Robot vibration suppression method based on intelligent slave station and acceleration feedback

Abstract

The invention provides a robot vibration suppression method based on an intelligent slave station and acceleration feedback, and belongs to the field of robot vibration suppression, and the method comprises the steps: designing two layers of EtherCAT communication, enabling a robot controller to serve as a master station of the first layer of EtherCAT communication, enabling the intelligent slave station to serve as a slave station of the first layer of EtherCAT communication, and enabling the intelligent slave station to serve as a master station of the second layer of EtherCAT communication, each servo motor is used as a slave station of the second layer of EtherCAT communication; the intelligent slave station carries a LINUX system, Beremiz software is installed in the LINUX system, and a calculation module is designed in the Beremiz software; voltage feedback signals collected by the acceleration sensors serve as input of the calculation module, the calculation module outputs initial rotation angles and rotation speeds of the two servo motors of the vibration suppression mechanisms of the joints, then the two servo motors generate resultant force on the corresponding joints to act on inertia force of the joints, and vibration suppression of the robot is achieved. Vibration of the robot can be suppressed in real time, the position control precision of the robot is improved, and the requirement for the computing power of a robot controller can be effectively lowered.

Description

Technical Field

[0001] The invention belongs to the field of robot vibration suppression, and in particular relates to a robot vibration suppression method based on an intelligent slave station and acceleration feedback. Background Art

[0002] In the prior art, a robot controller is used to control the robot. For the vibration suppression of the robot, it is generally carried out by establishing a complex dynamic model of a multi-joint robot, and the corresponding torque feedforward value is calculated based on the complex dynamic model to compensate the servo drive. However, this method uses the joint motor output control torque as the control input, that is, the joint motor is responsible for realizing rigid motion tracking and suppressing elastic vibration, which will undoubtedly cause a great burden on the mechanical structure at the joint. Furthermore, the dynamic model of the multi-joint robot has the characteristics of nonlinear strong coupling. On the one hand, the controller needs to control a large range of rigid body motion to achieve trajectory tracking, and on the other hand, it needs to suppress the elastic vibration of the arm in real time during the tracking process, and quickly suppress the residual vibration after the tracking is completed. This requires a high computing power of the controller, but considering the cost, applicability and other issues, the design of the controller is more difficult, and the robustness and real-time performance are also difficult to meet the requirements. Summary of the invention

[0003] The purpose of the present invention is to propose a robot vibration suppression method based on intelligent slave stations and acceleration feedback, which can realize real-time suppression of robot vibration by using intelligent slave stations, improve the position control accuracy of the robot, and effectively reduce the computing power requirements of the robot controller.

[0004] The present invention is achieved through the following technical solutions: A robot vibration suppression method based on intelligent slaves and acceleration feedback is provided. Acceleration sensors and vibration suppression mechanisms are installed on each joint of the robot. Each vibration suppression mechanism includes two servo motors and two exciters respectively arranged at the output ends of the two servo motors. The vibration suppression method includes the following steps: Step S1, designing two-layer EtherCAT communication, the robot controller serves as the master station of the first-layer EtherCAT communication, the intelligent slave station serves as the slave station of the first-layer EtherCAT communication and the master station of the second-layer EtherCAT communication, and each servo motor of each vibration suppression mechanism serves as the slave station of the second-layer EtherCAT communication; Step S2: The intelligent slave station is equipped with a LINUX system, the Beremiz software is installed in the LINUX system, and a calculation module is designed in the Beremiz software; Step S3, the voltage feedback signal collected by each acceleration sensor is used as the input of the calculation module, and the calculation module outputs the starting rotation angle and rotation speed of the two servo motors of the vibration suppression mechanism of each joint, so that the two servo motors drive the two exciters on the corresponding joints to generate a combined force acting on the inertia force of the joint to achieve vibration suppression of the robot.

[0005] Furthermore, the vibration exciter includes an eccentric mass.

[0006] Furthermore, in step S3, the calculation module uses the formula Calculate the rotation speed of the servo motor, where , T is the period of the voltage feedback signal.

[0007] Furthermore, in step S3, the rotation directions of the two servo motors are opposite, and the starting rotation angles of the two servo motors differ by π. The starting rotation angle of one servo motor is an angle at which the line L connecting the eccentric axis of the eccentric block and the axis of the servo motor is perpendicular to the plane P formed by the rotation axis of the joint and the arm of the joint.

