Force feedback device and method for assisting clamping operation of surgical robot

Abstract

The invention discloses a force feedback device and method for assisting a surgical robot in clamping operation, and belongs to the technical field of VR force feedback and machinery. The device comprises a variable stiffness mechanism, a blocking structure, a ratchet clutch structure, a holding mechanism, a measuring unit, a control processing unit and a power supply module. The effective length of the lever arm between the elastic element and the feedback force output position is changed through the variable stiffness mechanism, and then the stiffness of the force feedback device is adjusted. The blocking mechanism achieves rendering of infinite stiffness by limiting grip by an operator. And the mode switching between zero rigidity and rigidity rendering can be realized through the engagement and disengagement of the ratchet wheel clutch structure clamping jaw and the ratchet wheel. Therefore, the force feedback device can realize real physical stiffness feedback in a range from zero impedance to theoretically infinite. In surgical training or other tasks, the force information in interaction between the hand of the user and the virtual object is provided to the user as truthful, and the property of the elastic element makes the invention safer.

Description

Technical Field

[0001] The present invention belongs to the field of VR force feedback and mechanical technology, and specifically relates to a force feedback device and method for assisting a surgical robot in clamping operations. Background Art

[0002] The application of virtual reality (VR) technology in the medical field has made significant progress, especially in surgical training, rehabilitation therapy and telemedicine. As a key component to enhance the immersion of virtual environments, force feedback technology can help doctors and patients obtain more physical perception information in virtual environments, greatly improving the accuracy and safety of medical operations. In surgical training, force feedback devices can simulate the force sense and feedback resistance of actual surgical operations, helping surgeons and medical students to practice operations in virtual environments. By providing feedback of different hardness and elasticity, doctors can perceive the characteristics of different tissues such as skin, muscle, and bone during training, thereby improving the accuracy and safety of operations. In rehabilitation therapy, force feedback technology can be used to simulate various movements and forces in physical therapy, helping patients to perform restorative exercises through virtual devices, and improve joint mobility and muscle strength. Through adjustable feedback force, patients can gradually adapt to training from mild to greater force, promoting the rehabilitation process. In addition, in telemedicine, force feedback devices can help doctors remotely operate robotic arms or other medical equipment for precise surgery or treatment. Due to the lack of force information, traditional remote operations have high risks. The introduction of force feedback technology can provide more accurate operation perception. Although current force feedback technology has great potential in the medical field, existing devices still face many challenges, especially in terms of accuracy, flexibility, and adaptability.

[0003] Existing force feedback devices are mainly divided into three categories: active force feedback devices, passive force feedback devices and hybrid drive force feedback devices.

[0004] Active force feedback devices include impedance-type and admittance-type devices, which use active drive methods such as motors and pneumatic actuators to generate feedback force and can usually provide more accurate force feedback. Impedance-type devices provide feedback through a reverse-driven motor, and users can sense the device's response, but their feedback force is weak and cannot simulate complex physical force sensations, such as the stretching or compression of elastic objects. Admittance-type devices provide a large output force through a high-reduction ratio motor and force sensor, which is suitable for simulating the feedback of rigid objects. However, these devices are usually bulky and power-hungry, and are difficult to miniaturize and achieve high efficiency, especially in handheld devices, which limits their feasibility for long-term use in medical training.

[0005] Unlike active force feedback devices that rely on motors to generate feedback force, passive force feedback devices provide feedback force through physical mechanisms such as springs. They are usually lightweight, low power, and suitable for simulating the contact of hard objects. Some existing devices often provide feedback force through mechanical structures, which can simulate strong resistance and are suitable for simulating the contact of hard objects. However, they cannot simulate the interaction of elastic or soft objects and lack the ability to provide feedback for flexible objects. At the same time, these devices have poor flexibility and cannot meet complex interaction requirements, limiting their application in scenarios that require delicate operations.

[0006] Hybrid drive force feedback devices combine active and passive drives, hoping to take advantage of each other and provide a possibility for production use in medical treatment. Some existing works combine magnetorheological brakes and motors to achieve feedback by adjusting friction and force output, which can provide large output force and maintain low weight.

