Method for time slice synchronous control of RS485 bus of multi-electric motor clamping jaw

Abstract

The present application relates to the technical field of synchronous control of multiple electric clamping jaws, and particularly relates to an RS485 bus time slice synchronous control method for multiple electric clamping jaws, which comprises S1, whole network clock synchronization calibration: the master station periodically broadcasts a synchronization frame carrying a reference timestamp to the RS485 bus, all electric clamping jaw slave stations listen to and analyze the synchronization frame in real time, calibrate the local clock according to the reference time information, unify the whole network time sequence reference, and make the clock synchronization accuracy of the master station and all slave stations reach ±100us; the scheme introduces a time division multiple access scheduling mechanism into the traditional RS485 bus control, replaces the unstable software polling conflict avoidance mode, realizes bus channel time-sharing isolation through the time sequence rules of exclusive sending in the dedicated time slice and silent listening in the non-dedicated time slice, and the bus unique device actively sends at any time, thereby solving the signal conflict, data packet loss and communication lag caused by the concurrent transmission of multiple slave stations from the bottom layer, and greatly improving the stability and certainty of bus communication.

Description

Technical Field

[0001] This invention relates to the field of multi-electric gripper synchronization control technology, and more particularly to an RS485 bus time-slice synchronization control method for multi-electric grippers. Background Technology

[0002] In industries such as non-standard automation, 3C electronics assembly, precision hardware processing, and lithium battery automation, the collaborative operation of multiple electric grippers in clusters is the core process for achieving batch workpiece gripping, positioning, and assembly. Currently, the vast majority of small and medium-sized automated equipment and existing equipment retrofits use RS485 serial buses to complete the network control of multiple electric grippers. RS485 bus has become the mainstream communication solution for low-cost networking of multiple grippers due to its advantages of simple wiring, strong differential anti-interference capability, low hardware cost, strong versatility, and simple protocol adaptation.

[0003] Existing RS485 bus multi-electric gripper control systems all employ a master-station polling response mechanism for data exchange and command control. The master station sends query and control commands to each electric gripper sequentially according to a preset sequence of slave device addresses, with only one slave station allowed to respond and upload data at any given time. This traditional control mode has many inherent technical defects, severely limiting the accuracy of multi-gripper collaborative operations: 1. The RS485 bus is an asynchronous clockless bus. All electric gripper slaves on the bus use local independent timers for timing. There is no global unified clock reference. The crystal oscillators of each device have inherent frequency deviation and temperature drift. Over long-term operation, the clock deviation continues to accumulate, resulting in disordered timing of multiple gripper actions. 2. The traditional polling mode is a passive conflict avoidance mechanism at the software level, without hardware timing constraints. Once abnormal conditions such as inconsistent power-on timing of slave stations, command packet loss, timeout retransmission, and software scheduling jitter occur, multiple slave stations are very likely to send data at the same time, causing bus signal superposition conflicts, frame check errors, data packet loss, bus lag, or even the entire network communication blockage. 3. Traditional multi-gripper synchronous operation relies on delay compensation of the master station software to achieve pseudo-synchronization. Affected by communication delay and equipment response differences, the synchronization error usually reaches the millisecond level, which cannot meet the requirements of precision assembly process for microsecond-level synchronization accuracy.

