Electric gripper group conflict adaptive backoff control method based on RS485 bus

Abstract

The present application relates to the technical field of electric clamping jaw, and particularly relates to a conflict adaptive backoff control method of electric clamping jaw group based on RS485 bus, a plurality of electric clamping jaws are connected in parallel to the same RS485 differential bus as multiple master nodes, a communication control unit is built in each electric clamping jaw to execute an improved CSMA / CD protocol, and the improved CSMA / CD protocol comprises the following steps: S1: bus carrier sensing pre-judgment; S2: real-time conflict detection in a transmission process; S3: dynamic backoff time length calculation based on a priority parameter; S4: continuous conflict binary exponential backoff expansion; S5: high-priority frame pre-emptive sending scheduling; and S6: transmission completion conflict count resetting. The present application realizes conflict suppression through software protocol improvement, uses standard general RS485 transceiver chips, does not need to replace CAN and Ethernet hardware, does not increase the cost of wiring and isolation circuit, and is suitable for large-batch low-cost electric clamping jaw production line networking.

Description

Technical Field

[0001] This invention relates to the field of electric gripper technology, and in particular to a conflict adaptive backoff control method for electric gripper groups based on RS485 bus. Background Technology

[0002] RS485 bus, with its advantages of simple wiring, low hardware cost, and long transmission distance, is widely used in the networking communication of lower-level devices such as electric grippers, cylinders, and servo actuators in automated production lines. The standard RS485 physical layer only supports half-duplex differential transmission, and lacks native conflict detection and bus arbitration mechanisms at the hardware level, theoretically supporting a maximum of 32 nodes connected to the bus. When multiple electric grippers act as multiple master nodes actively reporting their gripping status and receiving synchronous grasping commands, multiple nodes simultaneously driving the bus can easily lead to bus conflict faults such as signal level superposition and distortion, CRC check errors, frame loss, and device communication freezes.

[0003] Existing mainstream solutions for RS485 multi-node conflicts in industrial settings have significant shortcomings: The host computer sequentially calls out each electric gripper to send and receive data, completely avoiding multi-master contention. However, the more nodes there are, the longer the polling cycle becomes, resulting in a serious lack of real-time performance for synchronous grasping and emergency clamping actions. Furthermore, a single point of failure in the host computer will directly cause the entire group of grippers to malfunction, making it impossible to achieve distributed autonomous communication.

[0004] Traditional simplified carrier sensing mechanisms only set a uniform fixed random delay, and the backoff time interval after all gripper collisions is the same. When multiple nodes collide continuously, the probability of repeated collisions is extremely high. There is no priority distinction, and emergency synchronization capture commands will wait in the same way as normal state reported data, which cannot meet the requirements of high real-time control.

[0005] CAN bus and industrial Ethernet come with built-in hardware arbitration and CSMA / CD conflict detection, but electric grippers require additional replacement of communication transceiver chips and addition of isolation circuits, which significantly increases the cost of hardware modification and does not meet the low-cost multi-gripper networking requirements of small and medium-sized production lines.

[0006] Assigning fixed transmission time slots based on gripper IDs results in extremely poor scalability. Adding a new gripper requires re-modifying timing parameters, and bus bandwidth utilization drops drastically after more than 32 nodes. Existing technologies lack a distributed conflict suppression scheme that is compatible with universal, low-cost RS485 transceiver chips, requires no additional hardware modifications, balances multi-node expansion with high-priority real-time preemption, and can adapt to continuous conflicts. Consequently, it is difficult to support synchronous and collaborative gripping operations with more than 32 electric grippers.

[0007] To address this, a conflict adaptive backoff control method for electric gripper groups based on RS485 bus is proposed. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by proposing a conflict adaptive backoff control method for electric gripper groups based on an RS485 bus.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A conflict adaptive backoff control method for an electric gripper group based on an RS485 bus is disclosed. Multiple electric grippers are connected in parallel to the same RS485 differential bus as multiple master nodes. Each electric gripper has a built-in communication control unit that executes an improved CSMA / CD protocol. The method includes the following steps: S1: Bus carrier sensing and prediction; Before any electric gripper is ready to send a data frame, the communication control unit continuously samples the differential level of the RS485 bus to determine the bus status; if the bus is idle, it immediately sends a data frame; if the bus is occupied, it continues to monitor until the bus is idle. S2: Real-time collision detection during transmission; When the electric gripper sends a data frame, it synchronously compares its own output level with the bus sampling level. If the levels are inconsistent, it determines that there is a bus conflict, immediately terminates the transmission, and enters the backoff calculation process. S3: Calculation of dynamic backoff duration based on priority parameters; Upon detecting a conflict, read the local two-level priority parameters: the unique hardware ID of the gripper and the urgency level of the current data frame to be sent; generate a differentiated basic backoff window based on the two-level priority parameters; the higher the priority, the smaller the basic backoff window value; S4: Consecutive Conflicts Binary Exponential Backoff Expansion When a single electric gripper collides with N times consecutively, the basic backoff window is exponentially amplified: backoff window = basic backoff window × 2^(N-1); after the data is successfully sent, the number of consecutive collisions is cleared to zero, and the exponential amplification factor is reset. S5: High-priority frame preemptive transmission scheduling; When both high-priority and low-priority data frames exist in the buffer queue, a preemption mechanism is enabled; when the bus is idle, high-priority frames are sent first; if the transmission of a low-priority frame has not exceeded the preemption breakpoint, the high-priority gripper sends a preemption flag to interrupt the low-priority transmission; after the high-priority frame transmission is completed, the low-priority gripper retryes the transmission. Step S6: Transmission complete, collision count reset; After sending a complete data frame without collision and receiving a response frame, the number of consecutive collisions on the local machine is reset to zero.

