Electromagnetic stop control system for a collaborative robot joint module based on a planetary reducer

Abstract

The application provides a planetary reducer-based cooperative robot joint module electromagnetic stop control system and belongs to the technical field of robot control, which comprises a master control calculation module, a servo drive module, a backup energy storage unit, a torque motor, a planetary reduction module, an electromagnetic brake module and a double-sided encoding unit. When power failure is determined, the servo drive module extracts the locally latched gravity feedforward torque data, uses the back electromotive force and the backup energy storage unit to control the motor output hybrid synthesized torque to brake and offset the gravity drop bias. Combined with the synchronous calculation of the transmission torsion angle of the two sets of encoding units, the step current is injected to force the rotor to micro-move into the mechanical back-lash gap window, output the suspended micro-current to pass through the mechanical response delay period of the brake and complete the stop together. The application actively releases the stress compression state of the internal gear of the reducer, avoids the direct mechanical brake to generate residual extrusion stress, and thus eliminates the secondary impact risk when the system is re-powered.

Description

Technical Field

[0001] This invention relates to the field of robot control technology, and in particular to an electromagnetic stop control system for collaborative robot joint modules based on planetary reducers. Background Technology

[0002] Collaborative robots are widely used in industrial manufacturing and human-machine interaction scenarios. The core joint module is highly integrated with a torque motor, planetary reducer and electromagnetic braking device. During normal operation, the servo drive system provides a continuous stator current to the torque motor to generate electromagnetic torque to overcome the robot arm's own gravity and execute the preset motion trajectory. When the system encounters a sudden power failure or triggers an emergency stop, the torque motor instantly loses the command from the external bus and the support of the main power supply. At this time, the electromagnetic braking device must be used to lock the rotor shaft to prevent the robot arm from falling under the action of gravity and causing a safety accident.

[0003] In existing joint modules, there is a disconnect between the control logic and the physical mechanical mechanism when handling power failure braking conditions. In the normally closed electromagnetic braking device, after the power supply to the coil is cut off, the internal reset spring releases and pushes the armature to press the friction plate. Objectively, there is a mechanical response delay of tens of milliseconds. During the delay period from power supply cut-off to the friction plate fully establishing friction lock, the motor output torque returns to zero, and the robotic arm will fall and deflect due to its own gravity because it loses electrical lifting force.

[0004] Because of the inherent mechanical backlash at the meshing point of the internal gears in a planetary reducer, a brief gravitational drop can cause the transmission gears to quickly cross the stress-free backlash range, resulting in the tooth surfaces squeezing together and forming a unidirectional gravitational pressure state. Existing braking control systems adopt a strategy of directly cutting off the electrical output and passively waiting for the mechanical brake to engage. This means that the electromagnetic brake ultimately achieves physical locking under a state of force engagement within the transmission mechanism. This braking process under load causes the reducer to be subjected to transient compressive stress, and this stress remains between the tooth surfaces during parking. When the system restores power and the electromagnetic brake is re-energized and released, the accumulated tooth surface stress is released instantaneously, causing the joint module to experience sudden displacement rebound and secondary mechanical impact. Long-term stress braking and power-on impact not only make it difficult to guarantee the original position reset accuracy before and after stopping, but also aggravate the wear of the precision reducer's tooth surfaces, affecting the overall service life of the collaborative robot. Therefore, this application provides an electromagnetic stop control system for the joint module of a collaborative robot based on a planetary reducer to meet the requirements. Summary of the Invention

[0005] The purpose of this invention is to provide an electromagnetic stop control system for the joint module of a collaborative robot based on a planetary reducer in order to solve the above-mentioned problems. This system solves the problems of falling due to mechanical delay of the brake when the existing collaborative robot brakes, as well as the residual compressive stress inside the reducer and the secondary impact when the robot is powered on due to locking under load.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] The collaborative robot joint module electromagnetic stop control system based on planetary reducer is characterized by including a main control computing module, a communication bus module, a servo drive module, a torque motor module, a planetary reducer module, an electromagnetic braking module, a motor-side encoding unit, and an output-side encoding unit.

[0008] The main control computing module is used to solve the dynamic attitude of the entire arm and calculate the gravity feedforward torque data;

[0009] The main control computing module establishes a bidirectional data connection with the servo drive module through the communication bus module; the servo drive module is internally equipped with a local cache unit, a logic control unit, an inverter drive unit, and a backup energy storage unit.

[0010] The servo drive module is externally electrically connected to the torque motor module and the electromagnetic brake module; the rotor shaft of the torque motor module is mechanically connected to the input end of the planetary reduction module.

[0011] The motor-side encoding unit and the output-side encoding unit are respectively electrically connected to the logic control unit;

[0012] When a physical power failure or emergency stop is triggered, the logic control unit extracts gravity feedforward torque data from the local cache unit, controls the inverter drive unit and the backup energy storage unit to drive the stator winding to generate a mixed composite torque, calculates the transmission torsion angle based on the current position feedback value, causes the rotor to move slightly until the transmission torsion angle enters the mechanical backlash window, and cancels the output, with the electromagnetic braking module taking over the position locking.

[0013] Furthermore, the main control computing module is used to calculate the overall arm dynamic attitude and gravity feedforward torque data. During normal operation, the main control computing module combines the position feedback information of each joint of the robotic arm to calculate the overall arm dynamic attitude and extract the gravity torque component applied to the rotation axis of the target joint as gravity feedforward torque data. The main control computing module synchronously sends the gravity feedforward torque data to the corresponding servo drive module via the communication bus module. The logic control unit is used to parse and extract the gravity feedforward torque data and continuously overwrite the gravity feedforward torque data into the independent address space of the local cache unit for state registration. The system continuously updates and stores the static bias parameters for the current attitude during the normal communication cycle, providing a source of low-level prior data extraction in the power-off communication isolation state.

[0014] Furthermore, the logic control unit continuously monitors the external power supply voltage status at the input of the servo drive module and the real-time heartbeat messages of the communication bus module. When the external power supply voltage drops to a preset undervoltage threshold or the heartbeat message loss time of the communication bus module exceeds a preset timeout threshold, the system is determined to trigger a physical power failure or emergency stop interruption. The logic control unit isolates the position loop commands of the communication bus module. The backup energy storage unit seamlessly intervenes in the power supply circuit, the logic control unit stops the overwrite operation, and copies and transfers the last fully overwritten and updated gravity feedforward torque data to the internal solidified register for latching. Multi-source status cross-verification is used to determine input abnormal events, block external interference commands, and isolate and solidify the characteristic parameters at the moment of power failure for subsequent compensation calculations.

[0015] Furthermore, the logic control unit reads the angular velocity calculated by the motor-side encoding unit, and calculates the transient back EMF generated in the stator winding under the current state based on the current angular velocity and the back EMF constant of the torque motor module. It then inverts the last fully overwritten and updated gravity feedforward torque data as the target bias torque command, and uses the back EMF energy generated by the torque motor module to output an asymmetric duty cycle modulation signal to the inverter drive unit, driving the stator winding to generate a hybrid torque. The remaining kinetic energy of the rotor is recovered and converted into internal electrical control energy, generating a drive control quantity with active compensation characteristics in the event of a main power supply failure.

