Force sensor decoupled end effector mechanism and variable impedance control method thereof

Abstract

The application discloses a kind of force sensor decoupling end effector mechanism and its variable impedance control method, mechanism includes: for being connected with robot sensor end, the sensor end includes: for being connected with robot force sensor and setting on the fixed platform of force sensor;With the mobile platform of the fixed platform sliding fit;Sliding mechanism is arranged between the fixed platform and mobile platform.Variable impedance control method includes: based on the designed end effector mechanism, by force sensor measured calculation end effector internal mechanical impedance and the reaction force of nonlinear force, this part of force is converted into current compensation input into the current loop control of linear motor, to realize the decoupling of mechanical impedance and nonlinear force;On the basis of above-mentioned decoupling, increase impedance controller in controller, combine the required stiffness and damping parameters, realize variable impedance control under different environmental stiffness.

Description

Technical Field

[0001] This invention relates to the fields of end effectors and automatic control, and in particular to an end effector mechanism with force sensor decoupling and its variable impedance control method. Background Technology

[0002] Traditional control strategies for industrial robot end effectors primarily focus on position control. However, an increasing number of unstructured environments require end effectors to perform contact operations with their surroundings, such as grinding, polishing, hole and shaft assembly, and gripping. While traditional high-rigidity position control can achieve precise positioning, it cannot meet the demands of some contact-based tasks. Due to the high rigidity of end effectors, significant impacts often occur when the end effector contacts the workpiece. Excessive vibration and impact can cause irreversible damage to both the workpiece and the actuator, potentially leading to equipment failure in severe cases.

[0003] The solution to the above problem is to reduce the stiffness of the end effector or increase its damping, so that the end effector exhibits a certain degree of compliance, thereby effectively reducing the impact between the end effector and the workpiece.

[0004] Existing research on resolving the above-mentioned issues mainly falls into two categories: structural design and control strategies. Regarding structural design, related research aims to alter stiffness and damping by designing different mechanisms. While this method can achieve changes in stiffness and damping, it is still influenced by the mechanical structure and lacks portability. As for control strategies, common approaches include using stiffness models to change stiffness by modifying their parameters. However, this method suffers from drawbacks such as insufficient variable stiffness range and low stiffness accuracy. Therefore, the proposed solution is to propose a force sensor-decoupled end effector mechanism and its variable impedance control method. Summary of the Invention

[0005] To address the problems in the prior art, this invention provides a force sensor decoupled end effector mechanism and its variable impedance control method. The impedance of the end effector can be controlled by changing the impedance controller parameters. By changing the impedance of the end effector mechanism, the impact between the end effector end and the workpiece during contact can be improved and reduced.

[0006] The technical solution adopted in this invention is:

[0007] An end effector mechanism decoupled from a force sensor, comprising:

[0008] A sensor terminal for connection to a robot, the sensor terminal including: a force sensor for connection to the robot and a fixed platform disposed on the force sensor;

[0009] A mobile platform that slides in conjunction with the fixed platform;

[0010] A sliding mechanism is provided between the fixed platform and the mobile platform.

[0011] The sliding mechanism specifically includes:

[0012] Linkages mounted on the fixed platform;

[0013] A slide rail is provided on the connecting rod;

[0014] A slider that mates with the slide rail;

[0015] The slider is connected to the mobile platform;

[0016] A drive mechanism that drives the slider to move linearly on the slide rail.

[0017] The drive mechanism is a linear motor.

[0018] The linear motor includes:

[0019] A linear motor stator is installed on the fixed platform;

[0020] A linear motor mover that is mounted on the mobile platform and engages with the linear motor stator.

[0021] A linear encoder is provided on the connecting rod, facing the linear motor actuator.

[0022] A further preferred embodiment is a force sensor decoupled end effector mechanism, comprising a linear motor, a fixed end, a moving end, and a linear encoder.

[0023] A linear motor provides a linear power source for the end effector, enabling the end effector to move. It consists of a stator and a mover.

[0024] The fixed end is equipped with a fixed platform, multiple connecting rods, a force sensor, and the stator of the linear motor;

[0025] The mobile terminal is equipped with a moving platform, multiple sliders, and the mover of the linear motor;

[0026] A linear encoder is mounted on the connecting rod and faces the linear motor mover to measure the relative displacement between the fixed end and the moving end.

