Disturbance observer integrated with outer-loop for workspace, and robot including same

Abstract

Provided are a disturbance observer integrated with an outer-loop for a workspace, and a robot including same. The disturbance observer is implemented outside a position and velocity control loop within a workspace, and integrates a velocity command value, a velocity measurement value, an inverse model of a velocity control system, and a force / torque sensor (F / T sensor) measurement value to obtain a disturbance estimation value, wherein the disturbance estimation value is expressed by the following equation. D^v(s) is a disturbance estimation value, Q(s) is a Q filter, Dn(s) is a nominal model, Vm(s) is a velocity measurement value, Vi(s) is a velocity command value, A(s) is an admittance target value, and Fm(s) is a force measurement value.

Description

Workspace external loop integrated disturbance observer and robot including same

[0001] The present invention relates to a workspace external loop integrated disturbance observer and a robot including the same.

[0002] While admittance control can improve robot performance and robustness in human-robot interactive tasks, it has limitations in terms of stability when implemented on low-admittance hardware, such as industrial robots that perform position control. This instability arises from deviations from the ideal reference model, resulting from internal loop bandwidth, timing delays, or other model errors.

[0003] The problem to be solved by the present invention is to provide a workspace external loop integrated disturbance observer and a robot including the same that can improve contact stability and admittance rendering accuracy.

[0004] The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0005] In order to solve the above-described problem, a workspace external loop integrated disturbance observer according to one aspect of the present invention is implemented outside of a position and speed control loop within a workspace, and integrates a speed command, a speed measurement, an inverse model of a speed control system, and a force / torque sensor (F / T sensor) measurement to obtain a disturbance estimate, and the disturbance estimate is characterized by being expressed by the following mathematical equation.

[0006] [Mathematical formula]

[0007]

[0008] Above D v (s) is a disturbance estimate, the above Q(s) is a Q filter, and the above D n (s) is the nominal model, and the above V m(s) is the speed measurement, and the above V i (s) is the speed command, A(s) is the admittance target, and F m (s) is the force measurement

[0009] According to another aspect of the present invention for solving the above-described problem, a robot is provided, which controls position and velocity within a workspace, including a robot manipulator, an F / T sensor coupled to a tool end of the robot manipulator, and a robot controller connected to the F / T sensor and including a workspace external loop integrated disturbance observer, wherein the workspace external loop integrated disturbance observer is implemented outside of a position and velocity control loop within the workspace and integrates a velocity command, a velocity measurement, an inverse model of a velocity control system, and F / T sensor measurement to obtain a disturbance estimate, and the disturbance estimate is characterized in that it is expressed by the following mathematical equation.

[0010] [Mathematical formula]

[0011]

[0012] Above D v (s) is a disturbance estimate, the above Q(s) is a Q filter, and the above D n (s) is the nominal model, and the above V m (s) is the speed measurement, and the above V i (s) is the speed command, A(s) is the admittance target, and F m (s) is the force measurement

[0013] Other specific details of the present invention are included in the detailed description and drawings.

[0014] According to the present invention, a speed command value, a speed measurement value, an inverse model of a speed control system, and F / T sensor measurements can be integrated to estimate and remove disturbance.

[0015] According to the present invention, by improving the accuracy of rendering the admittance of the robot to user or environmental forces, the robot can be more easily operated, the contact force with the environment can be reduced, and vibration can be minimized.

[0016] According to the present invention, by implementing a disturbance observer outside the position and velocity control loop, the influence of the dynamics of the robot and payload and time delay within the workspace can be offset.

[0017] According to the present invention, contact stability can be significantly improved by suppressing high-frequency contact dynamics by utilizing F / T sensor measurements within a working space.

[0018] According to the present invention, an admittance control method of a simple structure can be implemented in an industrial robot to convert it into a collaborative robot.

[0019] The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.

[0020] FIG. 1 is a schematic diagram of an admittance control system including a workspace external loop integrated disturbance observer according to one embodiment of the present invention.

[0021] FIG. 2 is a schematic diagram of a robot including a workspace external loop integrated disturbance observer according to another embodiment of the present invention.