[0007] The present application is different from the prior art as follows:

[0008] Technical comparison with patent CN114452640A "A VR force feedback device for sensing the physical properties of virtual objects"

[0009] In patent CN114452640A, the feedback force includes the simulated instantaneous impact force generated by the thumb servo and index finger servo, the elastic force generated by the spring ratchet and torsion spring, and the friction force generated by the interlaced servo and nut. In order to ensure the safe operation of the auxiliary surgical robot during clamping, we designed a hybrid drive handheld force feedback device with a spring lever mechanism. The output force comes entirely from the elastic force generated by the spring deformation.

[0010] In patent CN114452640A, the ratchet teeth clamp the spring ratchet wheel, so that the user cannot perform the inward pinching movement. However, we adopt a solution in which the ratchet wheel is equipped with a baffle and the brake is fixed on the spring carrier to form a blocking mechanism to limit the user's gripping movement. Summary of the invention

[0011] In order to solve the above technical problems, the present invention proposes a force feedback device and method for assisting the clamping operation of a surgical robot. The structure is a hybrid drive handheld force feedback device based on the combined action of a spring lever mechanism, which is called a semi-active handheld controller. While overcoming the existing problems, the effective length of the lever arm between the elastic element and the feedback force output position is changed by a variable stiffness mechanism, thereby realizing the adjustment of the stiffness of the force feedback device; the blocking mechanism realizes the rendering of infinite stiffness by limiting the gripping movement; on the other hand, the mode switching between zero stiffness and stiffness rendering can be realized by the engagement and disengagement of the claw of the ratchet clutch structure and the ratchet. Therefore, the force feedback device can realize real physical stiffness feedback ranging from zero impedance to theoretically infinite. In surgical training or other tasks, it provides the user with the force information in the interaction between the user's hand and the virtual object as if it were real. In the force feedback device, the motor is only used to adjust the position of the elastic element on the guide rail and does not directly participate in the output of the feedback force. Therefore, the device belongs to a quasi-active force feedback device.

[0012] To achieve the above object, the technical solution adopted by the present invention is:

[0013] A force feedback device for assisting a surgical robot in gripping operations comprises a variable stiffness mechanism, a blocking mechanism, a ratchet clutch mechanism, a grasping mechanism, a measuring unit, a control processing unit and a power supply module. The variable stiffness mechanism renders the output stiffness of the force feedback device by adjusting the position of a compression spring on the guide rail of a linear guide slider group. The blocking mechanism comprises a baffle and a brake. The baffle is mounted on the ratchet of the variable stiffness mechanism. The brake is mounted on the far hand end of the slider of the linear guide slider group of the variable stiffness mechanism. The ratchet motor in the ratchet clutch mechanism drives the corresponding transmission gear group to drive the ratchet claw to engage or disengage with the ratchet in the variable stiffness mechanism, thereby realizing the mode switching between zero stiffness and stiffness rendering of the force feedback device. The grasping mechanism is the frame and support of the force feedback device, including a relatively fixed end and a grasping handle, the relatively fixed end has a built-in control processing unit and a power supply module, the far-hand side of the grasping handle is connected to the ratchet clutch mechanism, when the ratchet pawl of the ratchet clutch mechanism engages with the ratchet of the variable stiffness mechanism, the force generated by the compression spring will be transmitted to the grasping handle through the lever arm of the variable stiffness mechanism and then fed back to the operator's hand, the measuring unit is connected to the control processing unit, and realizes data measurement of the motor's pushing distance, grasping angle, and lever arm angle, the control processing unit processes the data of the sensor unit and controls the motor, and the power supply module supplies power to the variable stiffness mechanism, control processing unit and electronic module of the force feedback device.