[0027] A fixed platform is located at the fixed end of the end effector, with one side connected to the stator of the linear motor and the other fixed end connected to the force sensor.

[0028] The mobile platform is located at the moving end of the end effector to realize the movement of the end effector mechanism.

[0029] The connecting rod is provided with multiple suspensions on a fixed platform, and the guide rail is installed on the inner side.

[0030] The guide rail and slider guide the movement of the end effector. The guide rail is installed inside the connecting rod, and the slider is installed on the moving platform. Together with the guide rail, they guide the direction of movement and limit the stroke of the end effector.

[0031] The force sensor, which can be a strain gauge force sensor or a piezoelectric force sensor, has a single degree of freedom in the direction of motion of the end effector. It is installed on the fixed end of the fixed platform, and the other end of the force sensor is connected to the industrial robot.

[0032] Furthermore, the force sensor decoupled end effector mechanism is decoupled by measuring and calculating the mechanical impedance and nonlinear force of the force sensor decoupled end effector, thereby changing the input of the linear motor to achieve mechanical impedance decoupling of the force sensor decoupled end effector.

[0033] The mechanical impedance of an end effector includes its mechanical stiffness and its mechanical damping.

[0034] A variable impedance control method for a force sensor-decoupled end effector mechanism, employing the aforementioned force sensor-decoupled end effector mechanism, includes the following steps:

[0035] Step 1: Use a force sensor to directly measure and calculate the mechanical impedance and nonlinear force of the end effector mechanism decoupled from the force sensor;

[0036] Step 2: Based on the mechanical impedance and nonlinear force measured and calculated in Step 1, perform compensation and decoupling to obtain the decoupled end effector mechanism of the force sensor.

[0037] Step 3: Based on the decoupling of the force sensor in Step 2, add an impedance controller to the end effector mechanism. Use the current signal output by the impedance controller to perform variable impedance control on the end effector mechanism decoupled from the force sensor.

[0038] In step 1, the mechanical impedance and nonlinear force of the end effector mechanism decoupled from the force sensor are directly measured and calculated using a force sensor. Specifically, this includes:

[0039] Based on the interaction forces, the force measured by the force sensor includes mechanical impedance, nonlinear force, and the output force of the linear motor. The force measured by the force sensor is the current value after the change caused by the movement of the end effector due to the output force of the linear motor at the previous moment. Therefore, the specific expression of the force measured by the force sensor is as follows:

[0040] F s =Z z +F t-1 +F n

[0041] In the formula F s Z is the force measured by the force sensor. z The mechanical impedance of the end effector mechanism decoupled from the force sensor, F t-1 F is the output force of the linear motor at the previous moment. n Nonlinear force of the end effector mechanism decoupled from the force sensor;

[0042] The output force of the linear motor is calculated based on the force constant and input current of the linear motor. Therefore, the mechanical impedance and nonlinear force of the end effector mechanism decoupled from the force sensor are the force measured by the force sensor minus the output force of the linear motor. The specific expression is as follows:

[0043] Z z +F n =F s -i t-1 K i

[0044] In the formula i t-1 K represents the input current of the linear motor at the previous moment. i The force constant of a linear motor;

[0045] In step 2, compensation and decoupling are performed based on the mechanical impedance and nonlinear force measured and calculated in step 1 to obtain the decoupled end effector mechanism of the force sensor, specifically including:

[0046] The mechanical impedance and nonlinear force of the force sensor-decoupled end effector mechanism are converted into corresponding current through the force constant of a linear motor:

[0047]

[0048] In the formula i c The decoupling current is converted from mechanical impedance and nonlinear force;

[0049] The linear motor is placed in the current loop via a driver;

[0050] The decoupling current converted from mechanical impedance and nonlinear force is added to the input of the linear motor current loop. At this time, the input current of the linear motor includes the corresponding current converted from the mechanical impedance and nonlinear force of the force sensor decoupled end effector mechanism through the force constant of the linear motor, thus obtaining the decoupled force sensor decoupled end effector mechanism.

[0051] In step 3, an impedance controller is added to the end effector mechanism decoupled from the force sensor after decoupling in step 2. The current signal output by the impedance controller is used to provide variable impedance control to the end effector mechanism decoupled from the force sensor. Specifically, this includes:

[0052] The decoupled force sensor and the decoupled end effector mechanism are controlled by the current signal output by the impedance controller to achieve variable impedance control.

