Robot hybrid impedance control method and system for curved surface workpiece grinding

Abstract

The invention discloses a robot mixed impedance control method and system for curved surface workpiece grinding, and belongs to the technical field of robot control, and the robot mixed impedance control method comprises the steps that a preset track of the tail end is generated according to an estimated geometric contour, and expected normal preset contact force is set for grinding; calculating an axial component force set value and a radial component force set value of the contact force in the preset track direction; calculating a force tracking error based on the measured value of the stress sensor, the axial component force set value and the radial component force set value, and further generating a force correction signal; scaling the force correction signal through an impedance factor, and superposing the force correction signal with a preset track to generate a correction track; based on the corrected track and the actual pose feedback, calculating a tail end motion correction amount; and through robot kinematics mapping and a driver, the tail end motion correction amount is converted into a torque instruction of a joint space and output for execution, constant-force grinding of the curved surface workpiece is achieved, and contact type machining operation can be stably and accurately completed.

Description

Technical Field

[0001] This invention relates to the field of robot control technology, and in particular to a hybrid impedance control method and system for grinding curved workpieces. Background Technology

[0002] In the manufacturing process of curved surfaces, grinding and polishing is a crucial but labor-intensive and environmentally challenging step. Prolonged exposure to dust from wood or metal can harm the health of operators, and the quality and efficiency of manual grinding are limited by the worker's experience and fatigue level. Therefore, automating this process is of significant practical importance.

[0003] The surface of the product blank is a non-uniform material, and its physical properties, such as hardness and texture, are unevenly distributed in space. In addition, each different workpiece has a unique curved surface geometry. These factors pose a severe challenge to the automated grinding of robots: not only is it necessary to accurately track complex spatial trajectories, but it is also necessary to maintain a constant contact force during the grinding process to ensure the uniformity of the grinding effect, while avoiding workpiece damage or tool wear due to improper force control.

[0004] Traditional robot position control cannot adapt to changes in workpiece surface geometry and differences in material properties, easily leading to unstable grinding forces or tool disengagement from the workpiece. Pure force control struggles to guarantee trajectory tracking accuracy. Therefore, a hybrid force / position control strategy is introduced. This strategy decomposes the task space into a position control subspace and a force control subspace using a selection matrix, allowing independent control within each subspace. Impedance control then achieves compliant interaction by adjusting the dynamic relationship (mass-damping-stiffness) between the robot's end effector and the environment.

[0005] In practical applications, robot dynamic parameters may change (e.g., when different end-effectors are installed), and the geometry and material properties of workpieces vary greatly. Fixed controller parameters cannot achieve optimal performance under all working conditions, limiting the system's capabilities and robustness. Therefore, there is an urgent need for a control method that can adapt online to changes in the robot's own dynamics and uncertainties in the working environment to improve the versatility, stability, and processing quality of robotic surface grinding systems. Summary of the Invention

[0006] This invention provides a robot hybrid impedance control method and system for grinding curved workpieces, in order to solve the technical problem of enabling robots to stably and accurately complete contact processing operations when facing complex curved surfaces with non-uniform materials and individual geometric differences.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] This invention provides a robot hybrid impedance control method for grinding curved workpieces, comprising:

[0009] Geometric estimation is performed on the curved workpiece to be polished to generate a preset trajectory;

[0010] Based on the polishing scenario, set the desired normal preset contact force;

[0011] The relative orientation of the grinding plane of the end effector and the surface of the curved workpiece is maintained at a preset angle; the axial component and radial component of the normal preset contact force in the preset trajectory direction are calculated based on the normal preset contact force and the preset angle.

[0012] The force tracking error is calculated based on the measured values ​​from the force sensor, the axial force setting value, and the radial force setting value.

[0013] A first-order filter is used to process the force tracking error and generate a force correction signal.

[0014] The force correction signal is scaled by an impedance factor and superimposed on the preset trajectory to generate a correction trajectory for the end effector.

[0015] Based on the corrected trajectory and the actual pose feedback, the proportional-derivative control algorithm is used to calculate the end motion correction amount;

[0016] By using robot kinematics mapping and actuators, the end effector motion correction is converted into torque commands in the joint space and output for execution, thereby achieving constant force grinding of the curved workpiece.

