Safety control method for position and moment alternation of man-machine cooperation collision scene

Abstract

The invention provides a safety control method for position and torque alternation of a man-machine cooperation collision scene, and belongs to the field of industrial robots, and the method comprises the steps: S1, under a normal condition, enabling a robot to perform trajectory tracking in a position control mode, and continuously correcting a position error; s2, collision detection is conducted through a sliding mode control algorithm, and when a collision signal is detected, it is judged that the robot collides with the outside; s3, when it is detected that the robot collides, the robot is switched to a torque control mode, and an active buffering mechanism is started; s4, detecting whether the robot stops collision or not, if not, executing a torque mode, performing speed detection and torque detection, and starting a protection mechanism; if so, executing the step S5; and S5, when the robot is separated from the impact surface, the robot automatically returns to the position control mode and waits for standby. According to the invention, the safety and performance of the industrial robot working in the same space as people can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial robots, and in particular to a method for safely controlling the alternation of position and torque in a human-robot collaborative collision scenario. Background Art

[0002] With the increasing use of human-machine interaction, the control characteristics of robots and their impact on safety performance must be considered in the design of robot control systems. Industrial robots may collide due to malfunctions, incorrect user input, or unforeseen changes in the operating environment. Especially when industrial robots interact with the external environment, a fast-response and safe shutdown control mechanism is required in the event of a collision. Currently, the protection strategies that have been implemented can be divided into two categories:

[0003] (1) Passive protection strategy, which considers the buffering after the collision and the protection of the robot body.

[0004] Many manufacturers are opting to add flexible skins to their robot shells. This approach transforms traditional industrial manipulators into collaborative robots. For example, the classic industrial manipulator (KUKA Cybertech) offers an optional industrial protective skin (AIRSKIN). Studies have shown that for transient collisions, passive protective skins can reduce impact forces by up to 40%. However, during quasi-static contact, cushioning skins, whether active or passive, cannot match the collision detection response of collaborative robots with built-in flexible cushioning.

[0005] (2) Active protection strategy: After a collision occurs, the motor actively buffers and offsets the impact force. For transient collisions, the time when collision detection is triggered and the motor starts to respond is strongly related to the working conditions at the time of the collision, making it difficult to specify a trigger control strategy. During the quasi-static contact process, the extrusion force accumulates, and the servo motor will detect the position error in real time and report the error, forcing the motor to power off. The robot host computer will not be able to use any control strategy to implement the buffer mechanism. Summary of the Invention

[0006] The object of the present invention is to solve at least one of the technical drawbacks.

[0007] To this end, the purpose of the present invention is to propose a safe control method for alternating position and torque in a human-robot collaborative collision scenario, which can improve the safety and performance of industrial robots when working in the same space with humans.

[0008] To achieve the above objectives, an embodiment of the present invention provides a method for safety control of alternating position and torque in a human-machine collaborative collision scenario, comprising the following steps:

[0009] Step S1: Under normal circumstances, the robot works in the position control mode to track the trajectory and continuously correct the position error;

[0010] Step S2: Using a sliding mode control algorithm to perform collision detection, when a collision signal is detected, it is determined that the robot has collided with the outside world;

[0011] Step S3: When a collision is detected in the robot, the robot switches to a torque control mode and activates an active buffering mechanism;

[0012] Step S4: Check whether the robot has stopped colliding. If it has not stopped, execute the torque mode, perform speed detection and torque detection, and activate the protection mechanism. If it has stopped, execute step S5.

[0013] Step S5: When the robot is separated from the impact surface, the robot automatically returns to the position control mode and waits.

[0014] Furthermore, during the process from step S1 to step S5, the joint torque is obtained by measuring the current of the DC motor, and the speed and torque are monitored.

[0015] Furthermore, the position control mode includes: issuing a position instruction to the servo motor and performing follow-up correction on the position error to achieve movement to a desired position.

[0016] Furthermore, in step S2, the use of the sliding mode control algorithm for collision detection includes: predicting the total external force received by the robot during the dynamic process through a sliding mode observer, and once the predicted external force exceeds a threshold, it is determined that a collision signal is detected.

[0017] Furthermore, in step S2, when a collision between the robot and the outside world is detected, the robot state data measured by the joints is recorded.

[0018] Furthermore, the robot status data includes: motor current torque, full-range speed, and servo status information.

[0019] Furthermore, in step S3, the torque control mode adopts torque control based on a proportional differential (PD) algorithm of the robot's gravity torque.

[0020] Furthermore, in step S3, under the active buffering mechanism, the impact force of the collision is limited to a preset safety range.

[0021] Furthermore, the active buffering mechanism includes: the upper computer sends a torque command to make the motor reverse or reduce the output to achieve the purpose of deceleration, wherein the torque against the impact direction offsets the residual impact force and plays a buffering role.

[0022] Furthermore, in step S4, the robot executes torque mode control, continuously reading the current speed and torque feedback until the speed feedback is detected to be zero and the torque feedback is substantially unchanged, and the robot is determined to be stopped.

