Integrated CAN (Controller Area Network) connection system of wheeled crane, communication quality adjusting method and crane

Abstract

The invention belongs to the technical field of engineering machinery CAN bus communication, and discloses a wheeled crane integrated CAN connection system, a communication quality adjusting method and a crane. The system comprises an injection-molded integrated CAN line, a trunk of which extends to a concentration area, and branches of which are in plug-in connection with distributed control elements; at least two independent CAN network interfaces, an adjustable terminal resistor and a communication quality adjusting unit are subjected to one-time injection molding packaging through a multi-layer PCB (Printed Circuit Board); the communication quality adjusting unit performs error frame detection, shielding and filtering amplification on each branch signal, and automatically reduces the rate of a non-key signal or sends the non-key signal in a time-limited manner when the load rate is greater than or equal to 70%. A large number of transition joints are replaced by a pre-cast integrated structure, the problems of vibration loosening, large wiring occupied space, strong magnetic and strong current interference, error frame diffusion and high-load clamping stagnation are solved, and crane CAN communication which is resistant to interference, free of maintenance, high in reliability and low in cost is achieved.

Description

Technical Field

[0001] This invention belongs to the field of CAN bus communication technology for wheeled cranes, and particularly relates to an integrated CAN connection system for wheeled cranes, a communication quality adjustment method, and the crane itself. Background Technology

[0002] Wheeled cranes commonly use CAN bus to achieve real-time data interaction between the engine, force limiter, main valve, sensors, and human-machine interface. In traditional solutions, each node is connected in parallel to the main trunk via standard CAN cables through T-junctions, and then connected to an independent terminating resistor to form a bus topology. This solution has the following drawbacks: numerous junction boxes requiring dedicated clips for fixation, resulting in high material and assembly costs; junction boxes are prone to loosening due to vehicle vibration, leading to increased contact resistance and signal reflection; branch cables are messy, occupying wiring space and making design changes difficult; high-voltage equipment such as the boom and winch motors generate broadband electromagnetic interference, causing bit flips and resulting in erroneous frames; when the number of nodes increases or the data volume surges, the bus load rate increases, leading to message collisions, delays, or even frame drops, affecting safe operation.

[0003] Chinese patent CN116545691A discloses a method and apparatus for transmitting CAN data, employing AES encryption to indicate data and resist replay attacks, but it does not solve the problems of physical layer connection reliability and excessive load rate. Chinese patent CN202010283020 discloses an injection-molded wire harness and its molding method, providing a method for molding the wire harness, but only improving harness protection and consistency, without addressing network topology optimization and signal quality adjustment. Chinese patent CN116143002A discloses a sliding displacement counterweight system, a sliding displacement method, and engineering machinery, replacing some wired connections with a wireless self-organizing network. While this reduces long cables, the wireless link has blind spots in cranes with dense metal structures, and a CAN transition connector is still required. In summary, the industry urgently needs a whole-machine-level CAN connection solution that can simultaneously solve the problems of "connection reliability, anti-interference, error frame suppression, and load self-adjustment." Summary of the Invention

[0004] Purpose of the invention: In view of the shortcomings of the prior art, the purpose of this invention is to provide an integrated CAN connection system, adjustment method and crane that is precast integral, maintenance-free, resistant to electromagnetic interference, can automatically shield error sources and dynamically reduce load rate.

[0005] Technical solution: The integrated CAN connection system for wheeled cranes described in this invention includes: The injection-molded integrated CAN cable has a main trunk and several branches branching off from the main trunk. The branches are used to connect to distributed control elements, while the main trunk is used to extend to centralized deployment areas. An integrated CAN plug-in module integrates the interfaces of at least two independent CAN networks into the same injection-molded housing using a multi-layer PCB circuit board. The housing is provided with a backbone socket for interfacing with the backbone and component sockets for interfacing with each CAN component in a centralized layout area. An adjustable terminating resistor is embedded in the injection-molded housing of the integrated CAN plug-in module and electrically connected to a multi-layer PCB circuit board. It is used to adjust the terminating resistor of the corresponding CAN network to a standard value. The communication quality adjustment unit, integrated on a multi-layer PCB board, is used to perform error frame detection, shield error frame sources, filter and amplify signals for each branch of the CAN signal, and to detect network load rate and reduce the transmission rate of non-critical signals or limit their transmission time when the load rate exceeds the threshold.

[0006] Preferably, the splitter of the injection-molded integrated CAN line has a PCB adapter board, which electrically connects the main CAN_H and CAN_L to the corresponding CAN_H and CAN_L of several branches, and arranges common mode chokes and ESD protection devices on the PCB adapter board.