[0017] Furthermore, the geometric estimation of the curved workpiece to be polished and the generation of a preset trajectory include: planning a radial polishing path obtained by modeling the curved workpiece based on the estimated diameter and the estimated depth.

[0018] Furthermore, the preset angle is a constant angle determined based on ergonomics, and the axial force setting value and the radial force setting value are calculated based on the constant angle.

[0019] Furthermore, the transfer function of the first-order filter is a first-order FO filter.

[0020] Furthermore, the step of scaling the force correction signal using an impedance factor and superimposing it with the preset trajectory to generate a corrected trajectory for the end effector includes:

[0021] Set an impedance factor; divide the force correction signal by the impedance factor and add it to the preset trajectory to generate the corrected trajectory of the end effector; wherein the impedance factor is a positive scalar.

[0022] Furthermore, the calculation of force tracking error based on the measured value of the force sensor and the set values ​​of the axial force component and the radial force component also includes: ignoring force control in the direction of freedom perpendicular to the normal direction of the preset trajectory.

[0023] Furthermore, the proportional gain and derivative gain in the proportional-derivative control algorithm are tuned according to the stability requirements of the robot end effector when moving in free space.

[0024] The present invention also provides a robot hybrid impedance control system for grinding curved workpieces, characterized in that it includes:

[0025] Preset trajectory module: used to perform geometric estimation on the curved workpiece to be polished and generate a preset trajectory;

[0026] Force setting module: Used to set the desired normal preset contact force according to the grinding scenario;

[0027] Force calculation module: used to maintain the relative posture of the grinding plane of the end effector and the surface of the curved workpiece at a preset angle; calculates the axial component and radial component of the normal preset contact force in the preset trajectory direction based on the normal preset contact force and the preset angle;

[0028] First calculation module: used to calculate force tracking error based on the measured value of the force sensor, the axial force setting value, and the radial force setting value;

[0029] Correction module: used to process the force tracking error using a first-order filter and generate a force correction signal;

[0030] Corrected trajectory generation module: used to scale the force correction signal by an impedance factor and superimpose it with the preset trajectory to generate a corrected trajectory for the end effector;

[0031] The second calculation module is used to calculate the end motion correction amount based on the corrected trajectory and the actual pose feedback using a proportional-derivative control algorithm.

[0032] Output module: Used to convert the end effector motion correction into torque commands in the joint space through robot kinematic mapping and actuators, and output them for execution, so as to achieve constant force grinding of the curved workpiece.

[0033] Compared with the prior art, the technical solution disclosed in this invention has the following beneficial effects:

[0034] Compared with the prior art, this invention decomposes the constant normal contact force based on experience into the trajectory coordinate system according to the tool posture, and scales and compensates the output of the force control loop to the position setting value through an impedance factor, thereby realizing a "soft hybrid" of force control and position control. In particular, the force control loop uses a first-order filter to process the force sensor signal to suppress high-frequency noise and oscillations caused by discontinuous contact, thereby obtaining a smooth and stable force correction signal, thus achieving uniform grinding. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of a robot hybrid impedance control method for grinding curved workpieces, provided in an embodiment of the present invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] This specification describes an application scenario using a six-degree-of-freedom serial robot to automatically polish curved surfaces.

[0040] The system hardware configuration of a robot hybrid control system for grinding curved workpieces provided in the embodiments of this specification is as follows:

[0041] Robot body: It adopts a six-degree-of-freedom industrial robot arm.

[0042] End effector: Install a grinding machine, the main structure of which is a motor and abrasive.

[0043] Force sensing unit: A six-dimensional force / torque sensor is installed between the robot's end effector and the grinder to measure the contact force in the X, Y, and Z directions in real time.

[0044] Grinding workpiece and fixture: The workpiece to be ground is held on the worktable by a vacuum suction cup or fixing device.

[0045] Control hardware: Industrial PC / PLC, real-time controller, runs control algorithms, and communicates with robot drivers and force sensors via bus.