[0016] Furthermore, the hybrid torque is decoupled into a damping torque component and a bias torque component. The damping torque component is in the opposite direction to the current angular velocity and is used to dissipate kinetic energy. The magnitude of the bias torque component is equal to the latched gravity feedforward torque data and its direction is opposite, used to counteract the gravity-induced bias. When the maximum output electromagnetic torque corresponding to the transient back electromotive force is less than the target bias torque command, the logic control unit controls the backup energy storage unit to release part of the electrical energy to make up for the voltage difference required by the stator winding. The two types of torques, energy dissipation and compensation, are independently controlled to simultaneously eliminate the influence of mechanical gravity compression during the system deceleration phase, establishing a dynamic equilibrium condition with no external force bias.

[0017] Furthermore, when the current angular velocity decays and falls below a preset safety threshold, the logic control unit uses a low-level hardware timer to send a synchronous latching command to the motor-side encoding unit and the output-side encoding unit. Simultaneously, it acquires multi-turn absolute angular position data from the rotor side and the reducer output as current position feedback values. This data, combined with the planetary reduction module's rated reduction ratio and the factory-calibrated zero-position offset compensation parameters, is used to calculate the transmission torsion angle. The transmission torsion angle is then compared with the factory-calibrated mechanical backlash window boundary value. By acquiring the multi-turn position coordinates of the input and output ends at the same time slice, the actual deformation and deviation within the reduction structure are quantified, and the actual physical contact boundary of the gears is determined.

[0018] Furthermore, if the transmission torsion angle exceeds the numerical closed interval formed by the boundary values ​​of the mechanical backlash window, the logic control unit determines the compensation polarity based on the direction of the excess polarity and generates a transient step current command containing directional information in conjunction with the system's preset reference step current amplitude. The inverter drive unit extracts energy from the backup energy storage unit and injects a transient step current into the stator winding of the torque motor module, breaking the static meshing state of the gear meshing surface and forcing the rotor of the torque motor module to produce micro-motion. The short-time sudden current is used to form a transient excitation torque to overcome static friction, peeling away the already compressed transmission contact surface to reconstruct the tooth surface clearance.

[0019] Furthermore, before generating the transient step current command, the logic control unit detects the current DC bus voltage of the servo drive module. Based on the equivalent capacitance of the internal electrolytic capacitors and the difference between the square of the current DC bus voltage and the square of the lowest operating voltage at the chip's underlying layer, it calculates the remaining available energy of the system. Combining the absolute amplitude of the transient step current command with the equivalent phase resistance of the stator windings, it converts the remaining available energy into the maximum allowable output duration of the transient step current command. A mathematical constraint relationship is established between the hardware voltage and electrical output energy consumption, allocating the underlying control chip the necessary base power margin to maintain operation.

[0020] Furthermore, once the transmission torsion angle enters the mechanical backlash window, the logic control unit records the absolute position value currently fed back by the motor-side encoding unit as the zero-point position of the suspension target. Through discretized position loop closed-loop calculations, the inverter drive unit continuously outputs a position suspension micro-current to the torque motor module to maintain the transmission torsion angle stable within the stress-free range inside the mechanical backlash window. An internal closed-loop steady state is constructed for the existing mechanical free clearance, restricting the transmission chain from drifting and maintaining the independent state of the physical mechanism, free from force contact.

[0021] Furthermore, the power supply circuit of the electromagnetic braking module's coil is simultaneously cut off at the instant the micro-current is suspended at the output position. The logic control unit maintains the micro-current output while the accumulated timing of the internal hardware timer does not exceed the mechanical response delay time threshold. When the accumulated timing reaches the mechanical response delay time threshold, it is determined that the friction plates of the electromagnetic braking module are physically pressed shut, the output is canceled, the electromagnetic braking module takes over the position locking, and the power supply channel to the stator winding of the torque motor module is completely cut off. The system smoothly transitions from an active electromagnetic levitation state to a passive physical locking state maintained entirely by the electromagnetic braking module. The electrical drive timing is set to overcome the inherent response time blind zone of the physical friction components, achieving a stress-free transition between electromagnetic maintenance and mechanical braking.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] 1. This invention uses a local cache unit to overwrite gravity feedforward torque data at a fixed communication cycle, and physically isolates external commands when a power failure is detected, transferring the last updated data to an internal fixed register for latching. This technical feature enables the servo drive module to prevent data tampering caused by memory reuse when it loses external main control computing power and communication support, providing an instant and accurate dynamic force reference for the underlying logic control unit, and ensuring reliable takeover and data security of the control system in the power failure island state.

[0024] 2. This invention calculates the current transient back electromotive force and combines it with the latched gravity data to control the inverter drive unit to output an asymmetric duty cycle modulation signal to generate a hybrid torque. This design uses the damping torque component to consume the residual kinetic energy of the mechanical mechanism, while using the bias torque component to counteract the downward tendency of the robotic arm due to gravity. When the back electromotive force decays, the backup energy storage unit releases electrical energy to make up for the voltage difference, thereby maintaining the force balance of the joints throughout the deceleration and braking phase and relieving the pressure state of the internal gears of the planetary reducer under unidirectional gravity.

[0025] 3. This invention utilizes dual-sided encoders to synchronously calculate the transmission torsion angle. When it is determined that the gear is under pressure, a transient step current is injected to force the rotor to micro-move into the clearance range. Subsequently, the output position is suspended by a micro-current to maintain this stress-free state until the electromagnetic braking module completes physical locking by crossing the inherent mechanical response delay time. This timing coordination mechanism of electrical control and mechanical response allows the gear to complete parking within the free clearance after escaping contact stress, avoiding the internal residual compression stress caused by direct mechanical braking, thereby reducing the risk of secondary mechanical impact caused by stress release when the system is powered on again. Attached Figure Description

[0026] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate embodiments of the invention and, together with the specification, further serve to explain the principles of the invention and enable those skilled in the art to practice and use the invention.

[0027] Figure 1 This is a system architecture diagram of the present invention;

[0028] Figure 2 This is a flowchart of the method of the present invention;

[0029] Figure 3 This is the timing diagram for gravity feedforward buffering and power outage islanding triggering in this invention;

[0030] Figure 4 This is a flowchart of the dynamic hybrid braking and transmission clearance calculation process of the present invention;

[0031] Figure 5 This is a flowchart of the active micro-motion optimization and zero-stress interlocking control of the present invention;

[0032] Figure 6 This is a time-domain response curve of the power-off drop displacement of the present invention;

[0033] Figure 7 This is a convergence phase trajectory diagram of the transmission torsion angle of the present invention.

[0034] Figure label:

[0035] 10. Main control computing module; 20. Communication bus module; 30. Servo drive module; 40. Torque motor module; 50. Planetary reduction module; 60. Electromagnetic brake module; 70. Motor-side encoding unit; 80. Output-side encoding unit; 31. Local cache unit; 32. Logic control unit; 33. Inverter drive unit; 34. Backup energy storage unit.

[0036] As shown in the figure, specific structures and devices are marked in the figure to clearly illustrate the structure of the embodiments of the present invention. However, this is only for illustrative purposes and is not intended to limit the present invention to this specific structure, device and environment. Those skilled in the art can adjust or modify these devices and environments according to specific needs. Detailed Implementation

[0037] The electromagnetic stop control system for collaborative robot joint modules based on planetary reducers provided by the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should also be noted that, to make the embodiments more detailed, the following embodiments are the best and preferred embodiments, and those skilled in the art can use other alternative methods to implement some known technologies; moreover, the accompanying drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.