[0014] As a further improvement of the structure of the present invention, the variable stiffness mechanism includes a lever arm, a spring baffle, a spring stop wheel, a rotating shaft, a linear motor, a ratchet, an L-shaped base, a linear guide slider group, a spring carrier and a compression spring. The lever arm is connected to the L-shaped base through the rotating shaft, and the front end of the lever arm is fixed to the ratchet by a screw. A positioning hole is reserved at the tail of the spring baffle, and it is fixed to the linear motor by fasteners. A through hole is reserved at the center of the side of the spring baffle for installing the spring stop wheel. Two through holes are reserved at the bottom of the spring baffle for constraining the compression spring. A thread is reserved at the bottom of the L-shaped base, and the linear guide slider group is fixed by screws. The guide slider group also has a thread, and the spring carrier is fixed by screws. A through hole is reserved at the top of the spring carrier, which cooperates with the through hole at the bottom of the spring baffle. The compression spring can extend into the upper and lower through holes to play a fixing role.

[0015] As a further improvement of the structure of the present invention, the baffle of the blocking mechanism is connected to the ratchet in the variable stiffness mechanism through a fastener, and the brake of the blocking mechanism is fixed to the front end of the spring carrier. When the spring moves to a certain position, the baffle and the brake come into hard contact to prevent the lever arm from moving.

[0016] As a further improvement to the structure of the present invention, the ratchet motor of the ratchet clutch mechanism is fixed to the far end of the holding handle of the grasping mechanism by screws, and meshes with the gears of the transmission gear set. A screw hole is reserved in the center of the transmission gear set, and the holding handle and the ratchet claw are connected by screws.

[0017] As a further improvement of the structure of the present invention, the grasping handle of the grasping mechanism is a Z-shaped structure, and a threaded hole is reserved on the far-hand side for installing and fixing the transmission gear set of the ratchet clutch mechanism through screws.

[0018] As a further improvement of the structure of the present invention, the measuring unit includes a grasping angle encoder, a lever arm angle encoder and a potentiometer, the grasping angle encoder and the lever arm angle encoder are installed on the left and right sides of the encoder receiving part, the grasping angle encoder has a threaded hole at the bottom, and is fixed to the encoder receiving part with screws, and is used for the rotation angle of the hand grasping through the PU belt transmission, the lever arm angle encoder has a threaded hole at the bottom, and is fixed to the encoder receiving part with screws, and is used for measuring the rotation angle of the lever arm through the PU belt transmission, and is used to collect the real-time angle information of the grasping handle of the grasping mechanism and the lever arm of the variable stiffness mechanism respectively, and the potentiometer is formed at the bottom of the linear motor of the variable stiffness mechanism, and is used to collect the output shaft length information of the linear motor and then determine the real-time position of the compression spring on the slide rail. The return values ​​of the grasping angle encoder, the lever arm angle encoder and the potentiometer can be used to calculate the stiffness and output torque of the force feedback device.

[0019] As a further improvement of the structure of the present invention, the control processing unit is composed of a data acquisition storage unit and a control processor. The data acquisition storage unit is responsible for collecting information such as the angle and position of the measuring unit, and the control processor processes these data and calculates the feedback force and stiffness of the device.

[0020] The present invention provides a force feedback method for a force feedback device for assisting a surgical robot clamping operation, comprising the following steps:

[0021] The force feedback device is powered on, and the grip angle encoder, lever arm angle encoder, potentiometer, linear motor, ratchet motor and its drive circuit, analog-to-electric converter, and microcontroller are operating normally;

[0022] Select the ratchet engagement state, press the grip handle to drive the lever arm to rotate, and the pressure is transmitted to the spring baffle through the baffle pulley. The left spring and the right spring are deformed and generate reaction force to achieve force feedback;

[0023] The control processing unit calculates the expected stiffness and feedback torque according to the stiffness information and rotation angle of the virtual object in the medical task and the sensor information related to the spring position, and controls the motor operation to change the spring position.

[0024] As a further improvement of the force feedback method of the present invention, the feedback torque τ of the force feedback device 0 and stiffness σ 0 Calculated by the following formula:

[0025]

[0026] In the formula, k s is the elastic constant of the spring, where θ 0 is the rotation angle of the lever arm measured by the deflection angle encoder, l e It is the distance from the center of the spring stop to the center of the lever arm's rotation axis.