[0008] Furthermore, the intelligent slave station includes an FPGA, a main control chip, and a link layer. The link layer is located in the FPGA. The main control chip accesses the link layer through a PCIe parallel bus. The link layer has a bidirectional data connection with the robot controller.

[0009] Furthermore, the intelligent slave station has no application layer protocol, nor a distributed clock function and an SDO function.

[0010] Furthermore, in step S2, the intelligent slave station is equipped with a LINUX system and runs a LINUX+Xenomai environment, and the Beremiz software provides a soft PLC secondary development programming platform compatible with the IEC61131 standard.

[0011] Furthermore, the robot has six joints.

[0012] Furthermore, in the first layer of EtherCAT communication, the acceleration sensors on the six joints are connected to the intelligent slave station using a serial bus, and in the second layer of EtherCAT communication, the intelligent slave station is connected to the two servo motors of each joint using a serial bus.

[0013] The present invention has the following beneficial effects: 1. In order to ensure the connection between each acceleration sensor and the servo motor of each vibration suppression mechanism and the intelligent slave station, so as to avoid all data having to pass through the robot controller, thereby effectively reducing the computing power requirements of the robot controller, the present invention designs two layers of EtherCAT communication, and uses the intelligent slave station as both a slave station of the first layer of EtherCAT communication and a master station of the second layer of EtherCAT communication, and arranges a computing module in the intelligent slave station. The voltage feedback signal collected by each acceleration sensor is used as the input of the computing module, and the computing module outputs the starting rotation angle and rotation speed of the servo motor of each joint, thereby generating an inertial force to achieve vibration suppression of the robot. This process is carried out in real time during the operation of the robot, thereby achieving real-time suppression of the vibration of the robot and improving the position control accuracy of the robot. On the other hand, the intelligent slave station of the present invention serves as a slave station of the upper network and as a master station of the lower network, so that it can expand and support more IO and AD / DA modules, enriching the peripheral capabilities of the intelligent slave station.

[0014] 2. The intelligent slave station of the present invention has the soft PLC programmable function in accordance with IEC61131-3, supports generating PLCopenXML files from Simulink models, and then importing them into the soft PLC project as function blocks. This fast model-to-code conversion method speeds up development efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention is further described in detail below with reference to the accompanying drawings.

[0016] Figure 1 It is a flow chart of the present invention.

[0017] Figure 2 It is a principle block diagram of the two-layer EtherCAT communication of the present invention.

[0018] Figure 3 It is a functional principle diagram of the intelligent slave station of the present invention.

[0019] Figure 4 Schematic diagram of input and output of the computing module of the present invention.

[0020] Figure 5 It is a schematic diagram of the installation of the acceleration sensor and the vibration suppression mechanism of the present invention.

[0021] Figure 6 This is the dual-machine vibration dynamics model of the present invention. DETAILED DESCRIPTION

[0022] like Figure 5As shown in FIG. 1 , the robot has six joints. Acceleration sensors and vibration suppression mechanisms are installed on each joint of the robot. Each vibration suppression mechanism includes two servo motors and two eccentric blocks respectively arranged at the output ends of the two servo motors. The two servo motors, the two eccentric blocks and the corresponding joints together constitute a dual-machine vibration system. Figure 1 As shown, the robot vibration suppression method based on intelligent slave station and acceleration feedback includes the following steps: Step S1, designing two-layer EtherCAT communication, the robot controller serves as the master station of the first-layer EtherCAT communication, the intelligent slave station serves as the slave station of the first-layer EtherCAT communication and the master station of the second-layer EtherCAT communication, and each servo motor of each vibration suppression mechanism serves as the slave station of the second-layer EtherCAT communication; Specifically, Figure 2 As shown, in the first layer of EtherCAT communication, the acceleration sensors on the six joints (the six joints are numbered as joint 1 to joint 6 from the robot base to the robot end) are connected to the intelligent slave station using a series bus, and the acceleration sensors of two adjacent joints are connected in series. In the second layer of EtherCAT communication, the intelligent slave station is connected to the two servo motors of each joint using a series bus, and the two servo motors of the same joint are connected in series, and the two servo motors of two adjacent joints are connected in series. like Figure 3 As shown, the intelligent slave station includes FPGA, main control chip, and link layer. The link layer is located in the FPGA. The main control chip accesses the link layer through the PCIe parallel bus. The link layer has a bidirectional data connection with the robot controller. The EtherCAT communication transmission cycle is 1ms. The intelligent slave station has no application layer protocol, nor does it have distributed clock function and SDO (service data object) function. It can only be used as an ordinary ECAT IO device; Step S2: The intelligent slave station is equipped with a LINUX system, the Beremiz software is installed in the LINUX system, and a calculation module is designed in the Beremiz software; More specifically, the intelligent slave station is equipped with the LINUX system and runs the LINUX+Xenomai environment. The Beremiz software provides a soft PLC secondary development programming platform compatible with the IEC61131 standard.