[0053] The parameters of an impedance controller include stiffness and damping;

[0054] Since stiffness is related to displacement and damping is related to velocity, the output current of the impedance controller is specifically:

[0055]

[0056] In the formula i i K is the output current of the impedance controller. d For the stiffness in the impedance controller parameters; B d The damping parameter is used in the impedance controller parameters; X is the relative displacement between the moving platform and the fixed platform. The relative speed between the mobile platform and the fixed platform;

[0057] The current signal output by the impedance controller is used to perform variable impedance control on the decoupled end effector mechanism of the force sensor. At this time, the input current of the linear motor includes the output current of the impedance controller and the mechanical impedance of the decoupled end effector mechanism of the force sensor, as well as the corresponding current converted by the nonlinear force through the force constant of the linear motor, thereby realizing the variable impedance control of the decoupled end effector mechanism of the force sensor.

[0058] A further preferred method for variable impedance control of a force sensor-decoupled end effector mechanism includes the following steps:

[0059] Step 1: Construct a physical model of the end effector to determine its mechanical impedance;

[0060] Step 2: Use a force sensor to directly measure and calculate the mechanical impedance and nonlinear force of the end effector;

[0061] Step 3: Compensate for the mechanical impedance and nonlinear force of the end effector measured and calculated in Step 2 to obtain the decoupled end effector;

[0062] Step 4: Based on the decoupled end effector in Step 3, add an impedance controller to realize variable impedance control of the end effector mechanism decoupled from the force sensor.

[0063] The physical model of the end effector and its mechanical impedance are constructed as follows:

[0064] The physical model of the end effector is a second-order system, and its model dynamic equations are as follows:

[0065]

[0066] Among them, K z For the mechanical stiffness of the end effector mechanism, B z For the mechanical damping of the end effector, M z Let X be the mass of the moving end of the end effector mechanism, and let X be the relative displacement between the moving end and the stationary end of the end effector. The relative speed between the moving end and the stationary end of the end effector; Let F be the relative acceleration between the moving and stationary ends of the end effector, and let F be the output force of the linear motor at the current moment. n Nonlinear forces in the end effector include frictional forces and other nonlinear forces.

[0067] Mechanical impedance is expressed as the product of stiffness and displacement, the product of damping and velocity, and the product of mass and acceleration. Based on the above end effector dynamic equations, the mechanical impedance of the end effector mechanism can be obtained as follows:

[0068]

[0069]

[0070] Among them, Z z Z represents the mechanical impedance of the end effector. m This refers to the inertia of the moving end of the end effector.

[0071] The mechanical impedance and nonlinear force of the end effector are directly measured and calculated using a force sensor. The specific method is as follows:

[0072] Based on the interaction forces, the forces acting on the fixed end of the end effector include mechanical resistance, the output force of the linear motor, and nonlinear forces, as expressed in the following expressions:

[0073] F g =Z z +F+F n (IV)

[0074] Among them, F g The force applied to the fixed end of the end effector.

[0075] A force sensor is installed on the fixed end of the end effector based on the force acting on it. One end of the force sensor is installed on the fixed end of the end effector, and the other end is installed on the industrial robot. The force, mechanical impedance, and nonlinear force measured by the force sensor are the forces resulting from the change in the end effector's movement caused by the output force of the linear motor at the previous moment. Therefore, the expression for the force measured by the force sensor is:

[0076] F s =Z z +F t-1 +F n (V)

[0077] In the formula F s F is the force measured by the force sensor. t-1 The force measured by the force sensor is equal to the force on the fixed end of the end effector, which is the output force of the linear motor at the previous moment.

[0078] The mechanical impedance and nonlinear force of the end effector measured by the force sensor are compensated to achieve decoupling of the mechanical impedance and nonlinear force of the end effector. The specific implementation method is as follows:

[0079] The linear motor of the end effector is placed in the current loop via a driver;

[0080] Based on the force constant of the linear motor and the input current of the linear motor current loop, the output force of the linear motor in the end effector at the current moment can be obtained as follows:

[0081] F = i t K i (VI)

[0082] In the formula i t K represents the current loop input current of the linear motor at the current moment. i The force constant of a linear motor;

[0083] Based on equations (V) and (VI), the mechanical impedance and nonlinear force at the current moment can be obtained:

[0084] Z z +F n =F s -i t-1 K i (VII)

[0085] In the formula i t-1 The input current of the current loop of the linear motor at the previous moment.

