A force feedback device and method for assisting surgical robot clamping operation

Abstract

A force feedback device and method for assisting surgical robot clamping operations, the present invention belongs to the field of VR force feedback and mechanical technology. The device includes a variable stiffness mechanism, a blocking structure, a ratchet clutch structure, a gripping 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 by the variable stiffness mechanism, thereby achieving adjustment of the stiffness of the force feedback device. The blocking mechanism achieves infinite stiffness rendering by limiting the operator's grip. The mode switching between zero stiffness and stiffness rendering can be achieved by engaging and disengaging the claw of the ratchet clutch structure with the ratchet. Therefore, the force feedback device can achieve 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, and the properties of the elastic element make the present 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 surgical robot clamping operations. Background Art

[0002] The application of virtual reality (VR) technology in the medical field has made significant progress, particularly in surgical training, rehabilitation therapy, and telemedicine. Force feedback technology, a key component in enhancing the immersiveness of virtual environments, can help doctors and patients gain more physical sensory information within virtual environments, significantly improving the precision and safety of medical procedures. In surgical training, force feedback devices can simulate the force sensation and resistance feedback of actual surgical procedures, helping surgeons and medical students practice procedures in a virtual environment. By providing feedback of varying hardness and elasticity, doctors can perceive the characteristics of different tissues, such as skin, muscle, and bone, during training, thereby improving the precision and safety of procedures. In rehabilitation therapy, force feedback technology can be used to simulate the various movements and forces used in physical therapy, helping patients perform restorative exercises using virtual devices to improve joint mobility and muscle strength. With adjustable feedback force, patients can gradually adapt to training from light to heavy forces, facilitating recovery. Furthermore, in telemedicine, force feedback devices can help doctors remotely operate robotic arms or other medical devices, enabling precise surgery or treatment. Traditional remote operations carry a high risk due to the lack of force information. The introduction of force feedback technology can provide more precise operational 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 electric motors and pneumatic actuators to generate feedback force and can usually provide relatively accurate force feedback. Impedance-type devices provide feedback through a reverse-driven electric motor, allowing users to 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 electric motor and a force sensor, and are suitable for simulating the feedback of rigid objects. However, these devices are generally bulky and have high power consumption. They 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, which rely on motors to generate feedback force, passive force feedback devices provide feedback through physical mechanisms such as springs. These devices are typically lightweight, consume less power, and are suitable for simulating contact with hard objects. Existing devices often provide feedback through mechanical structures, capable of simulating strong resistance and suitable for simulating contact with hard objects. However, they cannot simulate interactions with elastic or soft objects and lack the feedback capability for flexible objects. Furthermore, these devices lack flexibility and cannot meet complex interaction requirements, limiting their application in scenarios requiring precise manipulation.

[0006] Hybrid force feedback devices combine active and passive actuation, hoping to leverage their strengths and overcome their weaknesses, potentially offering a path to medical applications. Existing work has combined magnetorheological brakes and electric motors to achieve feedback by modulating friction and force output, enabling high output force while maintaining low weight.

[0007] The present application differs from the prior art in the following ways:

[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 simulated instantaneous impact force generated by the thumb and index finger servos, elastic force generated by the spring ratchet and torsion spring, and friction generated by the interleaved servos and nuts. To ensure safe operation during robotic grasping, we have designed a hybrid-driven handheld force feedback device that incorporates a spring-lever mechanism. The output force is derived entirely from the elastic force generated by spring deformation.