[0010] Preferably, the urgency level of the data frame is divided into three levels: The first-level frame is a synchronous capture and emergency clamping protection action frame, and it has bus preemption privileges; The second-level frame is the clamping force adjustment and point fine-tuning instruction frame; Level 3 frames are data frames for timed status reporting by the device and have no preemption privileges.

[0011] Preferably, the unique hardware ID of the gripper is independently encoded from 0 to 63. The smaller the ID value, the higher the priority and the smaller the base backoff window value.

[0012] Preferably, the preemption breakpoint is the transmission interval of the first two bytes of a single frame; after the number of bytes sent in a low-priority frame exceeds the preemption breakpoint, the high-priority gripper is prohibited from initiating a preemption interruption.

[0013] Preferably, the method achieves conflict suppression only through software protocol logic, without replacing RS485 transceiver hardware or adding bus wiring, and a single RS485 bus can stably connect 32-64 electric grippers.

[0014] Preferably, the electric gripper independently completes carrier sensing, collision detection, and backoff retry without the need for polling and scheduling by the host computer; multiple electric grippers can still complete synchronous grasping interaction through RS485 bus when the host computer is offline.

[0015] The beneficial effects of this invention are: This solution achieves conflict suppression through software protocol improvements, uses standard RS485 transceiver chips, requires no replacement of CAN or Ethernet hardware, and does not increase wiring or isolation circuit costs, making it suitable for networking in high-volume, low-cost electric gripper production lines.

[0016] Dynamic priority backoff significantly reduces repeated conflicts: Abandoning global fixed random delay, the backoff window is dynamically allocated by combining gripper ID and data urgency level, and high real-time grabbing instructions occupy the bus first; with the addition of continuous conflict binary exponential backoff, the retry timing is distributed in multi-node congestion scenarios, reducing the bus conflict rate by more than 70%.

[0017] For high-urgency actions such as synchronous grasping, it supports bus preemption, solving the problem of excessive delay in emergency commands in traditional polling and fixed backoff schemes, and controlling the timing error of multi-gripper synchronous collaborative grasping actions to the millisecond level.

[0018] Furthermore, it breaks through the traditional RS485 bus 32-node hardware bottleneck, stably supports up to 64 electric grippers connected to the same bus, and new grippers can be connected simply by configuring a unique ID, without the need to re-plan time slots or modify the host scheduling program, thus exhibiting strong scalability.

[0019] By eliminating the dependency on mandatory polling from the host computer, each electric gripper independently performs carrier sensing, collision detection, and backoff retry. Even if the host computer crashes, the grippers can still complete local synchronous grasping interaction, thus improving the system's fault tolerance.

[0020] The combination of multiple mechanisms, including instant idle bus transmission, high-priority preemption, and exponential avoidance of continuous conflicts, increases the effective transmission bandwidth of the bus by 40%-60% compared to the fixed polling scheme. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the conflict adaptive backoff control method for electric gripper groups based on RS485 bus proposed in this invention. Detailed Implementation

[0022] 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.