[0086] According to equation (VII) above, the mechanical impedance and nonlinear force of the end effector are converted into the corresponding current through the linear motor force constant:

[0087]

[0088] In the formula i c The decoupling current is the sum of the mechanical impedance and nonlinear force of the end effector at the current moment.

[0089] The decoupling current i is converted from the sum of the mechanical impedance and nonlinear force of the end effector at the current moment. c Adding this to the input current of the linear motor current loop, we can obtain the actual input current of the linear motor current loop after decoupling from mechanical impedance and nonlinear force:

[0090]

[0091] In the formula i t is the actual input current of the linear motor current loop at the current moment, and i is the controller output current;

[0092] At this time, the current input to the linear motor current loop includes the decoupling current converted from the sum of the controller output current, mechanical impedance, and nonlinear force, thus achieving decoupling of the mechanical impedance and nonlinear force of the end effector.

[0093] Add an impedance controller to achieve variable impedance control of the end effector based on force sensor measurement compensation. The specific method is as follows:

[0094] Since stiffness is related to displacement and damping is related to velocity, the output impedance of the impedance controller is:

[0095]

[0096] In the formula Z d K is the output impedance of the impedance controller. d Stiffness set for the impedance controller; B d Damping set for the impedance controller;

[0097] The current output by the impedance controller is:

[0098]

[0099] In the formula i i This is the current output by the impedance controller;

[0100] When the output current of the impedance controller is applied to the input of the linear motor current loop, the actual current input to the linear motor current loop is:

[0101] i t =id +i c +i i (XII)

[0102] In the formula i d This represents the desired current for the entire control loop.

[0103] At this time, the input current of the linear motor current loop includes the desired current of the entire control loop, the decoupling current converted from the sum of the mechanical impedance of the end effector and the nonlinear force, and the output current of the impedance controller.

[0104] This invention, based on a designed end effector mechanism, uses a force sensor to measure and calculate the reaction force of the internal mechanical impedance and nonlinear force of the end effector. This force is then converted into a current-compensated input to the current loop control of a linear motor, thereby decoupling the mechanical impedance and nonlinear force. Building upon this decoupling, an impedance controller is added to the controller. Finally, the required stiffness and damping parameters are set according to different needs to achieve variable impedance control under varying environmental stiffness. The aforementioned force sensor-decoupled end effector mechanism and variable impedance control method integrate a decoupled force sensor, enabling precise adjustment of the active compliance parameters of the end effector and achieving active variable impedance control.

[0105] Compared with the prior art, the present invention has the following advantages:

[0106] The force sensor decoupled end effector mechanism and its variable impedance control method of the present invention have the characteristics of simple structure. It can realize the change of stiffness and damping without changing the mechanical structure, and can realize arbitrary stiffness and damping control. It does not require the establishment of an accurate dynamic model of the end effector. The mechanical impedance of the end effector can be directly measured from the force sensor and its mechanical impedance can be decoupled. The impedance of the desired end effector can be directly set by setting the impedance controller, thereby realizing variable impedance control of the end effector. Attached Figure Description

[0107] Figure 1 This invention relates to an end effector mechanism for decoupling the force sensor.

[0108] Figure 2 This is a schematic diagram of the control architecture of the present invention;

[0109] Figure 3 This is a schematic flowchart of the force sensor decoupling end effector variable impedance control method of the present invention;

[0110] Figure 4 Fitting of the frequency domain dynamic response and dynamic characteristics of the end effector mechanism and its variable impedance method of the present invention;

[0111] Figure 5 The present invention provides the end effector mechanism and its variable impedance method of the present invention, and their frequency domain dynamic response and theoretical frequency domain dynamic response under virtual stiffness of 10000 N / m and virtual damping of 100 N*S / m.

[0112] Explanation of reference numerals in the attached drawings: 100-fixed end; 101-linear motor; 102-moving end; 1-force sensor; 2-fixed platform; 3-linear motor stator; 4-connecting rod; 5-linear motor mover; 6-linear encoder; 7-slider; 8-moving platform. Detailed Implementation

[0113] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Examples of these preferred embodiments are illustrated in the drawings. The embodiments of the present invention shown in and described with reference to the drawings are merely exemplary, and the present invention is not limited to these embodiments.

[0114] An end effector mechanism decoupled from a force sensor, such as Figure 1 As shown, it includes a linear motor 101, a fixed end 100, a moving end 102, and a linear encoder 6;

[0115] The linear motor 101 provides a linear power source for the end effector, enabling the end effector to move. It includes a linear motor stator 3 and a linear motor mover 5.