[0022] The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided solely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the present invention, and the present invention is defined solely by the scope of the claims.

[0023] The terminology used herein is for the purpose of describing embodiments only and is not intended to limit the present invention. In this specification, the singular also includes the plural unless specifically stated otherwise. As used herein, the terms "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components in addition to the mentioned components. Like reference numerals refer to like components throughout the specification, and "and / or" includes each and any combination of one or more of the mentioned components. Although "first", "second", etc. are used to describe various components, these components are not limited by these terms. These terms are only used to distinguish one component from another. Therefore, it should be understood that a first component mentioned below may also be a second component within the technical spirit of the present invention.

[0024] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in their common sense to those skilled in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0025] In describing the present invention, if it is judged that the detailed description of related known technology is obvious to a person skilled in the art and may unnecessarily obscure the gist of the present invention, it will be omitted.

[0026] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0027] In this specification, “dynamics” is used in place of a dynamic model, a dynamic model formula, or a simplified expression of a dynamic equation, an equation of motion, etc.

[0028] Robots must be able to safely render their dynamic range for physical interaction with the external environment or humans. Interaction control methods, such as impedance control or admittance control, control the robot's force and speed to respond to external forces or speeds, respectively.

[0029] Safety is crucial in interactive control. Unknown environmental dynamics interact with the robot, altering its dynamics and potentially causing vibrations or instability. Contact transitions or collisions can also induce transient, high forces. These stability issues become even more critical when the robot interacts with a rigid environment.

[0030] In many industrial applications, robot payloads include bulky or heavy objects, and in these cases, industrial robots offer higher payload capacities or reach. These interaction systems typically perform admittance control.

[0031] Meanwhile, a disturbance observer is used to suppress disturbances and effectively improve the internal control loop. A disturbance observer is a well-established method for suppressing the effects of disturbances.

[0032] FIG. 1 is a schematic diagram of an admittance control system including a workspace external loop integrated disturbance observer according to one embodiment of the present invention.

[0033] Referring to FIG. 1, the admittance control system (100) includes an internal position / velocity control loop (100) fixed for joint i.

[0034] The workspace external loop integrated disturbance observer (120) is implemented outside the position and velocity control loop (110) within the workspace.

[0035] The workspace external loop integrated disturbance observer obtains disturbance estimates by integrating speed command, speed measurements, an inverse model of the speed control system (or loop), and force / torque sensor (F / T sensor) measurements.

[0036] The above disturbance estimate can be expressed by the following mathematical expression 1.

[0037] [Mathematical Formula 1]

[0038]

[0039] Here, the above D^ v (s) is the disturbance estimate, Q(s) is the Q filter, and D n (s) is the nominal model, the above V m (s) is the speed measurement, V above i (s) is the speed command value, A(s) is the admittance target value, F m (s) represent the force measurements, respectively.

[0040] Here, 1-Q(s) provides a property that suppresses high-frequency vibrations due to contact dynamics, thereby improving overall contact stability. Multiplying by the admittance target value A(s) not only converts force into velocity, but also provides the additional benefit of generating force information for tracking the admittance target value.

[0041] In addition, the above speed command value is an auxiliary speed command value (V c) and may include the above external disturbance estimate.

[0042] In addition, the auxiliary speed command value is determined by the internal force reference value (F) by the admittance controller. r ) and the force values ​​including the above force measurements may be converted into speed.

[0043] Additionally, the nominal model is designed from internal velocity closed-loop dynamics and includes a payload suppression function, which can be expressed by the following mathematical expression 2.

[0044] [Equation 2]

[0045]

[0046] Here, the above R cn is the motor side nominal dynamics, the R dn is the robot nominal dynamics, the above P n Each represents the payload nominal dynamics.

[0047] In addition, the motor-side nominal dynamics can be expressed by the following mathematical expression 3.

[0048] [Equation 3]

[0049]

[0050] Here, the above k pn is the proportional coefficient, above k in Each represents an integration coefficient.

[0051] In addition, the robot nominal dynamics can be expressed by the following mathematical equation 4.