[0023] According to the safety control method for alternating position and torque in a human-machine collaborative collision scenario according to an embodiment of the present invention, an active protection strategy is adopted to greatly reduce transient impact force, and a buffering strategy is implemented by utilizing the high-bandwidth rapid response capability of servo control to minimize the damage caused by the collision, thereby improving the safety and performance of industrial robots when working in the same space with humans.

[0024] The safety control method for alternating position and torque in a human-machine collaborative collision scenario according to an embodiment of the present invention has the following beneficial effects:

[0025] (1) Compared with the industrial robot shutdown strategy without protection shutdown algorithm, the transient buffer torque is reduced by more than 10-30%;

[0026] (2) After the collision stops, the robot naturally separates from the contact surface, completely eliminating the steady-state extrusion force, making it easier for personnel to operate and troubleshoot, while protecting the tool and workpiece from secondary damage;

[0027] (3) The response to the impact is within 20ms, the impact force is released quickly and effectively, and there is no torque accumulation process that damages the robot joints;

[0028] (4) High versatility, suitable for all industrial machines and drive types.

[0029] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0031] Figure 1 Flowchart of a safety control method for alternating position and torque in a human-machine collaborative collision scenario according to an embodiment of the present invention;

[0032] Figure 2 Flowchart of a safety control method for alternating position and torque in a human-machine collaborative collision scenario according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0034] The present invention proposes a safety control method for alternating position and torque in a human-machine collaborative collision scenario, which implements active buffering protection for the robot and tool workpiece under extreme collision conditions.

[0035] like Figure 1 and Figure 2 As shown, the safety control method for alternating position and torque in a human-machine collaborative collision scenario according to an embodiment of the present invention includes the following steps:

[0036] Step S1: Under normal circumstances, the robot works in the position control mode to track the trajectory and continuously correct the position error.

[0037] Specifically, the basic control methods of robots are divided into two types: position control and torque control. Among them, position control sends position commands to servo motors, corrects position errors, and thus achieves movement to the desired position.

[0038] Step S2: Use sliding mode control algorithm to perform collision detection. When a collision signal is detected, it is determined that the robot has collided with the outside world.

[0039] Specifically, a sliding mode control algorithm is used for collision detection, including: using a sliding mode observer to predict the total external force applied to the robot during its dynamic process. Once the predicted external force exceeds a threshold, it is determined that a collision signal has been detected.

[0040] When a collision between the robot and the outside world is detected, the robot state data measured by the joints is recorded.

[0041] In an embodiment of the present invention, the robot state data includes: motor current torque, full speed, and servo state information. It should be noted that the robot state data is not limited to the above examples and may also include other data, which will not be repeated here.

[0042] Step S3: When a collision is detected in the robot, the robot switches to the torque control mode and starts the active buffering mechanism.

[0043] Specifically, the torque control mode uses a proportional derivative (PD) algorithm based on the robot's gravitational torque. Basic robot control methods are categorized as position control and torque control. Torque control issues torque commands to the servo motor, correcting for torque errors and performing tracking control to achieve the desired motor output and motion.

[0044] In addition, under the active buffering mechanism, the impact force of the collision is limited to a preset safety range.

[0045] The buffering mechanism uses a torque command from the upper computer to reverse the motor or reduce its output to achieve the purpose of deceleration; the torque against the impact direction offsets the residual impact force and acts as a buffer.

[0046] Step S4, detect whether the robot has stopped colliding. If it has not stopped, execute the torque mode, perform speed detection and torque detection, and start the protection mechanism; if it has stopped, execute step S5.

[0047] The robot executes torque mode control and continuously reads the current speed and torque feedback until the speed feedback is zero and the torque feedback is basically unchanged, and the robot is judged to have stopped.

[0048] Step S5: When the robot is separated from the impact surface, the robot automatically returns to the position control mode and waits.

[0049] In the embodiment of the present invention, during the process from step S1 to step S5, the joint torque is obtained by the current of the DC motor, and the speed and torque are monitored.

[0050] Specifically, to achieve optimal performance, the entire process monitors the DC motor's current to obtain joint torque, and monitors speed and torque. In engineering applications, various practical functions have been developed, including a downtime limit of less than 200ms, motor overload protection, and response to emergency stop signals.

[0051] The safety control method for alternating position and torque in a human-machine collaborative collision scenario according to an embodiment of the present invention involves a switching control method including two modes, one is a position control mode that uses a sliding mode control (SMC) algorithm for collision detection, and the other is a torque control mode based on a proportional differential (PD) algorithm of the robot's gravity torque. Under normal circumstances, the robot operates in the position control mode for trajectory tracking and continuously corrects position errors. Once the robot collides with the outside world, the robot will immediately switch to the torque control mode and limit the impact force to a safe range. When the robot is separated from the impact surface, the robot will automatically return to the position control mode.