[0116] The fixed end 100 is provided with a fixed platform 2, multiple connecting rods 4, a force sensor 1, and the linear motor stator 3;

[0117] The mobile terminal 102 is equipped with a mobile platform 8, multiple sliders 7 and the linear motor actuator 5;

[0118] The linear encoder 6 is mounted on the connecting rod 4 by screws and faces the linear motor mover 5, and is used to measure the relative displacement between the fixed end 100 and the moving end 102.

[0119] The fixed platform 2 is located at the fixed end 100 of the end effector. One side of the platform is connected to the linear motor stator 3 with screws, and the other side is connected to the force sensor 1 with screws.

[0120] Mobile platform 8 serves as the moving end of the end effector, enabling the movement of the end effector mechanism;

[0121] Link 4 is mounted with screws and suspended from fixed platform 2, and has guide rails on its inner side;

[0122] The slider 7 is mounted on the moving platform by screws and, together with the inner guide rail of the connecting rod 4, guides the movement of the end effector and limits the stroke of the end effector.

[0123] Force sensor 1, which can be a strain gauge force sensor or a piezoelectric force sensor, etc., has a single degree of freedom in the direction of motion of the end effector. It is installed on the fixed side of the fixed platform 2 by screws, and the other end of force sensor 1 is connected to the industrial robot.

[0124] Furthermore, the end effector mechanism decoupled from force sensor 1 is decoupled by measuring and calculating the mechanical impedance and nonlinear force of the end effector decoupled from force sensor 1, thereby changing the input of linear motor 101 to achieve mechanical impedance decoupling of the end effector decoupled from force sensor 1.

[0125] The mechanical impedance of an end effector includes its mechanical stiffness and its mechanical damping.

[0126] A variable impedance control method for a force sensor-1 decoupled end effector mechanism, the entire control architecture as follows: Figure 2 As shown, it includes the following steps:

[0127] Step 1: Construct a physical model of the end effector to determine its mechanical impedance;

[0128] Step 2: Use force sensor 1 to directly measure and calculate the mechanical impedance and nonlinear force of the end effector;

[0129] Step 3: Compensate for the mechanical impedance and nonlinear force of the end effector measured and calculated in Step 2 to obtain the decoupled end effector;

[0130] Step 4: Based on the decoupled end effector in Step 3, add an impedance controller to realize variable impedance control of the end effector mechanism decoupled from the force sensor.

[0131] The physical model of the end effector and its mechanical impedance are constructed as follows:

[0132] The physical model of the end effector is a second-order system, and its model dynamic equations are as follows:

[0133]

[0134] Among them, K z For the mechanical stiffness of the end effector, B z For the mechanical damping of the end effector, M z Let X be the mass of the moving end 102 of the end effector, and let X be the relative displacement between the moving end 102 and the fixed end 100 of the end effector. It is the relative speed between the mobile terminal 102 and the fixed terminal 100; F is the relative acceleration between the mobile end 102 and the fixed end 100, and F is the output force of the linear motor 101 of the end effector at the current moment. n Nonlinear forces in the end effector mechanism, including nonlinear forces such as friction;

[0135] Mechanical impedance is expressed as the product of stiffness and displacement, the product of damping and velocity, and the product of mass and acceleration. Based on the aforementioned end effector dynamics equations, the mechanical impedance of the end effector can be obtained as follows:

[0136]

[0137]

[0138] Among them, Z z Z represents the mechanical impedance of the end effector. m The inertia of the moving end of the end effector;

[0139] The mechanical impedance and nonlinear force of the end effector are directly measured and calculated using force sensor 1. The specific method is as follows:

[0140] Based on the interaction forces, the forces acting on the fixed end 100 of the end effector include mechanical resistance, the output force of the linear motor 101, and nonlinear forces, as specifically expressed below:

[0141] F g =Z z +F+F n (IV)

[0142] Among them, F g The force is applied to the fixed end 100 of the end effector.