[0023] Example: Refer to Figure 1 The electric gripper group employs a conflict adaptive backoff control method based on an RS485 bus. Multiple electric grippers are connected in parallel to the same RS485 differential bus as multiple master nodes. Each electric gripper has a built-in communication control unit that executes the improved CSMA / CD protocol, including the following steps: S1: Bus carrier sensing and prediction; Before any electric gripper is ready to send a data frame, the communication control unit continuously samples the differential level of the RS485 bus to determine the bus status; if the bus is idle, it immediately sends a data frame; if the bus is occupied, it continues to monitor until the bus is idle. S2: Real-time collision detection during transmission; When the electric gripper sends a data frame, it synchronously compares its own output level with the bus sampling level. If the levels are inconsistent, it determines that there is a bus conflict, immediately terminates the transmission, and enters the backoff calculation process. S3: Calculation of dynamic backoff duration based on priority parameters; Upon detecting a conflict, read the local two-level priority parameters: the unique hardware ID of the gripper and the urgency level of the current data frame to be sent; generate a differentiated basic backoff window based on the two-level priority parameters; the higher the priority, the smaller the basic backoff window value; S4: Consecutive Conflicts Binary Exponential Backoff Expansion When a single electric gripper collides with N times consecutively, the basic backoff window is exponentially amplified: backoff window = basic backoff window × 2^(N-1); after the data is successfully sent, the number of consecutive collisions is cleared to zero, and the exponential amplification factor is reset. S5: High-priority frame preemptive transmission scheduling; When both high-priority and low-priority data frames exist in the buffer queue, a preemption mechanism is enabled; when the bus is idle, high-priority frames are sent first; if the transmission of a low-priority frame has not exceeded the preemption breakpoint, the high-priority gripper sends a preemption flag to interrupt the low-priority transmission; after the high-priority frame transmission is completed, the low-priority gripper retryes the transmission. Step S6: Transmission complete, collision count reset; After sending a complete data frame without collision and receiving a response frame, the number of consecutive collisions on the local machine is reset to zero.

[0024] Specifically, the urgency level of data frames is divided into three levels: The first-level frame is a synchronous capture and emergency clamping protection action frame, and it has bus preemption privileges; The second-level frame is the clamping force adjustment and point fine-tuning instruction frame; Level 3 frames are data frames for timed status reporting by the device and have no preemption privileges.

[0025] Furthermore, the gripper has a unique hardware ID with an independent encoding from 0 to 63. The smaller the ID value, the higher the priority and the smaller the base backoff window value.

[0026] Furthermore, the preemption breakpoint is the first two bytes of a single frame's transmission interval; once the number of bytes sent in a low-priority frame exceeds the preemption breakpoint, the high-priority gripper is prohibited from initiating a preemption interrupt.

[0027] Finally, the method achieves conflict suppression solely through software protocol logic, without requiring replacement of RS485 transceiver hardware or additional bus wiring. A single RS485 bus can stably support 32-64 electric grippers, each independently performing carrier sensing, conflict detection, and backoff retries without requiring polling and scheduling by the host computer. Even when the host computer is offline, multiple electric grippers can still achieve synchronous grasping interaction via the RS485 bus.

[0028] In this embodiment, the production line has a total of 64 servo electric grippers, all of which are connected in parallel to a single RS485 two-wire differential bus with a baud rate of 9600bps. Each gripper's MCU has a built-in CSMA / CD communication program improved in this invention, and is assigned IDs 0-63. Priority parameter configuration is urgent: Level 1 frame: Multi-gripper synchronous grasping trigger command, allowing preemptive transmission; Secondary frame: Clamping force closed-loop adjustment, stroke point modification; Level 3 frames: Automatically report clamping opening, motor temperature, and load current every 200ms; ID0-15 are high-speed gripper stations with a basic retraction window baseline value of 1ms; ID16-63 are regular sorting stations with a basic retraction window baseline value of 3ms.

[0029] In a normal, conflict-free transmission process, gripper ID0 receives the synchronous grab trigger signal and buffers a high-priority frame. The communication unit samples the bus and finds no differential level, determines that the bus is idle, directly drives the DE pin to enable, and sends the complete synchronous grab command. There are no level conflicts throughout the process, and the continuous conflict count remains at 0 after the transmission is completed.

[0030] The dual-node collision adaptive backoff process involves ID0 and ID20 grippers simultaneously generating frames to be sent, synchronously driving the bus to generate a level collision. Both parties detect in real time that the transmitted level is inconsistent with the bus level and immediately stop transmission. The basic backoff window for ID0 is 1ms, and the basic backoff window for ID20 is 3ms. After a delay of 1ms and 3ms respectively within random intervals, both re-listen to the bus, significantly reducing the probability of secondary collisions. If a collision occurs again during this retry, the number of consecutive collisions N=2, and the backoff window is increased by 2 times. The backoff interval for ID0 becomes 1-2ms, and for ID20 it becomes 3-6ms. For the third collision, N=3, and the window is increased by 4 times again. This exponential expansion continues until successful transmission.