[0038] It should be noted that the use of terms such as "an embodiment," "an embodiment," "an exemplary embodiment," and "some embodiments" in the specification indicates that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments (whether explicitly described or not) should be within the knowledge of those skilled in the art.

[0039] Terms can be understood, at least in part, from their use in context. For example, depending at least in part on the context, the term “one or more” as used herein can be used to describe any feature, structure, or characteristic in a singular sense, or a combination of features, structures, or characteristics in a plural sense. Additionally, the term “based on” can be understood not necessarily to convey an exclusive set of factors, but rather, alternatively, depending at least in part on the context, to allow for the presence of other factors that are not necessarily explicitly described.

[0040] See attached document Figure 1 This invention provides an electromagnetic stop control system for a joint module based on a planetary reducer. The system may include:

[0041] The system includes a main control computing module 10, a communication bus module 20, a servo drive module 30, a planetary reduction module 50, a torque motor module 40, an electromagnetic braking module 60, a motor-side encoding unit 70, and an output-side encoding unit 80.

[0042] The main control computing module 10 is used to solve the dynamic attitude of the entire arm and calculate the gravity feedforward torque data;

[0043] The communication bus module 20 is used for bidirectional transmission of data and control commands between nodes;

[0044] The servo drive module 30 is used to receive data and control the operation of the underlying hardware components. The main control computing module 10 establishes a bidirectional data connection with the servo drive module 30 through the communication bus module 20.

[0045] The servo drive module 30 is internally equipped with a local cache unit 31, a logic control unit 32, an inverter drive unit 33, and a backup energy storage unit 34. The local cache unit 31 is used to overwrite and latch gravity feedforward torque data at high frequency. The logic control unit 32 is used to perform state calculation and stop timing control. The inverter drive unit 33 is used to output drive current to the motor stator winding according to the duty cycle modulation signal. The backup energy storage unit 34 is used to provide basic operating power for the servo drive module 30 in the event of a power failure. The backup energy storage unit 34 is connected in parallel to both ends of the DC bus of the servo drive module 30.

[0046] The servo drive module 30 is externally electrically connected to the torque motor module 40 and the electromagnetic brake module 60. The torque motor module 40 is used to output mechanical torque and generate back electromotive force during the deceleration phase.

[0047] The electromagnetic braking module 60 is used to lock the position of the motor rotor shaft by mechanical friction in the power-off state. The electromagnetic braking module 60 is a normally closed braking device when power is off.

[0048] The rotor shaft of the torque motor module 40 is mechanically connected to the input end of the planetary reduction module 50. The planetary reduction module 50 is used to reduce the speed of the torque motor module 40 and amplify the torque for power output.

[0049] The motor-side encoding unit 70 is installed on the rotor side of the torque motor module 40 and electrically connected to the logic control unit 32. The motor-side encoding unit 70 is used to acquire the absolute angular position and angular velocity of the rotor of the torque motor module 40 at high frequency. The output-side encoding unit 80 is installed on the output end of the planetary reduction module 50 and electrically connected to the logic control unit 32. The output-side encoding unit 80 is used to acquire the absolute angular position of the output end of the planetary reduction module 50 at high frequency.

[0050] See attached document Figure 2 This invention provides an electromagnetic stop control method for a joint module based on a planetary reducer, the method comprising the following steps:

[0051] S10, the main control calculation module 10 calculates the dynamic posture of the whole arm and the gravity feedforward torque borne by the target joint according to a fixed communication cycle, and sends the gravity feedforward torque data through the communication bus module 20. After the servo drive module 30 receives the data, the logic control unit 32 writes the data to the local cache unit 31 at high frequency.

[0052] S20, when a physical power failure or emergency stop is triggered, the logic control unit 32 isolates the position loop command of the communication bus module 20, the backup energy storage unit 34 intervenes in the power supply circuit to maintain the basic logic operation, and the logic control unit 32 extracts and latches the last updated gravity feedforward torque data from the local cache unit 31.

[0053] S30, the logic control unit 32 reads the angular velocity calculated by the motor-side encoding unit 70, and uses the back electromotive force energy generated by the torque motor module 40 to output an asymmetric duty cycle modulation signal to the inverter drive unit 33. The inverter drive unit 33 drives the stator winding to generate a hybrid torque to dissipate kinetic energy and counteract the gravitational downward bias.

[0054] S40, when the angular velocity is lower than the preset safety threshold, the logic control unit 32 reads the current position feedback values ​​of the motor-side encoding unit 70 and the output-side encoding unit 80, calculates the transmission torsion angle in combination with the rated reduction ratio of the planetary reduction module 50, and compares the transmission torsion angle with the factory-calibrated mechanical backlash window boundary value.

[0055] S50, if the transmission torsion angle exceeds the mechanical backlash window, the logic control unit 32 controls the inverter drive unit 33 to release the energy of the backup energy storage unit 34 according to the direction of exceeding the polarity, and injects a transient step current into the torque motor module 40 to make the rotor move slightly until the transmission torsion angle enters the mechanical backlash window.

[0056] S60, when the transmission torsion angle enters the mechanical backlash window, the logic control unit 32 controls the inverter drive unit 33 to continuously output a position floating micro current to the torque motor module 40, simultaneously cutting off the coil power supply circuit of the electromagnetic brake module 60, and maintaining the position floating micro current output within the mechanical response delay time of the electromagnetic brake module 60 until the friction plate is physically pressed and closed, after which the output is canceled and the position locking is taken over by the electromagnetic brake module 60.

[0057] See attached document Figure 3 The specific implementation of S10 can be handled through sub-steps:

[0058] S101, the main control calculation module 10 acquires the position feedback information of each joint of the entire robotic arm in real time according to a fixed communication cycle. The main control calculation module 10 combines the position feedback information of each joint of the robotic arm to calculate the dynamic posture of the entire arm and calculate the gravity feedforward torque borne by the target joint.

[0059] During the normal operation of the collaborative robot, the main control computing module 10 determines the instantaneous pose of the robotic arm linkage mechanism in three-dimensional space by summarizing the real-time angle feedback of each joint. The kinematic and dynamic analysis of the robotic arm's spatial pose is performed based on existing rigid body dynamics modeling methods.

[0060] Considering that the robotic arm is physically hinged by multiple links and that each link will generate a static offset torque at the target joint's rotation axis due to gravity, the main control calculation module 10 substitutes the currently acquired whole-arm position data into the preset robot system gravity model to extract the gravity torque component applied to the target joint's rotation axis. This robot system gravity model is a rigid body static analytical model constructed based on the prior real physical parameters of the robotic arm, requiring no data samples or training steps. The gravity torque component constitutes the gravity feedforward torque in this invention. The gravity feedforward torque characterizes the theoretical offset torque required by the target joint in the current static state to overcome the downward tendency of the link's own gravity. The relevant calculation relationship is expressed as follows:

[0061] ;

[0062] In the formula, The gravity feedforward torque calculated for the target joint; This is the spatial joint position vector of the entire robotic arm. The dimensions are determined by the actual number of physical joints of the collaborative robot, and the value range of each dimension is limited by the mechanical limit angle of the corresponding physical joint. The system's preset gravitational moment mapping function, gravitational moment mapping function The internal structure is constructed using Jacobi matrix mapping relationships based on the factory mass distribution parameters, centroid spatial geometric offset parameters, and link length parameters of each link component of the robotic arm.