[0052] [Equation 4]

[0053]

[0054] Here, the above M r1 is the joint side mass, M r2 is the link side mass, B above r1 is the joint side damping coefficient, B r2 Each represents a link-side damping coefficient.

[0055] In addition, the nominal dynamics of the payload can be expressed by the following mathematical expression 5.

[0056] [Equation 5]

[0057]

[0058] Here, the above M pn is the payload mass, M a represent the admittance mass, respectively.

[0059] In addition, the above admittance target value can be expressed by the following mathematical expression 6.

[0060] [Equation 6]

[0061]

[0062] Here, the above M a is the admittance mass, B above a represent the admittance attenuation coefficients, respectively.

[0063] Additionally, in the system (100) illustrated in Fig. 1, the robot dynamics R d (s) can be interpreted as a linear two-mass system, and can be expressed in simplified form as the following mathematical expression 7.

[0064] [Equation 7]

[0065]

[0066] Here, the above R d1 (s) is the motor side dynamics, the R d2 (s) is the link side dynamics, the above K s (s) represents the joint flexibility dynamics.

[0067] Additionally, the F / T sensor and the external environment are modeled as stiff springs, and the payload is modeled as pure inertia, and can be expressed as in the following mathematical expression 8.

[0068] [Equation 8]

[0069]

[0070] Here, K f is the F / T sensor stiffness, K e is the external environment strength, M p represents the payload mass.

[0071] The basic admittance control of the system (100) illustrated in Fig. 1 is realized by external feedback of F / T sensor measurements.

[0072] An analog low-pass filter (LPF) within the F / T amplifier can be designed to have a cutoff frequency of a predetermined value to reduce force measurement delay.

[0073] External forces can physically affect the robot's dynamics, acting on the robot from the user (human), the environment, or a combination of these forces. These external forces are measured by force / torque (F / T) sensors.

[0074] External force F ext is the power of human beings F hum and the force F due to the environment env It consists of F r represents an internal force reference value. The error between the force reference value and the force measurement is input to the admittance controller to generate a speed command value.

[0075] Speed ​​command V i is a robot controller R c and robot dynamics R d is entered as .

[0076] According to the speed command, the robot moves at speed V and generates force F.

[0077] d v represents the disturbance input to the system, and T d represents the input time delay.

[0078] The internal workspace motion control loop can track the motion commands provided by the admittance controller.

[0079] Admittance control is realized with respect to the tool center point (TCP), which is a reference point that defines the position and orientation of the tool mounted on the robot.

[0080] The force measurements are converted into a frame (or coordinate system) defined by the tool center point, and the robot's motion commands are also made within that frame.

[0081] Although there are some unexplained details in relation to the system (100) illustrated in FIG. 1 to explain the gist of the present invention, the implementation process and operational effects thereof will be sufficiently understandable to those skilled in the art.

[0082] FIG. 2 is a schematic diagram of a robot including a workspace external loop integrated disturbance observer according to another embodiment of the present invention.

[0083] Referring to FIG. 2, the robot (200) includes a robot manipulator (210), an F / T sensor (220), a robot controller (not shown), and a payload or gripper system (230).

[0084] A robot (200) according to an embodiment of the present invention may be a robot that controls position and speed within a work space.

[0085] Although FIG. 2 illustrates a robot manipulator (210) having six degrees of freedom, the robot manipulator (210) is not limited thereto, and embodiments of the present invention can be implemented using various robot manipulators such as a horizontal or vertical multi-joint robot manipulator having any degrees of freedom, an orthogonal robot manipulator, a SCARA robot manipulator, a delta robot manipulator, etc.

[0086] The F / T sensor (220) is coupled to the tool end of the robot manipulator (210).

[0087] The robot controller is connected to an F / T sensor (220) and includes a workspace external loop integrated disturbance observer as described with reference to FIG. 1.

[0088] Depending on the application, a gripper or payload or gripper system (230) may be coupled to and secured to the F / T sensor (220).

[0089] According to the present invention, a speed command value, a speed measurement value, an inverse model of a speed control system, and F / T sensor measurements can be integrated to estimate and remove disturbance.