[0143] Force sensor 1 is installed on the fixed end 100 of the end effector based on the force acting on it. One end of force sensor 1 is installed on the fixed end 100 of the end effector, and the other end is installed on the industrial robot. The force, mechanical impedance, and nonlinear force measured by force sensor 1 are the forces resulting from the change in the end effector's movement caused by the output force of the linear motor 101 at the previous moment. Therefore, the expression for the force measured by force sensor is:

[0144] F s =Z z +F t-1 +F n (V)

[0145] In the formula F s F is the force measured by force sensor 1. t-1 The force measured by the force sensor 1 is equal to the force on the fixed end 100 of the end effector, which is the output force of the linear motor 101 at the previous moment.

[0146] The mechanical impedance and nonlinear force of the end effector measured by force sensor 1 are compensated to achieve decoupling of the mechanical impedance and nonlinear force of the end effector. The specific implementation method is as follows:

[0147] The linear motor 101 of the end effector is placed in the current loop via a driver;

[0148] Based on the force constant of the linear motor 101 and the input current of the current loop of the linear motor 101, the output force of the end effector linear motor 101 at the current moment can be obtained as follows:

[0149] F = i t K i (VI)

[0150] In the formula i t K is the input current of the current loop of the linear motor 101 at the current moment. i The force constant is 101 for a linear motor;

[0151] Based on equations (V) and (VI), the mechanical impedance and nonlinear force at the current moment can be obtained:

[0152] Z z +F n =F s -i t-1 K i (VII)

[0153] In the formula i t-1 The input current of the current loop of the linear motor 101 at the previous moment.

[0154] According to equation (VII) above, the mechanical impedance and nonlinear force of the end effector are converted into corresponding currents through the force constant of the linear motor 101:

[0155]

[0156] In the formula i c The decoupling current is the sum of the mechanical impedance and nonlinear force of the end effector at the current moment.

[0157] The decoupling current i is converted from the sum of the mechanical impedance and nonlinear force of the end effector at the current moment. c Adding this to the input current of the linear motor 101 current loop, we can obtain the actual input current of the linear motor current loop after decoupling from mechanical impedance and nonlinear force:

[0158]

[0159] In the formula i ti represents the actual input current of the current loop of linear motor 101 at the current moment, and i represents the output current of the controller.

[0160] At this time, the current input to the current loop of the linear motor 101 includes the decoupling current converted from the sum of the controller output current, mechanical impedance, and nonlinear force, thus achieving decoupling of the mechanical impedance and nonlinear force of the end effector.

[0161] Add an impedance controller to achieve variable impedance control of the end effector based on force sensor 1 measurement compensation. The specific method is as follows:

[0162] Since stiffness is related to displacement and damping is related to velocity, the output impedance of the impedance controller is:

[0163]

[0164] In the formula Z d K is the output impedance of the impedance controller. d Stiffness set for the impedance controller; B d Damping set for the impedance controller;

[0165] The current output by the impedance controller is:

[0166]

[0167] In the formula i i This is the current output by the impedance controller;

[0168] When the output current of the impedance controller is applied to the input of the current loop of the linear motor 101, the actual current input to the current loop of the linear motor 101 is:

[0169] i t =i d +i c +i i (XII)

[0170] In the formula i d This represents the desired current for the entire control loop.

[0171] At this time, the input current of the linear motor 101 current loop includes the desired current of the entire control loop, the decoupling current converted from the sum of the mechanical impedance of the end effector and the nonlinear force, and the output current of the impedance controller.

[0172] To illustrate the advantages of this invention, since it controls the stiffness and damping of the end effector mechanism, and the end effector is a second-order spring-mass-damped system, this example uses frequency domain analysis to experimentally verify the invention by decoupling the force sensor 1 from the end effector mechanism and its variable impedance control method. Figure 4 and Figure 5 As shown. In the experiment, the current is input to the control system through a linear motor 101, and the output is the relative position measured by the encoder. Based on... Figure 4 The parameters of the end effector mechanism of the machine are identified, and its dynamic response is obtained through frequency domain fitting, thus obtaining its transfer function. Based on the transfer function of the mechanical system, the impedance controller parameters are modified to derive the theoretical transfer function using the method of this invention, and parameter identification is performed again. Figure 5 As can be seen from this, the decoupled end effector mechanism of force sensor 1 and its variable impedance control method realize the change of stiffness and damping of the end effector, and can obtain its relatively accurate theoretical frequency domain dynamic response.