[0063] S102, the main control calculation module 10 converts the gravity feedforward torque data into a digital format supported by the communication protocol, and the main control calculation module 10 synchronously sends the gravity feedforward torque data to the corresponding servo drive module 30 via the communication bus module 20.

[0064] The main control computing module 10 maintains strict periodic data exchange with the underlying nodes. Gravity feedforward torque data is encapsulated in process data transmission frames and sent along with conventional servo drive control commands at the same communication frequency. In this embodiment of the invention, the fixed communication cycle of the communication bus module 20 can be set to 1 to 4 milliseconds to adapt to the refresh requirements of the underlying position ring. This high-frequency synchronous communication mechanism helps to improve the synchronization of the data transmitted to the node end with the actual spatial movement changes of the robotic arm. The high-frequency synchronous communication mechanism can reduce the parameter hysteresis error generated when the robotic arm moves over a wide range.

[0065] S103, the servo drive module 30 receives a communication frame containing gravity feedforward torque data, the logic control unit 32 parses and extracts the gravity feedforward torque data and writes the gravity feedforward torque data to the local cache unit 31 at high frequency for status registration.

[0066] The local cache unit 31 is configured as an independent address space on the internal memory of the servo drive module 30. Considering the random nature of the triggering time of external physical power failure or communication failure events, the logic control unit 32 performs continuous overwrite operations on the local cache unit 31 according to the refresh frequency of the communication bus module 20. After the logic control unit 32 completes the parsing of a new frame of communication message, it directly writes the latest gravity feedforward torque value extracted into the predetermined address. The latest gravity feedforward torque value extracted overwrites the historical value retained in the previous communication cycle. The continuous overwrite operation is continuously executed in the background logic of the conventional servo control. Through this overwrite mechanism, the servo drive module 30 can always maintain a gravity prior parameter that is consistent with the current actual posture height of the robotic arm. This provides a nearby data extraction benchmark when the system cuts off the external data source and enters an emergency stop island state.

[0067] The specific implementation of S20 can be handled through sub-steps:

[0068] S201, the logic control unit 32 continuously monitors the external power supply voltage status at the input terminal of the servo drive module 30 and the real-time heartbeat message of the communication bus module 20. When the external power supply voltage drops to the preset undervoltage threshold or the heartbeat message loss time of the communication bus module 20 exceeds the preset timeout threshold, the logic control unit 32 determines that the system triggers a physical power failure or emergency stop interruption. The logic control unit 32 immediately sends a blocking signal to the internal bus interface to hardware isolate the position loop command issued by the communication bus module 20. The logic control unit 32 stops responding to the regular servo scheduling request of the external master control computing module 10 and switches to the internal irreversible safety control sequence.

[0069] To accurately trigger the abnormal operating condition detection mechanism, this embodiment of the invention sets the preset undervoltage threshold to 70% to 80% of the rated DC bus voltage of the servo drive module 30 in combination with the hardware electrical characteristics. The preset timeout threshold is set to 3 to 5 times the fixed communication cycle in combination with the communication protocol. By setting clear voltage thresholds and time boundaries, it helps to avoid false triggering of safety timing actions caused by minor fluctuations in the external power grid. Considering that transient electromagnetic interference may occur in industrial sites, resulting in brief heartbeat packet loss, the logic control unit 32 is equipped with a state filter counter. It only outputs an interruption confirmation signal when the number of consecutively lost heartbeat messages reaches the upper limit of the count corresponding to the preset timeout threshold.

[0070] S202, at the instant the external power supply interruption is detected, the main power supply circuit of the servo drive module 30 is physically disconnected, and the backup energy storage unit 34 connected in parallel to both ends of the DC bus of the servo drive module 30 automatically and seamlessly intervenes in the power supply circuit. The electrolytic capacitor array inside the backup energy storage unit 34 begins to discharge to the outside through the DC bus. The DC power released by the backup energy storage unit 34 is processed by the internal step-down and voltage regulation circuit and then transmitted to the logic control unit 32, the motor-side encoding unit 70, and the output-side encoding unit 80 respectively. The limited power provided by the backup energy storage unit 34 is used on the one hand to maintain the processing and computing capabilities of the underlying digital logic of the servo drive module 30 and the position feedback acquisition capability of the dual encoders, and on the other hand, it provides the drive power required for the inverter drive unit 33 to perform subsequent transient active micro-motion and position levitation through the bus channel.

[0071] From the perspective of circuit principle, since the terminal voltage at both ends of the electrolytic capacitor array cannot change abruptly, the DC bus voltage will decay exponentially as the charge is released. This requires the logic control unit 32 to acquire the system reference parameters within a limited time window in order to complete the scheduling and allocation of all subsequent stop control timings before the DC bus voltage drops to the lowest operating voltage of the underlying chip.

[0072] S203, after completing the hardware power supply circuit switch and confirming that it is in a communication island state, the logic control unit 32 stops the background overwrite operation of writing new data to the local cache unit 31. The logic control unit 32 directly accesses the predetermined address space of the local cache unit 31 and extracts the gravity feedforward torque data of the last complete overwrite update. The logic control unit 32 copies the extracted gravity feedforward torque data and transfers it to the internal fixed register for latching.

[0073] The last fully overwritten and updated gravity feedforward torque data latched will serve as a static reference for subsequent dynamic braking compensation when disconnected from the bus environment. The data transfer latching action helps to prevent the residual gravity feedforward torque data from being accidentally rewritten by other underlying interrupt programs due to memory address reuse. The local latching mechanism provides prior data support for the load force state of the robotic arm after the servo drive module 30 loses the computing power support of the main control computing module 10.

[0074] See attached document Figure 4 The specific implementation of S30 can be handled through sub-steps:

[0075] S301, the logic control unit 32 reads the current angular velocity collected by the motor-side encoding unit 70 at high frequency in real time, and the logic control unit 32 calculates the transient back electromotive force generated in the stator winding under the current state based on the current angular velocity and the back electromotive force constant of the torque motor module 40.

[0076] In the event of a physical power outage causing the external drive power supply to be cut off, the rotor of the torque motor module 40 continues to rotate under the drive of the system's residual kinetic energy. During this stage, the torque motor module 40 switches to generator operation mode and generates a back electromotive force (EMF) at the stator winding terminals. The amplitude of the back EMF is proportional to the current angular velocity of the torque motor module 40. The logic control unit 32 performs a quantitative assessment of the system's currently available self-generated electrical energy boundary based on Faraday's law of electromagnetic induction. The relevant back EMF calculation relationship is expressed as follows:

[0077] ;

[0078] In the formula, This is the transient back electromotive force generated by the torque motor module 40; The back electromotive force constant is the factory-calibrated value of the torque motor module 40. The value is determined by the permanent magnet flux linkage inside the torque motor module 40 and the number of turns of the stator winding; The current angular velocity is calculated by the motor-side encoding unit 70.

[0079] S302, the logic control unit 32 calculates the target bias torque command required to maintain the current attitude of the target joint by combining the last fully overwritten and updated gravity feedforward torque data. The logic control unit 32 outputs an asymmetric duty cycle modulation signal to the inverter drive unit 33 according to the mapping relationship between the target bias torque command and the transient back electromotive force.