[0010] In patent CN114452640A, the ratchet teeth block the spring ratchet, preventing the user from performing an inward pinching motion. However, our approach uses a ratchet with a baffle and a brake fixed to a spring carrier to form a blocking mechanism to restrict the user's gripping motion. 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 surgical robot clamping operations. The structure is based on a hybrid drive handheld force feedback device with the combined action of a spring and 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 achieving the adjustment of the stiffness of the force feedback device; the blocking mechanism achieves infinite stiffness rendering by limiting the gripping movement; on the other hand, the engagement and disengagement of the claw and the ratchet of the ratchet clutch structure can achieve mode switching between zero stiffness and stiffness rendering. Therefore, the force feedback device can achieve 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 of the user's hand interacting with the virtual object as if it were real. In this 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 is 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 pawl 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. 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, which is fixed to the linear motor through fasteners. A through hole is left in the center of the side of the spring baffle for installing the spring stop wheel. Two through holes are left at the bottom of the spring baffle for constraining the compression spring. The bottom of the L-shaped base is threaded, and the linear guide slider group is fixed by screws. The guide slider group also has threads, and the spring carrier is fixed by screws. A through hole is left 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 to the structure of the present invention, the baffle of the blocking mechanism is connected to the ratchet in the variable stiffness mechanism via 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, thereby preventing 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 pawl are connected by screws.

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

[0018] As a further improvement to 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, which is fixed to the encoder receiving part with screws and is driven by a PU belt to measure the rotation angle of the hand grasping. The lever arm angle encoder has a threaded hole at the bottom, which is fixed to the encoder receiving part with screws and is driven by a PU belt to measure the rotation angle of the lever arm. They are respectively used to collect real-time angle information of the grasping handle of the grasping mechanism and the lever arm of the variable stiffness mechanism. 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 thus 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 to the structure of the present invention, the control processing unit is composed of a data acquisition and storage unit and a control processor. The data acquisition and storage unit is responsible for collecting information such as the angle and position of the measuring unit, and the control processor processes this 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 in a gripping 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 and right springs are deformed and generate reaction force to achieve force feedback;

[0023] The control processing unit calculates the expected stiffness and feedback torque based on 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 to the force feedback method of the present invention, the feedback torque τ0 and stiffness σ0 of the force feedback device are calculated by the following formula:

[0025]

[0026] Where k s is the elastic constant of the spring, θ0 is the rotation angle of the lever arm measured by the deflection angle encoder, l e It is the distance between the center of the spring stop and 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 uses a spring-lever mechanism to adjust the feedback force between zero stiffness and full rigidity, 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 grip angle of the lever arm and the stiffness of the device. The position of the spring is adjusted by the microcontroller to control the length of the force arm and thus the rendering of the device stiffness. Thanks to the use of a ratchet clutch structure, the device can switch between zero stiffness and stiffness rendering modes by engaging and disengaging the ratchet. A blocking structure is placed on the ratchet and the spring carrier, allowing the operator to feel theoretically infinite stiffness. The present invention uses a small linear actuator, which is only used to adjust the position of the spring and does not directly generate feedback force. Therefore, the device involved in the present invention is a semi-active force feedback device. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0031] Figure 3 This is a three-dimensional view of a force feedback device for assisting a surgical robot in gripping operations provided by the present invention;

[0032] Figure 4 It is the main 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 It is the main view of the holding mechanism;

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

[0037] Figure 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 assembly; 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 assembly; 3-2. Ratchet motor; 3-3. Ratchet pawl; 4. Gripping mechanism; 4-1. Relatively fixed end; 4-2. Gripping handle; 5. Measuring unit; 5-1. Gripping 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 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 based on this embodiment by other researchers in this field fall 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 supply 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, the baffle is installed on the ratchet of the variable stiffness mechanism 1, and the brake is installed on the far-hand 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 pawl 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 gripping mechanism 4 is the frame and support of the force feedback device, including a fixed end and a gripping handle. The fixed end has a built-in control processing unit 6 and a power supply module 7. The gripping handle is a Z-shaped structure, and the far-hand side is connected to the ratchet clutch mechanism 3. When the pawl of the ratchet clutch mechanism 3 engages with the ratchet of the variable stiffness mechanism 1, the force generated by the compression spring is transmitted to the gripping handle through the lever arm of the variable stiffness mechanism 1 and then fed back to the operator's hand. The measuring unit 5 measures the motor's pushing distance, gripping angle, and lever arm angle. The measuring unit 5 is connected to the control processing unit 6 for data transmission and communication. The control processing unit 6 processes the data of the sensor unit and controls the motor. The power supply 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 4The variable stiffness mechanism 1 includes 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 assembly 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 ratchet 1-6 is fixed to the front end by 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. The bottom of the L-shaped base 1-7 is threaded, and the linear guide slider assembly 1-8 is fixed by screws. The guide slider assembly 1-8 is also threaded, and the spring carrier 1-9 is fixed by screws. A through hole is left on the top of the spring carrier 1-9, which cooperates with the through hole at the bottom of the spring baffle 1-2. 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 via fasteners, while the brake 2-2 is mounted and fixed to the front end of the 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, preventing 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 screwed to the distal end of the gripping handle 4-2 of the grasping mechanism 4 and meshes with the gears of the transmission gear set 3-1. A screw hole is provided in the center of the transmission gear set 3-1, which connects the gripping handle 4-2 to the ratchet pawl 3-3. The ratchet pawl 3-3 is controlled by the ratchet motor 3-2 and can engage or disengage with the ratchet 1-6 of 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 side for fixing the ratchet clutch mechanism 3 transmission gear set 3-1 by screws.