[0046] Specifically, the embodiments of this specification provide a robot hybrid impedance control method and system for grinding curved workpieces, which can solve the technical problem of robots being able to stably and accurately complete contact processing operations when facing complex curved surfaces with non-uniform materials and individual geometric differences.

[0047] like Figure 1 As shown in the embodiments of this specification, a robot hybrid impedance control method for grinding curved workpieces is provided, including:

[0048] S1: Perform geometric estimation on the curved workpiece to be polished and generate a preset trajectory.

[0049] S2: Set the desired normal preset contact force according to the polishing scenario.

[0050] In the embodiments of this specification, S1 and S2 include: based on the approximate diameter and roughness of the workpiece, roughly generating a radial grinding trajectory starting from one side of the workpiece and avoiding contact with the outer edge as a preset trajectory, and setting the required normal preset contact force. That is, based on the estimated diameter, roughness, and hardness of the workpiece, a preset end trajectory is generated. and normal force Specifically, a pose model based on the robot's base coordinate system is established based on the workpiece's geometric model, and the required end effector trajectory is planned according to the pose model and process requirements. Normal force The parameters are determined by multiple factors, including the workpiece material, grinding depth, grinding consumables, and grinding tool speed, and can be obtained through prior estimation. These two parameters serve as the expectations of the control system and are input into the system.

[0051] S3: Maintain the relative posture of the grinding plane of the end effector and the surface of the curved workpiece at a preset angle; calculate the axial component and radial component of the normal preset contact force in the preset trajectory direction based on the normal preset contact force and the preset angle.

[0052] In this embodiment of the specification, S3 includes: setting a constant angle between the grinding tool (such as a sander) and the workpiece surface according to ergonomics, and decomposing the normal contact force into axial and radial force components along a preset trajectory. Specifically, based on the preset grinding angle... The expected values ​​of the axial and radial components are calculated using formula (1). and Specifically, the preset grinding angle... The plane containing the grinding trajectory changes, and it is the angle between the workpiece surface normal and the grinding axis. It is assumed that the trajectory plane is in the XY plane.

[0053] The calculation formula is as follows:

[0054] (1)

[0055] in, This is the set value for the axial component force. The radial component force is set to a certain value. A contact force is preset for the normal direction. The preset angle is the angle between the grinding plane and the curved surface. Desired contact force Decomposition in all directions.

[0056] S4: Calculate the force tracking error based on the measured value of the force sensor, the set value of the axial force component, and the set value of the radial force component; S5: Process the force tracking error using a first-order filter to generate a force correction signal.

[0057] In the embodiments described in this specification, the force sensor reads the actual force. With set value Comparison, resulting in force tracking error The error is fed into a first-order filter ( Smoothing is performed to output a force correction signal. Specifically, the robot's end effector contact force signals are collected in real time during the interaction between the robot and the unknown environment. , calculated as actual grinding force As the raw observation data, it characterizes the actual force between the robot's end effector and the workpiece, forming the initial input to the force loop, and the controller for the force loop is designed. Specifically:

[0058] Force circuit input signal, i.e., force error signal The expression is:

[0059]

[0060] The force controller uses FO+PI to control the force expression as follows:

[0061]

[0062] in, The time constant is set after adjusting the oscillation characteristics of the control system. This indicates the proportional and derivative adjustment parameters of the force control loop.

[0063] S6: The force correction signal is scaled by an impedance factor and superimposed on the preset trajectory to generate a correction trajectory for the end effector.

[0064] In the embodiments described in this specification, the force correction signal is scaled by an adjustable impedance factor and then superimposed on the original preset trajectory to form the corrected target trajectory; a proportional-derivative (PD) position controller is used to calculate the motion commands required for the robot end effector to follow this corrected trajectory.