[0023] Step S3, the voltage feedback signal collected by each acceleration sensor is used as the input of the calculation module, and the calculation module outputs the starting rotation angle and rotation speed of the two servo motors of the vibration suppression mechanism of each joint, so that the two servo motors drive the two exciters on the corresponding joints to generate a combined force acting on the inertia force of the joint to achieve vibration suppression of the robot; More specifically, the accelerometer is used to measure the acceleration of an object. It senses the vibration force on the object and converts it into an electrical signal for measurement and analysis. Therefore, the signal fed back by the accelerometer to the controller is a voltage signal. The greater the voltage, the greater the vibration of the corresponding joint during the operation of the robot. Corresponding joint vibration acceleration The relationship is expressed as , k is the proportionality constant.

[0024] The robot controller is based on the formula Get the vibration frequency of the joint f , according to the formula Get the vibration frequency f The vibration amplitude under , according to the formula Get the vibration frequency f The vibration phase ,in, T The voltage signal collected by the acceleration sensor The cycle, , F {} indicates Fourier transform. This part is as follows Figure 3 As shown, Figure 3 middle, A The content indicated is , represents the amplitude; initial and x The angle between the axes is the initial phase; represents the phase, and correspond.

[0025] In order to suppress the vibration of the joint, the suppression frequency generated by the servo motor should be the same as the vibration frequency of the joint during processing. Therefore, the rotation speed of the two servo motors corresponding to the joint axis can be calculated based on the vibration suppression frequency. Figure 4 As shown, the calculation module is based on the formula Calculate the rotation speed of the servo motor, where , T is the period of the voltage feedback signal. Before the controller controls the servo motor to move for the first time, it determines the starting rotation angles of the two servo motors, where the starting rotation angle of one servo motor is the angle that makes the connecting line L Perpendicular to the plane P Angle, connection L The plane is the line connecting the eccentric shaft of the eccentric block and the axis of the servo motor. P It is the plane formed by the rotation axis of the joint and the arm of the joint. The arm of the joint refers to the rigid part connecting two adjacent rotation axes, such as Figure 5As shown. The starting rotation angle of the other servo motor differs from the starting rotation angle of the servo motor by π, and the starting rotation directions of the two servo motors are opposite. The starting vibration directions of the two servo motors are opposite to the vibration direction of the joint.

[0026] The robot controller can control the servo motor at any time, but in order to achieve better vibration suppression, the servo motor is controlled at the start-up time, which is the time when the amplitude of the vibration generated during the robot's operation is the largest. The amplitude can be divided into x , y , Three directions, such as Figure 6 As shown, the vibration displacements of the dual-machine vibration system in these three directions are ,in, , M represents the total weight of the two eccentric masses, m 1 and m 2 respectively represent the weight of the two eccentric blocks, k x , k y , The dual-machine vibration system is x , y , The spring stiffness in three directions, f x , f y , The dual-machine vibration system is x , y , Damping coefficients in three directions, l 0 represents the distance between the center of the machine body and the rotation center of the eccentric block. J is the equivalent moment of inertia of the dual-machine vibration system, l e is the equivalent rotation radius of the dual-machine vibration system, and In this embodiment, by observing the voltage signal fed back by the acceleration sensor, , the moments when the amplitudes of multiple vibrations are the largest can be determined, and one of the moments can be selected as the start moment.

[0027] In this embodiment, the robot is a multi-joint manipulator.