[0004] To address this, a time-slice synchronization control method for multiple electric grippers via RS485 bus is proposed. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a multi-electric gripper RS485 bus time-slice synchronization control method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for time-slice synchronization control of RS485 bus for multi-electric grippers includes S1, full-network clock synchronization calibration: the master station periodically broadcasts a synchronization frame carrying a reference timestamp to the RS485 bus, all electric gripper slave stations listen to and parse the synchronization frame in real time, calibrate the local clock according to the reference time information, unify the timing reference of the entire network, and make the clock synchronization accuracy between the master station and all slave stations reach ±100μs; S2. Time Slice Division and Dedicated Allocation: The master station sets 50ms as the global fixed control cycle of the system, and divides the 50ms global control cycle evenly into 10 independent non-overlapping time slices with a duration of 5ms. Each time slice is configured with a unique time slice ID. The master station scans the online devices on the bus and assigns a unique dedicated time slice ID to each electric gripper slave station, establishing a one-to-one binding relationship between the slave station device and the time slice. S3, time-division conflict-free bus communication: Each electric gripper slave station actively sends operating condition data to the RS485 bus only within its own dedicated 5ms time slot; during non-dedicated time slot periods, all slave stations disable data transmission function and only maintain bus listening and command receiving status, eliminating multi-device bus data conflicts through time slot isolation. S4. Multi-gripper synchronous action execution: When multi-gripper coordinated synchronous operation is required, the master station sends a multicast command containing action parameters to the RS485 bus; each electric gripper slave station receives and buffers the multicast command, does not execute the action immediately, and waits for the next global synchronization point to arrive before all target slave stations synchronously execute the clamping or releasing servo action.

[0007] Preferably, the method adopts a time-division multiple access (TDMA) communication scheduling mode, which completely replaces the traditional RS485 software polling control mode. It does not require replacing expensive real-time bus hardware such as EtherCAT or Profinet, and realizes hard real-time synchronous control of multiple electric grippers based on the native RS485 hardware architecture.

[0008] Preferably, all electric gripper slave stations in the entire network strictly follow the time-slot communication rules, actively uploading data only in a dedicated time slot, and silently listening at the rest of the time, thus completely eliminating bus concurrency conflicts, data packet loss and communication lag issues from the timing layer.

[0009] Preferably, the multi-gripper synchronous operation adopts a multicast instruction caching and globally unified synchronization point triggering execution mechanism, abandoning the software delay pseudo-synchronization method, eliminating the timing deviation of multi-device instruction reception and action response, and realizing high-precision synchronous collaborative assembly and group control gripping operation of multi-gripper.

[0010] Preferably, the master station forms a closed-loop clock calibration mechanism by periodically broadcasting synchronization frames to continuously compensate for clock drift caused by temperature drift and frequency offset of crystal oscillators of each slave station, ensuring that the clock synchronization accuracy of the entire network is stably maintained at ±100μs during long-term operation of the system.

[0011] The control structure of the RS485 bus time-slice synchronization control method for multiple electric grippers is characterized by including a master station controller and several electric gripper slave stations, wherein the master station controller and each electric gripper slave station are connected to the same RS485 bus and form a single master-multiple slave network structure.

[0012] The beneficial effects of this invention are: This invention introduces a time-division multiple access (TDMA) scheduling mechanism into the traditional RS485 bus control, replacing the unstable software polling collision avoidance mode. By using a timing rule of dedicated time slices for exclusive transmission and non-dedicated time slices for silent listening, it achieves time-division isolation of the bus channel. At any given time, only one device on the bus actively transmits data, solving the problems of signal conflicts, data packet loss, and communication lag caused by concurrent transmission from multiple slave stations from the underlying layer, and significantly improving the stability and determinism of bus communication.

[0013] This invention unifies the timing reference of all devices in the network through a periodic synchronization frame closed-loop calibration mechanism, effectively compensating for crystal oscillator frequency offset and temperature drift of each device, compressing the millisecond-level synchronization error of traditional solutions to ±100μs, and completely solving the problems of independent timing and asynchronous actions of distributed grippers. It meets the high process requirements of precision assembly and accurate gripping, and does not require the replacement of expensive industrial real-time bus hardware such as EtherCAT and Profinet, nor does it require the replacement of main controller, driver, and communication cables. It fully reuses the existing RS485 bus networking architecture and electric gripper equipment, and achieves performance upgrades only through algorithm and timing logic optimization, greatly reducing the equipment upgrade and project implementation costs of multi-gripper high-precision group control.