Claims

1. A variable impedance control method for an end effector mechanism decoupled from a force sensor, characterized in that, An end effector mechanism employing force sensor decoupling includes: A sensor terminal for connection to a robot, the sensor terminal including: a force sensor for connection to the robot and a fixed platform disposed on the force sensor; A mobile platform that slides in conjunction with the fixed platform; A sliding mechanism is provided between the fixed platform and the mobile platform; The method includes the following steps: Step 1: Directly measure and calculate the mechanical impedance and nonlinear force of the end effector mechanism decoupled from the force sensor using a force sensor. Specifically, this includes: Based on the interaction forces, the force measured by the force sensor includes mechanical impedance, nonlinear force, and the output force of the linear motor. The force measured by the force sensor is the current value after the change caused by the movement of the end effector due to the output force of the linear motor at the previous moment. Therefore, the specific expression of the force measured by the force sensor is as follows: In the formula The force measured by the force sensor. Mechanical impedance of the end effector mechanism decoupled from the force sensor This represents the output force of the linear motor at the previous moment. Nonlinear force of the end effector mechanism decoupled from the force sensor; The output force of the linear motor is calculated based on the force constant and input current of the linear motor. Therefore, the mechanical impedance and nonlinear force of the end effector mechanism decoupled from the force sensor are the force measured by the force sensor minus the output force of the linear motor. The specific expression is as follows: In the formula This represents the input current of the linear motor at the previous moment. The force constant of a linear motor; Step 2: Based on the mechanical impedance and nonlinear force measured and calculated in Step 1, perform compensation and decoupling to obtain the decoupled end effector mechanism of the force sensor, specifically including: The mechanical impedance and nonlinear force of the force sensor-decoupled end effector mechanism are converted into corresponding current through the force constant of a linear motor: In the formula The decoupling current is converted from mechanical impedance and nonlinear force; The linear motor is placed in the current loop via a driver; The decoupling current converted from mechanical impedance and nonlinear force is added to the input of the linear motor current loop. At this time, the input current of the linear motor includes the corresponding current converted from the mechanical impedance and nonlinear force of the force sensor decoupled end effector mechanism through the force constant of the linear motor, thus obtaining the decoupled force sensor decoupled end effector mechanism. Step 3: Based on the decoupling of the force sensor in Step 2, add an impedance controller to the end effector mechanism. Use the current signal output by the impedance controller to perform variable impedance control on the end effector mechanism decoupled from the force sensor.

2. The variable impedance control method for the force sensor-decoupled end effector mechanism according to claim 1, characterized in that, The sliding mechanism specifically includes: Linkages mounted on the fixed platform; A slide rail is provided on the connecting rod; A slider that mates with the slide rail; The slider is connected to the mobile platform; A drive mechanism that drives the slider to move linearly on the slide rail.

3. The variable impedance control method for the force sensor-decoupled end effector mechanism according to claim 2, characterized in that, The drive mechanism is a linear motor.

4. The variable impedance control method for the force sensor-decoupled end effector mechanism according to claim 3, characterized in that, The linear motor includes: A linear motor stator is installed on the fixed platform; A linear motor mover that is mounted on the mobile platform and engages with the linear motor stator.

5. The variable impedance control method for the force sensor-decoupled end effector mechanism according to claim 4, characterized in that, A linear encoder is provided on the connecting rod, facing the linear motor actuator.

6. The variable impedance control method for the force sensor-decoupled end effector mechanism according to claim 1, characterized in that, In step 3, based on the decoupling of the force sensor in step 2, an impedance controller is added to the end effector mechanism. The current signal output by the impedance controller is used to provide variable impedance control to the end effector mechanism decoupled from the force sensor. Specifically, this includes: The decoupled force sensor and the decoupled end effector mechanism are controlled by the current signal output by the impedance controller to achieve variable impedance control. The parameters of an impedance controller include stiffness and damping; Since stiffness is related to displacement and damping is related to velocity, the output current of the impedance controller is specifically: In the formula This refers to the output current of the impedance controller. Stiffness is a parameter in the impedance controller. Damping is a parameter in the impedance controller. This refers to the relative displacement between the mobile platform and the fixed platform. The relative speed between the mobile platform and the fixed platform; The current signal output by the impedance controller is used to perform variable impedance control on the decoupled end effector mechanism of the force sensor. At this time, the input current of the linear motor includes the output current of the impedance controller and the mechanical impedance of the decoupled end effector mechanism of the force sensor, as well as the corresponding current converted by the nonlinear force through the force constant of the linear motor, thereby realizing the variable impedance control of the decoupled end effector mechanism of the force sensor.

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