[0090] According to the present invention, by improving the accuracy of rendering the admittance of the robot to user or environmental forces, the robot can be more easily operated, the contact force with the environment can be reduced, and vibration can be minimized.

[0091] According to the present invention, by implementing a disturbance observer outside the position and velocity control loop, the influence of the dynamics of the robot and payload and time delay within the workspace can be offset.

[0092] According to the present invention, contact stability can be significantly improved by suppressing high-frequency contact dynamics by utilizing F / T sensor measurements within a working space.

[0093] According to the present invention, an admittance control method of a simple structure can be implemented in an industrial robot to convert it into a collaborative robot.

[0094] While the embodiments of the present invention have been described above with reference to the attached drawings, those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical concept or essential features thereof. Therefore, the embodiments described above should be understood to be illustrative in all respects and not restrictive.

Claims

1. Implemented outside the position and velocity control loop, within the workspace; The disturbance estimate is obtained by integrating the speed command, speed measurement, inverse model of the speed control system, and force / torque sensor (F / T sensor) measurements. A workspace external loop integrated disturbance observer, characterized in that the above disturbance estimate is expressed by the following mathematical expression 1. [Mathematical Formula 1] Above D^ v (s) is a disturbance estimate, the above Q(s) is a Q filter, and the above D n (s) is the nominal model, and the above V m (s) is the velocity measurement, and the above V i (s) is the speed command value, A(s) is the admittance target value, and F m (s) is the force measurement 2. In paragraph 1, The above speed command value is the auxiliary speed command value (V c ) and the above disturbance estimates, Workspace external loop integrated disturbance observer.

3. In paragraph 2, The above auxiliary speed command is an internal force reference value (F) by the admittance controller. r ) and the force value including the above force measurement value is converted into speed. Workspace external loop integrated disturbance observer.

4. In paragraph 1, The above nominal model is designed from internal velocity closed-loop dynamics and includes a payload suppression function, which is expressed by the following mathematical expression 2: Workspace external loop integrated disturbance observer. [Mathematical formula 2] Above R cn is the nominal dynamics on the motor side, and the above R dn is the robot nominal dynamics, and the above P n is the nominal payload dynamics 5. In paragraph 4, The above motor side nominal dynamics are expressed by the following mathematical expression 3: Workspace external loop integrated disturbance observer. [Mathematical Formula 3] above k pn is the proportional coefficient, and the above k in is the coefficient of integration 6. In paragraph 4, The above robot nominal dynamics is expressed by the following mathematical formula 4: Workspace external loop integrated disturbance observer. [Mathematical Formula 4] Above M r1 is the joint-side mass, and the above M r2 is the link side mass, and the B r1 is the joint-side damping coefficient, and the above B r2 is the link side attenuation coefficient 7. In paragraph 4, The above payload nominal dynamics are expressed by the following mathematical expression 5: Workspace external loop integrated disturbance observer. [Mathematical Formula 5] Above M pn is the payload mass, and the above M a is the admittance mass 8. In paragraph 1, The above admittance target value is expressed by the following mathematical formula 6: Workspace external loop integrated disturbance observer. Above M a is the admittance mass, and the above B a is the admittance attenuation coefficient 9. As a robot that controls position and speed within the work space, robot manipulator; A F / T sensor coupled to the tool end of the above robot manipulator; and A robot controller connected to the above F / T sensor and including a workspace external loop integrated disturbance observer, The above working space external loop integrated disturbance observer is, Implemented within the workspace, outside the position and velocity control loops, The disturbance estimate is obtained by integrating the speed command, speed measurement, inverse model of the speed control system, and force / torque sensor (F / T sensor) measurements. A robot characterized in that the above disturbance estimate is expressed by the following mathematical formula 7. [Mathematical formula 7] Above D^ v (s) is a disturbance estimate, the above Q(s) is a Q filter, and the above D n (s) is the nominal model, and the above V m (s) is the velocity measurement, and the above V i (s) is the speed command, Α(s) is the admittance target, and F m (s) is the force measurement

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