[0014] It adopts a hard real-time architecture with a fixed 50ms global cycle and a 5ms basic time slot. The control cycle is fixed and the timing logic is controllable. The real-time performance and stability of the system are not affected by the number of mounted devices, and it is suitable for control scenarios with a large number of gripper clusters.

[0015] It adopts a synchronization mechanism of instruction cache standby + global synchronization point unified triggering, abandons the traditional software delay pseudo-synchronization method, eliminates the timing deviation caused by instruction time-sharing and equipment response differences, realizes zero-delay synchronous action of multi-gripper, and is suitable for core operation scenarios of multi-gripper collaborative assembly and group control grasping. Attached Figure Description

[0016] Figure 1 This is a structural block diagram of the RS485 bus time-slice synchronization control method for multi-electric grippers proposed in this invention; Detailed Implementation

[0017] 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.

[0018] Example: Refer to Figure 1 A time-slice synchronization control method for RS485 bus with multiple electric grippers includes S1, full-network clock synchronization calibration: The master station broadcasts a custom global synchronization frame to the RS485 bus at a fixed period. The synchronization frame carries the master station's high-precision reference timestamp and synchronization verification information, providing a unified timing reference for all slave stations in the network. All electric gripper slave stations on the bus maintain a bus listening state throughout the process, capturing the synchronization frame signal in real time and quickly parsing the reference time information. Combined with the local timer, clock deviation calibration is completed to correct the deviation between the local clock and the master station's reference clock, and to compensate for timing errors caused by crystal oscillator temperature drift and operational drift. After periodic closed-loop calibration, the clock synchronization accuracy of the master station and all slave stations in the network is stably controlled within ±100μs, eliminating the timing disorder problem caused by independent timing of distributed devices. S2. Time Slice Division and Dedicated Allocation: The master station sets 50ms as the global fixed control cycle of the system, and divides the 50ms global control cycle evenly into 10 independent non-overlapping time slices with a duration of 5ms. Each time slice is configured with a unique time slice ID. The master station scans the online devices on the bus and assigns a unique dedicated time slice ID to each electric gripper slave station, establishing a one-to-one binding relationship between the slave station device and the time slice. S3. Time-Division Conflict-Free Bus Communication: Within each 50ms global control cycle, each electric gripper slave station determines its current system timing position in real time using a local timer, strictly adhering to time-slot communication rules: It only enables RS485 data transmission within its own dedicated 5ms time slot window, actively uploading real-time gripper opening / closing status, gripping force data, servo operating parameters, fault status, limit signals, and other operating condition information to the bus; during all time slots not belonging to its own station, all electric gripper slave stations forcibly close the RS485 transmission path, permanently prohibiting them from actively sending any data to the bus, only continuously listening to and receiving control commands and configuration parameters issued by the master station. Through dedicated channel isolation at the timing level, it ensures that only a single device actively transmits data on the bus at any given time, completely eliminating bus conflicts, data loss, and communication disorder caused by concurrent transmission from multiple devices. S4. Synchronous Execution of Multiple Grippers: For collaborative operation scenarios requiring synchronized clamping, releasing, and resetting of multiple grippers, the master station employs a control logic of batch multicast command distribution and unified triggering at a global synchronization point. The master station sends multicast control commands to the entire RS485 bus network. These commands include action parameters such as clamping force, opening / closing displacement, and running speed. All target electric gripper slave stations receiving the multicast commands immediately parse and cache the action parameters, marking them as pending execution status, but do not immediately trigger servo actions to avoid action deviations caused by timing differences in command reception. All slave stations awaiting execution continuously monitor the bus synchronization frame signal, waiting for the arrival of the next unified global synchronization reference point. At the instant the master station broadcasts the synchronization frame and the global timing reference is refreshed, all cached electric gripper slave stations synchronously trigger servo actions, simultaneously completing the clamping or releasing operation, achieving high-precision synchronous collaborative control of multiple grippers.