[0080] To help prevent the robotic arm from falling uncontrollably due to its own weight while releasing the residual kinetic energy of the system, the logic control unit 32 changes the conventional three-phase bridge arm symmetrical short-circuit braking mode. The logic control unit 32 generates a duty cycle modulation vector containing asymmetric characteristics by independently controlling the conduction time of the switching transistors of the three-phase upper and lower bridge arms inside the inverter drive unit 33. The logic control unit 32 inverts the last fully overwritten and updated gravity feedforward torque data as the target bias torque command. The logic control unit 32 uses the internal closed-loop regulator to calculate the three-phase bias current vector required to achieve the target bias torque command.

[0081] The logic control unit 32 performs asymmetric offset superposition on the basic duty cycle used for short-circuit braking based on the three-phase bias current vector to generate the final duty cycle modulation vector. Considering that the transient back EMF will gradually decay to the point where it cannot support the consumption of the target bias torque command alone as the speed decreases, the logic control unit 32 monitors the amplitude of the transient back EMF in real time and calculates the torque boundary in the current pure self-generated state in real time in combination with the physical parameters of the stator winding. The relevant maximum electromagnetic torque estimation formula is expressed as follows:

[0082] ;

[0083] In the formula, This represents the maximum output electromagnetic torque corresponding to the transient back electromotive force. This refers to the torque constant specified at the factory for the torque motor module 40. This is the currently calculated transient back electromotive force; The equivalent phase resistance of the stator winding of the torque motor module 40 is the maximum output electromagnetic torque corresponding to the transient back electromotive force. When the torque is less than the target bias torque command, the logic control unit 32 controls the backup energy storage unit 34 to release part of the electrical energy to make up for the voltage difference required by the stator winding.

[0084] S303, the inverter drive unit 33 controls the high-frequency switching action of the internal power devices according to the asymmetric duty cycle modulation signal. The inverter drive unit 33 drives the stator winding of the torque motor module 40 to generate a hybrid torque to simultaneously realize the dissipation of kinetic energy and the offset of gravity falling.

[0085] The hybrid torque is physically decoupled into two independently acting torque components. The first component is a damping torque, which is always opposite to the direction of the current angular velocity. It is used to dissipate the mechanical kinetic energy stored in the system's transmission mechanism and to reduce the speed of the torque motor module 40. The second component is a bias torque, which is equal in magnitude to the last fully overwritten and updated gravity feedforward torque data and is opposite in direction. It is used to balance the unidirectional force exerted by the robot arm load in the current pose. The relevant hybrid torque composition relationship is expressed as follows:

[0086] ;

[0087] In the formula, This refers to the actual combined torque generated by the stator windings; This refers to the damping torque component in the composite torque. This is the bias torque component in the composite torque used to counteract the effects of gravity.

[0088] The control logic sets the bias torque component in the hybrid composite torque used to counteract the effects of gravity to satisfy the following relationship:

[0089] ;

[0090] In the formula, This is the bias torque component in the composite torque used to counteract the effects of gravity. The gravity feedforward torque data is the last fully overwritten and updated data stored in the internal fixed register of the servo drive module 30.

[0091] By configuring the above-mentioned hybrid torque ratio, the dynamic balance of the system force can be maintained during the violent deceleration of the torque motor module 40. The dynamic balance state helps to alleviate the continuous pressure of unidirectional gravity bias on the meshing tooth surface inside the planetary reduction module 50. Relieving the unidirectional gravity bias pressure state establishes zero-force physical boundary conditions for subsequent fine-motion clearance optimization.

[0092] The specific implementation of S40 can be handled through sub-steps:

[0093] S401, the logic control unit 32 continuously monitors the current angular velocity fed back by the motor-side encoding unit 70. When the current angular velocity decays and falls below the preset safety threshold, the logic control unit 32 determines that the residual kinetic energy of the system has been basically dissipated and meets the conditions for performing clearance state detection. The value range of the preset safety threshold is set to 1% to 3% of the rated maximum speed in combination with the rated maximum speed of the torque motor module 40. If the preset safety threshold is set too high, the residual kinetic energy of the system will interfere with the subsequent micro-motion position suspension control. If the preset safety threshold is set too low, it will increase the waiting time of the overall braking response.

[0094] At the moment the trigger condition is met, the logic control unit 32 uses the underlying hardware timer to send a synchronous latching instruction to the motor-side encoding unit 70 and the output-side encoding unit 80. The logic control unit 32 simultaneously obtains the multi-turn absolute angle position data of the rotor side and the multi-turn absolute angle position data of the reducer output end through the hardware synchronization mechanism to help reduce the calculation error caused by the communication time difference. The multi-turn absolute angle position data includes the number of rotations continuously accumulated after the robot arm is powered on to prevent the division calculation distortion caused by the overflow of the number of rotations.

[0095] S402, the logic control unit 32 combines the synchronously acquired absolute angular position data and the rated reduction ratio of the planetary reduction module 50 to calculate the current transmission torsion angle of the system. Under the ideal rigid transmission model, the motor-side rotation angle divided by the reduction ratio should be strictly equal to the output-side rotation angle. However, in actual mechanical structures, the presence of tooth surface clearance and force deformation will cause a difference between the input and output angles. Considering the inherent physical zero-point deviation between the motor-side encoding unit 70 and the output-side encoding unit 80 during mechanical installation, the logic control unit 32 introduces the factory-calibrated zero-position offset compensation parameter to correct the error when calculating the transmission torsion angle. The relevant transmission torsion angle calculation relationship is expressed as follows:

[0096] ;

[0097] In the formula, The calculated current transmission torsion angle; This refers to the absolute angular position data of the rotor side multi-turn synchronously acquired by the motor-side encoding unit 70 at the moment of timer latching; The rated reduction ratio parameters set at the factory for planetary reduction module 50; The output-side encoding unit 80 synchronously acquires multi-turn absolute angular position data of the output terminal at the moment of timer latching; The dual encoder factory zero-position offset compensation parameters are pre-stored in the non-volatile memory inside the servo drive module 30. In this embodiment of the invention, the physical value range of the pre-stored dual encoder factory zero-position offset compensation parameters is defined as -0.5° to +0.5° to cover normal assembly errors.

[0098] S403, the logic control unit 32 reads the factory-pre-calibrated mechanical backlash window boundary value from its internal non-volatile storage area. The logic control unit 32 compares the calculated transmission torsion angle with the mechanical backlash window boundary value. Due to the influence of machining precision, gear meshing clearance objectively exists within the planetary reduction module 50. During the factory calibration stage, applying forward and reverse test torques at the output end can obtain the stress-free free angle range corresponding to the gear clearance. The physical upper and lower limits of the stress-free free angle range constitute the mechanical backlash window boundary value. In this embodiment of the invention, the mechanical backlash window boundary value is specifically represented as a numerical closed interval formed by the lower clearance boundary and the upper clearance boundary. Based on the backlash characteristics of conventional precision planetary reducers, the preset range of the lower limit boundary of the backlash is defined as -0.08° to -0.03°, and the preset range of the upper limit boundary of the backlash is defined as +0.03° to +0.08°. If the calculated transmission torsion angle falls within the closed interval formed by the mechanical backlash window boundary value, it indicates that the internal gear of the planetary reducer module 50 is in a free clearance state without contact force. If the calculated transmission torsion angle exceeds the mechanical backlash window boundary value, it indicates that the internal gear of the planetary reducer module 50 is in a compressed state. The depth assessment of the specific deformation under the compressed state is based on existing material mechanics Hooke's law combined with gear stiffness parameters.