[0027] Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0028] The present invention can adjust the feedback force between zero stiffness and full rigidity through the spring-lever mechanism, and can simulate various mechanical properties from soft tissue to hard tissue, which means that the device can accurately simulate the feedback of different tissues such as skin, muscle, and bone. The generation of feedback force is affected by both the lever arm grip angle and the device stiffness. The position of the spring is adjusted by the microcontroller to control the length of the force arm and thus control the rendering of the device stiffness; thanks to the use of the ratchet clutch structure, the device can achieve zero stiffness and stiffness rendering mode switching by engaging and disengaging the ratchet; a blocking structure is placed on the ratchet and the spring carrier, so that the operator can feel the theoretically infinite stiffness; the present invention uses a small linear actuator, which is only used to adjust the spring position, and does not directly generate feedback force, so the device involved in the present invention is a semi-active force feedback device. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of electrical connections of various components of a force feedback device for assisting a surgical robot gripping operation provided by the present invention;

[0030] Figure 2 It is a front view of a force feedback device for assisting a surgical robot in clamping operations provided by the present invention;

[0031] Figure 3 It is a stereoscopic view of a force feedback device for assisting a surgical robot clamping operation provided by the present invention;

[0032] Figure 4 It is the front view of the variable stiffness mechanism;

[0033] Figure 5 It is the main view of the blocking mechanism;

[0034] Figure 6 It is the front view of the ratchet clutch mechanism;

[0035] Figure 7 is the front view of the holding mechanism;

[0036] Figure 8 It is a bottom view of the measurement unit;

[0037] Fig. 9 This is a model diagram of the elastic element, fulcrum and lever in the force feedback device.

[0038] Description of reference numerals:

[0039] 1. Variable stiffness mechanism; 1-1. Lever arm; 1-2. Spring baffle; 1-3. Spring baffle wheel; 1-4. Rotating axis; 1-5. Linear motor; 1-6. Ratchet; 1-7. L-shaped base; 1-8. Linear guide slider group; 1-9. Spring carrier; 1-10. Compression spring; 2. Blocking mechanism; 2-1. Baffle; 2-2. Brake; 3. Ratchet clutch mechanism; 3-1. Transmission gear group; 3-2. Ratchet motor; 3-3. Ratchet pawl; 4. Grip mechanism; 4-1. Relative fixed end; 4-2. Grip handle; 5. Measuring unit; 5-1. Grip angle encoder; 5-2. Lever arm angle encoder; 5-3. Potentiometer; 6. Control processing unit; 7. Power module. DETAILED DESCRIPTION

[0040] The following is a further detailed description of the technical solution of the application in conjunction with the accompanying drawings. The described embodiments are only part of the embodiments involved in this patent. All non-innovative embodiments of other researchers in this field based on this embodiment are within the scope of protection of this patent.

[0041] Reference Figure 1 , Figure 2 , Figure 3 The present invention provides a force feedback device for assisting the clamping operation of a surgical robot, which includes a variable stiffness mechanism 1, a blocking mechanism 2, a ratchet clutch mechanism 3, a grasping mechanism 4, a measuring unit 5, a control processing unit 6 and a power module 7. The variable stiffness mechanism 1 is the core functional mechanism of the force feedback device, which renders the output stiffness of the force feedback device by adjusting the position of the compression spring on the guide rail. The blocking mechanism 2 includes a baffle and a brake, wherein the baffle is mounted on the ratchet of the variable stiffness mechanism 1, and the brake is mounted on the far end of the slider of the linear guide slider group of the variable stiffness mechanism 1. The ratchet motor in the ratchet clutch mechanism 3 drives the ratchet claw to engage or disengage with the ratchet in the variable stiffness mechanism 1, thereby realizing the mode switching between zero stiffness and stiffness rendering of the force feedback device. The grasping mechanism 4 is the frame and support of the force feedback device, including a fixed end and a grasping handle. The fixed end has a built-in control processing unit 6 and a power module 7. The grasping handle is a Z-shaped structure, and the far hand side is connected to the ratchet clutch mechanism 3. When the claw of the ratchet clutch mechanism 3 is engaged with the ratchet of the variable stiffness mechanism 1, the force generated by the compression spring will be transmitted to the grasping handle through the lever arm of the variable stiffness mechanism 1 and then fed back to the operator's hand. The measuring unit 5 realizes the data measurement of the pushing distance, grasping angle, and lever arm angle of the motor. The measuring unit 5 is connected to the control processing unit 6 for data transmission, communication, etc. The control processing unit 6 processes the data of the sensor unit and controls the motor. The power module 7 supplies power to the variable stiffness mechanism 1, the control processing unit 6, and the electronic module of the force feedback device.