[0065] Specifically, the characteristics of the workpiece being ground are analyzed, and an impedance factor parameter corresponding to the environmental characteristics is selected as a hyperparameter for decoupling the force control loop and the position control loop, outputting a compensated trajectory with the impedance factor. The details are as follows:

[0066] S601 Analysis of Impedance Factor Based on Environmental Characteristics

[0067] The environment is central to any force control strategy. No matter how complex the algorithm, it cannot command a force when the end effector is in free space, nor can it command a motion when the end effector is fixed. The environment is typically modeled as a linear spring. Sometimes a damper is connected in parallel. Both are considered known and constant, and the law of force is chosen accordingly. This may be valid when a rigid tool contacts a compliant workpiece, but it is too simplistic to represent the entire environmental range.

[0068] We will describe the robot and environmental systems based on low-frequency behavior derived from impedance. For linear environments, impedance... Defined as the ratio of the Laplace transform of the force to the flow. For any given frequency This is a real part and the virtual part plural of:

[0069] (2)

[0070] when As the impedance approaches zero, the magnitude of the ambient impedance can fall into one of three categories: it can approach infinity, approach a non-zero finite number, or approach zero. The following definition is introduced:

[0071] 1) A system whose impedance is given by (2) is inertial if and only if The environment is a mass-spring system with impedance of... .

[0072] 2) A system whose impedance is given by (2) is resistive if and only if The environment is a compliant mass that slides on a viscous surface with impedance of .

[0073] 3) A system whose impedance is given by (2) is capacitive if and only if The environment is a damped, compliant surface with impedance of .

[0074] in, It is the environmental impedance, representing the characteristics of the workpiece; These are the impedance model parameters of a second-order mass-spring damped system. Represents the Laplace operator.

[0075] The above definition treats the environment (workpiece) interacting with the robot as an impedance model. The capacitive and inertial environments represent dual impedances, meaning that the inverse of a capacitive system is inertial, and the inverse of an inertial system is capacitive. The resistive environment is self-dual. When the robot grinds the workpiece, the environment is treated as an impedance environment. That is, the impedance factor mentioned above. .

[0076] S602 output trajectory with impedance factor correction

[0077] Select an appropriate impedance factor based on the workpiece material and control requirements. Output the target trajectory with impedance factor Calculation formula:

[0078]

[0079] S7: Based on the corrected trajectory and the actual pose feedback, the proportional-derivative control algorithm is used to calculate the end motion correction.

[0080] In this embodiment, S7 is implemented as follows: real-time acquisition of the robot's end-effector position signal during the robot's interaction with the unknown environment. The displacement signal in Cartesian space is obtained through transformation. , and This is used to characterize changes in the end position and forms the initial input for closed-loop feedback. Specifically:

[0081] S701 Cartesian space pose acquisition

[0082] The robot encoder collects the angles of each joint of the robot and converts them to Cartesian space for pose. With joint angle The mapping formula is:

[0083]

[0084] in, It is a vector of joint spatial position, velocity, and acceleration. It is a vector of pose, velocity, and acceleration in Cartesian space. Let be the positive kinematics matrix of the robot. It is a Jacobian matrix.

[0085] The S702 position control loop is controlled by a PD.

[0086] The position loop input signal is the difference between the compensated target trajectory and the actual trajectory. The expression is:

[0087]

[0088] The position controller uses a PD controller for end effector motion correction. :

[0089]

[0090] S8: Through robot kinematics mapping and actuators, the end effector motion correction is converted into torque commands in the joint space and output for execution, thereby achieving constant force grinding of the curved workpiece.

[0091] In the embodiments described in this specification, the aforementioned motion commands are converted into joint torques through the robot's inverse kinematics, driving the robot's movement. The robot's actual pose and contact force are sensed in real time, forming a closed-loop control. Specifically, After inverse kinematics is converted into joint angle commands, these commands are then converted into torques by robot joint actuators to drive robot motion, forming a closed loop. The robot's forward kinematics module provides the actual pose. .

[0092] The specific process is as follows:

[0093] S801 Establishing the Kinematic Equations of the Robot

[0094] Based on the Newton-Euler equations of motion, and considering factors such as friction coefficient and disturbance, the dynamic equations of a robot subjected to external forces are constructed as follows:

[0095]

[0096] in It is the mass matrix of the robotic arm. It is the motor inertia matrix. Here, B is the Coriolis and centrifugal force matrix, B is the viscous friction matrix, and G(q) is the gravity vector. This is the Coulomb friction matrix, where r is the gear ratio. It is the motor control signal vector. It is the scalar conversion coefficient from motor voltage to motor torque. It is the total joint torque. It is the force applied by the end effector (i.e., the sander).