[0019] Specifically, the method adopts a time-division multiple access (TDMA) communication scheduling mode, which completely replaces the traditional RS485 software polling control mode. It does not require replacing expensive real-time bus hardware such as EtherCAT or Profinet, and realizes hard real-time synchronous control of multiple electric grippers based on the native RS485 hardware architecture.

[0020] Furthermore, all electric gripper slave stations across the network strictly adhere to time-slot communication rules, actively uploading data only during dedicated time slices and silently listening at the rest of the time, thus completely eliminating bus concurrency conflicts, data packet loss, and communication lag issues from the underlying timing layer.

[0021] Furthermore, the multi-gripper synchronous operation adopts a multicast command caching and globally unified synchronization point triggering execution mechanism, abandoning the software delay pseudo-synchronization method, eliminating the timing deviation of multi-device command reception and action response, and realizing high-precision synchronous collaborative assembly and group control gripping operations of multi-grippers.

[0022] Finally, the master station forms a closed-loop clock calibration mechanism by periodically broadcasting synchronization frames to continuously compensate for clock drift caused by temperature drift and frequency offset of crystal oscillators of each slave station, ensuring that the clock synchronization accuracy of the entire network is stably maintained at ±100μs during long-term operation of the system.

[0023] In this embodiment, the control structure of the RS485 bus time-slice synchronization control method for multiple electric grippers is characterized by including a master station controller and several electric gripper slave stations. The master station controller and each electric gripper slave station are connected to the same RS485 bus and form a single master-multiple slave network structure.

[0024] The test control system built in this embodiment includes one industrial master station controller and eight electric gripper slave stations of the same specification. All devices are connected in parallel to the same RS485 differential bus via twisted pair cables. The bus baud rate is configured as a conventional industrial 115200bps. No hardware replacement or line modification was carried out throughout the process, and the traditional RS485 networking hardware architecture was completely adopted.

[0025] After the system powers on and initializes, the master station automatically scans the online devices on the bus and accurately identifies 8 valid online electric gripper slave stations. The master station initiates the timing scheduling mechanism, evenly dividing the preset 50ms fixed global control cycle into 10 non-overlapping, equally long 5ms basic time slices, and assigning unique time slice IDs from ID0 to ID9 in sequence. The master station assigns a dedicated time slot ID to each of the 8 electric gripper slave stations, establishes a binding relationship between the device and the time slot, and issues and solidifies the binding. The remaining idle time slots can be used for master station parameter inspection and fault diagnosis.

[0026] During normal system operation, the master station broadcasts a synchronization frame with a high-precision timestamp to the bus at the beginning of each 50ms global cycle. All electric gripper slave stations listen to and parse the synchronization frame data in real time, compare it with local timing information to complete clock calibration, correct timing deviations, continuously suppress clock drift, and keep the clock synchronization error of the entire network stable within ±100μs, ensuring that the timing of all devices is completely consistent.

[0027] During the data communication phase, each electric gripper slave station strictly adheres to the time-slot rule: it activates its transmission function only within its corresponding 5ms dedicated time slot, actively uploading full-scale operating data such as gripper opening and closing positions, real-time clamping force, motor operating current, fault codes, and limit switch status; during all other time slots, the slave station completely shuts down its transmission channel, maintaining only a bus listening state to receive control commands and parameter configurations from the master station in real time. The entire communication process is free of any bus conflicts and data packet loss, with stable and highly deterministic communication timing.

[0028] When it is necessary to perform synchronous gripping and assembly operations with 8 grippers, the master station sends a multicast synchronous gripping command to the entire network, uniformly configuring process parameters such as gripping force, opening and closing stroke, and action speed. All electric grippers receive and cache the command parameters synchronously at the slave station, remain in standby state, and do not perform any actions. When the next round of master station synchronous frame broadcast and the global synchronous reference point of the entire network arrives, the 8 electric grippers synchronously trigger servo gripping actions. The action synchronization error does not exceed ±100μs, and the action consistency is extremely high, perfectly meeting the requirements of precision collaborative assembly process.