[0099] See attached document Figure 5 The specific implementation of S50 can be handled through sub-steps:

[0100] S501, when it is determined that the transmission torsion angle exceeds the numerical closed interval formed by the boundary value of the mechanical backlash window, the logic control unit 32 calculates the direction in which the transmission torsion angle deviates from the mechanical backlash window to determine the compensation polarity of the subsequent intervention action, and the logic control unit 32 allocates the energy output logic of the backup energy storage unit 34 according to the determined compensation polarity.

[0101] If the calculated transmission torsion angle is greater than the upper limit of the mechanical backlash window boundary value, the logic control unit 32 determines that the internal gear of the planetary reduction module 50 is in a positive force-pressed state and sets the compensation polarity to negative. If the calculated transmission torsion angle is less than the lower limit of the mechanical backlash window boundary value, the logic control unit 32 determines that the internal gear of the planetary reduction module 50 is in a reverse force-pressed state and sets the compensation polarity to positive. The logic control unit 32 generates a transient step current command containing direction information based on the determined compensation polarity in preparation for energy release. The relevant transient step current command calculation relationship is expressed as follows:

[0102] ;

[0103] In the formula, For transient step current commands that include directional information, the absolute amplitude of the command is used in the calculation when calculating energy and maximum allowable output duration. The compensation polarity coefficient is determined based on the deviation direction. When the deviation direction is greater than the upper limit boundary... The value is -1, when the deviation direction is less than the lower limit boundary. The value is 1; The preset range of the reference step current amplitude in this embodiment of the invention is set to 50% to 80% of the rated starting current of the torque motor module 40, in combination with the torque required by the torque motor module 40 to overcome the static friction of the maximum load.

[0104] Considering the limited and continuously decaying total power of the backup energy storage unit 34, the logic control unit 32 detects the current DC bus voltage of the servo drive module 30 in real time before generating the transient step current command. The logic control unit 32 calculates the remaining usable energy of the system based on the equivalent capacitance value of the electrolytic capacitor inside the backup energy storage unit 34 and the difference between the square of the current DC bus voltage and the square of the lowest operating voltage at the chip's bottom layer. This remaining usable energy is then converted into the maximum allowable output duration of the transient step current command. The relevant energy and duration calculation relationship is expressed as follows:

[0105] ;

[0106] ;

[0107] In the formula, The calculated remaining usable energy of the system; The equivalent capacitance value of the electrolytic capacitor array inside the backup energy storage unit 34; The current DC bus voltage is detected in real time; To maintain the lowest underlying operating voltage for the logic control unit 32 chip; The maximum allowable output duration of the calculated transient step current command; For transient step current commands that include directional information, the absolute amplitude of the command is used in the calculation when calculating energy and maximum allowable output duration. This is the equivalent phase resistance of the stator winding.

[0108] S502, the logic control unit 32 sends a transient step current command to the inverter drive unit 33. The inverter drive unit 33 responds to the transient step current command and extracts the energy from the backup energy storage unit 34 to inject the transient step current into the stator winding of the torque motor module 40. The torque motor module 40 responds to the transient step current to generate a transient overcoming torque to force the rotor of the torque motor module 40 to produce micro-motion.

[0109] When the gears inside the planetary reduction module 50 are under pressure, there is a large static friction and contact stress between the tooth surfaces. By injecting a sudden transient step current, the torque motor module 40 outputs a transient overcoming torque that is much greater than the current load resistance. The transient overcoming torque can break the static meshing state of the gear meshing surface within a very short time window and force the rotor of the torque motor module 40 to rotate at a small angle in the direction of force release. Compared with the smooth and gradual current injection method, this step-type sudden current injection method can better peel off the meshing tooth surfaces and help reduce the total energy consumption of the backup energy storage unit 34.

[0110] S503, during the process of transient step current injection and driving rotor micro-motion, the logic control unit 32 continuously and synchronously reads the data of the motor-side encoding unit 70 and the output-side encoding unit 80. The logic control unit 32 refreshes and calculates the current transmission torsion angle at high frequency until the current transmission torsion angle successfully enters the mechanical backlash window.

[0111] Since the rotor's micro-motion directly changes the relative position of the input terminal of the planetary reduction module 50, the logic control unit 32 needs to monitor the dynamically changing transmission torsion angle in real time. Once the latest transmission torsion angle value falls into the numerical closed interval formed by the lower and upper limits of the mechanical backlash clearance window, the logic control unit 32 immediately determines that the gear has disengaged from the force-pressing surface and is in a stress-free free state. At this time, the logic control unit 32 quickly sends a cutoff command to the inverter drive unit 33 to terminate the continued injection of transient step current. By constructing a high-frequency closed-loop position cutoff mechanism based on dual encoder feedback, it helps to avoid the overshoot phenomenon caused by excessive intervention energy leading to excessive rotor micro-motion amplitude and crossing the clearance interval to hit the other side of the tooth surface. If the transmission torsion angle still has not entered the mechanical backlash clearance window when the transient step current injection time reaches the maximum allowable output time, the logic control unit 32 determines that the mechanical structure has physically hard-jammed. The logic control unit 32 will forcibly stop the micro-motion intervention process and directly switch to the subsequent brake timing sequence to retain the bottom-line power energy to maintain the operation of the underlying chip.

[0112] The specific implementation of S60 can be handled through sub-steps:

[0113] S601, after the transmission torsion angle successfully enters the mechanical backlash window, the logic control unit 32 records the absolute position value currently fed back by the motor-side encoding unit 70 as the zero point position of the suspension target. The logic control unit 32 controls the inverter drive unit 33 to continuously output a position suspension micro-current to the torque motor module 40 to maintain the rotor state of the torque motor module 40. In order to avoid physical drift of the rotor of the torque motor module 40 in the stress-free backlash range, the logic control unit 32 calculates the position deviation by subtracting the zero point position of the suspension target from the actual position collected in real time by the motor-side encoding unit 70.

[0114] The logic control unit 32 inputs the position deviation into the internally embedded proportional-integral-derivative (PI-DE) controller for calculation to output the three-phase stator current command required to maintain the zero-point position of the suspended target in real time. The relevant discretized position loop closed-loop operation relationship is expressed as follows:

[0115] ;

[0116] In the formula, For the first The three-phase stator current command output in each control cycle; For the first The position deviation calculated in each control cycle; This represents the position deviation from the previous control cycle; , , These are the proportional coefficient, integral coefficient, and derivative coefficient preset within the proportional-integral-derivative controller, respectively. This is the sequence number of the current discrete control cycle, and its value is a positive integer. This is the discrete historical time step number from the initial moment of control startup to the current moment, used for discrete integral summation; For the first The position deviation is calculated from each discrete historical time step.

[0117] The inverter drive unit 33 injects a position-suspended micro-current into the stator winding of the torque motor module 40 according to the three-phase stator current command. In this embodiment of the invention, the upper limit of the steady-state amplitude of the position-suspended micro-current is clamped to 2% to 8% of the rated current of the torque motor module 40. The electromagnetic torque generated by the position-suspended micro-current is only used to offset the small disturbances of the rotor of the torque motor module 40 itself in order to maintain the transmission torsion angle stable within the stress-free range inside the mechanical backlash window.