[0007] Preferably, the communication quality adjustment unit includes: The error frame detection and blocking module is used to shut down the transmit and receive channels of the same branch and report the error information to the display terminal when the number of consecutive error frames in the same branch exceeds a preset value. The filtering and signal amplification module is used to perform bandpass filtering, amplitude compensation, and differential signal enhancement on the CAN signal after filtering out erroneous frames. The load rate detection and adjustment module is used to count the CAN bus utilization using a sliding time window, and to initiate a slowdown or time-limited transmission strategy for non-critical identifiers when the utilization rate is ≥70%. The load rate detection and adjustment module is also used to restore the slowed-down or time-limited non-critical signals to the normal transmission rate when the network load rate is below 30%.

[0008] Preferably, the adjustable terminal resistor is a dual-channel independent programmable resistor array, corresponding to the CAN1 network and the CAN2 network respectively. The resistance value of each programmable resistor array is adjustable from 50Ω to 70Ω in 1Ω increments.

[0009] Preferably, the outer surface of the injection-molded housing of the integrated CAN plug-in module is provided with a shielding coating, and the ground plane of the multi-layer PCB circuit board is electrically connected to the shielding coating through a conductive spring to form a 360° shielding cavity.

[0010] Preferably, both the main socket and the component socket are keyway sockets that prevent incorrect insertion, and the sockets integrate a switch terminal that allows insertion before disconnection, which is used to maintain continuous terminal resistance during hot-plugging.

[0011] Preferably, the outer sheath of the injection-molded CAN line is made of TPU material, and a stress-reducing cone sleeve is formed by secondary injection molding at the branch point. The Shore A hardness of the stress-reducing cone sleeve is 80±5.

[0012] Preferably, the communication quality adjustment unit further includes a temperature compensation circuit for compensating for temperature drift of the adjustable terminating resistor within the range of -40℃ to +85℃, so that the terminating resistor change rate is ≤±1%.

[0013] The present invention also provides a CAN communication quality adjustment method, comprising: Real-time error frame detection is performed on the CAN signal of each branch. When the error frame count exceeds the threshold, the branch is blocked and a fault code is reported. Bandpass filtering and differential amplification are performed on the CAN signal that passes the error frame detection to improve the common-mode rejection ratio; The bus load rate within a predetermined time window is calculated. If the load rate is greater than the set upper limit, the transmission frequency of non-critical identifiers is reduced or their transmission duration is shortened according to the priority table. If the load rate is less than the set lower limit, the normal transmission parameters of non-critical identifiers are restored.

[0014] The present invention further provides a wheeled crane equipped with the above-mentioned integrated CAN connection system, wherein the distributed control elements include length and angle sensors, pressure sensors and solenoid valve actuators, and the CAN elements in the centralized area include a main controller, a display and a force limiter.

[0015] Beneficial effects: Compared with the prior art, the present invention has the following advantages: (1) Precast integrated: The injection-molded integrated CAN line and integrated CAN plug module replace the traditional “cable + T-type head + independent resistor” mode, reducing the number of transition parts by more than 60%, reducing material costs by 35%, and reducing assembly time by 50%. (2) Vibration resistance and loosening prevention: The injection molding layer and stress buffer cone sleeve eliminate the relative displacement of the joint. After 5 g random vibration, 48 h salt spray and 1000 h heat aging test, the contact resistance change is <2 mΩ; (3) Electromagnetic interference resistance: The 360° shielded cavity + common mode choke improves the injection immunity to 100 V / m, meeting the ISO 11452-2 level 4 electromagnetic shielding requirements, and the error frame rate is reduced by two orders of magnitude; (4) Automatically shielding error sources: When a branch has 8 consecutive error frames, the branch is shut down and a fault code is reported within 0.8 ms to prevent the spread of error frames from causing the whole machine to lose control; (5) Dynamic load adjustment: When the load rate is ≥70%, the cycle of non-critical signals with priority ≤7 is doubled or the transmission time is limited to 1ms, the bus utilization rate is reduced to below 55%, and the message delay is <5ms, to ensure the real-time performance of critical commands such as boom luffing and hoisting. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the integrated CAN connection system structure of the crane of the present invention; Figure 2 A schematic diagram illustrating the optimization of CAN network signals within an integrated CAN plug-in module; Figure 3 Circuit diagram of PCB adapter board for injection molded integrated CAN line splitter; Figure 4 Workflow diagram for the communication quality adjustment unit; Figure 5 This is a CAN topology diagram of a wheeled crane. Detailed Implementation

[0017] The following is in conjunction with the appendix Figure 1-5 The present invention will be further described in detail below with reference to specific embodiments.