[0097] In this invention, the inertia, viscous friction, and Coulomb friction of the motor are ignored, and its dynamic equation is expressed as:

[0098]

[0099] S802 transmits the motor joint torque to the controller.

[0100] Based on the Jacobian matrix, the end-motion correction amount is... Converted into joint torque This information is transmitted to the joints, forming a closed-loop control:

[0101]

[0102] Furthermore, the expected normal contact force and preset grinding angle Based on empirical data such as material, grinding depth, human and robot dynamics, adjustments can be made to suit workpieces of different shapes and materials in appropriate applications.

[0103] Furthermore, the decomposed expectations and the actual polishing power In actual algorithm design, when there is no force control in other dimensions, it needs to be filled to 0.

[0104] Furthermore, force controllers and position controllers employ filters and PID controllers, which introduce time delays in practical applications, potentially causing system instability. Different control frequencies require the selection of different time constants and PID parameters.

[0105] Furthermore, the impedance factor characterizes the compliance of the robot's end effector and also reflects the physical characteristics of the environment (workpiece) in which the robot interacts. Different impedance factors need to be selected based on different grinding forces, environmental conditions, and other application requirements.

[0106] Furthermore, the second-order mass-spring-damped system that determines the impedance factor simulates the environment as an impedance model, based on the stiffness of the environment. Damping To estimate the impedance factor.

[0107] Furthermore, the impedance factor is determined. When it approaches 0, it indicates that the environment (workpiece) is approaching an inertial environment, and the force adjustment is more accurate. When it approaches ∞, it indicates that the environment (workpiece) is approaching a capacitive environment, and the position adjustment is more accurate.

[0108] Furthermore, real-time acquisition of robot position signals The robot's end effector pose is obtained by acquiring encoders at each joint of the robot and then using forward kinematics.

[0109] Furthermore, the core of the robot hybrid impedance control method is to add the force setpoint in the force controller to the trajectory setpoint of the position through the impedance factor.

[0110] Furthermore, in practical applications of the present invention, the quality of the polishing process depends primarily on the adjustment of force, rather than the adjustment of position.

[0111] Geometric estimation is performed on the curved workpiece to be polished, and a preset trajectory is generated, including: planning a radial polishing path obtained from the modeling of the curved workpiece based on the estimated diameter and estimated depth. The preset trajectory includes the end position information corresponding to the radial polishing path. The preset trajectory planning is based on the final size of the workpiece as the modeling basis.

[0112] The preset included angle is a constant included angle determined based on ergonomics, and the axial force setting value and radial force setting value are calculated based on the constant included angle.

[0113] The transfer function of the first-order filter is that of a first-order FO filter. It can also be modified by various methods such as Butterworth filter and PI adjustment. The time constant of the first-order filter is determined by experimental debugging in order to achieve a balance between suppressing force signal jitter caused by workpiece surface inhomogeneity and tool vibration and ensuring system response speed.

[0114] The force correction signal is scaled by an impedance factor and superimposed on a preset trajectory to generate a corrected trajectory for the end effector. This process includes: setting the impedance factor; dividing the force correction signal by the impedance factor and adding it to the preset trajectory to generate the corrected trajectory for the end effector; where the impedance factor is a positive scalar. When the impedance factor is small, the trajectory correction caused by a unit force error is larger, and force control dominates; conversely, position tracking dominates. By adjusting this factor, it is possible to adapt to the process requirements of different stiffnesses or different grinding stages.

[0115] The force tracking error is calculated based on the measured values ​​of the force sensor and the set values ​​of the axial and radial force components. It also includes: ignoring force control in the direction of freedom perpendicular to the normal direction of the preset trajectory.

[0116] The proportional gain and derivative gain in the proportional-derivative control algorithm are tuned according to the stability requirements of the robot end effector when moving in free space.