[0046] Reference Figure 8The measurement unit 5 includes a grip angle encoder 5-1, a lever arm angle encoder 5-2, and a potentiometer 5-3. The grip angle encoder 5-1 and the lever arm angle encoder 5-2 are mounted on the left and right sides of the encoder mounting assembly and, through associated pulleys and a PU belt transmission, are used to collect real-time angle information from the grip handle 4-2 of the gripping mechanism 4 and the lever arm 1-1 of the variable stiffness mechanism 1, respectively. Specifically, the grip angle encoder 5-1 has a threaded hole at its bottom that is screwed to the encoder mounting assembly and is used to measure the rotation angle of the hand grip. The lever arm angle encoder 5-2 has a threaded hole at its bottom that is screwed to the encoder mounting assembly and is used to measure the rotation angle of the lever arm through a PU belt transmission. The potentiometer 5-3 is integrated into the bottom of the linear motor 1-5 of the variable stiffness mechanism 1 and is used to collect information on the motor's output shaft length and thereby determine the real-time position of the spring on the slide rail. The return values ​​from the grip angle encoder, lever arm angle encoder, and 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 and storage unit and a control processor. The data acquisition and storage unit is responsible for collecting information such as the angle and position of the measuring unit 5, while the control processor processes this data and calculates the feedback force and stiffness of the device.

[0048] The power supply 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 above-mentioned force feedback device for assisting a surgical robot in gripping operations, the present invention also provides a force feedback method for assisting a surgical robot in gripping operations. The designed variable stiffness mechanism can control the position of the spring to adjust the stiffness of the device, thereby simulating the stiffness of different tissues such as skin, muscle, and bone. When the stiffness of the virtual object is known and input into the control processing unit 6, the ratchet pawl 3-3 in the ratchet clutch mechanism 3 engages or disengages with the ratchet according to the stiffness rendering requirements. When the ratchet pawl 3-3 engages with the ratchet 1-6, the control processing unit 6 calculates the position of the compression spring 1-10 based on the stiffness of the virtual object and uses a PID control algorithm to regulate 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 based on the contact torque and the rotation angle collected by the lever arm angle encoder 5-2. The above process is repeated to control the stiffness of the force feedback device. The measurement unit 5 and control processing unit 6 are able to detect and calculate the stiffness and torque applied by the user to the grip handle 4-2 in real time. They dynamically adjust the stiffness of the device based on the stiffness of the virtual object, thereby providing more accurate stiffness and force feedback. Furthermore, 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 feedback force. Therefore, this device is 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 the microcontroller. Figure 9 This is a basic model for the elastic element, fulcrum, and lever in a force feedback device. For ease 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 θ0;

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

[0055] h s =l e tanθ0

[0056] The reaction force F generated by the spring s for:

[0057] F s =k s h s

[0058] The force F0 generated by the spring on the lever arm in a direction perpendicular to the plane of the lever arm is:

[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 τ0 can be calculated:

[0063]

[0064] Stiffness σ0 is the partial derivative of 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 this invention depends on the position of the spring. The feedback force felt by the operator's hand and the stiffness of the virtual object can both be calculated by a microcontroller using data collected by the potentiometer and angle encoder. Therefore, during medical tasks such as surgical training and rehabilitation therapy, doctors can use the force feedback device provided by this invention to obtain realistic force information from interactions with virtual objects. Using an external force sensor, experimental data can be collected and used to calibrate the force feedback device.