[0042] Reference Figure 4, the variable stiffness mechanism 1 comprises a lever arm 1-1, a spring baffle 1-2, a spring stop wheel 1-3, a rotating shaft 1-4, a linear motor 1-5, a ratchet 1-6, an L-shaped base 1-7, a linear guide slider group 1-8, a spring carrier 1-9 and a compression spring 1-10. The lever arm 1-1 is connected to the L-shaped base 1-7 through the rotating shaft 1-4, and the front end fixes the ratchet 1-6 with screws and a grip. A positioning hole is reserved at the tail of the spring baffle 1-2, and it is fixed to the linear motor 1-5 by fasteners. A through hole is reserved in the center of the side of the spring baffle 1-2 for installing the spring stop wheel 1-3, and two through holes are reserved at the bottom of the spring baffle 1-2 for constraining the compression spring 1-10. A thread is reserved at the bottom of the L-shaped base 1-7, and the linear guide slider group 1-8 is fixed by screws. The guide slider group 1-8 also has a thread, and the spring carrier 1-9 is fixed by screws. A through hole is left at the top of the spring carrier 1-9, which matches with the through hole at the bottom of the spring baffle 1-2, and the compression spring 1-10 can extend into the upper and lower through holes to play a fixing role.

[0043] Reference Figure 5 The blocking mechanism 2 includes a baffle 2-1 and a brake 2-2. The baffle 2-1 is connected to the ratchet 1-6 in the variable stiffness mechanism 1 through a fastener, and the brake 2-2 is installed and fixed at the front end of the middle spring carrier 1-9. When the spring moves to a certain position, the baffle 2-1 and the brake 2-2 come into hard contact to prevent the lever arm from moving.

[0044] Reference Figure 6 The ratchet clutch mechanism 3 includes a transmission gear set 3-1, a ratchet motor 3-2 and a ratchet pawl 3-3. The ratchet motor 3-2 is fixed to the far hand end of the grip handle 4-2 of the grasping mechanism 4 by screws, and meshes with the transmission gear set 3-1 gear. A screw hole is reserved in the center of the transmission gear set 3-1, and the grip handle 4-2 and the ratchet pawl 3-3 are connected by screws. The ratchet pawl 3-3 is controlled by the ratchet motor 3-2 and can be engaged or disengaged with the ratchet 1-6 in the variable stiffness mechanism 1.

[0045] Reference Figure 7 The grasping mechanism 4 includes a fixed end 4-1 and a grasping handle 4-2, the fixed end 4-1 and the grasping handle 4-2 are connected through the rotating shaft 1-4 of the variable stiffness mechanism 1, the fixed end is equipped with a control processing unit 6 and a power supply module 7, the grasping handle is a Z-shaped structure, and a threaded hole is reserved on the far-hand side to install and fix the ratchet clutch mechanism 3 transmission gear set 3-1 through screws.