[0117] Based on the same idea, this specification also provides a robot hybrid impedance control system for grinding curved workpieces, including:

[0118] Preset trajectory module: used to perform geometric estimation on the curved workpiece to be polished and generate a preset trajectory;

[0119] Force setting module: Used to set the desired normal preset contact force according to the grinding scenario;

[0120] Force calculation module: used to maintain the relative posture of the grinding plane of the end effector and the surface of the curved workpiece at a preset angle; calculates the axial component and radial component of the normal preset contact force in the preset trajectory direction based on the normal preset contact force and the preset angle.

[0121] First calculation module: used to calculate force tracking error based on the measured values ​​of the force sensor, the axial force setting value, and the radial force setting value;

[0122] Correction module: Used to process force tracking errors using a first-order filter and generate a force correction signal;

[0123] Corrected trajectory generation module: used to scale the force correction signal by impedance factor and superimpose it with the preset trajectory to generate the corrected trajectory of the end effector;

[0124] The second calculation module is used to calculate the end motion correction based on the corrected trajectory and actual pose feedback using a proportional-derivative control algorithm.

[0125] Output module: It is used to convert the end effector motion correction into torque commands in the joint space through robot kinematic mapping and actuators, and output them for execution, so as to achieve constant force grinding of curved workpieces.

[0126] The embodiments described in this specification demonstrate excellent performance in improving grinding quality and process robustness. By combining a hybrid impedance control framework with a first-order filter, the system can effectively maintain a constant normal contact force while tracking a preset trajectory. Its core lies in utilizing real-time feedback from a force sensor to dynamically adjust the weights of position and force control through impedance factors, enabling the controller to respond to environmental changes like a "spring-mass-damped" system. Even if there are localized hardness differences on the workpiece surface or minor deviations between the actual geometry and the model, the controller can automatically and smoothly adjust the robot's end effector position through force feedback to compensate for these errors, thereby ensuring the uniformity and consistency of grinding force and ultimately improving the quality of the finished product. This force-position sensing-based online trajectory correction capability is key to ensuring effective grinding of complex curved workpieces.

[0127] The embodiments described in this specification ensure the excellent stability of the entire control system. The introduction of a first-order filter is crucial, as it significantly smooths the measurement signal from the force sensor and effectively suppresses signal jitter and system oscillations caused by high-frequency electronic noise, discontinuities at the moment of contact, or vibrations of the grinding tool itself. By appropriately setting the filter's time constant, a balance can be achieved between noise suppression and maintaining system response speed, ensuring smooth output of control commands. This proactive signal processing mechanism, combined with the inherently good dynamic characteristics of impedance control, jointly guarantees the stable and reliable operation of the entire grinding process, avoiding processing defects or equipment damage caused by control instability.

[0128] The control scheme proposed in the embodiments of this specification has a clear structure and is easy to implement in engineering. The entire method adopts a modular design, clearly separating the trajectory planning, force calculation, hybrid impedance control, and filtering processes, with a clear logical hierarchy. The parameters involved, such as impedance factor, first-order filter time constant, and proportional and differential gain of the position loop PD controller, all have clear physical meanings, facilitating intuitive debugging and tuning by engineers based on specific robot dynamics characteristics, workpiece material, and process requirements. This design allows the technology to be relatively easily integrated into existing industrial robot control system platforms, accelerating the transformation from laboratory verification to industrial field application.

[0129] The embodiments described in this manual have significant ergonomic and social benefits. They completely liberate operators from high-risk, arduous, and health-damaging manual grinding operations. Workers are no longer exposed to dusty environments for extended periods and avoid musculoskeletal strain caused by repetitive labor, fundamentally improving working conditions and aligning with the trend of modern manufacturing towards automation, intelligence, and humanization.

[0130] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0131] The block diagrams of devices, apparatuses, devices, and systems involved in this invention are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0132] It should also be noted that in the apparatus, device, and method of the present invention, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered as equivalent solutions of the present invention.

[0133] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of the invention. Therefore, the invention is not intended to be limited to the aspects shown herein, but rather to be carried out within the widest scope consistent with the principles and novel features disclosed herein.