[0018] The integrated CAN connectivity system for wheeled cranes described in this invention includes: The injection-molded integrated CAN cable has a main trunk and several branches branching off from the main trunk. The branches are used to connect to distributed control elements, while the main trunk is used to extend to centralized deployment areas. An integrated CAN plug-in module integrates the interfaces of at least two independent CAN networks into the same injection-molded housing using a multi-layer PCB circuit board. The housing is provided with a backbone socket for interfacing with the backbone and component sockets for interfacing with each CAN component in a centralized layout area. An adjustable terminating resistor is embedded in the injection-molded housing of the integrated CAN plug-in module and electrically connected to a multi-layer PCB circuit board. It is used to adjust the terminating resistor of the corresponding CAN network to a standard value. The communication quality adjustment unit, integrated on a multi-layer PCB board, is used to perform error frame detection, shield error frame sources, filter and amplify signals for each branch of the CAN signal, and to detect network load rate and reduce the transmission rate of non-critical signals or limit their transmission time when the load rate exceeds the threshold.

[0019] Injection-molded integrated CAN cable: See Figure 1 , Figure 3The injection-molded integrated CAN cable 20 includes a trunk 21, a splitter, and three branches 22. The splitter has an embedded PCB adapter board made of 1.6 mm thick FR-4 board. The front wiring layer connects the trunk CAN_H and CAN_L to the branches 22 in a star configuration. The back is entirely copper-clad as a ground plane, and a common-mode choke L1 (51 μH / 100 MHz) is connected in series at the entrance of each branch, and a TVS array D1 (24 V bidirectional) is connected in parallel for ESD protection. The splitter's exterior uses a TPU secondary injection molding to form a stress-absorbing cone sleeve. The outer diameter of the large end of the cone sleeve is 28 mm, and the outer diameter of the small end is 16 mm, with a Shore A 80±5, reducing the bending radius to 25 mm without damaging the insulation.

[0020] Integrated CAN connector module: See Figure 1 , Figure 2 , Figure 3 The integrated CAN plug-in module 30 has a rectangular injection-molded housing measuring 120 mm × 80 mm × 35 mm. The housing surface is coated with Ni-Cu conductive paint to form a shielding coating with a surface resistance of <50 mΩ. Inside the housing is a multi-layer PCB (six-layer board, 0.2 mm thick), with the upper layer housing two CAN interface circuits, an adjustable terminating resistor, and a communication quality adjustment unit. The adjustable terminating resistor consists of an array of eight precision resistors and analog switches, programmable in 1 Ω increments, with a default power-on setting of 60 Ω, calibrated online by the main controller via I²C. The side walls of the housing feature main sockets and component sockets, all with keyway-type anti-misinsertion structures, and integrated miniature switch terminals to ensure the terminating resistor remains effective during hot-swapping.

[0021] Communication quality conditioning unit: See Figure 2 , Figure 4 The communication quality conditioning unit is based on an FPGA+ARM SoC and has the following built-in features: The error frame detection and masking module performs frame-by-frame CRC, ACK, and EOF checks on the RX / TX of each branch 22. If the cumulative number of error frames is ≥8 within 1ms, the solid-state relay is driven to disconnect the power supply to the transceiver of that branch, and the fault code is uploaded to the display via CANopen EMCY message. The filtering and signal amplification module uses a bandpass filter (bandwidth 800 kHz to 1.2 MHz) and a differential operational amplifier (gain 6 dB) to improve the common-mode rejection ratio to 85 dB; The load rate detection and adjustment module uses a 10 ms sliding window to count the bus utilization. If the utilization is ≥70%, the sending period of identifiers with priority ≤7 will be doubled or the frame length will be limited to ≤1 ms according to the priority table. When the utilization is <30%, it will automatically recover.

[0022] Wheeled crane overall topology: See Figure 1 , Figure 5 The crane includes an operator's cab, turntable, boom, and control box 44. Boom sensors 45, pressure sensors 46, and solenoid valves 47 are distributed on the boom and connected to the main trunk via an injection-molded integrated CAN cable 20. They are then connected to the CAN1 network of the integrated CAN plug-in module 30 through the main trunk interface. The main controller 41, display 42, and force limiter 43 are centrally located in the control box 44 and connected to the CAN1 and CAN2 networks via component interfaces. Adjustable terminating resistors calibrate the CAN1 and CAN2 terminals to 60.0 Ω respectively. After 500 hours of on-site testing, the CAN bus error frame rate was <0.01 frame / s, the peak load rate decreased from 82% to 54%, and no communication bottlenecks were observed.

[0023] Temperature compensation: The adjustable terminating resistor array uses low-temperature drift resistors with a temperature of ±5 ppm / ℃, and NTC thermistors are arranged on PCB 33. The ARM SoC compensates in real time according to the temperature curve from -40℃ to +85℃, so that the terminating resistor change rate is ≤±1%, ensuring that the signal reflection coefficient is ≤-25 dB when starting at low temperature of -40℃ and operating continuously at high temperature of 85℃.

[0024] Hot-swap maintenance: When replacing the integrated CAN plug-in module 30, plug it in first and then disconnect the switch terminal to ensure that the terminating resistor is still connected across the bus, avoiding network reflections due to terminal loss. Actual testing showed that the module replacement was completed under engine running and a load of 1.2 times the rated load, and the bus did not experience a single disconnection or error frame.

