeat the above movement, positioning, and single-spindle doffing operation process until all target spindles have completed doffing, and then return to the standby position.

2. The intelligent positioning control method for fixed-length doffing of a rotor spinning doffing trolley according to claim 1, characterized in that, The conversion of the cumulative winding length of each spindle position is based on the following formula: In the formula, Let be the cumulative winding length of the i-th spindle. is the cumulative number of pulses at the i-th spindle position; p is the theoretical winding length corresponding to a single pulse, in mm; k is the system calibration coefficient, used to compensate for winding errors caused by yarn tension fluctuations and spindle wear.

3. The intelligent positioning control method for fixed-length doffing of a rotor spinning doffing trolley according to claim 1, characterized in that, The improved nearest neighbor heuristic search strategy introduces a direction weight factor when calculating the distance between nodes. When the candidate target spindle is located behind the current doffing trolley position, its effective distance is magnified to the actual distance. This is multiplied by a factor of 1 to ensure that the generated cruise path satisfies the unidirectional travel constraint, where >

10.

4. The intelligent positioning control method for fixed-length doffing of a rotor spinning doffing trolley according to claim 1, characterized in that, The sensing mechanism is a proximity sensor array, which consists of multiple high-frequency response inductive proximity switches arranged linearly along the direction of travel of the vehicle. Each spindle position is equipped with a metal detection target whose width covers the effective sensing range of the proximity sensor, and the sensing surface of the proximity sensor is parallel to the surface of the metal target with a vertical spacing of 3 mm.

5. The intelligent positioning control method for fixed-length doffing of a rotor spinning doffing trolley according to claim 4, characterized in that, The two-stage precise positioning and stopping specifically includes: when the first proximity sensor enters the sensing range of the metal target and outputs a rising edge signal, the servo drive motor switches to a low-speed operation mode, the speed drops to 0.05 m / s, and the output torque is limited to 30% of the rated value; when the sensor completely passes the trailing edge of the metal target and outputs a falling edge signal, the servo drive motor enters a zero-speed holding state and activates the electromagnetic brake device to implement mechanical locking.

6. The intelligent positioning control method for fixed-length doffing of a rotor spinning doffing trolley according to claim 1, characterized in that, The actuator is a mechanical actuator arm assembly, which includes a vacuum suction cup mechanism, a push cylinder, a new bobbin supply slide, and a return spring mechanism. Its specific action sequence is as follows: the vacuum suction cup mechanism first descends to the top of the old bobbin, establishing negative pressure suction; the push cylinder extends simultaneously, horizontally pushing the old bobbin out of the spindle tray; subsequently, the vacuum suction cup mechanism rises and moves laterally out of the working area, and the old bobbin falls into the conveyor belt below; the new bobbin supply slide releases an empty bobbin under gravity, allowing it to slide into the spindle tray positioning slot; finally, the entire mechanical actuator arm returns to its initial position, ready to perform the doffing task at the next target spindle position. The action sequence of the mechanical actuator assembly is controlled by a pneumatic solenoid valve group. The action interval of each cylinder is set to a fixed value of 200 ms. The negative pressure start and stop of the vacuum suction cup mechanism is strictly synchronized with the descent action. A photoelectric beam sensor is installed at the bottom of the new cylinder supply slide to detect the empty cylinder's position. If an obstruction signal is not detected within a preset time, the current doffing process is paused and an alarm is triggered.

7. The intelligent positioning control method for fixed-length doffing of a rotor spinning doffing trolley according to claim 1, characterized in that, The doffing control programmable logic controller has an internal task queue buffer to temporarily store concurrent doffing trigger instructions. After receiving a new set of instructions or completing the last spindle of the current path, the path optimization process is re-executed to include the new target spindle in the next cruise cycle.

8. The intelligent positioning control method for fixed-length doffing of a rotor spinning doffing trolley according to claim 1, characterized in that, The upper-level monitoring subsystem communicates with the doffing control programmable logic controller via industrial Ethernet and adopts a timestamp synchronization mechanism, ensuring that the end-to-end transmission delay of the doffing trigger command does not exceed 10 ms.

9. The intelligent positioning control method for fixed-length doffing of a rotor spinning doffing trolley according to claim 1, characterized in that, The servo drive motor is equipped with an encoder with a resolution of no less than 100,000 pulses per revolution. After being driven by a reducer, the system achieves a position control resolution of 10 micrometers in the track direction, with a repeatability accuracy better than ±0.1 mm.

10. The intelligent positioning control method for fixed-length doffing of a rotor spinning doffing trolley according to claim 1, characterized in that, A laser rangefinder is added in front of the doffing trolley to scan the track area in real time. When an unexpected obstacle is detected, the path optimization algorithm temporarily marks the affected spindle as unreachable and recalculates the shortest cruising path among the remaining reachable spindles. The obstacle mark is automatically cleared after the task is completed.

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