[0029] After long-term continuous operation testing, this control system showed no clock drift accumulation, no bus blockage, and no communication abnormalities. The stability and consistency of multi-gripper synchronous operation were excellent, and it can be adapted to continuous industrial automation operation conditions for a long time.

[0030] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0031] All standard parts used in this invention can be purchased from the market, and irregular parts can be customized according to the description and drawings. The specific connection methods of each part adopt conventional methods such as bolts, rivets, and welding that are mature in the prior art. The machinery, parts and equipment adopt conventional models in the prior art, and the circuit connection adopts conventional connection methods in the prior art, which will not be described in detail here.

[0032] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for RS485 bus time-slice synchronization control of multiple electric grippers, characterized in that, include: S1. Network-wide clock synchronization calibration: The master station periodically broadcasts a synchronization frame carrying a reference timestamp to the RS485 bus. All electric gripper slave stations listen to and parse the synchronization frame in real time, calibrate their local clocks according to the reference time information, unify the network-wide timing reference, and make the clock synchronization accuracy between the master station and all slave stations reach ±100μs. S2. Time Slice Division and Dedicated Allocation: The master station sets 50ms as the global fixed control cycle of the system, and divides the 50ms global control cycle evenly into 10 independent non-overlapping time slices with a duration of 5ms. Each time slice is configured with a unique time slice ID. The master station scans the online devices on the bus and assigns a unique dedicated time slice ID to each electric gripper slave station, establishing a one-to-one binding relationship between the slave station device and the time slice. S3, time-division conflict-free bus communication: Each electric gripper slave station actively sends operating condition data to the RS485 bus only within its own dedicated 5ms time slot; during non-dedicated time slot periods, all slave stations disable data transmission function and only maintain bus listening and command receiving status, eliminating multi-device bus data conflicts through time slot isolation. S4. Multi-gripper synchronous action execution: When multi-gripper coordinated synchronous operation is required, the master station sends a multicast command containing action parameters to the RS485 bus; each electric gripper slave station receives and buffers the multicast command, does not execute the action immediately, and waits for the next global synchronization point to arrive before all target slave stations synchronously execute the clamping or releasing servo action.

2. The RS485 bus time-slice synchronization control method for multiple electric grippers according to claim 1, characterized in that, The control method adopts the time division multiple access (TDMA) communication scheduling mode, which completely replaces the traditional RS485 software polling control mode. It does not require replacing the expensive real-time bus hardware of EtherCAT or Profinet, and realizes hard real-time synchronous control of multiple electric grippers based on the native RS485 hardware architecture.

3. The RS485 bus time-slice synchronization control method for multiple electric grippers according to claim 2, characterized in that, All electric gripper slave stations in the network strictly follow the time-slot communication rules, actively uploading data only in their designated time slots, and silently listening at the rest of the time, thus completely eliminating bus concurrency conflicts, data packet loss, and communication lag issues from the underlying timing layer.

4. The RS485 bus time-slice synchronization control method for multiple electric grippers according to claim 3, characterized in that, The multi-gripper synchronous operation adopts a multicast command caching and globally unified synchronization point triggering execution mechanism, abandoning the software delay pseudo-synchronization method, eliminating the timing deviation between multi-device command reception and action response, and realizing high-precision synchronous collaborative assembly and group control gripping operation of multi-gripper.

5. The RS485 bus time-slice synchronization control method for multiple electric grippers according to claim 4, characterized in that, The master station forms a closed-loop clock calibration mechanism by periodically broadcasting synchronization frames to continuously compensate for clock drift caused by temperature drift and frequency offset of crystal oscillators of each slave station, ensuring that the clock synchronization accuracy of the entire network is stably maintained at ±100μs during long-term operation of the system.

6. A control structure for an RS485 bus time-slice synchronization control method for multiple electric grippers according to any one of claims 1-5, characterized in that, It includes a master station controller and several electric gripper slave stations. The master station controller and each electric gripper slave station are connected to the same RS485 bus and form a single master and multiple slave network structure.

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