[0118] S602, at the instant the microcurrent is suspended at the output position, the logic control unit 32 simultaneously cuts off the coil power supply circuit of the electromagnetic braking module 60 to trigger the mechanical brake action. The hardware timer inside the logic control unit 32 is activated synchronously and starts to accumulate the time. Since the electromagnetic braking module 60 is a normally closed braking device when it loses power and the electromagnetic braking module 60 releases the internal reset spring after losing the coil excitation current and pushes the friction plate to physically press, there is an inherent response time difference. During the period when the accumulated time of the hardware timer does not exceed the mechanical response delay time threshold, the logic control unit 32 controls the inverter drive unit 33 to strictly maintain the output state of the microcurrent suspended at the position.

[0119] Meanwhile, the logic control unit 32 continuously monitors the DC bus voltage of the servo drive module 30 to prevent the backup energy storage unit 34 from running out of power during the mechanical brake waiting period. If the DC bus voltage drops to the bottom protection voltage threshold, the logic control unit 32 will forcibly cut off the position floating micro current in advance. In this embodiment of the invention, the bottom protection voltage threshold is set to 1.05 to 1.15 times the minimum stable operating voltage of the control chip in combination with hardware characteristics to leave sufficient self-storage margin for the system when it is powered off. The position floating micro current can prevent the rotor of the torque motor module 40 from being deflected by gravity due to the mechanical delay dead zone when the friction plate of the electromagnetic brake module 60 is not fully closed.

[0120] The relevant mechanical delay dead-time timing determination relationship is expressed as follows:

[0121] ;

[0122] In the formula, The current timing time accumulated by the internal hardware timer of the logic control unit 32; The preset mechanical response delay time threshold for the system is, in this embodiment of the invention, set in combination with the physical spring response stiffness of the electromagnetic braking module 60 and the rated physical stroke of the friction plate, to be 1.2 to 1.5 times the factory standard closing time of the electromagnetic braking module 60.

[0123] S603, when the logic control unit 32 determines that the current timing time meets the mechanical delay dead zone timing determination relationship, the logic control unit 32 confirms that the friction plate of the electromagnetic braking module 60 has completed the physical pressing and closing action. At this time, the rotor shaft of the torque motor module 40 has been completely mechanically locked by the static friction force provided by the electromagnetic braking module 60. The logic control unit 32 then controls the inverter drive unit 33 to cancel all electrical outputs and completely shut off the power supply channel of the stator winding of the torque motor module 40. The system smoothly transitions from the active electromagnetic levitation state to the passive physical locking state maintained entirely by the electromagnetic braking module 60. Since the locking action occurs when the gear inside the planetary reduction module 50 is in a stress-free free range, the final mechanical parking posture helps to avoid applying any residual compressive stress to the tooth surface of the planetary reduction module 50. The stress-relieved parking state establishes the physical initial condition of zero impact for the subsequent system to be powered on and resume operation. The specific friction plate pressing mechanical calculation of the electromagnetic braking module 60 is based on the existing mechanical statics method.

[0124] To aid in understanding the technical solution of this invention, an application example based on a six-axis collaborative robot handling a five-kilogram load is provided below.

[0125] A six-axis collaborative robot using the joint module of this invention is performing a task of transporting a five-kilogram load. The robotic arm is in a horizontally extended posture, and the second joint bears the downward bias torque of gravity.

[0126] The main control computing module calculates the offset torque required for the second joint to overcome the weight of the entire arm in the current extended posture at a communication cycle of two milliseconds. The gravity feedforward torque data is sent along with the position command, and the logic control unit in the servo drive module writes the gravity feedforward torque data into the local cache at high frequency.

[0127] After the external power supply is disconnected, the servo drive module detects the bus voltage drop and loses the heartbeat message from the communication bus module. The logic control unit physically isolates the position loop command issued by the communication bus module, discharges the backup energy storage unit connected in parallel to the DC bus, and supplies power to the logic control unit and the dual encoders.

[0128] The logic control unit extracts the gravity feedforward torque data from the last cache. The logic control unit converts the back electromotive force generated by the torque motor module and the electrical energy released by the backup energy storage unit into an asymmetric hybrid torque. Under the action of the hybrid torque, the torque motor module reduces the rotor angular velocity and counteracts the gravity downward bias.

[0129] When the rotor angular velocity is lower than the preset safety threshold, the logic control unit compares the current position feedback values ​​of the motor-side encoding unit and the output-side encoding unit to calculate the transmission torsion angle. When the transmission torsion angle exceeds the mechanical backlash window, the logic control unit controls the inverter drive unit to release the energy of the backup energy storage unit. The inverter drive unit injects a transient step current into the torque motor module to drive the rotor micro-motion so that the transmission torsion angle enters the mechanical backlash window.

[0130] After the transmission torsion angle enters the mechanical backlash window, the logic control unit controls the inverter drive unit to output a position floating micro-current. The logic control unit simultaneously cuts off the coil power supply circuit of the electromagnetic braking module and maintains the position floating micro-current output within the mechanical response delay time. After the friction plates of the electromagnetic braking module are physically pressed and closed, the logic control unit cancels the output and the electromagnetic braking module takes over the position locking.

[0131] A comparative experiment was conducted between the proposed solution and the traditional solution by building a test platform for the single-joint power failure stop of a collaborative robot.

[0132] The experimental test object uses a planetary reducer joint module with a rated torque of 100 and a counterweight block with an equivalent full load. In the traditional scheme control group, the power supply to the driver is cut off after power failure and the mechanical spring of the electromagnetic braking module is used for locking. The experimental group of the present invention uses an electromagnetic stop control system and method based on the planetary reducer joint module for locking control.

[0133] During the experiment, the control joint module moved at a constant angular velocity of 30° per second to the horizontal gravity stress point. The experimenter triggered the main power cut-off switch to disconnect the system power supply. The data acquisition instrument synchronously recorded the dual encoder position data, DC bus voltage and motor phase current from the moment of power failure to the moment the system physically stopped. After the system physically stopped, the experimenter recorded the residual torsion angle of the tooth surface and reconnected the power to record the power-on impact current at the moment the servo was enabled.

[0134] The time-domain response curve of the power-off drop displacement corresponding to the traditional scheme is a downward-opening parabola after power failure and has a mechanical oscillation waveform during the locking phase. The time-domain response curve of the power-off drop displacement corresponding to the scheme of the present invention transitions to a horizontal asymptote without fluctuations after power failure.

[0135] In the conventional scheme, the stopping point in the transmission torsion angle convergence phase trajectory diagram is distributed in the numerical region outside the mechanical backlash boundary line. In the scheme of the present invention, the transmission torsion angle convergence phase trajectory diagram has a step broken line in the low speed region and converges inside the closed interval of the mechanical backlash window.

[0136] Table 1: Comparison of Experimental Test Data for Two Power-Off Stopping Schemes

[0137] T01 Traditional solution 50% of rated load 2.618 +0.184 19.45 T02 Traditional solution 80% of rated load 3.812 +0.247 23.76 T03 Traditional solution 100% full load 4.127 +0.281 27.23 T04 Invention Solution 50% of rated load 0.142 +0.021 3.68 T05 Invention Solution 80% of rated load 0.225 -0.014 4.82 T06 Invention Solution 100% full load 0.293 +0.035 5.31

[0138] Refer to Table 1 and Appendix Figure 6 and attached Figure 7 It can be seen that under full-load power failure conditions, the traditional solution test group produced a drop displacement angle of 4.127°, while the solution test group of the present invention output a hybrid torque to control the drop displacement angle at 0.293°. The transmission torsion angle of the traditional solution test group after locking all exceeded the physical boundary of the mechanical backlash window. The solution test group of the present invention injected a transient step current into the torque motor module to drive the rotor micro-motion and adjust the residual transmission torsion angle to within the numerical range of the mechanical backlash window. The highest starting impact current of the traditional solution test group when re-energized reached 27.23 amps, while the highest starting impact current of the solution test group when re-energized while parked within the backlash range was 5.31 amps.