[0046] Reference Figure 8, the measuring unit 5 includes a grasping angle encoder 5-1, a lever arm angle encoder 5-2 and a potentiometer 5-3. The grasping angle encoder 5-1 and the lever arm angle encoder 5-2 are installed on the left and right sides of the encoder receiving part, and are used to collect the real-time angle information of the grasping handle 4-2 of the grasping mechanism 4 and the lever arm 1-1 of the variable stiffness mechanism 1 through the relevant pulleys and PU belt transmission. Specifically, the grasping angle encoder 5-1 has a threaded hole at the bottom, which is fixed to the encoder receiving part with screws, and is used to measure the rotation angle of the hand grasping through the PU belt transmission. The lever arm angle encoder 5-2 has a threaded hole at the bottom, which is fixed to the encoder receiving part with screws, and is used to measure the rotation angle of the lever arm through the PU belt transmission. The potentiometer 5-3 is integrated at the bottom of the linear motor 1-5 of the variable stiffness mechanism 1, and is used to collect the output shaft length information of the motor and then determine the real-time position of the spring on the slide rail. The return values ​​of the grasping angle encoder, the lever arm angle encoder and the potentiometer can be used to calculate the stiffness and output torque of the force feedback device.

[0047] The control processing unit 6 is composed of a data acquisition storage unit and a control processor. The data acquisition storage unit is responsible for collecting information such as the angle and position of the measuring unit 5, and the control processor processes these data and calculates the feedback force and stiffness of the device.

[0048] The power module 7 supplies power to the linear motors 1 - 5 , the measuring unit 5 and the control processing unit 6 in the variable stiffness mechanism 1 of the force feedback device.

[0049] Reference Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8Based on the force feedback device for assisting the clamping operation of the surgical robot, the present invention also provides the force feedback method for assisting the clamping operation of the surgical robot. The designed variable stiffness mechanism can control the position of the spring to adjust the stiffness of the device to simulate the stiffness of different tissues such as skin, muscle, and bone. When the stiffness of the virtual object is known and input to the control processing unit 6, the ratchet claw 3-3 in the ratchet clutch mechanism 3 engages or falls off with the ratchet according to the need of stiffness rendering. When the ratchet claw 3-3 engages with the ratchet 1-6, the control processing unit 6 processes and calculates the position of the compression spring 1-10 according to the stiffness of the virtual object, and uses the PID control algorithm to control the linear motor 1-5 to achieve precise control of the position of the compression spring 1-10; when the torque of the operator's contact with the virtual object is known, the control processing unit 6 calculates the stiffness of the virtual object according to the contact torque and the rotation angle collected by the lever arm angle encoder 5-2, and repeats the above process to control the stiffness of the force feedback device. The measuring unit 5 and the control processing unit 6 can detect and calculate the stiffness and the torque applied by the user to the grip handle 4-2 in real time, and dynamically adjust the stiffness of the device according to the stiffness of the virtual object, thereby providing more accurate stiffness and force feedback. In addition, the characteristics of the spring enhance the safety of the device. On the other hand, the motor is only used to adjust the position of the compression spring on the guide rail and does not directly participate in the output of the feedback force. Therefore, the device belongs to a quasi-active force feedback device.

[0050] The feedback force and the virtual object stiffness can be obtained by calculating the data collected by the angle encoder 5-1, the lever arm angle encoder 5-2 and the potentiometer 5-3 through a microcontroller. Fig. 9 This is a basic model for the elastic element, fulcrum and lever in the force feedback device. For the convenience of description, the following geometric parameters need to be defined first:

[0051] (1) The inherent elastic coefficient of the spring is k s ;

[0052] (2) The distance between the center of the spring baffle and the center of the lever arm rotation axis can be measured by the potentiometer as l e ;

[0053] (3) The lever arm angle encoder 5-2 can measure the lever arm rotation angle θ 0 ;

[0054] Based on the above parameters, the deformation h of the spring caused by the lever can be calculated. s for:

[0055] h s = l e tanθ 0

[0056] At this time, the reaction force F generated by the spring s for:

[0057] F s =k s h s

[0058] The direction of the spring force on the lever arm is perpendicular to the plane of the lever arm. 0 for:

[0059]

[0060] The component of force F generated by the spring on the spring carrier parallel to the horizontal plane h for:

[0061]

[0062] According to the above parameters, the feedback torque τ can be calculated 0 :

[0063]

[0064] Stiffnessσ 0 is the partial derivative of the torque with respect to the rotation angle and is calculated using the following formula:

[0065]

[0066] In summary, the output stiffness of the force feedback device in the present invention depends on the position of the spring, and the feedback force felt by the operator's hand and the stiffness of the virtual object can be obtained by solving the data collected by the potentiometer and the angle encoder through the microcontroller. Therefore, in medical tasks such as surgical training and rehabilitation treatment, doctors can obtain the force information in the interaction with the virtual object as if it were real through the force feedback device provided by the present invention, and can collect the data in the experiment and calibrate the force feedback device through the external force sensor.