[0028] The robot controller controls the movement of the two servo motors. The servo motor drives the eccentric mass to rotate, generating inertial force during its rotation. The inertial forces generated by the two eccentric masses act on the joints, and the joints produce corresponding vibrations, thereby offsetting the joint vibrations caused by the robot's operation. Since the servo motor is fixed on the joints, changes in the joint vibrations will affect the rotation of the eccentric mass, which is reflected in the changes in the load torque of the servo motor. Changes in the load torque will also lead to changes in the output speed of the servo motor. Therefore, it is necessary to continuously control the servo motor to move at the current rotation speed based on the data detected by the acceleration sensor.

[0029] The above description is only a preferred embodiment of the present invention, and therefore cannot be used to limit the scope of implementation of the present invention. That is, equivalent changes and modifications made according to the scope of the patent application of the present invention and the contents of the specification should still fall within the scope covered by the patent of the present invention.

Claims

1. A robot vibration suppression method based on intelligent slave station and acceleration feedback, characterized in that: An acceleration sensor and a vibration suppression mechanism are installed on each joint of the robot. Each vibration suppression mechanism includes two servo motors and two exciters respectively arranged at the output ends of the two servo motors. The vibration suppression method includes the following steps: Step S1, designing two-layer EtherCAT communication, the robot controller serves as the master station of the first-layer EtherCAT communication, the intelligent slave station serves as the slave station of the first-layer EtherCAT communication and the master station of the second-layer EtherCAT communication, and each servo motor of each vibration suppression mechanism serves as the slave station of the second-layer EtherCAT communication; Step S2: The intelligent slave station is equipped with a LINUX system, the Beremiz software is installed in the LINUX system, and a calculation module is designed in the Beremiz software; Step S3, the voltage feedback signal collected by each acceleration sensor is used as the input of the calculation module, and the calculation module outputs the starting rotation angle and rotation speed of the two servo motors of the vibration suppression mechanism of each joint, so that the two servo motors drive the two exciters on the corresponding joints to generate a combined force acting on the inertia force of the joint to achieve vibration suppression of the robot.

2. The robot vibration suppression method based on intelligent slave station and acceleration feedback according to claim 1 is characterized in that: The vibration exciter includes an eccentric mass.

3. The robot vibration suppression method based on intelligent slave station and acceleration feedback according to claim 2 is characterized in that: In step S3, the calculation module uses the formula Calculate the rotation speed of the servo motor, where , T is the period of the voltage feedback signal.

4. The robot vibration suppression method based on intelligent slave station and acceleration feedback according to claim 1, 2 or 3, characterized in that: In step S3, the rotation directions of the two servo motors are opposite, and the starting rotation angles of the two servo motors differ by π. The starting rotation angle of one servo motor is the angle at which the line L connecting the eccentric axis of the eccentric block and the axis of the servo motor is perpendicular to the plane P formed by the rotation axis of the joint and the arm of the joint.

5. The robot vibration suppression method based on intelligent slave station and acceleration feedback according to claim 1, 2 or 3, characterized in that: The intelligent slave station includes an FPGA, a main control chip, and a link layer. The link layer is located in the FPGA. The main control chip accesses the link layer through a PCIe parallel bus. The link layer is bidirectionally connected to the robot controller.

6. The robot vibration suppression method based on intelligent slave station and acceleration feedback according to claim 1, 2 or 3, characterized in that: The intelligent slave station has no application layer protocol, nor distributed clock function and SDO function.

7. The robot vibration suppression method based on intelligent slave station and acceleration feedback according to claim 1, 2 or 3, characterized in that: In step S2, the intelligent slave station is equipped with a LINUX system and runs a LINUX+Xenomai environment, and the Beremiz software provides a soft PLC secondary development programming platform compatible with the IEC61131 standard.

8. The robot vibration suppression method based on intelligent slave station and acceleration feedback according to claim 1, 2 or 3, characterized in that: The robot has six joints.

9. The robot vibration suppression method based on intelligent slave station and acceleration feedback according to claim 7, characterized in that: In the first layer of EtherCAT communication, the acceleration sensors on the six joints are connected to the intelligent slave station using a serial bus, and in the second layer of EtherCAT communication, the intelligent slave station is connected to the two servo motors of each joint using a serial bus.

Images