[0052] The verification method and steps of the safety control method for alternating position and torque in a human-machine collaborative collision scenario according to an embodiment of the present invention in actual working conditions are as follows:

[0053] (1) The robot runs at a speed of v4000 or above and executes motion instructions;

[0054] (2) Place an immovable metal plate at the end of the trajectory, which is intended to be the impact plane;

[0055] (3) Normal robot load and no-load test collision;

[0056] (4) After the collision is triggered, the motor current torque, full-range speed, and servo status information measured by the joint are recorded.

[0057] The experimental results show that the safety control method of alternating position and torque in a human-machine collaborative collision scenario according to the embodiment of the present invention is effective and feasible.

[0058] According to the safety control method for alternating position and torque in a human-machine collaborative collision scenario according to an embodiment of the present invention, an active protection strategy is adopted to greatly reduce transient impact force, and a buffering strategy is implemented by utilizing the high-bandwidth rapid response capability of servo control to minimize the damage caused by the collision, thereby improving the safety and performance of industrial robots when working in the same space with humans.

[0059] The safety control method for alternating position and torque in a human-machine collaborative collision scenario according to an embodiment of the present invention has the following beneficial effects:

[0060] (1) Compared with the industrial robot shutdown strategy without protection shutdown algorithm, the transient buffer torque is reduced by more than 10-30%;

[0061] (2) After the collision stops, the robot naturally separates from the contact surface, completely eliminating the steady-state extrusion force, making it easier for personnel to operate and troubleshoot, while protecting the tool and workpiece from secondary damage;

[0062] (3) The response to the impact is within 20ms, the impact force is released quickly and effectively, and there is no torque accumulation process that damages the robot joints;

[0063] (4) High versatility, suitable for all industrial machines and drive types.

[0064] The safety control method for alternating position and torque in a human-robot collaborative collision scenario according to an embodiment of the present invention is suitable for various robot types, sizes, and dynamics, has no hardware limitations, and can be expanded to a variety of practical industrial scenarios.

[0065] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0066] Although the embodiments of the present invention have been shown and described above, it should be understood that the above embodiments are illustrative and are not to be construed as limiting the present invention. Those skilled in the art may make changes, modifications, substitutions, and variations to the above embodiments without departing from the principles and intent of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A safety control method for alternating position and torque in a human-machine collaborative collision scenario, characterized in that: The steps include: Step S1: Under normal circumstances, the robot works in the position control mode to track the trajectory and continuously correct the position error; Step S2: Using a sliding mode control algorithm to perform collision detection, when a collision signal is detected, it is determined that the robot has collided with the outside world; Step S3: When a collision is detected in the robot, the robot switches to a torque control mode and activates an active buffering mechanism; Step S4: Check whether the robot has stopped colliding. If it has not stopped, execute the torque mode, perform speed detection and torque detection, and activate the protection mechanism. If it has stopped, execute step S5. Step S5: When the robot is separated from the impact surface, the robot automatically returns to the position control mode and waits.

2. The method for alternating position and torque control in a human-machine collaborative collision scenario according to claim 1, characterized in that: During the process of step S1 to step S5, the joint torque is obtained by the current of the DC motor, and the speed and torque are monitored.

3. The method for alternating position and torque control in a human-machine collaborative collision scenario according to claim 1, characterized in that: In step S1 , the position control mode includes: issuing a position instruction to the servo motor and performing follow-up correction on the position error to achieve movement to a desired position.

4. The method for alternating position and torque safety control in a human-machine collaborative collision scenario according to claim 1, characterized in that: In step S2, the use of the sliding mode control algorithm for collision detection includes: predicting the total external force received by the robot during the dynamic process through a sliding mode observer, and once the predicted external force exceeds a threshold, it is determined that a collision signal is detected.

5. The method for safety control of alternating position and torque in a human-machine collaborative collision scenario according to claim 1, characterized in that: In step S2, when a collision between the robot and the outside world is detected, the robot state data measured by the joints is recorded.

6. The method for alternating position and torque safety control in a human-machine collaborative collision scenario according to claim 5, characterized in that: The robot status data includes: motor current torque, full-range speed, and servo status information.

7. The method for safety control of alternating position and torque in a human-machine collaborative collision scenario according to claim 1, characterized in that: In step S3, the torque control mode adopts a proportional differential algorithm based on the robot's gravity torque to perform torque control.

8. The method for safety control of alternating position and torque in a human-machine collaborative collision scenario according to claim 1, characterized in that: In step S3, under the active buffering mechanism, the impact force of the collision is limited to a preset safety range.

9. The method for safety control of alternating position and torque in a human-machine collaborative collision scenario according to claim 8, characterized in that: The active buffering mechanism includes: the upper computer sends a torque command to make the motor reverse or reduce the output to achieve the purpose of deceleration, wherein the torque against the impact direction offsets the residual impact force and plays a buffering role.

10. The method for safety control of alternating position and torque in a human-machine collaborative collision scenario according to claim 1, characterized in that: In step S4, the robot performs torque mode control and continuously reads the current speed and torque feedback until the speed feedback is detected to be zero and the torque feedback is substantially unchanged, and the robot is determined to be stopped.

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