[0031] In the preemptive real-time scheduling implementation, ID30 gripper is sending a Level 3 status reporting frame, transmitting only 1 byte. At this time, ID0 generates a synchronization capture Level 1 frame and sends a preset preemption level flag to the bus. ID30 communication unit recognizes the preemption signal, immediately stops sending, buffers the remaining reporting data, and enters a 3ms basic backoff wait. After ID0 completely transmits the synchronization capture command, the bus becomes idle, and ID30 listens to the bus again to complete the transmission of the remaining reporting frames. If ID30 has already sent 3 bytes, exceeding the preemption breakpoint, ID0 cannot preempt and waits for the current low-priority frame transmission to finish before sending again.

[0032] In a large-scale continuous congestion scenario, 64 grippers simultaneously trigger timed status reporting. In the first round, a large number of nodes experience conflicts, and each gripper generates a differentiated basic window based on its own ID. As the number of continuous conflicts continues to accumulate, the backoff time increases exponentially, and the retry transmission timing of each gripper is completely dispersed. There is no continuous signal distortion on the bus and no frame loss. When the production line issues a synchronous grabbing command, high-priority grippers can preempt the bus to ensure that the grabbing action is executed synchronously.

[0033] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0034] 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.

[0035] 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 conflict adaptive backoff control method for an electric gripper group based on an RS485 bus, wherein multiple electric grippers are connected in parallel to the same RS485 differential bus as multiple master nodes, characterized in that, Each electric gripper has a built-in communication control unit that executes the improved CSMA / CD protocol, including the following steps: S1: Bus carrier sensing and prediction; Before any electric gripper is ready to send a data frame, the communication control unit continuously samples the RS485 bus differential level to determine the bus status; if the bus is idle, the data frame is sent immediately. If the bus is occupied, it will continue to monitor until the bus is free; S2: Real-time collision detection during transmission; When the electric gripper sends a data frame, it synchronously compares its own output level with the bus sampling level. If the levels are inconsistent, it determines that there is a bus conflict, immediately terminates the transmission, and enters the backoff calculation process. S3: Calculation of dynamic backoff duration based on priority parameters; Upon detecting a conflict, read the two-level priority parameters of the local machine: the unique hardware ID of the gripper and the urgency level of the current data frame to be sent; Generate a differentiated basic backoff window based on two priority parameters; The higher the priority, the smaller the base backoff window value; S4: Consecutive Conflicts Binary Exponential Backoff Expansion When a single electric gripper collides with N times consecutively, the basic backoff window is exponentially amplified: backoff window = basic backoff window × 2^(N-1); after the data is successfully sent, the number of consecutive collisions is cleared to zero, and the exponential amplification factor is reset. S5: High-priority frame preemptive transmission scheduling; When both high-priority and low-priority data frames exist in the buffer queue, a preemption mechanism is enabled; when the bus is idle, high-priority frames are sent first; if the transmission of a low-priority frame has not exceeded the preemption breakpoint, the high-priority gripper sends a preemption flag to interrupt the low-priority transmission; after the high-priority frame transmission is completed, the low-priority gripper retryes the transmission. Step S6: Transmission complete, collision count reset; After sending a complete data frame without collision and receiving a response frame, the number of consecutive collisions on the local machine is reset to zero.

2. The conflict adaptive backoff control method for an electric gripper group based on an RS485 bus according to claim 1, characterized in that, The data frame urgency level is divided into three levels: The first-level frame is a synchronous capture and emergency clamping protection action frame, and it has bus preemption privileges; The second-level frame is the clamping force adjustment and point fine-tuning instruction frame; Level 3 frames are data frames for timed status reporting by the device and have no preemption privileges.

3. The conflict adaptive backoff control method for an electric gripper group based on an RS485 bus according to claim 2, characterized in that, The unique hardware ID of the gripper is independently encoded from 0 to 63. The smaller the ID value, the higher the priority and the smaller the base backoff window value.

4. The conflict adaptive backoff control method for an electric gripper group based on an RS485 bus according to claim 3, characterized in that, The preemption breakpoint is the transmission interval of the first two bytes of a single frame; after the number of bytes sent by a low-priority frame exceeds the preemption breakpoint, the high-priority gripper is prohibited from initiating a preemption interruption.

5. The conflict adaptive backoff control method for an electric gripper group based on an RS485 bus according to claim 4, characterized in that, The method achieves conflict suppression solely through software protocol logic, requiring no replacement of RS485 transceiver hardware or additional bus wiring. A single RS485 bus can stably support 32-64 electric grippers.

6. The conflict adaptive backoff control method for an electric gripper group based on an RS485 bus according to claim 5, characterized in that, The electric gripper independently completes carrier sensing, collision detection, and backoff retry without the need for polling and scheduling by the host computer; multiple electric grippers can still complete synchronous grasping interaction through RS485 bus when the host computer is offline.

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