[0025] Through the above embodiments, the present invention achieves high reliability, maintenance-free operation, anti-interference, and intelligent load adjustment of crane CAN connection, and can be extended to complex equipment bus systems such as automobiles and port machinery.

Claims

1. An integrated CAN connection system for a wheeled crane, characterized in that The application relates to a trunk and branch CAN line, a trunk and branch CAN line integrated module, an adjustable terminal resistance, a communication quality adjustment unit, and a PCB adapter plate. The trunk and branch CAN line integrated module integrates interfaces of at least two independent CAN networks in the same injection shell through a multilayer PCB circuit board, the injection shell is provided with a trunk socket for being connected with the trunk and element sockets for being connected with CAN elements in a centralized arrangement area. The adjustable terminal resistance is embedded in the injection shell of the trunk and branch CAN line integrated module and is electrically connected with the multilayer PCB circuit board, and is used for adjusting the terminal resistance of the corresponding CAN network to a standard value. The communication quality adjustment unit is integrated in the multilayer PCB circuit board, is used for performing error frame detection, shielding error frame sources, filtering and signal amplification on the CAN signals of each branch, and is used for detecting a network load rate and reducing the transmission rate or limiting the transmission time of non-key signals when the load rate exceeds a threshold value. The PCB adapter plate is arranged in the trunk and branch CAN line integrated module, and respectively electrically connects trunk CAN_H and CAN_L with CAN_H and CAN_L of a plurality of branches, and arranges common mode choke coils and ESD protection devices on the PCB adapter plate.

2. The integrated CAN connection system of claim 1, wherein, The communication quality adjustment unit comprises:

3. The integrated CAN connection system of claim 1 or 2, wherein, An error frame detection and shielding module is used for shutting down the transceiving channel of the branch and reporting error information to a display terminal when the error frame count of the same branch continuously exceeds a preset value. A filtering and signal amplification module is used for performing band-pass filtering, amplitude compensation and differential signal enhancement on the CAN signals filtered of error frames. A load rate detection and adjustment module is used for counting the utilization rate of a CAN bus through a sliding time window, and starts a speed reduction or time-limited sending strategy for non-key identifiers when the utilization rate is greater than or equal to 70%, and restores the non-key signals reduced in speed or limited in time to a normal sending rate when the network load rate is less than 30%. The adjustable terminal resistance is a two-way independent programmable resistance array corresponding to CAN1 network and CAN2 network, and the resistance adjustment range of each programmable resistance array is 50 omega to 70 omega with a step of 1 omega.

4. The integrated CAN connection system of claim 1, wherein, The outer surface of the injection shell of the trunk and branch CAN line integrated module is provided with a shielding coating, and the ground plane of the multilayer PCB circuit board is electrically connected with the shielding coating through a conductive spring piece to form a 360-degree shielding cavity.

5. The integrated CAN connection system of claim 1, 2, or 4, wherein, The trunk socket and the element socket are key and groove type sockets for preventing wrong insertion, and integrated switch terminals for inserting first and then disconnecting are arranged in the sockets to maintain the continuity of the terminal resistance during hot plugging.

6. The integrated CAN connection system of claim 5, wherein, The outer sheath of the trunk and branch CAN line is made of TPU and is secondarily injection molded to form a stress buffer cone sleeve at the branch.

7. The integrated CAN connection system of claim 1, wherein, The application relates to a trunk and branch CAN line, a trunk and branch CAN line integrated module, an adjustable terminal resistance, a communication quality adjustment unit, and a PCB adapter plate.

8. A CAN communication quality adjustment method applied to the integrated CAN connection system of any one of claims 1 to 9, characterized in that, Real-time error frame detection is performed on the CAN signals of each branch, the branch is shielded and a fault code is reported when the error frame count exceeds a threshold value; Band-pass filtering and differential amplification are performed on the CAN signals detected through the error frame detection to improve the common mode rejection ratio of the signals. ​ The total bus load rate in a predetermined time window is counted, if the load rate is greater than a set upper limit, the sending frequency or the sending time length of non-critical identifiers is reduced according to the priority table, if the load rate is less than a set lower limit, the normal sending parameters of the non-critical identifiers are restored.

9. The method of claim 8, wherein, After shielding the branch, periodically attempt to enable the shielded branch with a redundant diagnostic frame, if no error frame is detected for three consecutive attempts, automatically restore the branch communication.

10. A wheel crane, characterized in that The integrated CAN connection system of any one of claims 1 to 9, wherein the distributed arrangement of control elements includes length angle sensors, pressure sensors, and solenoid valve drivers, and the centralized arrangement area of CAN elements includes a master controller, a display, and a force limiter.

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