[0139] Experimental results show that the control system and method provided by this invention can control the torque motor module to output a hybrid torque to suppress the drop displacement angle under power failure conditions. The present invention uses transient step current to drive rotor micro-motion so that the transmission torsion angle cuts into the mechanical backlash window. The present invention uses output position floating micro-current in conjunction with electromagnetic braking module to achieve physical locking within the mechanical backlash window. This control method reduces the starting impact current when the joint module is powered on again and realizes physical parking of the collaborative robot in power failure scenarios.

[0140] This invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this invention. To provide the public with a thorough understanding of this invention, specific details are described in detail in the following preferred embodiments; however, those skilled in the art will fully understand the invention even without these details. Furthermore, to avoid unnecessary misunderstanding of the essence of this invention, well-known methods, processes, procedures, components, and circuits are not described in detail.

[0141] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An electromagnetic stop control system for the joint module of a collaborative robot based on a planetary reducer, characterized in that, It includes a main control computing module, a communication bus module, a servo drive module, a torque motor module, a planetary reduction module, an electromagnetic brake module, a motor-side encoding unit, and an output-side encoding unit; The main control computing module is used to solve the dynamic attitude of the entire arm and calculate the gravity feedforward torque data; The main control computing module establishes a bidirectional data connection with the servo drive module through the communication bus module; the servo drive module is internally equipped with a local cache unit, a logic control unit, an inverter drive unit, and a backup energy storage unit. The servo drive module is externally electrically connected to the torque motor module and the electromagnetic brake module; the rotor shaft of the torque motor module is mechanically connected to the input end of the planetary reduction module. The motor-side encoding unit and the output-side encoding unit are respectively electrically connected to the logic control unit; When a physical power failure or emergency stop is triggered, the logic control unit extracts gravity feedforward torque data from the local cache unit, controls the inverter drive unit and the backup energy storage unit to drive the stator winding to generate a mixed composite torque, calculates the transmission torsion angle by combining the current position feedback value, causes the rotor to move slightly until the transmission torsion angle cuts into the mechanical backlash window, cancels the output and the electromagnetic braking module takes over the position locking. When the logic control unit continuously monitors the external power supply voltage status at the input of the servo drive module and the real-time heartbeat message of the communication bus module, and determines that the system triggers a physical power failure or emergency stop interruption when the external power supply voltage drops to a preset undervoltage threshold or the heartbeat message loss time of the communication bus module exceeds a preset timeout threshold, the logic control unit isolates the position loop command of the communication bus module; the backup energy storage unit seamlessly intervenes in the power supply circuit, the logic control unit stops the overwrite operation, and copies and transfers the gravity feedforward torque data of the last complete overwrite update to the internal solidified register for latching; The logic control unit calculates the transient back electromotive force generated in the stator winding under the current state based on the current angular velocity and the back electromotive force constant of the torque motor module. It inverts the last fully overwritten and updated gravity feedforward torque data as the target bias torque command and outputs an asymmetric duty cycle modulation signal to the inverter drive unit in combination with the mapping relationship between the target bias torque command and the transient back electromotive force, thereby driving the stator winding to generate a hybrid torque. The hybrid torque is decoupled into a damping torque component and a bias torque component. The direction of the damping torque component is opposite to the current angular velocity and is used to dissipate kinetic energy. The magnitude of the bias torque component is equal to the latched gravity feedforward torque data and the direction is opposite to the current angular velocity and is used to counteract the gravity downward bias. When the maximum output electromagnetic torque corresponding to the transient back electromotive force is less than the target bias torque command, the logic control unit controls the backup energy storage unit to release part of the electrical energy to make up for the voltage difference required by the stator winding. When the current angular velocity decays and falls below a preset safety threshold, the logic control unit uses the underlying hardware timer to send a synchronous latching command to the motor-side encoding unit and the output-side encoding unit. At the same time, it acquires the multi-turn absolute angular position data of the rotor side and the multi-turn absolute angular position data of the reducer output end. It calculates the transmission torsion angle by combining the rated reduction ratio of the planetary reduction module and the factory-calibrated zero-position offset compensation parameters, and compares the transmission torsion angle with the factory-calibrated mechanical backlash window boundary value. If the transmission torsion angle exceeds the numerical closed interval formed by the boundary values ​​of the mechanical backlash window, the logic control unit determines the compensation polarity based on the direction of the excess polarity and generates a transient step current command containing directional information in combination with the preset reference step current amplitude of the system. The inverter drive unit extracts energy from the backup energy storage unit and injects a transient step current into the stator winding of the torque motor module, breaking the static meshing state of the gear meshing surface and forcing the rotor of the torque motor module to produce micro-motion.

2. The electromagnetic stop control system for collaborative robot joint modules based on planetary reducers according to claim 1, characterized in that, During normal operation, the main control computing module is used to calculate the dynamic posture of the entire arm by combining the position feedback information of each joint of the robotic arm and extract the gravitational torque component applied to the rotation axis of the target joint as the gravity feedforward torque data; the main control computing module synchronously sends the gravity feedforward torque data to the corresponding servo drive module via the communication bus module; the logic control unit is used to parse and extract the gravity feedforward torque data and continuously overwrite the gravity feedforward torque data into the independent address space of the local cache unit for state registration.

3. The electromagnetic stop control system for the joint module of a collaborative robot based on a planetary reducer according to claim 1, characterized in that, Before generating the transient step current command, the logic control unit detects the current DC bus voltage of the servo drive module, calculates the remaining available energy of the system based on the equivalent capacitance value of the internal electrolytic capacitor and the difference between the square of the current DC bus voltage and the square of the lowest operating voltage of the chip, and combines the absolute amplitude of the transient step current command and the equivalent phase resistance of the stator winding to convert the remaining available energy of the system into the maximum allowable output duration of the transient step current command.

4. The electromagnetic stop control system for collaborative robot joint modules based on planetary reducers according to claim 1, characterized in that, When the transmission torsion angle enters the mechanical backlash clearance window, the logic control unit records the absolute position value currently fed back by the motor-side encoding unit as the zero point position of the suspension target. Through discretized position loop closed-loop operation, the inverter drive unit continuously outputs a position suspension micro-current to the stator winding to maintain the transmission torsion angle stable within the stress-free range inside the mechanical backlash clearance window.

5. The electromagnetic stop control system for the joint module of a collaborative robot based on a planetary reducer according to claim 4, characterized in that, At the instant the microcurrent is output at the position, the power supply circuit of the electromagnetic braking module coil is simultaneously cut off. The logic control unit maintains the output state of the microcurrent while the cumulative timing time of the internal hardware timer does not exceed the mechanical response delay time threshold. When the cumulative timing time reaches the mechanical response delay time threshold, it is determined that the friction plate of the electromagnetic braking module has completed the physical pressing and closing action, all electrical outputs are canceled and the power supply channel of the stator winding of the torque motor module is completely cut off. The system smoothly transitions from the active electromagnetic levitation state to the passive physical locking state maintained entirely by the electromagnetic braking module.

Images