[0067] The above description is merely a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent variation based on the technical essence of the present invention shall still fall within the scope of protection claimed 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 the compression spring (1-10) on the guide rail of the 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 (1-6) 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. (4) is a frame and support of the force feedback device, including a relatively fixed end (4-1) and a grasping handle (4-2), wherein the relatively fixed end (4-1) is built with a control processing unit (6) and a power supply module (7), and the far-hand side of the grasping handle (4-2) is connected to the ratchet clutch mechanism (3), when the ratchet pawl (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 motor's pushing distance, grasping angle, and lever arm angle, the control processing unit (6) processes the data of the sensor unit and controls the motor, and the power supply module (7) supplies power to the variable stiffness mechanism (1), the control processing unit (6) and the electronic module of the force feedback device; 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). At the same time, the front end of the lever arm (1-1) is fixedly installed with the ratchet wheel (1-6) via a screw. A positioning hole is reserved at the tail 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 left at the center of the side of the spring baffle (1-2) for installing the spring baffle wheel (1-3); two through holes are left at the bottom of the spring baffle (1-2) for constraining the compression spring (1-10); a thread is left at the bottom of the L-shaped base (1-7); the linear guide slider group (1-8) is fixed by screws; the guide slider group (1-8) also has a thread and is fixed by screws to the spring carrier (1-9); a through hole is left at the top of the spring carrier (1-9) and matches with the through hole at the bottom of the spring baffle (1-2); the compression spring (1-10) can extend into the upper and lower through holes to play a fixing role.

2. A force feedback device for assisting a surgical robot in gripping operations according to claim 1, 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 mounted and fixed on the front end of the spring carrier (1-9).

3. The force feedback device 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 distal end of the grip handle (4-2) of the grip mechanism (4) by 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 grip handle (4-2) and the ratchet pawl (3-3) are connected by screws.

4. The force feedback device for assisting a surgical robot in gripping operations according to claim 1, characterized in that: The gripping handle (4-2) of the gripping 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.

5. The force feedback device for assisting a surgical robot in gripping operations according to claim 1, characterized in that: 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. The grasping angle encoder (5-1) has a threaded hole at the bottom and is fixed to the encoder receiving part with screws. The PU belt is used to transmit the rotation angle of the hand grasping. The lever arm angle encoder (5-2) has a threaded hole at the bottom and is fixed to the encoder receiving part with screws. The PU belt is used to measure the rotation angle of the lever arm. The two are used to collect 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.

6. The force feedback device 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 and storage unit and a control processor. The data acquisition and storage unit is responsible for collecting the angle and position information of the measuring unit, and the control processor processes these data and calculates the feedback force and stiffness of the device.

7. A force feedback method using the force feedback device for assisting a surgical robot gripping operation according to claim 5, characterized in that: The steps include: The force feedback device is powered on, and the grip angle encoder (5-1), lever arm angle encoder (5-2), potentiometer (5-3), linear motor (1-5), ratchet motor (3-2) and its drive circuit, analog-to-electric converter, and microcontroller are operating normally; Select the ratchet engagement state, press the handle (4-2), drive the lever arm (1-1) to rotate, and the pressure is transmitted to the spring baffle (1-2) through the baffle pulley, the left spring and the right spring are deformed and generate reaction force, 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 operation to change the spring position.

8. The force feedback method of the force feedback device for assisting the clamping operation of a surgical robot according to claim 7, characterized in that: Feedback torque and stiffness of the force feedback device Calculated by the following formula: ； ； Where, is the elastic constant of the spring, is the rotation angle of the lever arm measured by the deflection angle encoder, It is the distance between the center of the spring stop and the center of the lever arm's rotation axis.

Images