[0067] The above description is only a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent change made based on the technical essence of the present invention still falls within the scope of protection required by the present invention.

Claims

1. A force feedback device for assisting a surgical robot in gripping operations, characterized in that: The invention comprises a variable stiffness mechanism (1), a blocking mechanism (2), a ratchet clutch mechanism (3), a grasping mechanism (4), a measuring unit (5), a control processing unit (6) and a power supply module (7). The variable stiffness mechanism (1) renders the output stiffness of the force feedback device by adjusting the position of a compression spring (1-10) on the guide rail of a linear guide rail slider group (1-8). The blocking mechanism (2) comprises a baffle (2-1) and a brake (2-2). The baffle (2-1) is installed On the ratchet (6) of the variable stiffness mechanism (1), the brake (2-2) is installed at the far end of the slider of the linear guide slider group (1-8) of the variable stiffness mechanism (1), and the ratchet motor (3-2) in the ratchet clutch mechanism (3) drives the corresponding transmission gear group (3-1) to drive the ratchet claw (3-3) to engage or disengage with the ratchet (1-6) in the variable stiffness mechanism (1), thereby realizing the mode switching between zero stiffness and stiffness rendering of the force feedback device, and the grasping mechanism ( 4) is a frame and support of the force feedback device, including a relatively fixed end (4-1) and a grasping handle (4-2), the relatively fixed end (4-1) is equipped with a control processing unit (6) and a power module (7), the far-hand side of the grasping handle (4-2) is connected to a ratchet clutch mechanism (3), when the ratchet claw (3-3) of the ratchet clutch mechanism (3) is engaged with the ratchet (1-6) of the variable stiffness mechanism (1), the force generated by the compression spring (1-10) is transmitted to the grasping handle (4-2) through the lever arm (1-1) of the variable stiffness mechanism (1) and then fed back to the operator's hand, the measuring unit (5) is connected to the control processing unit (6) and realizes data measurement of the pushing distance, grasping angle and lever arm angle of the motor, the control processing unit (6) processes the data of the sensor unit and controls the motor, and the power module (7) supplies power to the variable stiffness mechanism (1), the control processing unit (6) and the electronic module of the force feedback device.

2. A force feedback device for assisting a surgical robot in gripping operations according to claim 1, characterized in that: The variable stiffness mechanism (1) comprises a lever arm (1-1), a spring baffle (1-2), a spring baffle wheel (1-3), a rotating shaft (1-4), a linear motor (1-5), a ratchet (1-6), an L-shaped base (1-7), a linear guide slider group (1-8), a spring carrier (1-9) and a compression spring (1-10); the lever arm (1-1) is connected to the L-shaped base (1-7) via the rotating shaft (1-4); the front end of the lever arm (1-1) is fixedly mounted with the ratchet wheel (1-6) via a screw; a positioning hole is reserved at the rear end of the spring baffle (1-2) and is connected to the linear motor (1-1) via a fastener. 5) Installation and fixation, a through hole is reserved at the center of the side of the spring baffle (1-2) for installing the spring baffle wheel (1-3), two through holes are reserved at the bottom of the spring baffle (1-2) for constraining the compression spring (1-10), a thread is reserved at the bottom of the L-shaped base (1-7), and the linear guide slider group (1-8) is installed and fixed by screws, and the guide slider group (1-8) is also reserved with a thread, and the spring carrier (1-9) is fixed by screws, and a through hole is reserved at the top of the spring carrier (1-9), which cooperates with the through hole at the bottom of the spring baffle (1-2), and the compression spring (1-10) can extend into the upper and lower through holes to play a fixing role.