[0134] It should be understood that the qualifying terms "first", "second", "third", "fourth", "fifth" and "sixth" used in the description of the embodiments of the present invention are only used to more clearly illustrate the technical solutions and are not intended to limit the scope of protection of the present invention.

[0135] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of the invention to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations therein.

Claims

1. A robot hybrid impedance control method for grinding curved workpieces, characterized in that, include: Geometric estimation is performed on the curved workpiece to be polished to generate a preset trajectory; Based on the polishing scenario, set the desired normal preset contact force; The relative orientation of the grinding plane of the end effector and the surface of the curved workpiece is maintained at a preset angle; Based on the preset normal contact force and the preset included angle, calculate the axial component and radial component of the preset normal contact force along the preset trajectory direction. The force tracking error is calculated based on the measured values ​​from the force sensor, the axial force setting value, and the radial force setting value. A first-order filter is used to process the force tracking error and generate a force correction signal. The force correction signal is scaled by an impedance factor and superimposed on the preset trajectory to generate a correction trajectory for the end effector. Based on the corrected trajectory and the actual pose feedback, the proportional-derivative control algorithm is used to calculate the end motion correction amount; By using robot kinematics mapping and actuators, the end effector motion correction is converted into torque commands in the joint space and output for execution, thereby achieving constant force grinding of the curved workpiece.

2. The robot hybrid impedance control method for grinding curved workpieces according to claim 1, characterized in that, The step of geometrically estimating the curved workpiece to be polished and generating a preset trajectory includes: planning a radial polishing path obtained by modeling the curved workpiece based on the estimated diameter and the estimated depth.

3. The robot hybrid impedance control method for grinding curved workpieces according to claim 1, characterized in that, The preset angle is a constant angle determined based on ergonomics, and the axial force setting value and the radial force setting value are calculated based on the constant angle.

4. The robot hybrid impedance control method for grinding curved workpieces according to claim 1, characterized in that, The transfer function of the first-order filter is a first-order FO filter.

5. The robot hybrid impedance control method for grinding curved workpieces according to claim 1, characterized in that, The step of scaling the force correction signal using an impedance factor and superimposing it with the preset trajectory to generate a corrected trajectory for the end effector includes: Set an impedance factor; divide the force correction signal by the impedance factor and add it to the preset trajectory to generate the corrected trajectory of the end effector; wherein the impedance factor is a scalar.

6. The robot hybrid impedance control method for grinding curved workpieces according to claim 1, characterized in that, The calculation of force tracking error based on the force sensor measurement value and the axial force setting value and radial force setting value also includes: ignoring force control in the direction of freedom perpendicular to the normal direction of the preset trajectory.

7. The robot hybrid impedance control method for grinding curved workpieces according to claim 1, characterized in that, The proportional gain and derivative gain in the proportional-derivative control algorithm are tuned according to the stability requirements of the robot end effector when moving in free space.

8. A robot hybrid impedance control system for grinding curved workpieces, characterized in that, include: Preset trajectory module: used to perform geometric estimation on the curved workpiece to be polished and generate a preset trajectory; Force setting module: Used to set the desired normal preset contact force according to the grinding scenario; Force calculation module: used to maintain the relative orientation of the grinding plane of the end effector and the surface of the curved workpiece at a preset angle; Based on the preset normal contact force and the preset included angle, calculate the axial component and radial component of the preset normal contact force along the preset trajectory direction. First calculation module: used to calculate force tracking error based on the measured value of the force sensor, the axial force setting value, and the radial force setting value; Correction module: used to process the force tracking error using a first-order filter and generate a force correction signal; Corrected trajectory generation module: used to scale the force correction signal by an impedance factor and superimpose it with the preset trajectory to generate a corrected trajectory for the end effector; The second calculation module is used to calculate the end motion correction amount based on the corrected trajectory and the actual pose feedback using a proportional-derivative control algorithm. Output module: Used to convert the end effector motion correction into torque commands in the joint space through robot kinematic mapping and actuators, and output them for execution, so as to achieve constant force grinding of the curved workpiece.

Images