3. A force feedback device for assisting a surgical robot in gripping operations according to claim 2, characterized in that: The baffle (2-1) of the blocking mechanism (2) is connected to the ratchet (1-6) in the variable stiffness mechanism (1) via a fastener, while the brake (2-2) of the blocking mechanism (2) is installed and fixed on the front end of the spring carrier (1-9).

4. A force feedback device and method for assisting a surgical robot in gripping operations according to claim 1, characterized in that: The ratchet motor (3-2) of the ratchet clutch mechanism (3) is fixed to the far end of the gripping handle (4-2) of the grasping mechanism (4) by means of screws, and meshes with the gear of the transmission gear set (3-1). A screw hole is reserved in the center of the transmission gear set (3-1), and the gripping handle (4-2) and the ratchet pawl (3-3) are connected by means of screws.

5. A force feedback device and method for assisting a surgical robot in gripping operations according to claim 1, characterized in that: The grip handle (4-2) of the grip mechanism (4) is a Z-shaped structure, with a threaded hole on the far hand side for mounting and fixing the transmission gear set (3-1) of the ratchet clutch mechanism (3) via screws.

6. A force feedback device and method for assisting a surgical robot gripping operation according to claim 1, characterized in that: The measuring unit (5) comprises a grasping angle encoder (5-1), a lever arm angle encoder (5-2) and a potentiometer (5-3). The grasping angle encoder (5-1) and the lever arm angle encoder (5-2) are installed on the left and right sides of the encoder receiving part. The grasping angle encoder (5-1) has a threaded hole at the bottom and is fixed to the encoder receiving part by screws. The grasping angle encoder (5-1) is used to measure the rotation angle of the hand grasping through a PU belt transmission. The lever arm angle encoder (5-2) has a threaded hole at the bottom and is fixed to the encoder receiving part by screws. The lever arm angle encoder (5-2) is used to measure the rotation angle of the lever arm through a PU belt transmission. The lever arm angle encoder is used to collect the real-time angle information of the grasping handle (4-2) of the grasping mechanism (4) and the lever arm (1-1) of the variable stiffness mechanism (1). The potentiometer (5-3) is formed at the bottom of the linear motor (1-5) of the variable stiffness mechanism (1) and is used to collect the output shaft length information of the linear motor (1-5) and thereby determine the real-time position of the compression spring (1-10) on the slide rail.

7. A force feedback device and method for assisting a surgical robot in gripping operations according to claim 1, characterized in that: The control processing unit is composed of a data acquisition storage unit and a control processor. The data acquisition storage unit is responsible for collecting information such as the angle and position of the measuring unit, and the control processor processes these data and calculates the feedback force and stiffness of the device.

8. A force feedback method using the force feedback device for assisting a surgical robot gripping operation according to any one of claims 1 to 8, characterized in that: The steps include: The force feedback device is powered on, and the grip angle encoder (5-1), the lever arm angle encoder (5-2), the potentiometer (5-3), the linear motor (1-5), the ratchet motor (3-2) and its drive circuit, analog-to-electric converter, and microcontroller operate normally; The ratchet wheel (6) is selected to be in an engaged state, and the gripping handle (4-2) is pressed to drive the lever arm (11) to rotate, and the pressure is transmitted to the spring baffle (1-2) through the baffle pulley, and the left spring and the right spring are deformed and a reaction force is generated, thereby realizing force feedback; The control processing unit (6) calculates the expected stiffness and feedback torque according to the stiffness information and rotation angle of the virtual object in the medical task and the sensor information related to the spring position, and controls the motor to operate to change the spring position.

9. The force feedback method of the force feedback device for assisting the clamping operation of a surgical robot according to claim 8, characterized in that: The feedback torque τ0 and stiffness σ0 of the force feedback device are calculated by the following formula: In the formula, k s is the elastic constant of the spring, where θ0 is the rotation angle of the lever arm measured by the deflection angle encoder, l e It is the distance from the center of the spring stop to the center of the lever arm's rotation axis.

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